Class D Audio Amplifier Basics
class d 原理(一)
class d 原理(一)Class D 概述什么是 Class DClass D 是一种用于放大音频信号的功率放大器。
它具有高效、节省能源和低发热等优点，因此在音频应用场景中得到广泛应用。
Class D 的原理1.脉宽调制（PWM）技术：Class D 使用脉宽调制技术将模拟音频信号转换为数字信号。
这通过将音频信号分成许多短时脉冲来实现，其宽度与音频信号的幅度有关。
2.输出滤波：脉宽调制后的数字信号需要经过输出滤波电路来去除高频成分。
输出滤波器使用电感和电容来滤除脉宽调制信号中的高频元素，以得到音频信号的纯净输出。
3.开关管：Class D 使用开关管（通常是 MOSFET）将滤波后的数字信号转换回模拟信号。
开关管的导通和截止由输入信号的 PWM 脉冲控制，从而根据输入信号的幅度调整输出信号的幅度。
Class D 的优点•高功率效率：Class D 的功率效率通常非常高，因为开关管只在导通和截止状态工作，并且能量损失小。
•节能环保：由于高功率效率，Class D 在相同输出功率的情况下消耗的电能较少，有助于节能和减少能源浪费。
•低发热：相比于传统的线性放大器，Class D 发热较少，这是因为开关管处于导通和截止状态而不会持续工作。
•小体积：Class D 的电路结构相对简单，所需元器件较少，因此可以实现较小的物理体积。
Class D 的应用•低音扬声器：Class D 可以提供高功率输出，使其成为低音扬声器的理想放大器。
•汽车音响：由于 Class D 的高效特性，许多汽车音响系统采用 Class D 放大器，以提供强大的声音输出同时保持能耗低。
•蓝牙扬声器：蓝牙扬声器通常需要小体积和长电池寿命，Class D 放大器满足了这些要求。
•无线麦克风系统：Class D 可以提供清晰、高保真的音频输出，因此用于无线麦克风系统可以获得优异的音质表现。
总结Class D 是一种高效、节能、小体积的功率放大器，使用脉宽调制技术将模拟音频信号转换为数字信号，并通过开关管和输出滤波实现音频信号的放大和滤波。
Audio Basics 1
音频基础之声音的特性Presented By: Kane ZhangAudio Basics 1 ‒ Properties of Sound亚太区技术支持Citrix“Go To Training”Kane Zhang Email Address: kzhang@Cell in Hongkong: +852-********Cell in China: +86-156********Skype: biamp.kanezhangBiamp Systems | 9300 SW Gemini Dr. Beaverton, OR 97008 | tel: 800.826.1457 503.641.7287 | fax: 503.626.0281声音是什么？声音的特性什么是dB ？等响曲线 平方反比定律 今天给大家介绍… …,音频系统 室内声学特性 声学增益 声音信号级别 平衡与非平衡连接声音的定义：物理学：▪声波，是由振动物体产生，并在媒介中传播。
声波可以理解为介质偏离平衡态的小扰动的传播。
这个传播过程只是能量的传递过程，而不发生质量的传递。
生物学：▪是指声波作用于听觉器官所引起的一种主观感觉。
小问题：声音在真空里可以传播吗？声波声音的特性：声音物理特性：频率强度声谱（频谱）人耳主观感觉：音调响度音色小问题：音色和音调有什么不同？声音的特性： Harmonics 谐波/泛音 复合音基波一次泛音 二次泛音 三次泛音 四次泛音 中音C = 523 Hz 小常识：泛音是基波频率的整数倍声音的特性： ½ cycle 1 cycle WavelengthAmplitude P r e s s u r e 0+- 速度、周期、波长、频率、振幅、频宽声音的速度与媒介的温度和密度有关空气中的速度= 331.4 + 0.6 x T(ºC) m/s周期（T ）：完成往復運動一次所需的時間。
单位：s 频率（F ）：周期的倒数即f=1/T 单位：Hz波长（λ）：指沿着波的传播方向，在波的图形中相对平衡位置的位移时刻相 同的相邻的两个质点之间的距离。
3瓦D类功放(TA8803)规格书
E f f i c i e n c y (%)Key FeaturesGeneral Description3W Output at 10% THD with a 4Ω Load and 5V Power SupplyFilterless, Low Quiescent Current and Low EMIThe TA8803 is a 3W, class-D audio amplifier with 64-step digital volume control. It offers low THD+N, allowing it to produce high-quality sound reproduction. The new filterless a r chitecture Low THD+Nallows the device to drive the speaker directly, 64-step Digital Volume Control Superior Low Noise Low pop noiseEfficiency up to 90% Short Circuit Protection Thermal ShutdownFew External Components to Save Space and Costwithout needing low-pass output filters , which will save 30% system cost and 75% PCB area.With the same numbers of external components, the efficiency of the TA8803 is much better than class-AB cousins. It can extend the battery life, ideal for portable applications.Pb-Free PackageApplicationsThe TA8803 is available in a SSOP-24 package.LCD Monitors/TV Projectors Notebook Computers Portable SpeakersPortable DVD Players, Game Machines Cellular Phones/Speaker PhonesTypical ApplicationVD DC11μFPVDDC3 10μFC2 1μF100 90 80 70 60 50 7 18 5 2 340 4VDD GND PVDD PGND PGND 21 30SP_L+OUT_L1-OUT_L +OUT_R24 -OUT_RSP_R20 10 0 0 0.5 1 1.5 2 2.5 3IN LC60 .47μF8 17 INL INR TA8803C70.47μFINROutput P ow er(W)10C8 1μFVREFUP 14S1 Radiated EmissionsONMUTEONMUTE6 MUTE DN13S2SHDNSHDN19 SHDNNC N C N CNCPVDDPGND RST15PGND S3FCC Class B Limit9 11 12 16 2022 23C4 1μFPVDDC5 10μFBlock DiagramVDD PGNDDNMUTE SHDN +OUT_R -OUT_RVREFINL+OUT_L-OUT_L PGNDPin Configuration & Marking InformationTop ViewSSOP-24-OUT_L 1 PGND 2 PGND 3 +OUT_L 4 PVDD 5 MUTE 6VDD 7INL 8NC 924 -OUT_R23 PGND22 PGND21 +OUT_R20 PVDD19 SHDN18 GND17 INR16 NCX: Internal CodeY: YearWW: WeekLL: Internal CodeVREF10NC 1115 RST 14 UPNC DNTA8803 XXXYWWLLPin DescriptionsAbsolute Maximum RatingsThese are stress ratings only and functional operation is not implied.Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground.Supply Voltage at no Input Signal...................6.0V Maximum Junction Temperature..................150°CInput Voltage.............................-0.3V to VDD +0.3V StorageTemperature.....................-65°C to 150°C Soldering Temperature.......................300°C, 5secRecommended Operating ConditionsSupply voltage Range........................2.2V to 5.5V Ambient Temperature Range...........-40°C to 85°CJunction Temperature Range.........-40°C to 125°CThermal InformationParameter Symbol Package Maximum Unit Thermal Resis tance (Junction to Ambient)θJA SSOP-2496°C/WElectrical CharacteristicVDD =5V, Gain = 18dB, RL=8Ω,TA=25°C，unless otherwise noted.Typical Operating Characteristics (TA=25°C)1. THD+N vs Output Power2. THD+N vs Output PowerR=8Ω, Gain = 18dB%0.% 0.50.0.0.00.00.010m20m50m100m200m500m12410m20m50m100m 200m500m 124W W3. THD+N vs Output PowerVDD =5V, RL=4Ω, Gain = 18dB4. THD+N vs Output PowerV=5V, R=8Ω, Gain = 18dB0 0 0W20m50m 100m 200m 500m 1 2 4W5. THD+N vs FrequencyVDD=5V, RL=4Ω, Gain = 18dB16. THD+N vs FrequencyV=5V, R=8Ω, Gain = 18dB00 00H z 0H zHzTypical Operating Characteristics (continued)7. THD+N vs. FrequencyPo=0.8W,R =4Ω,Gain=18dB18. THD+N vs. FrequencyPo=0.1W,R L =8Ω,Gain=18dB0020501002005001k2k5k10kH z20k0H z++9. Frequency responseV DD =5V, Gain =18dB10. Power Supply Ripple Rejection VS FrequencyV DD =5V with 200mVpp Ripple++d +--d-+-20 50 100 200 500 1k 2k 5k 10k Hz20k-H zd BV ------11. FFT of Noise OutputV =5V, Gain = 18dB-dB12.Channel SeparationV =5V, R =4Ω, P =1.0W,Gain = 18dB H zH zO u t p u t P o w e r (W )O u t p u t P o w e r (W )Typical Operating Characteristics (continued)43.53 2.521.510.50 13. Output Power vs Power SupplyR L =4Ω10%ΤΗD1%ΤΗD2 3 4 5 6Supply Voltage (V)2.52 1.51 0.50 14. Output Power vs Power SupplyR L =8Ω10%ΤΗD1%ΤΗD2 3 4 5 6Supply V o ltage (V )Gain Setting (VDD=5V)Step Gain (dB) Step Gain (dB)Step Gain (dB)Step Gain (dB)1 -75.0 17 4.83311.249 17.62 -39.7 18 5.13411.650 18.03 -34.0 19 5.53512.051 18.44 -28.2 20 5.93612.352 18.85 -22.4 21 6.33712.753 19.26 -16.5 22 6.73813.254 19.67 -10.5 23 7.13913.655 20.08 -8.0 24 7.54014.056 20.49 -5.5 25 7.94114.457 20.910 -2.9 26 8.34214.858 21.311 -0.4 27 8.74315.259 21.712 1.1 28 9.14415.660 22.113 2.6* 29 9.64516.061 22.514 3.6 30 10.04616.462 22.915 4.0 31 10.44716.863 23.4164.43210.74817.26423.8*Power on gain or gain after reset.Note: Gain could have 1dB deviation device to device.Application Notice1． When TA8803 works without filter, we must connect the speaker before turn on. Else, it will be easy to damage the chip.2． When TA8803 works without filter, it will be best that adding a ferrite chip bead at the outgoing line of speaker in order to suppress possible electromagnetic interference .3． The absolute maximum rating of operation voltage is 6.0V. While using 6V power regulator, even the chip can deliver 4W sine wave with a 4 Ohm speaker, it is not recommended for long term using due to the heat dissipation. But if the input signal is a music signal, then it can work in long term since the average power output is much less than 4W. When using dry battery cell,we should notice that if the battery cell is 4 new dry batteries or alkaline batteries, even the voltage will be over 6V, it still can work safety. Since the output voltage of the 4 pack of new dry batteries will be reduced very quickly after turn on due to the internal resistance of the battery. There is no dangerous of damaging the chip when playing music or speech, even use 4 new dry batteries. To reduce the effect of the increasing of internal resistance of battery after long term discharging, it is recommended to connect a 1000uF electrolytic capacitor between the power supply and the ground.4． Because digital volume control has big gain, we can not make input signal too high to cause the clipping of the output signal when increase volume, also it may damage the chip.Test Setup for Performance TestingTA8803 Demo Board1. The AP AUX-0025 low pass filter is necessary for every class-D amplifier measurementdone by AP analyzer.2. Two 22μH inductors are used in series with load resistor to emulate the small speaker forefficiency and quiescent current measurement.13Application InformationMaximum GainAs shown in block diagram(page 2),the TA8803 has two internal amplifiers stage. The first stage's gain is externally con figurable, while the second stage's is internally fixed in a fixed-gain, inverting configuration. The closed-loop gain of the first stage is set by selecting the ratio of R f to R i while the second stage's gain is fixed at 2x. Consequently, the differential gain for the IC isA VD =20*log [2*(R f /R i )]There are 64 discrete gain settings ranging from +24dB maximum to -75dB minimum. Upon device power on or applied a logic low to the RST pin, the amplifier's gain is set to a default value of -4.5dB. However, when coming out of mute mode, the TA8803 will revert back to its previous gain setting. Volume levels for each step vary and are specified in Gain Setting table on page 7.If both the UP and DN pins are held high, no volume change will occur. Trigger points for the UP and DN pins are at 70% of V DD minimum for a The TA8803 sets maximum R f =218k Ω and logic high, and 20% of V DD maximum for a logic minimum R i =27k Ω, thus the maximum closed- low. It is recommended, however, to toggle UP gain is 24dB.Digital Volume Control (DVC)The TA8803 features a digital volume control which consists of the UP, DN and RST pins. An a n d D N b e t w e e n V D D performance.a n d G N D f o rb e s t internal clock is used where the clock frequency value is determined from the following formula:f CLK = f OSC / 2The oscillator frequency f OSC Figure 1.Timming DiagramMute Operationvalue is 250kHz typical,with ±20% tolerance.The DVC’s clock The MUTE pin is an input for controlling the frequency is 33Hz (cycle time 30ms) typical.Volume changes are then effected by toggling either the UP or DN pins with a logic low. After a period of 3.5 clocks pulses with either the UP or DN pins held low, the volume will change to the next specified step, either UP or DN, and followed by a short delay. This delay decreases the longer the line is held low, eventually reaching a delay of zero. The delay allows the user to pull the UP or DN terminal low once for one volume change, or hold down to ramp several volume changes. The delay is optimally configured for push button volume control.If either the UP or DN pin remains low after the first volume transition the volume will change again, but this time after 9.5 clock pulses. The followed transition occurs at 2 clock pulses for each volume transition. This is intended to provide the user with a volume control that pauses briefly after initial application, and then slowly increases the rate of volume change as it is continuously applied. This cycle is shown in the timing diagram shown in figure 1.output state of the TA8803 . A logic low on this pin disables the outputs, and a logic high on this pin enables the outputs. This pin may be used as a quick disable or enable of the outputs without a volume fade. Quiescent current is listed in the electrical characteristic table. The MUTE pin can be left floating due to the pull-up internal.Shutdown operationIn order to reduce power consumption while not in use, the TA8803 contains shutdown circuitry that is used to turn off the amplifier's bias circuitry. T his shutdown feature t urns the amplifier off when logic low is placed on the SHDN pin. By switching the SHDN pin connected to GND, the TA8803 supply current draw will be minimized in idle mode. The SHDN pin cannot be left floating due to the pull-down internal.Power supply decouplingThe TA8803 is a high performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output THD and PSRR are as low as possible. Power supply decoupling is affecting low frequency response. Optimum decoupling is achieved by using two capacitors of different types that target different types of noise on the power supply leads. For higher frequency transients, spikes, or digitalhash on the line, a good low equivalent-series- resistance (ESR) ceramic capacitor, typically 1.0μF, placed as close as possible to the device function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This noise is from the internal analog reference to the amplifier , which appears as degraded PSRR and THD+N.Bypass capacitor (C BYP ) values of 0.47μF to 1.0μF ceramic is recommended for the best THD and noise performance. Increasing the bypass capacitor reduces clicking and popping noise from power on/off and entering and leaving shutdown.Under Voltage Lock-out (UVLO)V DD terminal works best. For filtering lower- frequency noise signals, a larger capacitor of The TA8803 incorporates circuitry designed to 10μF (ceramic) or greater placed near the audio detect when the supply voltage is low. When the power amplifier is recommended.Input Capacitor (C i )Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized capacitor is needed to couple in low frequencies without severe attenu ation. But in many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 100Hz to 150Hz. Thus, using a large input capacitor may not increase actual system perfor mance. In this case, input capacitor (C i ) and input resistance (R i ) of the amplifier form a high-pass filter with the corner frequency determined equation below, supply voltage drops to 1.85V or below, the TA8803 outputs are disable, and the device comes out of this state and starts to normal functional when the supply voltage increases.Short Circuit Protection (SCP)The TA8803 has short c ircuit protectioncircuitry on the outputs that prevents damage to the device during output-to-output and output- to-GND short. When a short circuit is detected on the outputs, the outputs are disable immediately. If the short was removed, the device activates again.Over Temperature Protectionf C =1 2πR i C iIn addition to system cost and size, click and pop perfor mance is affected by the size of the input coupling capacitor, C i . A larger input coupling capacitor requires more charge to reach itsThermal protection on the TA8803 prevents damage to the device when the internal die temperature exceeds 150°C. There is a 15 degree tolerance on this trip point from device to device. Once the die temperature exceeds the thermal s e t point, t h e device outputs a r e fault. The thermal quiescent DC voltage (nominally 1/2 V DD ). This charge comes from the internal circuit via the feedback and is apt to create pops upon device enable. Thus, by minimizing the capacitor size based on necessary low frequency response, turn-on pops can be minimized.Analog Reference Bypass Capacitor (C BYP )The Analog Reference Bypass Capacitor (C BYP ) is the most critical capacitor and serves several important functions. During start-up or recovery from shutdown mode, C BYP determines the rate at which t h e amplifier s t arts up. The s e conddisabled. This is not a latched fault is cleared once the temperature of the die is reduced by 60°C. This large hysteresis will prevent motor boating sound well and the device begins normal operation at this point with no external system interaction.How t o Reduce EMI (Electro Magnetic Interference)A simple solution is to put an additional capacitor 1000uF at power supply terminal for power line coupling if the traces from a mplifier to speakers are short (<20cm).05/201011Most applications require a ferrite bead filter which shows at Figure 3. The ferrite filter reduces EMI around 1 MHz and higher. When selecting a ferrite bead, choose one with high i m p e da nc e a t h i g h f r e q u en c ie s , b u t low impedance at low frequencies.channel specific. A two channels amplifier has t w o m u t u a l l y e x c l u s i v e c h a n n e l s a n d consequently must have two mutually exclusive output noise ground traces. The layout of the TA8803 offers separate PGND connections for each channel and in some cases each side of the bridge. Output noise grounds must tie to system ground at the power in exclusively. Signal currents for the inputs, reference, etc need to bethe signal components and the GND pin. GND then ties to system ground.Power Supply LineAs same to the ground, VDD and each channel PVDD need to be separated and tied together at Figure 3: Ferrite Bead Filter to reduce EMIPCB Layout GuidelinesGroundingA t t h i s s t a g e i t i s p a r a m o u n t t h a t w e acknowledge the need for separate grounds. Noise currents in the output power stage need to be returned to output noise ground and nowhere else. Were these currents to circulate elsewhere, they may get into the power supply, the signal ground, etc, worse yet, they may form a loop and radiate noise. Any of these instances results in degraded amplifier performance. The logical returns for the output noise currents associated with Class D switching are the respective PGND pins for each channel. The switch state diagram illustrates that PGND isinstrumental in nearly every switch state. This is the perfect point to which the output noise ground trace should return. Also note that output noise ground isthe system power supply. Recommend that all the trace could be routed as short and thick as possible. For the power line layout, just imagine water stream, any barricade placed in the trace (shows in figure 4) could result in the bad performance of the amplifier.Figure 4Components PlacementThe power supply decoupling capacitors need to be placed as close to VDD and PVDD pins as possible. The inputs need to be routed away from the noisy trace. The VREF bypass capacitor also needs to be close to the pin of IC very much.PCB Top LayerPCB Bottom LayerFigure 5: Layout ExampleSiXplore Microelectronics ,Inc05/201012Ordering InformationTA8803Shipping Package Number of Pins Package TypePart NumberMarking Package Type Shipping PackageTA8803 NHRTA8803 XXXYWWLLSSOP-242,500 Units /Tape & ReelSiXplore Microelectronics ,IncOutline DimensionSSOP-24SiXplore Microelectronics,Inc05/201013。
Audio_Basics
Input Triangular
PWM
TI Confidential – NDA Restrictions
Modulation Modes
PVDD GVDD
A
LOAD
C
GVDD
BD Mode
+ AP AM
GVDD
B
D
GVDD
AD Mode
+ AP, BM BP, AM -
+ -
BP BM
BD MODE AD On - BC Off AC On - BD Off BC On - AD Off BD On - AC Off
– At lower level (<1 watts, depends on system), the distortion is dominated by noise. – An efficient speaker driver can reproduce the noise at an audible level with the amplifier. – Turn on input signal – Measure with AES-17 LPF
Audio Amplifier – Class AB
Class AB amplifiers
Class A – high idle loss (inefficient) Class B – high cross over distortion Class AB – the best of both classes above: efficient if bias current setting is low enough; low crossover distortion if bias current setting is high enough. However class AB amplifiers are still not very efficient ~ theoretically 78.5%.
Class-D功放详解
图2 原始信号和PWM输出信号以及经过低 通滤波器以后的信号频谱
雖然Class-D Amplifier 的工 作原理都是依靠PWM調製技術， 但在具體採樣方式和時序上，各 個廠商之間卻各不相同，以TI & PAM為例：
右圖為TI廠商型號：TPA3110D2 全橋輸出的波形。黃色曲綫和藍 色曲綫分別為負載兩端對地的波 形，紅色曲綫為黃色曲綫與藍色 曲綫做減法運算得到的波形即負 載的輸出波形。
最简单的PWM就是一个比较器，它的一端输入原始要放大的信号，另一端就 输入一个高频三角波。在这个比较器的输出就是一个脉宽被调制的矩形波。 这个矩形波就直接加到一对互补晶体管进行放大 。
NOTE：采用负反馈回路可降低失真，最简单的方式：直接从输出端经过RF反馈到输入端。
三角波可以采用如右图的方 式来产生。比较器输出的电 压为＋V1和－V1。当输出电 压为－V1时，三角波以 m=V1/R6C4的斜率增长。假定 三角波的峰值幅度为从＋VTP 到－VTP。再假定三角波的周 期为T＝1/fT。那么较器在 其非倒相输入端的电压达到0 时，切换其状态。这发生于 V1/R8=VTP/R7。所以，三角 波的频率就等于
• Amplifiers that provide features like • Volume control • Speaker and headphone drive • I2C interface • Bass boost • Small package options
图5. D类放大器的结构图
OUTLINE
Class-D Audio Amplifier 的工作原理和结构特点
The Principle Of Class-D Amplifier
Class-D功放详解
• 图8.半桥式和全桥式结构比较
Compare Class-D Amplifier With Class AB
Audio amplifier basic configuration
Class-AB vs. Class-D
Class-AB amplifiers use the same push-pull architecture as class-B, but active devices are biased on with a small quiescent current when Vin = 0.
• NOTE：为了不失真地放大最高频率分量为 20KHz的音频信号，三角波的重复频率最好在十倍 音频的最高频率分量，也就是200KHz以上
右圖表明了一个1KHz的正 弦波音频信号，经过三角波 采样后的输出频谱，其中包 含有很多高频分量。在 PWM的输出后面加上一个 低通滤波器，就可以滤去矩 形波的高频分量。
advantage: excellent linearity
disadvantage: poor efficiency
Q4
Q3
Q5 Vin
PVDD
Q1
C1 Q2
Rload
Class-D amplifiers modulates the audio signal in to a high frequency PWM signal that drives the speaker(s).
fT=R8/4R6R7C4， VTP＝V1R7/R8
图6. 三角波发生器
NOTE：积分电路的输出电压与输入 电压的积分成反比关系，所以阶跃信 号输入积分电路后会输出一个比例函 数的波形。
Class-D功放详解
Class D Vin
AP
LPF
AP
圖12 Test of Class-D and ClassAB
D类放大器的失真
Major Cause of Imperfection
Feedback Integrator
Switch nonidealities
Finite Ron Body diode Recovery (EMI)
最简单的PWM就是一个比较器，它的一端输入原始要放大的信号，另一端 就输入一个高频三角波。在这个比较器的输出就是一个脉宽被调制的矩形 波。这个矩形波就直接加到一对互补晶体管进行放大 。
NOTE：采用负反馈回路可降低失真，最简单的方式：直接从输出端经过RF反馈到输入端。
三角波可以采用如右图的方
式来产生。比较器输出的电 压为＋V1和－V1。当输出电 压为－V1时，三角波以 m=V1/R6C4的斜率增长。假 定三角波的峰值幅度为从＋ VTP到－VTP。再假定三角波 的周期为T＝1/fT。那么2VTP ＝mT/2=V1/2fTR6C4。比较 器在其非倒相输入端的电压 达到0时，切换其状态。这发 生于V1/R8=VTP/R7。所以， 三角波的频率就等于
NOTE：死区时间会严重影响失真，时长 几十纳秒就可能导致THD达到1%以上。
图13 THD and Dead time
Power Supply Pumping
另一个导致THD增大的原因是总 线充电，可以在半桥拓扑向负载提 供低频的输出信号时观察到如右。 这主要是由于D类Amplifier的增益 与Vbus直接成比例关系，Vbus波 动造成输出失真。由于D类 Amplifier的开关时双向的，当大 量LPF电感储存的能量回流至电源 时，电源无法吸收从而导致Vbus 上升产生波动。
audio amplifier用法
audio amplifier用法音频放大器（Audio Amplifier）是一种用于放大电子信号的设备，它用于将低电平的音频信号放大到足够大的电平，以便驱动扬声器或其他听觉设备。
这篇文章将一步一步地回答关于音频放大器的使用方式以及相关话题。
第一部分：什么是音频放大器？在介绍音频放大器的用法之前，我们先来了解一下音频放大器的基本工作原理。
音频放大器的任务是将音频信号经过放大后输出到扬声器或耳机。
它主要由前级放大器、功率放大器和输出级组成。
前级放大器用于将微弱的音频信号放大到合适的电平，然后传递给功率放大器。
功率放大器负责将前级放大器输出的信号进一步放大，以便驱动扬声器。
最后，输出级将放大的音频信号传递到扬声器或耳机，使人们能够听到清晰、高保真的音频。
第二部分：音频放大器的应用领域音频放大器在许多领域都有广泛的应用。
首先是家庭音响系统，包括立体声系统和家庭影院系统。
音频放大器使得家庭用户能够以高质量享受音乐和电影的音频效果。
此外，音频放大器也广泛应用于专业音频设备领域，如演播室、音乐录制工作室和现场音乐表演等。
在这些场合中，音频放大器的质量和性能对于获得高品质的音频输出至关重要。
第三部分：音频放大器的选择和连接在选择音频放大器时，有几个关键因素需要考虑。
首先是功率输出。
根据需要驱动的扬声器类型和大小，选择合适的功率输出。
其次是音频放大器的频率响应范围。
一个好的音频放大器应该能够在全频带内提供均衡、清晰的声音。
此外，输入和输出接口的兼容性也是一个重要因素，以确保音频信号能够正确地连接到音频放大器。
连接音频放大器的方法取决于具体的设备。
如果是家庭音响系统，通常会使用RCA线缆将音频输出设备（如CD播放器）连接到音频放大器的输入接口上。
同时，音频放大器的输出接口将连接到扬声器或其他听觉设备上。
在专业音频设备领域，常见的连接方式包括平衡（XLR）和非平衡（RCA）接口。
这些接口可以确保音频信号的稳定传输和低噪声。
ClassD功放详解
Others:
THD+N (ex.0.01%, 80dBFs, A weighting Filter) Cross-Talk For Stereo
NOTE：死区时间会严重影响失真，时长 几十纳秒就可能导致THD达到1%以上。
图13 THD and Dead time
Power Supply Pumping
另一个导致THD增大的原因是总 线充电，可以在半桥拓扑向负载提 供低频的输出信号时观察到如右。 这主要是由于D类Amplifier的增益 与Vbus直接成比例关系，Vbus波 动造成输出失真。由于D类 Amplifier的开关时双向的，当大 量LPF电感储存的能量回流至电源 时，电源无法吸收从而导致Vbus 上升产生波动。
图7. 全橋式桥式输出的D类放大器
• 图8.半桥式和全桥式结构比较
Compare Class-D Amplifier With Class AB
Audio amplifier basic configuration
Class-AB vs. Class-D
Class-AB amplifiers use the same push-pull architecture as class-B, but active devices are biased on with a small quiescent current when Vin = 0.
完全工作于开关状态，損耗很小
只要考虑在导通时的损耗。假定
负载电阻为RL，晶体管导通时的 内阻为Ron，則效率為：
•
E＝RL/(2Ron + RL)
• 除外，偏置电流、输入电容充 电、和切换电流都会降低效率，
右图为D类放大器和AB类放大器 在不同的输出功率时的效率 。
常用功放IC大全
397 TDA7240AH 20WBRIDGE AMPLIFIER FOR CAR RADIO
STMicroelectronics
396 TDA7240AV 20WBRIDGE AMPLIFIER FOR CAR RADIO
33 TDA8925ST Power stage 2 x 15 to 25Wclass-D audio amplifier
32 TDA8926 Power stage 2 x 50 W class-D audio amplifier
31 TDA8926J Power stage 2 x 50 W class-D audio amplifier
10．前置放大集成电路 前置放大集成电路属于低噪声、低失真、高增益、宽频带的运算放大器,有较高的输入阻抗和良好的线性.
常用的前置放大集成电路有NE5532、NE5534、NE5535、OP248、TL074、TL082、TL084、LM324、LM381、LM382、LM833、LM837等型号.
秀涛电子 更多资料请查看官方网站
TDA8920 2 x 50 W class-D power amplifier
NXP Semiconductors
48 TDA8920B 2 X 100 W class-D power amplifier
17 TDA8941P 1.5 W mono Bridge Tied Load BTL audio amplifier
16 TDA8942 2 x 1.5 W stereo Bridge Tied Load BTL audio amplifier
音频功率放大器测试(中英双语)
Review of Audio Terms 音频项目的回顾 First, let’s review a few audio terms首先,让我们回顾一 些音频测量项目: THD+N—Total Harmonic Distortion plus Noise. An excellent figure of merit for an audio device.总谐波失 真加噪声. 一个音频设备优良的质量因数. IMD—Intermodulation Distortion. 互调失真 SNR—Signal to Noise Ratio. 信噪比 LCR Filter—Inductor(L)-Capacitor(C)-Resistor(R) filter network. 电感-电容-电阻滤波网络 FFT—Fast Fourier Transform. Mathematics that can provide detailed analysis of waves, including time domain and frequency domain displays. 快速傅立叶变 换. 提供波形详细分析的数学方法,包含时域和频域的显示.
Analog vs. Digital Filter Implementation 模拟滤波器与数字滤波器的比较 Audio Precision implements the AES17 filter in hardware for 2700 Series instruments (left), and provides superior brick-wall DSP filters in the APx family of analyzers (right). AP在2700系列中使用AES17硬件滤波器(左图),而在APx系 列分析仪中使用优良的Brick-wall DSP数字滤波器(右图)
A、B、AB、D类音频功率放大器
D类音频功率放大器（Class D Audio Power Amplifier）近二十年来电子学课本上所讨论的放大器偏压(Bias)分类不外乎A类、B类、C类等放大电路，而讨论音频功率放大器仅强调A类、B类、AB类而却把D类放大器给忘掉了，事实上D类放大器早在1958年已被提出(注一)，甚至还有E 类、F类、G类、H类及S类等(注二)，只是这些类型的电路与D类很接近，运用机会低，所以也就很少被提及。
音频功率放大器最大目的在提供喇叭得到最大功率输出，而卫衍生与电源所供给功率不对等的关系，即所谓功率放大器的效率(输出功率与输入功率之比)如表一所示:偏压分类A类AB类B类D类理想效率25% 介于A与B类之间78.5% 100%表一各類功率放大器的效率比随着轻、薄、短、小手持电子装置的发展，诸如手机、MP3、PDA、IPOD 及LCD TV…数位家庭等，寻求一个省电的高效率音频功率放大器是必然的。
因此最近几年音频功率放大器由AB类功率放大器转以D类功率放大器为主流。
如图1所示(注三)，在实际应用上D类放大效率可达90%以上远超过效率50%的AB类放大。
所以D类放大的晶体管散热可大大的缩小，很适合应用于小型化的电子产品。
圖 1 D類及AB 類效率比較A类放大器(又称甲类放大器)的特点是不论是否输入信号，其输出电路恒有电流流通，而且这种放大器通常是在特性曲线的线性范围内操作，如图2所示，以求放大后的信号不失真。
所以它的优点，是失真度小，信号越小传真度越高，最大的缺点是“功率效益”（Power Efficiency）低，最大只有25%，不输入信号时丝毫不降低消耗功率，极不适合做功率放大。
但因其高传真度，部分高级音响器材仍采用A类放大器。
图1图2(a)、(b)皆属A类放大器，设计时让V CE=1/2V CC，以求最大不失真范围。
注意到V i 不输入时仍有0.5V CC/R L的电流流过晶体管，所以晶体管需要良好的散热环境。
Class ABCD Amp音频放大器
一、音频放大器分类Audio播放音频信号包含两个主要过程：1、数字语音数据到模拟语音信号的变换（利用高精度数模转换器DAC）实现；2利用模拟功率放大器进行模拟信号放大，如A类、B 类和AB类放大器。
从1980年代早期，许多研究者致力于开发不同类型的数字放大器，这种放大器直接从digital data实现功率放大而不需要进行模拟转换，这样的放大器通常称作数字功率放大器或者D类放大器。
•A类放大器特点：•放大器的工作点Q设定在负载线的中点附近,晶体管在输入信号的整个周期内均导通。
•放大器可单管工作，也可以推挽工作。
•工作在特性曲线的线性范围内，瞬态失真和交替失真较小效率低，功率的理论最大值仅有25％•B类放大器特点：•放大器的静态点在(VCC、0)处，即截止点处，当没有信号输入时，输出端几乎不消耗•功率。
在Vi的正半周期内，Q1导通Q2截止，输出端正半周正弦波；同理，当Vi 为负半波正弦波，Q2导通Q1截止，输出端负半周正弦波，所以必须用两管推挽工作。
•因放大器有一段工作在非线性区域内，交越失真较大•AB类放大器特点：•晶体管的导通时间稍大于半周期，必须用两管推挽工作。
可以避免交越失真。
效率较高，晶体管功耗较小•D类放大器特点：将输入模拟音频信号变换成PWM(脉冲宽度调制)或PDM(脉冲密度调制)的脉冲信号，然后用PWM或PDM的脉冲信号去控制大功率开关器件通/断音频功率放大器，也称为开关放大器。
放大器由输入信号处理电路、开关信号形成电路、大功率开关电路(半桥式和全桥式)和低通滤波器(LC)等四部分组成.PWM技术是用模拟信号的幅度来调制一系列矩形脉冲的宽度，这种脉冲是用一个等幅度的三角波来对音频信号进行采样来实现的。
经过采样后，模拟信号就被转换为脉冲信号的宽度信息中去了。
优点：原来的模拟信号包含在脉冲宽度中，则放大时晶体管的非线性引起的幅度失真不会对信号有影响；晶体管可以工作在开关状态，在此状态的晶体管的效率很高，可以提供更高的功率。
D类音频放大器英文原文
英文翻译Class D Audio Amplifiers:What, Why, and HowClass D amplifiers, first proposed in 1958, have become increasingly popular in recent years. What are Class D amplifiers? How do they compare with other kinds of amplifiers? Why is Class D of interest for audio? What is needed to make a “good”audio Class D amplifier? What are the features of ADI’s Class D amplifier products? Find the answers to all these questions in the following pages.Audio Amplifier BackgroundThe goal of audio amplifiers is to reproduce input audio signals at sound-producing output elements, with desired volume and power levels—faithfully, efficiently, and at low distortion. Audio frequencies range from about 20 Hz to 20 kHz, so the amplifier must have good frequency response over this range (less when driving a band-limited speaker, such as a woofer or a tweeter). Power capabilities vary widely depending on the application, from mill watts in headphones, to a few watts in TV or PC audio, to tens of watts for “mini”home stereos and automotive audio, to hundreds of watts and beyond for more powerful home and commercial sound systems—and to fill theaters or auditoriums with sound.A straightforward analog implementation of an audio amplifier uses transistors in linear mode to create an output voltage that is a scaled copy of the input voltage. The forward voltage gain is usually high (at least 40 dB). If the forward gain is part of a feedback loop, the overall loop gain will also be high. Feedback is often used because high loop gain improves performance—suppressing distortion caused by nonlinearities in the forward path and reducing power supply noise by increasing the power-supply rejection (PSR).The Class D Amplifier AdvantageIn a conventional transistor amplifier, the output stage contains transistors that supply the instantaneous continuous output current. The many possible implementations for audio systems include Classes A, AB, and B. Compared with Class D designs, the output-stage power dissipation is large in even the most efficient linear output stages. This difference gives Class D significant advantages in many applications because the lower power dissipation produces less heat, savescircuit board space and cost, and extends battery life in portable systems.Linear Amplifiers, Class D Amplifiers, and Power DissipationLinear-amplifier output stages are directly connected to the speaker (in some cases via capacitors). If bipolar junction transistors (BJTs) are used in the output stage, they generally operate in the linear mode, with large collector-emitter voltages. The output stage could also be implemented with MOS transistors, as shown in Figure 1.Figure 1. CMOS linear output stage.Power is dissipated in all linear output stages, because the process of generating VOUT unavoidably causes nonzero IDS and VDS in at least one output transistor. The amount of power dissipation strongly depends on the method used to bias the output transistors. The Class A topology uses one of the transistors as a dc current source, capable of supplying the maximum audio current required by the speaker. Good sound quality is possible with the Class A output stage, but power dissipation is excessive because a large dc bias current usually flows in the output-stage transistors (where we do not want it), without being delivered to the speaker (where we do want it).The Class B topology eliminates the dc bias current and dissipates significantly less power. Its output transistors are individually controlled in a push-pull manner, allowing the MH device to supply positive currents to the speaker, and ML to sink negative currents. This reduces output stage power dissipation, with only signal current conducted through the transistors. The Class B circuit has inferior sound quality, however, due to nonlinear behavior (crossover distortion) when the output current passes through 0 and the transistors are changing between the on and off conditions. Class AB, a hybrid compromise of Classes A and B, uses some dc bias current, but much less than a pure Class A design. The small dc bias current is sufficient to prevent crossover distortion, enabling good sound quality. Power dissipation, although between Class A and Class B limits, is typically closer to Class B. Some control, similar to that of the Class B circuit, is needed to allow the Class ABcircuit to supply or sink large output currents.Unfortunately, even a well-designed class AB amplifier has significant power dissipation, because its midrange output voltages are generally far from either the positive or negative supply rails. The large drain-source voltage drops thus produce significant IDS 3 VDS instantaneous power dissipation. Thanks to a different topology (Figure 2), the Class D amplifier dissipates much less power than any of the above. Its output stage switches between the positive and negative power supplies so as to produce a train of voltage pulses. This waveform is benign for power dissipation, because the output transistors have zero current when not switching, and have low VDS when they are conducting current, thus giving smaller IDS 3 VDS.Figure 2. Class D open-loop-amplifier block diagram.Since most audio signals are not pulse trains, a modulator must be included to convert the audio input into pulses. The frequency content of the pulses includes both the desired audio signal and significant high-frequency energy related to the modulation process. A low-pass filter is often inserted between the output stage and the speaker to minimize electromagnetic interference (EMI) and avoid driving the speaker with too much high frequency energy.The filter (Figure 3) needs to be lossless (or nearly so) in order to retain the power-dissipation advantage of the switching output stage. The filter normally uses capacitors and inductors, with the only intentionally dissipative element being the speaker.Figure 3. Differential switching output stage and LC.Low-pass filter.Figure 4 compares ideal output-stage power dissipation (PDISS) for Class A and Class B amplifiers with measured dissipation for the AD1994 Class D amplifier,plotted against power delivered to the speaker (PLOAD), given an audio-frequency sine wave signal. The power numbers are normalized to the power level, PLOAD max, at which the sine is clipped enough to cause 10% total harmonic distortion (THD). The vertical line indicates the PLOAD at which clipping begins.Significant differences in power dissipation are visible for a wide range of loads, especially at high and moderate values. At the onset of clipping, dissipation in the Class D output stage is about 2.5 times less than Class B, and 27 times less than Class A. Note that more power is consumed in the Class A output stage than is delivered to the speaker—a consequence of using the large dc bias current. Output-stage power efficiency, Eff, is defined asAt the onset of clipping, Eff = 25% for the Class A amplifier, 78.5% for the Class B amplifier, and 90% for the Class D amplifier (see Figure 5). These best-case values for Class A and Class B are the ones often cited in textbooks.Figure 5. Power efficiency of Class A, Class B, and Class D output stages.The differences in power dissipation and efficiency widen at moderate power levels. This is important for audio, because long-term average levels for loud music are much lower (by factors of five to 20, depending on the type of music) than the instantaneous peak levels, which approach PLOAD max. Thus, for audio amplifiers, [PLOAD = 0.1 3 PLOAD max] is a reasonable average power level at which to evaluate PDISS. At this level, the Class D output-stage Dissipation is nine times less than Class B, and 107 times less than Class A.For an audio amplifier with 10-W PLOAD max, an average PLOAD of 1 W can be considered a realistic listening level. Under this condition, 282 mW is dissipated inside the Class D output stage, vs.2.53 W for Class B and 30.2 W for Class A. In this case, the Class D efficiency is reduced to 78%—from 90% at higher power. But even 78% is much better than the Class B and Class A efficiencies—28% and 3%, respectively.Figure 4. Power dissipation in Class A, Class B, and Class D output stages.These differences have important consequences for system design. For power levels above 1W, the excessive dissipation of linear output stages requires significant cooling measures to avoid unacceptable heating—typically by using large slabs of metal as heat sinks, or fans to blow air over the amplifier. If the amplifier is implemented as an integrated circuit, a bulky and expensive thermally enhanced package may be needed to facilitate heat transfer. These considerations are onerous in consumer products such as flat-screen TVs, where space is at a premium—or automotive audio, where the trend is toward cramming higher channel counts into a fixed space.For power levels below 1 W, wasted power can be more of a difficulty than heat generation. If powered from a battery, a linear output stage would drain battery charge faster than a Class D design. In the above example, the Class D output stage consumes 2.8 times less supply current than Class B and 23.6 times less than Class A —resulting in a big difference in the life of batteries used in products like cell phones, PDAs, and MP3 players.For simplicity, the analysis thus far has focused exclusively on the amplifier output stages. However, when all sources of power dissipation in the amplifier system are considered, linear amplifiers can compare more favorably to Class D amplifiers at low output-power levels. The reason is that the power needed to generate and modulate the switching waveform can be significant at low levels. Thus, the system-wide quiescent dissipation of well-designed low-to-moderate-power Class ABamplifiers can make them competitive with Class D amplifiers. Class D power dissipation is unquestionably superior for the higher output power ranges, though Class D Amplifier Terminology, and Differential vs. Single-Ended Versions Figure 3 shows a differential implementation of the output transistors and LC filter in a Class D amplifier. This H-bridge has two half-bridge switching circuits that supply pulses of opposite polarity to the filter, which comprises two inductors, two capacitors, and the speaker. Each half-bridge contains two output transistors—a high-side transistor (MH) connected to the positive power supply, and a low-side transistor (ML) connected to the negative supply. The diagrams here show high-side pMOS transistors. High-side nMOS transistors are often used to reduce size and capacitance, but special gate-drive techniques are required to control them (Further Reading 1).Full H-bridge circuits generally run from a single supply (VDD), with ground used for the negative supply terminal (VSS). For a given VDD and VSS, the differential nature of the bridge means that it can deliver twice the output signal and four times the output power of single-ended implementations. Half-bridge circuits can be powered from bipolar power supplies or a single supply, but the single-supply version imposes a potentially harmful dc bias voltage, VDD/2, across the speaker, unless a blocking capacitor is added.The power supply voltage buses of half-bridge circuits can be“pumped”beyond their nominal values by large inductor currents from the LC filter. The dV/dt of the pumping transient can be limited by adding large decoupling capacitors between VDD and VSS. Full-bridge circuits do not suffer from bus pumping, because inductor current flowing into one of the half-bridges flows out of the other one, creating a local current loop that minimally disturbs the power supplies.Factors in Audio Class D Amplifier DesignThe lower power dissipation provides a strong motivation to use Class D for audio applications, but there are important challenges for the designer. These include: •Choice of output transistor size•Output-stage protection•Sound quality•Modulation technique•EMI•LC filter design•System costChoice of Output Transistor SizeThe output transistor size is chosen to optimize power dissipation over a wide range of signal conditions. Ensuring that VDS stays small when conducting large IDS requires the on resistance (RON) of the output transistors to be small (typically 0.1V to 0.2V). But this requires large transistors with significant gate capacitance (CG). The gate-drive circuitry that switches the capacitance consumes power—CV 2f, where C is the capacitance, V is the voltage change during charging, and f is the switching frequency. This “switching loss”becomes excessive if the capacitance orfrequency is too high, so practical upper limits exist. The choice of transistor size is therefore a trade-off between minimizing IDS 3 VDS losses during conduction vs. minimizing switching losses. Conductive losses will dominate power dissipation and efficiency at high output power levels, while dissipation is dominated by switching losses at low output levels. Power transistor manufacturers try to minimize the RON 3 CG product of their devices to reduce overall power dissipation in switching applications, and to provide flexibility in the choice of switching frequency. Protecting the Output StageThe output stage must be protected from a number of potentially hazardous conditions:Overheating: Class D’s output-stage power dissipation, though lower than that of linear amplifiers, can still reach levels that endanger the output transistors if the amplifier is forced to deliver very high power for a long time. To protect against dangerous overheating, temperature-monitoring control circuitry is needed. In simple protection schemes, the output stage is shut off when its temperature, as measured by an on-chip sensor, exceeds a thermal- shutdown safety threshold, and is kept off until it cools down. The sensor can provide additional temperature information, aside from the simple binary indication about whether temperature has exceeded the shutdown threshold. By measuring temperature, the control circuitry can gradually reduce the volume level, reducing power dissipation and keeping temperature well within limits —instead of forcing perceptible periods of silence during Thermal-shutdown events. Excessive current flow in the output transistors:The low on resistance of the output transistors is not a problem if the output stage and speaker terminals are properly connected, but enormous currents can result if these nodes are inadvertently short-circuited to one another, or to the positive or negative power supplies. If unchecked, such currents can damage the transistors or surrounding circuitry. Consequently, current-sensing output transistor protection circuitry is needed. In simple protection schemes, the output stage is shut off if the output currents exceed a safety threshold. In more sophisticated schemes, the current-sensor output is fed back into the amplifier—seeking to limit the output current to a maximum safe level, while allowing the amplifier to run continuously without shutting down. In these schemes, shutdown can be forced as a last resort if the attempted limiting proves ineffective. Effective current limiters can also keep the amplifier running safely in the presence of momentarily large transient currents due to speaker resonances.Under voltage: Most switching output stage circuits work well only if the positive power supply voltages are high enough. Problems result if there is an under voltage condition, where the supplies are too low. This issue is commonly handled by an under voltage lockout circuit, which permits the output stages to operate only if the power supply voltages are above an under voltage-lockout threshold.Output transistor turn-on timing:T he MH and ML output stage transistors (Figure 6) have very low on resistance. It is therefore important to avoid situations in which both MH and ML are on simultaneously, as this would create a low-resistance path fromVDD to VSS through the transistors and a large shoot-through current. At best, the transistors will heat up and waste power; at worst, the transistors may be damaged. Break-before-make control of the transistors prevents the shoot-through condition by forcing both transistors off before turning one on. The time intervals in which both transistors are off are called no overlap time or dead time.Figure 6. Break-before-make switching of output-stage transistors.。
PAM8003 滤波器无的 2.5W 双频带音频放大器说明书
FILTERLESS 2.5W CLASS-D STEREO AUDIO AMPLIFIERDescriptionThe PAM8003 is a 2.5W, Class-D audio amplifier. It offers low THD+N, allowing it to achieve high-quality sound reproduction. The new filterless architecture allows the device to drive the speaker directly,requiring no low-pass output filters, thus saving the system cost and PCB area.With the same numbers of external components, the efficiency of the PAM8003 is much better than that of class-AB cousins. It can extend the battery life, making it ideal for portable applications.The PAM8003 is available in SO-16 package.Features∙ 2.5W Output at 10% THD with a 5Ω Load and 5V Power Supply ∙ Filterless, Low Quiescent Current and Low EMI ∙ Low THD+N∙ 64-Step DC Volume Control ∙ Superior Low Noise ∙ Short Circuit Protection ∙ Thermal Shutdown∙ Few External Components to Save the Space and Cost ∙ RoHS Pass and Green Package∙ Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) ∙ Halogen and Antimony Free. “Green” Device (Note 3)Pin AssignmentsApplications∙ LCD Monitors / TVs ∙ Notebook Computers ∙ Portable Speakers∙Portable DVD Players, Game MachinesOrdering InformationNotes:1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.2. See https:///quality/lead-free/ for more information about Diodes Incorporate d’s definitions of Halogen - and Antimony-free, "Green" and Lead-free.3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and <1000ppm antimony compounds.Typical Applications Circuit ArrayPin DescriptionsFunctional Block DiagramAbsolute Maximum Ratings (@T A = +25°C, unless otherwise specified.)These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground.Recommended Operating Conditions(@T A = +25°C, unless otherwise specified.)Thermal InformationElectrical Characteristics (@T A = +25°C, V DD = 5V, Gain = 24dB, R L = 8Ω, unless otherwise specified.)Typical Performance Characteristics (@T A = +25°C, unless otherwise specified.)Typical Performance Characteristics (continued) (@T A = +25°C, unless otherwise specified.)Typical Performance Characteristics (cont.) (@T A = +25°C, unless otherwise specified.)Application Information1. When the PAM8803 works with LC filters, it should be connected with the speaker before it’s powered on, otherwise it will risk being damaged easily.2. When the PAM8003 works without LC filters, it’s better to add a ferrite chip bead at the outgoing line of speaker for suppressing the possi ble electromagnetic interference.3. The recommended operating voltage is 5.5V. When the PAM8003 is powered with four battery cells, it should be noted that the voltage of four new dry or alkaline batteries is over 6.0V, higher that its operation voltage, which will probably damage the device. Therefore, its recommended to use either four Ni-MH (Nickel Metal Hydride) rechargeable batteries or three dry or alkaline batteries.4. One should not make the input signal too large. Large signal can cause the clipping of output signal when increasing the volume. This will damage the device because of big gain of the PAM8004.5. When testing the PAM8803 without LC filters by using resistor instead of speakers as the output load, the test results, e.g. THD or efficiency, will be worse than those of using speaker as load.Test Setup for Performance TestingNotes: 4. The AP AUX-0025 low pass filter is necessary for class-D amplifier measurement with AP analyzer.5. Two 22μH inductors are used in series with load resistor to emulate the small speaker for efficiency measurement.Power Supply DecouplingThe PAM8003 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output THD and PSRR as low as possible. Power supply decoupling affects low frequency response. Optimum decoupling is achieved by using two capacitors of different types of noise on the power supply leads. For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resisitance (ESR) ceramic capacitor, typically 1.0µF, works best, placing it as close as possible to the device V DD terminal. For filtering lower-frequency noise signals, a large capacitor of 20µF (ceramic) or greater is recommended, placing it near the audio power amplifier.Input Capacitor (C I )Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized capacitor is needed to couple in low frequencies without severe attenuation. But in many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 100Hz to 150Hz. Thus, using a large input capacitor may not increase actual system performance. In this case, input capacitor (CI) and input resistance (RI) of the amplifier form a high-pass filter with the corner frequency determined by equation below.In addition to system cost and size, click and pop performance is affected by the size of the input the coupling capacitor, C I . A larger input coupling capacitor requires more charge to reach its quiescent DC voltage (nominally ½ V DD ). This charge comes from the internal circuit via the feedback and is apt to create pops upon device enable. Thus, by minimizing the capacitor size based on necessary low frequency response, turn-on pops can be minimized.C R 21f II C ∏=Application Information (continued)Analog Reference Bypass Capacitor (C BYP)The Analog Reference Bypass Capacitor (C BYP) is the most critical capacitor and serves several important functions. During start-up or recovery from shutdown mode, C BYP determines the rate at which the amplifier starts up. The second function is to reduce noise caused by the power supply coupling into the output drive signal. This noise is from the internal analog reference to the amplifier, which appears as degraded PSRR and THD+N.A ceramic bypass capacitor (C BYP) with values of 0.1μF to 1.0μF is recommended for the best THD and noise performance. Increasing the bypass capacitor reduces clicking and popping noise from power on/off and entering and leaving shutdown.Undervoltage Lock-Out (UVLO)The PAM8003 incorporates circuitry designed to detect low supply voltage. When the supply voltage drops to 2.0V or below, the PAM8003 outputs are disabled, and the device comes out of this state and starts to normal function when V DD≥ 2.2V.Short Circuit Protection (SCP)The PAM8003 has short circuit protection circuitry on the outputs to prevent damage to the device when output-to-output or output-to-GND short occurs. When a short circuit is detected on the outputs, the outputs are disabled immediately. If the short was removed, the device activates again.Over-temperature ProtectionThermal protection on the PAM8003 prevents the device from damage when the internal die temperature exceeds +140°C. There is a 15° tolerance on this trip point from device to device. Once the die temperature exceeds the thermal set point, the device outputs are disabled. This is not a latched fault. The thermal fault is cleared once the temperature of the die is reduced by 30°C. This large hysteresis will prevent motor boating sound well and the device begins normal operation at this point without external system intervention.How to Reduce EMI (Electro Magnetic Interference)A simple solution is to put an additional capacitor 1000μF at power supply term inal for power line coupling if the traces from amplifier to speakers are short (< 20cm).Most applications require a ferrite bead filter as shown in Figure 2. The ferrite filter reduces EMI of around 1 MHz and higher. When selecting a ferrite bead, choose one with high impedance at high frequencies, and low impedance at low frequencies.Figure 2. Ferrite Bead Filter to Reduce EMIMarking InformationPackage Outline DimensionsPlease see /package-outlines.html for the latest version.SO-16SEE DETAIL 'A'11 of 12 May 2017 © Diodes IncorporatedSuggested Pad LayoutPlease see /package-outlines.html for the latest version.SO-16PAM8003Document number: DS36421 Rev. 2 - 212 of 12 May 2017 © Diodes IncorporatedPAM8003Document number: DS36421 Rev. 2 - 2。
「掌握」D类音效功率放大器(Class D Audio Power Amplifier)
「掌握」D類音效功率放大器（Class D Audio Power Amplifier）音質與用電的新妥協方案（郭長佑／）2005/06/20導言：老一代的電子電機人，在學校上課時多半只聽過A類、B類、C類的功率放大電路（常用在音響系統的後級擴大），以及折衷式設計的AB類，並對各者的特性優劣、運用時機有所瞭解，但曾幾何時世界上又多出了一種D類放大器，此物是從何而來的呢？事實上，功率放大（簡稱：功放）電路不止ABC三類，也不是突然多出個D類，D類早已存在，其他還有E類、F類、G類、H類，甚至是跳跨列編的S類等，只是這些類型的電路運用機會低，或者與A、B、AB類相近再另行變化，所以也就鮮少提及。
▲圖說：美國國家半導體公司（National Semiconductor；NS）的高用電效益D類放大器：LM4670、LM4671，採行Tiny Micro SMD封裝，使其達到最小的空間精省與電路佈局彈性，另外也具有關閉模式以降低用電，適合用在手機、PDA等手持裝置。
（圖片來源／）AB類放大：音質與用電的妥協設計為何今日會盛行D類放大器呢？在如此問之前其實應當問過去至今為何AB類會盛行？在此我們不再詳述電路的細節運作原理，單就結果特性來說明，A類放大具有最佳的信號傳真性（電壓波形幾乎無失真），但卻相當耗用電能，一般來說電能利用率只有20％∼30％，舉例而言，倘若供應100W電力給A類放大機（擴大機），最後真正輸出到喇叭發聲功率的只有25W，其餘的75W統統是放大系統運作過程中的耗用，而且此一高耗能也會產生高廢熱，需要在放大電晶體上配裝厚高的散熱片來幫助散熱。
雖然A類電能利用率差，但信號完整是其可取之處，所以依然用在高檔專業音響中，發燒友為了享受無失真的完美音質，不會太在乎多耗3倍的電能。
至於B類放大，其電能利用率較高，理想上可至75％，但卻有交越失真的問題，上下波形中有一者會遭部分截斷，而無法全波完整放大，如此若用在音響系統就會有明顯的聲音粗糙變質。
Design of Class-D Audio Amplifiers
(3). D-to-S On-Resistance, RDS(ON) : Directly related to MOSFET conduction losses. Temperature dependent.
(4). Body Diode Reverse Recovery Characteristics, Qrr, trr , Irr , and S factor. Influence THD, EMI, and Efficiency. Temperature dependent. (5). Package : Power dissipation capability, current capability, internal inductance, internal resistance, electrical isolation, and mounting process.
Chun-Hsien Su
7
Efficiency: Class AB vs. Class D
[From TI’s report]
Chun-Hsien Su
8
Measured Efficiency
– TI-TPA2
Chun-Hsien Su
9
Temperature vs. Output Power
Architecture Analog/digital w/SDM
Feedback
Nonlinear LC
Audio source
PWM
Gate Driver
Modulation error Quantization error
Dead time Delay time
Single-bridge/Full bridge Filterless modulation scheme
Planet Audio BB2400.1
CONTENTSU S E R ’S M A N U A L2Introduction 2Features3What is included?3General precautions 3Installation precautions 3 Mounting the amplifier 4 Connecting the amplifier 5Important system considerations 5Tips for a safe system 6Low level input wiring 6Speaker wiring 7Power connectionsNormal and with Stiffening Capacitor9Bridging two Big Bang CLASS D Amplifiers 11Troubleshooting 12SpecificationsCongratulations on your purchase of a Planet Audio Big Bang Class D Amplifier.It has been designed, engineered and manufactured to bring you the highest level of performance and quality, and will afford you years of listening pleasure.Thank you for making Planet Audio choice for car audio entertainment!pageBB2400.1BB1400.1CLASS D MonoBlock Car Audio AmplifiersIntroductionWith the Planet Audio BB2 Class D amplifier series, we are introducing two new CLASS D amplifiers, both designed in the USA.These Big Bang models feature variable low pass and subsonic filters and a variable input gain control. These models also incorporate a phase selector switch to help compensate for time delays in subwoofer applications.For further flexibility in the use of a subwoofer, a variable 0-+18dB Bass Boost control has been included.You can control the subwoofer level with the remote level control module.Planet Audio understands that amplifiers are placed in many different kinds of installations, so we have also included an input sensitivity control to help you integrate the amp into your system regardless of the nature of your input source.A special feature on this Class D amp is DataLink circuitry, which allows you to “strap” (bridge) together two identical BB2 Class D amp models for an astounding total maximum output power of between 3800 and an astounding 6000 watts, depending on the model selected.FeaturesYour new Big Bang amplifier features the following:• Class D operation• MOSFET PWM (Pulse WidthModulated) Power Supply• One Ohm stable mono operation • Thermal, overload and speaker short protection• Soft turn-on circuit• Remote turn-on/turn-off circuit • Variable input gain control• Input voltage sensitivity selector • Variable subsonic filter: 15-40 Hz, 24dB/octave• Variable low pass filter: 50-150 Hz, 24dB/octave• Variable 0-+18dB Bass Boost • 0/180º Phase Shift selector• Nickel-plated RCA low level inputs • Nickel-plated speaker and power terminals• I n-line AGU fuse holder with fuse (BB2400.1 only)• LED power and protectionindicators• Black anodized heatsink• Remote subwoofer level controlInstallation precautionsBefore you drill or cut any holes,investigate your car's layout very carefully. T ake special care when you work near the gas tank, fuel lines,hydraulic lines and electrical wiring.Never operate the amplifier when it is unmounted. Attach all audio system components securely to prevent damage, especially in an accident.Before making or breaking power connections in your system, disconnect the vehicle battery. Confirm that your head unit or other equipment is turned off while connecting the input jacks and speaker terminals.If you need to replace the power fuse,replace it only with a fuse identical to that supplied with the amplifier. Using a fuse of a different type or rating may result in damage to your audio system or your amplifier which is not covered by the manufacturer's warranty.Mounting the amplifier1. Find a suitable location in the vehicle in which to mount the amplifier.2. Make sure there is sufficient air circulation around the intended mounting location.General precautionsBefore installing and using your new Planet Audio amplifier, please be-come familiar with all the information contained in this manual.Please keep this manual in a safe place for future reference.• Do not open or attempt to repair this unit yourself. Dangerous high voltages are present which may result in electric shock. Refer any repairs to a qualified service technician.• To avoid risk of electronic shock or damage to the amplifier , do not permit any of this equipment to become damp or wet from water or drinks. If this does occur, immediately unplug the power wires and send the amplifier to your local dealer or service center as soon as possible.• If there is smoke or any peculiar odor present during use or if there is damage to any of the component enclosures,immediately unplug the power cord and send the amplifier to your local dealer or service center as soon as possible .What is included?When first unpacking your new amplifier, please check first that the package contains all of the items below. If something is missing, contact the store where you purchased the amplifier.• Class D amplifier• Remote subwoofer level control • Remote subwoofer control cable • DataLink cable (for bridging two identical BB2 Class D amplifiers together)• Four (4) mounting screws3. Mark the location for the mounting hole screws by positioning the amplifier where you wish to install it. Use a scribe or mounting screw, inserted through each of the amp's mounting holes, to mark the mounting surface. If the mounting surface is carpeted, measure the hole centers and mark with a felt tip pen.4. Drill pilot holes in the mounting surface for the mounting screws. Place the amplifier in position, and attach the amplifier to the mounting surface securely using screws.Before doing any wiring, look through this manual and identify the diagrams to follow for power , input and speaker connections for your particularinstallation. Be sure you understand all the connections before you proceed.1. Connect the amplifier’s power ground terminal to the closest point on the chassis of the car. Keep this ground wire to less than 39" (100 cm)in length. Use 4 gauge (or heavier)wire.2. Connect the remote terminal to the remote output of the head unit using 16 gauge (or heavier) wire.3. Connect an empty fuse holder within 18" (45 cm) of the car battery, and run 4 gauge (or heavier) cable from this fuse to the amplifier location.The purpose of placing a fuse in this location is to protect your vehicle’s battery in the event that this wire accidentally touches the chassis ground on its run to the amplifier.Connecting the amplifier4. Check that the fuse holder is empty.Then connect the fuse holder to the "BATT+" connection on the amplifier.5. If multiple amplifiers are being used in your system, either:• Run a separate pair of cables from the battery and a chassis ground point to each amplifier . Each (+) cable must have its own inline fuse.-or-• Run a #0 cable from the fuse holder at the battery to a distribution block at or near the amplifier's location. Then run separate cables from the amplifier to this distribution block and toindependent chassis ground points.6. Connect all line inputs and outputs (if used) using high-quality cables.Connect all speakers, following the diagrams in this manual. Be sure to observe proper polarity to avoid audio phase problems.7. Insert fuse(s) into the battery fuse holder(s).8. Recheck all connections before powering up the amplifier.9. Set all level controls to minimum position, and set all crossover controls/switches to the desired frequency points.10. Power up the head unit and the amplifier . Then set the volume control on the head unit to about 3/4 volume,and adjust the amplifier’s input level control(s) to just below the level of distortion.11. Further fine tuning of the various controls may be necessary to obtainbest results.Important installation considerations for using this amplifier.SHOCK HAZARD! Do not open the case of this product. There are dangerous voltages present within the unit. There are no user-serviceable parts within the unit.The fuse ratings for these amps is described on the Specifications page of this manual. Although sufficient for normal working conditions,overloading the amp may result in blown fuses. Please try to avoid overloading the amp in this manner.Your BB 2 Class D amplifier is designed to run with a mini-mum load of 1 Ohm.Operating a BB 2 Class D am-plifier with a speaker imped-ance load below 1 Ohm may result in poor sound quality and damage to the amplifier circuitry. Such damage is not covered under the warranty for this product.When making electrical connections to the amplifier, please observe the following:• Always use 4GA or heavier wire for power and ground connections.• Wire the amplifier directly to the car battery. Make sure there is circuit protection (such as a fuse) on the positive power lead within 18” of the battery.• When making a ground connection,always use the shortest possible wire to a good chassis ground point.• Wire the remote turn-on connection to the remote turn-on lead of your EQ or head unit. In some cases, this may be the power antenna lead of the head unit.• Fuses protect BOTH the amplifier and the electrical system of your vehicle from faulty conditions. If you must replace a fuse on the amplifier,you must use a fuse of exactly the same type and rating. A different type of fuse or rating may result in damage or cause a fire.Tips for making your system as safe as possibleDo not mistake the input level control for a volume control! It is designed ONL Y to match the output level of your audio source to the input level of your amplifier.Do not adjust this input level to maximum unless your input level requires it.Ignoring these instructions will result in an input overload to the amplifier ,and excessive audio distortion. It can also cause the protection circuit to engage.Don't misuse thelevel control!Low Level Input and Remote Level Control ConnectionsLow-level (RCA) input wiring is preferred for best audio performance. Always usea high-quality RCA cable for best audio performance.Speaker ConnectionsPLEASE NOTE:This diagram shows the BB1400.1. Although the layout of therear panel varies slightly between BB1400.1 and BB2400.1, theconnectors themselves are functionally similar.RemoteSubwoofer Level ControlWithout Stiffening CapacitorWith StiffeningCapacitor(Fuse and fuseholderprovided with BB2400.1)groundpointWithout Stiffening CapacitorWith Stiffening Capacitorground pointPHASE SELECTOR 0Bridging T wo BB2400.1 or Two BB1400.1 AmplifiersPHSLAVEAMPLIFIER Rear PanelPOWER AND SPEAKER CONNECTIONS(SEE PREVIOUS PAGE FOR INPUT, DATALINK AND REMOTE LEVEL CONTROL CONNECTIONS)MASTER AMPLIFIER Rear panelto REMOTE TURN-ON terminal of head unitground pointPLEASE NOTE:In this manual, the BB1400.1 is shown, but the wiring connections are identical to those of the BB2400.1.TroubleshootingBB2400.1 • BB1400.1 Amplifier User’s Manual - page 11If you experience operation or performance problems with this product, compare your installation with the electrical wiring diagram on the previous pages. If problems persist,read the following troubleshooting tips which may help eliminate the problems.Amplifier will not power up.Check to make sure you have a good ground connection.Check that the Remote Input (Turn-On) has at least 3VDC.Check that there is battery power on the (+) terminal.Check that there is at least 12v.Check all fuses, replace if necessary.Make sure that the Protection LED is not illuminated. If it is lit, shut off the amplifier briefly, and then repower it.Protection LED comes on when amplifier is powered up.Check for short circuits on speaker leads.Turn down the volume control on the head unit to prevent overdriving.Remove speaker leads, and reset the amplifier. If the Protection LED still comes on, then the amplifier is faulty and needs servicing.No output.Check that all fuses are OK.Check that amplifier is properly grounded.Check that the Remote Input (Turn-On) has at least 3VDC.Check that the RCA audio cables are plugged into the proper inputs.Check all speaker wiring.Low output.Reset the Level Control.Check the Crossover Control settings.Audio present in only one channel.Check the RCA interconnect cables.Check all speaker wiring.High hiss in the speakers.Disconnect all RCA inputs to the amplifiers. If the hiss disappears, then plug in the component driving the amplifier and unplug its inputs. If the hiss disappears at this point, go on until the faulty/noisy component is found.It is best to set the amplifier's input level control as low as possible. The best subjective signal-to-noise ratio is achieved in this manner. Try to set the head unit as high as possible (without distortion) and the amp input level as low as possible.Squealing noise from speakers.Check for improperly grounded RCA interconnects.Distorted sound.Check that the Input Level Control is set to match the signal level of the head unit. Always try to set the Input Level as low as possible.Check that all crossover frequencies are properly set.Check for short circuits on the speaker leads.Amplifier gets very hot.Check that the minimum speaker impedance for the amp model is correct.Check that there is good air circulation around the amp. In some applications, it may be necessary to add and external cooling fan.Engine noise (static type)This is usually caused by poor quality RCA cables,which can pick up radiated noise. Use only the best quality cables, and route them away from power cables.Engine noise (alternator whine)Check that speaker leads are not shorted to the vehicle chassis.Check that the RCA grounds are not shorted to the vehicle chassis.Check that the head unit is properly grounded.SYMPTOMPOSSIBLE REMEDYSpecificationsBB2400.1 • BB1400.1 Amplifier User’s Manual - page 121900W x 11 Ohm Mono 10k OhmSelectable 100mV-2V or 2V-8V 50Hz-150Hz 100dB 50Hz-150Hz 15Hz-40Hz Variable 0 -+18dB Selectable 0/180º40A x 417-3/4"All specifications subject tochange without notice.into 4 Ohmsinto 1 OhmMAX POWERinto 1 OhmMin. speakerimpedance Inputimpedance InputsensitivityFrequency response Signal-to-noise ratio Crossover/filter rangelow pass subsonicBass Boost Phase Shift Fuse rating Dimensions:(6-7/8" x 2" x ...)W x 100W x 13000W x 11 Ohm Mono 10k OhmSelectable 100mV-2V or 2V-8V 50Hz-150Hz 100dB 50Hz-150Hz 15Hz-40Hz Variable 0 - +18dB Selectable 0/180º250A x 121-3/4"BB2400.1MODELCLASS D MonoBlock Car Audio AmplifiersBB1400.1MAX POWERMAX POWER150750475w x 1950w x 1。
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the input signal is a standard audio line level signal. This audio line level signal is sinusoidal with a frequency ranging from 20Hz to 20kHz typically. This signal is compared with a high frequency triangle or sawtooth waveform to create the PWM signal as seen in fig 2a below. This PWM signal is then used to drive the power stage, creating the amplified digital signal, and finally a low pass filter is applied to the signal to filter out the PWM carrier frequency and retrieve the sinusoidal audio signal (also seen in fig 2b).
2
non-linearity of Class B designs is overcome, without the inefficiencies of a Class A design. Efficiencies for Class AB amplifiers is about 50%. Class D – This class of amplifier is a switching or PWM amplifier as mentioned above. This class of amplifier is the main focus of this application note. In this type of amplifier, the switches are either fully on or fully off, significantly reducing the power losses in the output devices. Efficiencies of 90-95% are possible. The audio signal is used to modulate a PWM carrier signal which drives the output devices, with the last stage being a low pass filter to remove the high frequency PWM carrier frequency. From the above amplifier classifications, classes A, B and AB are all what is termed linear amplifiers. We will discuss the differences between Linear and Class D amplifiers in the next section. The block diagram of a linear amplifier is shown below in fig 1. In a linear amplifier the signals always remain in the analog domain, and the output transistors act as linear regulators to modulate the output voltage. This results in a voltage drop across the output devices, which reduces efficiency. Class D amplifiers take on many different forms, some can have digital inputs and some can have analog inputs. Here we will focus on the type which have analog inputs.
A Class D audio amplifier is basically a switching amplifier or PWM amplifier. There are a number of different classes of amplifiers. This application note takes a look at the definitions for the main classifications.
AN-1071
Feedback
Triangle Generator
+Vcc Nch Level Shift
+
-
COMP Error Amp
Deadtime Nch
+
Fig 1 Block Diagram of a Class D Amplifier
-Vcc
Fig 1 above shows the basic block diagram for a Half Bridge Class D amplifier, with the waveforms at each stage. This circuit uses feedback from the output of the half-bridge to help compensate for variations in the bus voltages. So how does a Class D amplifier work? A Class D amplifier works in very much the same way as a PWM power supply (we will show the analogy later). Let’s start with an assumption that
AN-1071
1
AN-1071
What is a Class D Audio Amplifier Theory of Operation
A Class D audio amplifier is basically a switching amplifier or PWM amplifier. There are a number of different classes of amplifiers. We will take a look at the definitions for the main classifications as an introduction: Class A – In a Class A amplifier, the output devices are continuously conducting for the entire cycle, or in other words there is always bias current flowing in the output devices. This topology has the least distortion and is the most linear, but at the same time is the least efficient at about 20%. The design is typically not complementary with a high and low side output devices. Class B – This type of amplifier operates in the opposite way to Class A amplifiers. The output devices only conduct for half the sinusoidal cycle (one conducts in the positive region, and one conducts in the negative region), or in other words, if there is no input signal then there is no current flow in the output devices. This class of amplifier is obviously more efficient than Class A, at about 50%, but has some issue with linearity at the crossover point, due to the time it takes to turn one device off and turn the other device on. Class AB – This type of amplifier is a combination of the above two types, and is currently one of the most common types of power amplifier in existence. Here both devices are allowed to conduct at the same time, but just a small amount near the crossover point. Hence each device is conducting for more than half a cycle but less than the whole cycle, so the inherent
Application Note AN-1071
Class D Audio Amplifier Basics
By Jun Honda & Jonathan Adams