NCP1351的原理和使用方法
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variable, Fsw related losses decrease:
Coss和门电荷损耗 Coss and gate charge losses 泄漏感抗损耗 Leakage inductance losses
PSWITCHING
1 2 COSS VDS Fsw 2
PGATE VGS QG Fsw
-50.0 longer) to deliver the necessary output power: 4.68m 4.wk.baidu.com1m
4.73m time in seconds
Fsw1 @ Pout1
4.76m
4.68m
Fsw2 @ Pout2
4.71m
4.73m time in seconds
Pout1 > Pout2
Quasi Resonant and Fixed Frequency
固定开关频率
Fixed Fsw
准谐振
Quasi resonant
频率
Frequency
固定Fixed
可变Variable (开关频率 最小时功率最高(max
power at min Fsw)
轻载能效
Light Load Efficiencies
面向快速简单的固定导通时间设计的资源
Resources for quick and easy fixed on time designs
10
www.onsemi.com.cn
控制拓扑结构比较 Control Topology Comparison
固定开关频率
Fixed Fsw
准谐振
Quasi resonant
固定导通时间
Fixed on time
频率
Frequency
固定Fixed
可变Variable (开关频 可变Variable (开关频 率最小时功率最高 率最小时功率最高
(max power at min Fsw) max power at max Fsw)
轻载能效
Light Load Efficiencies
议程Agenda
1. 当前水准：准谐振和固定频率
State of the art: quasi resonant and fixed frequency
2. 用于反激的固定导通时间(FON)控制介绍
Introduction to the fixed on time control for flybacks
固定频率、准谐振和固定导通时间比较
Fixed frequency, quasi resonant, and fixed on time comparison
4.
5. 6. 7.
设计方法学及示例
Design methodology and example
将您的固定频率适配器更新为固定导通时间模式
Update your fixed frequency adapter to fixed on time
Pleak 1 2 Lleak I peak Fsw 2
FOT大幅提高轻载能效
FOT dramatically improves light load efficiency
9
www.onsemi.com.cn
议程Agenda
1.
当前水准：准谐振和固定频率
State of the art: quasi resonant and fixed frequency
1.30
3.30 300m 2.30
1
Plot1 idrain in amperes
350 300m
1
Plot2 vdrain in volts
250 -700m 150
2
350 50.0 250 -50.0 150 4.78m
Plot2 vdrain in volts
4.71m
• 峰值电流保持恒定，而开关频率则会变化(改变关闭时间)，以提供必需 50.0 2 的输出功率：The peak current is constant, switching frequency changes (Off time gets
增添额外功能性的技巧与决窍
Tips and tricks to add additional functionality
面向快速简单的固定导通时间设计的资源
Resources for quick and easy fixed on time designs
5
3.30
Plot1 idrain in amperes
2.
3.
用于反激的固定导通时间(FON)控制介绍
Introduction to the fixed on time control for flybacks
固定频率、准谐振和固定导通时间比较
Fixed frequency, quasi resonant, and fixed on time comparison
conditions, Fsw increases until it hits the Ct clamp: fault
8
www.onsemi.com.cn
固定导通时间(FOT) – 开关损耗
FOT – Switching Losses
由于频率可变，与开关频率相关的损耗减少：As the frequency is
议程Agenda
1.
当前水准：准谐振和固定频率
State of the art: quasi resonant and fixed frequency
2.
3.
用于反激的固定导通时间(FON)控制介绍
Introduction to the fixed on time control for flybacks
idrain
2 v drain
2.30
1 idrain 2 v drain
www.onsemi.com.cn
固定导通时间(FOT)–工作原理
1.30
Fixed On Time (FOT) – Principle of Operation
-700m 峰值电流保持恒定，可用用户选择 Constant peak current, user selectable
www.onsemi.com.cn
如何采用固定导通时间控制器进行设计
How to Design with a Fixed On-Time Controller
您优化轻载能效的关键所在
Your Key to Optimizing Light Load Efficiency
www.onsemi.com.cn
固定导通时间(FOT)–工作原理
Fixed On Time (FOT) – Principle of Operation
Pout , DCM 1 Lp I peak 2 Fsw 2
1 Lp I peak 2 I valley 2 Fsw 2
Pout ,CCM
峰值电流通过控制器来保持恒定 the peak current is kept constant by the
增添额外功能性的技巧与决窍
Tips and tricks to add additional functionality
面向快速简单的固定导通时间设计的资源
Resources for quick and easy fixed on time designs
3
www.onsemi.com.cn
准谐振和固定频率
工作模式
Operating mode
变压器尺寸
Transformer Size
连续导电模式/非连续 边界导电模式 导电模式CCM/DCM BCM (Borderline) 正常 Normal 较大 Larger 正常 Normal 较小 Smaller
电磁干扰 EMI
必须提升宽输出负载范围下的能效 Must improve the efficiency for a wide output load range 必须改善待机能耗 Must improve the standby
6. 增添额外功能性的技巧与决窍
Tips and tricks to add additional functionality
7. 面向快速简单的固定导通时间设计的资源
Resources for quick and easy fixed on time designs
2
www.onsemi.com.cn
4
www.onsemi.com.cn
议程Agenda
1.
当前水准：准谐振和固定频率
State of the art: quasi resonant and fixed frequency
2.
3.
用于反激的固定导通时间(FON)控制介绍
Introduction to the fixed on time control for flybacks
固定频率、准谐振和固定导通时间比较
Fixed frequency, quasi resonant, and fixed on time comparison
4.
5. 6. 7.
设计方法学及示例
Design methodology and example
将您的固定频率适配器更新为固定导通时间模式
Update your fixed frequency adapter to fixed on time
4.
5. 6. 7.
设计方法学及示例
Design methodology and example
将您的固定频率适配器更新为固定导通时间模式
Update your fixed frequency adapter to fixed on time
增添额外功能性的技巧与决窍
Tips and tricks to add additional functionality
3. 固定频率、准谐振和固定导通时间比较
Fixed frequency, quasi resonant, and fixed on time comparison
4. 设计方法学及示例
Design methodology and example
5. 将您的固定频率适配器更新为固定导通时间模式
Update your fixed frequency adapter to fixed on time
controller
频率发生变化以满足上述等式 the frequency varies to satisfy the above
equations
缺少环路控制(短路，启动)时， Fsw被(Ct针对NCP1351进行)钳位
in lack of loop control (short-circuit, startup), Fsw is clamped (by Ct for the NCP1351)
开关频率由反馈回路进行控制
The FB loop controls the switching frequency
7
www.onsemi.com.cn
固定导通时间(FOT) – 可变开关频率
Load
FOT – Variable Switching Frequency
Ct
(时序电容电压 Timing capacitor voltage)
正常 Normal (采用跳 周期或频率反走with
skip mode or freq foldback)
谷底跳适问题(噪声)
Valley jumping problem (noise) Max Fsw at min Pout
满载能效
Full Load Efficiencies
正常 Normal
最佳 Best
4.76m
4.68m
• 频率最高时提供的功率最大 Maximum4.78m is delivered at maximum frequency Power 4.71m 4.73m 4.76m
time in seconds
4.73m time in seconds
4.76m
6
www.onsemi.com.cn
由回路控制
Controlled by the loop
Fsw 钳位clamp
在正常操作模式，回路固定着频率，而非Ct ！In normal operation, the
loop fixes the frequency, NOT Ct!
轻载条件下，峰值电流减小，开关频率下降。这就限制了可听噪 声问题。In light load conditions, Ipeak reduces and Fsw goes down. This limits audible noise problems. 满载条件下，开关频率增加，直至其碰到Ct钳位：故障 In full load
Coss和门电荷损耗 Coss and gate charge losses 泄漏感抗损耗 Leakage inductance losses
PSWITCHING
1 2 COSS VDS Fsw 2
PGATE VGS QG Fsw
-50.0 longer) to deliver the necessary output power: 4.68m 4.wk.baidu.com1m
4.73m time in seconds
Fsw1 @ Pout1
4.76m
4.68m
Fsw2 @ Pout2
4.71m
4.73m time in seconds
Pout1 > Pout2
Quasi Resonant and Fixed Frequency
固定开关频率
Fixed Fsw
准谐振
Quasi resonant
频率
Frequency
固定Fixed
可变Variable (开关频率 最小时功率最高(max
power at min Fsw)
轻载能效
Light Load Efficiencies
面向快速简单的固定导通时间设计的资源
Resources for quick and easy fixed on time designs
10
www.onsemi.com.cn
控制拓扑结构比较 Control Topology Comparison
固定开关频率
Fixed Fsw
准谐振
Quasi resonant
固定导通时间
Fixed on time
频率
Frequency
固定Fixed
可变Variable (开关频 可变Variable (开关频 率最小时功率最高 率最小时功率最高
(max power at min Fsw) max power at max Fsw)
轻载能效
Light Load Efficiencies
议程Agenda
1. 当前水准：准谐振和固定频率
State of the art: quasi resonant and fixed frequency
2. 用于反激的固定导通时间(FON)控制介绍
Introduction to the fixed on time control for flybacks
固定频率、准谐振和固定导通时间比较
Fixed frequency, quasi resonant, and fixed on time comparison
4.
5. 6. 7.
设计方法学及示例
Design methodology and example
将您的固定频率适配器更新为固定导通时间模式
Update your fixed frequency adapter to fixed on time
Pleak 1 2 Lleak I peak Fsw 2
FOT大幅提高轻载能效
FOT dramatically improves light load efficiency
9
www.onsemi.com.cn
议程Agenda
1.
当前水准：准谐振和固定频率
State of the art: quasi resonant and fixed frequency
1.30
3.30 300m 2.30
1
Plot1 idrain in amperes
350 300m
1
Plot2 vdrain in volts
250 -700m 150
2
350 50.0 250 -50.0 150 4.78m
Plot2 vdrain in volts
4.71m
• 峰值电流保持恒定，而开关频率则会变化(改变关闭时间)，以提供必需 50.0 2 的输出功率：The peak current is constant, switching frequency changes (Off time gets
增添额外功能性的技巧与决窍
Tips and tricks to add additional functionality
面向快速简单的固定导通时间设计的资源
Resources for quick and easy fixed on time designs
5
3.30
Plot1 idrain in amperes
2.
3.
用于反激的固定导通时间(FON)控制介绍
Introduction to the fixed on time control for flybacks
固定频率、准谐振和固定导通时间比较
Fixed frequency, quasi resonant, and fixed on time comparison
conditions, Fsw increases until it hits the Ct clamp: fault
8
www.onsemi.com.cn
固定导通时间(FOT) – 开关损耗
FOT – Switching Losses
由于频率可变，与开关频率相关的损耗减少：As the frequency is
议程Agenda
1.
当前水准：准谐振和固定频率
State of the art: quasi resonant and fixed frequency
2.
3.
用于反激的固定导通时间(FON)控制介绍
Introduction to the fixed on time control for flybacks
idrain
2 v drain
2.30
1 idrain 2 v drain
www.onsemi.com.cn
固定导通时间(FOT)–工作原理
1.30
Fixed On Time (FOT) – Principle of Operation
-700m 峰值电流保持恒定，可用用户选择 Constant peak current, user selectable
www.onsemi.com.cn
如何采用固定导通时间控制器进行设计
How to Design with a Fixed On-Time Controller
您优化轻载能效的关键所在
Your Key to Optimizing Light Load Efficiency
www.onsemi.com.cn
固定导通时间(FOT)–工作原理
Fixed On Time (FOT) – Principle of Operation
Pout , DCM 1 Lp I peak 2 Fsw 2
1 Lp I peak 2 I valley 2 Fsw 2
Pout ,CCM
峰值电流通过控制器来保持恒定 the peak current is kept constant by the
增添额外功能性的技巧与决窍
Tips and tricks to add additional functionality
面向快速简单的固定导通时间设计的资源
Resources for quick and easy fixed on time designs
3
www.onsemi.com.cn
准谐振和固定频率
工作模式
Operating mode
变压器尺寸
Transformer Size
连续导电模式/非连续 边界导电模式 导电模式CCM/DCM BCM (Borderline) 正常 Normal 较大 Larger 正常 Normal 较小 Smaller
电磁干扰 EMI
必须提升宽输出负载范围下的能效 Must improve the efficiency for a wide output load range 必须改善待机能耗 Must improve the standby
6. 增添额外功能性的技巧与决窍
Tips and tricks to add additional functionality
7. 面向快速简单的固定导通时间设计的资源
Resources for quick and easy fixed on time designs
2
www.onsemi.com.cn
4
www.onsemi.com.cn
议程Agenda
1.
当前水准：准谐振和固定频率
State of the art: quasi resonant and fixed frequency
2.
3.
用于反激的固定导通时间(FON)控制介绍
Introduction to the fixed on time control for flybacks
固定频率、准谐振和固定导通时间比较
Fixed frequency, quasi resonant, and fixed on time comparison
4.
5. 6. 7.
设计方法学及示例
Design methodology and example
将您的固定频率适配器更新为固定导通时间模式
Update your fixed frequency adapter to fixed on time
4.
5. 6. 7.
设计方法学及示例
Design methodology and example
将您的固定频率适配器更新为固定导通时间模式
Update your fixed frequency adapter to fixed on time
增添额外功能性的技巧与决窍
Tips and tricks to add additional functionality
3. 固定频率、准谐振和固定导通时间比较
Fixed frequency, quasi resonant, and fixed on time comparison
4. 设计方法学及示例
Design methodology and example
5. 将您的固定频率适配器更新为固定导通时间模式
Update your fixed frequency adapter to fixed on time
controller
频率发生变化以满足上述等式 the frequency varies to satisfy the above
equations
缺少环路控制(短路，启动)时， Fsw被(Ct针对NCP1351进行)钳位
in lack of loop control (short-circuit, startup), Fsw is clamped (by Ct for the NCP1351)
开关频率由反馈回路进行控制
The FB loop controls the switching frequency
7
www.onsemi.com.cn
固定导通时间(FOT) – 可变开关频率
Load
FOT – Variable Switching Frequency
Ct
(时序电容电压 Timing capacitor voltage)
正常 Normal (采用跳 周期或频率反走with
skip mode or freq foldback)
谷底跳适问题(噪声)
Valley jumping problem (noise) Max Fsw at min Pout
满载能效
Full Load Efficiencies
正常 Normal
最佳 Best
4.76m
4.68m
• 频率最高时提供的功率最大 Maximum4.78m is delivered at maximum frequency Power 4.71m 4.73m 4.76m
time in seconds
4.73m time in seconds
4.76m
6
www.onsemi.com.cn
由回路控制
Controlled by the loop
Fsw 钳位clamp
在正常操作模式，回路固定着频率，而非Ct ！In normal operation, the
loop fixes the frequency, NOT Ct!
轻载条件下，峰值电流减小，开关频率下降。这就限制了可听噪 声问题。In light load conditions, Ipeak reduces and Fsw goes down. This limits audible noise problems. 满载条件下，开关频率增加，直至其碰到Ct钳位：故障 In full load