高升压比的耦合电感的介绍

Vout
= Vc1
+ Vc2
+ L + Vcn
= Vs
1+ k 1− D
(4)
where, k is the number of voltage doubler. With very low duty cycle, Vc2 can not be the product of turn ratio and input voltage because C2 can not be charged fully due to very short duty cycle. If the turn-on time ends prior to the charging of capacitor C2 to nVs, output voltage will be decreased in proportional to the charging voltage of C2. In this case, it is assumed that the duty cycle is enough to guarantee the charging time of C2. In the figure 1, k is 1. k is increased in proportion to the multiplier number. Figure 2 shows the boost rate of output voltage using the circuit of figure 1 with a continuous inductor current. In this case, input voltage has been set to 48V. Figure 2 shows the results not only for different number of multiplier but also for turn ratio at the same time. That is, if turn ratio is n, (4) can be expressed as follows:
Generally, the conventional method to step up the output voltage is using a transformer. In this case, additional losses caused by the transformer and the switch are generated. The modified boost converter using inductor coupling is better compared to the conventional high boost converter such as a cascade boost converter and a converter using a transformer.[4-6] The main features of these converters are a high conversion ratio, high efficiency, a single low voltage
High Boost Converter Using Voltage multiplier
Ju-Won Baek, Myung-Hyo Ryoo, Tae-Jin Kim, Dong-Wook Yoo, Jong-Soo Kim
Industrial Electric Research Center Korea Electrotechnology Research Institute 28-1, SungJudong, Changwon, Kyungnam
VC1
= VS
nD 1− D
, VC 2
=
nVs
(2)
where, n is turn ratio of L2/L1. Using (1) and (2), the
0-7803-9252-3/05/$20.00 ©2005 IEEE
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output voltage can be expressed as follows:
With a very high duty ratio, the output rectifier conducts only a very short time during each switching cycle, thus resulting in serious reverse recovery problems and an increase in the rating of the rectification diode. Also, the EMI problem is severe under this condition. Therefore, a number of modified boost converter topologies have been proposed to get higher conversion efficiency and voltage gain.[2-7]
I. INTRODUCTION
Reliability becomes more important to power supplies for industrial applications. So, power supplies have adopted a battery back-up system in several applications. In addition to that, renewable energy such as the fuel cell is a hot issue in the research field. The common power supply for the above applications is a high boost converter to step up the low input voltage to high output voltage. Usually, a high efficiency, high step up dc/dc converter that can generate 380Vdc bus from 48Vdc plant is one of the most important part for DC back up system and fuel cell application. [1]
Korea jwbaek@keri.re.kr
Abstract – With the increasing demand for renewable energy, distributed power included in fuel cells have been studied and developed as a future energy source. For this system, a power conversion circuit is necessary to interface the generated power to the utility. In many cases, a high step-up dc/dc converter is needed to boost low input voltage to high voltage output. Conventional methods using cascade dc/dc converters cause extra complexity and higher cost. The conventional topologies to get high output voltage use flyback dc/dc converters. They have the leakage components that cause stress and loss of energy that results in low efficiency.
Vc3
= Vs
1 1− D
,
D
=
Ton Ts
(1)
where, D is the duty ratio, Ton is the pulse width, Ts is the
switching period. Also, the capacitor voltage Vc1 and Vc2
can be expressed as follows:
switch, and simple topology. This topology can be modified to the different variants as described in [7].
This paper presents an improved high boost converter that can boost very low input voltage to high output voltage. The proposed circuit is made of a boost converter with a coupled inductor and a voltage multiplier. The number of multiplier can be adjusted to get a needed duty ratio; a higher boost rate is easily obtained from the voltage multiplier. In this paper, a 300W prototype is made and tested to verify and analyze the operation of the proposed topology.
Vout
= Vc1
+ Vc2
+ Vc3
= Vs
2 1− D
(3)
where, n is assumed to 1. If the voltage multiplier is increased, the output voltage can be expressed as the sum of voltages of output capacitors as follows:
The basic structure to obtain high boost rate is a cascade converter, which has low efficiency and complexity. To simplify the cascade circuit, the modified converter using one switch has been proposed.[2,3] However, it still has the same problem in efficiency and cost compared to the cascade converter.
This paper presents a high boost converter with a voltage multiplier and a coupled inductor. The secondary voltage of the coupled inductor is rectified using a voltage multiplier. High boost voltage is obtained with low duty cycle. Theoretical analysis and experimental results verify the proposed solutions using a 300W prototype.
D3
L2
C1
L1
D2
C2
D1
Ro
Vs
S
ห้องสมุดไป่ตู้C3
Fig. 1 the proposed high boost circuit
II. CONFIGURATION AND OPERATION PRINCIPLE
A. Circuit Configuration
Figure 1 shows the proposed high boost converter. A pair of inductors is coupled magnetically and a secondary side of coupled inductors is rectified using a voltage multiplier. The multiplier can consist of various types. In this case, a voltage doubler is used. If the inductor current is continuous, the capacitor voltage Vc3 can be expressed as follows: