A SIMPLIFIED LOSSLESS PASSIVE SOFTSWITCHING SNUBBER FOR PWM HALF-BRIDGE
INVERTERS
2009 Second International Conference on Intelligent Computation Technology and Automation
Yuanyuan Yang
School of Electronics and InformationTongji University
Shanghai, Chinae19840106@sohu.com
Xu Weisheng
School of Electronics and Information
Tongji University Shanghai, China Xuweisheng@tongji.edu.cn
班級:控晶四乙
學號:4a02c076
姓名:王鈺傑
指導老師:王明賢
I. INTRODUCTION

Soft-switching methods can be broadly classified into two groups: active
one and passive one. In recent years, passive soft-switching has been
given renewed notice as having a better price/performance ratio than
their active counterparts [1]. And snubber technique is the only possible
way to achieve soft-switching through passive means. The snubber
technique is having an inductor and capacitor placed in series and
parallel with each power switch to reduce its di/dt and dv/dt, achieving
ZCS turn-on and ZVS turn-off or ZCS turn-off and ZVS turn-on for each
switch. Fig 1 shows the McMurray Snubber [2], which had been widely
used in PWM inverters. Although it can partly return the snubber energy
into DC rail, it is still lossy, dissipating the recovered energy in resistors.
Recently, many lossless passive snubber circuits have been proposed, but
they almost use transformers, whose parameters such as their associated
diode stress and leakage inductance problem still remain to be studied

. There have been great improvements in this field such as [3, 4], which
have an idea that takes advantage of transformer as a part of resonant
circuitry. In [5] the authors present a method adding additional voltage
stress to provide higher efficiency and larger duty ratio range
II. SIMPLIFIED LPSSS CIRCUIT ANALYSIS

Fig 2 shows the proposed simplified LPSSScircuit, which consists of two IGBT
switches 1 S ,2 S , and two diodes 1 D , 2 D that are reversely paralleled to
the main switches, and a snubberinductor s L which reduces the rate of turnoncurrent(di/dt) to achieve ZCS turn-on and restrains the reverse recovery
current of diodes,and a larger capacitor b C which has two functions: one is,
as a passive voltage source connected across the two snubber capacitors s1
C , s2 C ,guarantying the sum of both snubber capacitors’ voltages constant
and equal to the DC link voltage; the other is, as a transient energy storage,
recovering the snubber energy into the DC rail through the resonant
inductorr L . The simplified LPSSS circuit also includes asnubber diode s1 D
and a snubber capacitor s1 C for the upper main device 1 S and
symmetrically s2 D and s2 C for the lower main device 2 S , which can
reduce dv/dt to achieve ZVS turn-off for
each main switch and remain the circuit free
from parasitic oscillation. Because the upper and
lower main devices always operate
complementarily to each other during normal
PWM operation, to further guarantee the sum of
both snubber capacitor’ voltage constant, the two
snubber capacitor are connected to the midpoint
of the phase leg.
Fig 3 [6] shows the ideal
voltage operating
waveforms of s1 C and
s2 C during 1 S turns off
and 2 S turns on. In this
time, cs1 V increases,
cs2 V decreases and the
sum of both capacitors’
voltage remains constant.
3.1幾個假設受僱於
分析[7]：

在這個電路中的所有元件都是理想的;

提供感性負載，等效

電流源需要的負荷的地方

在減刑的研究;

為了簡化分析，S L是等於r L，

B C，作為無源電壓源E，大

夠了。 Ë= D U（直流電源電壓）。
3.2符號說明

1（ω）=1/1的

b

L

ç

是諧振角

次數11 / B Z = L C是

諧振特性阻抗

電路，其包括電感器。S L，R L和

電容器B C，1 / R S R。S L= L L L+ L;
CONCLUSION
簡化的無源無損軟開關緩衝電路已被本文提出。它由導通
/關斷緩衝電路再生電路，它包括一個較大的電容器和諧振電感器回收
存儲在此緩衝能量緩衝電容器為直流軌道，實現緩衝技術和共振的結合
技術。這種簡化的電路可以工作井具有高性能，低成本和無需額外的開
關或控制電路，它適合任何PWM逆變器。從仿真結果，這LPSSS電路可
以實現ZVS關斷/ ZCS導通主開關和最小化開關損耗和應力。然而，由於
簡單的拓撲的，這在大型提出的電路不能正常工作功率範圍有限的負載
電流和輸出功率。
References


http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5287874&url=ht
tp%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F5287481%2F5287873%
2F05287874.pdf%3Farnumber%3D5287874
http://gram.eng.uci.edu/~pelwww/passive_ss_inverters.pdf