Soft-switching techniques for power inverter legs

• US 7,110,269 B2
• Filed: 08/09/2005
• Issued: 09/19/2006
• Est. Priority Date: 05/14/2003
• Status: Active Grant

• Current Assignee: City University of Hong Kong
• Original Assignee: City University of Hong Kong
• Inventors: Cao, Xiao Hong, Hui, Shu-Yuen Ron
• Primary Examiner(s): Vo, Tuyet Thi
• Application Number:
  US11/199,778
• Publication Number:
  US 20060033453A1
• Time in Patent Office: 406 Days
• Field of Search: None
• US Class Current: 363/21.03
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: H05B 41/2856 against internal abnormal circuit conditions
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

This invention relates to new soft-switching techniques for minimizing switching losses and stress in power electronic circuits using inverter legs. By choosing the switching frequency with specific relationships with the resonant frequency of the power electronic circuits, the proposed switching technique enables the power electronic circuits to achieve soft switching under full load and short-circuit conditions at the defined frequencies for both capacitive and inductive loads. This technique can be applied to an electronic circuit with two switches connected in totem pole configuration between two dc voltage rails or commonly known as a power inverter leg or inverter arm. Examples of these circuits are class-D power converter, half-bridge power converters and full-bridge power converters or inverters. The proposed techniques allow inverter circuits with resistive, capacitive and inductive loads to achieve soft switching.

Claims

1. A circuit comprising an inverter having a switching frequency f_s and a resonant tank circuit electrically coupled with the inverter and configured to have a resonant frequency f_r such that K<

f_r/f_s<

K+1, wherein K is an even integer.

2. The circuit of claim 1, wherein the resonant tank circuit is an LCL resonant tank circuit.

3. The circuit of claim 1, wherein the resonant tank circuit is a multi-resonant tank circuit.

4. The circuit of claim 1, wherein the resonant tank circuit is configured such that the resonant frequency, f_r, is altered during operation of the circuit.

5. The circuit of claim 1, further comprising an auxiliary resonant tank circuit electrically coupled to the inverter and the resonant tank circuit, the auxiliary resonant tank circuit being configured to have a resonant frequency, f_a, such that K<

f_a/f_s<

K+1, wherein K is an even integer.

6. The circuit of claim 1, wherein the resonant tank circuit is configured to have a second resonate frequency, f_r2, such that f_r2<

f_r.

7. A circuit comprising an inverter having a switching frequency, f_s, a first resonant tank circuit electrically coupled with the inverter and configured to have a first resonant frequency f_r1 and a second resonant frequency f_r2 such that f_r1<

f_r2 and K<

f_s/f_r2<

K+1, where K is an even integer, and a second resonant tank circuit electrically coupled with the inverter and the first resonant tank circuit, the second resonant tank circuit having a resonant frequency f_a such that K<

f_a/f_s<

K+1.

8. The circuit of claim 7, wherein the inverter is configured to have a second switching frequency f_s2 such that f_s2>

f_s1 and f_s2>

f_r2.

9. The circuit of claim 7, wherein the inverter is configured to have a second switching frequency f_s2 such that f_s2>

f_s1, and f_s2>

f_a.

10. A method of supplying power to a load having a resonant frequency f_r, the method comprising switching an inverter coupled to the load at a switching frequency f_s such that K<

f_r/f_s<

K+1, where K is an even integer.