Soft-switching techniques for power inverter legs

• US 20040228153A1
• Filed: 05/14/2003
• Published: 11/18/2004
• Est. Priority Date: 05/14/2003
• Status: Abandoned Application

• Current Assignee: City University of Hong Kong
• Original Assignee: City University of Hong Kong
• Inventors: Hui, Shu-Yuen Ron, Cao, Xiao Hong, Chung, Shu-Hung Henry
• Application Number:
  US10/437,622
• Publication Number:
  US 20040228153A1
• Time in Patent Office: Days
• US Class Current: 363/71
• 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 method of operating a power electronics circuit comprising an inverter and a load including a resonant tank, wherein said inverter is switched at a frequency f_s and said resonant tank has a resonant frequency f_r, wherein K<

f_r/f_s<

K+1 where K is an even-numbered integer.

2. A method of operating a power electronics circuit comprising an inverter and a load, wherein said load as first and second operating conditions associated with respective first (f_r1) and second (f_r2) resonant frequencies, f_r2 being greater than f_r1, and wherein said inverter is switched at first (f_s1) and second (f_s2) switching frequencies corresponding to said first and second operating conditions, f_s2 being greater than f_s1, and wherein K<

f_r2/f_s1<

K+1 where K is an even-numbered integer.

3. A method as claimed in claim 2 wherein an auxiliary resonant tank is provided between said inverter and said load and having a resonant frequency (f_a), and wherein K−

f_sf_s1<

K+1 where K is an even-numbered integer.

4. A method as claimed in claim 3 wherein f_s2>

f_a.

5. A method as claimed in claim 2 wherein f_s2>

f_r2.

6. A method as claimed in claim 2 wherein said power electronics circuit is an electronic ballast for driving a high intensity discharge lamp.

7. A method of operating a power electronics circuit comprising an inverter and a load, wherein said load as first and second operating conditions associated with respective first (f_r1) and second (f_r2) resonant frequencies, f_r2 being greater than f_r1, and wherein said inverter is switched at first (f_s1) and second (f_s2) switching frequencies corresponding to said first and second operating conditions, f_s2 being greater than f_s1, wherein an auxiliary resonant tank is provided between said inverter and said load and having a resonant frequency (f_a), and wherein K<

f_a/f_s1<

K+1 where K is an even-numbered integer, and wherein K<

f_r2/f_s1<

K+1, and f_s2>

f_r2 and f_s2>

f_a.

8. A method as claimed in claim 7 wherein f_a is close to f_r2.

9. A method of operating a power electronics circuit comprising an inverter and a load, wherein said load as first and second operating conditions associated with respective first (f_r1) and second (f_r2) resonant frequencies, f_r2 being greater than f_r1, and wherein said inverter is switched at first (f_s1) and second (f_s2) switching frequencies corresponding to said first and second operating conditions, f_s2 being greater than f_s1, wherein an auxiliary resonant tank is provided between said inverter and said load and having a resonant frequency (f_a), wherein K<

f_r2/f_s1<

K+1 and f_s1>

f_a.

10. A method of operating a power electronics circuit comprising an inverter and a load including a resonant tank, wherein an auxiliary resonant tank is provided between said inverter and said load whereby in the event of the load acting as a short-circuit during operation, current provided by said auxiliary resonant tank enables soft-switching of said inverter.

11. A power electronics circuit comprising an inverter, a load including a resonant tank, and an auxiliary resonant load provided between said inverter and said load.