Quasi resonant push-pull converter and control method thereof

• US 9,252,677 B2
• Filed: 01/21/2012
• Issued: 02/02/2016
• Est. Priority Date: 01/28/2011
• Status: Active Grant

• Current Assignee: Lian Zheng Electronics Shenzhen Co., Ltd. (Eaton Corporation PLC.)
• Original Assignee: Lian Zheng Electronics Shenzhen Co., Ltd. (Eaton Corporation PLC.)
• Inventors: He, Zhifeng, Yang, Yucheng
• Primary Examiner(s): PATEL, RAJNIKANT B
• Application Number:
  US13/982,207
• Publication Number:
  US 20140022826A1
• Time in Patent Office: 1,473 Days
• Field of Search: 363 16- 20, 363/21.04, 363/21.06, 363/25
• US Class Current: 1/1
• 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 3/3372 of the parallel type
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• 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

The invention relates to a quasi-resonant push-pull converter and the method for controlling the same, said push-pull converter comprising: a direct current (DC) input power supply configured to supply DC input for the converter; a first power input unit and a second power input unit, connected to said DC input power supply, respectively and configured to supply input for the converter in different periods, comprising a first power switching tube and a second power switching tube, a first primary winding and a second primary winding; a power output circuit, configured to supply output of the converter, comprising secondary windings and full-bridge rectification circuits; a first output capacitor and a second output capacitor connected to said power output circuit and configured to store DC electric energy output by the power output circuit in which a resonant element is arranged to achieve a quasi-resonant switching circuit through voltage feedback; and a switching circuit being controlled through voltage feedback, whereby turns ratio of the primary windings and the secondary windings of the push-pull converter is controlled.

Claims

1. A quasi-resonant push-pull converter comprising:

a transformer having a primary winding and a secondary winding;

an input circuit configured to apply a DC power source to the primary winding of the transformer;

a resonant circuit;

a rectifier circuit having an input coupled to the secondary winding and an output coupled to the resonant circuit; and

a switching circuit configured to modify a coupling of the secondary winding to the resonant circuit via the rectifier circuit responsive to a voltage of the DC power source.

2. The converter of claim 1, wherein the switching circuit is configured to change a turns ratio applied to the rectifier circuit.

3. The converter of claim 2, wherein the switching circuit is configured to change the turns ratio to control an efficiency of the converter.

4. The converter of claim 1:

wherein the rectifier circuit comprises;

a first rectifier circuit having an input coupled to first and second terminals of the secondary winding and an output coupled to an input of the filter circuit; and

a second rectifier circuit having an input coupled to third and fourth terminals of the secondary winding; and

wherein the switching circuit is configured to couple and decouple an output of second rectifier circuit to and from the output of the first rectifier circuit.

5. The converter of claim 4, wherein the switching circuit comprises first and second switches configured to couple and decouple the output of second rectifier circuit to and from the output of the first rectifier circuit.

6. The converter of claim 4, wherein the first and second rectifier circuits are full-bridge rectifier circuits.

7. A method of operating a quasi-resonant push-pull converter comprising an input circuit configured to apply a DC power source to a primary winding of a transformer, a rectifier circuit coupled to a secondary winding of the transformer and an output filter coupled to an output of the rectifier circuit, the method comprising:

selectively modifying a coupling of the secondary winding to the output filter via the rectifier circuit responsive to a voltage of the DC power source to control an efficiency of the converter.

8. The method of claim 7, wherein selectively modifying a coupling of the secondary winding to the output filter via the rectifier circuit responsive to a voltage of the DC power source to control an efficiency of the converter comprises changing a turns ratio applied to rectifier circuit.

9. The method of claim 7, wherein the rectifier circuit comprises a first rectifier having an input coupled to first and second terminals of the secondary winding and an output coupled to an input of the filter circuit and a second rectifier circuit having an input coupled to third and fourth terminals of the secondary winding and wherein selectively modifying a coupling of the secondary winding to the output filter via the rectifier circuit responsive to a voltage of the DC power source to control an efficiency of the converter comprises coupling and decoupling an output of the second rectifier circuit to and from the output of the first rectifier circuit responsive to the voltage of the DC power source.

10. The method of claim 9, wherein the first rectifier circuit and the second rectifier circuit are full-bridge rectifier circuits.

11. The method of claim 7, wherein selectively modifying a coupling of the rectifier circuit responsive to a voltage of the DC power source to control an efficiency of the converter comprises selectively modifying a coupling of the rectifier circuit responsive to a voltage of the DC power source to maintain resonant mode operation of a switching device of the input circuit as the voltage of the DC source changes.