Soft-switched full-bridge converters

• US 6,356,462 B1
• Filed: 02/05/2001
• Issued: 03/12/2002
• Est. Priority Date: 08/31/2000
• Status: Expired due to Term

• Current Assignee: Delta Electronics Incorporated
• Original Assignee: Delta Electronics Incorporated
• Inventors: Jang, Yungtaek, Jovanovic, Milan M.
• Primary Examiner(s): Han, Jessica
• Application Number:
  US09/775,636
• Publication Number:
  US 20020044461A1
• Time in Patent Office: 400 Days
• Field of Search: 363/16, 363/17, 363/56, 363/98, 363/131, 363/132
• US Class Current: 363/17
• 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 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• 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

A family of soft-switched, full-bridge pulse-width-modulated (FB PWM) converters provides zero-voltage-switching (ZVS) conditions for the turn-on of the bridge switches over a wide range of input voltage and output load. The FB PWM converters of this family achieve ZVS with the minimum duty cycle loss and circulating current, which optimizes the conversion efficiency. The ZVS of the primary switches is achieved by employing two magnetic components whose volt-second products change in the opposite directions with a change in phase shift between the two bridge legs. One magnetic component always operates as a transformer, where the other magnetic component can either be a coupled inductor, or uncoupled (single-winding) inductor. The transformer is used to provide isolated output(s), whereas the inductor is used to store the energy for ZVS.

Claims

1. A soft-switched, constant-frequency, full-bridge power converter with phase-shift modulation comprising:

an input power source;

a first and second bridge leg each comprising a pair of serially-connected controllable switching devices adapted to connect across said input power source, each of said controllable switching devices comprising a switch, an antiparallel diode coupled across said switch and a capacitor coupled across said switch;

a first and second magnetic device each having a plurality of windings formed around a corresponding magnetic core;

said first and second magnetic device coupled to said first and second bridge leg in an arrangement so that when corresponding switches in said first and second bridge leg are open and closed in phase the volt-second product of said windings of said first magnetic device is maximal and the volt-second product of said windings of said second magnetic device is minimal, and when corresponding switches in said first and second bridge leg are open and closed in antiphase the volt-second product of said windings of said first magnetic device is minimal and the volt-second product of said windings of said second magnetic device is maximal;

a plurality of capacitors coupled to said windings of said first and second magnetic devices to prevent their saturation by providing a volt-second balance of said windings;

an output circuit for coupling a load.

2. A power converter as in claim 1 wherein said first magnetic device is arranged as a transformer having primary and secondary windings, and wherein said second magnetic device is arranged as a coupled inductor having two windings that are connected in series, and wherein the magnetizing inductance of said coupled inductor is selected so that the energy stored in said magnetizing inductance is large enough to substantially discharge said output capacitance of each of said switching devices that is about to be turned on so that voltage across said each of said switching devices at the moment of turn-on is substantially reduced in the entire current range of said load.

3. A power converter as in claim 2 wherein said output circuit is coupled to said secondary winding of said transformer.

4. A power converter as in claim 1 wherein said second magnetic device is arranged as a transformer having primary and secondary windings, and wherein said first magnetic device is arranged as an inductor, and wherein the inductance of said inductor is selected so that the energy stored in said inductor is large enough to substantially discharge said output capacitance of said each of said switching devices that is about to be turned on so that voltage across said each of said switching devices that is about to be turned on at the moment of turn-on is substantially reduced in the entire current range of said load.

5. A power converter as in claim 4 wherein said output circuit is coupled to said secondary winding of said transformer.

6. A power converter as in claim 1 further comprising a plurality of resistors for precharging said plurality of capacitors immediately after said power source is applied to said power converter so that said plurality of capacitors provide required voltages for maintaining volt-second products of said windings of said first and second magnetic devices during a start-up period.

7. A power converter as in claim 1 wherein said output circuit is the full-wave rectifier.

8. A power converter as in claim 1 wherein said output circuit is the current doubler.

9. A power converter as in claim 1 wherein said output circuit comprises a filter.