AC/DC flyback converter

• US 20040252529A1
• Filed: 05/13/2003
• Published: 12/16/2004
• Est. Priority Date: 05/13/2003
• Status: Active Grant

• Current Assignee: Delta Electronics Incorporated
• Original Assignee: Delta Electronics Incorporated
• Inventors: Chang, Chien-Chung, Jovanovic, Milan M., Huber, Laszlo
• Granted Patent: US 6,950,319 B2
• Time in Patent Office: Days
• US Class Current: 363/21.12
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• 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 single-stage input-current-shaping (S²ICS) flyback converter achieves substantially reduced conduction losses in the primary side of the S²ICS flyback converter by connecting a bypass diode between the positive terminal of a full-bridge rectifier and the positive terminal of an energy-storage capacitor. An effective current interleaving between an energy-storage inductor and the bypass diode is thus obtained in the S²ICS flyback converter around the peak of the rectified line voltage, resulting in a significantly reduced input-current ripple and reduced current stress on the switch. Further, by rearranging the rectifiers in the ICS part of the S²ICS flyback converter in such a way that the energy-storage capacitor and the ICS inductor are connected to the ac line voltage through only two rectifiers, one diode forward-voltage drop is eliminated, which results in a substantially reduced conduction loss in the primary-side rectifiers.

Claims

1. A flyback converter with input-current shaping and output-voltage regulation, comprising:

a bridge rectifier coupled to receive an AC power supply voltage and having an output terminal providing a rectified voltage;

a transformer having a primary winding including a tap that divides the primary winding into a first portion and a second portion;

a switch switchably coupling the first portion of the primary winding to a ground terminal;

an energy-storage inductor coupled to the tap of the primary winding and having an input terminal;

a first rectifier coupling the output terminal of the bridge rectifier and the input terminal of the energy-storage inductor;

an energy-storage capacitor coupled between the second portion of the primary winding and the ground terminal; and

a second rectifier coupling the output terminal of the bridge rectifier and the energy-storage capacitor.

2. A flyback converter as in claim 1 further comprising:

a secondary winding of the transformer;

an output-filter capacitor;

a third rectifier coupling the secondary winding of the transformer and the output-filter capacitor;

an output terminal that connects a load across the output-filter capacitor and a second ground terminal.

3. A flyback converter as in claim 2, wherein the third rectifier comprises a Schottky rectifier.

4. A flyback converter as in claim 2, wherein the third rectifier comprises a synchronous rectifier.

5. A flyback converter as in claim 1 further comprising a control circuit for operating the transformer at the boundary of the discontinuous and continuous conduction modes.

6. A flyback converter as in claim 1, wherein the energy-storage inductor operates in a discontinuous conduction mode and the second rectifier becomes conducting around the peak of the rectified voltage when the rectified voltage is larger than the voltage across the energy-storage capacitor.

7. A flyback converter as in claim 6, wherein the current of the second rectifier is a discontinuous current interleaved with the discontinuous current of the energy-storage inductor.

8. A flyback converter as in claim 1 further comprising a voltage clamp to limit the voltage stress on the first rectifier.

9. A flyback converter as in claim 8, wherein the voltage clamp comprises a first RCD clamp.

10. A flyback converter as in claim 9 further comprising a second RCD clamp coupling the switch and the energy-storage capacitor.

11. A flyback converter as in claim 10, wherein the first RCD clamp and the second RCD clamp are combined.

12. A flyback converter with input-current shaping and output-voltage regulation, comprising:

a first bridge rectifier coupled to receive an AC power supply voltage and having an output terminal providing a first rectified voltage;

an energy-storage inductor coupled to receive the first rectified voltage from the first bridge rectifier;

a second rectifier coupled to receive the AC power supply voltage and having an output terminal providing a second rectified voltage;

an energy-storage capacitor coupled to receive the second rectified voltage from the second bridge rectifier;

a transformer having a primary winding including a tap that divides the primary winding into a first portion and a second portion;

said tap of the primary winding coupled to the energy storage inductor, and said second portion of the primary winding coupled to the energy-storage capacitor; and

a switch switchably coupling the first portion of the primary winding of the transformer to a ground terminal;

13. A flyback converter as in claim 12 further comprising:

a secondary winding of the transformer;

an output-filter capacitor;

a rectifier coupling the secondary winding of the transformer and the output-filter capacitor;

an output terminal connecting a load across the output-filter capacitor and a second ground terminal.

14. A flyback converter as in claim 13, wherein the rectifier comprises a Schottky rectifier.

15. A flyback converter as in claim 13, wherein the rectifier comprises a synchronous rectifier.

16. A flyback converter as in claim 12 further comprising a control circuit for operating the transformer at the boundary of the discontinuous and continuous conduction modes.

17. A flyback converter as in claim 12, wherein the energy-storage inductor operates in a discontinuous conduction mode and the second bridge rectifier becomes conducting around the peak of the second rectified voltage when the second rectified voltage is larger than the voltage across the energy-storage capacitor.

18. A flyback converter as in claim 17, wherein the current of the second bridge rectifier is a discontinuous current interleaved with the discontinuous current of the energy-storage inductor.

19. A flyback converter as in claim 12, wherein the first bridge rectifier and the second bridge rectifier include rectifiers common to both bridge rectifiers.

20. A flyback converter as in claim 12 further comprising a voltage clamp to limit the voltage stress on the rectifiers of the first bridge rectifier.

21. A flyback converter as in claim 20, wherein the voltage clamp comprises a first RCD clamp.

22. A flyback converter as in claim 21 further comprising a second RCD clamp coupling the switch and the energy-storage capacitor.

23. A flyback converter as in claim 22, wherein the first RCD clamp and the second RCD clamp are combined.