Efficient power conversion circuit having zero voltage switching

• US 20010036088A1
• Filed: 05/04/2001
• Published: 11/01/2001
• Est. Priority Date: 05/04/2000
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Wittenbreder, Ernest H. Jr.
• Granted Patent: US 6,560,127 B2
• Time in Patent Office: Days
• US Class Current: 363/17
• CPC Class Codes: H02M 3/33576 having at least one active switching element at the secondary side of an isolation transformer

Abstract

A highly efficient and simple power conversion circuit (300) having zero voltage switching (ZVS) includes a novel switch timing technique, such that the need for an leakage inductor connected in series with the primary circuit of the converter and rectifier diodes is eliminated. A switch timing circuit (351) located in an output side circuit (350) enables the use of the natural stored magnetic energy in the output side circuit (350) to drive the critical switching transitions to accomplish soft switching for all of the switches (314-317) in a full bridge forward converter (300) for all transitions. This power conversion circuit (300) includes a full bridge circuit (310) having plurality of switching devices (314-317) that intermittently couple the primary winding (327) to the input of the power converter (300). A transformer (326) couples to receive power from the full bridge circuit (310) into its primary winding (327). The output side circuit (310) includes the switching circuit (351) coupled to provide stored magnetic energy to drive the switching transitions of the switching devices (314-317) in the full bridge circuit (310). The switching circuit (351) closes at a predetermined time delay after the switching transitions in the full bridge circuit (310) to accomplish zero voltage switching for the plurality of switches in the full bridge circuit (310). A converter controller provides control signals to the full bridge and the switching circuits (310, 351).

Claims

1. A power converter having an input and output, comprising:

a full bridge circuit coupled to the input of the power converter;

a converter controller coupled to the full bridge circuit, to provide control signals thereto;

a transformer coupled to the full bridge circuit to receive power from the full bridge circuit into a primary winding thereof;

the full bridge circuit comprises a plurality of switching devices that intermittently couple the primary winding to the input of the power converter; and

an output side circuit connected to the secondary winding of the transformer and including a switching circuit coupled to provide stored magnetic energy to drive the switching transitions of the switching devices in the full bridge circuit, wherein the switching circuit closes at a predetermined time delay after the switching transitions in the full bridge circuit to accomplish zero voltage switching for the plurality of switches in the full bridge circuit.

2. A power converter as recited in

claim 1

, wherein the converter controller is a phase shift modulation controller.

3. A power converter as recited in

claim 1

, wherein the converter controller is a pulse width modulation controller.

4. A power converter as recited in

claim 1

, wherein the full bridge circuit comprises four switches controlled by the controller in alternating pairs to deliver power received from the input of the power converter to the primary winding.

5. A power converter as recited in

claim 1

, wherein the power converter further comprises an output filter interposed between the output side circuit and the output of the power converter.

6. A power converter as recited in

claim 1

, wherein in the predetermined time delay is 100 nano-seconds.

7. A power converter as recited in

claim 1

, wherein the switching circuit comprises a pair of parallel coupled branches, each branch including a switching device coupled in series with a magnetic storage device.

8. A power converter as recited in

claim 7

, wherein the magnetic storage device is an inductor.

9. A power converter as recited in

claim 7

, wherein the switching circuit comprises the plurality of switching devices selected from the group consisting of insulated gate bipolar transistors, bipolar junction transistors, metal oxide semiconductor controlled thyristors, and field effect transistors.

10. A power converter as recited in

claim 7

, wherein the switching device is a serially connected rectifier diode and a saturable core bead.

11. A power converter as recited in

claim 1

, wherein the switching circuit comprises:

a bridge having a first, second, third and fourth branch; and

an output choke coupled to the second and third branch, the output choke including an inductor.

12. A power converter as recited in

claim 11

, wherein the first, second, third, and fourth branch each include a serially coupled rectifier diode and a saturable core inductor.

13. A power converter as recited in

claim 11

, further comprising a saturable core inductor coupled between the input of the switching circuit and the bridge.

14. A power converter as recited in

claim 13

, wherein the first and fourth branch each include a serially coupled rectifier diode and a saturable core inductor and wherein the second and third branch each include at least one diode.

15. A converter as recited in

claim 1

, wherein the converter controller includes a switching device control means for turning on and off the first, second, third and fourth switching devices in a sequence to alternately connect the primary winding to the input of the power converter.

16. For use in a power converter having a controlled full bridge circuit coupled to a transformer, the bridge having a plurality of switching devices delivering power received from an input of the power converter to a primary winding of the transformer, a method of providing stored energy from a switching circuit coupled to the secondary winding of the transformer, comprising the steps of:

controlling the full bridge circuit to intermittently couple the primary winding to the input of the power converter; and

closing the switching circuit at a predetermined delay time after the closed switching transition of one of the plurality of switching devices.

17. A method as recited in

claim 16

, wherein the controlling step includes a step of providing control signals from the controller to the switching circuit and the switching devices in the full bridge circuit.

18. A method as recited in

claim 16

, wherein the controlling step includes a step of controlling the switching devices in alternating pairs to deliver power received from the input of the power converter to the primary winding.

19. A method as recited in

claim 16

, wherein the predetermined delay is 100 nano-seconds.