Self-driven synchronous rectifier circuit

• US 20060109698A1
• Filed: 11/23/2004
• Published: 05/25/2006
• Est. Priority Date: 11/23/2004
• Status: Active Grant

• Current Assignee: Power-One Incorporated (ABB Limited)
• Original Assignee: Power-One Incorporated (ABB Limited)
• Inventors: Qu, Dayu
• Granted Patent: US 7,075,799 B2
• Time in Patent Office: Days
• US Class Current: 363/127
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary 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 DC-DC power converter has a transformer with a primary side and secondary side. A first power transistor is coupled between a first end of a first winding of the secondary side and a ground terminal. A second power transistor is coupled between a second end of the first winding and the ground terminal. A first driver transistor is coupled to a gate of the first power transistor, and a second driver transistor is coupled to a gate of the second power transistor. A separate driver winding taken off the secondary side of the transformer controls the gates of the first and second driver transistors. First and second inductors are coupled between the opposite ends of the first winding and an output of the power supply. First and second resistors are coupled between the gates of the first and second driver transistors and the ground terminal, respectively.

Claims

1. A power supply, comprising:

a transformer having a primary winding receiving an input voltage and having first and second windings on a secondary side of the transformer;

a driver winding responsive to the input voltage;

a first power transistor having a first conduction terminal coupled to a first end of the first winding, a second conduction terminal coupled to a ground terminal, and a control terminal coupled to a first end of the second winding;

a second power transistor having a first conduction terminal coupled to a second end of the first winding, a second conduction terminal coupled to the ground terminal, and a control terminal coupled to a second end of the second winding;

a first driver transistor having a first conduction terminal coupled to the control terminal of the first power transistor, a second conduction terminal coupled to the ground terminal, and a control terminal coupled to a first end of the driver winding;

a second driver transistor having a first conduction terminal coupled to the control terminal of the second power transistor, a second conduction terminal coupled to the ground terminal, and a control terminal coupled to a second end of the driver winding;

a first inductor coupled between the first end of the first winding and an output of the power supply; and

a second inductor coupled between the second end of the first winding and the output of the power supply.

2. The power supply of claim 1, wherein the driver winding includes a center tap coupled to the ground terminal.

3. The power supply of claim 1, further including a capacitor coupled between the output of the power supply and the ground terminal.

4. The power supply of claim 1, further including:

a first resistor coupled between the control terminal of the first driver transistor and the ground terminal; and

a second resistor coupled between the control terminal of the second driver transistor and the ground terminal.

5. The power supply of claim 1, wherein the first and second power transistors are metal oxide semiconductor field effect transistors.

6. The power supply of claim 1, wherein the first and second driver transistors are metal oxide semiconductor field effect transistors.

7. The power supply of claim 1, wherein the primary winding includes a center tap coupled for receiving the input voltage.

8. The power supply of claim 1, further including:

a third power transistor having a first conduction terminal coupled to a first end of the primary winding, and a second conduction terminal coupled to the ground terminal;

a first pulse width modulated (PWM) control circuit having an input coupled to the output of the power supply and an output coupled to a control terminal of the third power transistor;

a fourth power transistor having a first conduction terminal coupled to a second end of the primary winding, and a second conduction terminal coupled to the ground terminal; and

a second PWM control circuit having an input coupled to the output of the power supply and an output coupled to a control terminal of the fourth power transistor.

9. A self-driven synchronous rectification circuit, comprising:

a transformer having a primary winding receiving an input voltage and having first and second on a secondary side of the transformer;

a driver winding responsive to the input voltage;

a first power transistor having a first conduction terminal coupled to a first end of the first winding, a second conduction terminal coupled to a ground terminal, and a control terminal coupled to a first end of the second winding;

a first driver transistor having a first conduction terminal coupled to the control terminal of the first power transistor, a second conduction terminal coupled to the ground terminal, and a control terminal coupled to a first end of the driver winding; and

a first inductor coupled between the first end of the first winding and an output of the power supply.

10. The self-driven synchronous rectification circuit of claim 9, comprising:

a second power transistor having a first conduction terminal coupled to a second end of the first winding, a second conduction terminal coupled to the ground terminal, and a control terminal coupled to a second end of the second winding;

a second driver transistor having a first conduction terminal coupled to the control terminal of the second power transistor, a second conduction terminal coupled to the ground terminal, and a control terminal coupled to a second end of the driver winding; and

a second inductor coupled between the second end of the first winding and the output of the power supply.

11. The self-driven synchronous rectification circuit of claim 10, further including:

a first resistor coupled between the control terminal of the first driver transistor and the ground terminal; and

a second resistor coupled between the control terminal of the second driver transistor and the ground terminal.

12. The self-driven synchronous rectification circuit of claim 10, wherein the primary winding includes a center tap coupled for receiving the input voltage.

13. The self-driven synchronous rectification circuit of claim 10, further including:

a third power transistor having a first conduction terminal coupled to a first end of the primary winding, and a second conduction terminal coupled to the ground terminal;

a first pulse width modulated (PWM) control circuit having an input coupled to the output of the power supply and an output coupled to a control terminal of the third power transistor;

a fourth power transistor having a first conduction terminal coupled to a second end of the primary winding, and a second conduction terminal coupled to the ground terminal; and

a second PWM control circuit having an input coupled to the output of the power supply and an output coupled to a control terminal of the fourth power transistor.

14. The self-driven synchronous rectification circuit of claim 9, wherein the driver winding includes a center tap coupled to the ground terminal.

15. In a power conversion circuit, a transformer having a primary winding receiving an input voltage and having first and second windings on a secondary side of the transformer, the power conversion circuit comprising:

a driver winding responsive to the input voltage;

a first metal oxide semiconductor field effect transistor (MOSFET) having a drain coupled to a first end of the first winding, a source coupled to a ground terminal, and a gate coupled to a first end of the second winding; and

a second MOSFET having a drain coupled to the gate of the first MOSFET, a source coupled to the ground terminal, and a gate coupled to a first end of the driver winding.

16. The power conversion circuit of claim 15, further including:

a third MOSFET having a drain coupled to a second end of the first winding, a source coupled to the ground terminal, and a gate coupled to a second end of the second winding;

a fourth MOSFET having a drain coupled to the gate of the third MOSFET, a source coupled to the ground terminal, and a gate coupled to a second end of the driver winding;

a first inductor coupled between the first end of the first winding and an output of the power supply; and

a second inductor coupled between the second end of the first winding and the output of the power supply.

17. The power conversion circuit of claim 16, further including:

a first resistor coupled between the gate of the second MOSFET and the ground terminal; and

a second resistor coupled between the gate of the fourth MOSFET and the ground terminal.

18. The power conversion circuit of claim 15, wherein the driver winding includes a center tap coupled to the ground terminal.

19. In a DC-DC power converter, a transformer having a primary side responsive to an input voltage and having a secondary side, the DC-DC power converter comprising:

a driver winding responsive to the input voltage;

a first power transistor having a first conduction terminal coupled to a first end of a first winding of the secondary side, a second conduction terminal coupled to a ground terminal, and a control terminal coupled to a first end of a second winding of the secondary side; and

a first driver transistor having a first conduction terminal coupled to the control terminal of the first power transistor, a second conduction terminal coupled to the ground terminal, and a control terminal coupled to a first end of the driver winding.

20. The DC-DC power converter of claim 19, further including:

a second power transistor having a first conduction terminal coupled to a second end of the first winding, a second conduction terminal coupled to the ground terminal, and a control terminal coupled to a second end of the second winding;

a second driver transistor having a first conduction terminal coupled to the control terminal of the second power transistor, a second conduction terminal coupled to the ground terminal, and a control terminal coupled to a second end of the driver winding;

a first inductor coupled between the first end of the first winding and an output of the power supply; and

a second inductor coupled between the second end of the first winding and the output of the power supply.

21. The DC-DC power converter of claim 20, further including:

a first resistor coupled between the control terminal of the first driver transistor and the ground terminal; and

a second resistor coupled between the control terminal of the second driver transistor and the ground terminal.

22. The DC-DC power converter of claim 20, wherein the first and second power transistors are metal oxide semiconductor field effect transistors.

23. The DC-DC power converter of claim 20, wherein the first and second driver transistors are metal oxide semiconductor field effect transistors.

24. The DC-DC power converter of claim 20, wherein the primary winding includes a center tap coupled for receiving the input voltage.

25. The DC-DC power converter of claim 20, further including:

a third power transistor having a first conduction terminal coupled to a first end of the primary winding, and a second conduction terminal coupled to the ground terminal;

a first pulse width modulated (PWM) control circuit having an input coupled to the output of the power supply and an output coupled to a control terminal of the third power transistor;

a fourth power transistor having a first conduction terminal coupled to a second end of the primary winding, and a second conduction terminal coupled to the ground terminal; and

a second PWM control circuit having an input coupled to the output of the power supply and an output coupled to a control terminal of the fourth power transistor.

26. The DC-DC power converter of claim 19, wherein the driver winding includes a center tap coupled to the ground terminal.