Synchronous rectifier drive circuit and power supply including same

• US 6,570,268 B1
• Filed: 11/20/2000
• Issued: 05/27/2003
• Est. Priority Date: 11/20/2000
• Status: Expired due to Fees

• Current Assignee: Artesyn Technologies Incorporated (Artesyn Embedded Technologies, Inc.)
• Original Assignee: Artesyn Technologies Incorporated (Artesyn Embedded Technologies, Inc.)
• Inventors: Poynton, Ian, Perry, Marty
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/716,506
• Time in Patent Office: 918 Days
• Field of Search: 307/38, 307/39, 307/40, 307/31
• US Class Current: 307/38
• 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 dual output power converter, including a transformer having first and second secondary windings, a first synchronous rectifier coupled to the first secondary winding of the transformer for converting an alternating voltage at the first secondary winding to a first DC output voltage, a second synchronous rectifier coupled to the second secondary winding of the transformer for converting an alternating voltage at the second secondary winding to a second DC output voltage, and a drive circuit coupled to each of the first and second synchronous rectifiers for turning on the first and second synchronous rectifiers when the alternating voltage at the first and second secondary windings transition from a first polarity to a second polarity, and for turning off the first and second synchronous rectifiers when the alternating voltage at the first and second secondary windings transition from the second polarity to the first polarity.

Claims

1. A dual output power converter, comprising:

a transformer having first and second secondary windings;

a first synchronous rectifier coupled to the first secondary winding of the transformer for converting a first alternating voltage at the first secondary winding to a first DC output voltage;

a second synchronous rectifier coupled to the second secondary winding of the transformer for converting a second alternating voltage at the second secondary winding to a second DC output voltage; and

a drive circuit coupled to each of the first and second synchronous rectifiers for turning on the first and second synchronous rectifiers when the first alternating voltage at the first secondary winding and the second alternating voltage at the second secondary winding transition from a first polarity to a second polarity, and for turning off the first and second synchronous rectifiers when the first alternating voltage at the first secondary winding and the second alternating voltage at the second secondary winding transition from the second polarity to the first polarity,

wherein the drive circuit includes a first switch coupled to the first and second synchronous rectifiers and a second switch coupled to at least one of the first and second synchronous rectifiers.

2. The power converter of claim 1, wherein:

the first switch is for supplying a drive current to a control terminal of each of the first and second synchronous rectifiers when the first alternating voltage at the first secondary winding and the second alternating voltage at the second secondary winding are at the second polarity; and

the second switch is for shunting the drive current from the control terminals of the first and second synchronous rectifiers when the first alternating voltage at the first secondary winding and the second alternating voltage at the second secondary winding transition from the second polarity to the first polarity.

3. The power converter of claim 2, wherein the drive circuit further includes a pulse transformer having first and secondary windings for turning on the second switch when the first alternating voltage at the first secondary winding and the second alternating voltage at the second secondary winding transition from the second polarity to the first polarity.

4. The power converter of claim 3, wherein the drive circuit further includes a differentiator circuit coupled to the pulse transformer.

5. The power converter of claim 4, wherein the differentiator circuit includes:

a capacitor connected to the primary winding of the pulse transformer; and

a resistor connected in parallel with the primary winding of pulse transformer.

6. The power converter of claim 1, wherein:

the first synchronous rectifier includes a MOSFET; and

the second synchronous rectifier includes a MOSFET.

7. A dual output power converter, comprising:

a transformer having first and second secondary windings;

a first synchronous rectifier coupled to the first secondary winding of the transformer;

a second synchronous rectifier coupled to the second secondary winding of the transformer; and

a drive circuit coupled to each of the first and second synchronous rectifiers;

wherein the drive circuit includes a first switch coupled to the first and second synchronous rectifiers and a second switch coupled to at least one of the first and second synchronous rectifiers, and wherein the first switch is for supplying a drive current to a control terminal of each of the first and second synchronous rectifiers and the second switch is for shunting the drive current from the control terminals of the first and second synchronous rectifiers.

8. The power converter of claim 7, wherein:

the first switch is for supplying the drive current when a first alternating voltage at the first secondary winding and a second alternating voltage at the second secondary winding is at a first polarity; and

the second switch is for shunting the drive current when the first alternating voltage at the first secondary winding and the second alternating voltage at the second secondary winding transition from the first polarity to a second polarity.

9. The power converter of claim 8, wherein the drive circuit further includes a pulse transformer having first and secondary windings for turning on the second switch when the first alternating voltage at the first secondary winding and the second alternating voltage at the second secondary winding transition from the first polarity to the second polarity.

10. The power converter of claim 9, wherein the drive circuit further includes a differentiator circuit coupled to the pulse transformer.

11. The power converter of claim 10, wherein the differentiator circuit includes:

a capacitor connected in series with the primary winding of the pulse transformer; and

a resistor connected in parallel with the pulse transformer.

12. The power converter of claim 7, wherein:

the first synchronous rectifier includes a MOSFET; and

the second synchronous rectifier includes a MOSFET.