Resonant gate driver

• US 6,477,065 B2
• Filed: 02/20/2001
• Issued: 11/05/2002
• Est. Priority Date: 10/31/1994
• Status: Expired due to Fees

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Parks, David B.
• Primary Examiner(s): Nguyen, Matthew
• Application Number:
  US09/788,803
• Publication Number:
  US 20020110004A1
• Time in Patent Office: 623 Days
• Field of Search: 363/16, 363/20, 363/21.01, 363/21.04, 363/21.06, 363/21.12, 363/21.14, 363/95, 363/97, 363/131
• US Class Current: 363/21.06
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• 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: H03K 2017/6875 using self-conductive, depletion FETs
• 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 power supply (500) with vertical field effect transistor synchronous rectifiers (VFET1 and VFET2) having drivers (VFET Driver1 and VFET Driver2) which provide bipolar mode of operation by diode clamping an inductor overshoot which forwards biases the gate-source junction. The rectifiers have low on resistance useful in low output voltage power supplies.

Claims

1. A dc power supply, comprising:

(a) a transformer with a primary winding and a secondary winding;

(b) a switched dc circuit connected to said primary winding;

(c) a dc output coupled to said secondary winding;

(d) a field effect transistor coupled between said secondary winding and ground; and

(e) a gate driver with an output connected to the gate of said field effect transistor, said gate driver including;

(i) first and second power supply inputs;

(ii) a first switch coupled between said first power supply input and said output;

(iii) a second switch coupled between said second power supply input and a passive overshoot circuit, said overshoot circuit coupled to said output; and

(iv) a switch input coupled to said first and second switches and synchronized with said switched dc circuit.

2. The dc power supply of claim 1, wherein:

(a) said overshoot circuit includes an inductor.

3. The dc power supply of claim 2, wherein:

(a) said overshoot circuit includes a diode in series with said inductor.

4. The dc power supply of claim 1, further comprising:

(a) a lowpass filter connected between said second winding and said dc output.

5. The dc power supply of claim 1, further comprising:

(a) a second field effect transistor coupled between said secondary winding and ground so that said dc output couples to said secondary winding between said field effect transistor and said second field effect transistor; and

(e) a second gate driver with a second output connected to the gate of said second field effect transistor, said second gate driver including;

(i) third and fourth power supply inputs;

(ii) a third switch coupled between said third power supply input and said output;

(iii) a fourth switch coupled between said fourth power supply input and a second passive overshoot circuit, said second overshoot circuit coupled to said second output; and

(iv) a second switch input coupled to said third and fourth switches and synchronized with said switched dc circuit.