Apparatus and method for driving synchronous rectifier

Patent metadata

Field	Value
Publication number	US-9991807-B2
Application number	US-201414916086-A
Country	US
Kind code	B2
Filing date	May 7, 2014
Priority date	Sep 3, 2013
Publication date	Jun 5, 2018
Grant date	Jun 5, 2018

Abstract

Provided is apparatus and a method for driving synchronous rectifiers, which relate to the field of power supplies for communications. The apparatus includes: detection circuits, wherein each of the detection circuits is configured to detect drain and source voltages of one of synchronous rectifiers to obtain a detection signal for indicating a current direction in the one of the synchronous rectifiers; an isolated driving circuit, configured to generate isolated driving signals for driving the synchronous rectifiers according to the detection signals output by the detection circuits; and the synchronous rectifiers, configured to synchronously rectify input signals from a main transformer by using the isolated driving signals. The present disclosure can obtain the isolated driving signals of the synchronous rectifiers simply and effectively, and has a superior protective feature in case of shoot-through and other abnormalities.

First claim

What is claimed is:

1. Apparatus for driving synchronous rectifiers, comprising:
detection circuits, wherein each of the detection circuits are configured to detect drain and source voltages of one of the synchronous rectifiers to obtain a detection signal for indicating a current direction in the one of the synchronous rectifiers;
an isolated driving circuit configured to generate isolated driving signals for driving the synchronous rectifiers according to the detection signals output by the detection circuits; and
the synchronous rectifiers configured to synchronously rectify input signals from a main transformer by using the isolated driving signals;
wherein the apparatus comprises two synchronous rectifiers, each of the two synchronous rectifiers being connected to a secondary winding of the main transformer and one of the detection circuits respectively;
the isolated driving circuit comprises two push-pull circuits and an isolated driving transformer, wherein an input end of each of the two push-pull circuits is connected to one of the detection circuits; and a primary winding of the isolated driving transformer is connected to output ends of the two push-pull circuits, and each of two secondary windings of the isolated driving transformer is connected to a gate and source of one of the two synchronous rectifiers;
wherein each of the detection circuits comprise: a comparison circuit, wherein an input end of the comparison circuit is connected to a drain and source of the one of the synchronous rectifiers; and
an amplification circuit, wherein an input end of the amplification circuit is connected to the comparison circuit, and an output end of the amplification circuit is connected to one of the two push-pull circuits.

2. The apparatus according to claim 1 , wherein the apparatus comprises a full-bridge rectifier circuit formed by four synchronous rectifiers; input ends of the full-bridge rectifier circuit are connected to the secondary windings of the main transformer; and a synchronous rectifier, of which the source is grounded, in the two synchronous rectifiers in each input branch circuit of the full-bridge rectifier circuit is connected to one of the detection circuits.

3. The apparatus according to claim 2 , wherein the isolated driving circuit comprises two push-pull circuits and an isolated driving transformer, wherein
an input end of each of the two push-pull circuits is connected to the one of the detection circuits; and
a primary winding of the isolated driving transformer is connected to output ends of the two push-pull circuits, and each of four secondary windings of the isolated driving transformer is connected to a gate and source of the one of the synchronous rectifiers.

4. The apparatus according to claim 1 , wherein each of the comparison circuits comprises a first comparison branch circuit and a second comparison branch circuit; one end of the first comparison branch circuit and one end of the second comparison branch circuit are connected to an auxiliary power supply via a first resistor;
the first comparison branch circuit comprises:
a first triode, wherein a base and collector of the first triode are connected to the drain of the one of the synchronous rectifiers;
a first diode, wherein a cathode of the first diode is connected to an emitter of the first triode, an anode of the first diode is connected to the first resistor;
the second comparison branch circuit comprises:
a second triode, wherein a base of the second triode is connected to the source of the one of the synchronous rectifiers, a collector of the second triode is connected to the amplification circuit; and
a second diode, wherein a cathode of the second diode is connected to an emitter of the second triode, an anode of the second diode is connected to the first resistor.

5. A method for driving synchronous rectifiers, comprising:
detecting drain and source voltages of each of the synchronous rectifiers to obtain detection signals for indicating current directions in the synchronous rectifiers;
generating isolated driving signals for driving the synchronous rectifiers according to the obtained detection signals; and
synchronously rectifying input signals from a main transformer by using the isolated driving signals;
wherein obtaining the detection signals for indicating the current directions in the synchronous rectifiers comprises:
comparing the drain and source voltages of one of the synchronous rectifiers by using a comparison circuit; and
amplifying an output of the comparison circuit by using an amplification circuit to obtain the detection signal for indicating the current direction in the one of the synchronous rectifiers.

6. The method according to claim 5 , wherein generating the isolated driving signals for driving the synchronous rectifiers comprises:
outputting the detection signals to an isolated driving transformer in a push-pull way by using a push-pull circuit, in order that the isolated driving transformer generates the isolated driving signals for driving the synchronous rectifiers.

7. The apparatus according to claim 1 , wherein each of the comparison circuits comprises a first comparison branch circuit and a second comparison branch circuit; one end of the first comparison branch circuit and one end of the second comparison branch circuit are connected to an auxiliary power supply via a first resistor;
the first comparison branch circuit comprises:
a first triode, wherein a base and collector of the first triode are connected to the drain of the one of the synchronous rectifiers;
a first diode, wherein a cathode of the first diode is connected to an emitter of the first triode, an anode of the first diode is connected to the first resistor;
the second comparison branch circuit comprises:
a second triode, wherein a base of the second triode is connected to the source of the one of the synchronous rectifiers, a collector of the second triode is connected to the amplification circuit; and
a second diode, wherein a cathode of the second diode is connected to an emitter of the second triode, an anode of the second diode is connected to the first resistor.

8. The method according to claim 5 , wherein generating the isolated driving signals for driving the synchronous rectifiers comprises:
outputting the detection signals to an isolated driving transformer in a push-pull way by using a push-pull circuit, in order that the isolated driving transformer generates the isolated driving signals for driving the synchronous rectifiers.

Assignees

• Zte Corp

Inventors

• Du Fengfu
• Fan Jie
• Gao Yaoguang

Classifications

• H02M7/217 Primary

  using semiconductor devices only · CPC title

• H02M3/33592 Primary

  having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer · CPC title

• Y02B70/1475

  Cross-Sectional Technologies · mapped topic

• H02M3/33546 Primary

  with automatic control of the output voltage or current (H02M3/33561 takes precedence) · CPC title

• Y02B70/10

  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 · CPC title