CN202586786U

CN202586786U - Synchronous rectification circuit based on synchronous rectification chip low-voltage-output push-pull converter

Info

Publication number: CN202586786U
Application number: CN2012202219132U
Authority: CN
Inventors: 李遥; 孙培德; 杨刚; 叶超; 朱龙秀; 朱剑辉
Original assignee: Donghua University
Current assignee: Donghua University
Priority date: 2012-05-15
Filing date: 2012-05-15
Publication date: 2012-12-05
Anticipated expiration: 2022-05-15

Abstract

The utility model provides a synchronous rectification circuit based on a synchronous rectification chip low-voltage-output push-pull converter. The synchronous rectification circuit based on the synchronous rectification chip low-voltage-output push-pull converter comprises a controlled rectifier metal oxide semiconductor (MOS) pipe and a synchronous rectification unit, wherein a drain electrode of the controlled rectifier MOS pipe is connected with a secondary winding of a transformer. The synchronous rectification circuit based on the synchronous rectification chip low-voltage-output push-pull converter is characterized in that a detection end of the synchronous rectification unit is respectively connected with the drain electrode and a source electrode of the controlled rectifier MOS pipe, and a driving end of the synchronous rectification unit is connected with a grid electrode of the controlled rectifier MOS pipe. Compared with an existing push-pull synchronous rectification circuit, the synchronous rectification circuit based on the synchronous rectification chip low-voltage-output push-pull converter only utilizes eclectic signals of the secondary winding of the transformer, avoids damaging the original separation character of the circuit, and is high in rectification efficiency, strong in interference resistant capacity, and capable of achieving zero current turn-off.

Description

Circuit of synchronous rectification based on synchronous rectification chip low pressure output push-pull converter

Technical field

The utility model relates to a kind of synchronous rectification driving circuit of DC converter, is particularly useful for exporting the direct current push-pull converter of low-pressure high-power.

Background technology

The low-voltage, high-current isolated converter has widely always to be used.To the occasion of low-voltage, high-current, synchronous rectification can reduce conduction loss effectively, combines with suitable circuit topology, can obtain energy-efficient converter.Because the conduction voltage drop of rectifier diode is higher; Even the pressure drop of adopting the Schottky diode of low pressure drop also can produce about 0.6V; So the loss of rectifying tube is particularly outstanding, sometimes need extraly carry out air-cooledly to rectifier diode, synchronous rectification can address this problem well.

Existing circuit of synchronous rectification is a kind of circuit of synchronous rectification of recommending that is applicable to wide input voltage range.This circuit utilizes the drive signal on former limit to drive synchronous rectifier; Synchronous rectifier adopts the extremely low special power MOSFET of on state resistance; Replace rectifier diode to reduce the wastage, improve the efficient of DC/DC converter and do not have the dead band voltage that causes by Schottky barrier voltage.It is characterized in that its former limit one MOS turn-offed to the time interval that another MOS opens; Therefore one of secondary metal-oxide-semiconductor is open-minded, and another shutoff is in this two periods time intervals; The body diode that secondary turn-offs metal-oxide-semiconductor is walked in afterflow; So making full use of low resistance state MOS does not go conducting, and the rectification metal-oxide-semiconductor do not have the zero-current switching function, thereby has limited the further lifting of circuit of synchronous rectification efficient.

Summary of the invention

The purpose of the utility model provides a kind of circuit of synchronous rectification with zero-current switching function.

In order to achieve the above object; The technical scheme of the utility model has provided a kind of circuit of synchronous rectification based on synchronous rectification chip low pressure output push-pull converter; Comprise controlled rectification metal-oxide-semiconductor, the drain electrode of controlled rectification metal-oxide-semiconductor links to each other with the secondary winding of transformer, also comprises the synchronous rectification unit; It is characterized in that: the test side of synchronous rectification unit connects the drain electrode and the source electrode of controlled rectification metal-oxide-semiconductor respectively, and its drive end connects the grid of controlled rectification metal-oxide-semiconductor.

Preferably, the drain electrode of said controlled rectification metal-oxide-semiconductor links to each other with the test side of said synchronous rectification unit through the RC filter circuit.

Preferably, the secondary winding of said transformer directly is the power supply of said synchronous rectification unit through output resistance.

The utility model has the advantages that: (1) has utilized the electric signal and the synchronous rectification chip controls rectifying tube of transformer secondary, avoids destroying the original isolation characteristic of circuit.(2) when output voltage within the specific limits, can be directly give the power supply of synchronous rectification control chip through output voltage, the Transformer Winding that need not increase extra auxiliary winding or band tap is come to the synchronous rectification chip power supply.(3) the synchronous rectification control chip detects rectifying tube drain-source voltage Vds, turn-offs rectifying tube when Vds levels off to zero the time, has realized zero-current switching.(4) synchronous rectification driving duty ratio further extends, and rectification efficiency improves, thereby transducer effciency further improves.(5) drain electrode of controlled rectification metal-oxide-semiconductor connects the test side of rectification chip respectively after RC filtering, can eliminate the interference of introducing owing to parasitic parameter in switch motion of former limit and the circuit, improves the stability and the antijamming capability of system.

Description of drawings

Fig. 1 is a kind of circuit diagram of exporting the circuit of synchronous rectification of push-pull converter based on synchronous rectification chip low pressure among the embodiment;

Fig. 2 is the desirable sequential chart of Fig. 1 circuit;

Fig. 3 is the actual sequential chart of Fig. 1 circuit.

Embodiment

For making the utility model more obviously understandable, now with a preferred embodiment, and conjunction with figs. elaborates as follows.

As shown in Figure 1; The disclosed a kind of circuit of synchronous rectification based on synchronous rectification chip low pressure output push-pull converter of present embodiment comprises power transformer 5, and the former limit winding of power transformer 5 links to each other with the drain electrode of first metal-oxide-semiconductor 2, the drain electrode and the direct-current input power supplying 4 of second metal-oxide-semiconductor 3 respectively.The grid of first metal-oxide-semiconductor 2 and second metal-oxide-semiconductor 3 connects former limit and drives 1.The secondary winding of power transformer 5 links to each other with the drain electrode of the first controlled rectification metal-oxide-semiconductor 10 and the second controlled rectification metal-oxide-semiconductor 11 respectively; Link to each other with the negative pole of electric capacity 15 after the source electrode parallel connection of the first controlled rectification metal-oxide-semiconductor 10 and the second controlled rectification metal-oxide-semiconductor 11, parallel resistance 16 on electric capacity 15.

One of the first synchronous rectification chip 12 detects pin and links to each other with the drain electrode of the first controlled rectification metal-oxide-semiconductor 10 via behind resistance 8 and the RC filter circuit that electric capacity 6 reaches again; Another detects the source electrode that pin connects the first controlled rectification metal-oxide-semiconductor 10; The driving pin of the first synchronous rectification chip 12 connects the grid of the first controlled rectification metal-oxide-semiconductor 10, and the ground wire pin of the first synchronous rectification chip 12 connects the source electrode of the first controlled rectification metal-oxide-semiconductor 10.One of the second synchronous rectification chip 13 detects pin and links to each other with the drain electrode of the second controlled rectification metal-oxide-semiconductor 11 via behind resistance 9 and the RC filter circuit that electric capacity 7 reaches again; Another detects the source electrode that pin connects the second controlled rectification metal-oxide-semiconductor 11; The driving pin of the second synchronous rectification chip 13 connects the grid of the second controlled rectification metal-oxide-semiconductor 11, and the ground wire pin of the second synchronous rectification chip 13 connects the source electrode of the second controlled rectification metal-oxide-semiconductor 11.

Drain-source voltage Vds by the controlled rectification metal-oxide-semiconductor of synchronous rectification chip detection; Generation offers the control signal of controlled rectification metal-oxide-semiconductor control end; When drain-source voltage Vds arrives the first reversing valve threshold voltage, the controlled rectification metal-oxide-semiconductor of conducting, and the minimum conducting that triggers controlled rectification metal-oxide-semiconductor drives; When drain-source voltage Vds arrives the second reversing valve threshold voltage; Turn-off controlled rectification metal-oxide-semiconductor, reset synchronization rectification chip when drain-source voltage Vds reaches the 3rd forward threshold voltage begins the voltage detecting of following one-period.

The secondary winding of power transformer 5 is the first synchronous rectification chip 12 and the power supply of the second synchronous rectification chip 13 through resistance 18 and resistance 17 respectively again after via inductance 14.

Fig. 1 is a kind of embodiment of the utility model typical scenario; When this circuit of synchronous rectification is following time of ideal situation; Be the influence that does not have electromagnetic interference and parasitic parameter in the circuit, then can obtain sequential chart as shown in Figure 2, but because the interference that some the stray inductance electric capacity in switch motion of former limit and the circuit are introduced; Can the voltage detecting of synchronous rectification chip be exerted an influence, therefore at the synchronous rectification chip detects pin adding RC filter circuit.Therefore obtain actual sequential chart as shown in Figure 3.The conducting duty ratio of secondary metal-oxide-semiconductor further extends among Fig. 3; And the synchronous rectification chip power-consumption is low, and rectifier switch is realized zero-current switching, and synchronous rectification efficient improves; Improved the efficient of converter, realized that this function detects through the drain-source voltage of synchronous rectification chip and rectification metal-oxide-semiconductor.

Claims

1. circuit of synchronous rectification based on synchronous rectification chip low pressure output push-pull converter; Comprise controlled rectification metal-oxide-semiconductor; The drain electrode of controlled rectification metal-oxide-semiconductor links to each other with the secondary winding of transformer; Also comprise the synchronous rectification unit, it is characterized in that: the test side of synchronous rectification unit connects the drain electrode and the source electrode of controlled rectification metal-oxide-semiconductor respectively, and its drive end connects the grid of controlled rectification metal-oxide-semiconductor.

2. a kind of circuit of synchronous rectification based on synchronous rectification chip low pressure output push-pull converter as claimed in claim 1, it is characterized in that: the drain electrode of said controlled rectification metal-oxide-semiconductor links to each other with the test side of said synchronous rectification unit through the RC filter circuit.

3. a kind of circuit of synchronous rectification based on synchronous rectification chip low pressure output push-pull converter as claimed in claim 1 is characterized in that: the secondary winding of said transformer directly is the power supply of said synchronous rectification unit through output resistance.