CN105991048A - Synchronous rectifier control circuit and control method thereof - Google Patents

Abstract

The invention discloses a synchronous rectifier control circuit and a control method thereof, which are used for controlling power switches in a synchronous rectifier of a power converter. The synchronous rectifier control circuit comprises a signal processing unit and driving units. The signal processing unit is electrically connected with the secondary winding of a transformer. The driving units are electrically connected with the power switches and the signal processing unit. The signal processing unit senses output current of the secondary winding and determines the number of the power switches operating in a following state. When the output current is less than a first preset value, one power switch in each switch module operates in the following state; when the output current is greater than a second preset value, all the power switches operate in the following state; and when output current is greater than the first preset value and less than the second preset value, the number of the power switches operating in the following state is increased by the signal processing unit along with the increasing of output current. The invention further discloses a control method for the synchronous rectifier control circuit.

Description

Synchronous rectifier control circuit and control method thereof

Technical field

The present invention relates to a kind of ON-OFF control circuit, the synchronous rectifier of a kind of circuit of synchronous rectification Control circuit and control method thereof.

Background technology

Tradition uses the rectifier system of diode or Schottky diode because of forward conducting voltage greatly, overall losses Become the dominant loss of power supply changeover device.Mos field effect transistor has conducting resistance Low, switch time is short, input impedance is high, becomes the rectification unit that the power supply changeover device of low-voltage and high-current is first-selected Part, according to the Volume control of mos field effect transistor, thus has synchronous rectification The technology of (Synchronous Rectification, SR).

Coordinate refering to Fig. 1, for the circuit diagram of the synchronous rectifier control circuit of prior art.Synchronous rectifier Control circuit 4 is electrically connected to the secondary windings of transformator, in order to control the behaviour of the power switch of synchronous rectifier Make state.Synchronous rectifier is electrically connected to the change of power supply changeover device (for example, DC-DC power converter) Depressor T secondary windings, synchronous rectifier comprises the first switch module SR1 and second switch module SR2, the One switch module SR1 and second switch module SR2 comprise four power switch, wherein the first switching moldings respectively Block SR1 comprises power switch MOS11-MOS14, second switch group SR2 and comprises power switch MOS21-MOS24.Power switch MOS11-MOS14 in first switch module SR1 in being connected in parallel, Power switch MOS21-MOS24 in two switch module SR2 is also in being connected in parallel.More specifically, first In switch module SR1 and second switch module SR2, the grid of power switch MOS11-MOS24 all electrically connects In synchronous rectifier control circuit 4, drain electrode is all electrically connected at the secondary windings of transformation T, and source electrode all electrically connects Earth terminal.

Thereby, synchronous rectifier control circuit 4 can control the first switch module SR1 and second switch simultaneously The mode of operation of all power switch in module SR2；Such as make the first switch module SR1 and second switch All power switch MOS11-MOS24 all operationss in module SR2 are in cut-off state, or make first It is whole that all power switch MOS11-MOS24 in switch module SR1 and second switch module SR2 follow synchronization The driving signal of stream device control circuit 4 output switches over action.

The power switch MOS11-MOS24 of aforesaid synchronous rectifier possesses that control mode is simple and circuit is simple Single feature.But, after power supply changeover device starts, no matter power supply changeover device is operate within heavy duty or underloading, All power switch MOS11-MOS24 all can enter according to the driving signal of synchronous rectifier control circuit 4 output Row switching action, this makes the power supply changeover device switch cost when underloading to be effectively reduced.

Summary of the invention

The technical problem to be solved is to provide a kind of synchronous rectifier control circuit, is applied to control Synchronous rectifier in one power supply changeover device, synchronous rectifier control circuit is according to power supply changeover device secondary windings Output electric current determine that the power switch in synchronous rectifier operates in the quantity of following state, and when output electricity When stream increases, increase the quantity of the power switch operating in following state, to reduce power supply changeover device in underloading Time switch cost.

To achieve these goals, the invention provides a kind of synchronous rectifier control circuit, it is applicable to control The synchronous rectifier of power supply changeover device processed.Synchronous rectifier is electrically connected to the transformer secondary output of power supply changeover device Winding, and comprise multiple switch module；Each switch module comprises multiple power switch.

Synchronous rectifier control circuit comprises signal processing unit and multiple driver element, signal processing unit electricity It is connected to the secondary windings of transformator.Driver element is electrically connected in switch module and signal processing unit.

The output electric current of signal processing unit sensing transformer secondary output winding, and determine operation according to output electric current Quantity in the power switch of cut-off state.When exporting electric current less than first predetermined value, in switch module One of them power switch operate in following state, when export electric current more than second predetermined value time, power Switch all operates in following state, when exporting electric current between the first predetermined value and the second predetermined value, at signal Reason unit increases along with output electric current and increases the quantity of the power switch operating in following state.

In order to above-mentioned purpose is better achieved, present invention also offers the control method of a kind of synchronous rectifier, It, in order to control the mode of operation of the multiple power switch in multiple switch modules of a synchronous rectifier, synchronizes Commutator is electrically connected to the secondary windings of transformator.

The control method of synchronous rectifier comprises the steps of that (a) senses the secondary windings of this transformator Output electric current；(b) when this output electric current more than one first setting value and less than second setting value time, foundation The mode of operation of the such power switch in this output electric current control respectively this switch module, and when this output electric current When being gradually increased, the such power switch in increase respectively this switch module operates in the quantity of following state.

The method have technical effect that:

According to the output electric current of power supply changeover device secondary windings, the present invention determines that the power in synchronous rectifier is opened Close the quantity operating in following state, and when the output current increases, increase the power operating in following state The quantity of switch, to reduce the power supply changeover device switch cost when underloading.

Describe the present invention below in conjunction with the drawings and specific embodiments, but not as to the present invention's Limit.

Accompanying drawing explanation

Fig. 1 is the circuit diagram of the synchronous rectifier control circuit of prior art；

Fig. 2 is the circuit diagram of one embodiment of the invention synchronous rectifier control circuit；

Fig. 3 is output electric current and the sequential chart of on off state of the corresponding present invention；

Fig. 4 a is the circuit block diagram of the signal processing unit of first embodiment of the invention；

Fig. 4 b is the circuit block diagram of the signal processing unit of second embodiment of the invention；

Fig. 4 c is the circuit block diagram of the signal processing unit of third embodiment of the invention；

Fig. 5 a is the circuit block diagram of the driver element of first embodiment of the invention；

Fig. 5 b is the circuit block diagram of the driver element of second embodiment of the invention；

Fig. 5 c is the circuit block diagram of the driver element of third embodiment of the invention.

Wherein, reference

1 signal processing unit

10 signal processors

11 switching devices

12 pulse width modulation controllers

20 driver elements

30 master drivers

32 drivers

40 switching circuits

4 synchronous rectifier control circuits

Cntl2 the first control signal input

Cntl3 the second control signal input

Cntl4 the 3rd control signal input

Cntl_1 first controls end

Cntl_2 second controls end

Cntl_3 the 3rd controls end

Cntl_4 the 4th controls end

Drv_In_1 first drives input

Drv_In_2 second drives input

Drv_In_3 the 3rd drives input

Drv_In_4 the 4th drives input

Drv_Out_1 the first drive output

Drv_Out_2 the second drive output

Drv_Out_3 the 3rd drive output

Drv_Out_4 the 4th drive output

Drv1 first drives signal output part

Drv2 second drives signal output part

DrvI driving signal input

Drv1_Select_1-Drv2_Select_2 drives and selects end

Enable enable end

I1 the first setting value

I2 the second setting value

I_SENSE current sense end

MOS11-MOS24 power switch

MOS2_EN the first control signal outfan

MOS3_EN the second control signal outfan

MOS4_EN the 3rd control signal outfan

Out1 the first outfan

Out2 the second outfan

Out3 the 3rd outfan

Out4 the 4th outfan

SR1, SR2 switch module

SR1_MODE1-SR2_MODE2 operates mode signals outfan

SW switching control end

Sw_1_En first switchs enable end

Sw_2_En second switch enable end

Sw_3_En the 3rd switchs enable end

Sw_4_En the 4th switchs enable end

Sw_In_1 the first switch input terminal

Sw_In_2 second switch input

Sw_In_3 the 3rd switch input terminal

Sw_In_4 the 4th switch input terminal

Sw_Out_1 the first output switching terminal

Sw_Out_2 second switch outfan

Sw_Out_3 the 3rd output switching terminal

Sw_Out_4 the 4th output switching terminal

T transformator

Detailed description of the invention

Structural principle and operation principle to the present invention are described in detail below in conjunction with the accompanying drawings:

Coordinate refering to Fig. 2, for the circuit diagram of the synchronous rectifier control circuit of the embodiment of the present invention.Synchronize whole Current circuit is applicable to control a synchronous rectifier of a power supply changeover device, and synchronous rectifier is electrically connected to power supply and turns The transformator T secondary windings of parallel operation, and comprise multiple switch module SR1-SR2, each switch module SR1, SR2 comprises multiple power switch MOS11-MOS24, and power switch can such as metal oxide semiconductcor field effect Answer transistor (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET). To be illustrated, the circuit of synchronous rectification of the embodiments of the present invention is the most all to control two switches Four power switch of module are as illustrative example, so when reality is implemented, switch module and power switch Quantity can adjust according to actual requirement.The drain electrode of power switch MOS11-MOS24 is electrically connected in change The secondary windings of depressor T, source electrode then connects earth terminal.

Synchronous rectifier control circuit comprises a signal processing unit 1 and multiple driver element 20.At signal Reason unit 1 is electrically connected to the secondary windings of transformator T, in order to sense the output electric current of secondary windings；Wherein, Signal processing unit 1 can pass through current transformer (current transformer) and feel in a non contact fashion Answer the output electric current of secondary windings, or through current-sense resistor (shunt resistor) with contact side Formula obtains the output electric current of secondary windings.Signal processing unit 1 comprises a current sense end I_SENSE, many Individual drive output and multiple control signal outfan.In the present invention, signal processing unit 1 comprises two and drives Dynamic outfan and three control output ends, and the respectively first driving signal output part Drv1, the second driving Signal output part Drv2, the first control signal outfan MOS2_EN, the second control signal outfan MOS3_EN And the 3rd control signal outfan MOS4_EN.

Driver element 20 comprises driving signal input DrvI, multiple control signal input and multiple defeated Go out end, and when the quantity of control signal input is P, when the quantity of outfan is Q, meet following bar Part: P=Q-1.In invention, driver element 20 comprises three control signal inputs, and respectively first Control signal input Cntl2, the second control signal input Cntl3 and the 3rd control signal input Cntl4.Driver element 20 also comprises four outfans, and the respectively first outfan Out1, second defeated Go out to hold Out2, the 3rd outfan Out3 and the 4th outfan Out4.

First driving signal output part Drv1 of signal processing unit 1 is electrically connected to one of them driver element Driving signal input DrvI of 20, second drives signal output part Drv2 to be electrically connected to another driver element Driving signal input DrvI of 20.First control signal outfan MOS2_EN of signal processing unit 1 It is electrically connected to the first control signal input Cntl2 of driver element 20, the second control signal outfan MOS3_EN is electrically connected to the second control signal input Cntl3 of driver element 20, and the 3rd control signal is defeated Go out to hold MOS4_EN to be electrically connected to the 3rd control signal input Cntl4 of driver element 20.

First outfan Out1 of driver element 20 the most above, the second outfan Out2, 3rd outfan Out3 and the 4th outfan Out4 is electrically connected in the grid of power switch MOS11-MOS14 Pole, is positioned at the first outfan Out1 of driver element 20 of lower section, the second outfan Out2, the 3rd output End Out3 and the 4th outfan Out4 is electrically connected in the grid of power switch MOS21-MOS24.

The current sense end I_SENSE of signal processing unit 1 is electrically connected to the secondary windings of transformator T, and The output electric current of sensing secondary windings.Signal processing unit 1 according to the output electric current sensed with determine behaviour Make in the quantity of the power switch MOS11-MOS24 of cut-off state, and by the first control signal outfan MOS2_EN, the second control signal outfan MOS3_EN and the 3rd control signal outfan MOS4_EN send Corresponding controls signal to the first control signal input Cntl2 of driver element 20, the second control signal Input Cntl3 and the 3rd control signal input Cntl4, to control power switch MOS11-MOS24's Mode of operation.

The mode of operation of power switch MOS11-MOS24 comprises cut-off state and following state, at cut-off shape State, the grid of power switch MOS11-MOS24 receives pick-off signal (at this for continuous low level signal) During input, it is not turned on, for cut-off state between the source electrode of power switch MOS11-MOS24 and drain electrode；Following State, power switch MOS11-MOS24 follows the driving signal that driver element 20 sends and switches over action； Wherein, signal is driven to be made up of staggered low level signal and high levle signal.

When the output electric current of transformator T secondary windings is less than the first setting value I1 (as shown in Figure 3), with Step rectifier control circuit makes one of them power switch in switch module SR1, SR2, for example, merit Rate switch MOS11 and MOS21 operate in following state, other power switch MOS12, MOS13, MOS14, MOS22, MOS23 and MOS24 then operate in cut-off state；In other words, only power switch MOS11 and MOS21 Not operation is in cut-off state.

When the output electric current of transformator T secondary windings is more than the second setting value I2 (as shown in Figure 3), with Step rectifier control circuit makes all of power switch MOS11-MOS24 all operate in following state, and power Switch MOS11-MOS24 all follows the driving signal of driver element 20 output and switches over action；In other words, All of power switch MOS11-MOS24 all not operations are in cut-off state.Wherein, the second setting value I2 can Current value when for example, power supply changeover device works in semi-load), and the second setting value I2 is more than the first setting value I1。

When transformator T secondary windings output electric current between the first setting value I 1 and the second setting value I2 it Between, and when being gradually increased to the second setting value I2 by the first setting value I1, synchronous rectifier control circuit makes The quantity of the power switch MOS11-MOS24 operating in following state is gradually increased.In short, work as transformation The output electric current of device T secondary windings is little, operates in the number of the power switch MOS11-MOS24 of following state Amount few (namely operate in the power switch MOS11-MOS24 of cut-off state quantity many)；When secondary around The output electric current of group is big, many (namely the behaviour of the quantity of the power switch MOS11-MOS24 operating in following state The quantity of the power switch MOS11-MOS24 making in cut-off state is few)；And it is preferred that operate in and follow shape The quantity of the power switch MOS11-MOS24 of state is directly proportional to the numerical value of output electric current.Thereby, Ke Yiyou Effect ground reduces the switch cost of power switch when power supply changeover device operates in underloading.

Lower list is below coordinated to illustrate once the mode of operation of the synchronous rectifier control circuit of the present invention.

Table one is the detailed operation data of the synchronous rectifier control circuit of Fig. 2, and wherein L table exports low standard Position signal, H table output high levle signal；" end " expression power switch MOS11-MOS24 operate in cut Only state, is i.e. not turned between power switch MOS11-MOS24 source electrode and drain electrode；" follow " expression power to open Close MOS11-MOS24 and operate in following state, i.e. power switch MOS11-MOS24 follows signal processing unit The first of 1 or second drives the driving signal of signal output part Drvl, Drv2 output to switch over action.

In short, the control method of the synchronous rectifier of the present invention is first to sense the secondary windings of transformator T One output electric current, and in time exporting electric current and be more than the first setting value and be less than the second setting value, according to output electricity The mode of operation of the power switch MOS11-MOS24 in flow control switch module SR1, SR2, and when output When electric current is gradually increased, the power switch MOS11-MOS24 increased in switch module SR1, SR2 operates in The quantity of following state.

Coordinate refering to Fig. 4 a, for the block diagram of the signal processing unit of first embodiment of the invention.At signal Reason unit 1 comprise signal processor 10, signal processor 10 comprise current sense end I_SENSE, first To the 3rd control signal outfan MOS2_EN-MOS4_EN, the first driving signal output part Drv1 and second Drive signal output part Drv2, and respectively in order to as signal processing unit 1 current sense end I_SENSE, First to the 3rd control signal outfan MOS2_EN-MOS4_EN, first drive signal output part Drv1 and Second drives signal output part Drv2.

Coordinate refering to Fig. 4 b, for the block diagram of the signal processing unit of second embodiment of the invention.At signal Reason unit 1 comprises signal processor 10 and a pulse width modulation controller 12；Signal processor 10 Comprise current sense end I_SENSE and first to the 3rd control signal outfan MOS2_EN-MOS4_EN, and Defeated in order to current sense end I_SENSE and first to the 3rd control signal as signal processing unit 1 respectively Go out to hold MOS2_EN-MOS4_EN.

Pulse width modulation controller 12 comprises the first driving signal output part Drv1 and two driving signal is defeated Go out and hold Drv2, and in order to drive signal output part Drv1 and second to drive as the first of signal processing unit 1 Dynamic signal output part Drv2.

Coordinate refering to Fig. 4 c, for the block diagram of the signal processing unit of third embodiment of the invention.At signal Reason unit 1 comprises signal processor 10 and switching device 11；Signal processor 10 comprises a current sense End I_SENSE, the first to the 3rd control signal outfan MOS2_EN-MOS4_EN, an enable end Enable, One switching control end SW and multiple operation mode signals outfan SR1_MODE1-SR2_MODE2, electric current sense Survey end I_SENSE and first to the 3rd control signal outfan MOS2_EN-MOS4_EN in order at as signal Current sense end I_SENSE and first to the 3rd control signal outfan of reason unit 1 MOS2_EN-MOS4_EN。

Switching device 11 comprises one first driving signal output part Drv1, one second driving signal output part Drv2, an enable end Enable, a switching control end SW and multiple driving select end Drv1_Select_1-Drv2_Select_2, first drives signal output part Drv1 and a two driving signal Outfan Drv2 is in order to drive signal output part Drv1 and 1 second to drive as the first of signal processing unit 1 Dynamic signal output part Drv2.

The enable end Enable and switching control end SW of signal processor 10 are electrically connected in switching device The enable end Enable and switching control end SW of 11, in order to control the duty of switching device 11.Letter The operation mode signals outfan SR1_MODE1-SR2_MODE2 of number processor 10 is electrically connected in switching The driving of element 11 selects end Drv1_Select_1-Drv2_Select_2, and switching device 11 is according to operation The signal of mode signals outfan SR1_MODE1-SR2_MODE2 output is to determine power switch The mode of operation of MOS11-MOS24.

Under below coordinating, list two just includes the synchronous rectifier control of the signal processing unit of the 3rd embodiment The mode of operation of circuit processed illustrates.

Table two is for having the detailed behaviour of the synchronous rectifier control circuit of the signal processing unit shown in Fig. 4 c Make data, wherein the output of X table arbitrary signal, L table output low level signal, H table output high levle signal； " end " expression power switch MOS11-MOS24 and operate in cut-off state, i.e. power switch MOS11-MOS24 It is not turned between source electrode and drain electrode；" follow " expression power switch MOS11-MOS24 and operate in following state, I.e. power switch MOS11-MOS24 follow signal processing unit 1 the first or second drive output Drvl, The driving signal of Drv2 output switches over.

Coordinate refering to Fig. 5 a, for the circuit block diagram of the driver element of first embodiment of the invention.Driver element 20 can be made up of master driver 30 and secondary driver 32, and master driver 30 and secondary driver 32 are respectively Comprise the first driving input Drv_In_1, the second driving input Drv_In_2, the first control end Cntl_1, the second control end Cntl_2, the first drive output Drv_Out_1 and the second drive output Drv_Out_2。

First driving input Drv_In_1 of master driver 30, the second driving input Drv_In_2, with And the first driving input Drv_In_1 of secondary driver 32, second drive input Drv_In_2 to be connected Connect and in order to driving signal input DrvI as driver element 20.

Second control end Cntl_2 of master driver 30 is in order to the first control signal as driver element 20 Input Cntl2, the first control end Cntl_1 of secondary driver 32 is in order to as the of driver element 20 Two control signal input Cntl3, the second control end Cntl_2 of secondary driver 32 is in order to single as driving 3rd control signal input Cntl4 of unit 20, the first control end Cntl_1 of master driver 30 are electrically connected It is connected to an enable signal, and is maintained at the state being enabled at any time.

First drive output Drv_Out_1 of master driver 30 and the second drive output Drv_Out_2 Respectively in order to as the first outfan Out1 of driver element 20 and the second outfan Out2, secondary driver First drive output Drv_Out_1 of 32 and the second drive output Drv_Out_2 are respectively in order to conduct 3rd outfan Out3 of driver element 20 and the 4th outfan Out4.

Coordinate refering to Fig. 5 b, for the circuit block diagram of the driver element of second embodiment of the invention.Driver element 20 can be made up of master driver 30 and secondary driver 32；Master driver 30 and secondary driver 32 are respectively Comprise the first driving input Drv_In_1 and the first drive output Drv_Out_1.

Secondary driver 32 also comprise the second driving input Drv_In_2, the 3rd drive input Drv_In_3, 4th drives input Drv_In_4, the first control end Cntl_1, the second control end Cntl_2, the 3rd control End Cntl_3 processed, the 4th control end Cntl_4, the second drive output Drv_Out_2, the 3rd drive defeated Go out to hold Drv_Out_3 and the 4th drive output Drv_Out_4.

First driving input Drv_In_1 of master driver 30, and the first driving of secondary driver 32 Input Drv_In_1, the second driving input Drv_In_2, the 3rd driving input Drv_In_3 are connected Connect and in order to the driving input Drv1 as driver element 20.

First control end Cntl_1 of secondary driver 32, the second control end Cntl_2 and the 3rd control end Cntl_3 is respectively in order to believe as the first control signal input Cntl2 of driver element 20, the second control Number input Cntl3 and the 3rd control signal input Cntl4.

First defeated in order to as driver element 20 of first drive output Drv_Out_1 of master driver 30 Go out and hold Out1, the first drive output Drv_Out_1 of secondary driver 32, the second drive output Drv_Out_2 and the 3rd drive output Drv_Out_3 second defeated in order to as driver element 20 respectively Go out to hold Out2, the 3rd outfan Out3 and the 4th outfan Out4.

Coordinate refering to Fig. 5 c, for the circuit block diagram of the driver element of third embodiment of the invention.Driver element 20 can be made up of master driver 30 and switching circuit 40；Master driver 30 comprises the first driving input Drv_In_1, the second driving input Drv_In_2, the 3rd driving input Drv_In_3, the 4th driving Input Drv_In_4, the first drive output Drv_Out_1, the second drive output Drv_Out_2, 3rd drive output Drv_Out_3 and the 4th drive output Drv_Out_4.

First drives input Drv_In_1, the second driving input Drv_In_2, the 3rd driving input Drv_In_3, the 4th driving input Drv_In_4 are connected and believe in order to the driving as driver element 20 Number input DrvI.

Switching circuit 40 comprise the first switch input terminal Sw_In_1, second switch input Sw_In_2, Three switch input terminal Sw_In_3, the 4th switch input terminal Sw_In_4, first switch enable end Sw_1_En, Second switch enable end Sw_2_En, the 3rd switch enable end Sw_3_En, the 4th switch enable end Sw_4_En, First output switching terminal Sw_Out_1, second switch outfan Sw_Out_2, the 3rd output switching terminal Sw_Out_3 and the 4th output switching terminal Sw_Out_4.

First switch input terminal Sw_In_1, second switch input Sw_In_2, the 3rd switch input terminal Sw_In_3 and the 4th switch input terminal Sw_In_4 be electrically connected in the first drive output Drv_Out_1, Second drive output Drv_Out_2, the 3rd drive output Drv_Out_3 and the 4th drive output Drv_Out_4。

First switch enable end Sw_1_En is electrically connected to an enable signal, and is maintained at the shape being enabled at any time State；Second switch enable end Sw_2_En, the 3rd switch enable end Sw_3_En and the 4th switch enable end Sw_4_En is respectively in order to believe as the first control signal input Cntl2 of driver element 20, the second control Number input Cntl3 and the 3rd control signal input Cntl4.

First output switching terminal Sw_Out_1, second switch outfan Sw_Out_2, the 3rd output switching terminal Sw_Out_3 and the 4th output switching terminal Sw_Out_4 is in order to the first outfan as driver element 20 Out1, the second outfan Out2, the 3rd outfan Out3 and the 4th outfan Out4.

Fig. 5 a to Fig. 5 c is shown as and drives module 20 to be available for and the either signal process shown in Fig. 4 a to Fig. 4 c The synchronous rectifier control circuit of the unit 1 matched combined present invention, its line connection is same as above, Do not repeat them here；And the synchronous rectifier control circuit of any one combination can control in switch module The duty (cut-off state as previously described and following state) of each power switch, effectively to drop The low synchronous rectifier switch cost when underloading.

Certainly, the present invention also can have other various embodiments, without departing substantially from present invention spirit and the feelings of essence thereof Under condition, those of ordinary skill in the art work as can make various corresponding change and deformation according to the present invention, but These change accordingly and deform the protection domain that all should belong to appended claims of the invention.

Claims (10)

1. a synchronous rectifier control circuit, it is adaptable to control a synchronous rectifier of a power supply changeover device, This synchronous rectifier is electrically connected to the secondary windings of a transformator of this power supply changeover device and comprises multiple switch Module, respectively this switch module comprises multiple power switch, it is characterised in that this synchronous rectifier control circuit Comprise:

One signal processing unit, is electrically connected to the secondary windings of this transformator, and this signal processing unit sensing should One output electric current of the secondary windings of transformator, and determine operating in of such power switch in this output electric current The quantity of following state；And

Multiple driving modules, are electrically connected in the plurality of switch module and this signal processing unit,

Wherein, when this output electric current is less than first predetermined value, one of them in the plurality of switch module Power switch operates in following state, and when this output electric current is more than second predetermined value, the plurality of power is opened Close and all operate in following state, when this output electric current is between this first predetermined value and this second predetermined value, should Signal processing unit increases along with this output electric current and increases the quantity of the power switch operating in following state.

2. synchronous rectifier control circuit as claimed in claim 1, it is characterised in that this signal processing Unit comprises a current sense end, multiple driving signal output part and multiple control signal outfan, this electric current Sensing end is electrically connected to the secondary windings of this transformator, respectively this driver element comprise a driving signal input, Multiple control signal inputs and multiple outfan, the plurality of driving signal output part of this signal processing unit It is electrically connected to the plurality of driving signal input of the plurality of driver element, this signal processing unit the plurality of Control signal outfan is electrically connected to this control signal input of the plurality of driver element, respectively this driver element The plurality of outfan be electrically connected in one of them power switch.

3. synchronous rectifier control circuit as claimed in claim 2, it is characterised in that respectively this driving list The quantity of the plurality of control signal input of unit is P, the respectively quantity of the plurality of outfan of this driver element For Q, it meets following condition:

P=Q-1.

4. synchronous rectifier control circuit as claimed in claim 2, it is characterised in that this signal processing Unit comprises a signal processor and a pulse width modulation controller, and this signal processor comprises this electric current sense Surveying end and the plurality of control signal outfan, it is defeated that this pulse width modulation controller comprises the plurality of driving signal Go out end.

5. synchronous rectifier control circuit as claimed in claim 2, it is characterised in that this signal processing Unit comprises a signal processor and a switching device, and this signal processor comprises this current sense end, these are many Individual control signal outfan, an enable end, a switching control end and multiple operation mode signals outfan, should Switch unit comprises the plurality of driving signal output part, an enable end, a switching control end and multiple driving choosing Selecting end, this enable end of this signal processor and this switching control end are electrically connected being somebody's turn to do in this switching device Enable end and switching control end, the plurality of operation mode signals outfan of this signal processor is electrically connected The plurality of driving in this switch unit selects end.

6. the synchronous rectifier control circuit as described in claim 4 or 5, it is characterised in that this driving Unit comprises a master driver and secondary driver, this master driver and this driver and comprises one first respectively and drive Dynamic input, one second drive input, one first control end, one second control end, one first drive defeated Going out end and one second drive output, this of this master driver and this driver first drives input and the Two drive input to be connected and in order to this driving signal input as this driver element, this master driver This second control end in order to the first control signal input as this driver element, this driver should First controls end in order to this second control signal input as this driver element, this driver this Two control end in order to the 3rd control signal input as this driver element.

7. the synchronous rectifier control circuit as described in claim 4 or 5, it is characterised in that this driving Unit comprises a master driver and secondary driver, and this master driver comprises one first driving input and one first Drive output, this driver comprises one first driving input, second drives input, one the 3rd drives Dynamic input, one the 4th drive input, one first control end, one second control end, one the 3rd control end, One the 4th control end, one first drive output, one second drive output, one the 3rd drive output and One the 4th drive output, this master driver this first drive input, this driver this first drive Dynamic input, this second driving input and the 3rd drive input to be connected and in order to as this driving list This driving signal input of unit, this first control end of this driver, this second control end and the 3rd Control end defeated in order to this first control signal input, this second control signal as this driver element respectively Enter end and the 3rd control signal input.

8. the synchronous rectifier control circuit as described in claim 4 or 5, it is characterised in that this driving Unit comprises a master driver and a switching circuit, this master driver comprise one first driving input, one the Two drive inputs, one the 3rd drive input, one the 4th drive input, one first drive output, One second drive output, one the 3rd drive output and one the 4th drive output, this first driving input End, this second drive input, the 3rd drive input and the 4th drive input be connected and in order to As this driving signal input of this driver element, this switching circuit comprise one first switch input terminal, one Second switch input, one the 3rd switch input terminal, one the 4th switch input terminal, one first switch enable end, One second switch enable end, one the 3rd switch enable end, one the 4th switch enable end, one first switch output End, a second switch outfan, one the 3rd output switching terminal and one the 4th output switching terminal, this switching circuit This first to fourth switch input terminal be electrically connected in this master driver this first to fourth drive defeated Go out end, this second to the 4th switch enable end of this switching circuit respectively in order to as this driver element this Two to the 4th control signal inputs, this first to fourth output switching terminal of this switching circuit is in order to as this This first to fourth outfan of driver element.

9. synchronous rectifier control circuit as claimed in claim 1, it is characterised in that the plurality of operation The quantity of the plurality of power switch in following state is directly proportional to the size of this output electric current.

10. a control method for synchronous rectifier, in order to control multiple switch modules of a synchronous rectifier In the mode of operation of multiple power switch, this synchronous rectifier is electrically connected to the secondary windings of a transformator, The control method of this synchronous rectifier comprises the steps of

A () senses an output electric current of the secondary windings of this transformator；

(b) when this output electric current more than one first setting value and less than second setting value time, according to this output The mode of operation of the plurality of power switch in electric current control respectively this switch module, and work as this output electric current gradually During increase, the plurality of power switch in increase respectively this switch module operates in the quantity of following state.