CN106100379A - Synchronous rectifying controller - Google Patents

Abstract

The invention discloses synchronous rectifying controller, temperature-compensation circuit is connected with the A end of the B end opening comparator and shutoff comparator, and temperature-compensation circuit receives threshold value V_ref, output is opened and is compensated threshold value V_{ref_on_com}Threshold value V is compensated with turning off_{ref_off_com}To turning off comparator, open comparator A end and receive detection magnitude of voltage V_DET, opening comparator will detection magnitude of voltage V_DETThreshold value V is compensated with opening_{ref_on_com}Compare, open comparator and generate unlatching signal SR_on and export to drive circuit, turn off comparator B end and receive detection magnitude of voltage V_DET, turning off comparator will detection magnitude of voltage V_DETThreshold value V is compensated with turning off_{ref_off_com}Compare, turn off comparator and generate cut-off signals SR_off and export to drive circuit, generate drive voltage signal V_{sr_g}, control the switch of switch metal-oxide-semiconductor N2, it is achieved accurately switch.

Description

Synchronous rectifying controller

Technical field

The present invention relates to a kind of synchronous rectifying controller, belong to switch power technology field.

Background technology

At present, inverse-excitation type switch power-supply system owing to having that circuit is simple, input and output voltage isolation, low cost, volume The advantage such as little and be widely used, but when exporting electric current and being relatively low compared with big, output voltage, tradition inverse-excitation type switch power-supply Secondary commutation diode on-state loss and reverse recovery loss in system are big, inefficient, therefore use synchronous rectification, The switch metal-oxide-semiconductor using on-state resistance extremely low replaces commutation diode, it is possible to improve the conversion effect of whole changer well Rate.The circuit of existing synchronous rectifying controller on-off mode is as it is shown in figure 1, unlatching comparator 602 will be from synchronous rectifying controller The detection magnitude of voltage V that the VDET end of 600 obtains_DETWith unlatching threshold value V_{ref_on}Compare, as detection magnitude of voltage V_DETReach to open threshold value V_{ref_on}Time, open comparator 602 and send unlatching signal SR_on and export to drive circuit 604.Turning off comparator 603 will detection Magnitude of voltage V_DETWith shutoff threshold value V_{ref_off}Compare, as detection magnitude of voltage V_DETReach to turn off threshold value V_{ref_off}Time, turn off comparator 603 send cut-off signals SR_off and export to drive circuit 604.Finally by drive circuit 604 receive unlatching signal SR_on and Cut-off signals SR_off generates drive voltage signal V_{sr_g}And it is transferred to the GATE end of synchronous rectifying controller 600, control switch The switch of metal-oxide-semiconductor N2.Find out from the graph of a relation of the switch metal-oxide-semiconductor body diode conduction voltage drop shown in Fig. 2 with junction temperature, switch MOS The body diode conduction voltage drop V of pipe_SDNegative correlativing relation is become with junction temperature.From prior art opening ways lower body two pole shown in Fig. 3 The graph of a relation of pipe conduction voltage drop and the relative value of unlatching threshold value and junction temperature is found out, when the temperature increases, if directly using unlatching Threshold value V_{ref_on}It is used as the condition judging to open, can be because of the setting of the unlatching threshold value conducting more than the body diode D2 after changing Pressure drop V_SDAnd the relative value that cannot open switch metal-oxide-semiconductor N2, i.e. body diode conduction voltage drop and unlatching threshold value has temperature characterisitic, The change understanding temperature can affect the accurate unlatching of switch metal-oxide-semiconductor.From conducting resistance and the junction temperature of the switch metal-oxide-semiconductor shown in Fig. 4 Graph of a relation understand, switch metal-oxide-semiconductor conducting resistance R_ds(on)Positive correlation is become with junction temperature.Close from the prior art shown in Fig. 5 Under disconnected mode, shutoff threshold current is found out with the graph of a relation of junction temperature, when the temperature increases, turns off threshold value if directly used V_{ref_off}It is used as the condition judging to turn off, corresponding shutoff threshold current I_sec(off)Can diminish, i.e. turn off threshold current I_sec(off)There is temperature characterisitic, it is known that the change of temperature can affect the accurate shutoff of switch metal-oxide-semiconductor.

Summary of the invention

It is an object of the invention to the deficiency overcoming prior art to exist, it is provided that one have be switched on and off threshold temperature mend Repay the synchronous rectifying controller of circuit.

The purpose of the present invention is achieved through the following technical solutions:

Synchronous rectifying controller, feature is: includes temperature-compensation circuit, opens comparator and turn off comparator, described temperature Degree compensates circuit and is connected with the A end of the B end opening comparator and shutoff comparator, and temperature-compensation circuit receives threshold value V_ref, temperature Compensate circuit output and open compensation threshold value V_{ref_on_com}To opening comparator, output turns off and compensates threshold value V_{ref_off_com}To turning off ratio Relatively device；

The A end of described unlatching comparator receives detection magnitude of voltage V from the VDET end of synchronous rectifying controller_DET, unlatching is compared Device will detection magnitude of voltage V_DETThreshold value V is compensated with opening_{ref_on_com}Compare, as detection magnitude of voltage V_DETReach to open and compensate threshold value V_{ref_on_com}Time, open comparator and generate unlatching signal SR_on and export to drive circuit；

The B end of described shutoff comparator receives detection magnitude of voltage V from the VDET end of synchronous rectifying controller_DET, shutoff is compared Device will detection magnitude of voltage V_DETThreshold value V is compensated with turning off_{ref_off_com}Compare, as detection magnitude of voltage V_DETReach to turn off and compensate threshold value V_{ref_off_com}Time, turn off comparator and generate cut-off signals SR_off and export to drive circuit；

Described drive circuit receives opens signal SR_on and cut-off signals SR_off generation drive voltage signal V_{sr_g}And pass Transport to the GATE end of synchronous rectifying controller, control the switch of switch metal-oxide-semiconductor.

Further, above-mentioned synchronous rectifying controller, wherein, and open stage, when temperature raises, the body of switch metal-oxide-semiconductor The conduction voltage drop V of diode_SDRaise with temperature and diminish；If it is unchanged to open threshold value, because opening the setting of threshold value more than changing The conduction voltage drop V of the body diode after change_SDAnd switch metal-oxide-semiconductor cannot be opened；Threshold value is opened in temperature-compensation circuit regulation, by adjusting After joint, open and compensate threshold value V_{ref_on_com}Suitably reduce when temperature raises, the amplitude reduced by regulation, open when being held open Close the body diode conduction voltage drop of metal-oxide-semiconductor and open the relative value of threshold value not with temperature significant change, it is ensured that the standard of switch metal-oxide-semiconductor Really open.

Further, above-mentioned synchronous rectifying controller, wherein, and off-phases, when temperature raises, switch metal-oxide-semiconductor Conducting resistance R_ds(on)Raise with temperature and become big, if it is unchanged to turn off threshold value, turn off threshold current I_sec(off)Liter with temperature High and reduce, turn off threshold current I_sec(off)The current value of switch metal-oxide-semiconductor is flow through when being off；Temperature-compensation circuit regulation turns off Threshold value, after regulation, turns off and compensates threshold value V_{ref_off_com}Keep and temperature raises, the amplitude raised by regulation simultaneously, Threshold current I is turned off when being held off eventually_sec(off)Not with temperature significant change, it is ensured that the accurate shutoff of switch metal-oxide-semiconductor.

Further, above-mentioned synchronous rectifying controller, wherein, described temperature-compensation circuit includes the first operation amplifier Device, the first PMOS, the first electric capacity, the first resistance, the second resistance, the 3rd resistance, the 4th resistance and the 5th resistance, described first The outfan of operational amplifier connects the first PMOS and the first electric capacity, and the V+ end of the first operational amplifier connects temperature-compensating electricity The input IN on road, the V-end of the first operational amplifier is connected to the second resistance and the 3rd resistance；

Described first PMOS is connected with power voltage terminal, the first resistance and the second resistance；

Described 3rd resistance, the 4th resistance, the 5th resistance are the most connected in order；

Described 5th resistance connects with ground end.

Yet further, above-mentioned synchronous rectifying controller, wherein, between described 3rd resistance and the 4th resistance, temperature is set Degree compensates the first outfan OUT1 of circuit.

Yet further, above-mentioned synchronous rectifying controller, wherein, between described 4th resistance and the 5th resistance, temperature is set Degree compensates the second outfan OUT2 of circuit.

Yet further, above-mentioned synchronous rectifying controller, wherein, the input IN of temperature-compensation circuit, the first output The magnitude of voltage of end OUT1 and the second outfan OUT2 is respectively V_IN、V_OUT1、V_OUT2, then the computing formula of the offset obtained is:

$V_{OUT1}=V_{IN}*(1-\frac{R3}{R3+R4+R5})$

$V_{OUT2}=V_{IN}*\frac{R5}{R3+R4+R5}$

The temperature coefficient value of resistance is normal number or negative constant so that output voltage V_OUT1、V_OUT2For positive temperature characterisitic or negative Temperature characterisitic；R3, R5 are positive temperature coefficient, and R4 is negative temperature coefficient；

For temperature-compensation circuit, input IN receives threshold value V_ref, the first outfan OUT1 output is opened and is compensated threshold value V_{ref_on_com}, the second outfan OUT2 output turns off and compensates threshold value V_{ref_off_com}；

For open stage, the unlatching using temperature-compensation circuit to generate compensates threshold value V_{ref_on_com}As judging unlatching Condition, i.e. when

V_DET=V_{ref_on_com}

Time meet unlocking condition, the computing formula of body diode conduction voltage drop and the relative value that opens threshold value is:

$V_{ref\_on\_com}=V_{ref}*(1-\frac{R3}{R3+R4+R5})$

$\frac{V_{SD}}{V_{ref\_on\_com}}=\frac{V_{SD}}{V_{ref}*(1-\frac{R3}{R3+R4+R5})}$

Wherein, threshold value V_refIt is a standard voltage value, for zero-temperature coefficient, V_SDFor switching the conducting of metal-oxide-semiconductor N2 body diode Pressure drop；

When the temperature increases, the resistance of R3, R5 becomes big, and the resistance of R4 diminishes, by the setting to temperature coefficient so thatBecome big, V_{ref_on_com}Diminishing, the unlatching the most now exported compensates threshold value V_{ref_on_com}For negative temperature characteristic；

For off-phases, the shutoff using temperature-compensation circuit to generate compensates threshold value V_{ref_off_com}As judging shutoff Condition, i.e. when

V_DET=V_{ref_off_com}

Time meet turn-off criterion, turn off threshold current I_sec(off)Computing formula be:

$V_{ref\_off\_com}=V_{ref}*\frac{R5}{R3+R4+R5}$

$I_{\sec \left(off\right)}=\frac{V_{ref\_off\_com}}{R_{ds\left(on\right)}}=\frac{V_{ref}*\frac{R5}{R3+R4+R5}}{R_{ds\left(on\right)}}$

Wherein, threshold value V_refIt is a standard voltage value, for zero-temperature coefficient, R_ds(on)For switching the conducting resistance of metal-oxide-semiconductor N2；

When the temperature increases, the resistance of R3, R5 becomes big, and the resistance of R4 diminishes, by the setting to temperature coefficient so thatBecome big, V_{ref_off_com}Becoming big, the shutoff i.e. exported compensates threshold value V_{ref_off_com}For positive temperature characterisitic；

When temperature raises, switch metal-oxide-semiconductor body diode conduction voltage drop diminishes, and opens and compensates threshold value V_{ref_on_com}Diminish, When being held open eventually, the relative value of body diode conduction voltage drop and unlatching threshold value is not with temperature significant change, it is ensured that switch metal-oxide-semiconductor Accurate unlatching.

Yet further, above-mentioned synchronous rectifying controller, wherein, threshold value V_refIt it is a standard voltage value.

Yet further, above-mentioned synchronous rectifying controller, wherein, it is applied in inverse-excitation type switch power-supply system.

Substantive distinguishing features and significantly progress that technical solution of the present invention is prominent are mainly reflected in:

The present invention can open threshold value along with the change of temperature regulates and turn off threshold value, weakens synchronous rectification switch metal-oxide-semiconductor Switch is acted upon by temperature changes, and when the temperature is changed, opens threshold temperature and compensates circuit along with the change regulation unlatching of temperature Threshold value and shutoff threshold value, can realize switching the accurate switch of metal-oxide-semiconductor after regulation.

Accompanying drawing explanation

Fig. 1: the electrical block diagram of background technology synchronous rectifying controller on-off mode；

Fig. 2: switch metal-oxide-semiconductor body diode conduction voltage drop and the graph of a relation of junction temperature；

The relative value of Fig. 3: background technology opening ways lower body N and unlatching threshold value and the relation of junction temperature Figure；

Fig. 4: switch metal-oxide-semiconductor conducting resistance and the graph of a relation of junction temperature；

Fig. 5: turn off the graph of a relation of threshold current and junction temperature under background technology shutoff mode；

The electrical block diagram of Fig. 6: the present invention；

The schematic diagram of the temperature-compensation circuit of Fig. 7: the present invention；

The relative value of the body diode conduction voltage drop of Fig. 8: the present invention and unlatching threshold value and the graph of a relation of junction temperature；

The graph of a relation turning off threshold current and junction temperature of Fig. 9: the present invention.

Figure 10: the work wave schematic diagram under background technology on-off mode；

The work wave schematic diagram of Figure 11: the present invention.

Detailed description of the invention

The present invention arranges and is switched on and off threshold temperature compensation circuit, can regulate unlatching threshold value and pass according to temperature difference Disconnected threshold value.

As shown in Figure 6, synchronous rectifying controller 600, including temperature-compensation circuit 601, open comparator 602 and turn off ratio Relatively device 603, temperature-compensation circuit 601 is connected with the A end of the B end opening comparator 602 and shutoff comparator 603, temperature-compensating Circuit 601 receives threshold value V_ref, threshold value V_refBeing a standard voltage value, output is opened and is compensated threshold value V_{ref_on_com}To opening comparator 602, output turns off and compensates threshold value V_{ref_off_com}To turning off comparator 603.

The A end opening comparator 602 receives detection magnitude of voltage V from the VDET end of synchronous rectifying controller 600_DET, open ratio Relatively device 602 will detection magnitude of voltage V_DETThreshold value V is compensated with opening_{ref_on_com}Compare, as detection magnitude of voltage V_DETReach to open and mend Repay threshold value V_{ref_on_com}Time, open comparator 602 and generate unlatching signal SR_on and export to drive circuit 604.

The B end turning off comparator 603 receives detection magnitude of voltage V from the VDET end of synchronous rectifying controller 600_DET, turn off ratio Relatively device 603 will detection magnitude of voltage V_DETThreshold value V is compensated with turning off_{ref_off_com}Compare, as detection magnitude of voltage V_DETReach to turn off and mend Repay threshold value V_{ref_off_com}Time, turn off comparator 603 and generate cut-off signals SR_off and export to drive circuit 604.

Drive circuit 604 receives opens signal SR_on and cut-off signals SR_off generation drive voltage signal V_{sr_g}And pass It is passed to the GATE end of synchronous rectifying controller 600, controls the switch of switch metal-oxide-semiconductor N2.

During unlatching, when temperature raises, the conduction voltage drop V of the body diode D2 of switch metal-oxide-semiconductor N2_SDRaise with temperature and become Little.If unlatching threshold value is unchanged, can be because opening the conduction voltage drop V arranging the body diode D2 after being more than change of threshold value_SDAnd Cannot open switch metal-oxide-semiconductor N2, temperature-compensation circuit 601 is in order to regulate unlatching threshold value, after regulation, opens and compensates threshold value V_{ref_on_com}Suitably reduce when temperature raises, the amplitude reduced by regulation, body diode conducting pressure when being finally held open The relative value of fall and unlatching threshold value is not with temperature significant change, it is ensured that the accurate unlatching of switch metal-oxide-semiconductor；

Threshold current I is turned off during shutoff_sec(off)It is shown below:

$I_{\sec \left(off\right)}=\frac{V_{ref\_off\_com}}{R_{ds\left(on\right)}}$

Wherein, R_ds(on)For switching the conducting resistance of metal-oxide-semiconductor N2.

When temperature raises, R_ds(on)Raising with temperature and become big, compensating threshold value V if turned off_{ref_off_com}Unchanged, close Disconnected threshold current I_sec(off)Reducing with the rising of temperature, temperature-compensation circuit 601 is in order to regulate shutoff threshold value, by regulation After, turn off and compensate threshold value V_{ref_off_com}Keep and temperature raises, the amplitude raised by regulation simultaneously, close when being finally held off Disconnected threshold current I_sec(off)Not with temperature significant change, it is ensured that the accurate shutoff of switch metal-oxide-semiconductor.

As it is shown in fig. 7, temperature-compensation circuit 601 includes first operational amplifier A the 1, first PMOS P1, the first electric capacity C1, the first resistance R1, the second resistance R2, the 3rd resistance R3, the 4th resistance R4 and the 5th resistance R5, the first operational amplifier A 1 Output connects the first PMOS P1 and the first electric capacity C1, and the V+ end of the first operational amplifier A 1 connects IN end, the first operation amplifier The V-end of device A1 connects the second resistance R2 and the 3rd resistance R3.

First PMOS P1 is connected with power voltage terminal VCC, the first resistance R1 and the second resistance R2.

3rd resistance R3 and the 4th resistance R4 and the 5th resistance R5 is connected in order.

5th resistance R5 connects with ground end；

First outfan OUT1 of temperature-compensation circuit 601 is set between the 3rd resistance R3 and the 4th resistance R4.

Second outfan OUT2 of temperature-compensation circuit 601 is set between the 4th resistance R4 and the 5th resistance R5.

The principle Analysis of temperature-compensation circuit 601: by Fig. 2, Fig. 3 known switch metal-oxide-semiconductor body diode conduction voltage drop Negative correlativing relation is become with junction temperature, if temperature to be accomplished raises, corresponding body diode conduction voltage drop and the phase of unlatching threshold value Will not significant change to value, it is desirable to open and compensate threshold value V_{ref_on_com}For negative temperature characteristic；And by Fig. 4, Fig. 5 known switch MOS Pipe conducting resistance becomes positive correlation with junction temperature, if temperature to be accomplished raises, will make the shutoff threshold current of correspondence I_sec(off)Will not significant change, it is desirable to turn off and compensate threshold value V_{ref_off_com}For positive temperature characterisitic.

The magnitude of voltage of the input IN of temperature-compensation circuit 601, the first outfan OUT1 and the second outfan OUT2 is respectively For V_IN、V_OUT1、V_OUT2, then the computing formula of the offset obtained is:

$V_{OUT1}=V_{IN}*(1-\frac{R3}{R3+R4+R5})$

$V_{OUT2}=V_{IN}*\frac{R5}{R3+R4+R5}$

The temperature coefficient value of resistance is set to normal number or negative constant so that output voltage V_OUT1、V_OUT2For positive temperature characterisitic Or negative temperature characteristic.R3, R5 are positive temperature coefficient herein, and R4 is negative temperature coefficient.

For temperature-compensation circuit 601, IN end receives threshold value V_ref, the output of OUT1 end is opened and is compensated threshold value V_{ref_on_com}, The output of OUT2 end turns off and compensates threshold value V_{ref_off_com}。

For open stage, the unlatching using temperature-compensation circuit 601 to generate compensates threshold value V_{ref_on_com}As judging to open The condition opened, i.e. when

V_DET=V_{ref_on_com}

Time meet unlocking condition, the computing formula of body diode D2 conduction voltage drop and the relative value that opens threshold value is as follows:

$V_{ref\_on\_com}=V_{ref}*(1-\frac{R3}{R3+R4+R5})$

$\frac{V_{SD}}{V_{ref\_on\_com}}=\frac{V_{SD}}{V_{ref}*(1-\frac{R3}{R3+R4+R5})}$

Wherein, threshold value V_refIt is a standard voltage value, for zero-temperature coefficient, V_SDFor switching the conducting of metal-oxide-semiconductor N2 body diode Pressure drop.

When the temperature increases, the resistance of R3, R5 becomes big, and the resistance of R4 diminishes, and by the setting to temperature coefficient, can make ?Become big, V_{ref_on_com}Diminishing, the unlatching the most now exported compensates threshold value V_{ref_on_com}For negative temperature characteristic, Negative correlativing relation is become with junction temperature by Fig. 2 known switch metal-oxide-semiconductor body diode conduction voltage drop, the most when the temperature increases, corresponding body The relative value of diode D2 conduction voltage drop and unlatching threshold value will not significant change.

For off-phases, the shutoff using temperature-compensation circuit 601 to generate compensates threshold value V_{ref_off_com}As judging to close Disconnected condition, i.e. when

V_DET=V_{ref_off_com}

Time meet turn-off criterion, turn off threshold current I_sec(off)Computing formula as follows:

$V_{ref\_off\_com}=V_{ref}*\frac{R5}{R3+R4+R5}$

$I_{\sec \left(off\right)}=\frac{V_{ref\_off\_com}}{R_{ds\left(on\right)}}=\frac{V_{ref}*\frac{R5}{R3+R4+R5}}{R_{ds\left(on\right)}}$

Wherein, threshold value V_refIt is a standard voltage value, for zero-temperature coefficient, R_ds(on)For switching the conducting resistance of metal-oxide-semiconductor N2.

When the temperature increases, the resistance of R3, R5 becomes big, and the resistance of R4 diminishes, and by the setting to temperature coefficient, can make ?Become big, V_{ref_off_com}Becoming big, the shutoff the most now exported compensates threshold value V_{ref_off_com}Special for positive temperature Property, Fig. 4 known switch metal-oxide-semiconductor conducting resistance become positive correlation, the most when the temperature increases, corresponding shutoff threshold value with junction temperature Electric current I_sec(off)Will not significant change.

Fig. 8 is the body diode conduction voltage drop of the present invention and opens the relative value of threshold value and the graph of a relation of junction temperature, temperature liter Gao Shi, switch metal-oxide-semiconductor body diode D2 conduction voltage drop diminishes, and opens and compensates threshold value V_{ref_on_com}Diminish, when being finally held open The relative value of body diode D2 conduction voltage drop and unlatching threshold value is not with temperature significant change, it is ensured that the accurate unlatching of switch metal-oxide-semiconductor.

Fig. 9 is the graph of a relation turning off threshold current and junction temperature of the present invention, when temperature raises, R_ds(on)Become big, turn off and compensate Threshold value V_{ref_off_com}Become big, when being finally held off, turn off threshold current I_sec(off)Not with temperature significant change, it is ensured that switch The accurate shutoff of metal-oxide-semiconductor.

The temperature-compensation circuit of the visible present invention can weaken the synchronous rectification switch metal-oxide-semiconductor switch shadow by variations in temperature Ring.The temperature-compensation circuit of the present invention can be switched on and off threshold value along with the change of temperature regulates, and can realize split after regulation Close the accurate switch of metal-oxide-semiconductor.

Open and compensate threshold value V_{ref_on_com}Threshold value V is compensated with turning off_{ref_off_com}Actual temp characteristic, can offset detection voltage Value V_DETTemperature characterisitic.Can be applicable in inverse-excitation type switch power-supply system, but be not limited to inverse-excitation type switch power-supply system.

Figure 10 is the work wave schematic diagram under background technology on-off mode, V_DETWaveform sets forth temperature rising, temperature The waveform that degree is corresponding when normally reducing with temperature, for open stage, when the temperature increases, opens threshold value if directly used V_{ref_on}It is used as the condition judging to open, corresponding body diode conduction voltage drop and unlatching threshold value V_{ref_on}Relative value's relatively temperature Can diminish time normal.When the temperature decreases, corresponding body diode conduction voltage drop and unlatching threshold value V_{ref_on}Relative value's relatively temperature Can become big time normal, it is seen that the change of temperature can affect the accurate unlatching of switch metal-oxide-semiconductor；For off-phases, when temperature raises Time, turn off threshold value V if directly used_{ref_off}It is used as the condition judging to turn off, I_secThe shutoff threshold current that waveform is corresponding I_sec(off)Can diminish time normal compared with temperature, the drop point position of GATE waveform can be delayed time normal compared with temperature.When the temperature decreases, I_secThe shutoff threshold current I that waveform is corresponding_sec(off)Can become big time normal compared with temperature, the drop point position relatively temperature of GATE waveform Can shift to an earlier date time normal, it is seen that the change of temperature can affect the accurate shutoff of switch metal-oxide-semiconductor.

Figure 11 is the work wave schematic diagram of the present invention, V_DETWaveform sets forth that temperature raises, temperature is normal and temperature Waveform corresponding during reduction, for open stage, when the temperature increases, corresponding unlatching compensates threshold value V_{ref_on_com}Relatively temperature is just Suitably reduce time often.When the temperature decreases, corresponding unlatching compensates threshold value V_{ref_on_com}Suitably increase time normal compared with temperature.Finally When being held open, the relative value of body diode conduction voltage drop and unlatching threshold value is not with temperature significant change, it is ensured that switch metal-oxide-semiconductor Accurately open；For off-phases, when the temperature increases, corresponding shutoff compensates threshold value V_{ref_off_com}Time normal compared with temperature suitable Increase.When the temperature decreases, corresponding shutoff compensates threshold value V_{ref_off_com}Suitably reduce time normal compared with temperature.Finally it is held off Time I_secThe shutoff threshold current I that waveform is corresponding_sec(off)Not with temperature significant change, the drop point position of GATE waveform keeps solid Fixed not temperature influence, it is ensured that the accurate shutoff of switch metal-oxide-semiconductor.

In sum, the present invention can be switched on and off threshold value along with the change of temperature regulates, and weakens synchronous rectification switch Metal-oxide-semiconductor switch is acted upon by temperature changes, and can realize the accurate switch to switch metal-oxide-semiconductor after regulation.

It should be understood that the foregoing is only the preferred embodiment of the present invention, it is not limited to the power of the present invention Profit scope；Simultaneously above description, the special personage for correlative technology field should understand and implement, therefore other without departing from The equivalence completed under disclosed spirit changes or modifies, and should be included in claim.

Claims (9)

1. synchronous rectifying controller, it is characterised in that: include temperature-compensation circuit (601), open comparator (602) and turn off ratio Relatively device (603), described temperature-compensation circuit (601) and B end and the A end phase of shutoff comparator (603) of opening comparator (602) Even, temperature-compensation circuit (601) receives threshold value (V_ref), temperature-compensation circuit (601) output is opened and is compensated threshold value (V_{ref_on_com}) To opening comparator (602), output turns off and compensates threshold value (V_{ref_off_com}) to turning off comparator (603)；

The A end of described unlatching comparator (602) receives detection magnitude of voltage (V from the VDET end of synchronous rectifying controller (600)_DET), Opening comparator (602) will detection magnitude of voltage (V_DET) compensate threshold value (V with opening_{ref_on_com}) compare, when detection magnitude of voltage (V_DET) reach to open compensation threshold value (V_{ref_on_com}) time, open comparator (602) and generate unlatching signal (SR_on) and export extremely Drive circuit (604)；

The B end of described shutoff comparator (603) receives detection magnitude of voltage (V from the VDET end of synchronous rectifying controller (600)_DET), Turning off comparator (603) will detection magnitude of voltage (V_DET) compensate threshold value (V with turning off_{ref_off_com}) compare, when detection magnitude of voltage (V_DET) reach to turn off compensation threshold value (V_{ref_off_com}) time, turn off comparator (603) and generate cut-off signals (SR_off) and export extremely Drive circuit (604)；

Described drive circuit (604) receives opens signal SR_on and cut-off signals SR_off generation drive voltage signal V_{sr_g}And pass Transport to the GATE end of synchronous rectifying controller (600), control the switch of switch metal-oxide-semiconductor (N2).

Synchronous rectifying controller the most according to claim 1, it is characterised in that: open stage, when temperature raises, switch The conduction voltage drop V of the body diode (D2) of metal-oxide-semiconductor (N2)_SDRaise with temperature and diminish；If it is unchanged to open threshold value, because opening The conduction voltage drop V that body diode (D2) after being more than change is set of threshold value_SDAnd switch metal-oxide-semiconductor (N2) cannot be opened；Temperature is mended Repay circuit (601) regulation and open threshold value, after regulation, open and compensate threshold value (V_{ref_on_com}) suitably subtract when temperature raises Amplitude that is little, that reduced by regulation, is switched body diode (D2) conduction voltage drop of metal-oxide-semiconductor (N2) and opens threshold value when being held open Relative value not with temperature significant change, it is ensured that the accurate unlatching of switch metal-oxide-semiconductor.

Synchronous rectifying controller the most according to claim 1, it is characterised in that: off-phases, when temperature raises, switch Conducting resistance R of metal-oxide-semiconductor (N2)_ds(on)Raise with temperature and become big, if it is unchanged to turn off threshold value, turn off threshold current I_sec(off)Reduce with the rising of temperature, turn off threshold current I_sec(off)The electric current of switch metal-oxide-semiconductor (N2) is flow through when being off Value；Temperature-compensation circuit (601) regulation turns off threshold value, after regulation, turns off and compensates threshold value (V_{ref_off_com}) keep and temperature Raise, the amplitude raised by regulation simultaneously, when being finally held off, turn off threshold current I_sec(off)Not with temperature significant change, Guarantee to switch the accurate shutoff of metal-oxide-semiconductor.

4. according to the synchronous rectifying controller described in claim 1 or 2 or 3, it is characterised in that: described temperature-compensation circuit (601) the first operational amplifier (A1), the first PMOS (P1), the first electric capacity (C1), the first resistance (R1), the second resistance are included (R2), the 3rd resistance (R3), the 4th resistance (R4) and the 5th resistance (R5), the outfan company of described first operational amplifier (A1) Connecing the first PMOS (P1) and the first electric capacity (C1), the V+ end of the first operational amplifier (A1) connects temperature-compensation circuit (601) Input IN, the V-end of the first operational amplifier (A1) is connected to the second resistance (R2) and the 3rd resistance (R3)；

Described first PMOS (P1) is connected with power voltage terminal (VCC), the first resistance (R1) and the second resistance (R2)；

Described 3rd resistance (R3), the 4th resistance (R4), the 5th resistance (R5) are the most connected in order；

Described 5th resistance (R5) connects with ground end.

Synchronous rectifying controller the most according to claim 4, it is characterised in that: described 3rd resistance (R3) and the 4th resistance (R4) the first outfan OUT1 of temperature-compensation circuit (601) is set between.

Synchronous rectifying controller the most according to claim 4, it is characterised in that: described 4th resistance (R4) and the 5th resistance (R5) the second outfan OUT2 of temperature-compensation circuit (601) is set between.

Synchronous rectifying controller the most according to claim 4, it is characterised in that: the input of temperature-compensation circuit (601) The magnitude of voltage of IN, the first outfan OUT1 and the second outfan OUT2 is respectively V_IN、V_OUT1、V_OUT2, then the offset that obtains Computing formula is:

$V_{OUT1}=V_{IN}*(1-\frac{R3}{R3+R4+R5})$

$V_{OUT2}=V_{IN}*\frac{R5}{R3+R4+R5}$

The temperature coefficient value of resistance is normal number or negative constant so that output voltage V_OUT1、V_OUT2For positive temperature characterisitic or negative temperature Characteristic；R3, R5 are positive temperature coefficient, and R4 is negative temperature coefficient；

For temperature-compensation circuit (601), input IN receives threshold value V_ref, the first outfan OUT1 output is opened and is compensated threshold value V_{ref_on_com}, the second outfan OUT2 output turns off and compensates threshold value V_{ref_off_com}；

For open stage, the unlatching using temperature-compensation circuit (601) to generate compensates threshold value V_{ref_on_com}As judging unlatching Condition, i.e. when

V_DET=V_{ref_on_com}

Time meet unlocking condition, the computing formula of body diode (D2) conduction voltage drop and the relative value that opens threshold value is:

$V_{ref\_on\_com}=V_{ref}*(1-\frac{R3}{R3+R4+R5})$

$\frac{V_{SD}}{V_{ref\_on\_com}}=\frac{V_{SD}}{V_{ref}*(1-\frac{R3}{R3+R4+R5})}$

Wherein, threshold value V_refIt is a standard voltage value, for zero-temperature coefficient, V_SDConducting for switch metal-oxide-semiconductor N2 body diode (D2) Pressure drop；

When the temperature increases, the resistance of R3, R5 becomes big, and the resistance of R4 diminishes, by the setting to temperature coefficient so thatBecome big, V_{ref_on_com}Diminishing, the unlatching the most now exported compensates threshold value V_{ref_on_com}For negative temperature characteristic；

For off-phases, the shutoff using temperature-compensation circuit (601) to generate compensates threshold value V_{ref_off_com}As judging to turn off Condition, i.e. when

V_DET=V_{ref_off_com}

Time meet turn-off criterion, turn off threshold current I_sec(off)Computing formula be:

$V_{ref\_off\_com}=V_{ref}*\frac{R5}{R3+R4+R5}$

$I_{\sec \left(off\right)}=\frac{V_{ref\_off\_com}}{R_{ds\left(on\right)}}=\frac{V_{ref}*\frac{R5}{R3+R4+R5}}{R_{ds\left(on\right)}}$

Wherein, threshold value V_refIt is a standard voltage value, for zero-temperature coefficient, R_ds(on)For switching the conducting resistance of metal-oxide-semiconductor N2；

When the temperature increases, the resistance of R3, R5 becomes big, and the resistance of R4 diminishes, by the setting to temperature coefficient so thatBecome big, V_{ref_off_com}Becoming big, the shutoff i.e. exported compensates threshold value V_{ref_off_com}For positive temperature characterisitic；

When temperature raises, switch metal-oxide-semiconductor body diode (D2) conduction voltage drop diminishes, and opens and compensates threshold value V_{ref_on_com}Diminish, finally When being held open, the relative value of body diode (D2) conduction voltage drop and unlatching threshold value is not with temperature significant change, it is ensured that switch MOS The accurate unlatching of pipe.

Synchronous rectifying controller the most according to claim 1, it is characterised in that: threshold value (V_ref) it is a standard voltage value.

Synchronous rectifying controller the most according to claim 1, it is characterised in that: it is applied to inverse-excitation type switch power-supply system In.