CN202634255U - Synchronous rectification circuit - Google Patents
Synchronous rectification circuit Download PDFInfo
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- CN202634255U CN202634255U CN 201220208988 CN201220208988U CN202634255U CN 202634255 U CN202634255 U CN 202634255U CN 201220208988 CN201220208988 CN 201220208988 CN 201220208988 U CN201220208988 U CN 201220208988U CN 202634255 U CN202634255 U CN 202634255U
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- 230000001360 synchronised effect Effects 0.000 title claims abstract description 138
- 238000001514 detection method Methods 0.000 claims abstract description 23
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- 239000008186 active pharmaceutical agent Substances 0.000 description 21
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Abstract
A synchronous rectification circuit is disclosed. A plurality of grids are led out from a synchronous rectifier tube in the synchronous circuit, and during zero-crossing detection, a part of MOS units in the synchronous rectifier tube are turned off, so that the on-resistance between the drain electrode and the source electrode of the synchronous rectifier tube is increased. The zero-crossing detection process can increase the sensed voltage signal and improve the current zero-crossing detection precision.
Description
Technical field
The embodiment of the utility model relates to electronic circuit, relates in particular to a kind of circuit of synchronous rectification.
Background technology
In the synchronous rectified DC-DC converter, under the situation of underloading, circuit working is at inductive current discontinuous mode (DCM).During synchronous rectifier afterflow conducting, inductive current is linear to descend.When electric current dropped to zero, if synchronous rectifier conducting still, then output capacitance will be through the synchronous rectification tube discharge, and electric current pours in down a chimney, thereby greatly reduces the conversion efficiency of power supply.
For addressing this problem, can, electric current drive synchronous rectifier and turn-off when drop to zero.For this reason, we need detect the electric current that flows through synchronous rectifier usually, promptly need zero cross detection circuit that current zero-crossing point is detected, to determine whether to open or turn-off synchronous rectifier.Usually, we will use the conducting resistance R of synchronous rectifier self
L, convert current signal into voltage signal, and utilize zero-crossing comparator to detect the zero crossing of electric current.For this kind detection mode, the precision of zero passage detection is mainly by the input offset voltage V of zero-crossing comparator in the circuit
OSDecision.Conducting resistance R when synchronous rectifier
LWhen very little, its pressure drop is also very little, and the precision of zero passage detection will receive very big influence.
The utility model content
Consider one or more problem of the prior art, proposed a kind of circuit of synchronous rectification.
Embodiment according to the utility model; A kind of circuit of synchronous rectification has been proposed; Comprise: switching circuit, comprise a power switch pipe and a synchronous rectifier at least, the conducting through power switch pipe and synchronous rectifier converts input signal into the output signal with turn-offing; Wherein, said synchronous rectifier comprises the MOS unit of a plurality of parallel connections; Zero cross detection circuit; Comprise first voltage comparator and second voltage comparator, the inverting input of first voltage comparator and second voltage all receives the voltage sense signal between synchronous rectifier drain-source the two poles of the earth, and the first voltage comparator in-phase input end receives first reference voltage; The second voltage comparator in-phase input end receives second reference voltage; Wherein, second reference voltage is greater than first reference voltage, and said first voltage comparator and second voltage comparator are exported two comparison signals respectively; Feedback control circuit is electrically connected to the output of switching circuit, and according to two comparison signals of zero cross detection circuit and the output signal of switching circuit, the output control signal is at least two grids of power controlling switching tube and synchronous rectifier respectively.
According to the embodiment of the utility model, the conducting resistance of said zero cross detection circuit through said synchronous rectifier converts current signal into voltage signal and produces said voltage sense signal.
According to the embodiment of the utility model, when voltage sense signal equaled second reference voltage, said feedback control circuit turn-offed a part of MOS unit in the said synchronous rectifier; When voltage sense signal equaled first reference voltage, said feedback control circuit turn-offed remaining that part of MOS unit in the said synchronous rectifier.
According to the embodiment of the utility model, the grid of the MOS unit of a plurality of parallel connections in the said synchronous rectifier is divided at least two groups and connects, and draws at least two grids accordingly.
According to the embodiment of the utility model, said synchronous rectifier is a metal-oxide-semiconductor.
Utilize such scheme, improved the precision of zero passage detection.
Description of drawings
Figure 1A is depicted as the synchronous rectified DC-DC converters schematic circuit;
Figure 1B is depicted as the synchronous rectified DC-DC converters exemplary waveform diagrams;
Shown in Figure 2 is existing circuit of synchronous rectification sketch map with current over-zero testing circuit;
Fig. 3 A is depicted as synchronous rectifier one embodiment schematic diagram;
Fig. 3 B is depicted as the synchronous rectifier structural representation according to the utility model one embodiment;
Fig. 3 C is depicted as the synchronous rectifier structural representation according to another embodiment of the utility model;
Shown in Figure 4 is according to the utility model one embodiment inductive current and sensing voltage waveform sketch map;
Shown in Figure 5 is circuit of synchronous rectification schematic circuit according to the utility model one embodiment.
Embodiment
To describe the specific embodiment of the utility model below in detail, should be noted that the embodiments described herein only is used to illustrate, be not limited to the utility model.In the following description, for the thorough to the utility model is provided, a large amount of specific detail have been set forth.Yet it is obvious that for those of ordinary skills: needn't adopt these specific detail to carry out the utility model.In other instances,, do not specifically describe known circuit, material or method for fear of obscuring the utility model.
Be elaborated below in conjunction with the embodiment of accompanying drawing to the utility model.
Figure 1A is depicted as synchronous rectified DC-DC converters illustrative circuitry Figure 100.This circuit of synchronous rectification comprises power switch tube S W, synchronous rectifier SR, inductance L, capacitor C and load.Wherein, power switch tube S W and synchronous rectifier SR are series at power supply V
INAnd between the ground, the end of inductor L links to each other with the link of synchronous rectifier SR with power switch tube S W, and the other end of inductor L links to each other with an end of capacitor C and load, the other end ground connection of capacitor C and load.This circuit of synchronous rectification also comprises feedback control circuit, the output signal V of its receiving circuit
OAs feedback signal, and according to conducting and the shutoff of feedback signal power controlling switching tube SW and synchronous rectifier SR.
Here shown in is synchronous rectification BUCK converter topology structure; Certainly also can adopt other DC topology, like structures such as synchronous rectification anti exciting converter, synchronous rectification forward converter, synchronous rectification bridge converters with synchronous rectification.
In Figure 1A illustrated embodiment, when power switch tube S W conducting, when synchronous rectifier SR turn-offs, supply voltage V
INOutput capacitance C is charged output voltage V through inductor L
ORise; When power switch tube S W shutoff, during synchronous rectifier SR conducting, synchronous rectifier SR is to inductive current I
LAfterflow, and I
LLinearity reduces.When circuit working under electric current non-continuous mode (DCM), inductive current I
LLinear decline worked as I
LWhen dropping to zero, if synchronous rectifier SR conducting still, then output capacitance C can be through synchronous rectifier SR discharge, electric current I
LOppositely, thus greatly reduce the conversion efficiency of power supply.
Figure 1B is depicted as the oscillogram of synchronous rectified DC-DC converters 100.Under the DCM pattern, as inductive current I through synchronous rectifier SR afterflow
LDuring zero passage, SR in time turn-offs, at this moment inductive current I
LWith reverse flow, inductive current I
LWaveform is shown in dotted line in (b) among Figure 1B.In order to stop inductive current I
LThe reverse efficient that reduces circuit of synchronous rectification will increase the current over-zero testing circuit usually in the circuit of synchronous rectification structure.At this moment, as the inductive current I that flows through synchronous rectifier SR
LArrive the current over-zero threshold values constantly, turn-off synchronous rectifier SR, inductive current I
LWaveform is shown in (c) among Figure 1B.
Shown in Figure 2 is the existing circuit of synchronous rectification signal Figure 200 that current over-zero detects that has.In order to prevent that capacitor from passing through synchronous rectifier SR and discharging over the ground; Usually will in synchronous rectified DC-DC converters 100 shown in Figure 1, increase current over-zero testing circuit 210, judge the sense of current and the size that flows through synchronous rectifier SR through the magnitude of voltage between the synchronous rectifier SR drain-source.In embodiment illustrated in fig. 2, also show the conducting resistance R of power switch tube S W
HConducting resistance R with synchronous rectifier
L, through the conducting resistance R of synchronous rectifier
LCurrent signal is converted into voltage sense signal V
DSFeedback control loop in the circuit of synchronous rectification 200 comprises feedback circuit 221 and control circuit 222; Feedback circuit 221 will be exported conversion of signals to be feedback signal and to deliver to control circuit 222; The output signal of control circuit 222 receiving feedback signals and zero cross detection circuit 210, and conducting and the shutoff of output control signal power controlling switching tube SW and synchronous rectifier SR.As shown in Figure 2, W ends when power switch tube S, and during synchronous rectifier SR conducting, inductance L is through synchronous rectifier SR afterflow, and the electric current of synchronous rectifier SR flows to drain D by source S, at this moment the voltage V between the synchronous rectifier SR drain-source
DSFor negative.
In embodiment illustrated in fig. 2, zero cross detection circuit 210 comprises a zero-crossing comparator, and its inverting input receives voltage sense signal V
DS, normal phase input end reception value is zero reference voltage, and comparative result is delivered to control circuit 222.Because the input offset voltage V of comparator
OSNon-vanishing, as voltage sense signal V
DSEqual input offset voltage V
OSThe time, synchronous rectifier SR turn-offs, and therefore, the precision of zero passage detection depends primarily on the input offset voltage V of comparator
OSVoltage sense signal V
DS=-R
L* I
L, as the conducting resistance R of synchronous rectifier SR
LValue hour, voltage sense signal V
DSValue very little, the precision of current over-zero will receive bigger restriction.For example, the input offset voltage V of no-voltage comparator
OSBe 3mV, the conducting resistance of synchronous rectifier SR is 3m Ω, then at inductive current I
LDuring for 1A, comparator will output signal to control circuit, turn-off synchronous rectifier SR.At this moment, current over-zero detects inaccurate, low precision.
Fig. 3 A is depicted as synchronous rectifier one embodiment schematic diagram.It will be obvious to those skilled in the art that a power MOS pipe is formed in parallel by a large amount of MOS unit, the quantity of MOS unit is decided by the size of power MOS pipe size.One of power MOS pipe effect that a plurality of MOS unit composes in parallel is to reduce the conducting resistance R between the power MOS pipe drain-source
DS (on), the MOS element number of parallel connection is many more, the conducting resistance R between the power MOS pipe drain-source
DS (on)More little.In Fig. 3 a illustrated embodiment, synchronous rectifier SR is by N MOS unit M
1, M
2... M
NCompose in parallel MOS unit M
1, M
2... M
NDrain electrode be joined together to form the drain D of synchronous rectifier SR, MOS unit M
1, M
2... M
NSource electrode be joined together to form the source S of synchronous rectifier SR, MOS unit M
1, M
2... M
NGrid be joined together to form the grid G of synchronous rectifier SR, the conducting resistance between each MOS unit drain-source is R
ON, the conducting resistance of synchronous rectifier SR is R
ON/ N.
Fig. 3 B is depicted as the synchronous rectifier structural representation according to the utility model one embodiment.Synchronous rectifier SR is by N MOS unit M
1, M
2... M
NCompose in parallel MOS unit M
1, M
2... M
NDrain electrode be joined together to form the drain D of synchronous rectifier SR, MOS unit M
1, M
2... M
NSource electrode be joined together to form the source S of synchronous rectifier SR, MOS unit M
1, M
2... M
NGrid draw separately, form a plurality of grid G of synchronous rectifier SR
1, G
2... G
N, the conducting resistance between each MOS unit drain-source is R
ON, the conducting resistance of synchronous rectifier SR is R
ON/ N.
When power switch tube S W shutoff, during synchronous rectifier SR afterflow conducting, control circuit outputs control signals to a plurality of grid G of synchronous rectifier SR
1, G
2... G
N, all equal conductings in MOS unit, the conducting resistance of synchronous rectifier SR is R
ON/ N.As sensing voltage V
DSNear comparator input offset voltage V
OSThe time, as at V
OSDuring+Δ v, cutoff MOS unit for example passes through G
2... G
NTurn-off MOS unit M
2... M
N, conducting MOS unit M only
1, this moment, the conducting resistance of synchronous rectifier SR became R
ONCompare and do not turn-off MOS unit M
2... M
NBefore, conducting resistance increases N-1 doubly, and the current over-zero accuracy of detection has improved N-1 doubly.Sensing voltage V
DSContinue to drop to comparator input imbalance pressure regulation V
OSThe time, the grid G through synchronous rectifier SR again
1Turn-off MOS unit M
1, whole synchronous rectifier SR turn-offs.
Fig. 3 C is depicted as the synchronous rectifier structural representation according to another embodiment of the utility model.Likewise, synchronous rectifier SR is composed in parallel by N MOS unit, and N MOS unit can be divided into module 310, module 320 two parts, and module 310 comprises MOS unit M
1... M
M, module 320 comprises MOS unit M
M+1... M
N(M＜N).MOS unit M
1, M
2... M
NDrain electrode be joined together to form the drain D of synchronous rectifier SR pipe, MOS unit M
1, M
2... M
NSource electrode be joined together to form the source S of synchronous rectifier SR, MOS unit M
1... M
MGrid link together and draw, form the grid G of module 310
M, MOS unit M
M+1M
NGrid link together and draw, form the grid G of module 320
N, the conducting resistance between each MOS unit drain-source is R
ON, the conducting resistance of synchronous rectifier SR is R
ON/ N.
When power switch tube S W shutoff, during synchronous rectifier SR afterflow conducting, all equal conductings in MOS unit, the conducting resistance of synchronous rectifier SR is R
ON/ N.As node voltage V
DSNear input offset voltage V
OSThe time, such as at V
OSDuring+Δ v, at first pass through grid G
MM MOS unit turn-offed in control, and this moment, the conducting resistance of synchronous rectifier SR became R
ON/ (N-M).Compare before the not shutoff, conducting resistance has increased N/ (N-M)-1 times, and the current over-zero accuracy of detection has improved N/ (N-M)-1 times.As sensing voltage V
DSContinue to drop to comparator input offset voltage V
OSThe time, through grid G
NN-M remaining MOS unit turn-offed in control, and whole synchronous rectifier SR turn-offs.
Fig. 3 B shows the situation that each MOS unit of forming synchronous rectifier SR is drawn grid respectively separately, and Fig. 3 C shows the MOS unit of forming synchronous rectifier SR and is divided into two groups of situations of drawing two grids.Yet the technical staff in present technique field should be appreciated that in other embodiments the MOS unit of synchronous rectifier SR can be other situation of dividing into groups.
Shown in Figure 4 is according to the utility model one embodiment inductive current and sensing voltage waveform sketch map 400.When power switch tube S W conducting, sensing voltage V
DS=V
IN-I
L* R
HWhen power switch tube S W shutoff, during synchronous rectifier SR afterflow conducting, sensing voltage V
DS=-I
L* R
LIn waveform sketch map shown in Figure 4, the offset voltage of comparator is V
OS, as sensing voltage V
DS=V
OSDuring+Δ v, turn-off the part MOS unit among the synchronous rectifier SR, increase the conducting resistance R of synchronous rectifier SR
L, this moment sensing voltage V
DSValue increase to the V that b is ordered by original value a point
DS', and drop to offset voltage V with new slope
OSBy inductive current I among the figure
LWaveform can know, as conducting resistance R
LBefore not increasing, the current over-zero threshold values is shown in dotted line among the figure, when increasing conducting resistance R
LAfter, inductive current zero passage threshold values reduces, and the zero passage detection precision improves.Work as R
LWhen increasing K times, equal input offset voltage V at sensing voltage
OSConstantly, the current over-zero threshold values reduces K doubly.For example, the input offset voltage V of comparator
OSBe 3mV, the conducting resistance R of synchronous rectifier SR
LIncrease 10 times, increase to 30m Ω by 3m Ω, the current over-zero threshold values is reduced to 0.1A by 1A, and the zero passage detection precision has improved 10 times.
Shown in Figure 5 is circuit of synchronous rectification schematic circuit 500 according to the utility model one embodiment.Circuit of synchronous rectification 500 comprises switching circuit, feedback control circuit and current over-zero testing circuit 510.Switching circuit comprises power switch tube S W, synchronous rectifier SR, inductance L, capacitor C and load.Wherein power switch tube S W and synchronous rectifier SR are series at power supply V
INAnd between the ground, the conducting resistance of power switch tube S W is R
H, the conducting resistance of synchronous rectifier is R
L, the end of inductor L links to each other with the link of synchronous rectifier SR with power switch tube S W, and the other end of inductor L links to each other with an end of capacitor C and load, the other end ground connection of capacitor C and load.Synchronous rectifier SR has the structure that a plurality of MOS unit is connected in parallel, and draws at least two grids.
Feedback control circuit comprises feedback circuit 521 and control circuit 522; Feedback circuit 521 will be exported conversion of signals to be feedback signal and to deliver to control circuit 522; The output signal of control circuit 522 receiving feedback signals and zero cross detection circuit 510, and conducting and the shutoff of output control signal power controlling switching tube SW and synchronous rectifier SR.Zero cross detection circuit 510 comprises two voltage comparator CV
1And CV
2, it all has input offset voltage V
OSComparator C V
1Inverting input receives voltage sense signal V
DS, normal phase input end reception value is zero reference voltage; Comparator C V
2Inverting input receives voltage sense signal V
DS, normal phase input end reception value is the reference voltage of Δ v.Control circuit 522 receives comparator C V
1And CV
2The output signal.As voltage sense signal V
DS=V
OSDuring+Δ v, voltage comparator CV
1And CV
2Difference output low level signal and high level signal to control circuit 522, control circuit 522 outputs control signals to synchronous rectifier SR according to this two level signal, and cutoff MOS unit is to increase the conducting resistance of synchronous rectifier SR.As voltage sense signal V
DS=V
OSThe time, voltage comparator CV
1And CV
2Equal output low level signal to control circuit 522, control circuit 522 outputs control signals to synchronous rectifier SR according to this two level signal, turn-offs remaining part MOS unit, and this moment, synchronous rectifier SR turn-offed fully.
Should be noted that it is more known ins and outs for a person skilled in the art that top description has been omitted for the utility model is more readily understood.
Those skilled in the art should also be understood that the used term of the used embodiment of the utility model is explanation and exemplary and nonrestrictive term.Because the utility model practical implementation and do not break away from the spirit or the essence of utility model in a variety of forms; So be to be understood that; The foregoing description is not limited to any aforesaid details; And should in enclose spirit that claim limited and scope, explain widely, therefore fall into whole variations and remodeling in claim or its equivalent scope and all should be the claim of enclosing and contain.
Claims (5)
1. a circuit of synchronous rectification is characterized in that, said circuit of synchronous rectification comprises:
Switching circuit comprises a power switch pipe and a synchronous rectifier at least, and the conducting through power switch pipe and synchronous rectifier converts input signal into the output signal with turn-offing, and wherein, said synchronous rectifier comprises the MOS unit of a plurality of parallel connections;
Zero cross detection circuit; Comprise first voltage comparator and second voltage comparator, the inverting input of first voltage comparator and second voltage all receives the voltage sense signal between synchronous rectifier drain-source the two poles of the earth, and the first voltage comparator in-phase input end receives first reference voltage; The second voltage comparator in-phase input end receives second reference voltage; Wherein, second reference voltage is greater than first reference voltage, and said first voltage comparator and second voltage comparator are exported two comparison signals respectively;
Feedback control circuit is electrically connected to the output of switching circuit, and according to two comparison signals of zero cross detection circuit and the output signal of switching circuit, the output control signal is at least two grids of power controlling switching tube and synchronous rectifier respectively.
2. circuit of synchronous rectification as claimed in claim 1 is characterized in that, the conducting resistance of said zero cross detection circuit through said synchronous rectifier converts current signal into voltage signal and produce said voltage sense signal.
3. circuit of synchronous rectification as claimed in claim 1 is characterized in that,
When voltage sense signal equaled second reference voltage, said feedback control circuit turn-offed a part of MOS unit in the said synchronous rectifier;
When voltage sense signal equaled first reference voltage, said feedback control circuit turn-offed remaining that part of MOS unit in the said synchronous rectifier.
4. circuit of synchronous rectification as claimed in claim 1 is characterized in that, the grid of the MOS unit of a plurality of parallel connections in the said synchronous rectifier is divided at least two groups and connects, and draws at least two grids accordingly.
5. circuit of synchronous rectification as claimed in claim 1 is characterized in that, said synchronous rectifier is a metal-oxide-semiconductor.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220208988 CN202634255U (en) | 2012-05-10 | 2012-05-10 | Synchronous rectification circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220208988 CN202634255U (en) | 2012-05-10 | 2012-05-10 | Synchronous rectification circuit |
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| CN202634255U true CN202634255U (en) | 2012-12-26 |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102735914A (en) * | 2012-05-10 | 2012-10-17 | 成都芯源系统有限公司 | Synchronous rectification circuit and zero-crossing detection method |
| CN104753346A (en) * | 2013-12-30 | 2015-07-01 | 展讯通信（上海）有限公司 | Technology for improving efficiency of BUCK circuit |
| CN108279733A (en) * | 2018-02-11 | 2018-07-13 | 成都英特格灵微电子技术有限公司 | A kind of electric current limit reference generating circuit and initialization circuit |
| CN111865052A (en) * | 2020-04-20 | 2020-10-30 | 成都芯源系统有限公司 | Drive circuit and drive method for driving power switch |
-
2012
- 2012-05-10 CN CN 201220208988 patent/CN202634255U/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102735914A (en) * | 2012-05-10 | 2012-10-17 | 成都芯源系统有限公司 | Synchronous rectification circuit and zero-crossing detection method |
| CN102735914B (en) * | 2012-05-10 | 2014-12-31 | 成都芯源系统有限公司 | synchronous rectification circuit and zero-crossing detection method |
| CN104753346A (en) * | 2013-12-30 | 2015-07-01 | 展讯通信（上海）有限公司 | Technology for improving efficiency of BUCK circuit |
| CN104753346B (en) * | 2013-12-30 | 2017-05-24 | 展讯通信（上海）有限公司 | Technology for improving efficiency of BUCK circuit |
| CN108279733A (en) * | 2018-02-11 | 2018-07-13 | 成都英特格灵微电子技术有限公司 | A kind of electric current limit reference generating circuit and initialization circuit |
| CN108279733B (en) * | 2018-02-11 | 2023-12-05 | 四川易冲科技有限公司 | Current limit reference generation circuit and setting circuit |
| CN111865052A (en) * | 2020-04-20 | 2020-10-30 | 成都芯源系统有限公司 | Drive circuit and drive method for driving power switch |
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