CN1780128A - Synchronous commutating self-driving circuit for single-end conversion - Google Patents
Synchronous commutating self-driving circuit for single-end conversion Download PDFInfo
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- CN1780128A CN1780128A CNA2004100917676A CN200410091767A CN1780128A CN 1780128 A CN1780128 A CN 1780128A CN A2004100917676 A CNA2004100917676 A CN A2004100917676A CN 200410091767 A CN200410091767 A CN 200410091767A CN 1780128 A CN1780128 A CN 1780128A
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Abstract
A synchronous rectifying type self-drive circuit for single-end converter is composed of drive signal source, the second acceleration cut-off circuit, the second delay circuit, synchronous rectifier and holding circuit. Its connection scheme of various devices in circuit is also disclosed. Its advantages are simple circuit, less loss, and high efficiency and adaptability.
Description
Technical field
The present invention relates to field of power supplies, relate in particular to the self-driven circuit that is applied to single-end conversion (comprising single-end ortho-exciting, single-ended reverse exciting etc.) synchronous rectification.
Background technology
Along with the sizable application of low-voltage, high-current DC/DC converter, synchronous rectification in the nineties in last century also gradually the development and maturation is got up.Low-voltage, high-current DC/DC converter secondary synchronous rectification generally mainly comprises three kinds: a kind of is the self-driven mode that adopts the coupling magnetic circuit; A kind of is the separate excitation mode that adopts independent controling circuit; The third is that part adopts self-powered and part to adopt the combination of separate excitation mode.Therefore from technical costs and performance, first kind of self-driven mode has tangible advantage, develops very fastly, various circuit form also occurred, wherein the most extensive use mainly contain following a few class:
1, with main winding as directly driving, main winding provides the energy of output on the one hand, and the drive signal of synchronous rectifier and continued flow tube is provided on the other hand.Such circuit has the drive circuit characteristic of simple, but it is bigger with the work change in duty cycle to drive amplitude, and the spike that the leakage inductance of main transformer produces can have a strong impact on the reliability of synchronous rectifier and continued flow tube.And, make this circuit can not be applied in the higher or lower converter of output voltage owing to adopt the restriction of MOSFET synchronous rectifier and continued flow tube grid voltage between source electrodes, and produce under the situation about resetting in advance at main transformer, also can't use.
2, adopt the self-driven mode of auxiliary winding.Such circuit application scope is not subjected to the restriction of self output voltage, and is relatively flexible.And have centre cap on the drive form, and being equivalent to double winding, each winding drives synchronous rectifier and synchronous freewheeling pipe respectively.It is more that but its shortcoming is a umber of turn, produces unnecessary negative voltage in the drive signal, and drive loss is bigger, and it is bigger with the work change in duty cycle to drive amplitude.Together moreover, because the drive signal of synchronous freewheeling pipe is subjected to the influence of the reverse resetting voltage of main transformer very big, if main transformer resets in advance at person in charge's blocking interval (the single-end ortho-exciting circuit that for example former limit employing capacitor resonance resets), the synchronous freewheeling pipe also can turn-off therefore and in advance so, diode current flow in its body, the loss meeting increases greatly, has a strong impact on efficient.
In addition, in this type circuit, also have a kind of as United States Patent (USP) " a kind of synchronous commutation self-driving circuit that is applied to the active-clamp the converter " (patent No.: 5590032; Open date: 1996.12.31; Obligee: Lucent Technologies Inc.,) described mode, in this circuit, adopt simplex winding driven synchronous rectifier and synchronous freewheeling pipe, a kind of mode drives the more shortcoming of winding before having overcome well, and the number of turn has only half of preceding a kind of mode.This patent improves reliability in order to overcome the amplitude problem that drives in addition, adopts MOSFET to form amplitude limiter circuit, and grid connects reference voltage, and source electrode acts on the grid of synchronous rectifier and synchronous freewheeling pipe.Do like this and have apparent in view shortcoming in the practicality equally: the driving amplitude of winding rely on the auxiliary circuit amplitude limit, so drive loss is bigger than higher on the one hand; Need the MOSFET that selects conducting resistance smaller on the other hand, otherwise can influence the turn-on and turn-off time of synchronous rectifier and synchronous freewheeling pipe, efficient reduces.The MOSFET conducting resistance is all bigger generally speaking, needs to select power and the bigger model of outline packages, so also limited the application of this circuit to the smaller occasion of space requirement.The same with preceding a kind of mode in addition, this patent circuit can't be applied to the situation that main transformer resets in advance.
3, the self-driven mode of electric charge maintenance.This mode can be used under the condition that main transformer resets in advance, makes synchronous rectification can be applied to the single-end conversion circuit widely.Made full use of the high characteristics of input impedance between fieldtron grid source electrode technically, be maintained driving voltage, do not descended because main transformer resets in advance by auxiliary circuit.But its shortcoming is the voltage of keeping exists certain overlapping easily with the unlatching of synchronous rectifier on the turn-off time, thereby produces the phenomenon of conducting simultaneously, reduces overall efficiency and reliability.
Summary of the invention
Technical problem to be solved of the present invention be prior art exist by coupling magnetic circuit leakage inductance cause that the driving voltage peak amplitude is excessive, circuit flexibility and versatility is poor, synchronous rectifier and synchronous freewheeling pipe switch transition overlong time, can't guarantee enough drive currents and switching speed, can't guarantee when the main transformer magnetic core resets in advance that the synchronous freewheeling pipe continues to keep problems such as conducting, drive loss be serious, in the hope of the synchronous commutation self-driving circuit that a kind of circuit form is succinct, loss is little, efficient is high, adaptive capacity is strong is provided.
For achieving the above object, the present invention has constructed a kind of synchronous commutation self-driving circuit that is applied to single-end conversion, it is characterized in that, comprises with the lower part: drive signal, second is quickened breaking circuit, second delay circuit, synchronous rectifier and maintenance loop;
The source S R-GND of the grid A ' of the described synchronous rectifier of one termination of the described second acceleration breaking circuit output, the described synchronous rectifier of another termination of output, the other end of the described drive signal of control termination; Give between the described synchronous rectifier grid source electrode a low-impedance discharge loop is provided, quicken the turn-off time of described synchronous rectifier;
The output of described second delay circuit drives the grid A ' of described synchronous rectifier, provides and control the drive current of described synchronous rectifier, regulates the service time of described synchronous rectifier;
Described drive signal one termination second is quickened the control end of breaking circuit; The input of described second delay circuit of its another termination; Provide and the synchronous drive signal of the former limit of single-ended reverse exciting switch change-over;
Described synchronous rectifier source electrode point is SR-GND.
Described drive signal and main winding are synchronous, and by the winding generation of an independent coupling, drive voltage amplitude can be adjusted umber of turn as required and realize; If the voltage that the output main winding of secondary side produces is suitable, also can directly take from it.
The synchronous commutation self-driving circuit that is applied to single-end conversion that the present invention constructed comprises that also keeps a loop, described maintenance loop input termination SR-GND, the described drive signal of output termination offers described second and quickens current path of breaking circuit control end and electric charge maintenance.
For single-ended forward converter, comprise that also first quickens breaking circuit, first delay circuit and synchronous freewheeling pipe;
The source S R-GND of the grid A of the described synchronous freewheeling pipe of one termination of the described first acceleration breaking circuit output, the described synchronous freewheeling pipe of another termination of output, an end of the described drive signal of control termination; Give between the described synchronous freewheeling pipe grid source electrode a low-impedance discharge loop is provided, quicken the turn-off time of described synchronous freewheeling pipe;
The output of described first delay circuit drives the grid A of described synchronous freewheeling pipe, provides and control the drive current of described synchronous freewheeling pipe, regulates the service time of described synchronous freewheeling pipe.
Adopt circuit of the present invention, compared with prior art, combine the advantage of dissimilar self-driven circuit, owing to adopt simplex winding to drive, so simple in structure; And the impedance that drives the loop is little, and drive current is big.Synchronous rectifier and synchronous freewheeling pipe switch transition speed are fast.Fu Jia acceleration breaking circuit cooperates delay circuit in addition, can optimize the change-over time of synchronous rectifier and synchronous freewheeling pipe, further reduces transducer loose, raises the efficiency, and driving does not have negative pressure.Because circuit has the portion of energy back coupling, can reduce drive loss simultaneously, raise the efficiency, the amplitude of driving voltage makes moderate progress with the situation of work change in duty cycle.In addition, R in the delay circuit or RC resistance can be regulated the time on the one hand, can absorb the spike of drive signal on the other hand.Improve reliability.Two diodes that increase, can realize that the electric charge maintenance drives (see figure 4), synchronous rectification can be applied in the single-ended converter of wide more model, cooperate additional acceleration breaking circuit simultaneously, delay circuit, can overcome the shortcoming that common electric charge maintenance drives, ON time in the time of minimizing even elimination synchronous freewheeling pipe and synchronous rectifier.Further improve the efficient of single-ended converter.Device of the present invention can also be applied in single end flyback converter, in the secondary synchronous rectification driving circuit.
Description of drawings
Fig. 1 is a structure drawing of device of the present invention.
Fig. 2 is the structure chart of device of the present invention in single-ended forward converter is used.
Fig. 3 is the structure drawing of device as first embodiment of the invention.
Fig. 4 is the structure drawing of device as second embodiment of the invention.
Fig. 5 is the structure drawing of device as third embodiment of the invention.
Fig. 6 is the example structure figure that is applied in the single-ended active-clamp converter.
Fig. 7 is the example structure figure that is applied to single-ended capacitor resonance reset transform device.
Fig. 8 is the example structure figure that is applied to the single-ended flyback converter.
Embodiment
Be described in further detail below in conjunction with the enforcement of accompanying drawing technical scheme:
Main purpose of the present invention be overcome that prior art exists cause the flexibility and the versatility problem of the excessive problem of driving voltage peak amplitude, circuit by coupling magnetic circuit leakage inductance, it is few promptly to be implemented in middle widespread usage of single-end conversion (comprising single-end ortho-exciting and anti-sharp topology) and device, and area occupied is few; The optimization problem of synchronous rectifier and synchronous freewheeling pipe switch transition time; How synchronous rectifier and continued flow tube when driving a plurality of parallel connections simultaneously guarantee enough drive currents, guarantee the switching speed problem; When the main transformer magnetic core resets in advance, how to guarantee that the synchronous freewheeling pipe continues to keep the problem of conducting; Reduce the aspects such as problem of drive loss.
The present invention combines the advantage of several self-driven circuit at present, adopt simplex winding directly to drive synchronous rectifier and continued flow tube, have circuit and simply simultaneously can obtain enough drive currents again, increased the shutoff that small-power MOSFET is respectively applied for acceleration synchronization rectifying tube and synchronous freewheeling pipe, be connected in parallel on the voltage-stabiliser tube between small-power MOSFET grid source electrode, when the Control current forward, play voltage-stabilizing protection; When Control current is reverse, play the gate source voltage clamp and the control signal path is provided, small-power MOSFET is by concerning with the cross-join formation self-locking in logic that drives winding, add the RC circuit of series connection, can form optimization to the time that turns on and off of synchronous rectification and continued flow tube, wherein capacitor C refers to, comprise input capacitance between corresponding synchronous rectifier that drives or continued flow tube grid source electrode, correspondence is connected in parallel on the output capacitance of electric capacity and small-power MOSFET drain-source interpolar between synchronous rectifier or continued flow tube grid source electrode, also can add suitable capacitor C ' and the indication capacitances in series, synchronous rectifier or continued flow tube grid voltage between source electrodes that the result of series connection on the one hand can corrective action drives in correspondence are on the other hand with the same service time that can adjust synchronous rectifier or continued flow tube of resistance R of series connection.Simplex winding type of drive lower part drives energy and can feedback, and therefore can reduce drive loss, and when for example synchronous rectifier was opened, the part voltage between synchronous freewheeling pipe grid source electrode charged to synchronous rectifier together with the induced voltage that drives winding.Can improve of the influence of work duty ratio, improve driving efficient simultaneously the synchronized signal amplitude.Driving voltage spike problem to leakage inductance causes will improve the coupling coefficient that drives winding and main winding on the one hand as far as possible, reduces leakage inductance; On circuit, increase the absorption circuit that RC absorbs and enough become by resistance and voltage-stabiliser tube simultaneously under improper situation on the other hand, improved the reliability of drive circuit.
As can be seen from Figure 2, the present invention mainly comprises following components:
1. first quicken breaking circuit, the grid A of a termination synchronous freewheeling pipe of its output, the source S R-GND of another termination synchronous freewheeling pipe of output, an end of control termination drive signal.Effect is to providing a low-impedance discharge loop between synchronous freewheeling pipe grid source electrode, thus the turn-off time of acceleration synchronization continued flow tube.
2. second quicken breaking circuit, the grid A ' of a termination synchronous rectifier of its output, the source S R-GND of another termination synchronous rectifier of output, the other end of control termination drive signal.Effect is to a low-impedance discharge loop is provided between synchronous rectifier grid source electrode, thus the turn-off time of acceleration synchronization rectifying tube.
3. first delay circuit, its output drives the grid A of synchronous freewheeling pipe.Effect is to provide and control the drive current of synchronous freewheeling pipe, regulates the service time of synchronous freewheeling pipe.
4. second delay circuit, its output drives the grid A ' of synchronous rectifier.Effect is to provide and control the drive current of synchronous rectifier, regulates the service time of synchronous rectifier.
5. the drive signal synchronous with main winding.This signal is preferably produced by the winding of an independent coupling, and drive voltage amplitude can be adjusted umber of turn as required and realizes like this, if the voltage of the output winding of secondary side generation is suitable certainly, also can directly take from it.Drive signal is produced by an independent winding with the coupling of single-end ortho-exciting main transformer, and drive voltage amplitude can be adjusted umber of turn as required and realize.The one end connects the input of first delay circuit and the control end of the second acceleration breaking circuit respectively; Its other end connects the input of second delay circuit and the control end of the first acceleration breaking circuit respectively.Effect is to provide and the synchronous drive signal of the former limit of single-end ortho-exciting switch change-over.
Above mentioned synchronous rectifier and synchronous freewheeling pipe source electrode are common ground, and the place is SR-GND altogether.
To Fig. 5, first quickens breaking circuit, second to quicken breaking circuit, first delay circuit, the second delay circuit situation as follows described in corresponding diagram 1 and Fig. 2 for three following figure: Fig. 3:
Fig. 3 R3 in Fig. 4, first quickens breaking circuit described in VD1 and the VT1 pie graph 2;
Fig. 3 R1 in Fig. 5, second quickens breaking circuit described in VD2 and VT2 pie graph 1 and Fig. 2;
Fig. 3 R2 or R2 in Fig. 4, first delay circuit in the C1 pie graph 2;
Fig. 3 R4 or R4 in Fig. 5, second delay circuit among C2 pie graph 1 and Fig. 2;
Keep the loop in R3, the VD1 pie graph 1 among Fig. 5;
Concrete annexation is as follows:
Fig. 3 is a kind of specific implementation form according to the schematic diagram of Fig. 1.One end of drive signal links to each other with first resistance R 1, second resistance R 2; The other end of drive signal links to each other with the 3rd resistance R 3, the 4th resistance R 4; The other end of second resistance R 2 links to each other with first capacitor C 1, (perhaps the other end of second resistance R 2 directly meets output A to another termination output A of C1, cancellation C1, as dotted line indication among Fig. 3 with the C1 short circuit), the drain electrode of output A end while with the first N-channel MOS FET (VT1) links, the source electrode of the anode of the anode of the source electrode of VT1 and the first voltage-stabiliser tube VD1, the second voltage-stabiliser tube VD2, the second N-channel MOS FET (VT2) is connected in the SR-GND end, and the source electrode of external synchronous rectifier that drives of this end and synchronous freewheeling pipe is the place altogether.As previously mentioned, the other end of first resistance R 1 links to each other with the negative electrode of the second voltage-stabiliser tube VD2, the grid of the second N-channel MOS FET (VT2); The other end of the 3rd resistance R 3 links to each other with the negative electrode of the first voltage-stabiliser tube VD1, the grid of the first N-channel MOS FET (VT1); The drain electrode of the second N-channel MOS FET (VT2) connects output terminals A ', A ' links to each other with an end of second capacitor C 2 simultaneously, the other end of second capacitor C 2 links to each other with the other end of the 4th resistance R 4 and (perhaps cancels capacitor C 2, with the C2 short circuit, A ' end directly links to each other with the other end of aforementioned the 4th resistance R 4 as dotted line indication among Fig. 3).
Need to prove, according to drive signal synchronous signal (referring to Phase synchronization), the corresponding respectively grid that drives synchronous freewheeling pipe and synchronous rectifier of the output terminals A of this circuit, A '.The shared source electrode of synchronous rectifier and synchronous freewheeling pipe is total to the place, links to each other with the SR-GND end of this circuit; The first voltage-stabiliser tube VD1 and the second underwater pipeline stabilizing VD2 rise in circuit and make of there being two: 1. driving voltage back clamping between the grid source electrode of the grid source electrode of couple first N-channel MOS FET (VT1) and the second N-channel MOS FET (VT2), and the control signal path is provided; 2. protect that positive drive voltage is no more than rated value between the grid source electrode of the grid source electrode of the first N-channel MOS FET (VT1) and the second N-channel MOS FET (VT2).Under the enough big situation of drive signal amplitude, circuit shown in Figure 3 is out of shape a little, can obtain another implementation shown in Figure 4.This mode has the advantages that the electric charge maintenance drives, can be under the single-ended converter main transformer shifts to an earlier date reset case, be applied in the secondary synchronous rectification driving circuit, by keeping electric charge, continue the conducting of holding power pipe, reduce the loss of output current, raise the efficiency because of producing by diode in the power body.Former in addition limit is responsible for because the resetting in advance of main transformer, has reduced withstand voltage before opening, and the switching loss that therefore former limit is responsible for has also reduced.
Another kind of specific implementation form shown in Figure 4 is: an end of drive signal links to each other with first resistance R 1, second resistance R 2; The other end of drive signal links to each other with the 3rd resistance R 3, the 4th resistance R 4; The other end of second resistance R 2 links to each other with first capacitor C 1, the anode of the other end of C1 and the 4th diode VD4, the negative electrode of the 3rd diode VD3 links to each other, the negative electrode of the 4th diode VD4 connects output A end, the drain electrode of exporting the A end and the first N-channel MOS FET (VT1) simultaneously links, the source electrode of the anode of the anode of the source electrode of VT1 and the first voltage-stabiliser tube VD1, the second voltage-stabiliser tube VD2, the second N-channel MOS FET (VT2), the anode of the 3rd diode VD3 are connected in the SR-GND end, and the source electrode of external synchronous rectifier that drives of this end and synchronous freewheeling pipe is the place altogether.As previously mentioned, the other end of first resistance R 1 links to each other with the negative electrode of the second voltage-stabiliser tube VD2, the grid of the second N-channel MOS FET (VT2); The other end of the 3rd resistance R 3 links to each other with the negative electrode of the first voltage-stabiliser tube VD1, the grid of the first N-channel MOS FET (VT1); The drain electrode of the second N-channel MOS FET (VT2) connects output terminals A ', A ' links to each other with an end of second capacitor C 2 simultaneously, and the other end of second capacitor C 2 links to each other with the other end of the 4th resistance R 4.This scheme also can be cancelled capacitor C 1 and C2, on the circuit directly with its short circuit, as shown in phantom in Figure 4.
For the single-ended flyback converter,, therefore also just saved continuous current circuit, as long as the drive signal of synchronous rectifier is provided, specifically as shown in Figure 5 because output does not need energy storage inductor.
Fig. 5 is the third specific implementation form: a termination first resistance R 1 of drive signal, and the other end of R1 links to each other with the negative electrode of the second voltage-stabiliser tube VD2, the grid of the second N-channel MOS FET (VT2); Another termination the 3rd resistance R 3 and the 4th resistance R 4 of drive signal; The negative electrode of another termination first diode VD1 of the 3rd resistance R 3; The source electrode of the anode of the anode of the first diode VD1, the second diode VD2, the second N-channel MOS FET (VT2) connects holds SR-GND commonly, and this holds output to connect the source electrode of the synchronous rectifier that drives altogether; The one termination output A ' of the drain electrode of the second N-channel MOS FET (VT2), second capacitor C 2, A ' output connects the grid of the synchronous rectifier that drives; The other end of second capacitor C 2 links to each other with the other end of the 4th resistance R 4.This scheme also can be cancelled capacitor C 2, on the circuit directly with its short circuit, as shown in phantom in Figure 5.
Fig. 6 is the embodiment that is applied in the single-ended active-clamp converter, is example with former limit booster type active-clamp in this example, can also be applied to single-ended converter topologys such as former limit voltage-dropping type active-clamp.
Frame of broken lines 100 indications are the circuit described in Fig. 3 among Fig. 6, indication drive signal part among Fig. 3, the winding n3 by main transformer T1 in Fig. 6 provides, if signal amplitude allows certainly, also can be directly provide, not necessarily leave no choice but adopt independently auxiliary winding n3 by the main winding n2 of T1.The former limit winding n1 one termination input power supply of T1, the drain electrode of a termination N raceway groove main switch VT5 and the end of clamping capacitance C3.The drain electrode of another termination P raceway groove clamper tube VT6 of C3 electric capacity.The source electrode of VT5 and VT6 connects input ground.Control and drive part 101 offer the signal of main switch VT5 and a pair of complementary conducting of clamp switch pipe VT6, shutoff.When VT5 opens, main transformer T1 excitation is transmitted energy to secondary simultaneously, VT6 conducting when VT5 turn-offs, clamping capacitance C3 goes up the voltage that keeps T1 is resetted, and is that VT6 turn-offs the VT5 conducting then.
The synchronous commutation self-driving circuit operation principle (see figure 6) of single-ended forward converter:
When the VT5 conducting, main transformer T1 forward excitation is simultaneously by secondary winding n2 output energy, main transformer T1 each winding n1, n2, n3 end of the same name are for just, the output current of winding n3 has two paths: 1. the electric current resistance R 3 of flowing through, give the grid source electrode charging of VT1, get back to the non-same polarity of winding n3 by the parallel branch of VD2, R1 and VT1, C1, R2 then, make VT1 open-minded, VT2 turn-offs; 2. electric current acts on the grid source electrode of synchronous rectifier VT4 by R4, gets back to the non-same polarity of winding n3 then by VD2, R1 and VT1, C1, R2 parallel branch, makes synchronous rectifier VT4 conducting, and synchronous freewheeling pipe VT3 turn-offs; Because the grid source electric charge of small-power MOSFET (VT1) is little more than synchronous rectifier VT4, by selecting what suitable resistance value of R3, R4, can make speed that the conducting of VT1 and VT2 turn-off conducting speed faster than synchronous rectifier VT4, control electric charge in the grid source of synchronous freewheeling pipe VT3 can quicken discharge by VT1 like this, guarantee that synchronous freewheeling pipe VT3 in time turn-offs when winding n2 forward conduction, synchronous rectifier VT4 is in time open-minded simultaneously.
When VT5 turn-offs, the VT6 conducting, main transformer T1 winding oppositely resets, drive winding n3 and induce reverse voltage, electric current flows out from the non-same polarity of n3, and two loops are arranged equally: 1. the electric current resistance R 1 of flowing through, give the grid source electrode charging of VT2, get back to the end of the same name of winding n3 then by the parallel branch of VD1, R3 and VT2, R4, make VT2 open-minded, VT1 turn-offs; 2. electric current acts on the grid source electrode of synchronous freewheeling pipe VT3 by R2, C1, gets back to the end of the same name of winding n3 then by the parallel branch of VD1, R3 and VT2, R4; Because the grid source electric charge of small-power MOSFET (VT2) is little more than synchronous freewheeling pipe VT3, by selecting the suitable resistance value of R1, R2, can make the conducting of VT2, the turn-off speed of VT1 is faster than the conducting speed of synchronous freewheeling pipe VT3, control electric charge in the grid source of synchronous rectifier VT4 can quicken discharge by VT2 like this, guarantee that synchronous rectifier VT4 in time turn-offs when winding n2 reverse-conducting, synchronous freewheeling pipe VT3 is in time open-minded simultaneously.
When the former limit of single-ended forward converter adopts capacitor resonance to reset, the former limit of main transformer T1 winding n1 can reset in the shutoff cycle of main switch VT5 in advance, the induced voltage that n3 drives winding can drop to zero, synchronous freewheeling Guan Yin can not get enough driving voltages and turn-offs, the freewheel current of outputting inductance L1 can be by the endobiosis diode of VT3, thereby loss is increased, and efficient reduces.The self-driven way of realization of another kind shown in Figure 4 has the advantages that electric charge keeps driving, and Fig. 7 is Fig. 4 circuit is realized synchronous rectification under the capacitor resonance reset case of the former limit of single-end ortho-exciting a specific embodiment.
Frame of broken lines 103 parts are exactly Fig. 4 indication circuit among Fig. 7.Former limit main switch is VT5 and the former limit of main transformer T1 winding n1 polyphone, and C3 is a resonant capacitance.Control and drive circuit 102 produce pwm signal, control turning on and off of main switch.Be responsible for blocking interval, the reverse resonance of resonant capacitance and n1, main transformer resets in advance at person in charge VT5 blocking interval, and at this moment because VD4 oppositely ends, and electric charge remains unchanged between the last grid source electrode of synchronous freewheeling pipe VT3, the synchronous freewheeling pipe can be kept the continuation conducting; To be responsible for VT5 open-minded when former limit, finishes secondary afterflow state, drives winding n3 end of the same name and just be output as, and by the grid source electrode of R3, VT1, and then impels the VT1 conducting by VD2, R1 with the parallel branch of VD3, C1, R2, and synchronous freewheeling pipe VT3 quickens shutoff.Also can be on R3 shunt capacitance C4 (as shown in Figure 7), make the conducting of VT1 suitably leading with respect to VT4, synchronous freewheeling pipe VT3 ends when n2 winding forward is exported fully, reduces short circuit loss.The forward of synchronous rectifier VT4 is opened the loop: driving winding end of the same name n3 this moment just is output as, electric current flow through the grid source electrode of R4, synchronous rectifier VT4, get back to the non-same polarity of n3 by the parallel branch of VD2, R1 and VD3, C1, R2 then, make synchronous rectifier VT4 conducting.
Single end flyback converter is different from single-end ortho-exciting, and output no longer needs energy storage inductor, so has not also just needed the synchronous freewheeling pipe on the circuit.According to theory diagram 2, do suitably to simplify, obtain Fig. 5 specific implementation, Fig. 8 is the specific embodiment of Fig. 5 indication circuit in the single-ended flyback converter.
Frame of broken lines indication 104 parts are exactly Fig. 5 circuit among Fig. 8.Control and drive circuit 102 produce pwm signal, control main switch VT5 turns on and off, when VT5 opened, main transformer drove winding n3 end of the same name and just is output as, and the electric current positive flow is through R1, act on the grid source electrode of N-channel MOS FET VT2, flow back to the non-same polarity of n3 again through VD1, R3 and VT2, R4, therefore and open-minded, synchronous rectifier VT4 turn-offs N-channel MOS FET VT2, the output of blocking-up main transformer T1 secondary winding n2, main transformer is by former limit n1 winding storage power.When VT5 turn-offs, driving winding n3 non-same polarity just is output as, VT2 is owing to the conducting of VD2 is turn-offed, driving voltage acts on the grid source electrode of the VT4 of synchronous rectifier by R4, get back to the end of the same name of winding n3 then by VD2, R1, therefore and open-minded synchronous rectifier VT4 realizes the synchronous rectification of single end flyback converter output.
The advantage of this circuit is: the grid source control voltage of synchronous freewheeling pipe VT4 has the advantages that the electric charge maintenance drives, and the grid source control voltage of synchronous rectifier can only be released by VT2, and synchronous rectifier can obtain stable driving voltage like this; Synchronous rectifier does not have negative voltage to drive, reduce drive loss, control the shutoff of synchronous rectifier by the conducting of control VT2, can the turn-off time of synchronous rectifier be optimized, for example can also be on R1 resistance and capacitor C 4, the ON time that can control VT2 is suitably leading, thus the turn-off time of control synchronous rectifier VT4 is suitably leading, reduce the turn-on consumption of former limit switching tube, improve the efficient of converter.
Claims (5)
1, a kind of synchronous commutation self-driving circuit that is applied to single-end conversion is characterized in that, comprises with the lower part: drive signal, second is quickened breaking circuit, second delay circuit, synchronous rectifier and maintenance loop;
The source S R-GND of the grid A ' of the described synchronous rectifier of one termination of the described second acceleration breaking circuit output, the described synchronous rectifier of another termination of output, the other end of the described drive signal of control termination; Give between the described synchronous rectifier grid source electrode a low-impedance discharge loop is provided, quicken the turn-off time of described synchronous rectifier;
The output of described second delay circuit drives the grid A ' of described synchronous rectifier, provides and control the drive current of described synchronous rectifier, regulates the service time of described synchronous rectifier;
Described drive signal one termination second is quickened the control end of breaking circuit; The input of described second delay circuit of its another termination; Provide and the synchronous drive signal of the former limit of single-ended reverse exciting switch change-over;
Described synchronous rectifier source electrode point is SR-GND.
2, the synchronous commutation self-driving circuit that is applied to single-end conversion according to claim 1, it is characterized in that, described drive signal and main winding are synchronous, and by the winding generation of an independent coupling, drive voltage amplitude can be adjusted umber of turn as required and realize.
3, the synchronous commutation self-driving circuit that is applied to single-end conversion according to claim 2 is characterized in that, if the voltage that the output main winding of secondary side produces is suitable, also can directly take from it.
4, the synchronous commutation self-driving circuit that is applied to single-end conversion according to claim 1, it is characterized in that, comprise that also keeps a loop, described maintenance loop input termination SR-GND, the described drive signal of output termination offers described second and quickens current path of breaking circuit control end and electric charge maintenance.
5, the synchronous commutation self-driving circuit that is applied to single-end conversion according to claim 1 is characterized in that, for single-ended forward converter, comprises that also first quickens breaking circuit, first delay circuit and synchronous freewheeling pipe;
The source S R-GND of the grid A of the described synchronous freewheeling pipe of one termination of the described first acceleration breaking circuit output, the described synchronous freewheeling pipe of another termination of output, an end of the described drive signal of control termination; Give between the described synchronous freewheeling pipe grid source electrode a low-impedance discharge loop is provided, quicken the turn-off time of described synchronous freewheeling pipe;
The output of described first delay circuit drives the grid A of described synchronous freewheeling pipe, provides and control the drive current of described synchronous freewheeling pipe, regulates the service time of described synchronous freewheeling pipe.
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| CNB2004100917676A CN100440704C (en) | 2004-11-26 | 2004-11-26 | Synchronous commutating self-driving circuit for single-end conversion |
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| CNB2004100917676A CN100440704C (en) | 2004-11-26 | 2004-11-26 | Synchronous commutating self-driving circuit for single-end conversion |
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| CN100440704C CN100440704C (en) | 2008-12-03 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101267158B (en) * | 2008-01-23 | 2010-08-04 | 中兴通讯股份有限公司 | Synchronous commutation self-driving circuit |
| CN101527511B (en) * | 2009-01-05 | 2012-05-30 | 崇贸科技股份有限公司 | Synchronous rectifier circuit |
| CN109698613A (en) * | 2017-10-19 | 2019-04-30 | 浙江大学 | A kind of driving circuit of driving circuit and full-bridge synchronous rectification |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8542507B2 (en) * | 2010-06-11 | 2013-09-24 | System General Corp. | Adaptive synchronous rectification control method and apparatus |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000152623A (en) * | 1998-11-10 | 2000-05-30 | Ricoh Co Ltd | Power unit |
| US6038148A (en) * | 1998-12-11 | 2000-03-14 | Ericsson, Inc. | Self-driven synchronous rectification scheme |
| US6275401B1 (en) * | 2000-01-10 | 2001-08-14 | Power-One, Inc. | Self-driven synchronous rectification circuit for low output voltage DC-DC converters |
| CN1144346C (en) * | 2000-08-17 | 2004-03-31 | 伊博电源（杭州）有限公司 | New self-driving circuit of synchronous rectifier tube |
| CN100338864C (en) * | 2003-10-20 | 2007-09-19 | 艾默生网络能源有限公司 | DC/DC converter synchronous rectification circuit |
| CN100388609C (en) * | 2003-10-24 | 2008-05-14 | 中兴通讯股份有限公司 | Driving device of synchronous rectifier transistor |
-
2004
- 2004-11-26 CN CNB2004100917676A patent/CN100440704C/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101267158B (en) * | 2008-01-23 | 2010-08-04 | 中兴通讯股份有限公司 | Synchronous commutation self-driving circuit |
| CN101527511B (en) * | 2009-01-05 | 2012-05-30 | 崇贸科技股份有限公司 | Synchronous rectifier circuit |
| CN109698613A (en) * | 2017-10-19 | 2019-04-30 | 浙江大学 | A kind of driving circuit of driving circuit and full-bridge synchronous rectification |
Also Published As
| Publication number | Publication date |
|---|---|
| CN100440704C (en) | 2008-12-03 |
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