CN201430532Y - A zero-voltage switch flyback DC-DC power conversion device - Google Patents
A zero-voltage switch flyback DC-DC power conversion device Download PDFInfo
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- CN201430532Y CN201430532Y CN2009201220573U CN200920122057U CN201430532Y CN 201430532 Y CN201430532 Y CN 201430532Y CN 2009201220573 U CN2009201220573 U CN 2009201220573U CN 200920122057 U CN200920122057 U CN 200920122057U CN 201430532 Y CN201430532 Y CN 201430532Y
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Abstract
本实用新型涉及一种直流/直流电源变换装置，特别是高效率转换以及轻载下的高效率转换以及低的待机功耗的一种零电压开关反激式直流－直流电源转换装置。反激电路上增加一个辅助开关以及吸收电容，辅助开关与吸收电容相串联组成辅助支路，所述辅助支路可并联在变压器原边绕组两端，也可以并联在原边开关两端，辅助开关仅在原边开关导通前导通一段设定的时间。本实用新型相对于现有技术，线路漏感的能量被吸收后传输到输出端以及用来实现原边开关的软开关，电路的效率可以大大提高；漏感引起的寄生振荡被抑制，电路的EMI特性可以改善；电路的控制更加简单，可以大大提高电路在轻载的效率，降低空载下的损耗。
The utility model relates to a DC/DC power conversion device, in particular to a zero-voltage switch flyback DC-DC power conversion device with high efficiency conversion, high efficiency conversion under light load and low standby power consumption. An auxiliary switch and absorption capacitor are added to the flyback circuit. The auxiliary switch and the absorption capacitor are connected in series to form an auxiliary branch. The auxiliary branch can be connected in parallel at both ends of the transformer primary winding or at both ends of the primary switch. Turns on for a set period of time only before the primary switch turns on. Compared with the prior art, the utility model transmits the energy of the leakage inductance of the line to the output terminal after being absorbed and is used to realize the soft switch of the primary side switch, and the efficiency of the circuit can be greatly improved; the parasitic oscillation caused by the leakage inductance is suppressed, and the circuit EMI characteristics can be improved; the control of the circuit is simpler, which can greatly improve the efficiency of the circuit at light load and reduce the loss at no load.
Description
Technical field
The utility model relates to a kind of DC-DC electric power conversion apparatus, particularly the Zero-voltage switch flyback-type DC-DC power conversion equipment of high efficiency conversion under high efficiency conversion and the underloading and low stand-by power consumption.
Background technology
DC/DC conversion is one of the most basic transformation of electrical energy form.Anti exciting converter is widely used in small-power DC/DC conversion, usually below 100～200W owing to characteristics such as its topology are simple, and components and parts are few.The loss of anti exciting converter mainly comprises the loss of former limit switch, and the loss of transformer absorbs the loss of circuit and the loss of secondary rectifier, and the control mode of these losses and anti exciting converter is also closely related.
Usually the transformer of anti exciting converter is its stored energy and the critical piece that transmits energy, because the existence of leakage inductance, switching tube on former limit produces bigger spine voltage when turn-offing, need extra absorption circuit to absorb and consume the energy of leakage inductance, absorb circuit as RCD clamp commonly used, but the energy of absorption circuitry consumes makes the efficient of circuit reduce.
In recent years, along with the lasting raising that in the world efficient of power supply product is required, as the Energy Star of the U.S., the efficiency standard of European Union makes power supply conversion efficiency become an emphasis of power supply design again.At present, the requirement of efficient is not only at full load conditions, equally also at the efficient under other various loading conditions, usually need be under 25%/50%/75%/100% loading condition, and the mean value of the efficient that records need satisfy standard.Therefore, the efficient that how to improve under the underloading condition also becomes a key.And under no-load condition, the idling consumption of converter requires minimum, requires less than 0.3W a perhaps littler numerical value usually.
The anti exciting converter of traditional fixed frequency because switching frequency is fixed, therefore under underloading and waiting condition, can't satisfy present standard.The more control method is studied and puts forward to be used to improve efficient and to reduce no-load loss.
Aspect raising the efficiency, a kind of method is the active-clamp technology, mainly with the energy absorption of leakage inductance, and utilizes the energy of the energy of magnetizing inductance or leakage inductance to realize the soft switch of former limit switch, raises the efficiency.But this type of switch need increase an auxiliary switch, controls by the complementation of auxiliary switch and former limit switch and realizes, all adopts and decides FREQUENCY CONTROL.
Another method is the conversion efficiency that the mode of employing quasi-resonance (QR) improves power supply, utilize under anti exciting converter work and electric current critical discontinuous mode (Critical DCM) or the discontinuous current pattern (DCM), the parasitic oscillation of magnetizing inductance and former limit switch, be implemented in former limit switch and open or drain-source voltage open-minded when being input voltage, to reduce switching loss in the minimum point of its drain-source voltage (perhaps collector electrode-emitter voltage).Here the electric current of indication is continuous or interrupted, refers to that all the magnetizing inductance electric current of transformer is continuous or interrupted.Adopt the anti exciting converter of quasi-resonance control mode, its switching frequency can change along with the variation of load and input voltage.A kind of commonplace control is the peak value that utilizes load end (outlet side) feedback regulation primary current, thereby the control power output is promptly controlled ON time.Usually, switching frequency uprises along with diminishing of load, be unfavorable for the raising of light-load efficiency and improve electromagnetic interference, need the extra frequency clamp or the pattern of having the hiccups (Burst Mode) to improve underloading and stand-by power consumption usually, the too high electromagnetic interference that causes of control frequency.Another mode is that to keep the peak value of primary current constant, regulates power output by regulating the turn-off time, promptly controls the turn-off time, and like this, frequency reduces along with reducing of load, helps light-load efficiency and stand-by power consumption.But common switching frequency can drop to (below the 20kHz) in the audiorange in unusual underloading, therefore, need avoid producing the noise in the audiorange.
Although adopt the control mode of quasi-resonance can reduce switching loss, in the bigger occasion of input range (as being fit to the interchange scope 90V～265VRMS of global general-use, the DC bus-bar voltage that forms after the rectification, usually at 100V～380VDC), usually under the condition of low input, can realize the soft switch of former limit switch, but under the condition of height input, still there is bigger switching loss.And the energy of transformer leakage inductance still needs to absorb circuit and carries out the clamp absorption.Equally, adopt turn-off time control, utilize the decline of frequency also can reduce switching loss, but under high input voltage or loading condition when changing, still have switching loss.
Adopt at secondary under the situation of synchronous rectifier, utilize the secondary synchronous rectifier can be so that the transformer primary current is reverse, can realize the soft switch of former limit switch, mode by the switching tube shunt capacitance can absorb leakage inductance energy and turn back to input again, realize the harmless absorption of leakage inductance energy, but withstand voltage, the leakage inductance of transformer of the design of capacitance and switching tube and the size of circulating energy are associated difficult design.And make the current reversal of magnetizing inductance realize the soft switch of former limit switch owing to need use the output energy, and the circulating energy of circuit increases, and causes the conduction loss of circuit to increase, and the conduction loss that makes the loss of the absorption circuit saved be increased is traded off.In addition, it is complicated more that the control circuit of synchronous rectifier can seem, prior art adopts the outer mode that drives usually.
For further raising the efficiency the active-clamp circuit of reversed excitation shown in the accompanying drawing 2.By increasing an auxiliary switch Qa, turn-off constantly at former limit switch Q1, the energy absorption of leakage inductance in clamping capacitance Cr, and then is discharged into load or input.Usually switch Q1 and auxiliary switch Qa are operated in complementary state, shown in the gate-drive waveform of accompanying drawing 3 and accompanying drawing 4, be to have no progeny in the Q1 pass, there is a less Dead Time between the two in auxiliary switch Qa conducting in the reality, prevent the generation of the straight-through phenomenon that causes owing to switching characteristic is imperfect, damage circuit, very short comparatively speaking during this period of time, can ignore, this also is a common practise.With the working method according to the transformer excitation inductive current, it is magnetizing inductance electric current unidirectional [1] [4] and magnetizing inductance electric current two-way [2] [3] that 2 working methods can be arranged, respectively shown in accompanying drawing 3 and accompanying drawing 4.Because the on off state complementation of Q1 and Qa, no matter unidirectional or two-way the transformer excitation inductive current is, all is in continuous mode (CCM), therefore in actual applications, adopts the control mode of fixed frequency usually.Although the circuit of reversed excitation of active-clamp can avoid the RCD clamp to absorb circuit, reduce circuit loss.But under the situation that load lightens, because the magnetizing inductance electric current is continuous always, circulating energy is big, causes inefficiency.Have again, in auxiliary switch conduction period, transformer leakage inductance and clamping capacitance resonance, difference between leakage inductance electric current and the exciting curent is sent to output, and relative classical inverse excitation circuit is under the situation of output identical currents, secondary current peak value and effective value are big, cause the secondary conduction loss to become big.In the occasion that is applied to exchange input, under the situation that direct voltage provides by rectification or prime circuit of power factor correction (PFC), when load is light, because the magnetizing inductance electric current is continuous, switching frequency is constant, cause light-load efficiency low, can't satisfy the stand-by power consumption requirement of present requirement, must be when not being with the PFC prime less than 0.3W.Adopt " bursting " (Burst) pattern can reduce stand-by power consumption, for guaranteeing operate as normal, so the control circuit complexity, cause the cost of circuit and the reduction of reliability owing to the control signal of 2 switches need be blocked simultaneously.
Accompanying drawing 5 is anti-sharp current transformers [5] that secondary adopts synchronous rectification.Because secondary adopts synchronous rectification, utilize the energy of output to make the magnetizing inductance current reversal can realize the soft switch of former limit switch Q1.Therefore can be by absorbing the energy (having comprised the parasitic capacitance in the circuit simultaneously) that capacitor C ds absorbs leakage inductance one of the two ends of former limit switch pipe Q1 parallel connection, the RCD clamp on former limit absorbs circuit and can not want.Waveform as shown in Figure 6.This circuit need utilize the output energy to realize the soft switch of former limit switch, so the circulating energy of circuit is bigger.Equally, in the moment that former limit switch turn-offs, transformer leakage inductance produces parasitic oscillation in the shunt capacitance Cds of former limit switch, because the loss resistance that does not add, the decay of vibration relies on the dead resistance of circuit, the amplitude of parasitic oscillation and time are all longer, cause the electromagnetic interference (EMI) degradation of circuit.Therefore, still need an extra RCD clamp as shown in accompanying drawing 1 to absorb circuit usually, but introduced extra loss.Therefore, how further to raise the efficiency, especially underloading and average efficiency, reduce idling consumption is the emphasis of research always.
List of references
[1] Robert Waston, et al, " Utilization of an Active-Clamp Circuit to Achieve Soft Switching inFlyback Converters ", IEEE Trans.On Power Electronics, vol.11, No.1, Jan.1996, pp.162-169 (Robert Wei Sidun etc., " instead swashing in the current transformer utilizes active clamping circuir to realize soft switch ", IEEE power electronics periodical the 11st the 1st phase of volume of January in 1996,162～169 pages);
[2] Koji Yoshida, et al, " Zero Voltage Switching Approach for Flyback Converter ", IEEEINTELEC ' 92, pp.324-329 (the big grade of hole Ji Yuexi people, " instead swash the zero voltage switch method of current transformer ", IEEE INTELEC meeting in 1992 .324-329 page or leaf);
[3] E.H.Wittenbreder, " Zero Voltage Switching Pulse Width Modulated Power Converters ", US Patent 5402329, March 1995 (Wei Dunbulaite, " zero voltage switch pulse-width modulation power converter ", United States Patent (USP) 5402329, March nineteen ninety-five);
[4] David A.Cross, " Clamped Continuous Flyback Power Converter ", USA patent No.5570278, Oct.29,1996 (wear Vikro this, " clamp continuity instead swash current transformer ", United States Patent (USP) in October, 5570278,1996);
[5] M.T.Zhang, Milan M.Javanovic, F.C.Lee, " Design Consideration and PerformanceEvaluations of Synchronous Rectification in Flyback Converters ", IEEE Trans.on PE, Vol.13, No.3, May 1998, pp538～546 (Michael opens etc., " and instead swash the design of synchronous rectifier in the current transformer and Performance Evaluation ", IEEE power electronics periodical, in May, 1998, the 13rd the 3rd phase of volume, 538～546 pages).
The utility model content
The technical problem to be solved in the present invention provides a kind of switching loss that can reduce circuit of reversed excitation, and leakage inductance absorbs circuit loss, the Zero-voltage switch flyback-type DC-DC power conversion equipment that improves light-load efficiency and reduce idling consumption.
In order to overcome the above problems, the utility model provides a kind of Zero-voltage switch flyback-type DC-DC power conversion equipment, comprising:
An input port is accepted DC input voitage, and an output port provides direct current to load;
A transformer comprises a former limit winding and a secondary winding at least;
Former limit switch is in series with the former limit of described transformer winding; During the switch conduction of described former limit, DC input voitage is added to the former limit of described transformer winding, described transformer stored energy; At described former limit switch blocking interval, described DC input voitage and the former limit of described transformer winding disconnect, and the energy that described transformer is stored during the switch conduction of described former limit discharges to load by the secondary winding of described transformer;
Output circuit, the secondary coupling with described voltage device produces a direct current at the energy that described former limit switch blocking interval discharges at described output port with described transformer, offers load;
Also comprise a clamp circuit, comprise an electric capacity, a booster diode and an auxiliary switch, described auxiliary switch and capacitances in series, described booster diode is in parallel with auxiliary switch, the switch blocking interval provides a current path for described transformer on described former limit, described clamp circuit in parallel with the former limit winding of described transformer or with described former limit switch in parallel;
Described auxiliary switch is in the time of described former limit switch conduction setting of conducting before the moment, described auxiliary switch turn-offs the time that shifts to an earlier date the setting constantly of described former limit switch conduction constantly, at described former limit switch conduction constantly, the voltage that described former limit switch bears is close to zero.
Further, described former limit switch or auxiliary switch are metal oxide semiconductor field-effect, igbt or bipolar transistor.
Further, described booster diode is the parasitic diode of described auxiliary switch.
Further, the constantly leading described former limit of the described auxiliary switch conducting switch conduction time constantly is fixing or sets.
Further, described auxiliary switch ON time is less than the described former limit switch turn-off time; Described auxiliary switch is booster diode not conducting of conduction period in described clamp circuit;
Further, the exciting curent of described transformer is operated in on-off state or continuous state;
Further, described output port comprises a rectifying device, breaks anti-Pianguan County in the time at described former limit switch conduction, in the turn-off time, allows electric current to pass through at described former limit switch.
Further, the energy that absorbed in described booster diode conduction period of the electric capacity in the described clamp circuit is discharged to load and direct-flow input end by described transformer leakage inductance by described auxiliary switch conduction device.
Further, described rectifying device is a diode.
Further, the adjusting of output is by the ON time of control described former limit switch, and the duty ratio of controlling the turn-off time of described former limit switch or controlling the conducting of described former limit switch is regulated.
Below the utility model will be further described:
A kind of Zero-voltage switch flyback-type DC-DC power conversion equipment comprises:
An input port is accepted DC input voitage, and an output port provides direct current to load;
A transformer comprises a former limit winding and a secondary winding at least;
Former limit switch is in series with the former limit of described transformer winding; During the switch conduction of described former limit, DC input voitage is added to the former limit of described transformer winding, described transformer stored energy; At described former limit switch blocking interval, described DC input voitage and the former limit of described transformer winding disconnect, and the energy that described transformer is stored during the switch conduction of described former limit discharges to load by the secondary winding of described transformer;
Output circuit, the secondary coupling with described voltage device produces a direct current at the energy that described former limit switch blocking interval discharges at described output port with described transformer, offers load;
A clamp circuit, comprise an electric capacity, a booster diode and an auxiliary switch, described auxiliary switch and capacitances in series, described booster diode is in parallel with auxiliary switch, and the switch blocking interval provides a current path for described transformer on described former limit.Described clamp circuit in parallel with the former limit winding of described transformer or with described former limit switch in parallel;
Described auxiliary switch is in the time of described former limit switch conduction setting of conducting before the moment, described auxiliary switch turn-offs the time that shifts to an earlier date the setting constantly of described former limit switch conduction constantly, at described former limit switch conduction constantly, the voltage that described former limit switch bears is close to zero.
Further, described former limit switch or auxiliary switch can be metal oxide semiconductor field-effect (MOSFET), also can be igbts (IGBT), also can be bipolar transistors (BJT); Described booster diode can be the parasitic diode of described auxiliary switch;
The constantly leading described former limit of the described auxiliary switch conducting switch conduction time constantly is fixing or sets, and ON time or the turn-off time with described former limit switch changes, also not with the conducting change in duty cycle of described former limit switch; Described auxiliary switch ON time is less than the described former limit switch turn-off time; Described auxiliary switch is booster diode not conducting of conduction period in described clamp circuit;
Wherein, the exciting curent of described transformer is operated in on-off state or continuous state; Described transformer can be that a plurality of transformers are in series or parallel connection.
Further, described output circuit comprises a rectifying device, breaks anti-Pianguan County in the time at described former limit switch conduction, in the turn-off time, allows electric current to pass through at described former limit switch.
The energy that electric capacity in the described clamp circuit was absorbed in described booster diode conduction period discharges to load and direct-flow input end by described transformer leakage inductance at described auxiliary switch conduction device.
Described rectifying device is a diode, can be metal oxide semiconductor field-effect (MOSFET).Further, the adjusting of output is by the ON time of control described former limit switch, and the duty ratio of controlling the turn-off time of described former limit switch or controlling the conducting of described former limit switch is regulated.
The DC input voitage of described input port can be that the interchange of electrical network obtains, also can be the direct voltage of other change-over circuit outputs through diode rectifier circuit, described DC input voitage can be constant, also bigger mobility scale can be arranged, as 3～5 times variation.
Circuit structure that the utility model adopted and control mode thereof, with respect to prior art, tangible advantage is arranged, the soft switch (zero voltage switch that is transferred to output after the energy of circuit leakage inductance is absorbed and is used for realizing former limit switch, ZVS), the efficient of circuit can improve greatly; The parasitic oscillation that leakage inductance causes is suppressed, and the EMI characteristic of circuit can be improved; Equally,, also can be operated in the discontinuous current mode, make that the control of circuit is simpler, can improve the efficient of circuit greatly, reduce the loss under the zero load in underloading because magnetizing inductance promptly can be operated in the electric current continuous state.
Description of drawings
Fig. 1 band RCD clamp absorbs the circuit of reversed excitation figure of circuit;
Fig. 2 active-clamp circuit of reversed excitation figure;
The working waveform figure of Fig. 3 active-clamp circuit of reversed excitation under the magnetizing inductance electric current is unidirectional;
The working waveform figure of Fig. 4 active-clamp circuit of reversed excitation under the magnetizing inductance electric current is two-way;
Fig. 5 secondary adopts the circuit of reversed excitation figure (former limit does not have the RCD clamp and absorbs circuit) of synchronous rectification;
Fig. 6 secondary adopts the circuit of reversed excitation working waveform figure (former limit does not have the RCD clamp and absorbs circuit) of synchronous rectification;
Fig. 7 circuit structure diagram of the present utility model;
Gate pulse sequential chart and working waveform figure under Fig. 8 specific embodiment CCM mode of the present utility model;
Gate pulse sequential chart and working waveform figure under Fig. 9 another specific embodiment of the present utility model DCM mode;
Waveform schematic diagram under Figure 10 circuit of reversed excitation VF DCM working method (QR working method);
The waveform schematic diagram of embodiment of Figure 11 the utility model under VF DCM working method (QR working method);
Embodiment of Figure 12 the utility model realizes the waveform schematic diagram that peak point is opened under VF DCM working method;
The circuit diagram that Figure 13 peak point detects;
An auxiliary branch embodiment schematic diagram in parallel in Figure 14 the utility model with switching tube;
Be applied to a plurality of transformer tandem junction compositions (output series connection) in Figure 15 the utility model;
Be applied to a plurality of transformer tandem junction compositions (output-parallel) in Figure 16 the utility model.
Embodiment
Below in conjunction with accompanying drawing the utility model is done detailed description.By description to the utility model specific embodiment, easy to understand feature of the present utility model and details more.This paper does not describe known execution mode and operational means in detail, in order to avoid obscure various technology implementation scheme of the present utility model, still, the technical staff that ability is got over, lack one or more concrete details or assembly, do not influence understanding of the present utility model and enforcement.
This specification described " embodiment " or " embodiment " are meant in conjunction with the embodiments concrete feature, structure, execution mode and the characteristics of describing among at least one embodiment of the present utility model of being included in.Therefore, when mentioning " in one embodiment ", may not refer to same embodiment in the different places of specification.These features, structure or characteristic can be in any suitable manner in conjunction with in one or more embodiments.
Circuit diagram of a specific embodiment of the present utility model (accompanying drawing 7) and distinctive control strategy (accompanying drawing 8) thereof comprise a former limit switch Q1 and a former limit auxiliary switch Qa among the figure.Electrical block diagram shown in the accompanying drawing 7 and accompanying drawing 2 are of equal value, and auxiliary switch Qa is a N type field effect transistor MOSFET.Be different from the control mode shown in accompanying drawing 3 or the accompanying drawing 4, former here limit switch Q1 is not complementary work in auxiliary switch Qa, Qa only before former limit switch Q1 opens a bit of time of conducting open-minded, shown in accompanying drawing 8, accompanying drawing 9.
As shown in Figure 8, t0 constantly before, the switch Q1 conducting of former limit, primary current rises, the transformer storage power, the output rectifier diode ends.At t0 constantly, former limit switch Q1 turn-offs, and at this moment, is stored in the body diode of energy by auxiliary switch Qa among the transformer leakage inductance Lk and stores into and absorb among the capacitor C r.Usually, the capacitance value of Cr is bigger, can regard a constant voltage source as.Because the energy of leakage inductance is absorbed into capacitor C r, the parasitic oscillation that leakage inductance causes is suppressed, and helps to improve the EMI characteristic of circuit.Simultaneously, the energy of magnetizing inductance storage begins to discharge to outlet side by rectifier diode.
At t1 constantly, the energy in the leakage inductance is absorbed by capacitor C r fully, and primary current Ip drops to zero.At this moment, the energy of transformer excitation inductance L m storage is released to outlet side, and the magnetizing inductance electric current is linear to descend.This stage is until till the t2 moment.
At t2 constantly, auxiliary switch Qa conducting, r is to the leakage inductance reverse charging for the absorption capacitor C, and it is negative that primary current Ip becomes, slope that current reversal increases and absorption capacitance voltage V
CrAnd the difference that output voltage is converted the numerical value on former limit is directly proportional, and absorbs energy in the electric capacity and is discharged into load by transformer and is stored in the leakage inductance.Equally, owing to absorb capacitance voltage V
CrAnd the output voltage numerical value of converting former limit differ can be very not big, during auxiliary switch Qa conducting, its drain-source voltage is very little, therefore, auxiliary switch Qa turn-on consumption is very little.
At t3 constantly, auxiliary switch Qa turn-offs, and the energy that is stored in this moment in the leakage inductance discharges to the equivalent parasitic capacitances Cds between the switch Q1 drain-source of former limit, and the equivalent parasitic capacitances Cds between the drain-source described here has comprised other identical parasitic capacitances of effect in the circuit.At t4 constantly, the voltage Vds at Q1 drain-source two ends drops to zero.Former limit switch realization this moment no-voltage is opened (soft switch).In t3～t4 time interval,, be stored in the soft switch that energy in the magnetizing inductance also can help to realize former limit switch Q1 if the magnetizing inductance electrorheological is negative.[t3-t4] constantly is mainly used to realize the soft switch of Q1 and prevents Q1 and Qa common, plays the effect of similar Dead Time.
After the moment, former limit switch is open-minded at t4, and input voltage charges to magnetizing inductance, stored energy, and this stage is identical with traditional anti exciting converter.
In the waveform shown in the accompanying drawing 8, the magnetizing inductance electric current I
LmBe in (CCM mode) under the continuation mode, at t2～t4 in the time period, the magnetizing inductance electric current I
LmCan become negatively, just also can always be, not influence the working attributes of circuit.
Accompanying drawing 9 has shown the magnetizing inductance electric current I
LmBe in the work wave (DCM mode) under the interrupted mode.
Before the moment, the work of circuit is consistent with the front at t1.In period, the magnetizing inductance electric current drops to zero constantly at t2a at t1～t2.In period, the equivalent parasitic capacitances Cds resonance of magnetizing inductance and former limit switch Q1 is waited until t2 auxiliary switch Qa conducting constantly always at t2a～t2.
At t2 constantly, auxiliary switch Q2 conducting is on all four under the course of work after this and the magnetizing inductance continuum of states.It should be noted that constantly the magnetizing inductance electric current I at t3
LmFor negative, can help former limit switch to realize zero voltage switch.Because the magnetizing inductance electric current can be operated under the DCM mode, so its light-load efficiency can improve greatly.
Can see from top analysis, circuit structure that the utility model adopted and control mode thereof with respect to prior art, have tangible advantage, the soft switch that is transferred to output after the energy of circuit leakage inductance is absorbed and is used for realizing former limit switch, the efficient of circuit can improve greatly; The parasitic oscillation that leakage inductance causes is suppressed, and the EMI characteristic of circuit can be improved; Equally,, also can be operated in the discontinuous current mode, make that the control of circuit is simpler, can improve the efficient of circuit greatly, reduce the loss under the zero load in underloading because magnetizing inductance promptly can be operated in the electric current continuous state.
At the auxiliary switch switch control mode that circuit and the utility model proposed shown in the accompanying drawing 7, can be incorporated into existing various circuit of reversed excitation controlling schemes at present.Can adopt the control mode of deciding frequency, promptly the switching frequency of Q1 is (user sets) of fixing.Can adopt the control mode of frequency conversion, promptly the switching frequency of Q1 is not fixing, changes along with the variation of load, input voltage, parameter yet, comprises schemes such as changing ON time and change turn-off time.
In the variable frequency control mode of traditional change ON time, usually wish that circuit working is in the inductive current critical discontinuous mode, for reducing switching loss, after the magnetizing inductance electric current reduces to zero, utilize the vibration of magnetizing inductance and parasitic capacitance, the realization the lowest point is open-minded, is also referred to as VF DCM working method, perhaps quasi-resonance circuit of reversed excitation (QR Flyback).Under the traditional approach, circuit structure is shown in the accompanying drawing 1, and circuit waveform as shown in Figure 10.At t0 constantly, the magnetizing inductance electric current drops to zero, and time-delay or detection mode (being generally half harmonic period of parasitic oscillation) through suitable realize the open-minded of switch Q1 constantly at t1, realizes the open-minded of minimum voltage (being the lowest point).The ON time of Q1 is determined that by feedback element this is a common practise, here no longer narration.Voltage detection mode constantly in the lowest point also has existing techniques in realizing, here no longer narration.Sometimes, in order to prevent that switching frequency is too high under underloading or high input voltage, opening of Q1 can be in the lowest point of the 2nd resonance, as shown in accompanying drawing 10, also can be more, usually realize that by the turn-off time of restriction Q1 promptly the time of t1a to t3 can not be less than some set points in the accompanying drawing 10.Realize at present by a lot of control chips, as the NCP1207A of ONSEMI etc., family chips such as the TEA1552 of NXP.
The control mode that the utility model adopted can adopt VF DCM working method (perhaps quasi-resonance QR mode) equally.As a specific embodiment, as shown in Figure 11, at t0 constantly, magnetizing inductance drops to zero, opens auxiliary switch Qa constantly at t1, preset time of conducting, and then actuating switch Q1.The ON time of Qa is set by circuit, and the ON time of Q1 is determined that by feedback control loop ability is got over the technical staff can realize the control technology that the utility model disclosed by existing chip easily, and waveform as shown in Figure 11.For further improving performance, by changing suitable time-delay or detection mode, detect the peak value of parasitic oscillation, further reduce switching loss, waveform as shown in Figure 12, like this auxiliary switch Qa open switching loss constantly can minimum.A simple mode is by auxiliary winding parasitic oscillation and zero potential to be compared, and the waveform of generation is through suitable time-delay, and trailing edge is exactly the detection of oscillation peak constantly, schematic diagram as shown in Figure 13.Those skilled in the art can obtain the mode that various peak points detect on the basis of existing technology, and this does not influence enforcement of the present utility model.
In the variable frequency control mode that changes the turn-off time, the ON time of Q1 is fixed or is changed (according to the peak current decision by switch Q1 according to setting rule in advance, be that switching current reaches the set point stopcock), feedback element is regulated the turn-off time of former limit switch Q1 and is regulated output voltage or electric current, promptly can be operated in CCM and also can be operated under the DCM mode.Like this, switching frequency lightens along with load and reduces, and can significantly improve light-load efficiency, and under full load conditions, the operating frequency of circuit is the highest.Be operated under the CCM mode, similar with the CCM mode of deciding FREQUENCY CONTROL.Under the DCM mode, work wave and accompanying drawing 12 are similar, and difference is that the ON time of Q1 is predefined, and the turn-off time (time of t1a to t3) is the feedback element decision, and therefore, the conducting of Qa constantly may be at peak point.
As fully visible, the utility model is by a simple circuit, by increasing an auxiliary switch, the time of control auxiliary switch setting of conducting before the switch Q1 conducting of former limit, can realize the soft switch of former limit switch, harmless absorption leakage inductance energy, and with its be delivered to output and input, improve the efficient of circuit, prevent the parasitic oscillation that leakage inductance causes, improve the EMI characteristic of circuit, be applicable to the various control modes of present circuit of reversed excitation, as frequently fixed, the scheme of frequency conversion (regulating ON time or control turn-off time) compared with prior art has tangible advantage.
Auxiliary switch shown in the accompanying drawing 7 is the MOSFET of a N type, auxiliary switch Qa is connected in parallel on the transformer two ends with the auxiliary branch that absorbs capacitor C r composition, those skilled in the art can obtain all kinds of equivalent electric circuits easily, equivalent electric circuit as shown in Figure 14, auxiliary branch is connected in parallel on the switching tube two ends, adopts a P type MOSFET.Auxiliary switch also can be the switch of other types.Requiring of its auxiliary switch Qa and former limit switch Q1 conducting control is constant, and be described consistent with accompanying drawing 8/4C and accompanying drawing 6.
Adopt a transformer as an example among the above embodiment, same, transformer can be that a plurality of transformers are in series, its primary current equates, the energy of each transformer leakage inductance can be absorbed by the capacitor C r shown in the accompanying drawing 7, and the secondary of a plurality of transformers can be connected, also can be in parallel.Accompanying drawing 15,16 has provided the embodiment of 2 transformer primary edge series connection.Those skilled in the art can draw the embodiment of a plurality of transformer series connection equally.
The above-mentioned detailed description of the utility model embodiment be not exhaustive or be used for the utility model be limited in above-mentioned clear and definite in form.Above-mentioned with schematic purpose specific embodiment of the present utility model and example are described in, those skilled in the art will recognize that and can in scope of the present utility model, carry out various equivalent modifications.
The utility model enlightenment provided here is not must be applied in the said system, can also be applied in other system.Element and the effect of above-mentioned various embodiment can be combined so that more embodiment to be provided.
Can make amendment to the utility model according to above-mentioned detailed description, at above-mentioned declarative description specific embodiment of the present utility model and having described in the anticipated optimal set pattern, no matter occur how detailed explanation hereinbefore, also can be implemented in numerous ways the utility model.The details of foregoing circuit structure and control mode thereof is carried out in the details at it can carry out considerable variation, yet it still is included in the utility model disclosed herein.
Should be noted that as above-mentioned that employed specific term should not be used to be illustrated in when explanation some feature of the present utility model or scheme redefines this term here with restriction of the present utility model some certain features, feature or the scheme relevant with this term.In a word, should be with the terminological interpretation in the claims of enclosing, used for the utility model not being limited to disclosed specific embodiment in the specification, unless above-mentioned detailed description part defines these terms clearly.Therefore, actual range of the present utility model not only comprises the disclosed embodiments, also is included in to implement or carry out all equivalents of the present utility model under claims.
Claims (10)
1, a kind of Zero-voltage switch flyback-type DC-DC power conversion equipment comprises:
An input port is accepted DC input voitage, and an output port provides direct current to load;
A transformer comprises a former limit winding and a secondary winding at least;
Former limit switch is in series with the former limit of described transformer winding; During the switch conduction of described former limit, DC input voitage is added to the former limit of described transformer winding, described transformer stored energy; At described former limit switch blocking interval, described DC input voitage and the former limit of described transformer winding disconnect, and the energy that described transformer is stored during the switch conduction of described former limit discharges to load by the secondary winding of described transformer;
Output circuit, the secondary coupling with described voltage device produces a direct current at the energy that described former limit switch blocking interval discharges at described output port with described transformer, offers load;
It is characterized in that: also comprise a clamp circuit, comprise an electric capacity, a booster diode and an auxiliary switch, described auxiliary switch and capacitances in series, described booster diode is in parallel with auxiliary switch, the switch blocking interval provides a current path for described transformer on described former limit, described clamp circuit in parallel with the former limit winding of described transformer or with described former limit switch in parallel;
Described auxiliary switch is in the time of described former limit switch conduction setting of conducting before the moment, described auxiliary switch turn-offs the time that shifts to an earlier date the setting constantly of described former limit switch conduction constantly, at described former limit switch conduction constantly, the voltage that described former limit switch bears is close to zero.
2, Zero-voltage switch flyback-type DC-DC power conversion equipment according to claim 1, it is characterized in that: described former limit switch or auxiliary switch are metal oxide semiconductor field-effect, igbt or bipolar transistor.
3, Zero-voltage switch flyback-type DC-DC power conversion equipment according to claim 1, it is characterized in that: described booster diode is the parasitic diode of described auxiliary switch.
4, Zero-voltage switch flyback-type DC-DC power conversion equipment according to claim 1 is characterized in that: described auxiliary switch conducting is leading constantly, and the described former limit switch conduction time constantly is fixing or sets.
5, Zero-voltage switch flyback-type DC-DC power conversion equipment according to claim 1 is characterized in that: described auxiliary switch ON time is less than the described former limit switch turn-off time; Described auxiliary switch is booster diode not conducting of conduction period in described clamp circuit.
6, Zero-voltage switch flyback-type DC-DC power conversion equipment according to claim 1, it is characterized in that: the exciting curent of described transformer is operated in on-off state or continuous state.
7, Zero-voltage switch flyback-type DC-DC power conversion equipment according to claim 2, it is characterized in that: described output circuit, comprise a rectifying device, break anti-Pianguan County in the time, allow electric current to pass through in the turn-off time at described former limit switch at described former limit switch conduction.
8, Zero-voltage switch flyback-type DC-DC power conversion equipment according to claim 2 is characterized in that: the energy that the electric capacity in the described clamp circuit was absorbed in described booster diode conduction period is discharged to load and direct-flow input end by described transformer leakage inductance by described auxiliary switch conduction device.
9, Zero-voltage switch flyback-type DC-DC power conversion equipment according to claim 8, it is characterized in that: described rectifying device is a diode.
10, Zero-voltage switch flyback-type DC-DC power conversion equipment according to claim 1, it is characterized in that: the adjusting of output is by the ON time of control described former limit switch, or the duty ratio of controlling the turn-off time of described former limit switch or controlling the conducting of described former limit switch is regulated.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2009201220573U CN201430532Y (en) | 2009-06-15 | 2009-06-15 | A zero-voltage switch flyback DC-DC power conversion device |
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| Application Number | Priority Date | Filing Date | Title |
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| CN2009201220573U CN201430532Y (en) | 2009-06-15 | 2009-06-15 | A zero-voltage switch flyback DC-DC power conversion device |
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| CN201430532Y true CN201430532Y (en) | 2010-03-24 |
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