CN1992488A - Synchronous rectification device - Google Patents
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- CN1992488A CN1992488A CN 200510132573 CN200510132573A CN1992488A CN 1992488 A CN1992488 A CN 1992488A CN 200510132573 CN200510132573 CN 200510132573 CN 200510132573 A CN200510132573 A CN 200510132573A CN 1992488 A CN1992488 A CN 1992488A
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Abstract
A synchronous rectifier device includes the transformer, the synchronous rectifier circuit and the synchronous rectifier drive circuit, and the transformer includes the original edge winding and the subsidiary edge winding, the synchronous rectifier circuit and the transformer subsidiary edge winding forming full-wave or times flow synchronous rectifier circuit, including synchronous rectifier tubes VT1 and VT2, and the rectifier drive circuit connects to a subsidiary edge winding and VT1, VT2 gates, and the synchronous rectifier circuit includes two groups driving circuit to respectively provide the driver voltage for VT1 and VT2, each group including the capacitive charge and maintain circuit, and capacitive discharge circuit, the former used to charge the VT1 or VT2 gate-source capacity when the subsidiary edge winding voltage is positive, and maintain the stored electricity when the voltage is zero, and when the voltage is reverse, the capacitor discharge circuit releases the stored electricity, the two drive signals output from the driver circuit are phase complementary. In the invention, the synchronous rectifier device can provide adequate drive voltage for the rectifier tube, to maintain the work efficiency of the power converter.
Description
Technical field
The present invention relates to a kind of rectifying device, relate in particular to the synchronous rectificating device in a kind of DC-DC power converter.
Background technology
Because low pressure and low power field-effect transistor (MOSFET) has very little conducting resistance, the voltage drop that produces when having electric current to flow through is very little, can substitute diode as rectifying device, improve the efficient of DC-DC supply convertor greatly, in the DC-DC converter of low pressure, big electric current, be used widely.When using power MOSFET to make rectifier, the grid voltage between source electrodes must with kept just finishing rectification function synchronously by the phase place of commutating voltage, so the title synchronous rectification.
MOSFET is the voltage-controlled type switching device, must add between its grid-source electrode that driving voltage controls the turn-on and turn-off between its drain electrode and the source electrode.According to its control mode, the drive circuit of synchronous rectification can be divided into it and drive and self-powered two big classes.
The circuit that utilization adds comes that the mode that MOSFET drives is called it and drives, it drives the driving sequential logic that mode realizes meeting the synchronous rectification needs easily, improve the efficient of synchronous rectification, but the control circuit that needs more complicated usually, sometimes also comprise the special driving chip, have circuit complexity, the higher shortcoming of cost, and the loss of drive circuit may make the decrease in efficiency of whole converter on the contrary in middle low power is used.
Utilize on power transformer in the supply convertor or the power inductance winding voltage directly or handle afterwards through ball bearing made using that the mode of driven MOS FET is called self-powered.The self-powered circuit of synchronous rectification has the advantage that circuit is simple, cost is low, and being suitable for after the rectification of the isallobaric device winding voltage waveform of normal shock active-clamp topological sum asymmetrical half-bridge topology is to use in the supply convertor of complementary square wave.But in the supply convertor that the pulse-width modulation (PWM) of incomplementarity waveform is controlled behind some Transformer Winding voltage commutations, as symmetrical half bridge, full-bridge, topology such as recommend, under the little situation of duty ratio, the power transformer winding voltage is zero in the long time period, make the drive signal of MOSFET have big dead band, MOSFET turn-offs because of losing driving voltage, and at this moment load current can flow through the body diode of MOSFET, causes very lossy.In addition, because the body diode reverse of MOSFET is very big recovery time, the turn-off time is long, therefore can cause the transformer secondary short circuit when another MOSFET opens, and has increased the loss and the electromagnetic emission of converter.
Self-driven full-wave rectifying circuit (shown in Figure 1A) and current-doubling rectifier (shown in Figure 1B) with bridge circuit they are example, and Fig. 1 C illustrates the drive waveforms of synchronous rectifier VT1 and VT2 in these two kinds of circuit, wherein, and V
WSBe the waveform of transformer secondary winding voltage, V
GS_VT1And V
GS_VT2It is the drive waveforms of synchronous rectifier VT1 and VT2.As shown in the figure, during voltage on the transformer secondary winding Ws was zero, the driving voltage of VT1 and VT2 was zero, and promptly drive waveforms has the dead band, and the body diode conducting of MOSFET during this period causes the efficient of supply convertor to reduce.
People such as Cobos J.A. APEC ' 99 years can on gate charge conversion driving method (Cobos J.A. has been proposed, Alou P., Garcia O., Uceda J.and Rascon M.New driving Schemefor Self Driven Synchronous Rectifiers.APEC ' 99.Volume:2,1999.Pages:840～846), its circuit theory diagrams are referring to Fig. 2 A.Adopt the gate charge conversion driving method shown in Fig. 2 A can avoid existing in the self-driven circuit of full-wave rectification shown in Figure 1A the problem that drives the dead band.W among Fig. 2 A
SBe transformer secondary winding, W
ATransformer is assisted winding, the drive waveforms of synchronous rectifier such as Fig. 2 B in this circuit.From Fig. 2 A and 2B as can be seen, (the T among the figure when transformer secondary winding voltage is zero
h), synchronous rectifier VT1 and VT2 all have driving voltage, the conducting that can keep MOSFET, but because the dividing potential drop effect of the grid source electric capacity of two MOSFET, the driving voltage that VT1 and VT2 obtain only is half of normal drive voltage (being transformer secondary winding voltage amplitude in the drawings), driving voltage is still too low in some applications, influences supply convertor efficient.
Summary of the invention
Technical problem to be solved by this invention provides a kind of DC-DC power converter, can provide enough driving voltages for rectifying tube, keeps the operating efficiency of supply convertor.
In order to solve the problems of the technologies described above, the invention provides a kind of synchronous rectificating device, comprise transformer, circuit of synchronous rectification and synchronous rectification driving circuit, described transformer comprises former limit winding and one or more secondary winding, described circuit of synchronous rectification and transformer secondary winding have been formed all-wave or using current double synchronous rectifier circuit together, comprise the first synchronous rectifier VT1 and the second synchronous rectifier VT2, described synchronous rectification driving circuit is electrically connected to the grid of two synchronous rectifiers in a secondary winding and the described circuit of synchronous rectification, one side of this secondary winding has splicing ear A, another side has splicing ear B, it is characterized in that
Described synchronous rectification driving circuit comprises and is respectively two groups of drive circuits that VT1 and VT2 provide driving voltage, every group of drive circuit comprises an electric capacity charging and electric charge holding circuit and a capacitor discharging circuit, the charging of described electric capacity and electric charge holding circuit are the grid source electric capacity charging of respective synchronization rectifying tube in transformer secondary winding voltage during for forward, provide synchronous rectifier required driving voltage, and when the secondary winding voltage is zero, maintain the electric charge that stores between described grid, source electrode; When the Transformer Winding voltage reversal, described capacitor discharging circuit discharges the electric charge that stores between described synchronous rectifier grid, source electrode, avoids VT1 and VT2 conducting simultaneously, and, the two-way drive signal phase place complementation of two groups of drive circuit outputs.
Further, above-mentioned synchronous rectificating device also can have following characteristics: first group of drive circuit in the described synchronous rectification driving circuit is included as the electric capacity charging of VT1 grid source and plays the first diode VD1 of electric charge maintenance effect, and be the first auxiliary switch S1 of VT1 grid source capacitor discharge, sun level and the negative electrode of VD1 are electrically connected to the splicing ear A of described secondary winding and the grid of VT1 respectively, S1 is connected in parallel on the grid, source electrode of VT1, and the control utmost point of S1 is electrically connected to described secondary winding; Second group of drive circuit is included as the second diode VD2 that VT2 grid source electric capacity charges and plays electric charge maintenance effect, and be the second auxiliary switch S2 of VT2 grid source capacitor discharge, the anode of VD2 and negative electrode are electrically connected to the splicing ear B of described secondary winding and the grid of VT2 respectively, S2 is connected in parallel on the grid, source electrode of VT2, and the control utmost point of S2 is electrically connected to described secondary winding.
Further, above-mentioned synchronous rectificating device also can have following characteristics: described secondary winding also comprises a centre cap, the source electrode of VT1 and VT2 all is electrically connected on this centre cap, the control utmost point of S1 is electrically connected to the splicing ear B of secondary winding, and the control utmost point of S2 is electrically connected to the splicing ear A of secondary winding.
Further, above-mentioned synchronous rectificating device also can have following characteristics: described auxiliary switch S1 and S2 are N-channel MOS FET, the drain electrode of S1 is electrically connected to the grid of VT1, the grid of S1 is electrically connected to the splicing ear B of described secondary winding, the drain electrode of S2 is electrically connected to the grid of VT2, the grid of S2 is electrically connected to the splicing ear A of described secondary winding, and the source electrode of S1 and S2 all is electrically connected to described centre cap.
Further, above-mentioned synchronous rectificating device also can have following characteristics: first group of drive circuit in the described synchronous rectification driving circuit is included as the electric capacity charging of VT1 grid source and plays the first diode VD1 of electric charge maintenance effect, and be the first auxiliary switch S1 of VT1 grid source capacitor discharge, the anode of VD1 and negative electrode are electrically connected to the splicing ear A and the VT1 grid of described secondary winding respectively, S1 is in parallel with VD1, and the S1 control utmost point is electrically connected to described secondary winding; Second group of drive circuit is included as the second diode VD2 that VT2 grid source electric capacity charges and plays electric charge maintenance effect, and be the second auxiliary switch S2 of VT2 grid source capacitor discharge, the anode of VD2 and cathodic electricity are connected to the splicing ear B and the VT2 grid of described secondary winding, S2 is in parallel with VD2, and the S2 control utmost point is electrically connected to described secondary winding.
Further, above-mentioned synchronous rectificating device also can have following characteristics: described secondary winding also comprises a centre cap, and the control utmost point of the source electrode of described VT1 and VT2, S1 and S2 all is electrically connected on this centre cap.
Further, above-mentioned synchronous rectificating device also can have following characteristics: described auxiliary switch S1 and S2 are N-channel MOS FET, and described VD1 and VD2 serve as with the body diode of described S1 and S2 respectively; The drain electrode of S1 is electrically connected to the grid of VT1, the source electrode of S1 is electrically connected to the splicing ear A of described secondary winding, the drain electrode of S2 is electrically connected to the grid of VT2, and the source electrode of S2 is electrically connected to the splicing ear B of described secondary winding, and the grid of S1 and S2 all is electrically connected to described centre cap.
Further, above-mentioned synchronous rectificating device also can have following characteristics: described auxiliary switch S1 and S2 are N-channel MOS FET, and described VD1 and VD2 serve as with the body diode of described S1 and S2 respectively; The drain electrode of S1 is electrically connected to the grid of VT1, the source electrode of S1 is electrically connected to the splicing ear A of described secondary winding, the drain electrode of S2 is electrically connected to the grid of VT2, the source electrode of S2 is electrically connected to the splicing ear B of described secondary winding, the grid of S1 is electrically connected to the splicing ear B of described secondary winding, the grid of S2 is electrically connected to the splicing ear A of described secondary winding, the drain electrode of VT1 is connected to the splicing ear B of described secondary winding, the drain electrode of VT2 is connected to the splicing ear A of described secondary winding, and the source electrode of VT1 and VT2 interconnects.
Further, above-mentioned synchronous rectificating device also can have following characteristics: described auxiliary switch S1 and S2 are MOSFET pipe or BJT pipe.
Further, above-mentioned synchronous rectificating device also can have following characteristics: described secondary winding has two, is respectively secondary main winding and auxiliary winding, and described synchronous rectification driving circuit is to be electrically connected to this auxiliary winding.
Further, above-mentioned synchronous rectificating device also can have following characteristics: described secondary winding has one, is the secondary main winding, and described synchronous rectification driving circuit is to be electrically connected to this secondary winding.
Further, above-mentioned synchronous rectificating device also can have following characteristics: the drain electrode of described VT1 and VT2 is electrically connected to two splicing ears on described secondary main winding both sides respectively, constitutes full-wave rectification or current-doubling rectifier.
Further, above-mentioned synchronous rectificating device also can have following characteristics: the positive negative sense pulse of the secondary winding voltage of described transformer is the phase place complementation, perhaps also having one section voltage between positive negative sense pulse is the zero time, the input signal of described drive circuit is described transformer secondary winding voltage, and the two-way drive signal of output is the square wave of phase place complementation.
Further, above-mentioned synchronous rectificating device also can have following characteristics: the threshold voltage of described auxiliary switch S1, S2 is equal to or less than the threshold voltage of described synchronous rectifier VT1, VT2.
As from the foregoing, synchronous rectification driving circuit with gate charge maintenance function provided by the invention, be applicable to the driving of the synchronous rectification of common source to pipe, when being applied in the supply convertor of PWM control of Transformer Winding voltage incomplementarity waveform, can avoid the prior art drive waveforms to exist the dead band to cause driving not enough problem, can be so that still can be for zero the time for MOSFET provide enough driving voltages at Transformer Winding voltage, overcome that MOSFET turn-offs during the drive waveforms dead band, the body diode conducting causes the problem that supply convertor efficient reduces.
Description of drawings
Figure 1A is the both-end DC-DC transfer circuit schematic diagram of the self-driven all-wave synchronous rectification of prior art;
Figure 1B is the both-end DC-DC transfer circuit schematic diagram of the self-driven using current double synchronous rectifier of prior art;
Fig. 1 C is the main waveform schematic diagram of circuit shown in Figure 1A and Figure 1B;
Fig. 2 A is the both-end DC-DC transfer circuit schematic diagram that prior art adopts the synchronous rectification of gate charge conversion driving;
Fig. 2 B is the main waveform schematic diagram of circuit shown in Fig. 2 A, wherein V
GS_VT1And V
GS_VT2It is the drive waveforms of synchronous rectifier VT1 and VT2;
Fig. 3 A is the schematic block circuit diagram that adopts the both-end DC-DC converter of the synchronous rectification driving circuit that the present invention proposes;
Fig. 3 B is the operation principle waveform schematic diagram of circuit shown in Fig. 3 A;
Fig. 4 A is the schematic diagram of first embodiment of the invention;
Fig. 4 B is the operation principle waveform schematic diagram of circuit shown in Fig. 4 A;
Fig. 4 C is the schematic diagram of a preferred embodiment of circuit shown in Fig. 4 A;
Fig. 5 A is the schematic diagram of second embodiment of the invention;
Fig. 5 B is the operation principle waveform schematic diagram of circuit shown in Fig. 5 A;
Fig. 5 C is the schematic diagram of a preferred embodiment of circuit shown in Fig. 5 A;
Fig. 5 D is the schematic diagram of third embodiment of the invention.
Embodiment
Referring to Fig. 3 A and Fig. 3 B.It shown in Fig. 3 A the both-end DC-DC converter that adopts synchronous rectification driving circuit of the present invention, include a DC-AC translation circuit, a power transformer (promptly the main transformer among the figure also abbreviates transformer as in the literary composition), a circuit of synchronous rectification, a synchronous rectification driving circuit and a low-pass filter circuit.Transformer wherein, circuit of synchronous rectification and synchronous rectification driving circuit have constituted a synchronous rectificating device.Described transformer comprises former limit winding, secondary winding, and wherein the secondary winding can comprise secondary main winding and auxiliary winding, also can include only the secondary main winding.
Described DC-AC translation circuit is electrically connected to the direct-current input power supplying of converter, and input direct voltage is transformed into alternating voltage is applied on the former limit winding of described transformer; Topology such as described DC-AC translation circuit can be half-bridge, full-bridge, recommend.The secondary main winding of described transformer is electrically connected to described circuit of synchronous rectification; Described transformer can comprise one or more secondary main winding; The secondary main winding of described transformer can also be to be with centre tapped winding.Described circuit of synchronous rectification comprises the first synchronous rectifier VT1 and the second synchronous rectifier VT2, and described circuit of synchronous rectification and transformer secondary main winding have been formed all-wave circuit of synchronous rectification or using current double synchronous rectifier circuit together.Described circuit of synchronous rectification is electrically connected to a low pass filter, obtains required direct voltage at the output of low pass filter.
Described synchronous rectification driving circuit comprises that two groups are respectively the drive circuit that VT1 and VT2 provide driving voltage, and every group of drive circuit is made of electric capacity charging and electric charge holding circuit and capacitor discharging circuit; Described drive circuit is electrically connected to the auxiliary winding (or secondary main winding) and the described circuit of synchronous rectification of described transformer; Described drive circuit is provided by the auxiliary winding (or secondary main winding) of described transformer and drives energy and synchronizing signal, and can when being zero, auxiliary winding (or the secondary main winding) voltage of transformer keep the electric charge that stores between described synchronous rectification tube grid and source electrode, for synchronous rectifier provides enough driving voltages, when transformer is assisted winding (or secondary main winding) voltage reversal, can in time discharge the electric charge that stores between described synchronous rectification tube grid and source electrode again, avoid the transformer secondary short circuit.
V among Fig. 3 B
WSBe the waveform of transformer secondary winding voltage in the circuit shown in Fig. 3 A, V
GS_VT1And V
GS_VT2Drive waveforms for synchronous rectifier VT1 and VT2 in the circuit shown in Fig. 3 A.Voltage waveform on the winding of the former limit of transformer is identical with the secondary winding, and amplitude difference only is as the V among Fig. 3 B
WsHaving one section voltage between the positive half wave of this alternating voltage and the negative half-wave is zero period, as the T among Fig. 3 B
R
In Fig. 3 A, described synchronous rectification driving circuit is handled the voltage waveform on the secondary winding of described transformer, makes that at Transformer Winding voltage be timing, and the grid source electric capacity charging to the first synchronous rectifier VT1 provides driving voltage; (T in referring to Fig. 3 B when the vanishing of Transformer Winding voltage
R), just the grid source electric capacity at the first synchronous rectifier VT1 of conducting still can keep normal driving voltage; When the Transformer Winding voltage reversal, the first synchronous rectifier VT1 can in time turn-off, and avoids the transformer secondary short circuit.As seen described synchronous rectification driving circuit has been exported the drive signal of two-way phase place complementation, as the V among Fig. 3 B
GS_VT1, V
GS_VT2, can avoid the conducting of secondary synchronous rectifier body diode between the afterflow period like this, reduce circuit loss, and conducting when avoiding two synchronous rectifiers.
Fig. 4 A shows a both-end DC-DC converter, has wherein adopted the synchronous rectificating device of the first embodiment of the present invention, and Fig. 4 B is the main waveform of synchronous rectification driving circuit shown in Fig. 4 A.
Transformer among Fig. 4 A comprises a former limit winding W
P, a secondary main winding W
S, an auxiliary winding W
ADescribed circuit of synchronous rectification comprises the first synchronous rectifier VT1, and the second synchronous rectifier VT2 forms all-wave circuit of synchronous rectification or using current double synchronous rectifier circuit; Described circuit of synchronous rectification is electrically connected to described transformer secondary main winding W
SDescribed synchronous rectification driving circuit comprises to described first synchronous rectifier VT1 grid source electric capacity charging and plays the first diode VD1 of electric charge maintenance effect, give the described second synchronous rectifier VT2 grid source electric capacity charging and play the second diode VD2 of electric charge maintenance effect, also comprise the first auxiliary switch S1, give the second auxiliary switch S2 of the described second synchronous rectifier VT2 grid source capacitor discharge to the described first synchronous rectifier VT1 grid source capacitor discharge.VD1 and S1 constitute first group of drive circuit, and VD2 and S2 constitute second group of drive circuit, and two groups of drive circuits are respectively VT1 and VT2 provides driving voltage, and its operation principle is identical.
Described auxiliary switch S1 and S2 are connected in parallel on respectively between the grid and source electrode of described first, second synchronous rectifier, and described auxiliary switch can be semiconductor device such as MOSFET or BJT, and its control utmost point is electrically connected to described auxiliary winding.The positive negative sense pulse of the auxiliary winding voltage of described transformer can be the phase place complementation, and also can have one section voltage between positive negative sense pulse is the zero time.The input signal of described drive circuit is the auxiliary winding voltage of described transformer, and output signal is the drive signal (as the VGS_VT1 among Fig. 4 B, VGS_VT2) of described synchronous rectifier, and described drive signal is the square wave of phase place complementation.
Introduce the operation principle of circuit among Fig. 4 A below in conjunction with the waveform among Fig. 4 B.In half work period of described DC-DC converter, as the auxiliary winding W of transformer
ALast voltage is timing, the VD1 conducting, and for VT1 provides driving voltage, auxiliary switch S2 conducting simultaneously is clamped on zero with the grid voltage of VT2; At the auxiliary winding W of transformer
ALast voltage during by positive vanishing (referring to T among Fig. 4 B
R), VD1 is anti-inclined to one side, and the grid source capacitance charge of VT1 does not have the approach of releasing, and the driving voltage of keeping the VT1 conducting is kept; When the auxiliary winding voltage of transformer was reverse, auxiliary switch S1 conducting was reduced to zero with VT1 grid source capacitance voltage, simultaneously, the VD2 conducting, S2 closes, and auxiliary winding begins the grid source electric capacity charging for VT2, next work half period of beginning.
In Fig. 4 A, exported the drive signal of two-way complementation by the synchronous rectification driving circuit that VD1, VD2, S1, S2 form, as the V among Fig. 4 B
GS_VT1, V
GS_VT2, can avoid Transformer Winding voltage like this is the conducting of synchronous rectifier body diode during zero, reduces circuit loss, and conducting when avoiding two synchronous rectifiers.
Fig. 4 C is a preferred embodiment of circuit shown in Fig. 4 A.Auxiliary switch S1 described in the circuit and S2 shown in Fig. 4 C adopt N-channel MOS FET; The auxiliary winding of described transformer has centre cap, and the first splicing ear A and the second splicing ear B are arranged.The drain electrode of the described first auxiliary switch S1 is electrically connected to the grid of the described first synchronous rectifier VT1 and the negative electrode of the described first diode VD1, the drain electrode of the described second auxiliary switch S2 is electrically connected to the grid of the described second synchronous rectifier VT2 and the negative electrode of the described second diode VD2, and the source electrode of described first, second auxiliary switch S1, S2 and described first, second synchronous rectifier VT1, VT2 is electrically connected to the centre cap of the auxiliary winding of described transformer.The grid of the anode of the described first diode VD1 and the second auxiliary switch S2 is electrically connected to the first splicing ear A of the auxiliary winding of described transformer; The grid of the anode of the described second diode VD2 and the first auxiliary switch S1 is electrically connected to the second splicing ear B of the auxiliary winding of described transformer.The drain electrode of described first, second synchronous rectifier VT1 and VT2 is electrically connected to described transformer secondary main winding W
STwo ends, constitute full-wave rectification or current-doubling rectifier.
The auxiliary winding first splicing ear A is timing with respect to centre tapped voltage when transformer, auxiliary winding W
ABy the first diode VD1 is the grid source electric capacity charging of VT1, and the first synchronous rectifier VT1 obtains driving voltage and is opening state.When the voltage on the auxiliary winding began to descend, the first diode VD1 was anti-inclined to one side, and therefore the electric charge on the first synchronous rectifier grid source electric capacity can't be released, and grid source driving voltage remains unchanged, and first synchronous rectifier keeps opening state.
When the auxiliary winding first splicing ear A of transformer begins to become negative by zero with respect to centre tapped voltage, the second splicing ear B begins just becoming and be the grid source electric capacity charging of the second synchronous rectifier VT2 by zero with respect to centre tapped voltage, and the gate source voltage of the second synchronous rectifier VT2 is V
GS_VT2=V
WA/ 2-0.7 (V), 0.7 in the formula is the conduction voltage drop of the second diode VD2; Meanwhile, the first auxiliary switch S1 obtains driving voltage V
GS_S1=V
WA/ 2 and conducting, with the grid source capacitor discharge of first synchronous rectifier to no-voltage.Select the threshold voltage (V of auxiliary switch
TH) be equal to or less than the threshold voltage of synchronous rectifier, can be so that before another synchronous rectifier to be opened, the synchronous rectifier of previous conducting can in time turn-off, and avoids the transformer secondary short circuit, decrease in efficiency.
Fig. 5 A shows a both-end DC-DC converter, has wherein adopted the synchronous rectificating device of the second embodiment of the present invention, and Fig. 5 B is the main waveform of synchronous rectification driving circuit shown in Fig. 5 A.
Transformer among Fig. 5 A comprises a former limit winding W
P, a secondary main winding W
S, an auxiliary winding W
ADescribed circuit of synchronous rectification comprises the first synchronous rectifier VT1, and the second synchronous rectifier VT2 forms all-wave circuit of synchronous rectification or using current double synchronous rectifier circuit; Described circuit of synchronous rectification is electrically connected to described transformer secondary main winding W
SDescribed synchronous rectification driving circuit comprises first, second diode VD1, the VD2 that gives described first, second synchronous rectifier VT1, the charging of VT2 grid source electric capacity respectively and play electric charge maintenance effect, also comprises first, second auxiliary switch S1, the S2 that give described first, second synchronous rectifier VT1, VT2 grid source capacitor discharge respectively.Described first, second auxiliary switch S1, S2 are connected on respectively between the grid and the auxiliary winding of described transformer of described first, second synchronous rectifier VT1, VT2, and described first, second auxiliary switch is parallel to respectively on described first, second diode VD1, the VD2; Described auxiliary switch can be semiconductor device such as MOSFET or BJT, and its control utmost point is electrically connected to described auxiliary winding.The positive negative sense pulse of the auxiliary winding voltage of described transformer can be the phase place complementation, and also can have one section voltage between positive negative sense pulse is the zero time.The input signal of described drive circuit is the auxiliary winding voltage of described transformer, and output signal is the drive signal of described synchronous rectifier, and described drive signal is the square wave of phase place complementation.
Introduce the operation principle of circuit among Fig. 5 A below in conjunction with the waveform among Fig. 5 B.In half work period of described DC-DC converter, as the auxiliary winding W of transformer
ALast voltage is for just, and when making the VD1 conducting, VT1 and S2 obtain driving voltage and conducting, and S2 is produced the grid clamping of VT2 in auxiliary winding negative voltage is so VT2 ends.As auxiliary winding W
ALast voltage during by positive vanishing (referring to T among Fig. 4 B
R), VD1 is anti-inclined to one side, and the grid source capacitance charge of VT1 does not have the approach of releasing, and the driving voltage of keeping the VT1 conducting is kept; When transformer secondary winding voltage was reverse, auxiliary switch S1 conducting was reduced to zero with VT1 grid source capacitance voltage, and auxiliary simultaneously winding begins the grid source electric capacity charging for VT2, next work half period of beginning.
In Fig. 5 A, exported the drive signal of two-way complementation by the synchronous rectification driving circuit that VD1, VD2, S1, S2 form, as the V among Fig. 4 B
GS_VT1, V
GS_VT2, can avoid Transformer Winding voltage like this is the conducting of synchronous rectifier body diode during zero, reduces circuit loss, and conducting when avoiding two synchronous rectifiers.
Fig. 5 C is a preferred embodiment of circuit among Fig. 5 A.Auxiliary switch S1 and S2 described in Fig. 5 C circuit adopt N-channel MOS FET, and described first, second diode utilizes the body diode of described first, second auxiliary switch to serve as respectively; Described transformer is assisted winding W
AHave centre cap, and the first splicing ear A and the second splicing ear B are arranged.The drain electrode of described first, second auxiliary switch S1, S2 is electrically connected to the grid of described first, second synchronous rectifier VT1, VT2 respectively; Described first, second diode utilizes the body diode of described first, second auxiliary switch to serve as respectively; The source electrode of described first, second auxiliary switch S1, S2 is electrically connected to the auxiliary winding W of described transformer respectively
AFirst, second splicing ear A, B.The source electrode of the grid of described first, second auxiliary switch S1, S2 and described first, second synchronous rectifier VT1, VT2 is electrically connected to the centre cap of the auxiliary winding of described transformer.The drain electrode of described first, second synchronous rectifier VT1 and VT2 is electrically connected to described transformer secondary main winding W
STwo ends, constitute full-wave rectification or current-doubling rectifier.
As auxiliary winding W
SThe first splicing ear A is timing with respect to centre tapped voltage, and auxiliary winding is the grid source electric capacity charging of VT1 by the body diode of S1, and VT1 obtains driving voltage and open-minded; S2 conducting simultaneously, auxiliary winding provides negative voltage for the grid source electrode of VT2, so VT2 turn-offs.When the voltage on the auxiliary winding began to descend, the body diode of S1 was anti-inclined to one side, thus the electric charge on the electric capacity of VT1 grid source can't release, grid source driving voltage remains unchanged, VT1 keeps opening state; Meanwhile, the negative drive voltage amplitude between VT2 grid source electrode begins to reduce, until S2 because of driving voltage less than its threshold voltage (V
TH) and till turn-offing, the negative drive voltage amplitude between VT2 grid source electrode is-V at this moment
TH
As auxiliary winding W
SWhen the first splicing ear A began to become negative by zero with respect to centre tapped voltage, the second splicing ear B began just becoming and for the grid source electric capacity of VT2 charges, the gate source voltage of VT2 is V by zero with respect to centre tapped voltage
GS_VT2=V
WA/ 2-0.7 (V), 0.7 in the formula is the conduction voltage drop of the body diode of S2; Meanwhile, S1 obtains driving voltage V
GS_S1=V
WAAnd conducting, described auxiliary winding W
AProvide negative voltage by S1 for the grid source electrode of VT1, so VT1 turn-offs.Select the threshold voltage (V of auxiliary switch S1, S2
TH) be equal to or less than the threshold voltage of synchronous rectifier VT1, VT2, can be so that before another synchronous rectifier be opened, the synchronous rectifier of previous conducting can in time turn-off, and avoids the conducting simultaneously of two synchronous rectifiers to cause transformer secondary short circuit, decrease in efficiency.
Here because first, second synchronous rectifier has negative driving voltage when turn-offing, accelerate turn-off speed, can further avoid the conducting simultaneously of two synchronous rectifiers.In the voltage of the Transformer Winding first splicing ear A begins by negative sense zero transforming process, the driving voltage of the first auxiliary switch S1 drop to its below threshold voltage before this pipe still keep conducting, therefore the negative voltage of the grid source electric capacity of the first synchronous rectifier VT1 can be followed the auxiliary winding W of transformer
AThe drops that powers on is up to dropping to-V
THShi Buzai descends.
Fig. 5 D shows a both-end DC-DC converter, has wherein adopted the synchronous rectificating device of the third embodiment of the present invention.Synchronous rectificating device among this device and Fig. 5 C is basic identical, just in the present embodiment, and the secondary main winding W of transformer
SSimultaneously as auxiliary winding W
A, and do not have centre cap.
As shown in the figure, described transformer secondary main winding W
SThe first splicing ear A be electrically connected to the drain electrode of the second synchronous rectifier VT2, the source electrode of the first auxiliary switch S1, the grid of the second auxiliary switch S2, described transformer secondary main winding W
SThe second splicing ear B be electrically connected to the drain electrode of the first synchronous rectifier VT1, the source electrode of the second auxiliary switch S2, the grid of the first auxiliary switch S1.The grid of the described first synchronous rectifier VT1 is electrically connected to the drain electrode of the first auxiliary switch S1, and the grid of the described second synchronous rectifier VT2 is electrically connected to the drain electrode of the second auxiliary switch S2.The operation principle of circuit is similar with Fig. 5 C circuit among Fig. 5 D.
Described several preferred embodiment of the present invention above particularly, but should be appreciated that general personnel, can under the situation that does not break away from spirit of the present invention, make various variations for the present technique field.The foregoing description is to be used to the present invention is described and to be not to limit the invention.
Claims (14)
1, a kind of synchronous rectificating device, comprise transformer, circuit of synchronous rectification and synchronous rectification driving circuit, described transformer comprises former limit winding and one or more secondary winding, described circuit of synchronous rectification and transformer secondary winding have been formed all-wave or using current double synchronous rectifier circuit together, comprise the first synchronous rectifier VT1 and the second synchronous rectifier VT2, described synchronous rectification driving circuit is electrically connected to the grid of two synchronous rectifiers in a secondary winding and the described circuit of synchronous rectification, one side of this secondary winding has splicing ear A, another side has splicing ear B, it is characterized in that
Described synchronous rectification driving circuit comprises and is respectively two groups of drive circuits that VT1 and VT2 provide driving voltage, every group of drive circuit comprises an electric capacity charging and electric charge holding circuit and a capacitor discharging circuit, the charging of described electric capacity and electric charge holding circuit are the grid source electric capacity charging of respective synchronization rectifying tube in transformer secondary winding voltage during for forward, provide synchronous rectifier required driving voltage, and when the secondary winding voltage is zero, maintain the electric charge that stores between described grid, source electrode; When the Transformer Winding voltage reversal, described capacitor discharging circuit discharges the electric charge that stores between described synchronous rectifier grid, source electrode, avoids VT1 and VT2 conducting simultaneously, and, the two-way drive signal phase place complementation of two groups of drive circuit outputs.
2, synchronous rectificating device as claimed in claim 1, it is characterized in that, first group of drive circuit in the described synchronous rectification driving circuit is included as the electric capacity charging of VT1 grid source and plays the first diode VD1 of electric charge maintenance effect, and be the first auxiliary switch S1 of VT1 grid source capacitor discharge, sun level and the negative electrode of VD1 are electrically connected to the splicing ear A of described secondary winding and the grid of VT1 respectively, S1 is connected in parallel on the grid, source electrode of VT1, and the control utmost point of S1 is electrically connected to described secondary winding; Second group of drive circuit is included as the second diode VD2 that VT2 grid source electric capacity charges and plays electric charge maintenance effect, and be the second auxiliary switch S2 of VT2 grid source capacitor discharge, the anode of VD2 and negative electrode are electrically connected to the splicing ear B of described secondary winding and the grid of VT2 respectively, S2 is connected in parallel on the grid, source electrode of VT2, and the control utmost point of S2 is electrically connected to described secondary winding.
3, synchronous rectificating device as claimed in claim 2, it is characterized in that, described secondary winding also comprises a centre cap, the source electrode of VT1 and VT2 all is electrically connected on this centre cap, the control utmost point of S1 is electrically connected to the splicing ear B of secondary winding, and the control utmost point of S2 is electrically connected to the splicing ear A of secondary winding.
4, synchronous rectificating device as claimed in claim 3, it is characterized in that, described auxiliary switch S1 and S2 are N-channel MOS FET, the drain electrode of S1 is electrically connected to the grid of VT1, the grid of S1 is electrically connected to the splicing ear B of described secondary winding, the drain electrode of S2 is electrically connected to the grid of VT2, and the grid of S2 is electrically connected to the splicing ear A of described secondary winding, and the source electrode of S1 and S2 all is electrically connected to described centre cap.
5, synchronous rectificating device as claimed in claim 1, it is characterized in that, first group of drive circuit in the described synchronous rectification driving circuit is included as the electric capacity charging of VT1 grid source and plays the first diode VD1 of electric charge maintenance effect, and be the first auxiliary switch S1 of VT1 grid source capacitor discharge, the anode of VD1 and negative electrode are electrically connected to the splicing ear A and the VT1 grid of described secondary winding respectively, S1 is in parallel with VD1, and the S1 control utmost point is electrically connected to described secondary winding; Second group of drive circuit is included as the second diode VD2 that VT2 grid source electric capacity charges and plays electric charge maintenance effect, and be the second auxiliary switch S2 of VT2 grid source capacitor discharge, the anode of VD2 and cathodic electricity are connected to the splicing ear B and the VT2 grid of described secondary winding, S2 is in parallel with VD2, and the S2 control utmost point is electrically connected to described secondary winding.
6, synchronous rectificating device as claimed in claim 5 is characterized in that, described secondary winding also comprises a centre cap, and the control utmost point of the source electrode of described VT1 and VT2, S1 and S2 all is electrically connected on this centre cap.
7, synchronous rectificating device as claimed in claim 6 is characterized in that, described auxiliary switch S1 and S2 are N-channel MOS FET, and described VD1 and VD2 serve as with the body diode of described S1 and S2 respectively; The drain electrode of S1 is electrically connected to the grid of VT1, the source electrode of S1 is electrically connected to the splicing ear A of described secondary winding, the drain electrode of S2 is electrically connected to the grid of VT2, and the source electrode of S2 is electrically connected to the splicing ear B of described secondary winding, and the grid of S1 and S2 all is electrically connected to described centre cap.
8, synchronous rectificating device as claimed in claim 6 is characterized in that, described auxiliary switch S1 and S2 are N-channel MOS FET, and described VD1 and VD2 serve as with the body diode of described S1 and S2 respectively; The drain electrode of S1 is electrically connected to the grid of VT1, the source electrode of S1 is electrically connected to the splicing ear A of described secondary winding, the drain electrode of S2 is electrically connected to the grid of VT2, the source electrode of S2 is electrically connected to the splicing ear B of described secondary winding, the grid of S1 is electrically connected to the splicing ear B of described secondary winding, the grid of S2 is electrically connected to the splicing ear A of described secondary winding, the drain electrode of VT1 is connected to the splicing ear B of described secondary winding, the drain electrode of VT2 is connected to the splicing ear A of described secondary winding, and the source electrode of VT1 and VT2 interconnects.
As claim 2 or 5 described synchronous rectificating devices, it is characterized in that 9, described auxiliary switch S1 and S2 are MOSFET pipe or BJT pipe.
As the described synchronous rectificating device of arbitrary claim in the claim 1 to 7, it is characterized in that 10, described secondary winding has two, be respectively secondary main winding and auxiliary winding, described synchronous rectification driving circuit is to be electrically connected to this auxiliary winding.
As the described synchronous rectificating device of arbitrary claim in the claim 1 to 7, it is characterized in that 11, described secondary winding has one, be the secondary main winding, described synchronous rectification driving circuit is to be electrically connected to this secondary winding.
12, synchronous rectificating device as claimed in claim 10 is characterized in that, the drain electrode of described VT1 and VT2 is electrically connected to two splicing ears on described secondary main winding both sides respectively, constitutes full-wave rectification or current-doubling rectifier.
13, synchronous rectificating device as claimed in claim 1, it is characterized in that, the positive negative sense pulse of the secondary winding voltage of described transformer is the phase place complementation, perhaps also having one section voltage between positive negative sense pulse is the zero time, the input signal of described drive circuit is described transformer secondary winding voltage, and the two-way drive signal of output is the square wave of phase place complementation.
As the described synchronous rectificating device of arbitrary claim in the claim 1 to 7, it is characterized in that 14, the threshold voltage of described auxiliary switch S1, S2 is equal to or less than the threshold voltage of described synchronous rectifier VT1, VT2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510132573 CN1992488A (en) | 2005-12-26 | 2005-12-26 | Synchronous rectification device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510132573 CN1992488A (en) | 2005-12-26 | 2005-12-26 | Synchronous rectification device |
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| CN1992488A true CN1992488A (en) | 2007-07-04 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112019074A (en) * | 2019-05-31 | 2020-12-01 | 台达电子工业股份有限公司 | Rectification control module, active bridge rectification control device and operation method thereof |
| CN112532080A (en) * | 2020-12-01 | 2021-03-19 | 复旦大学 | High-efficiency control method and device for silicon carbide power electronic converter and converter |
-
2005
- 2005-12-26 CN CN 200510132573 patent/CN1992488A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112019074A (en) * | 2019-05-31 | 2020-12-01 | 台达电子工业股份有限公司 | Rectification control module, active bridge rectification control device and operation method thereof |
| CN112019074B (en) * | 2019-05-31 | 2023-06-20 | 台达电子工业股份有限公司 | Rectification control module, active bridge rectification control device and operation method thereof |
| CN112532080A (en) * | 2020-12-01 | 2021-03-19 | 复旦大学 | High-efficiency control method and device for silicon carbide power electronic converter and converter |
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