Driving circuit of multi-tube flyback circuit, multi-tube flyback circuit and switching power supply

Abstract

The utility model discloses a drive circuit of a multi-tube flyback circuit, the multi-tube flyback circuit and a switching power supply. The driving circuit of the multi-tube flyback circuit comprises a transformer, an input circuit and a plurality of output circuits. The transformer comprises a primary side coil and a plurality of secondary side coils; the input circuit comprises a first switch tube, a second switch tube, a first capacitor and a clamping diode; the first switch tube and the second switch tube are connected in series between the anode and the cathode of the auxiliary power supply; the base of the first switch tube is connected with the base of the second switch tube; the first capacitor and the clamping diode are connected in parallel, a first parallel connection point corresponding to a cathode of the clamping diode is connected with a connection point of the first switch tube and the second switch tube, and a second parallel connection point corresponding to an anode of the clamping diode is connected with a dotted terminal of the primary coil; the synonym end of the primary coil is connected with the cathode of the auxiliary power supply; and each secondary side coil is connected with one MOS tube through the corresponding output circuit. According to the utility model, the over-drive phenomenon of the MOS tube can be inhibited.

Description

TECHNICAL FIELD

[0001] The utility model belongs to power supply technical field especially relates to a drive circuit of multi -tube flyback circuit, multi -tube flyback circuit and switching power supply. BACKGROUND

[0002] With the development of the auxiliary power supply of high-voltage power supply, multi -tube flyback circuit is widely applied. Multi -tube flyback circuit includes multiple metal oxide semiconductor field effect transistors (MOS tube), when applying multi -tube flyback circuit, multiple MOS tubes need to be driven to control multi -tube flyback circuit work.

[0003] The related art is mainly through the drive transformer to drive the MOS tube in multi -tube flyback circuit, but due to the excitation of drive transformer and the conservation of volt-second product, when the duty cycle of pulse width modulation (PWM) signal suddenly decreases, MOS tube drive will appear overdrive phenomenon, that is, the drive waveform will appear PWM wave of drive low level too high, which will make MOS tube straight through, and further will lead to the phenomenon of tube explosion in the running process. UTILITY MODEL CONTENT

[0004] The utility model embodiment provides a drive circuit of multi -tube flyback circuit, multi -tube flyback circuit and switching power supply to inhibit the overdrive phenomenon of MOS tube.

[0005] The first aspect of the utility model embodiment provides a drive circuit of multi -tube flyback circuit, including transformer, input circuit and multiple output circuits;The transformer includes a primary winding and multiple secondary windings;Wherein, the multiple secondary windings, the multiple output circuits and the number of MOS tubes in multi -tube flyback circuit are same;

[0006] The input circuit includes first switch tube, second switch tube, first capacitor and clamping diode;

[0007] The first switch tube and the second switch tube are connected in series between the positive and negative of auxiliary power supply;The base of the first switch tube and the base of the second switch tube are connected, and are used for input control signal;

[0008] The first capacitor and the clamping diode are connected in parallel, and the cathode of the clamping diode corresponds to the first junction point of the first switch tube and the second switch tube in series connection point, and the anode of the clamping diode corresponds to the second junction point of the primary winding of the same name end;

[0009] The different name end of the primary winding is used for connecting the negative of the auxiliary power supply;

[0010] Each of the secondary side coils is connected with a MOS transistor through its corresponding output circuit, for inputting the corresponding driving signal of the control signal to the gate of the MOS transistor.

[0011] In one embodiment, each of the output circuits comprises an absorption unit; the absorption unit is connected between the same name end and the different name end of its corresponding secondary side coil.

[0012] In one embodiment, the absorption unit comprises an absorption diode and an absorption resistor;

[0013] The anode of the absorption diode is connected with the first end of the absorption resistor;

[0014] The cathode of the absorption diode is connected with the same name end of its corresponding secondary side coil;

[0015] The second end of the absorption resistor is connected with the different name end of its corresponding secondary side coil.

[0016] In one embodiment, each of the output circuits further comprises a first resistor and a second resistor;

[0017] The first end of the first resistor is connected with the same name end of its corresponding secondary side coil; the second end of the second resistor is connected with the different name end of its corresponding secondary side coil;

[0018] The second end of the first resistor and the first end of the second resistor are connected and serve as the output end of the output circuit.

[0019] In one embodiment, the first switch transistor is an NPN type triode, and the second switch transistor is a PNP type triode;

[0020] The collector of the first switch transistor is used for connecting the positive pole of the auxiliary power supply;

[0021] The emitter of the first switch transistor and the emitter of the second switch transistor are connected;

[0022] The collector of the second switch transistor is used for connecting the negative pole of the auxiliary power supply.

[0023] In one embodiment, the capacitance of the first capacitor ranges from 100nF to 1000nF.

[0024] In one embodiment, the capacitance of the first capacitor is 200nF.

[0025] In one embodiment, the input circuit further comprises a second capacitor;

[0026] The second capacitor is connected between the positive pole and the negative pole of the auxiliary power supply.

[0027] The second aspect of the embodiment of the utility model provides a kind of multi-tube flyback circuit, including multiple MOS tubes and the driving circuit of the multi-tube flyback circuit as described in any one of the first aspect or the first aspect.

[0028] The second aspect of the embodiment of the utility model provides a kind of switching power supply, including the multi-tube flyback circuit as described in the second aspect.

[0029] The beneficial effects existing in the embodiment of the utility model compared with prior art are as follows:

[0030] By setting the clamping diode in the input circuit of the primary coil, and making the clamping diode and the first capacitor in the input circuit parallel, and making the anode of the clamping diode and the like end of the primary coil connected, the overdrive phenomenon of the transformer can be inhibited, the risk of the MOS tube driven by the driven circuit is reduced, and the possibility of tube explosion phenomenon in the running process is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical scheme in the embodiment of the utility model, the drawings needed to be used in the embodiment or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can be obtained without creative labor under the premise of these drawings.

[0032] Figure 1 It is the first module structure schematic diagram of the driving circuit of the multi-tube flyback circuit provided by the embodiment of the utility model;

[0033] Figure 2 It is the second module structure schematic diagram of the driving circuit of the multi-tube flyback circuit provided by the embodiment of the utility model;

[0034] Figure 3 It is the first circuit structure diagram of the driving circuit of the multi-tube flyback circuit provided by the embodiment of the utility model;

[0035] Figure 4 It is the second circuit structure diagram of the driving circuit of the multi-tube flyback circuit provided by the embodiment of the utility model;

[0036] Figure 5 It is the third circuit structure diagram of the driving circuit of the multi-tube flyback circuit provided by the embodiment of the utility model;

[0037] Figure 6 It is the fourth circuit structure diagram of the driving circuit of the multi-tube flyback circuit provided by the embodiment of the utility model;

[0038] Figure 7The utility model embodiment provides the circuit structure diagram of the drive circuit of the multi -tubular flyback circuit which has not carried out the drive optimization.

[0039] Figure 8 The utility model embodiment provides the GS overdrive waveform chart of the MOS tube which has not carried out the drive optimization MOS tube.

[0040] Figure 9 The utility model embodiment provides the GS overdrive waveform chart of the MOS tube of setting clamping diode.

[0041] Figure 10 The utility model embodiment provides the GS overdrive waveform chart of the MOS tube of setting absorption unit.

[0042] Figure 11 The utility model embodiment provides the waveform chart after optimization drive waveform top drop.

[0043] Figure 12 The utility model embodiment provides a partial circuit structure diagram of multi -tubular flyback circuit. DETAILED DESCRIPTION

[0044] In order to make the personnel in the technical field better understand the scheme, the technical scheme in the scheme embodiment will be clearly described below in conjunction with the drawings in the scheme embodiment, obviously, the described embodiment is a part of the embodiment of the scheme, rather than all the embodiments. Based on the embodiment in the scheme, all other embodiments obtained by the ordinary skill in the art without creative labor should belong to the protection scope of the scheme.

[0045] The term " includes " and other any variation in the specification and claims of the scheme and the above-mentioned drawing is " includes but is not limited to ", the intention is to cover the non-exclusive inclusion, and is not limited to the examples listed in the text. In addition, the terms " first " and " second " are used to distinguish different objects, rather than to describe a specific order.

[0046] The inventor finds that in the process of driving the MOS tube of multi -tubular flyback circuit, when the duty ratio of PWM drive signal suddenly reduces, the MOS tube drive will appear overdrive phenomenon, makes MOS tube straight through, can cause the phenomenon of tube explosion in the operation process of switching power supply.

[0047] From the idea of inhibiting the overdrive phenomenon of MOS tube in multi -tubular flyback circuit, in the embodiment of the application, the clamping diode is arranged in the input circuit corresponding to the primary winding of transformer, the clamping diode is parallelly connected with the first capacitor, thereby inhibiting the overdrive phenomenon of transformer.

[0048] The implementation of the utility model will be described in detail in combination with specific drawings as follows:

[0049] Referring to Figure 1 The utility model provides a drive circuit of multi-tube flyback circuit, including transformer 1, input circuit 2 and multiple output circuits 3, transformer 1 includes one primary winding T1A and multiple secondary windings T1X, wherein multiple secondary windings T1X, multiple output circuits 3 and the number of MOS tube in multi-tube flyback circuit are same.

[0050] Input circuit 1 includes first switch tube Q1a, second switch tube Q1b, first capacitor C1 and clamping diode D1.

[0051] First switch tube Q1a and second switch tube Q1b are connected in series between the positive pole VAUX of auxiliary power supply and negative pole DC-, and the base of first switch tube Q1a and the base of second switch tube Q1b are connected for inputting control signal, first capacitor C1 and clamping diode D1 are connected in parallel, and the cathode of clamping diode D1 is connected to the first junction point of first switch tube Q1a and second switch tube Q1b, and the anode of clamping diode D1 is connected to the same name end of primary winding T1A.

[0052] The different name end of primary winding T1A is used for connecting the negative pole DC- of auxiliary power supply.

[0053] Here, the control signal can be positive level signal or negative level signal, and the control signal can be converted into driving signal for driving transistor in multi-tube flyback circuit after passing through drive circuit.

[0054] When the control signal is positive level signal, first switch tube Q1a is turned on and outputs to the primary winding T1A of transformer 1 to form voltage, and when the control signal is negative level signal, second switch tube Q1b is turned on and outputs to the primary winding T1A of transformer 1 to form voltage.

[0055] In the embodiment, first capacitor C1 and clamping diode D1 are connected in parallel and connected to the same name end of primary winding T1A, when the duty cycle of switch tube suddenly changes, the voltage spike of primary winding T1A can be caused, at this time, the clamping diode is turned on, and the part of voltage spike can be clamped in a safe range, thereby reducing the occurrence of overdrive phenomenon and avoiding the explosion of MOS tube.

[0056] In addition, the leakage energy of primary winding T1A can be absorbed by clamping diode D1 and first capacitor C1 to prevent the damage of switch tube caused by the spike voltage.

[0057] Optionally, as Figure 1As shown, the first switching transistor Q1a can be an NPN transistor, and the second switching transistor Q1b can be a PNP transistor. The collector of the first switching transistor Q1a is connected to the positive terminal VAUX of the auxiliary power supply. The emitter of the first switching transistor Q1a is connected to the emitter of the second switching transistor Q1b. The collector of the second switching transistor Q1b is connected to the negative terminal DC- of the auxiliary power supply.

[0058] For the secondary side of the transformer, each secondary coil T1X is connected to a MOSFET through its corresponding output circuit 3, which is used to input the drive signal corresponding to the control signal to the gate of the MOSFET.

[0059] Here, each secondary coil T1X corresponds to a MOSFET, and the MOSFET is controlled by inputting a drive signal to the gate of the MOSFET.

[0060] The same-name terminal of each secondary coil T1X can be connected to the gate of the MOSFET through the output circuit 3, and the opposite-name terminal of the secondary coil T1X can be connected to the source of the MOSFET through the output circuit 3.

[0061] This embodiment of the invention, by setting a clamping diode in the input circuit of the primary coil, connecting the clamping diode in parallel with the capacitor in the input circuit, and connecting the anode of the clamping diode to the same-name terminal of the primary coil, can suppress the overdrive phenomenon of the transformer, reduce the risk of the MOS transistor driven by the driven circuit shoot-through, and reduce the possibility of transistor explosion during operation.

[0062] In some embodiments, the capacitance value of the first capacitor C1 can be in the range of 100nF to 1000nF. For example, the capacitance value of the first capacitor C1 can be 100nF, 200nF, and 1000nF, etc.

[0063] Here, by setting the capacitance value of the first capacitor C1 in the input circuit, the peak drop phenomenon in the drive signal of the MOSFET can be optimized, avoiding an unexpected negative voltage at the gate voltage of the MOSFET, which would affect the normal operation of the MOSFET.

[0064] Preferably, the capacitance of the first capacitor can be 200nF.

[0065] In some embodiments, such as Figure 2 As shown, the input circuit 1 also includes a second capacitor C2; the second capacitor C2 is connected between the positive terminal VAUX and the negative terminal DC- of the auxiliary power supply.

[0066] Here, by setting the second capacitor C1, the voltage stress of the first switching transistor Q1a and the second switching transistor Q1b can be reduced when the two transistors are disconnected, and the output of the auxiliary power supply can be stabilized.

[0067] In some embodiments, such as Figure 3As shown in the figure, each output circuit 3 includes an absorption unit 31; the absorption unit 31 is connected between the same name end and the different name end of its corresponding secondary coil T1X.

[0068] In this embodiment, in order to further inhibit the overdrive phenomenon of the transformer, an absorption unit can be arranged in each output circuit 3, and the absorption unit is used to inhibit the voltage peak in the corresponding output circuit 3, and leave voltage margin for the MOS.

[0069] Optionally, referring to Figure 3 , the absorption unit 31 includes an absorption diode D2x and an absorption resistor R3x; the anode of the absorption diode D2x is connected with the first end of the absorption resistor R3x; the cathode of the absorption diode D2x is connected with the same name end of its corresponding secondary coil T1X; the second end of the absorption resistor R3x is connected with the different name end of its corresponding secondary coil T1X.

[0070] Here, x in the absorption diode D2x and the absorption resistor R3x can be b, c, d, …, and the above x corresponds to X in the secondary coil T1X.

[0071] In one embodiment, as Figure 4 shown in the second circuit structure diagram of the driving circuit of the multi-tube flyback circuit, and Figure 5 shown in the third circuit structure diagram of the driving circuit of the multi-tube flyback circuit, each output circuit 3 further includes a first resistor R1x and a second resistor R2x; the first end of the first resistor R1x is connected with the same name end of its corresponding secondary coil T1X; the second end of the second resistor R2x is connected with the different name end of its corresponding secondary coil T1X; the second end of the first resistor R1x and the first end of the second resistor R2x are connected as the output end of the output circuit 3.

[0072] In this embodiment, as Figure 4 and Figure 5 shown, the second end of the first resistor R1x and the first end of the second resistor R2x are connected, and are connected with the gate of the MOS tube corresponding to the output circuit 3; the different name end of the secondary coil T1X is connected with the source of the corresponding MOS tube Qi.

[0073] Here, each secondary coil T1X corresponds to a MOS tube Qi in the multi-tube flyback circuit, and i can be 2, 3, 4, …, n, wherein i corresponds to X in the secondary coil T1X.

[0074] In other embodiments, as Figure 6 shown, in the driving circuit of the multi-tube flyback circuit, the absorption circuit 31 can also be arranged in each output circuit 3, and the clamping diode D1 is not arranged in the input circuit 1. The effect of inhibiting overdrive can also be achieved by the separate absorption circuit 31.

[0075] The input circuit 1 includes a first transistor Q1a, a second transistor Q1b, and a first capacitor C1, while each output circuit 3 includes an absorption unit 31. Additionally, the input circuit 1 may also include a second capacitor C2, and each output circuit 3 may also include a first resistor and a second resistor, etc.

[0076] In some specific embodiments, with Figure 7 The drive circuit of the multi-transistor flyback circuit shown was tested, and the GS overdrive waveform without optimization for overdrive phenomenon was obtained, i.e. Figure 8 .by Figure 1 The test shown was conducted on the drive circuit of the multi-transistor flyback circuit to determine how to optimize overdrive by adding a clamping diode in the input circuit. Figure 9 .contrast Figure 8 and Figure 9 It can be seen that by setting clamping diode D1 in input circuit 1, overdrive of the MOSFET drive waveform can be suppressed. Among them, the GS overdrive waveform refers to the voltage in the voltage waveform between the gate (G) and source (S) of the MOSFET that exceeds the normal drive voltage.

[0077] by Figure 6 The drive circuit of the multi-transistor flyback circuit shown was tested to determine the overdrive situation by adding an absorption unit to the output circuit. Figure 10 .contrast Figure 8 and Figure 10 It can be seen that by setting the absorption unit 31 in the output circuit 3, the overdrive of the MOS transistor drive waveform can be suppressed.

[0078] By comparison Figure 9 and Figure 10 It can be seen that the scheme using clamping diode D1 is superior to the scheme using absorption unit 31 in suppressing the overdrive of the MOSFET drive waveform. Furthermore, the clamping diode D1 only requires one component, resulting in lower overall losses, while the absorption circuit 31 requires a resistor and a diode in each output circuit 3, requiring more components and resulting in greater overall losses.

[0079] In other specific embodiments, the top drop phenomenon is optimized by changing the capacitance value of the first capacitor C1 connected in series with the primary winding T1A of the transformer. Tests were conducted for capacitance values ​​of 100nF, 200nF, and 1000nF, respectively.

[0080] See Figure 11The waveform diagram after the top drop of the optimized drive waveform shows that the top drop phenomenon can be optimized by adjusting the capacitance of the first capacitor C1. When the capacitance of the first capacitor C1 is 100 nF, the amplitude of the top drop of the drive waveform is 2.40 V, which is reduced from 9.20 V to 6.80 V; when the capacitance of the first capacitor C1 is 200 nF, the amplitude of the top drop of the drive waveform is 2.40 V, which is reduced from 9.40 V to 7.00 V; when the capacitance of the first capacitor C1 is 1000 nF, the amplitude of the top drop of the drive waveform is 2.70 V, which is reduced from 9.70 V to 7.00 V. Obviously, the capacitance of the first capacitor C1 is 200 nF, which is the best optimization effect on the top drop of the drive waveform, which is better than the other two capacitances.

[0081] The application also provides a multi-tube flyback circuit and a switching power supply. For details not described in detail, please refer to the corresponding circuit embodiments described above.

[0082] In some embodiments, the multi-tube flyback circuit can include a plurality of MOS tubes and a drive circuit of the multi-tube flyback circuit as in any of the above embodiments.

[0083] Optionally, as Figure 12 shown, the multi-tube flyback circuit can include two MOS tubes, a second MOS tube Q2 and a third MOS tube Q3, and correspondingly, the drive circuit of the multi-tube flyback circuit also includes two secondary side coils and two output circuits corresponding to them, i.e. a first secondary side coil T1B and a second secondary side coil T1C, each of which corresponds to an output circuit 3.

[0084] Among them, the multi-tube flyback circuit can also include a second transformer 2, which includes two coils, namely a first coil T2A and a second coil T2B. The source of the second MOS tube Q2 is connected to the non-identical end of the first coil T2A, the identical end of the first coil T2A is connected to the non-identical end of the second coil T2B, and the identical end of the second coil T2B is connected to the source of the third MOS tube.

[0085] In addition, the source of the second MOS tube Q2 is also connected to the negative pole of the auxiliary power supply through two diodes (i.e. Figure 12 D2 and D3 in Figure 12 , and the source of the third MOS tube is also connected to the positive pole of the auxiliary power supply through two diodes (i.e.

[0086] In some embodiments, the switching power supply can include the multi-tube flyback circuit as above.

[0087] The above-described above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features therein can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A driving circuit of a multi-tube flyback circuit, characterized by, The application relates to a multi-tube flyback circuit, which comprises a transformer, an input circuit and a plurality of output circuits; the transformer comprises a primary coil and a plurality of secondary coils; wherein the number of the plurality of secondary coils, the plurality of output circuits and the number of MOS tubes in the multi-tube flyback circuit are the same. The input circuit comprises a first switch tube, a second switch tube, a first capacitor and a clamping diode. The first switch tube and the second switch tube are connected in series between the positive electrode and the negative electrode of an auxiliary power supply; the base of the first switch tube is connected with the base of the second switch tube, and is used for inputting a control signal. The first capacitor and the clamping diode are connected in parallel; the cathode of the clamping diode is connected with a first connecting point corresponding to the connection point of the first switch tube and the second switch tube in series, and the anode of the clamping diode is connected with the same end of the primary coil. The different end of the primary coil is used for connecting the negative electrode of the auxiliary power supply. Each secondary coil is connected with one MOS tube through the corresponding output circuit, and is used for inputting a driving signal corresponding to the control signal to the gate of the MOS tube.

2. The driving circuit of a multi-tube flyback circuit according to claim 1, characterized by, Each output circuit comprises an absorption unit, which is connected between the same end and the different end of the corresponding secondary coil.

3. The driving circuit of a multi-tube flyback circuit according to claim 2, characterized in that, The absorption unit comprises an absorption diode and an absorption resistor. The anode of the absorption diode is connected with the first end of the absorption resistor. The cathode of the absorption diode is connected with the same end of the corresponding secondary coil. The second end of the absorption resistor is connected with the different end of the corresponding secondary coil.

4. The driving circuit of a multi-tube flyback circuit according to claim 3, characterized by Each output circuit further comprises a first resistor and a second resistor. The first end of the first resistor is connected with the same end of the corresponding secondary coil, and the second end of the second resistor is connected with the different end of the corresponding secondary coil. The second end of the first resistor and the first end of the second resistor are connected, and the connection point is used as the output end of the output circuit.

5. The driving circuit of a multi-tube flyback circuit according to any one of claims 1 to 4, characterized in that, The first switch tube is an NPN triode, and the second switch tube is a PNP triode. The collector of the first switch tube is used for connecting the positive electrode of the auxiliary power supply. The emitter of the first switch tube is connected with the emitter of the second switch tube. The collector of the second switch tube is used for connecting the negative electrode of the auxiliary power supply.

6. The driving circuit of a multi-tube flyback circuit according to claim 1 or 2, characterized by The capacitance of the first capacitor ranges from 100nF to 1000nF.

7. The driving circuit of a multi-tube flyback circuit according to claim 6, characterized by The capacitance of the first capacitor is 200nF.

8. The driving circuit of a multi-tube flyback circuit according to claim 2, characterized by, The input circuit further comprises a second capacitor. The second capacitor is connected between the positive electrode and the negative electrode of the auxiliary power supply.

9. A multiple-tub reverse flyback circuit, characterized by, The application further relates to a driving circuit comprising a plurality of MOS tubes and the multi-tube flyback circuit according to any one of claims 1 to 8.

10. A switching power supply, characterized by comprising: The application further relates to a multi-tube flyback circuit according to claim 9.

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