CN105356728A - Isolated drive circuit - Google Patents
Isolated drive circuit Download PDFInfo
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- CN105356728A CN105356728A CN201510873552.8A CN201510873552A CN105356728A CN 105356728 A CN105356728 A CN 105356728A CN 201510873552 A CN201510873552 A CN 201510873552A CN 105356728 A CN105356728 A CN 105356728A
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- 238000004804 winding Methods 0.000 claims abstract description 72
- 239000003990 capacitor Substances 0.000 claims abstract description 47
- 238000002955 isolation Methods 0.000 claims abstract description 47
- 230000005284 excitation Effects 0.000 claims description 28
- 230000005347 demagnetization Effects 0.000 claims description 19
- 230000001133 acceleration Effects 0.000 claims description 9
- 230000005669 field effect Effects 0.000 claims description 4
- 230000000903 blocking effect Effects 0.000 abstract description 11
- 238000010586 diagram Methods 0.000 description 13
- 238000000034 method Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
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- 230000000694 effects Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000010248 power generation Methods 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- 229920006395 saturated elastomer Polymers 0.000 description 1
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0006—Arrangements for supplying an adequate voltage to the control circuit of converters
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Abstract
The invention provides a novel isolated drive circuit, which is not influenced by the duty ratio of a primary side and has strong drive capability. According to the thought, a blocking capacitor in a primary side exciting circuit is removed, and only participates in constituting a primary side demagnetizing circuit. The primary side exciting circuit is composed of a primary side PWM (Pulse Width Modulation) control signal, a primary side voltage source, an isolation transformer primary winding and a primary side switching tube; when the primary side PWM control signal is of high level, the primary side switching tube is driven to be connected, the amplitude of the connection voltage of the switching tube is ignored, the voltages at the two ends of the primary side voltage source are directly added to the two ends of the isolation transformer primary winding, the voltages are coupled to a secondary side rectifying circuit by a transformer and rectified by the secondary side rectifying circuit to output a secondary side drive signal; when the turn ratio of the primary and secondary sides of the isolation transformer is 1, the high level amplitude of the drive signal is equal to the voltage amplitudes of the two ends of the primary side voltage source, and is irrelevant to the duty ratio of the primary side PWM signal.
Description
Technical Field
The invention relates to the field of circuits, in particular to a driving circuit for driving a switching device in a switching power supply system, and provides an isolation and control device.
Background
In recent years, energy problems are increasingly severe, new energy sources such as photovoltaic solar energy, wind power generation and the like are greatly supported by national policies, and the industry develops rapidly. The photovoltaic auxiliary power supply is a switch converter and is used for providing stable and reliable direct-current voltage for control systems such as photovoltaic solar energy, wind power generation, SVG and the like.
Under the influence of application occasions, the working voltage range of a photovoltaic power supply is wide, for example, a photovoltaic solar power station is influenced by illumination intensity, the output voltage of the photovoltaic solar power station ranges from dozens of volts to kilovolts, and the working voltage range of a corresponding auxiliary power supply is also from dozens of volts to kilovolts. The available technology of the photovoltaic auxiliary power supply comprises the schemes of double-tube flyback, double-tube forward excitation and the like, and the schemes are similar to full-bridge and half-bridge converters, and double-tube flyback and double-tube forward excitation circuits need an isolation driving circuit to drive and control a switching tube, so that the duty ratio change range corresponding to the double-tube flyback and double-tube forward excitation circuits is large due to the wide working voltage range, and the isolation driving circuit is difficult to design.
The existing isolation driving circuit in common use is different from the power circuit of forward topology in that the forward topology circuit is used for power transfer. The isolation driving circuit only realizes the driving control of the power switch tube (such as MOS tube, IGBT and the like) in topology and is mainly used for outputting control signals to the power switch tube.
Fig. 1a is a conventional isolation driving circuit, fig. 1b is a diagram of an application example of the isolation driving circuit in a forward converter, the isolation driving circuit is used for driving a power switching tube in a switching power supply system, and includes a primary side circuit and a secondary side rectifying circuit, wherein the primary side circuit includes a PWM controller, switching tubes TR1 and TR2 controlled by the PWM controller, a resistor R1, a primary side winding Np0 of a transformer, and a capacitor C1, the secondary side rectifying circuit includes a secondary side winding Ns0 and a resistor R2 of the transformer, a dotted end of the secondary side winding Ns0 of the transformer is led out through the resistor R2 to serve as an output end a of the isolation driving circuit, and is used for being connected with a gate of the power switching tube Q01; the synonym terminal of the secondary winding Ns0 of the transformer is led out as the output terminal B of the isolation driving circuit and is used for being connected with the source electrode of the power switch tube Q01. That is, the isolation driving output port A, B in fig. 1a is connected to the gate-source of the power switch Q01 in fig. 1b, and the isolation driving circuit shown in fig. 1a is only one module circuit in the circuit system shown in fig. 1 b.
In fig. 1a, PWM (pulse width modulation signal) is a control signal output by the control circuit, a totem pole is formed by an N-type triode TR1 and a P-type triode TR2 to improve the driving capability of the PWM signal, VCC is a totem pole dc supply voltage, a resistor R1 is a primary side current limiting resistor, C1 is a primary side dc blocking driving capacitor, T1 is an isolation transformer with a turn ratio of 1, R2 is a secondary side current limiting resistor, A, B is a secondary side driving signal output port, and VAB represents the voltage amplitude at both ends of the port AB. The circuit has obvious defects that: the high level amplitude of the secondary side isolation driving signal is influenced by the duty ratio of the primary side signal, the larger the duty ratio of the PWM signal is, the lower the high level amplitude of the secondary side driving signal is, and the secondary side switching tube is in danger of being incapable of driving; when the duty ratio of the PWM signal is small, the high level amplitude of the secondary side driving signal is higher, and the secondary side switching tube driving stage faces the forward breakdown risk.
The operation of the circuit of FIG. 1a will be briefly described with reference to the waveforms of the associated node voltages shown in FIG. 2. In fig. 2, the duty ratio of the driving signal is set to D, the high level amplitude is set to Vpwm, the VCC voltage is set to V0, the voltage across the dc blocking capacitor C1 is set to Vc0, and the polarity is positive left and negative right. When the driving signal is at a high level, the TR1 is turned on, the TR2 is turned off, the voltage at two ends of a primary winding Np0 of the isolation transformer is recorded as Vp0, then Vp0 is equal to V0-Vc0, and the product of the excitation voltage at two ends of the primary winding at this stage is Vp0 equal to D, so that in the excitation process of the transformer, the amplitude of the voltage at two ends of the primary winding Np0 is lower than the amplitude V0 of the primary voltage VCC under the influence of the duty ratio; the magnitude of the port voltage VAB of the secondary port A, B output from the secondary winding Ns0 is also lower than the magnitude V0 of the primary voltage VCC. When the driving signal is low level, TR2 is on, TR1 is off, the voltage across the primary winding of the isolation transformer is the voltage across the dc blocking capacitor C1, Vp0 is Vc0, and the product of demagnetizing voltage across the primary winding at this stage is Vp0 (1-D), so that in the demagnetizing process of the transformer, the transformer is affected by the energy stored by the capacitor at the excitation stage, and the reverse energy applied to the transformer in the demagnetization circuit formed by the resistor and the capacitor includes the residual magnetic energy in the transformer and the energy stored by the capacitor C1. From the volt-second equilibrium we can get: vp0 × D is Vp0 × D (1-D), and the voltage Vc0 across the dc blocking capacitor C1 is V0 × D and the high amplitude across the primary winding is V0 × 1-D, which can be calculated by this formula. In order to ensure that the amplitude of the secondary side driving signal can reach the threshold value of the switching tube to be driven, the duty ratio of the primary side PWM signal is generally lower than 50%.
Patent publication No. CN101621246A discloses a magnetic isolation driving circuit, which can avoid the malfunction of the main switch of the power circuit, and prevent the power supply from failing, but the drawback of the third winding adopted in this scheme is obvious: 1) the increase of the windings can lead to the increase of leakage inductance between the primary side and the secondary side and can lead to higher peak of a driving switch; 2) the scheme has complex design and high cost.
In view of the obvious disadvantages of the circuits, the inventor of the present invention has conducted an in-depth analysis on the isolated driving circuit, and the present invention has resulted from the results.
Disclosure of Invention
In view of the above, in order to solve the above technical problems, the present invention provides a novel isolation driving circuit with strong driving capability and without being affected by the magnitude of the primary side duty ratio.
Because the blocking capacitor participates in forming a primary side excitation circuit and a demagnetization circuit in the existing isolation driving circuit, because the blocking capacitor is connected in series for voltage division, the steady-state voltage at two ends of the blocking capacitor is equal to the product of the voltage amplitude at two ends of a primary side voltage source and the duty ratio of a primary side PWM control signal, and the steady-state voltage is influenced by the duty ratio of the primary side PWM; correspondingly, the high level amplitude transmitted to the secondary rectifying circuit through the isolation transformer is equal to the voltage at two ends of the primary voltage source minus the steady state voltage value at two ends of the blocking capacitor, and similarly, the high level amplitude of the secondary driving signal is influenced by the duty ratio of the primary PWM signal.
The idea of the invention is to remove a blocking capacitor in a primary side excitation circuit, and the capacitor only participates in forming a primary side demagnetization circuit. The primary side excitation circuit is composed of a primary side PWM control signal, a primary side voltage source, a primary side winding of the isolation transformer and a primary side switching tube; when the primary side PWM control signal is at a high level, the primary side switching tube is driven to be conducted, the conducting voltage amplitude of the switching tube is ignored, the voltages at two ends of the primary side voltage source are directly added at two ends of the primary side winding of the isolation transformer and are coupled to the secondary side rectifying circuit through the transformer, the secondary side driving signal is output after being rectified by the secondary side rectifying circuit, and when the primary side turn ratio and the secondary side turn ratio of the isolation transformer are 1, the high level amplitude of the driving signal is equal to the voltage amplitude at two ends of the primary side voltage source and is irrelevant to the duty ratio of the primary side PWM signal.
Accordingly, the invention provides an isolation driving circuit, which is used for driving a power switching tube in a switching power supply system and comprises a primary circuit and a secondary rectifying circuit, wherein the primary circuit comprises a PWM controller, an N-type switching tube Q1 controlled by the PWM controller, a primary winding of a transformer and a capacitor, the secondary rectifying circuit comprises a secondary winding of the transformer and a diode D2, and the dotted end of the secondary winding of the transformer is led out through the diode D2 to be used as a first output end of the isolation driving circuit and is used for being connected with a grid electrode of the power switching tube; and in the excitation circuit and the demagnetization circuit of the primary winding of the transformer, the capacitor only works in the demagnetization circuit and does not participate in excitation.
Preferably, the primary circuit further comprises a resistor R3 and a diode D1, wherein the dotted terminal of the transformer is led out to serve as the input terminal of the isolation driving circuit and is used for being connected with a voltage source; the synonym end of the transformer is grounded through an N-type switching tube Q1; one end of the capacitor is connected with the dotted terminal of the transformer, the other end of the capacitor is connected with the cathode of the diode, and the anode of the diode is connected with the dotted terminal of the transformer; the resistor is connected in parallel at two ends of the capacitor; the excitation circuit of the primary winding of the transformer only consists of a conduction path of an N-type switching tube Q1 and the primary winding; the demagnetization circuit of the primary winding of the transformer consists of a capacitor, a resistor, a diode and the primary winding when the N-type switching tube Q1 is turned off.
Preferably, the primary circuit further comprises a resistor R3 and a diode D1, wherein the dotted terminal of the transformer is led out to serve as the input terminal of the isolation driving circuit and is used for being connected with a voltage source; the synonym end of the transformer is grounded through an N-type switching tube Q1; the anode of the diode is connected with the synonym end of the transformer, the cathode of the diode is connected with one end of the capacitor, and the other end of the capacitor is grounded; the resistor is connected in parallel at two ends of the capacitor; the excitation circuit of the primary winding of the transformer only consists of a conduction path of an N-type switching tube Q1 and the primary winding; the demagnetization circuit of the primary winding of the transformer consists of the primary winding, a diode, a capacitor and a resistor when the N-type switching tube Q1 is turned off.
Preferably, the secondary side rectifying circuit further comprises an acceleration turn-off circuit, wherein the acceleration turn-off circuit is composed of a resistor R5, a resistor R6, a resistor R7 and a P-type switching tube Q2, one end of the resistor R5 is connected to the anode of the diode D2, and the other end of the resistor R5 is connected to the gate of the P-type switching tube Q2; one end of the resistor R6 is connected to the cathode of the diode D2, the other end of the resistor R7 is connected to the source of the P-type switching tube Q2, one end of the resistor R7 is connected to the drain of the P-type switching tube Q2, and the other end of the resistor R7 is connected to the synonym end of the secondary winding Ns1 of the transformer T1.
Preferably, the N-type switching tube Q1 is an NPN-type triode or an N-type field effect transistor; the P-type switching tube Q2 is a PNP type triode or a P-type field effect tube.
The primary side demagnetization circuit in the scheme demagnetizes the excitation energy of the isolation transformer, prevents the isolation transformer from being saturated and improves the reliability of the scheme of the invention.
Compared with the prior art, the invention has the following beneficial effects:
1) the high-level amplitude of the driving signal transmitted to the secondary side through the isolation transformer keeps constant in the whole duty ratio change range, is not influenced by the size of the duty ratio of the primary side, and has strong driving capability;
2) the duty ratio working range of the invention is wider, and can exceed 50 percent or even higher;
3) the scheme has high reliability, and can effectively prevent the failure of a power loop caused by the false turn-on of a drive circuit false trigger signal at the moment of instantaneous sudden change of a PWM signal sent by a control circuit;
4) the invention has the advantages of simple circuit, low cost, easy design and high reliability.
Drawings
FIG. 1a is a schematic diagram of a conventional isolated driving circuit;
FIG. 1b is a diagram illustrating an example of an isolated driving circuit applied to a forward converter;
FIG. 2 illustrates the operation principle of the prior art isolation driving circuit and the voltage waveform of the related loop;
FIG. 3 is a schematic circuit diagram according to a first embodiment of the present invention;
FIG. 4 illustrates an embodiment of the present invention, a related loop voltage waveform;
FIG. 5 is a schematic diagram of a second circuit according to the second embodiment of the present invention;
FIG. 6 is a second schematic circuit diagram according to a second embodiment of the present invention;
FIG. 7 is a third schematic circuit diagram according to a second embodiment of the present invention;
FIG. 8 is a schematic diagram of a third circuit of an embodiment of the present invention;
FIG. 9 is one of four schematic circuit diagrams according to an embodiment of the present invention;
FIG. 10 is a second schematic circuit diagram of a fourth embodiment of the present invention;
fig. 11 is a third schematic diagram of a fourth circuit according to the embodiment of the invention.
Detailed Description
First embodiment
Fig. 3 shows a schematic block diagram of a first embodiment of the present invention, a novel isolated driving circuit, which includes: the high-voltage direct-current power supply comprises a primary side PWM control signal, a duty ratio of the primary side PWM control signal is set to be D, a high-level amplitude value is recorded as Vpwm, a voltage source Vsource, a direct-current voltage value of the primary side PWM control signal is set to be VDD, a primary side excitation circuit, a primary side demagnetization circuit and an isolation transformer T1 assume that the turn ratio of a primary side to a negative side is 1, a secondary side rectification circuit and an acceleration turn-off circuit.
The primary side excitation circuit is composed of a voltage source Vsource, an N-type switching tube Q2, a resistor R3, a transformer T1 primary side winding Np1 and a PWM driving control signal, wherein the PWM is input to a grid electrode of the switching tube Q2 through the resistor R3 through the resistor driving signal; the positive pole of a voltage source Vsource (one end of the Vsource marked with "+" in FIG. 3), the same-name end (the end with the black point of the NP1 in FIG. 3) of a primary winding Np1 of a transformer T1, the different-name end (the end without the black point of the NP1 in FIG. 3) of a primary winding Np1 of a transformer T1 are connected to the drain of a switching tube Q2, the source of the switching tube Q2 is connected with the negative pole of the voltage source Vsource (the end of the Vsource marked with "-" in FIG. 3), and the common node is used as a primary ground.
The primary side de-magnetoelectric circuit consists of a diode D1, a resistor R4 and a capacitor C2, wherein the anode of the diode D1 is connected to the synonym terminal of a primary side winding Np1 of the transformer T1; the capacitor C2 and the resistor R4 are connected in parallel, and then one end of the capacitor C2 and the resistor R4 are connected to the anode of the voltage source Vsource, and the other end of the capacitor C2 and the resistor R4 are connected to the cathode of the diode D1.
The secondary side rectification circuit consists of a secondary side winding Ns1 of a transformer T1, a diode D2 and a port number C, D, wherein the same name end (the end with the black point of the winding Ns1 in the figure 3) of the secondary side winding Ns1 of the transformer T1 is connected with the anode of the diode D2, the different name end (the end without the black point of the winding Ns1 in the figure 3) of the secondary side winding Ns1 of the transformer T1 is connected to the port number D, and the cathode of the diode D2 is connected to the port number C.
The acceleration switching circuit consists of resistors R5, R6, R7 and a P-type switching tube Q2, wherein one end of the resistor R5 is connected to the anode of the diode D2, and the other end of the resistor R5 is connected to the grid electrode of the P-type switching tube Q2; one end of the resistor R6 is connected to the cathode of the diode D2, the other end is connected to the source of the P-type switch tube Q2, one end of the resistor R7 is connected to the drain of the P-type switch tube Q2, and the other end is connected to the synonym terminal of the secondary winding Ns1 of the transformer T1 (the end of the winding Ns1 without black dots in FIG. 3).
In particular, the reason for adding the accelerated shutdown circuit is: at the moment when the PWM signal changes from high level to low level, the voltage between the drain and the source of the switching tube Q1 has a gradual rising process, and the forward bias voltage of the reverse clamp diode D1 cannot be immediately established, so the voltage at the two ends of the primary winding of the isolation transformer cannot be immediately reversed at the moment when the driving signal is turned off, resulting in too long time of the falling edge of the turn-off of the driving signal output by the secondary port C, D, and further causing waveform distortion of the driving signal.
The beneficial effects of adding the accelerated turn-off circuit are as follows: in the stage that the primary side PWM signal is reduced from the high level to the low level, the reduction speed of the secondary side port C, D for reducing the driving signal from the high level to the low level is increased, the falling time of the driving signal is shortened, and further, the turn-off loss corresponding to the driving secondary side port C, D is reduced.
Referring to the connection relationship of the circuit shown in fig. 3, the following working principle is described in conjunction with the voltage and current waveforms of the relevant nodes of the circuit shown in fig. 4:
stage T0-T1: at the time of T0, a PWM signal is at a high level, a switching tube Q1 is switched on, a diode D1 is cut off in a reverse direction, the voltage at the same name end of a primary winding Np1 of a transformer T1 is positive, the voltage at the different name end of the primary winding Np1 is negative, the voltage at two ends of the primary winding Np1 is the voltage at two ends of a voltage source Vsource (the conduction voltage drop between the drain and the source of the switching tube Q1 is ignored), the voltage is marked as Vp 1; because of the coupling relation of the homonymous ends of the transformers, the voltage of the homonymous end of the secondary winding Ns1 of the transformer T1 is positive, the voltage of the heteronymous end of the transformer T1 is negative, the voltage of the two ends of the secondary winding Ns1 is equal to the voltage of the two ends of a voltage source Vsource (the conduction voltage drop between the drain and the source of the switching tube Q1 is ignored), and the amplitude is VDD;
the isolation driving circuit is different from the existing isolation driving circuit in that in the excitation stage, the output voltage of the direct current bias power supply is directly applied to two ends of the primary winding, and at the moment, a direct current blocking capacitor C2 does not form a path due to reverse bias of a diode, so that the primary voltage of the transformer is coupled to the secondary side in a full-amplitude mode, and therefore, the voltage at two ends of the primary winding and the secondary winding of the transformer is always equal to the output voltage of the direct current bias power supply and is irrelevant to the duty ratio of a PWM signal.
Further, the voltage across port C, D is denoted as VCD, as shown in FIG. 4. When the diode D2 is conducting in the forward direction, the voltage across the port C, D is at a high level and has a magnitude of VDD (ignoring the forward conduction voltage drop of the diode D2), and at this stage, the port C, D is always kept at a high level and has a magnitude of VDD, regardless of the duty ratio of the PWM signal.
Stage T1-T2: at the time of T1, the PWM signal falls to low level, the switching tube Q1 is turned off, the voltage across the primary winding Np1 of the transformer T1 is negative at the same name, the voltage across the different name is positive, the diode D1 is turned on in the forward direction, the voltage across the primary winding Np1 is the voltage across the capacitor C2, which is denoted as Vc2, as shown in fig. 4, the excitation energy of the primary winding Np1 of the transformer starts to be demagnetized at the previous stage.
In the demagnetization stage, in the working process of the scheme shown in fig. 1a, the exciting current of the primary inductor of the transformer is firstly reduced to zero in the forward direction and then increased in the reverse direction, and the amplitude of the reverse current is related to the capacity of the capacitor C1, the inductance of the primary winding of the isolation transformer, the direct-current voltage source and the duty ratio of the PWM signal. The working principle of the circuit of the scheme is obviously different from that of the circuit shown in fig. 1a at this stage in that: at the moment when the switching tube Q1 is turned off, the excitation current in the present scheme gradually decreases from the forward maximum value to the next moment when the switching tube Q1 is turned on, the current may be greater than or equal to zero, part of the excitation energy is consumed by the resistor R4, and there is no reverse excitation current provided by the capacitor C2, and there is only a freewheeling path, as shown by the dashed line in fig. 3.
At the moment that the switching tube Q1 is turned off, due to the relation of the same-name ends of the transformers, the same-name end of the secondary winding Ns1 of the transformer is negative, the voltage of the different-name end of the transformer is negative, the grid-source voltage of the P-type switching tube Q2 is negative, the switching tube Q2 is conducted, the resistors R6 and R7 are used for accelerating the voltage dropping speed of the two ends of the port C, D, and the port C, D is always kept in a low-level state in the whole stage from T1 to T2.
The high and low level states of the PWM signal are outputted to the driving port C, D through the isolated driving circuit shown in fig. 3 through two stages of T0-T1 and T1-T2, and the high and low level states of the port C, D are consistent with the PWM signal at any time.
Second embodiment
In the first embodiment, the N-type switching tube of the primary side excitation circuit shown in fig. 3 may also be an NPN-type triode, and the P-type switching tube of the secondary side acceleration and shutdown circuit may also be a PNP-type triode, which are arranged and combined as shown in fig. 5, 6 and 7, and the working principle of the adjusted circuit is the same as that of the first embodiment, thereby achieving the same effect.
Third embodiment
Fig. 8 shows a schematic block diagram of a third embodiment of the present invention, a novel isolated driving circuit, comprising: the primary side PWM control signal, the primary side excitation circuit, the primary side demagnetization circuit, the isolation transformer T1, the secondary side rectification circuit, and the acceleration turn-off circuit, the connection relationship of the circuit elements in this embodiment is only that the primary side demagnetization circuit is different from the first embodiment, and the other parts are completely the same, and the connection relationship of the primary side demagnetization circuit in this embodiment is:
the primary side de-magnetoelectric circuit consists of a diode D1, a resistor R4 and a capacitor C2, wherein the anode of the diode D1 is connected to the synonym terminal of a primary winding Np1 of a transformer T1 (the winding N in the figure 8)P1The end without black dots); the capacitor C2 and the resistor R4 are connected in parallel, and then one end of the capacitor C2 and one end of the resistor R4 are connected to the negative electrode of the voltage source Vsource (the end marked "-" by Vsource in fig. 8), and the other end of the capacitor C2 and the other end of the resistor R4 are connected to the cathode of the diode D1.
The operating principle of the adjusted circuit is basically the same as that of the first embodiment, and the difference is only in the demagnetization stage: the diode D1 is conducting in the forward direction and the voltage across the primary winding Np1 is equal to the difference between the voltage across the capacitor C2 minus the voltage across the dc voltage source Vsource, the demagnetization path being shown by the dashed line in fig. 8. The adjusted circuit has substantially the same function as the first embodiment.
Fourth embodiment
In the third embodiment, the N-type switching tube of the primary side excitation circuit shown in fig. 8 may also be an NPN-type triode, and the P-type switching tube of the secondary side acceleration and shutdown circuit may also be a PNP-type triode, which are arranged and combined as shown in fig. 9, 10 and 11, and the operating principle of the adjusted circuit is the same as that of the third embodiment, so that the same or similar effects can be achieved.
The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and it will be apparent to those skilled in the art that several modifications and decorations can be made without departing from the spirit and scope of the present invention, and these modifications and decorations should also be considered as the protection scope of the present invention, which is not described in detail by the embodiments herein, and the protection scope of the present invention should be subject to the scope defined by the claims.
Claims (5)
1. An isolation driving circuit is used for driving a power switch tube in a switching power supply system and comprises a primary side circuit and a secondary side rectifying circuit, wherein the primary side circuit comprises a PWM controller, an N-type switching tube Q1 controlled by the PWM controller, a primary side winding of a transformer and a capacitor, the secondary side rectifying circuit comprises a secondary side winding of the transformer and a diode D2, and the dotted end of the secondary side winding of the transformer is led out through a diode D2 to be used as a first output end of the isolation driving circuit and is used for being connected with a grid electrode of the power switch tube; the synonym end of the secondary winding of the transformer is led out to serve as a second output end of the isolation driving circuit and is used for being connected with a source electrode of the power switch tube, and the power switch tube is characterized in that:
in the excitation circuit and the demagnetization circuit of the primary winding of the transformer, the isolation driving circuit only works in the demagnetization circuit and does not participate in excitation.
2. The isolated drive circuit of claim 1, wherein: the primary side circuit also comprises a resistor R3 and a diode D1, wherein the dotted terminal of the transformer is led out to be used as the input terminal of the isolation driving circuit and is used for being connected with a voltage source; the synonym end of the transformer is grounded through an N-type switching tube Q1; one end of the capacitor is connected with the dotted terminal of the transformer, the other end of the capacitor is connected with the cathode of the diode, and the anode of the diode is connected with the dotted terminal of the transformer; the resistor is connected in parallel at two ends of the capacitor; wherein,
the excitation circuit of the primary winding of the transformer is only composed of a conduction path of an N-type switching tube Q1 and the primary winding;
the demagnetization circuit of the primary winding of the transformer consists of a capacitor, a resistor, a diode and the primary winding when the N-type switching tube Q1 is turned off.
3. The isolated drive circuit of claim 1, wherein: the primary side circuit also comprises a resistor R3 and a diode D1, wherein the dotted terminal of the transformer is led out to be used as the input terminal of the isolation driving circuit and is used for being connected with a voltage source; the synonym end of the transformer is grounded through an N-type switching tube Q1; the anode of the diode is connected with the synonym end of the transformer, the cathode of the diode is connected with one end of the capacitor, and the other end of the capacitor is grounded; the resistor is connected in parallel at two ends of the capacitor; wherein,
the excitation circuit of the primary winding of the transformer is only composed of a conduction path of an N-type switching tube Q1 and the primary winding;
the demagnetization circuit of the primary winding of the transformer consists of the primary winding, a diode, a capacitor and a resistor when the N-type switching tube Q1 is turned off.
4. The isolated drive circuit according to any one of claims 1 to 3, wherein: the secondary side rectifying circuit further comprises an acceleration turn-off circuit, wherein the acceleration turn-off circuit consists of a resistor R5, a resistor R6, a resistor R7 and a P-type switching tube Q2, one end of the resistor R5 is connected to the anode of a diode D2, and the other end of the resistor R5 is connected to the grid electrode of the P-type switching tube Q2; one end of the resistor R6 is connected to the cathode of the diode D2, the other end of the resistor R7 is connected to the source of the P-type switching tube Q2, one end of the resistor R7 is connected to the drain of the P-type switching tube Q2, and the other end of the resistor R7 is connected to the synonym end of the secondary winding Ns1 of the transformer T1.
5. The isolated drive circuit according to any one of claims 1 to 4, wherein: the N-type switching tube Q1 is an NPN-type triode or an N-type field effect tube; the P-type switching tube Q2 is a PNP type triode or a P-type field effect tube.
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| CN107359797A (en) * | 2017-08-21 | 2017-11-17 | 上海空间电源研究所 | Constant voltage and current limiting isolated drive circuit and control method for flash protection switch pipe |
| CN109391021A (en) * | 2018-11-27 | 2019-02-26 | 每天蓝(深圳)科技有限公司 | Cell anti-reverse fills the control device and solar energy MPPT control system of switch |
| CN110190736A (en) * | 2019-07-09 | 2019-08-30 | 杭州飞仕得科技有限公司 | A kind of multi signal Magnetic isolation transmission circuit and its application with high reliability |
| CN111371294A (en) * | 2020-04-03 | 2020-07-03 | 宁波安信数控技术有限公司 | Frequency spectrum shifting MOS drive circuit and method based on digital banner technology |
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| CN112003456A (en) * | 2020-07-14 | 2020-11-27 | 宁波安信数控技术有限公司 | Circuit for driving grid driving transformer |
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| CN113872419A (en) * | 2021-09-28 | 2021-12-31 | 成都芯源系统有限公司 | Isolation driving circuit and isolation driving method |
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Application publication date: 20160224 |