CN216564940U - Converter and positive feedback circuit thereof - Google Patents

Abstract

The utility model relates to the field of switching power supplies, and discloses a converter and a positive feedback circuit thereof, which are suitable for series circuits of two or more switching tubes, wherein the switching tubes are in series connection, a first input end of the positive feedback circuit is connected with a current inflow end of the switching tubes, a second input end of the positive feedback circuit is connected with a current outflow end of the switching tubes, and an output end of the positive feedback circuit is connected with a control end of the switching tubes; the positive feedback first input end and the second input end are used for sampling voltage signals rising from the current inflow end and the current outflow end when the switch tube is turned off; the output end of the positive feedback circuit is connected to the control end of the switch tube and used for discharging at the control end of the switch tube. In the turn-off process, the control end of the switching tube is always at a low level, so that the synchronous turn-off of the series switching tubes is realized. The utility model effectively solves the problem of inconsistent loss caused by asynchronous turn-off of the series switching tubes.

Description

Converter and positive feedback circuit thereof

Technical Field

The utility model relates to the field of switching power supplies, in particular to a converter and a positive feedback circuit thereof.

Background

In recent years, technologies such as solar power generation, wind power generation, and hydroelectric power generation have become mature. In a power generation control system and power transmission, the input voltage of the system is higher and higher, and the operating voltage of a power switch semiconductor device is also higher and higher. The existing power switch semiconductor is limited in the manufacturing process level, and the withstand voltage of the existing power switch semiconductor is difficult to reach the system voltage. For this reason, the use of low voltage power switch semiconductors in series to cope with the high input voltage of the system has slowly become the mainstream.

However, the switching tubes are connected in series, and the switching tubes are required to be synchronous. If the switch tube switches are asynchronous, the phenomena of inconsistent switch tube loss, inconsistent voltage sharing and the like due to inconsistent switches can occur, and the reliability of the switching power supply can be greatly reduced. The switching-on of the switching tube is influenced by the driving voltage, the driving resistor and the parasitic capacitor, the three factors are easy to control, and synchronous switching-on can be easily achieved. Therefore, the synchronous opening of the switching tubes has little influence on the series connection of the switching tubes. However, the turn-off of the switching tube is affected by parasitic capacitance, a discharge circuit, switching voltage and the like, and synchronous turn-off is difficult to achieve. The synchronous turn-off becomes a main factor influencing the series connection of the switching tubes, so that a method for solving the problem of inconsistent turn-off of the switching tubes is needed.

In order to solve the problem of inconsistent turn-off of the switching tube, a discharge circuit is added to the control end of the switching tube of a general power switching tube. The conventional discharge circuit has 2 types: 1 increasing the reverse diode discharge at the control terminal of the power device. 2, a discharge switch tube is added, when the driving signal disappears, the potential of the control end of the power switch tube is pulled down through the discharge switch tube, and accelerated turn-off is realized. Both of these approaches have significant disadvantages. In the two discharge circuits, the discharge signals are both driving signal ends. The drive signal end is the weak current pin, and when two kinds of modes were turned off, there was surge energy to introduce the drive signal end through parasitic capacitance from the switch tube high voltage end, makes the signal end oscillation, and the signal end oscillation can influence the effect of discharging, makes the switch tube can not turn off in step. Moreover, the surge energy may even break down the signal terminal when it is too large. For example, the power switch tube is an NMOS, and when the gate voltage drops to the turn-off voltage, the MOS starts to turn off, and the voltage between the drain and the source starts to rise. The parasitic capacitance of the drain and the gate starts to charge from the gate to the source, so that the gate potential rises relative to the source to cause oscillation, the turn-off time becomes longer, and the turn-off loss becomes larger. When the parasitic capacitance of the drain electrode and the grid electrode is overlarge, the switch tube is even turned on again in the turn-off process, so that the explosion is caused. In the switching power supply, the switching device is generally a MOS. When the MOS tube is driven in a floating mode, the potential of the source electrode changes during turn-off, so that more loops are formed by charging and discharging the parasitic capacitance of the drain electrode and the grid electrode through the grid electrode, and the switch tube driven in the floating mode and the switch tube driven in the ground mode are more difficult to achieve synchronous turn-off.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a positive feedback circuit, which solves the problem of inconsistent turn-off loss caused by asynchronous turn-off of a series switch tube.

In order to solve the technical problem, the utility model provides a converter, which comprises at least two switching tubes and at least one energy storage element, wherein the two switching tubes and the energy storage element are connected in series; the switch is also provided with at least one positive feedback circuit correspondingly connected with the switch tube;

the positive feedback circuit is provided with a first input end, a second input end and an output end, the first input end is connected to the current inflow end of the switch tube, the second input end is connected to the current outflow end of the switch tube, the output end is connected to the control end of the switch tube, and the positive feedback circuit is used for achieving simultaneous turn-off of the two switch tubes by accelerating reduction of voltage of the control end of the switch tube when the drive signal of the switch tube disappears.

In an embodiment, the positive feedback circuit includes a capacitor, a resistor, and an MOS transistor, one end of the capacitor is connected to the current inflow end of the switching transistor, and the connection point is a first input end of the positive feedback circuit; the other end of the capacitor is connected with one end of the resistor and the control end of the MOS tube; the other end of the resistor is connected with the current outflow end of the switch tube and the source electrode of the MOS tube, and the connection point is a second input end of the positive feedback circuit; the drain electrode of the MOS tube is connected to the control end of the switch tube, and the connection point is the output end of the positive feedback circuit;

when the driving signal of the switch tube disappears, the capacitor is charged, the voltage of the resistor is increased when the capacitor is charged, and after the voltage of the resistor reaches the switching-on threshold value of the MOS tube, the MOS tube is conducted, so that the voltage of the control end of the switch tube is reduced in an accelerated manner.

In one embodiment, the positive feedback circuit includes a capacitor and a triode; one end of the capacitor is connected with the current inflow end of the switching tube, and the connection point is a first input end of the positive feedback circuit; the other end of the capacitor is connected with the base electrode of the triode; the emitter of the triode is connected with the current outflow end of the switching tube, and the connection point is the second input end of the positive feedback circuit; the collector of the triode is connected with the control end of the switch tube, and the connection point is the output end of the positive feedback circuit;

when the driving signal of the switch tube disappears, the capacitor is charged, and when the charging current of the capacitor makes the base electrode and the emitting electrode of the triode forward biased, the triode is in saturated conduction, so that the voltage of the control end of the switch tube is reduced in an accelerated manner.

The utility model also provides a converter, which comprises at least two switching tubes and at least one energy storage element, wherein the two switching tubes are respectively a switching tube Q1 and a switching tube Q2, the switching tube Q1 and the switching tube Q2 are connected with the energy storage element in series, and the converter is also provided with a positive feedback circuit correspondingly connected with the switching tube Q1;

the positive feedback circuit is provided with a capacitor C1 and a switching tube Q3; one end of the capacitor C1 is connected to the current inflow end of the switch tube Q1; the other end of the capacitor C1 is connected to the control end of the switch tube Q3; the current outflow end of the switching tube Q3 is connected to the current outflow end of the switching tube Q1; the current inflow end of the switching tube Q3 is connected to the control end of the switching tube Q1.

In one embodiment, the converter is further provided with another positive feedback circuit, and the other positive feedback circuit is provided with a capacitor C2 and a switch tube Q4; one end of the capacitor C2 is connected to the current inflow end of the switch tube Q2; the other end of the capacitor C2 is connected to the control end of the switch tube Q4; the current outflow end of the switching tube Q4 is connected to the current outflow end of the switching tube Q2; the current inflow end of the switching tube Q3 is connected to the control end of the switching tube Q2.

In an embodiment, the switching tube Q3 and the switching tube Q4 are transistors, respectively.

In one embodiment, the switching transistor Q3 is a MOS transistor; the positive feedback circuit is further provided with a resistor R1, one end of the resistor R1 is connected to the control end of the switch tube Q3, and the other end of the resistor R1 is connected to the current outflow end of the switch tube Q3.

In one embodiment, the converter is further provided with a resistor R1a and a resistor R2 a; one end of the resistor R1a is connected with the control end of the switch tube Q1, and the other end of the resistor R1a is connected with the current outflow end of the switch tube Q1; one end of the resistor R2a is connected to the control end of the switch tube Q2, and the other end of the resistor R2a is connected to the current outflow end of the switch tube Q2.

The utility model further provides a positive feedback circuit, which is used in a converter, wherein the converter comprises at least two switching tubes and at least one energy storage element, the two switching tubes are respectively a switching tube Q1 and a switching tube Q2, and the switching tube Q1, the switching tube Q2 and the energy storage element are connected in series; the positive feedback circuit is provided with a capacitor and a switching tube Q3; one end of the capacitor is connected to the current outflow end of the switching tube Q1; the other end of the capacitor is connected to the control end of the switching tube Q3; the current inflow end of the switching tube Q3 is connected with the current inflow end of the switching tube Q1; the current outflow end of the switch tube Q3 is connected to the control end of the switch tube Q1.

The utility model further provides a converter, which comprises at least two switching tubes, wherein the two switching tubes are connected in series; the converter is also provided with at least one positive feedback circuit correspondingly connected with the switch tube;

the positive feedback circuit is provided with a first input end, a second input end and an output end, the first input end is connected with the current inflow end of the switch tube, the second input end is connected with the current outflow end of the switch tube, and the output end is connected with the control end of the switch tube; the positive feedback circuit is used for rapidly switching off the switch tube by accelerating to reduce the voltage of the control end of the switch tube when the driving signal of the switch tube disappears.

Compared with the prior art, the utility model has the following beneficial effects:

1. the utility model relates to a converter and a positive feedback circuit thereof, which are suitable for series circuits of two or more switching tubes; the switching tubes are connected in series. The first input end of the positive feedback circuit is connected with the current inflow end of the switch tube, the second input end of the positive feedback circuit is connected with the current outflow end of the switch tube, and the output end of the positive feedback circuit is connected with the control end of the switch tube; the first input end and the second input end of the positive feedback circuit are used for sampling voltage signals rising from the current inflow end and the current outflow end of the switch tube when the switch tube is switched off; the output end of the positive feedback circuit is connected to the control end of the switch tube and used for discharging at the control end of the switch tube. In the switching-off process of the switching tube, the control end of the switching tube always maintains a low level to realize synchronous switching-off of the series switching tube, so that the problem of inconsistent switching-off loss caused by inconsistent switching-off of the series switching tube is solved;

2. the converter and the positive feedback circuit thereof skillfully set the signal of the control end of the switch tube quickly by sampling the rising voltage signals of the current inflow end and the current outflow end of the switch tube when the switch tube is switched off, thereby achieving the effects of synchronous switching off and reducing the switching-off loss of the switch tube.

Interpretation of terms:

the control end of the switch tube: a port for controlling the switch to be switched on and off, for example, for an MOS transistor, a grid electrode of the MOS transistor is referred to; for a triode, the base of the triode is referred to.

The current inflow end of the switching tube is as follows: and after the switch is conducted, current flows into the port. For an N-MOS tube, the drain electrode of the N-MOS tube is referred to, and when the N-MOS tube is conducted, current flows from the drain electrode with high voltage to the source electrode with low voltage; for an NPN transistor, the collector of the transistor is referred to, and when conducting, current flows from the high voltage collector to the low voltage emitter.

Current outflow end of switching tube: after the switch is switched on, the port where the current flows out, such as for an N-MOS tube, refers to the source electrode of the N-MOS tube; for an NPN transistor, the emitter of the transistor is referred to.

Drawings

FIG. 1 is an equivalent circuit of a MOS transistor;

FIG. 2 is a block diagram of a positive feedback circuit according to a first embodiment of the present invention;

FIG. 3 is a schematic diagram of a positive feedback circuit according to a first embodiment of the present invention applied to a BUCK-BOOST converter;

FIG. 4 is a schematic diagram of a second embodiment of a positive feedback circuit applied to an overlapped flyback converter;

fig. 5 is a schematic diagram of an ac circuit breaker in which a positive feedback circuit according to a third embodiment of the present invention is applied to asynchronous switch driving.

Detailed Description

In order to make the utility model more clearly understood, the utility model is further described in detail below with reference to the attached drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.

Parasitic parameters exist in the semiconductor switch tube, wherein the parasitic capacitance has the most serious influence on the work of the semiconductor switch tube. Fig. 1 shows a parasitic capacitance equivalent circuit of a MOS transistor. A parasitic capacitance Cds exists between the drain and the source, a parasitic capacitance Cgs exists between the gate and the source, and a parasitic capacitance Cgd exists between the gate and the drain. When the MOS tube is turned off, the voltage between the drain electrode and the source electrode of the MOS tube rises, and the parasitic capacitance Cgd, the parasitic capacitance Cgs and the parasitic capacitance Cds of the MOS tube start to charge. When the parasitic capacitance Cgd is too large, the potential between the gate and the source of the MOS transistor is increased due to the series charging of the parasitic capacitance Cgd and the parasitic capacitance Cgs, so that the turn-off time is prolonged. When two or more MOS tubes are connected in series, due to the influence of parasitic capacitance and the voltage difference between the drain and the source of the MOS tubes, the problems of inconsistent turn-off and inconsistent loss caused by inconsistent discharge of the parasitic capacitance Cgs can occur.

First embodiment

Referring to fig. 2 and fig. 3, fig. 3 is a schematic diagram of the positive feedback circuit applied to the BUCK-BOOST converter according to the present invention. The BUCK-BOOST converter comprises a switching tube Q1, a switching tube Q2, an energy storage element, a resistor R1a, a resistor R2a and two positive feedback circuits, wherein the switching tube Q1 and the switching tube Q2 are connected in series, the MOS tubes are respectively used as the switching tube Q1, and the energy storage element is an inductor L. The source electrode of the switching tube Q1 is connected to the first end of the inductor L; the drain electrode of the switching tube Q2 is connected to the second end of the inductor L; one end of the resistor R1a is connected to the gate (control end) of the switching tube Q1, and the other end of the resistor R1a is connected to the source of the switching tube Q1; one end of the resistor R2a is connected to the gate of the switching tube Q2, and the other end of the resistor R2a is connected to the source of the switching tube Q2; the two positive feedback circuits are respectively a first positive feedback circuit and a second positive feedback circuit.

The first positive and negative feed circuit is composed of a capacitor C1, a resistor R1 and a switching tube Q3, wherein the switching tube Q3 is a MOS tube (hereinafter referred to as a MOS tube Q3); the connection relationship of the capacitor C1, the resistor R1 and the switching tube Q3 is as follows: one end of the capacitor C1 is connected to the drain (current inflow end) of the switch tube Q1, and the connection point is the first input end of the first positive feedback circuit; the other end of the capacitor C1 is connected to one end of the resistor R1 and the gate (control end) of the MOS transistor Q3; the other end of the resistor R1 is connected to the source (current outflow end) of the switching tube Q1 and the source (current outflow end) of the MOS tube Q3, and the connection point is the second input end of the first positive feedback circuit; the drain (current inflow end) of the MOS transistor Q3 is connected to the gate of the switch transistor Q1, and this connection point is the output end of the first positive feedback circuit.

The second positive and negative feed circuit is composed of a capacitor C2, a resistor R2 and a switching tube Q4, wherein the switching tube Q4 is a MOS (hereinafter referred to as MOS Q4), and the connection relationship between the capacitor C2, the resistor R2 and the MOS Q4 is as follows: one end of the capacitor C2 is connected to the drain (current inflow end) of the switch tube Q2, and the connection point is the first input end of the second positive feedback circuit; the other end of the capacitor C2 is connected to one end of the resistor R2 and the gate (control end) of the MOS transistor Q4; the other end of the resistor R2 is connected to the source (current flowing end) of the switching transistor Q2 and the source (current flowing end) of the MOS transistor Q4, and the connection point is the second input end of the second positive feedback circuit. The drain (current inflow end) of the MOS transistor Q4 is connected to the gate of the switching transistor Q2, and this connection point is the output end of the second positive feedback circuit.

The working processes of the first positive feedback circuit and the second positive feedback circuit are as follows: when the driving signal DRV1 of the switching tube Q1 and the switching tube Q2 disappears (no driving signal), the parasitic capacitance Cgs between the gate and the source of the switching tube Q1 and the switching tube Q2 starts to discharge through the resistor R1a and the resistor R2a, and the voltage between the gate and the source of the switching tube Q1 and the switching tube Q2 starts to drop. When the voltage between the gate and the source of the switching tube Q1 and the switching tube Q2 drops to the turn-off threshold thereof, the switching tube Q1 and the switching tube Q2 start to turn off. The voltage at point a in fig. 2 (i.e., the source of the switching transistor Q1) begins to drop due to freewheeling in the inductor L. The capacitor C1 charges the point a through the resistor R1 from the drain of the switching tube Q1, the voltage of the resistor R1 starts to rise, when the voltage reaches the on threshold of the MOS transistor Q3, the MOS transistor Q3 is turned on, the voltage between the gate and the source of the switching tube Q1 is pulled low, the capacitor C1, the resistor R1 and the MOS transistor Q3 form positive feedback for turning off the switching tube Q1, and turning off the switching tube Q1 is accelerated.

Similarly, when the voltages between the gate and the source of the switching transistor Q1 and the switching transistor Q2 drop to their turn-off thresholds, the switching transistor Q1 and the switching transistor Q2 start to turn off. The voltage at the point b in fig. 3 rises due to the freewheeling of the inductor L, the capacitor C2 is charged to ground through the resistor R2, the voltage of the resistor R2 starts to rise, and the MOS transistor Q4 is turned on when the voltage reaches the turn-on threshold of the MOS transistor Q4. The voltage between the grid electrode and the source electrode of the switching tube Q2 is pulled down, the capacitor C2, the resistor R2 and the MOS tube Q4 form positive feedback for the turn-off of the switching tube Q2, the turn-off of the switching tube Q2 is accelerated, and the synchronous turn-off of the switching tube Q2 and the switching tube Q1 is further realized.

By reasonably selecting the values of the capacitor C1 and the capacitor C2, the on-time of the MOS transistor Q3 and the on-time of the MOS transistor Q4 can be controlled, so that the off-time of the switching transistor Q1 and the switching transistor Q2 is controlled, and the purpose of synchronously turning off the switching transistor Q1 and the switching transistor Q2 is achieved.

In this embodiment, the first positive feedback circuit and the second positive feedback circuit are provided to achieve the purpose of synchronously turning off the switch Q1 and the switch Q2, and in other embodiments, only one positive feedback circuit may be provided to achieve the purpose of accelerating the turning off of the switch.

Second embodiment

Referring to fig. 4, fig. 4 is a schematic diagram of the positive feedback circuit applied to the overlapped flyback converter according to the present invention. The overlapped flyback converter comprises a switching tube Q1, a switching tube Q2, a transformer T1, a resistor R1a, a resistor R2a and two positive feedback circuits which are connected in series, wherein the two positive feedback circuits are a first positive feedback circuit and a second positive feedback circuit respectively.

The first positive and negative feed line is composed of a capacitor C1 and a switching tube Q3, wherein the switching tube Q3 is a transistor Q3 (hereinafter referred to as a transistor Q3); the connection relationship between the capacitor C1 and the triode Q3 is as follows: one end of the capacitor C1 is connected to the drain (current inflow end) of the switching tube Q1, and the connection point is the first input end of the positive feedback circuit; the other end of the capacitor C1 is connected with the base electrode of the triode Q3; an emitter (current outflow end) of the triode Q3 is connected with a source (current outflow end) of the switching tube Q1, and the connection point is a second input end of the first positive feedback circuit; the collector (current inflow terminal) of the transistor Q3 is connected to the gate of the switch Q1, and this connection point is the output terminal of the first positive feedback circuit.

The second positive and negative feed circuit is composed of a capacitor C2 and a switching tube Q4, wherein the switching tube Q4 is a transistor Q4 (hereinafter referred to as a transistor Q4); the connection relationship between the capacitor C2 and the triode Q4 is as follows: one end of the capacitor C2 is connected to the drain of the switch tube Q2, and the connection point is the first input end of the second positive feedback circuit; the other end of the capacitor C2 is connected with the base electrode of the triode Q4; an emitter of the triode Q4 is connected to a source of the switching tube Q2, and the connection point is a second input end of the second positive feedback circuit; the collector of the transistor Q4 is connected to the gate of the switch Q2, and the connection point is the output end of the two positive feedback circuits.

The operation principle of the first positive feedback circuit of the present embodiment is as follows:

as shown in fig. 4, when the driving signal DRV1 disappears, the inter-electrode parasitic capacitance Cgs between the gate and the source of the switching tube Q1 starts to discharge through the resistor R1a, and the voltage between the gate and the source of the switching tube Q1 starts to drop. When the voltage between the gate and the source of the switching tube Q1 drops to its off threshold, the switching tube Q1 starts to turn off. Due to the freewheeling of the transformer T1, the voltage between the drain and source of the switching tube Q1 begins to rise. The interelectrode parasitic capacitance Cgd of the switching tube Q1 is charged by the parasitic capacitance Cgs and the resistor R1a, so that the voltage drop between the gate and the source of the switching tube Q1 is slowed down, and the turn-off time is lengthened. The parasitic capacitance Cgd, the parasitic capacitance Cgs and the resistor R1a form negative feedback for the turn-off of the switching tube Q1, and the switching tube Q1 is prevented from being turned off. At the same time, the capacitor C1 is charged to point a through the diode between the base and emitter of transistor Q3. When the base and the emitter of the transistor Q3 are positively biased by the charging current of the capacitor C1, and the transistor Q3 enters a saturation state, the collector and the emitter of the transistor Q3 start to be turned on, the gate and the source of the switching tube Q1 are rapidly pulled low, the capacitor C1 and the transistor Q3 form positive feedback on the turn-off of the switching tube Q1, and the switching tube Q1 is accelerated to be turned off.

The operation principle of the second positive feedback circuit is the same as that of the first positive feedback circuit, and will not be described here. By reasonably selecting the values of the capacitor C1 and the capacitor C2, the on-time of the triode Q3 and the on-time of the triode Q4 can be controlled, so that the off-time of the switching tube Q1 and the switching tube Q2 is controlled, and the purpose of synchronously turning off the switching tube Q1 and the switching tube Q2 is achieved.

Third embodiment

Referring to fig. 5, fig. 5 is a schematic diagram of an ac circuit breaker with asynchronous switch driving according to the present invention. The alternating current circuit breaker comprises a switch tube Q1, a switch tube Q2, a contactor L1B, a resistor R1a, a resistor R2a and two positive feedback circuits which are connected in series, wherein the two positive feedback circuits are respectively a first positive feedback circuit and a second positive feedback circuit.

The operation principle of the first positive feedback circuit of the present embodiment is as follows:

a. the point b is an alternating current input end, and under the normal condition, when the alternating current input at the points a and b is positive, negative and positive, the driving signal DRV1 is at high level, and the current passes through the drain electrode of the Q1 from the point a to the source electrode, and then passes through the body diode of the switch tube Q2 to the contactor L1B to form a loop. When the alternating current input at the points a and b is negative, positive, negative and positive, the driving signal DRV2 is high, and the current flows through the contactor L1B from the point b, passes through the drain to the source of the switch tube Q2, and then passes through the body diode of the switch tube Q1 to the point a to form a loop.

The first positive and negative feed circuit is composed of a capacitor C1, a resistor R1 and a switching tube Q3, wherein the switching tube Q3 is a MOS tube (hereinafter referred to as MOS tube Q3); the connection relationship of the capacitor C1, the resistor R1 and the switching tube Q3 is as follows: one end of the capacitor C1 is connected to the drain (current inflow end) of the switch tube Q1, and the connection point is the first input end of the first positive feedback circuit; the other end of the capacitor C1 is connected to one end of the resistor R1 and the gate (control end) of the MOS transistor Q3; the other end of the resistor R1 is connected to the source (current outflow end) of the switching tube Q1 and the source (current outflow end) of the MOS tube Q3, and the connection point is the second input end of the first positive feedback circuit; the drain (current inflow end) of the MOS transistor Q3 is connected to the gate of the switch transistor Q1, and this connection point is the output end of the first positive feedback circuit.

When the alternating current input at the points a and b is positive, negative, and positive, the circuit fails, the DRV1 driving signal disappears, the parasitic capacitance Cgs between the gate and the source of the switching tube Q1 starts to discharge through the resistor R1a, and the voltage between the gate and the source of the switching tube Q1 starts to drop. When the voltage between the gate and the source of the switching tube Q1 drops to its off threshold, the switching tube Q1 starts to turn off. The voltage between the drain and source of Q1 begins to rise. The capacitor C1 forms a loop from the drain of the switch Q1 to the source of the switch Q1 through the resistor R1 for charging, the voltage of the resistor R1 starts to rise, when the voltage reaches the turn-on threshold of the MOS transistor Q3, the MOS transistor Q3 is turned on, the voltage between the gate and the source of the switch Q1 is pulled low, the capacitor C1, the resistor R1 and the MOS transistor Q3 form positive feedback for turning off the switch Q1, and turning off the switch Q1 is accelerated.

The second positive and negative feed circuit is composed of a capacitor C2, a resistor R2 and a switch tube Q4. The switching tube Q4 is a MOS tube (hereinafter referred to as a MOS tube Q4)), and the connection relationship among the capacitor C2, the resistor R2 and the MOS tube Q4 is: one end of the capacitor C2 is connected to the drain (current inflow end) of the switch tube Q2, and the connection point is the first input end of the second positive feedback circuit; the other end of the capacitor C2 is connected to one end of the resistor R2 and the gate (control end) of the MOS transistor Q4; the other end of the resistor R2 is connected to the source (current outflow end) of the switching transistor Q2 and the source (current outflow end) of the MOS transistor Q4, and this connection point is the second input end of the second positive feedback circuit. The drain (current inflow end) of the MOS transistor Q4 is connected to the gate of the switching transistor Q2, and this connection point is the output end of the second positive feedback circuit.

When the alternating current input at the points a and b is negative, the circuit is in a fault, the DRV2 driving signal disappears, the parasitic capacitance Cgs between the gate and the source of the switching tube Q2 starts to discharge through the resistor R2a, and the voltage between the gate and the source of the switching tube Q2 starts to drop. When the voltage between the gate and the source of the switching tube Q2 drops to its off threshold, the switching tube Q2 starts to turn off. The voltage between the drain and source of Q2 begins to rise. The capacitor C2 forms a loop from the drain of the switch Q2 to the source of the switch Q2 through the resistor R2 for charging, the voltage of the resistor R2 starts to rise, when the voltage reaches the turn-on threshold of the MOS transistor Q4, the MOS transistor Q4 is turned on, the voltage between the gate and the source of the switch Q2 is pulled low, the capacitor C2, the resistor R2 and the MOS transistor Q4 form positive feedback for turning off the switch Q2, and turning off the switch Q1 is accelerated.

The embodiments of the present invention are not limited thereto, and according to the above-mentioned contents of the present invention, the specific implementation circuit of the present invention can be modified, replaced or changed in various other forms without departing from the basic technical idea of the present invention.

Claims (10)

1. A converter comprises at least two switching tubes and at least one energy storage element, wherein the two switching tubes and the energy storage element are connected in series; the method is characterized in that: at least one positive feedback circuit correspondingly connected with the switch tube is also arranged;

the positive feedback circuit is provided with a first input end, a second input end and an output end, the first input end is connected with the current inflow end of the switch tube, the second input end is connected with the current outflow end of the switch tube, and the output end is connected with the control end of the switch tube; the positive feedback circuit is used for reducing the voltage of the control end of the switch tube in an accelerating manner when the driving signal of the switch tube disappears, so that the two switch tubes are switched off simultaneously.

2. The converter according to claim 1, wherein the positive feedback circuit comprises a capacitor, a resistor and a MOS transistor, one end of the capacitor is connected to the current inflow end of the switching transistor, and the connection point is the first input end of the positive feedback circuit; the other end of the capacitor is connected with one end of the resistor and the control end of the MOS tube; the other end of the resistor is connected to a current outflow end of the switch tube and a source electrode of the MOS tube, and the connection point is a second input end of the positive feedback circuit; the drain electrode of the MOS tube is connected to the control end of the switch tube, and the connection point is the output end of the positive feedback circuit;

when the driving signal of the switch tube disappears, the capacitor is charged, the voltage of the resistor is increased when the capacitor is charged, and after the voltage of the resistor reaches the switching-on threshold value of the MOS tube, the MOS tube is conducted, so that the voltage of the control end of the switch tube is reduced in an accelerated manner.

3. The converter of claim 1, wherein said positive feedback circuit comprises a capacitor and a transistor; one end of the capacitor is connected with the current inflow end of the switching tube, and the connection point is a first input end of the positive feedback circuit; the other end of the capacitor is connected with the base electrode of the triode; the emitter of the triode is connected with the current outflow end of the switching tube, and the connection point is the second input end of the positive feedback circuit; the collector of the triode is connected with the control end of the switch tube, and the connection point is the output end of the positive feedback circuit;

when the driving signal of the switching tube disappears, the capacitor is charged, and when the charging current of the capacitor enables the base electrode and the emitting electrode of the triode to be positively biased, the triode is in saturated conduction, so that the voltage of the control end of the switching tube is reduced in an accelerated manner.

4. A converter, comprising at least two switching tubes and at least one energy storage element, the two switching tubes are a switching tube Q1 and a switching tube Q2, the switching tube Q1 and the switching tube Q2 are connected in series with the energy storage element, and the converter is characterized in that: a positive feedback circuit correspondingly connected with the switching tube Q1 is also arranged;

the positive feedback circuit is provided with a capacitor C1 and a switching tube Q3; one end of the capacitor C1 is connected to the current inflow end of the switch tube Q1; the other end of the capacitor C1 is connected to the control end of the switch tube Q3; the current outflow end of the switching tube Q3 is connected to the current outflow end of the switching tube Q1; the current inflow end of the switching tube Q3 is connected to the control end of the switching tube Q1.

5. The converter according to claim 4, wherein there is further provided another positive feedback circuit having a capacitor C2 and a switch Q4; one end of the capacitor C2 is connected to the current inflow end of the switch tube Q2; the other end of the capacitor C2 is connected to the control end of the switch tube Q4; the current outflow end of the switching tube Q4 is connected to the current outflow end of the switching tube Q2; the current inflow end of the switching tube Q3 is connected to the control end of the switching tube Q2.

6. The converter according to claim 4, wherein the switch transistor Q3 and the switch transistor Q4 are triodes.

7. The converter according to claim 4, wherein the switching tube Q3 is a MOS tube; the positive feedback circuit is further provided with a resistor R1, one end of the resistor R1 is connected to the control end of the switch tube Q3, and the other end of the resistor R1 is connected to the current outflow end of the switch tube Q3.

8. The converter according to claim 4, characterized in that a resistor R1a and a resistor R2a are further provided; one end of the resistor R1a is connected with the control end of the switch tube Q1, and the other end of the resistor R1a is connected with the current outflow end of the switch tube Q1; one end of the resistor R2a is connected to the control end of the switch tube Q2, and the other end of the resistor R2a is connected to the current outflow end of the switch tube Q2.

9. A positive feedback circuit is used in a converter, the converter comprises at least two switching tubes and at least one energy storage element, the two switching tubes are a switching tube Q1 and a switching tube Q2 respectively, and the switching tube Q1, the switching tube Q2 and the energy storage element are connected in series; the positive feedback circuit is characterized by comprising a capacitor and a switching tube Q3; one end of the capacitor is connected to the current outflow end of the switching tube Q1; the other end of the capacitor is connected to the control end of the switching tube Q3; the current inflow end of the switching tube Q3 is connected with the current inflow end of the switching tube Q1; the current outflow end of the switch tube Q3 is connected to the control end of the switch tube Q1.

10. A converter comprises at least two switching tubes, wherein the two switching tubes are connected in series; the method is characterized in that: at least one positive feedback circuit correspondingly connected with the switch tube is also arranged;

the positive feedback circuit is provided with a first input end, a second input end and an output end, the first input end is connected with the current inflow end of the switch tube, the second input end is connected with the current outflow end of the switch tube, and the output end is connected with the control end of the switch tube; the positive feedback circuit is used for rapidly switching off the switch tube by accelerating to reduce the voltage of the control end of the switch tube when the driving signal of the switch tube disappears.

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