CN217216395U

CN217216395U - Novel full-bridge inverse soft switching circuit

Info

Publication number: CN217216395U
Application number: CN202220425683.5U
Authority: CN
Inventors: 许真剑
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-03-01
Filing date: 2022-03-01
Publication date: 2022-08-16
Anticipated expiration: 2032-03-01

Abstract

The utility model discloses a novel full-bridge contravariant soft switch circuit, it includes: the soft switch circuit is connected to the front end of the full-bridge inversion base circuit; the soft switching circuit is divided into a PWM (pulse-width modulation) type soft switching circuit and a frequency modulation type soft switching circuit according to different control modes; the driving circuit is used for driving the full-bridge inversion base circuit and the soft switching circuit; the purpose of high-frequency and soft switching is achieved, direct-through protection is achieved, direct-through loss caused by a freewheeling diode and an interelectrode capacitor is eliminated, a load inductor or a transformer can select a smaller iron core and inductance, and valuable materials such as the iron core and a copper wire winding are saved.

Description

Novel full-bridge inverse soft switching circuit

Technical Field

The utility model relates to the power electronics field especially involves a novel full-bridge contravariant soft switch circuit.

Background

The full-bridge inverter circuit and its soft switch function are generally used in high-power high-frequency devices, such as: switching power supply, induction heating equipment, electric welding machine, direct current fill electric pile etc..

The current common inversion methods include: single-ended flyback, single-ended forward, push-pull, half-bridge, full-bridge, etc., and related topologies of the above circuits. The main function of the soft switch is to replace the traditional hard switch, namely a switching tube (silicon controlled rectifier, mos tube, igbt and the like), because the hard switch is easy to burn out when working at high frequency and the waste of electric energy is serious.

Soft switching means zero voltage turn-on and zero current turn-off. Some components are added in the circuit, and meanwhile, the switching tube is controlled by a driving signal to manufacture a zero-voltage or zero-current state, so that the switching tube is switched on and off in the state, and further, the loss of the switching tube is greatly reduced.

The existing full-bridge inverter circuit has the problems that a large number of hard switches are used, so that the inverter circuit is large in damage and cannot run at high frequency, and a switching tube requires large current and high power; and the switching tubes at the two ends of the inductance bridge arm have direct connection risks, can be simultaneously switched on due to errors to cause short circuit, and also has direct connection loss to cause difficult high frequency. Due to the existence of interelectrode capacitance and a freewheeling diode, a mos tube or igbt is used inside, so that a fast recovery diode is turned from a forward direction to an inverted direction to be cut off, the recovery time of tens of nanoseconds to hundreds of nanoseconds is required, and the recovery time can pass a large reverse current, although the time is short, the influence on high-frequency operation is not negligible.

Accordingly, there is a need for a novel full-bridge inverter soft switching circuit that solves one or more of the above problems.

SUMMERY OF THE UTILITY MODEL

For solving one or more problems that exist among the prior art, the utility model provides a novel full-bridge contravariant soft switch circuit. The utility model discloses a solve the technical scheme that above-mentioned problem adopted and be: a novel full-bridge inverse soft switching circuit comprises: the full-bridge inversion base circuit is provided with two bridge arms and four switching tubes V1, V2, V3 and V4, wherein the switching tubes V1 and V2 are the same bridge arm, the switching tubes V3 and V4 are the same bridge arm, collectors of the switching tubes V1 and V3 are connected with the same input end, and emitters of the switching tubes V2 and V4 are connected with the same output end;

the soft switching circuit is respectively a PWM (pulse width modulation) type soft switching circuit and a frequency modulation type soft switching circuit, and is electrically connected to the front end of the full-bridge inverter basic circuit;

the driving circuit is electrically connected with the soft switching circuit and the full-bridge inversion basic circuit and is used for driving the soft switching circuit and the full-bridge inversion basic circuit;

the PWM-type soft switching circuit includes: the circuit comprises a first switch tube, a second switch tube, a first inductor, a first resistor, a fast recovery diode and a first capacitor, wherein the first switch tube and the first inductor are connected in series on a main circuit, the first resistor and the fast recovery diode are connected in series and are marked as a protection circuit, the protection circuit is connected in parallel with the first inductor, the protection circuit is connected in series with the first switch tube, the first capacitor and the second switch tube are connected in series and are marked as a working circuit, the working circuit is connected in parallel with the protection circuit, the working circuit is connected in series with the first switch tube, and the working circuit is connected in series with the first inductor;

after subtracting the second switch tube, the PWM type soft switch circuit becomes the frequency modulation type soft switch circuit.

Furthermore, a freewheeling diode or a capacitor is arranged in or outside the first switch tube and the second switch tube.

The utility model discloses the beneficial value who gains is: the utility model realizes the purpose of high frequency and soft switching function by connecting the soft switching circuit on the existing full-bridge inversion basic circuit, matching with the corresponding switch tube driving circuit and control method and dividing PWM type and frequency modulation type control circuits and methods according to different requirements, and obtains direct protection, eliminates direct loss caused by the freewheeling diode and the interelectrode capacitance, so that the load inductance or the transformer can select smaller iron core and inductance value, and saves valuable materials such as iron core and copper wire winding; the circuit has strong universality, does not need specific equipment or circuit for matching, has no specific requirement on a secondary side circuit of the transformer, and further greatly improves the compatibility; the second switch tube belongs to an auxiliary circuit and can be used in a small size, the switch tube in the full-bridge inversion basic circuit is switched in a soft switch mode after the first switch tube cuts off the main circuit, the loss is very low, and the switch tube can be used in a small size, so that the overall cost of the switch tube is reduced even if one first switch tube is added; when the energy-saving circuit is applied to a high-power circuit, the obtained energy-saving effect is more obvious. The utility model discloses a practical value has greatly improved above.

Drawings

Fig. 1 is an implementation schematic diagram I of the PWM-type soft switching circuit of the present invention;

fig. 2 is an implementation schematic II of the PWM soft switching circuit of the present invention;

fig. 3 is an implementation schematic diagram I of the frequency modulation soft switching circuit of the present invention;

fig. 4 is an implementation schematic diagram II of the frequency modulation soft switching circuit of the present invention;

fig. 5 is a schematic diagram III of the implementation of the frequency modulation soft switching circuit of the present invention;

fig. 6 is a waveform diagram of the PWM-type soft switching circuit according to the present invention;

fig. 7 is a waveform diagram of the frequency modulation soft switching circuit of the present invention.

Detailed Description

In order to make the above objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, as those skilled in the art will be able to make similar modifications without departing from the spirit and scope of the invention.

As shown in fig. 1-5, the utility model discloses a full-bridge inverter soft switching circuit, include: the full-bridge inversion base circuit is provided with two bridge arms and four switching tubes V1, V2, V3 and V4, wherein the switching tubes V1 and V2 are the same bridge arm, the switching tubes V3 and V4 are the same bridge arm, collectors of the switching tubes V1 and V3 are connected with the same input end, and emitters of the switching tubes V2 and V4 are connected with the same output end;

the PWM-type soft switching circuit includes: a first switch tube V0, a second switch tube Q0, a first inductor L0, a first resistor R01, a fast recovery diode D01 and a first capacitor C0, wherein the first switch tube V0 and the first inductor L0 are connected in series on a main circuit, the first resistor R01 and the fast recovery diode D01 are connected in series and are recorded as a protection circuit, the protection circuit is connected in parallel with the first inductor L0, the protection circuit is connected in series with the first switch tube V0, the first capacitor C0 and the second switch tube Q0 are connected in series and are recorded as a working circuit, the working circuit is connected in parallel with the protection circuit, the working circuit is connected in series with the first switch tube V0, and the working circuit is connected in series with the first inductor L0;

after subtracting the second switch Q0 (i.e. the working circuit does not include the second switch Q0, only the first capacitor C0), the PWM-type soft switching circuit becomes the frequency modulation-type soft switching circuit. The number of switching tubes in the driving circuit in fig. 1-5 is set according to the requirement.

It should be noted that the full-bridge inverter base circuit is a conventional technology, and may be modified in various ways. The first switch tube V0 generally needs to be a large switch tube, and the working frequency of the first capacitor C0 and the first inductor L0 is higher and lower; in the PWM type soft switching circuit, the second switching tube Q0 only bears the discharge current from the first capacitor C0, so the power consumption is not large, and a small-size switching tube is adopted. As shown in fig. 4 and 5, a freewheeling diode or a capacitor is connected in or outside the first and second switch tubes, and the capacitor and the freewheeling diode may be used instead of each other. The load L of the full-bridge inversion basic circuit comprises an inductor and a transformer.

It should be noted that the operation of the protection circuit is: in the event of a circuit fault, the first switching tube V0 needs to be turned off immediately, and at this time, if a hard switch is turned off, the fast recovery diode D01 is needed to freewheel the first inductor L0; the first resistor R01 is used to limit the reverse current generated when the first switch V0 is turned on, so that the recovery time of the fast recovery diode D01 is as small as possible to reduce the power consumption of the first resistor R01. Under the condition of normal operation, the power consumption of the first resistor R01 and the fast recovery diode D01 is small, and a small-size element can be selected.

And a control method of the full-bridge inversion soft switching circuit, which comprises the following steps: the switching of the two arms of the full-bridge inversion basic circuit is carried out under the condition that a first switch tube V0 is disconnected, a second switch tube Q0 is closed before a first switch tube V0 in the PWM type soft switch circuit is switched on, and the second switch tube Q0 is switched on before the first switch tube V0 is switched off;

when the soft switching circuit is the PWM type soft switching circuit, the working period of the full bridge is taken as T, and the control method comprises the following steps:

the first half cycle: the second switch tube Q0 is closed, the switch tubes V1 and V4 are turned on/off, then the switch tubes V3 and V2 are turned off/on, then the first switch tube V0 is turned on, after the first switch tube V0 is turned on for X microseconds, the second switch tube Q0 is turned on, then the first switch tube V0 is turned off, and then Y microseconds are delayed;

the following half cycle: the second switch tube Q0 is closed, the switch tubes V3 and V2 are turned on/off, then the switch tubes V1 and V4 are turned off/on, then the first switch tube V0 is turned on, after the first switch tube V0 is turned on for X microseconds, the second switch tube Q0 is turned on, then the first switch tube V0 is turned off, and then Y microseconds are delayed;

as described above, the switching order of the two arms can be reversed.

The steps of the upper half period and the lower half period are repeated as required, and X microseconds is the conduction time of the first switching tube V0 and the power-on time of the load in the upper half period and the lower half period. As shown in fig. 1, the load current is repeatedly switched from a to B and from B to a of the coil L, so that the load coil L obtains a high-frequency alternating current.

When the soft switching circuit is the frequency modulation type soft switching circuit, the working cycle of the full bridge is taken as T, and the control method comprises the following steps:

the first half cycle: the switching tubes V1 and V4 are switched on/off, then the switching tubes V3 and V2 are switched off/on, then the first switching tube V0 is switched on for X microseconds and then is switched off, and then Y microseconds are delayed;

the next half cycle: the switching tubes V3 and V2 are switched on/off, then the switching tubes V1 and V4 are switched off/on, then the first switching tube V0 is switched on for X microseconds and then is switched off, and then Y microseconds are delayed;

as described above, the switching order of the two arms can be reversed.

The steps of the upper half period and the lower half period are repeated as required, and X microseconds is the conduction time of the first switching tube V0 and is the power-on time of the load in the upper half period and the lower half period. As shown in fig. 3, the load current is repeatedly switched from a to B and from B to a of the coil L, so that the load coil L obtains a high-frequency alternating current.

It should be noted that X is less than 0.5T, and Y is equal to 0.5T-X. At shutdown, all the switching tubes are open. In order to better adapt to a use scene, when the input voltage and the output power change greatly, the PWM type soft switching circuit and the control method thereof are adopted; when the input voltage and the output power are not changed greatly, the frequency modulation type soft switching circuit and the control method thereof are adopted.

It should be noted that, in the PWM-type soft switching circuit and the control method thereof, the on-time X is used for regulating and controlling the output power, and the larger the value of X is, the larger the output power is, and conversely, the smaller the output power is. In the frequency modulation type soft switching circuit and the control method thereof, the output power is regulated and controlled by the working period T, the smaller the T, the higher the frequency, the higher the output power, and on the contrary, the lower the output power, when high frequency is needed, the smaller the first inductor L0 and the first capacitor C0 are selected, and the conduction time X can be very small; in particular, the smaller the frequency here, the longer the conduction time of the half cycle of the load coil L is, and thus the larger the iron core and the inductance are required, the conduction time is always X microseconds and is not changed, and the design and the type of the load coil L and the selection of the iron core and the inductance are only considered in this point.

Specifically, as shown in fig. 6, a cycle is entered when T is T1, at this time, the second switching tube Q0 is turned off, the switching tubes V1 and V4 are turned on, the switching tubes V2 and V3 are turned off, and then the first switching tube V0 is turned on. When the first switch tube V0 is turned on, the first inductor L0 generates an electromotive force as large as Vd to prevent sudden change of current, so that the first switch tube V0 can realize zero-voltage turn-on. After the first switching tube V0 is turned on, the current of the load coil L is continuously increased from a to B, and meanwhile, the freewheeling diode QD0 of the second switching tube Q0 charges the first capacitor C0, the voltage of the first capacitor C0 is continuously increased until the voltage is twice of the input voltage Vd, and then, because the second switching tube Q0 is turned off and the freewheeling diode QD0 thereof is blocked, the first capacitor C0 cannot discharge, the voltage Vc0 of the first capacitor is maintained at Vd which is 2 times that of the first capacitor, and the load coil L continuously obtains the current;

when T is T2, the second switching tube Q0 is turned on in a pilot mode when the first switching tube V0 is turned off, so that the first capacitor C0 discharges, the current of the first inductor L0 rapidly decreases, and the voltage Vc0 of the first capacitor also discharges to the load coil L and decreases, when the current of the first inductor L0 decreases to 0, the voltage Vc0 of the first capacitor is still higher than the input voltage Vd, then the first inductor L0 is turned off in a flyback mode, the current direction is leftward, the freewheeling diode D0 of the first switching tube is turned on, the first capacitor C0 discharges to the input power supply Vd, and at this time, the first switching tube V0 is driven to be turned off, and zero-current turn-off is realized;

after the first switch tube V0 is turned off, the first capacitor C0 and the parasitic capacitors of the switch tubes V3 and V2 discharge to the load coil L, and at this time, the load coil L attempts to maintain the original current, the current is large, the first capacitor C0 is small, the parasitic capacitors of the switch tubes V3 and V2 are small and can be discharged in a short time, the current time is equal to the capacitor capacity voltage according to the formula IT, and the current time can be within hundreds of nanoseconds through circuit design.

After the first capacitor C0 is discharged, the load coil L freewheels through a freewheeling diode D3 of a switching tube V3 and a switching tube V1 from point A to point B to point D3 to point V1 to point A. At the same time, the current flows through the switch tube V4 and the freewheeling diode D2 of the switch tube V2 from point A to point B to point V4 to point D2 to point A. At this time, the voltages at the two ends of the parasitic capacitors of the switching tubes V3 and V2 are discharged to zero. This state is maintained.

When T is T3, the second switching tube Q0 is turned off by the time of switching another half cycle, and the switching tubes V3 and V2 are turned on by the freewheeling of the load coil L, so that zero-voltage conduction is realized. Then, the switching tubes V1 and V4 are switched off, and in the switching-off process, since the voltage of the first capacitor C0 is 0 at this time, the freewheeling of the load coil L is switched to the first capacitor C0 to charge, so that the switching tubes V1 and V4 realize zero current switching-off. The loop of the L follow current is: point A-point B-D3-C0-D2-point A. When the second switch tube Q0 is turned on, the second switch tube Q0 only bears the discharge current of the first capacitor C0, and when the second switch tube Q0 is turned off, Vc0 is close to 0, so that the consumption is not large. The first switch tube V0 is turned on, and continues to perform the next half cycle, and the first switch tube V0 is turned off after being turned on for X microseconds, which is the same as the first half cycle.

It should be noted that, in a full bridge, it is possible to turn off the bridge arm that is being turned on first, and then turn on another pair of bridge arms that are still being turned off. If T is T3, the switching tubes V1 and V4 may be turned off first, and then the switching tubes V3 and V2 may be turned on, so that the soft switching process is as follows: the second switch tube Q0 is turned off, and then the switch tubes V1 and V4 are turned off, during the turn-off process, since the voltage of the first capacitor C0 is 0 at this time, the freewheeling of the load coil L is turned to the first capacitor C0, so that the switch tubes V1 and V4 realize zero current turn-off. The loop of the load coil L is: point A-point B-D3-C0-D2-point A. Then, before the process that the load coil L flows to charge the first capacitor C0 is not finished, the switching tubes V3 and V2 are turned on, and zero-voltage turning-on is realized.

In the PWM-type soft switching circuit, the values of the first capacitor C0 and the first inductor L0 cannot be selected to be too large, so that the resonant frequencies of the capacitors are larger and better, and the loss of the power-on duty ratio of the load coil L is reduced. The driving circuit can be realized by a single chip microcomputer or a PWM driving chip, an operational amplifier and a timer. When the singlechip is used, the stability is ensured by independently supplying power to the driving circuit, carrying out differential mode and common mode filtering, isolating, shielding by a metal shell and the like.

Specifically, as shown in fig. 6 and 7, fig. 7 is a waveform diagram of an operation of one cycle of the frequency modulation type soft switching circuit, and the operation principle of the soft switching implemented in fig. 6 and 7 is the same, but the high-frequency capability is stronger after the second switching tube is removed. Particularly, with reference to fig. 3, 4 and 7, after the first switching tube V0 is turned on, and the voltage of the first capacitor C0 rises to 2Vd, because the freewheeling diode D01 of the second switching tube Q0 is not blocked, the first capacitor C0 may discharge to cause the voltage to drop, the voltage of the first capacitor is not maintained at 2Vd, and then the first inductor L0 is flyback in a direction to the left, the freewheeling diode D0 of the first switching tube V0 is turned on, the first capacitor C0 discharges to the input power Vd, and the first switching tube V0 is turned off at this time, so that a soft switch is obtained.

When the first capacitor C0 discharges to the input power Vd in the frequency modulation type soft switching circuit, the current of the first inductor L0 is reversed, energy is fed back to the power, and the inductance magnetic flux is reset rapidly, so that the process takes a certain time, the load power-obtaining duty ratio is lost, but the frequency can be very high, and under the condition of the same power, the inductance and the magnetic core of the load coil L or the transformer can be still made smaller, and the material cost is saved.

To sum up, the utility model discloses a connect soft switch circuit on current full-bridge contravariant basic circuit, cooperate corresponding switch tube drive circuit and control method to divide PWM formula and frequency modulation formula control circuit, method to different demands, realized doing the purpose of high frequency and soft switching function, and obtain direct-through protection, eliminate the direct-through loss that freewheeling diode and interelectrode electric capacity brought, make load inductance or transformer can choose for use less iron core and inductance value, save valuable materials such as iron core and copper wire winding; the circuit has strong universality, does not need specific equipment or circuit for matching, has no specific requirement on a secondary side circuit of the transformer, and further greatly improves the compatibility; the second switch tube belongs to an auxiliary circuit and can be used in a small size, the switch tube in the full-bridge inversion basic circuit is switched in a soft switch mode after the first switch tube cuts off the main circuit, the loss is very low, and the switch tube can be used in a small size, so that the overall cost of the switch tube is reduced even if one first switch tube is added; when the energy-saving circuit is applied to a high-power circuit, the obtained energy-saving effect is more obvious. The utility model discloses a practical value has greatly improved above.

The embodiments described above merely represent one or more embodiments of the present invention, which are described in detail and concrete, but cannot be understood as limitations of the present invention. It should be noted that, for those skilled in the art, without departing from the concept of the present invention, several variations and modifications can be made, which all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A novel full-bridge inverse soft switching circuit comprises: the full-bridge inverter base circuit is characterized by comprising a soft switching circuit, a frequency modulation circuit and a PWM (pulse-width modulation) soft switching circuit, wherein the soft switching circuit is electrically connected to the front end of the full-bridge inverter base circuit;

2. The novel full-bridge inverter soft switching circuit according to claim 1, wherein a freewheeling diode or a capacitor is arranged in or outside the first switching tube and the second switching tube.