CN114553040A - Full-bridge inverse soft switching circuit and control method - Google Patents

Full-bridge inverse soft switching circuit and control method Download PDF

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Publication number
CN114553040A
CN114553040A CN202210194032.4A CN202210194032A CN114553040A CN 114553040 A CN114553040 A CN 114553040A CN 202210194032 A CN202210194032 A CN 202210194032A CN 114553040 A CN114553040 A CN 114553040A
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circuit
switching
switched
tube
full
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许真剑
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Priority to CN202210194032.4A priority Critical patent/CN114553040A/en
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Priority to PCT/CN2023/076721 priority patent/WO2023165346A1/en
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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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • 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
    • H02M1/083—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the ignition at the zero crossing of the voltage or the current
    • 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
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • 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
    • H02M1/38—Means for preventing simultaneous conduction of switches
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention discloses a full-bridge inverse soft switching circuit, which comprises: 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 control method comprises PWM and frequency modulation control methods; 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

Full-bridge inverse soft switching circuit and control method
Technical Field
The invention relates to the field of power electronics, in particular to a full-bridge inverter soft switching circuit and a control method.
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. The fast recovery diode is turned from the forward direction to the reverse direction to be cut off due to the existence of interelectrode capacitance and a freewheeling diode which internally use the mos tube or the igbt, the recovery time of dozens to hundreds of nanoseconds is needed, and the recovery time can pass a large reverse current, although the recovery time is short, the influence on the high-frequency operation is not negligible.
Therefore, a full-bridge inverter soft switching circuit and a control method thereof are needed to solve one or more of the above problems.
Disclosure of Invention
The invention provides a full-bridge inverse soft switching circuit and a control method thereof, aiming at solving one or more problems in the prior art. The technical scheme adopted by the invention for solving the problems is as follows: a full-bridge inverter soft switching circuit, comprising: 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 switching of two bridge arms of the full-bridge inversion basic circuit is carried out under the condition that a first switching tube is disconnected, a second switching tube is closed before the first switching tube in the PWM type soft switching circuit is connected, and the first switching tube is connected before the first switching tube is disconnected;
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 is closed, the switch tubes V1 and V4 are switched on/off, then the switch tubes V3 and V2 are switched off/on, then the first switch tube is switched on, the second switch tube is switched on after the first switch tube is switched on for X microseconds, then the first switch tube is switched off, and then Y microseconds are delayed;
the following half cycle: the second switch tube is closed, the switch tubes V3 and V2 are switched on/off, then the switch tubes V1 and V4 are switched off/on, then the first switch tube is switched on, the second switch tube is switched on after the first switch tube is switched on for X microseconds, then the first switch tube is switched off, and then Y microseconds are delayed;
the steps of the upper half period and the lower half period are repeatedly cycled as required, and X microseconds is the conduction time of the first switching tube and the power-on time of the load in the upper half period and the lower half period.
Further, when the soft switching circuit is the frequency modulation soft switching circuit, the duty 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 is switched on for X microseconds and then is switched off, and then Y microseconds are delayed;
the following 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 is switched on for X microseconds and then is switched off, and then Y microseconds are delayed;
the steps of the upper half period and the lower half period are repeatedly cycled as required, and X microseconds is the conduction time of the first switching tube and the power-on time of the load in the upper half period and the lower half period.
Furthermore, the value of X is less than 0.5T, and Y is equal to 0.5T-X.
Further, when the machine is stopped, all the switch tubes are disconnected.
Further, 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.
The invention has the following beneficial values: the soft switching circuit is connected to the existing full-bridge inversion basic circuit, the corresponding switching tube driving circuit and the control method are matched, and the PWM type and frequency modulation type control circuits and methods are divided according to different requirements, so that the purpose of performing high-frequency and soft switching functions is achieved, direct-connection protection is obtained, direct-connection 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 precious materials such as the iron core and copper wire windings are saved; 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 practical value of the invention is greatly improved.
Drawings
FIG. 1 is a schematic diagram I of an embodiment of a PWM-type soft switching circuit according to the present invention;
FIG. 2 is a schematic diagram II of an embodiment of the PWM-type soft switching circuit of the present invention;
FIG. 3 is a schematic diagram I of an embodiment of the frequency-modulated soft switching circuit of the present invention;
FIG. 4 is a schematic diagram II of an embodiment of a frequency modulated soft switching circuit according to the present invention;
FIG. 5 is a schematic diagram III of an embodiment of a frequency modulated soft switching circuit according to the present invention;
FIG. 6 is a waveform diagram of an embodiment of a PWM-type soft switching circuit according to the present invention;
FIG. 7 is a waveform diagram of an implementation of the FM soft switching circuit of the present invention.
Detailed Description
In order to make the aforementioned 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. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
As shown in fig. 1 to 5, the present invention discloses a full-bridge inverse soft switching circuit, which includes: 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: 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 to 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 an operating circuit, the operating circuit is connected in parallel with the protection circuit, the operating circuit is connected in series with the first switch tube V0, and the operating 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, and 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 larger and smaller; 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, the first and second switch tubes are internally or externally connected with a freewheeling diode or a capacitor, and the capacitor and the freewheeling diode can 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 failure, 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 tube 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 is connected in the PWM type soft switch circuit, and the second switch tube Q0 is connected in a pilot mode before the first switch tube V0 is disconnected;
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, the second switch tube Q0 is turned on after the first switch tube V0 is turned on for X microseconds, then the first switch tube V0 is turned off, and then Y microseconds are delayed;
the next 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, the second switch tube Q0 is turned on after the first switch tube V0 is turned on for X microseconds, 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 following 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 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 is, the longer the conduction time of the half cycle of the load coil L is, and thus the larger the iron core and 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 required to be considered.
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 simultaneously the freewheeling diode QD0 of the second switching tube Q0 charges the first capacitor C0, and after the voltage of the first capacitor C0 is continuously increased to twice the input voltage Vd, 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, 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 off-time of the first switching tube V0 is reached, so that the first capacitor C0 discharges, the current of the first inductor L0 rapidly drops, and the voltage Vc0 of the first capacitor also discharges to the load coil L and drops, when the current of the first inductor L0 drops 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 switching tube V0 is turned off, the first capacitor C0 and the parasitic capacitors of the switching 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 switching 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 the switching tube V3 and the switching tube V1, and the voltage of the load coil L is 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 for the other half cycle, and the switching tubes V3 and V2 are turned on by the follow current of the load coil L, thereby achieving zero-voltage conduction. And then the switching tubes V1 and V4 are disconnected, and in the disconnection process, because the voltage of the first capacitor C0 is 0 at the moment, the follow current of the load coil L is converted to the first capacitor C0 to be charged, so that the switching tubes V1 and V4 realize zero current disconnection. 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, it only bears the discharge current of the first capacitor C0, and when it is turned off, Vc0 is close to 0, so that it is not consumed much. 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 can be turned off first, and then the switching tubes V3 and V2 can 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 turn-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. Specifically, 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 drop the voltage, 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 soft switching is achieved.
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.
In summary, the soft switching circuit is connected to the existing full-bridge inversion basic circuit, the corresponding switching tube driving circuit and the control method are matched, and the PWM type and frequency modulation type control circuits and methods are divided according to different requirements, so that the purpose of performing high-frequency and soft switching functions is achieved, direct-through protection is obtained, direct-through loss caused by a freewheeling diode and an inter-electrode 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; 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 practical value of the invention is greatly improved.
The above-described examples merely represent one or more embodiments of the present invention, which are described in greater detail and detail, but are not to be construed as limiting the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the spirit of the invention, which falls within the scope of the invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims (7)

1. A full-bridge inverter soft switching circuit, comprising: 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, the collectors of the switching tubes V1 and V3 are connected with the same input end, and the emitters of the switching tubes V2 and V4 are connected with the same output end, and the full-bridge inversion base circuit is characterized in that the soft switching circuits are respectively a PWM (pulse-width modulation) type soft switching circuit and a frequency modulation type soft switching circuit and are electrically connected to the front end of the full-bridge inversion base 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.
2. The full-bridge inverter soft-switching circuit according to claim 1, wherein a freewheeling diode or a capacitor is disposed inside or outside the first switching tube and the second switching tube.
3. A control method of a full-bridge inversion soft switching circuit is characterized in that switching of two bridge arms of the full-bridge inversion basic circuit is carried out under the condition that a first switching tube is disconnected, a second switching tube is closed before the first switching tube is connected in a PWM (pulse-width modulation) type soft switching circuit, and the second switching tube is connected in a pilot mode before the first switching tube is disconnected;
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 is closed, the switch tubes V1 and V4 are switched on/off, then the switch tubes V3 and V2 are switched off/on, then the first switch tube is switched on, the second switch tube is switched on after the first switch tube is switched on for X microseconds, then the first switch tube is switched off, and then Y microseconds are delayed;
the following half cycle: the second switch tube is closed, the switch tubes V3 and V2 are switched on/off, then the switch tubes V1 and V4 are switched off/on, then the first switch tube is switched on, the second switch tube is switched on after the first switch tube is switched on for X microseconds, then the first switch tube is switched off, and then Y microseconds are delayed;
the steps of the upper half period and the lower half period are repeatedly cycled as required, and X microseconds is the conduction time of the first switching tube and the power-on time of the load in the upper half period and the lower half period.
4. The method for controlling the full-bridge inverter soft switching circuit according to claim 3, wherein when the soft switching circuit is a frequency modulation soft switching circuit, the duty cycle of the full bridge is T, and the method comprises:
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 is switched on for X microseconds and then is switched off, and then Y microseconds are delayed;
the following 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 is switched on for X microseconds and then is switched off, and then Y microseconds are delayed;
the steps of the upper half period and the lower half period are repeatedly cycled as required, and X microseconds is the conduction time of the first switching tube and the power-on time of the load in the upper half period and the lower half period.
5. The method as claimed in claim 3 or 4, wherein X is less than 0.5T and Y is equal to 0.5T-X.
6. The method as claimed in claim 3, wherein all the switch tubes are turned off during shutdown.
7. The method for controlling the full-bridge inverter soft switching circuit according to claim 4, wherein the PWM soft switching circuit and the control method thereof are adopted when the input voltage and the output power have large changes;
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.
CN202210194032.4A 2022-03-01 2022-03-01 Full-bridge inverse soft switching circuit and control method Pending CN114553040A (en)

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WO2023165346A1 (en) * 2022-03-01 2023-09-07 许真剑 Full-bridge inverter soft switching circuit and control method

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CN102231600A (en) * 2011-07-08 2011-11-02 南京航空航天大学 Novel full-bridge soft switch circuit applied to arc welding inverter power supply
WO2017201209A1 (en) * 2016-05-17 2017-11-23 Georgia Tech Research Corporation Soft switching solid state transformers and converters
CN111711378A (en) * 2020-06-22 2020-09-25 中国人民解放军海军工程大学 Soft switching inverter
CN114553040A (en) * 2022-03-01 2022-05-27 许真剑 Full-bridge inverse soft switching circuit and control method

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* Cited by examiner, † Cited by third party
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WO2023165346A1 (en) * 2022-03-01 2023-09-07 许真剑 Full-bridge inverter soft switching circuit and control method

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