Switch control circuit, method and power supply circuit

Abstract

The present invention discloses a switch control circuit, method and power supply circuit, the switch control circuit comprises: a resonance module, a first end of which is connected to the first end of a bus capacitor, a second end of which is connected to the positive input terminal of an inverter circuit, and a third end of which is connected between the second end of the bus capacitor and the negative input terminal of the inverter circuit; the resonance module is used to store the electric energy released by the rectifier circuit and the buffer capacitor, and based on the electric energy, before the switch device in the inverter circuit is turned on, the freewheeling diode inside the switch device is controlled to be turned on, so that the voltage drop at both ends of the switch device is zero; the buffer capacitor is correspondingly arranged at both ends of each switch device in the inverter circuit, and is used to release electric energy to the resonance module, and control the voltage at both ends of the switch device to remain zero after the switch device is turned on and before the switch device is turned off. Through the present invention, zero voltage soft turn-on and soft turn-off can be achieved, device loss can be reduced, and the reliability of the inverter can be improved.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a switch control circuit, method and power supply circuit. Background Art

[0002] Figure 1 The topological structure diagram of the existing power supply circuit is as follows: Figure 1 As shown, no soft switching control scheme is designed for the switching devices in the inverter circuit. Therefore, the switching devices are turned on or off under load, that is, when the switching devices are turned on or off, the voltage across the two ends or the current passing through the switching devices is not zero. In the process of the switching devices being turned on or off under load, switching losses may be caused, and even the switches may be damaged, thereby reducing device reliability.

[0003] With regard to the problem in the prior art that the switching device of the inverter circuit is turned on or off under load, resulting in low reliability, no effective solution has been proposed so far. Summary of the invention

[0004] The embodiments of the present invention provide a switch control circuit, method and power supply circuit to solve the problem in the prior art that the switch device of the inverter circuit is turned on or off under load, resulting in low reliability.

[0005] In order to solve the above technical problems, the present invention provides a switch control circuit, which is applied to a power supply circuit, wherein the power supply circuit includes a rectifier circuit, a bus capacitor and an inverter circuit, and is characterized in that the switch control circuit includes:

[0006] A resonance module, a first end of which is connected to the first end of the bus capacitor, a second end of which is connected to the positive input terminal of the inverter circuit, and a third end of which is connected between the second end of the bus capacitor and the negative input terminal of the inverter circuit; the resonance module is used to store the electric energy released by the rectifier circuit and the buffer capacitor, and before the switch device in the inverter circuit is turned on based on the electric energy, control the freewheeling diode inside the switch device to turn on, so that the voltage drop across the switch device is zero;

[0007] The buffer capacitor is correspondingly arranged at both ends of each switching device in the inverter circuit, and is used to release electric energy to the resonance module, and control the voltage at both ends of the switching device to remain zero after the switching device is turned on and before the switching device is turned off.

[0008] Furthermore, the resonance module comprises:

[0009] A first switch module, a first end of which is connected to the first end of the bus capacitor, and a second end of which is connected to the positive input terminal of the inverter circuit;

[0010] A second switch module, a first end of which is connected between the second end of the first switch module and the positive input terminal of the inverter circuit, and a second end of which is connected to the first end of the resonant capacitor;

[0011] The resonant capacitor; a second end of which is connected to the first end of the resonant inductor, and is used to release electric energy to the resonant inductor, or to store the electric energy released by the resonant inductor;

[0012] The resonant inductor has a second end connected between the second end of the bus capacitor and the negative input terminal of the inverter circuit.

[0013] Furthermore, the first switch module is used to conduct forward before the switch device is turned on, and control the rectifier circuit to output an initial voltage to the inverter circuit;

[0014] The second switch module is used to conduct forward after the first switch module is conducted forward, and control the rectifier circuit to charge the resonant capacitor and the resonant inductor;

[0015] The first switch module is further configured to be switched off after the second switch module when the current of the resonant inductor increases to a preset current threshold;

[0016] The buffer capacitor is specifically used to release electric energy to the resonant capacitor and the resonant inductor when the first switch module is turned off and the second switch module is forwardly conducted;

[0017] The resonant inductor is used to release the electric energy to the resonant capacitor after all the electric energy in the buffer capacitor is released and the voltage drop across the inverter circuit is zero, and at the same time, the freewheeling diode inside the switch device is turned on, thereby making the voltage drop across the switch device zero;

[0018] The second switch module is further used for reverse conduction after the resonant inductor finishes releasing electric energy to the resonant capacitor, so that the resonant capacitor releases electric energy to the resonant inductor; wherein, after the second switch module is reversely conducted, the switch device is turned on.

[0019] Furthermore, the inverter circuit is specifically used to keep the voltage across itself at zero before the electric energy of the resonant capacitor is completely released to the resonant inductor; wherein, when the electric energy of the resonant capacitor is completely released to the resonant inductor, the switch device is controlled to be turned off.

[0020] Furthermore, the resonance module further includes:

[0021] a unidirectional diode, wherein the anode of the diode is connected between the first end of the second switch module and the positive input terminal of the inverter circuit, and the cathode of the diode is connected between the second end of the resonant capacitor and the first end of the resonant inductor;

[0022] The unidirectional diode is used to: turn on after the switch device is turned off, control the resonant inductor to release electric energy to the buffer capacitor, and increase the voltage across the inverter circuit.

[0023] Furthermore, the first switch module is also used to: conduct reversely after the voltage at both ends of the inverter circuit rises to an initial voltage, so that the resonant inductor releases electrical energy to the bus capacitor; and conduct forwardly after the current of the resonant inductor decreases to zero.

[0024] Furthermore, the first switch module includes: a first unidirectional diode and a first switch tube connected in reverse parallel;

[0025] Forward conduction of the first switch module means that the first switch tube is turned on and the first unidirectional diode is turned off; reverse conduction of the first switch module means that the first switch tube is turned off and the first unidirectional diode is turned on; and shutdown of the first switch module means that the first switch tube is turned off and the first unidirectional diode is turned off.

[0026] Furthermore, the second switch module includes: a second unidirectional diode and a second switch tube connected in reverse parallel;

[0027] Forward conduction of the second switch module means that the second switch tube is turned on and the second unidirectional diode is turned off; reverse conduction of the second switch module means that the second switch tube is turned off and the second unidirectional diode is turned on; and turning off of the second switch module means that the second switch tube is turned off and the second unidirectional diode is turned off.

[0028] The present invention also provides a power supply circuit, comprising a rectifier circuit, a bus capacitor and an inverter circuit, and also comprising the above-mentioned switch control circuit.

[0029] The present invention also provides a switch control method, which is applied to the above switch control circuit, and the method comprises:

[0030] The electric energy released by the rectifier circuit and the inverter circuit is stored by the resonance module, and based on the electric energy stored by the resonance module, the voltage drop across the switching device is controlled to be zero before the switching device is controlled to be turned on;

[0031] After the switching device is turned on and before the switching device is turned off, the voltage across the switching device is controlled to remain zero through the inverter circuit until the switching device is controlled to be turned off.

[0032] Furthermore, the electric energy released by the rectifier circuit and the inverter circuit is stored by the resonance module, and based on the electric energy stored by the resonance module, before the switch device is controlled to be turned on, the voltage drop across the switch device is controlled to be zero, including:

[0033] Controlling the first switch module to conduct forward, so that the rectifier circuit outputs an initial voltage to the inverter circuit;

[0034] After the first switch module is forward-conducted, the second switch module is controlled to be forward-conducted, so that the rectifier circuit charges the resonant capacitor and the resonant inductor;

[0035] When the current of the resonant inductor increases to a preset current threshold, controlling the first switch to be turned off so that the buffer capacitor releases electric energy to the resonant capacitor and the resonant inductor;

[0036] After all the electric energy in the buffer capacitor is released and the voltage across the inverter circuit drops to zero, the resonant inductor is controlled to release the electric energy to the resonant capacitor, and the freewheeling diode inside the switch device is turned on, thereby making the voltage across the switch device zero.

[0037] Further, after the resonant inductor finishes releasing electric energy to the resonant capacitor, the method further includes:

[0038] The second switch module is controlled to be reversely conducted, so that the resonant capacitor releases electrical energy to the resonant inductor; wherein, when the second switch module is reversely conducted, the switch device is turned on.

[0039] Further, after the switch device is turned on and before the switch device is turned off, controlling the voltage across the switch device to remain zero until the switch device is controlled to be turned off includes:

[0040] Before the electric energy of the resonant capacitor is completely released to the resonant inductor, the voltage across the inverter circuit is controlled to remain zero; wherein, when the electric energy of the resonant capacitor is completely released to the resonant inductor, the switch device is turned off.

[0041] Furthermore, after controlling the switch device to turn off, the method further includes:

[0042] The unidirectional diode is controlled to be turned on, thereby controlling the resonant inductor to release electric energy to the buffer capacitor, so that the voltage across the inverter circuit increases; wherein the anode of the unidirectional diode is connected between the first end of the second switch module and the positive input terminal of the inverter circuit, and the cathode is connected between the second end of the resonant capacitor and the first end of the resonant inductor.

[0043] Further, after controlling the resonant inductor to release electric energy to the buffer capacitor so that the voltage across the inverter circuit increases, the method further includes:

[0044] After the voltage at both ends of the inverter circuit rises to an initial voltage, the first switch module is controlled to conduct in reverse, so that the resonant inductor releases electric energy to the bus capacitor;

[0045] After the current of the resonant inductor decreases to zero, the first switch module is controlled to be forward-conducted.

[0046] The present invention also provides a computer-readable storage medium on which a computer program is stored, and the program implements the above-mentioned switching method when executed by a processor.

[0047] The technical solution of the present invention is applied. Based on the electric energy obtained from the rectifier circuit and the inverter circuit, the freewheeling diode inside the switch device is controlled to be turned on before the switch device in the inverter circuit is turned on, so that the voltage drop across the switch device is zero, and the electric energy is released to the resonance module through the buffer capacitor inside the inverter capacitor; and the voltage across the switch device is controlled to remain zero after the switch device is turned on and before it is turned off. When the switch device is turned on or off, the voltage across its two ends is zero, realizing zero-voltage soft turn-on and soft turn-off, reducing device loss, and improving the reliability of the inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A topological diagram of an existing power supply circuit;

[0049] Figure 2 is a connection diagram of a switch control circuit and a power supply circuit according to an embodiment of the present invention;

[0050] Figure 3 is a connection diagram of a switch control circuit and a power supply circuit according to another embodiment of the present invention;

[0051] Figure 4 FIG. 4 is a flow chart of a switch control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0054] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0055] It should be understood that, although the terms first, second, etc. may be used to describe the switch modules in the embodiments of the present invention, the switch modules should not be limited to these terms. These terms are only used to distinguish different switch modules. For example, without departing from the scope of the embodiments of the present invention, the first switch module may also be referred to as the second switch module, and similarly, the second switch module may also be referred to as the first switch module.

[0056] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0057] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0058] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings. Example 1

[0059] This embodiment provides a switch control circuit, which is applied to a power supply circuit. Figure 2 FIG. 4 is a connection diagram of a switch control circuit and a power supply circuit according to an embodiment of the present invention. Figure 2As shown, the power supply circuit includes a rectifier circuit 1, a bus capacitor C and an inverter circuit 2. The rectifier circuit 1 is connected to the AC power grid. The rectifier circuit 1 includes three rectifier bridges. Each rectifier bridge includes two rectifier diodes connected in series in the same direction. The output terminals of each phase of the AC power grid are respectively connected between the two rectifier diodes in the corresponding rectifier bridge. The bus capacitor C is arranged between the positive and negative output terminals of the rectifier circuit 1. The inverter circuit 2 is connected in parallel at both ends of the bus capacitor C. In this embodiment, the inverter circuit 2 includes six switching devices Q. The above six switching devices Q are connected in series in pairs in the same direction and then connected in parallel to form three inverter bridges. Each switching device Q includes a switch tube and a freewheeling diode D connected in reverse parallel thereto. The output end of the inverter circuit is connected to the load.

[0060] like Figure 2 As shown, the switch control circuit includes: a resonance module 10, a first end of the resonance module 10 is connected to the first end of the bus capacitor C, a second end of the resonance module 10 is connected to the positive input terminal of the inverter circuit 2, and a third end of the resonance module 10 is connected between the second end of the bus capacitor C and the negative input terminal of the inverter circuit 2; the resonance module 10 is used to store the electric energy released by the rectifier circuit 1 and the inverter circuit 2, and based on the electric energy, before the switch device Q in the inverter circuit 2 is turned on, the freewheeling diode D inside the switch device Q is controlled to be turned on, so that the voltage drop across the switch device Q is zero.

[0061] The buffer capacitor C1 is correspondingly arranged at both ends of each switching device Q in the inverter circuit, and is used to release electric energy to the resonance module 10, and to control the voltage across the switching device Q to remain zero after the switching device Q is turned on and before it is turned off.

[0062] In the figure, Cx is the equivalent capacitance of the parallel circuit composed of the buffer capacitors C1 that are turned on in the inverter circuit 2. It is assumed that the capacitance of the six buffer capacitors C1 is equal, that is, Cs. Because when any upper or lower switch device of each bridge arm of the inverter circuit is turned on, the buffer capacitor C1 in parallel with the switch device will be short-circuited. Therefore, at any time, the equivalent capacitance of the inverter circuit is equal to the capacitance of the three buffer capacitors in parallel. According to the capacitance calculation method of the capacitor parallel circuit, it can be known that Cx = 3Cs.

[0063] The switch control circuit of this embodiment controls the freewheeling diode inside the switch device to conduct before the switch device in the inverter circuit is turned on based on the electric energy obtained from the rectifier circuit and the inverter circuit through the resonance module, so that the voltage drop across the switch device is zero, and releases electric energy to the resonance module through the buffer capacitor inside the inverter capacitor; and controls the voltage across the switch device to remain zero after the switch device is turned on and before it is turned off. When the switch device is turned on or off, the voltage across its two ends is zero, realizing zero-voltage soft conduction and soft shutdown, reducing device loss, and improving the reliability of the inverter. Example 2

[0064] This embodiment provides another switch control circuit. Figure 3 FIG. 1 is a connection diagram of a switch control circuit and a power supply circuit according to another embodiment of the present invention. In order to realize zero voltage soft turn-on and soft turn-off of a switch device, as shown in FIG. Figure 3 As shown, the resonance module 10 comprises: a first switch module 101, a first end of which is connected to a first end of a bus capacitor C, and a second end of which is connected to a positive input terminal of an inverter circuit 2. The first switch module 101 comprises three states, namely, forward conduction, reverse conduction and off. The first switch module 101 is used to: forward conduct before the switch device Q is turned on, and control the rectifier circuit 1 to output an initial voltage U1 to the inverter circuit 2; specifically, as Figure 3 As shown, in order to realize the three states of forward conduction, reverse conduction and shutdown, the first switch module 101 includes: a first unidirectional diode D1 and a first switch tube Q1 connected in reverse parallel; forward conduction of the first switch module 101 means that the first switch tube Q1 is turned on, and the first unidirectional diode D1 is turned off; reverse conduction of the first switch module 101 means that the first switch tube Q1 is turned off, and the first unidirectional diode D1 is turned on; shutdown of the first switch module means that the first switch tube Q1 is turned off, and the first unidirectional diode D1 is turned on.

[0065] The second switch module 102 has a first end connected between the second end of the first switch module 101 and the positive input terminal of the inverter circuit 2, and a second end connected to the first end of the resonant capacitor C2. The second switch module 102 includes three states: forward conduction, reverse conduction and off. The second switch module 102 is used to: forward conduct after the first switch module 101 is forward conducted, and control the rectifier circuit 1 to charge the resonant capacitor C2 and the resonant inductor L. Specifically, Figure 3 As shown, in order to realize the three states of forward conduction, reverse conduction and shutdown, the second switch module 102 includes: a second unidirectional diode D2 and a second switch tube Q2 connected in reverse parallel; the second switch module 102 forward conduction means that the second switch tube Q2 is turned on, and the second unidirectional diode D2 is turned off; the second switch module reverse conduction means that the second switch tube Q2 is turned off, and the second unidirectional diode D2 is turned on; the second switch module shutdown means that the second switch tube Q2 is turned off, and the second unidirectional diode D2 is turned off. When the second switch module 102 is forward conducted, under the energy storage effect of the resonant inductor L, the change rate of the current flowing through the second switch module 102 is limited, so the forward conduction process of the second switch module 102 is zero current soft conduction.

[0066] After the second switch module 102 is forward-conducted, the resonant inductor L is charged, and the current passing through the resonant inductor L gradually increases. The first switch module 101 is also used to shut down when the current of the resonant inductor L increases to a preset current threshold. Due to the clamping effect of the buffer capacitor C1, the voltage across the inverter circuit 2 cannot suddenly change, which reduces the rate of change of the voltage across the first switch tube Q1, and the first switch tube Q1 achieves zero-voltage soft shutdown.

[0067] The second end of the resonant capacitor C2 is connected to the first end of the resonant inductor L, and is used to release electric energy L to the resonant inductor, or to store the electric energy released by the resonant inductor L; the second end of the resonant inductor L is connected between the second end of the bus capacitor C and the negative input terminal of the inverter circuit 2.

[0068] The buffer capacitor C1 is specifically used to release electric energy to the resonant capacitor C2 and the resonant inductor L when the first switch module 101 is turned off and the second switch module 102 is forward-conducting.

[0069] The resonant inductor L is used to release the electric energy to the resonant capacitor C2 after the electric energy of the buffer capacitor is completely released to make the voltage drop across the inverter circuit zero, and at the same time turn on the freewheeling diode D inside the switching device Q, thereby making the voltage drop across the switching device Q zero.

[0070] The second switch module 102 is also used to reverse conduct after the resonant inductor L releases electric energy to the resonant capacitor C2, that is, after the electric energy of the resonant inductor L is completely released to the resonant capacitor C2, so that the resonant capacitor C2 releases electric energy to the resonant inductor L; wherein, after the second switch module 102 is reversely conducted, the switch device Q is controlled to be turned on, because before the switch device Q is turned on, the freewheeling diode D inside it is turned on, so that the voltage across the switch device Q has been reduced to zero, so zero voltage soft conduction is achieved. At this time, the current flows from the first end of the resonant capacitor C2 through the second switch module, and then through the turned-on switch device Q, flows into the second end and the first end of the resonant inductor, and then flows back to the second end of the resonant capacitor C2. Because before the second switch tube Q2 is turned off, the resonant inductor L has finished releasing electric energy to the resonant capacitor C2, and the current value flowing through the second switch tube Q2 has dropped to zero, so the turn-off process of the second switch tube Q2 is zero current soft turn-off.

[0071] In order to realize the zero-voltage soft shutdown of the switching device, the buffer capacitor C1 is specifically used to: keep the voltage across itself at zero before the electric energy of the resonant capacitor C2 is completely released; wherein, when the electric energy of the resonant capacitor C2 is completely released to the resonant inductor L, the switching device Q is controlled to be turned off. Due to the clamping effect of the buffer capacitor, the voltage across the switching device is zero at this time, realizing zero-voltage soft shutdown.

[0072] In order to control the voltage at both ends of the inverter circuit to return to the initial voltage U1 after the switch device is turned off, the above-mentioned resonant module 101 also includes: a unidirectional diode D3, whose anode is connected between the first end of the second switch module 102 and the positive input terminal of the inverter circuit 1, and whose cathode is connected between the second end of the resonant capacitor C2 and the first end of the resonant inductor L; the above-mentioned unidirectional diode D1 is used to: turn on after the switch device Q is turned off, control the resonant inductor L to release electric energy to the inverter circuit 2, so that the voltage at both ends of the inverter circuit increases. Specifically, the current flows from the first end of the resonant inductor L, through the unidirectional diode D1 to the buffer capacitor C1 in the inverter circuit 2, and then returns to the second end of the resonant inductor L, so that the voltage at both ends of the inverter circuit 2 increases.

[0073] In a specific implementation, after the voltage across the inverter circuit 2 rises to the initial voltage U1, it will not be able to continue to rise. At this time, there may still be a certain amount of electric energy in the resonant inductor L. In order to release this part of the electric energy, the first switch module 101 is also used to: reverse conduct after the voltage across the inverter circuit rises to the initial voltage U1, so that the resonant inductor L releases electric energy to the bus capacitor C; and forward conduct after the current of the resonant inductor decreases to zero, completing the entire switch control operation.

[0074] The working principle of the present invention is described in detail below in conjunction with a specific embodiment. The specific principles of the present invention include:

[0075] Step 1, at time t0, control the first switch tube Q1 to be turned on, the rectifier circuit 1 directly supplies power to the inverter circuit 2, the inverter circuit 2 works in a stable state, the voltage across the resonant capacitor C2 is 0, the resonant inductor current is 0, and the voltage across the inverter circuit 2 is the initial voltage U1; at the same time, the inverter circuit 2 supplies power to the load.

[0076] Step 2, in the time period (t0, t1], after the first switch tube Q1 is triggered, the second switch tube Q2 is triggered to turn on. Under the energy storage effect of the resonant inductor L, the change rate of the current flowing through the second switch tube Q2 is limited. Therefore, the conduction process of the second switch tube Q2 is zero current soft conduction. After the second switch tube Q2 is turned on, the resonant inductor L and the resonant capacitor C2 are charged at the same time; the current flowing through them both increases from zero. At the moment t1, the current of the resonant inductor L increases to be equal to the preset current threshold. At this time, the first switch tube Q1 is controlled to be turned off, and step 2 ends. At the moment when the first switch tube Q1 is turned off, due to the clamping effect of the buffer capacitor C1 in the capacitor inverter circuit 2, the voltage across the first switch tube Q1 cannot suddenly change, and the change rate of the voltage across the first switch tube Q1 is reduced, so the first switch tube Q1 achieves zero voltage soft shutdown.

[0077] Step 3, in the time period (t1, t2), the resonant inductor L, the resonant capacitor C2 and the inverter circuit 2 enter the resonant state, and the inverter circuit 2 charges the resonant inductor L and the resonant capacitor C2. The current of the resonant inductor L gradually increases based on the above-mentioned preset current threshold, the voltage across the resonant capacitor C2 also begins to gradually increase, and the voltage across the inverter circuit 2 gradually decreases from the initial value U1, the first resonance process is completed, and step 3 ends.

[0078] Step 4, in the time period [t2, t3], at time t2, when the voltage across the inverter circuit decreases to zero, the current of the resonant inductor L increases to the maximum value, and the flyback diode D connected in parallel across the switch device in the inverter circuit begins to conduct, and the inverter circuit 2 continues current through the flyback diode D. The second switch tube Q2, the resonant capacitor C2, the resonant inductor L and the flyback diode D form a loop, the resonant inductor L charges the resonant capacitor C2, and the inductor current value gradually decreases. When the inductor current value decreases to zero at t3, step 4 ends.

[0079] Step 5, in the time period (t3, t4], after the moment t3, the second switch tube Q2 is turned off, and the second unidirectional diode D2 is controlled to be turned on. Because the current value flowing through the second switch tube Q2 has dropped to zero before the second switch tube Q2 is turned off, the turn-off process of the second switch tube Q2 is a zero-current soft turn-off. At the same time, the IGBT switch device is turned on, because the terminal voltage of the IGBT switch device has been reduced to zero before the IGBT switch device is turned on, so zero-voltage soft turn-on is achieved. After the IGBT switch device is turned on, the resonant inductor L and the resonant capacitor C2 enter the resonant state, the resonant capacitor C2 is discharged, the resonant inductor L is charged, and the resonant current starts to increase from zero. At the moment t4, when the resonant current increases to the maximum value, this resonance process is completed, and step 5 ends.

[0080] Step 6, in the time period (t4, t5], at time t4, the voltage across the resonant capacitor C2 drops to zero, and the IGBT switch device is turned off. Because the buffer capacitor C1 reduces the rising rate of the voltage at the terminal of the IGBT switch device, the IGBT switch device achieves zero voltage soft shutdown. After the IGBT switch device is turned off, the unidirectional diode D3 is triggered to conduct, the buffer capacitor C1 and the resonant inductor L enter the resonant state, and the resonant inductor L charges the buffer capacitor C1, so that the voltage across the inverter circuit 2 gradually increases, and the current of the resonant inductor L decreases. When the resonant inductor L decreases to zero at time t5, the voltage across the inverter circuit 2 increases to the initial voltage U1, and step 6 ends.

[0081] Step 7: In the time period (t5, t6), after time t5, the voltage across the inverter circuit increases to the initial voltage U1, and the voltage across the inverter circuit is clamped at the initial voltage U1. The resonant inductor no longer charges the buffer capacitor C1, but starts to charge the bus capacitor. The current starts to flow through the first unidirectional diode D1, and the current of the resonant inductor L starts to decrease linearly. At time t6, when the current of the resonant inductor L is zero, the unidirectional diode D3 enters the cut-off state, and step 7 ends.

[0082] Step 8, in the (t6, t7] time period, after time t6, the unidirectional diode D3 enters the cut-off state, and at this time, the first switch tube Q1 is turned on, and the first switch tube Q1 is soft-turned on with zero voltage. After the first switch tube Q1 is turned on, at time t7, the process returns to step 1 to perform the next working cycle. Example 3

[0083] This embodiment provides a power supply circuit, including a rectifier circuit, a bus capacitor and an inverter circuit, and also includes the switch control circuit in the above embodiment, which is used to control the switch device to softly turn on and off at zero voltage to improve circuit reliability. Example 4

[0084] This embodiment provides a switch control method, which is applied to the switch control circuit in the above embodiment. Figure 4 is a flow chart of a switch control method according to an embodiment of the present invention. Figure 4 As shown, the method includes:

[0085] S101, storing electric energy released by a rectifier circuit and an inverter circuit through a resonance module, and based on the electric energy stored in the resonance module, controlling the voltage drop across the switching device to zero before controlling the switching device to be turned on.

[0086] S102, controlling the voltage across the switching device to remain zero after the switching device is turned on and before the switching device is turned off through the inverter circuit until the switching device is turned off.

[0087] The switch control method of this embodiment controls the freewheeling diode inside the switch device to conduct before the switch device in the inverter circuit is turned on based on the electric energy obtained by the rectifier circuit and the inverter circuit through the resonance module, so that the voltage drop across the switch device is zero, and the electric energy is released to the resonance module through the buffer capacitor inside the inverter capacitor; and, after the switch device is turned on and before it is turned off, the voltage across the switch device is controlled to remain zero. When the switch device is turned on or off, the voltage across its two ends is zero, realizing zero-voltage soft conduction and soft shutdown, reducing device loss, and improving the reliability of the inverter.

[0088] In order to achieve zero-voltage soft turn-on and soft turn-off of the switching device, the electric energy released by the rectifier circuit and the inverter circuit is stored by the resonance module. Based on the electric energy stored in the resonance module, before controlling the switching device to turn on, the voltage drop across the switching device is controlled to be zero, specifically including: controlling the first switch module to be forward-conducted so that the rectifier circuit outputs an initial voltage to the inverter circuit; controlling the second switch module to be forward-conducted after the first switch module is forward-conducted so that the rectifier circuit charges the resonant capacitor and the resonant inductor; when the current of the resonant inductor increases to a preset current threshold, controlling the first switch to be turned off so that the buffer capacitor releases electric energy to the resonant capacitor and the resonant inductor; after all the electric energy of the buffer capacitor is released and the voltage drop across the inverter circuit is zero, controlling the resonant inductor to release electric energy to the resonant capacitor, and at the same time turning on the freewheeling diode inside the switching device, thereby making the voltage across the switching device zero. After the resonant inductor finishes releasing electric energy to the resonant capacitor, the method further includes: controlling the second switch module to conduct in reverse, so that the resonant capacitor releases electric energy to the resonant inductor; wherein, when the second switch module conducts in reverse, the switch device is turned on, because before the switch device is turned on, the freewheeling diode inside it is turned on, so that the voltage across the switch device has been reduced to zero, thereby achieving zero voltage soft turn-on.

[0089] The above steps realize zero voltage soft turn-on. To further realize zero voltage soft turn-off, after the switch device is turned on and before the switch device is turned off, the voltage across the switch device is controlled to remain zero until the switch device is controlled to be turned off, including: before the electric energy of the resonant capacitor is fully released to the resonant inductor, the voltage across the inverter circuit is controlled to remain zero; wherein, when the electric energy of the resonant capacitor is fully released to the resonant inductor, the switch device is turned off. Due to the clamping effect of the buffer capacitor, the voltage across the switch device is zero at this time, realizing zero voltage soft turn-off.

[0090] In order to control the voltage across the inverter circuit to return to the initial voltage after the switch device is turned off, the method further includes: controlling the unidirectional diode to conduct, thereby controlling the resonant inductor to release electrical energy to the buffer capacitor, thereby increasing the voltage across the inverter circuit; wherein the anode of the unidirectional diode is connected between the first end of the second switch module and the positive input terminal of the inverter circuit, and the cathode of the unidirectional diode is connected between the second end of the resonant capacitor and the first end of the resonant inductor.

[0091] After controlling the unidirectional diode to conduct, and then controlling the resonant inductor to release electric energy to the buffer capacitor, so that the voltage at both ends of the inverter circuit increases, it also includes: after the voltage at both ends of the inverter circuit increases to the initial voltage, it will no longer continue to increase. At this time, there may still be a certain amount of electric energy in the resonant inductor L. In order to release this part of the electric energy, the first switch module is controlled to be reversely conducted so that the resonant inductor releases electric energy to the bus capacitor; after the current of the resonant inductor is reduced to zero, the first switch module is controlled to be forwardly conducted to complete the entire switch control operation. Example 5

[0092] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the switch control method in the above embodiment is implemented.

[0093] The circuit embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0094] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A switch control circuit, applied to a power supply circuit, wherein the power supply circuit comprises a rectifier circuit, a bus capacitor and an inverter circuit, characterized in that: The switch control circuit comprises: A resonance module, wherein the first end thereof is connected to the first end of the bus capacitor, the second end thereof is connected to the positive input terminal of the inverter circuit, and the third end thereof is connected between the second end of the bus capacitor and the negative input terminal of the inverter circuit; the resonance module is used to store the electric energy released by the rectifier circuit and the buffer capacitor, and before the switch device in the inverter circuit is turned on based on the electric energy, the freewheeling diode inside the switch device is controlled to be turned on, so that the voltage drop across the switch device is zero; the resonance module comprises: a first switch module, wherein the first end thereof is connected to the first end of the bus capacitor, and the second end thereof is connected to the positive input terminal of the inverter circuit; a second switch module, wherein the first end thereof is connected between the second end of the first switch module and the positive input terminal of the inverter circuit, and the second end thereof is connected to the first end of the resonance capacitor; the resonance capacitor; the second end thereof is connected to the first end of the resonance inductor, and is used to release electric energy to the resonance inductor, or to store the electric energy released by the resonance inductor; the second end of the resonance inductor is connected between the second end of the bus capacitor and the negative input terminal of the inverter circuit; The buffer capacitor is correspondingly arranged at both ends of each switching device in the inverter circuit, and is used to release electric energy to the resonance module, and control the voltage at both ends of the switching device to remain zero after the switching device is turned on and before the switching device is turned off.

2. The switch control circuit according to claim 1, characterized in that: The first switch module is used for forward conduction before the switch device is turned on, and controls the rectifier circuit to output an initial voltage to the inverter circuit; The second switch module is used to conduct forward after the first switch module is conducted forward, and control the rectifier circuit to charge the resonant capacitor and the resonant inductor; The first switch module is further configured to switch off when the current of the resonant inductor increases to a preset current threshold after the second switch module is forwardly conducted; The buffer capacitor is specifically used to release electric energy to the resonant capacitor and the resonant inductor when the first switch module is turned off and the second switch module is forwardly conducted; The resonant inductor is used to release the electric energy to the resonant capacitor after all the electric energy in the buffer capacitor is released and the voltage drop across the inverter circuit is zero, and at the same time, the freewheeling diode inside the switch device is turned on, thereby making the voltage drop across the switch device zero; The second switch module is further used for reverse conduction after the resonant inductor finishes releasing electric energy to the resonant capacitor, so that the resonant capacitor releases electric energy to the resonant inductor; wherein, after the second switch module is reversely conducted, the switch device is turned on.

3. The switch control circuit according to claim 1, characterized in that: The inverter circuit is specifically used to keep the voltage across itself at zero before all the electric energy of the resonant capacitor is released to the resonant inductor; wherein, when all the electric energy of the resonant capacitor is released to the resonant inductor, the switch device is controlled to be turned off.

4. The switch control circuit according to claim 3, characterized in that: The resonance module further includes: a unidirectional diode, wherein the anode of the diode is connected between the first end of the second switch module and the positive input terminal of the inverter circuit, and the cathode of the diode is connected between the second end of the resonant capacitor and the first end of the resonant inductor; The unidirectional diode is used to be turned on after the switch device is turned off, and to control the resonant inductor to release electric energy to the buffer capacitor, so that the voltage across the inverter circuit increases.

5. The switch control circuit according to claim 4, characterized in that: The first switch module is further used for reverse conduction after the voltage at both ends of the inverter circuit rises to an initial voltage, so that the resonant inductor releases electric energy to the bus capacitor; and forward conduction after the current of the resonant inductor decreases to zero.

6. The switch control circuit according to any one of claims 2 to 5, characterized in that: The first switch module comprises: a first unidirectional diode and a first switch tube connected in reverse parallel; Forward conduction of the first switch module means that the first switch tube is turned on and the first unidirectional diode is turned off; reverse conduction of the first switch module means that the first switch tube is turned off and the first unidirectional diode is turned on; and shutdown of the first switch module means that the first switch tube is turned off and the first unidirectional diode is turned off.

7. The switch control circuit according to any one of claims 2 to 5, characterized in that: The second switch module includes: a second unidirectional diode and a second switch tube connected in reverse parallel; Forward conduction of the second switch module means that the second switch tube is turned on and the second unidirectional diode is turned off; reverse conduction of the second switch module means that the second switch tube is turned off and the second unidirectional diode is turned on; and turning off of the second switch module means that the second switch tube is turned off and the second unidirectional diode is turned off.

8. A power supply circuit, comprising a rectifier circuit, a bus capacitor and an inverter circuit, characterized in that: It also includes the switch control circuit according to any one of claims 1 to 7.

9. A switch control method, applied to the switch control circuit according to any one of claims 1 to 7, characterized in that: The method comprises: The electrical energy released by the rectifier circuit and the inverter circuit is stored by the resonance module, and based on the electrical energy stored by the resonance module, the voltage drop across the switching device is controlled to be zero before the switching device is controlled to be turned on; After the switching device is turned on and before the switching device is turned off, the voltage across the switching device is controlled to remain zero through the inverter circuit until the switching device is controlled to be turned off.

10. The switch control method according to claim 9, characterized in that: The electric energy released by the rectifier circuit and the inverter circuit is stored by the resonance module, and based on the electric energy stored by the resonance module, before the switch device is controlled to be turned on, the voltage drop across the switch device is controlled to be zero, including: Controlling the first switch module to conduct forward, so that the rectifier circuit outputs an initial voltage to the inverter circuit; After the first switch module is forward-conducted, the second switch module is controlled to be forward-conducted, so that the rectifier circuit charges the resonant capacitor and the resonant inductor; When the current of the resonant inductor increases to a preset current threshold, controlling the first switch to be turned off so that the buffer capacitor releases electric energy to the resonant capacitor and the resonant inductor; After all the electric energy in the buffer capacitor is released and the voltage across the inverter circuit drops to zero, the resonant inductor is controlled to release the electric energy to the resonant capacitor, and the freewheeling diode inside the switch device is turned on, thereby making the voltage across the switch device zero.

11. The switch control method according to claim 10, characterized in that: After the resonant inductor finishes releasing electrical energy to the resonant capacitor, the method further includes: The second switch module is controlled to be reversely conducted, so that the resonant capacitor releases electrical energy to the resonant inductor; wherein, when the second switch module is reversely conducted, the switch device is turned on.

12. The switch control method according to claim 11, characterized in that: After the switch device is turned on and before the switch device is turned off, controlling the voltage across the switch device to remain zero until the switch device is controlled to be turned off, comprising: Before the electric energy of the resonant capacitor is completely released to the resonant inductor, the voltage across the inverter circuit is controlled to remain zero; wherein, when the electric energy of the resonant capacitor is completely released to the resonant inductor, the switch device is turned off.

13. The switch control method according to claim 12, characterized in that: After controlling the switch device to turn off, the method further includes: The unidirectional diode is controlled to be turned on, thereby controlling the resonant inductor to release electric energy to the buffer capacitor, so that the voltage across the inverter circuit increases; wherein the anode of the unidirectional diode is connected between the first end of the second switch module and the positive input terminal of the inverter circuit, and the cathode is connected between the second end of the resonant capacitor and the first end of the resonant inductor.

14. The switch control method according to claim 13, characterized in that: After controlling the unidirectional diode to conduct, thereby controlling the resonant inductor to release electric energy to the buffer capacitor so that the voltage at both ends of the inverter circuit increases, the method further includes: After the voltage at both ends of the inverter circuit rises to an initial voltage, the first switch module is controlled to conduct in reverse, so that the resonant inductor releases electric energy to the bus capacitor; After the current of the resonant inductor decreases to zero, the first switch module is controlled to be forward-conducted.

15. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 9 to 14 is implemented.

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