A bridge arm circuit with zero-voltage turn-off and zero-current turn-on and a control method thereof

Abstract

The present invention discloses a leg circuit and a control method with zero-voltage turn-off and zero-current turn-on, belonging to the field of soft-switching circuits. In the leg circuit of the present invention, an inductor is respectively led out from the midpoints of four legs. The midpoint of the first leg is connected to the midpoint of the third leg through an inductor, and the midpoint of the second leg is connected to the midpoint of the fourth leg through an inductor. Moreover, a capacitor is provided between the midpoint of the first leg and the midpoint of the second leg, and between the midpoint of the third leg and the midpoint of the fourth leg. By delaying the current rising rate through the inductor, combining the principle of capacitor charge and discharge, and cooperating with the on-off timing control of each switching device, zero-current turn-on and zero-voltage turn-off of each switching device are realized. It can be applied to all existing leg circuit application scenarios, and soft-switching processing (zero-current turn-on and zero-voltage turn-off) can be realized without separately designing an LC resonance circuit, greatly reducing the switching loss and having a wide application range.

Description

Technical Field

[0001] The present invention relates to the field of soft-switching circuits, and particularly to a leg circuit and a control method for zero-voltage turn-off and zero-current turn-on. Background Art

[0002] Soft-switching circuits are widely used in fields such as switching power supplies, motor drives, and power regulation, aiming to reduce the losses and electromagnetic interference (EMI) generated when switching devices. As Figure 1 shown, in a traditional hard-switching circuit, during the switching process, both the voltage and current are non-zero, there is an overlap, resulting in switching losses; and the voltage and current change rapidly, and the waveforms show obvious overshoots, leading to switching noise. As Figure 2 shown, the soft-switching circuit adds resonant elements on the basis of the original circuit, introduces resonance before and after the switching process, eliminates the overlap of voltage and current, and thus reduces the switching losses and switching noise.

[0003] Existing soft-switching circuits usually use an LC resonant circuit to generate resonance across the switching device, so that the switching device switches when the voltage or current is close to zero, reducing the switching losses. Existing soft-switching circuits are usually designed and controlled separately for a specific application circuit, that is, a resonant circuit needs to be designed separately for the original topology circuit, and cannot adapt to all scenarios and does not have universality. On this basis, how to design a soft-switching circuit that does not rely on an LC resonant circuit and can achieve zero-voltage turn-off and zero-current turn-on is a technical problem that urgently needs to be solved at present. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of the existing technology and provide a leg circuit and a control method for zero-voltage turn-off and zero-current turn-on.

[0005] The object of the present invention is achieved by the following technical solutions: A bridge arm circuit with zero-voltage turn-off and zero-current turn-on, which is located between the power supply end and the load end, includes cascaded first bridge arm, second bridge arm, third bridge arm and fourth bridge arm. The upper arm and the lower arm of the first bridge arm are respectively provided with a first switching device and a second switching device. The upper arm and the lower arm of the second bridge arm are respectively provided with a third switching device and a fourth switching device. The upper arm and the lower arm of the third bridge arm are respectively provided with a fifth switching device and a sixth switching device. The upper arm and the lower arm of the fourth bridge arm are respectively provided with a seventh switching device and an eighth switching device. The eight switching devices are connected to the control module. The midpoint of the first bridge arm is connected to a first inductor, the midpoint of the second bridge arm is connected to a second inductor. The first inductor is connected to the second inductor, and a first capacitor is provided between the midpoint of the first bridge arm and the midpoint of the second bridge arm. The midpoint of the third bridge arm is connected to a third inductor, the midpoint of the fourth bridge arm is connected to a fourth inductor. The third inductor is connected to the fourth inductor, and a second capacitor is provided between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm. A fifth inductor is provided between the midpoint of the second bridge arm and the midpoint of the fourth bridge arm, and a sixth inductor is provided between the midpoint of the first bridge arm and the midpoint of the third bridge arm. The common connection point of the first inductor and the second inductor, and the common connection point of the third inductor and the fourth inductor are connected to an energy transfer inductor, and the energy transfer inductor is connected to the power supply end.

[0006] In one example, the switching device is a transistor, which can be any one or more of MOSFET, IGBT, BJT, and triode.

[0007] In one example, all the switching devices in the bridge arm circuit are IGBTs. The emitter of the first switching device is connected to the collector of the second switching device. The emitter of the third switching device is connected to the collector of the fourth switching device. The emitter of the fifth switching device is connected to the collector of the sixth switching device. The emitter of the seventh switching device is connected to the collector of the eighth switching device. The collector of the first switching device is connected to the collector of the third switching device. The collector of the third switching device is connected to the collector of the fifth switching device. The collector of the fifth switching device is connected to the collector of the seventh switching device. The emitter of the second switching device is connected to the emitter of the fourth switching device. The emitter of the fourth switching device is connected to the emitter of the sixth switching device. The emitter of the sixth switching device is connected to the emitter of the eighth switching device. The gates of the eight switching devices are all connected to the control module.

[0008] In one example, the bridge arm circuit includes at least two bridge arm circuits formed by any one or more of the above examples. The single bridge arm circuits can be cascaded, paralleled or connected in a hybrid manner. Each bridge arm circuit realizes single bridge arm control in the switching power supply topology as an independent module.

[0009] It should be further noted that the technical features corresponding to the above examples can be combined with each other or replaced to form a new technical solution.

[0010] The present invention further includes a control method for a bridge arm circuit with zero-voltage turn-off and zero-current turn-on. This method is used to control the bridge arm circuit formed by any one of the above examples or a combination of multiple examples. The execution subject of the method is a control module, and it includes the following steps:

[0011] Control the switching timings of the switching devices in each bridge arm to charge and discharge the first capacitor and the second capacitor. Through the charge and discharge process of the first capacitor and the second capacitor, turn off the switching devices on the zero-voltage side of the first capacitor and the second capacitor to achieve zero-voltage turn-off;

[0012] Control the switching timings of the switching devices in each bridge arm to adjust the current changes in the first inductor, the second inductor, the third inductor, the fourth inductor, the fifth inductor, and the sixth inductor, delay the rising speed of the current in the corresponding inductor, and turn on the switching devices in zero current to achieve zero-current turn-on.

[0013] In one example, the zero-voltage turn-off includes:

[0014] In the positive half-cycle of the AC power supply:

[0015] When turning off the third switching device, the second switching device, the fifth switching device, and the eighth switching device, and turning on the first switching device, the fourth switching device, the seventh switching device, and the sixth switching device, the voltages at the midpoints of the second bridge arm and the third bridge arm are zero. Turn off the fourth switching device and the sixth switching device, and the voltages at one end of the first capacitor close to the midpoint of the second bridge arm and one end of the second capacitor close to the midpoint of the third bridge arm rise, achieving zero-voltage turn-off of the fourth switching device and the sixth switching device;

[0016] When turning off the first switching device, the fourth switching device, the seventh switching device, and the sixth switching device, and turning on the third switching device, the second switching device, the fifth switching device, and the eighth switching device, the voltages at the midpoints of the first bridge arm and the fourth bridge arm are zero. Turn off the second switching device and the eighth switching device, and the voltages at one end of the first capacitor close to the midpoint of the first bridge arm and one end of the second capacitor close to the midpoint of the fourth bridge arm rise, achieving zero-voltage turn-off of the second switching device and the eighth switching device;

[0017] In the negative half-cycle of the AC power supply:

[0018] When the first switch device, the fourth switch device, the seventh switch device, and the sixth switch device are turned off and the second switch device, the third switch device, the eighth switch device, and the fifth switch device are turned on, the voltages at the midpoints of the second bridge arm and the third bridge arm are zero. By turning off the third switch device and the fifth switch device, zero-voltage turn-off of the third switch device and the fifth switch device is achieved, and the voltages at one end of the first capacitor close to the midpoint of the second bridge arm and one end of the second capacitor close to the midpoint of the third bridge arm increase.

[0019] When the second switch device, the third switch device, the fifth switch device, and the eighth switch device are turned off and the first switch device, the fourth switch device, the seventh switch device, and the sixth switch device are turned on, the voltages at the midpoints of the first bridge arm and the fourth bridge arm are zero. By turning off the first switch device and the seventh switch device, zero-voltage turn-off of the first switch device and the seventh switch device is achieved, and the voltages at one end of the first capacitor close to the midpoint of the first bridge arm and one end of the second capacitor close to the midpoint of the fourth bridge arm increase.

[0020] Zero-current turn-on includes:

[0021] During the positive half-cycle of the AC power supply, when the first switch device, the third switch device, the fifth switch device, and the seventh switch device are initially in the off state:

[0022] When the second switch device and the sixth switch device are turned off and the fourth switch device and the eighth switch device are turned on, the currents in the first inductor and the fourth inductor are zero. By turning off the fourth switch device and the eighth switch device, the currents in the second inductor and the third inductor flow through the diodes on the third switch device and the seventh switch device. By turning on the first switch device and the fifth switch device, zero-current turn-on of the first switch device and the fifth switch device is achieved.

[0023] When the fourth switch device and the eighth switch device are turned off and the second switch device and the sixth switch device are turned on, the currents in the second inductor and the third inductor are zero. By turning off the second switch device and the sixth switch device, the currents in the first inductor and the fourth inductor flow through the diodes on the first switch device and the fifth switch device. By turning on the third switch device and the seventh switch device, zero-current turn-on of the third switch device and the seventh switch device is achieved.

[0024] During the negative half-cycle of the AC power supply, when the second switch device, the fourth switch device, the sixth switch device, and the eighth switch device are initially in the off state:

[0025] When the first switch device and the fifth switch device are turned off, and the third switch device and the seventh switch device are turned on, the currents in the second inductor and the third inductor are zero. Turn off the third switch device and the seventh switch device. The currents in the first inductor and the fourth inductor flow through the diodes on the fourth switch device and the eighth switch device. Turn on the second switch device and the sixth switch device to achieve zero-current turn-on of the second switch device and the sixth switch device. The current flowing through the fourth switch device via the first inductor is zero, and the current flowing through the eighth switch device via the fourth inductor is zero.

[0026] When the third switch device and the seventh switch device are turned off, and the first switch device and the fifth switch device are turned on, the current flowing through the fourth switch device via the first inductor is zero and the current flowing through the eighth switch device via the fourth inductor is zero. Turn off the third switch device and the seventh switch device. The currents in the second inductor and the third inductor flow through the second switch device and the sixth switch device. Turn on the fourth switch device and the eighth switch device to achieve zero-current turn-on of the fourth switch device and the eighth switch.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] In the present invention, inductors are led out from the midpoints of four bridge arms, inductors and capacitors are designed between the bridge arms. By using the inductor to delay the current rising rate, combined with the principle of capacitor charge and discharge, and cooperating with the on-off timing control of each switch device, zero-current turn-on and zero-voltage turn-off of each switch device are achieved. It can be applied to all existing bridge arm circuit application scenarios, and soft-switching processing (zero-current turn-on and zero-voltage turn-off) can be realized without separately designing an LC resonant circuit, greatly reducing the switching loss and having a wide application range. Description of the Drawings

[0029] The following further describes the specific embodiments of the present invention in detail with reference to the drawings. The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The same reference numerals are used to represent the same or similar parts in these drawings. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application.

[0030] Figure 1 It is a voltage-current curve diagram during the switching process of an existing hard-switching circuit;

[0031] Figure 2 It is a voltage-current curve diagram during the switching process of a soft-switching circuit with added resonant elements;

[0032] Figure 3 It is a schematic diagram of a bridge arm circuit for zero-voltage turn-off and zero-current turn-on provided by an example of the present invention. Detailed Description of the Invention

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. In addition, the use of ordinal numbers (for example, "first and second", "first to fourth", etc.) is to distinguish objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0035] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0036] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] In an example, a bridge arm circuit with zero-voltage turn-off and zero-current turn-on is located between a power supply terminal and a load terminal. The bridge arm circuit includes cascaded first, second, third, and fourth bridge arms. The fourth bridge arm is connected to the load terminal. Optionally, the fourth bridge arm is connected to the load terminal via a voltage transformation processing circuit. For example, the second bridge arm is connected to the load terminal via a boost circuit. The upper and lower arms of the first bridge arm are respectively provided with a first switching device Q1 and a second switching device Q2. The upper and lower arms of the second bridge arm are respectively provided with a third switching device Q3 and a fourth switching device Q4. The upper and lower arms of the third bridge arm are respectively provided with a fifth switching device Q5 and a sixth switching device Q6. The upper and lower arms of the fourth bridge arm are respectively provided with a seventh switching device Q7 and an eighth switching device Q8. Q1 - Q8 are connected to a control module. The switching device is a transistor, such as any one or more of MOSFET, IGBT, BJT, triode, etc. A diode can be arranged between the source and drain of the transistor or between the emitter and collector of the transistor. Of course, if a diode is already integrated between the emitter and collector of the transistor itself, a new diode does not need to be integrated additionally.

[0038] Optionally, all the switching devices in the bridge arm circuit are IGBTs, and a diode is integrated between the emitter and collector of the IGBT. The anode of the diode is connected to the emitter, and the cathode of the diode is connected to the collector. Specifically, as Figure 3 shown, the emitter of Q1 is connected to the collector of Q2, the emitter of Q3 is connected to the collector of Q4, the emitter of Q5 is connected to the collector of Q6, and the emitter of Q7 is connected to the collector of Q8; the collector of Q1 is connected to the collector of Q3, the collector of Q3 is connected to the collector of Q5, and the collector of Q5 is connected to the collector of Q7; the emitter of Q2 is connected to the emitter of Q4, the emitter of Q4 is connected to the emitter of Q6, the emitter of Q6 is connected to the emitter of Q8, and the gates of Q1 - Q8 are all connected to the control module (not shown in the figure).

[0039] Further, the midpoint of the first bridge arm is connected to the first inductor L1, the midpoint of the second bridge arm is connected to the second inductor L2, the first inductor L1 is connected to the second inductor L2, and a first capacitor C1 is provided between the midpoint of the first bridge arm and the midpoint of the second bridge arm; the midpoint of the third bridge arm is connected to the third inductor L3, the midpoint of the fourth bridge arm is connected to the fourth inductor L4, the third inductor L3 is connected to the fourth inductor L4, and a second capacitor C2 is provided between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm. At this time, the connection point of the first capacitor C1 and the midpoint of the first bridge arm is defined as B1, the connection point of the first capacitor C1 and the midpoint of the second bridge arm is defined as B2, the end of the first capacitor C1 close to B1 is defined as the 1 end of the first capacitor C1, and the end of the first capacitor C1 close to B2 is defined as the 2 end of the first capacitor C1; the connection point of the second capacitor C2 and the midpoint of the third bridge arm is defined as B3, the connection point of the second capacitor C1 and the midpoint of the fourth bridge arm is defined as B4, the end of the second capacitor C2 close to B1 is defined as the 1 end of the second capacitor C2, and the end of the second capacitor close to B2 is defined as the 2 end of the second capacitor C2.

[0040] Further, a fifth inductor L5 is provided between the midpoint of the second bridge arm and the midpoint of the fourth bridge arm, and a sixth inductor L6 is provided between the midpoint of the first bridge arm and the midpoint of the third bridge arm; the common connection point of the first inductor L1 and the second inductor L2, and the common connection point of the third inductor L3 and the fourth inductor L4 are connected to the energy transfer inductor L, and the energy transfer inductor is connected to the positive pole of the power supply.

[0041] For zero-voltage turn-off, by charging and discharging the capacitors C1 and C2, the switching devices on the zero-voltage sides of the capacitors C1 and C2 are turned off, thereby achieving zero-voltage turn-off. The working principle of the bridge arm circuit of the present invention is as follows:

[0042] In the positive half-cycle of the AC power supply, when Q3, Q2, Q5, Q8 are turned off and Q1, Q4, Q7, Q6 are turned on, the voltages at B1 and B4 are Vdc (the DC voltage obtained after processing by the bridge arm circuit), and the voltages at B2 and B3 are 0. At this time, when Q4 and Q6 are turned off, the 2 ends of the capacitor C1 and the 1 end of the capacitor C2 will slowly rise to Vdc, and Q4 and Q6 are zero-voltage turned off. Similarly, when Q1, Q4, Q7, Q6 are turned off and Q3, Q2, Q5, Q8 are turned on, the voltages at B2 and B3 are Vdc, and the voltages at B1 and B4 are 0. At this time, when Q2 and Q8 are turned off, the 1 end of the capacitor C1 and the 2 end of the capacitor C2 will slowly rise to Vdc, and Q2 and Q8 are zero-voltage turned off.

[0043] During the negative half - cycle of the AC power supply, when Q1, Q4, Q7, Q6 are turned off and Q2, Q3, Q8, Q5 are turned on, the voltages at B2 and B3 are zero. Turn off Q3 and Q5, and capacitors C1 and C2 start to charge, achieving zero - voltage turn - off of Q3 and Q5, and the voltages at the 2 - terminal of capacitor C1 and the 1 - terminal of capacitor C2 rise. When Q2, Q3, Q5, Q8 are turned off and Q1, Q4, Q7, Q6 are turned on, the voltages at B1 and B4 are zero. Turn off Q1 and Q7, achieving zero - voltage turn - off of Q1 and Q7, and the voltages at the 1 - terminal of capacitor C1 and the 2 - terminal of capacitor C2 rise.

[0044] For zero - current turn - on, the current rise rate is delayed through inductors L1 - L6, and the switching devices in zero - current state are turned on, thereby achieving zero - current turn - on. The working principle of the bridge - arm circuit of the present invention is as follows:

[0045] During the positive half - cycle of the AC power supply, when Q1, Q3, Q5, Q7 are in the off state initially:

[0046] When Q2 and Q6 are turned off and Q4 and Q8 are turned on, at this time, the currents in L1 and L4 are 0, so I1 = 0 (I1 is the current in inductor L1), I5 = 0 (I5 is the current flowing through inductor L4 to Q5). At this time, turn off Q4 and Q8, and the currents in L2 and L3 flow through the diodes on Q3 and Q7. At this time, turn on Q1 and Q5, and I1 and I5 rise slowly, and Q1 and Q5 are zero - current turned on. The currents I4 (the current flowing through inductor L2 to Q4) and I8 (the current flowing through inductor L3 to Q8) in L2 and L3 will gradually be pulled to 0. Similarly, when Q4 and Q8 are turned off and Q2 and Q6 are turned on, at this time, the currents in L2 and L3 are 0, so I3 = 0 (I3 is the current flowing through L2 to Q3), I7 = 0 (I7 is the current flowing through L3 to Q7). At this time, turn off Q2 and Q6, and the currents in L1 and L4 flow through the diodes on Q1 and Q5. At this time, turn on Q3 and Q7, and I3 and I7 rise slowly, and Q3 and Q7 are zero - current turned on. The currents I2 (the current flowing through inductor L1 to Q2) and I6 (the current flowing through L4 to Q6) in L1 and L4 will gradually be pulled to 0.

[0047] During the negative half - cycle of the AC power supply, when Q2, Q4, Q6, Q8 are in the off state initially:

[0048] When Q1 and Q5 are turned off and Q3 and Q7 are turned on, the currents in L2 and L3 are zero. Turn off Q3 and Q7, and the currents in L1 and L4 flow through the diodes in Q4 and Q8. Turn on Q2 and Q6 to achieve zero-current turn-on of Q2 and Q6. The current flowing through Q4 via L1 is pulled to zero, and the current flowing through Q8 via L4 is pulled to 0. When Q3 and Q7 are turned off and Q1 and Q5 are turned on, the current flowing through Q4 via L1 is gradually pulled to 0, and the current flowing through Q8 via L4 is gradually pulled to 0. Turn off Q3 and Q7, and the currents in L2 and L3 flow through Q2 and Q6. Turn on Q4 and Q8 to achieve zero-current turn-on of Q4 and Q8. At this time, the currents flowing through Q2 via L2 and through Q6 via L3 will both be gradually pulled to 0.

[0049] In one example, a bridge arm circuit unit with zero-voltage turn-off and zero-current turn-on includes multiple bridge arm circuits described in any one or more of the above examples. The bridge arm circuits are cascaded, that is, cascaded between the last bridge arm of the upper-level bridge arm circuit and the first bridge arm of the lower-level bridge arm circuit to form a multilevel conversion circuit.

[0050] The present invention also includes a control method for a bridge arm circuit with zero-voltage turn-off and zero-current turn-on, which is used to control the circuit formed by any one or a combination of multiple examples above. The execution subject of the method is a control module. For zero-voltage turn-off, it includes the following steps:

[0051] In the positive half-cycle of the AC power supply, when turning off Q3, Q2, Q5, Q8 and turning on Q1, Q4, Q7, Q6, the voltages at B2 and B3 are 0. Turn off Q4 and Q6, and the voltages at the 2 ends of capacitor C1 and the 1 end of capacitor C2 rise slowly (from 0 to Vdc), that is, it is zero-voltage turn-off when turning off Q4 and Q6. When turning off Q1, Q4, Q7, Q6 and turning on Q3, Q2, Q5, Q8, the voltages at B1 and B4 are 0. Turn off Q2 and Q8, and the voltages at the 1 end of capacitor C1 and the 2 end of capacitor C2 rise slowly (from 0 to Vdc), that is, it is zero-voltage turn-off when turning off Q2 and Q8.

[0052] In the negative half-cycle of the AC power supply, when Q1, Q4, Q7, Q6 are turned off and Q2, Q3, Q8, Q5 are turned on, the voltages at B2 and B3 are zero. Turn off Q3 and Q5, and capacitors C1 and C2 start to charge to achieve zero-voltage turn-off of Q3 and Q5, and the voltages at the 2 end of capacitor C1 and the 1 end of capacitor C2 rise. When turning off Q2, Q3, Q5, Q8 and turning on Q1, Q4, Q7, Q6, the voltages at B1 and B4 are zero. Turn off Q1 and Q7 to achieve zero-voltage turn-off of Q1 and Q7, and the voltages at the 1 end of capacitor C1 and the 2 end of capacitor C2 rise.

[0053] For zero-current turn-on, it includes the following steps:

[0054] During the positive half - cycle of the AC power supply, when Q1, Q3, Q5, and Q7 are in the off state in the initial state:

[0055] When Q2 and Q6 are turned off and Q4 and Q8 are turned on, the currents in L1 and L4 are 0 at this time, so I1 = 0 and I5 = 0. Then Q4 and Q8 are turned off, and the currents in L2 and L3 flow through the diodes on Q3 and Q7. Q1 and Q5 are turned on, and I1 and I5 rise slowly (starting from zero current and rising slowly). There is no current flowing to Q1 and Q5 instantaneously when Q1 and Q5 are turned on, realizing zero - current turn - on of Q1 and Q5;

[0056] When Q4 and Q8 are turned off and Q2 and Q6 are turned on, the currents in L2 and L3 are 0 at this time, so I3 = 0 and I7 = 0. Then Q2 and Q6 are turned off, and the currents in L1 and L4 flow through the diodes on Q1 and Q5. Q3 and Q7 are turned on, and I3 and I7 rise slowly (starting from zero current and rising slowly). There is no current flowing to Q3 and Q7 instantaneously when Q3 and Q7 are turned on, realizing zero - current turn - on of Q3 and Q7.

[0057] During the negative half - cycle of the AC power supply, when Q2, Q4, Q6, and Q8 are in the off state in the initial state:

[0058] When Q1 and Q5 are turned off and Q3 and Q7 are turned on, the current in L2 and L3 is zero. Q3 and Q7 are turned off, and the currents in L1 and L4 flow through the diodes on Q4 and Q8. Q2 and Q6 are turned on, realizing zero - current turn - on of Q2 and Q6. The current flowing through Q4 via L1 is pulled to zero, and the current flowing through Q8 via L4 is pulled to 0;

[0059] When Q3 and Q7 are turned off and Q1 and Q5 are turned on, the current flowing through Q4 via L1 is gradually pulled to 0, and the current flowing through Q8 via L4 is gradually pulled to 0. Q3 and Q7 are turned off, and the current in L2 and L3 flows through Q2 and Q6. Q4 and Q8 are turned on, realizing zero - current turn - on of Q4 and Q8. At this time, the current flowing through Q2 via L2 and the current flowing through Q6 via L3 will both be gradually pulled to 0.

[0060] The above - mentioned specific embodiments are detailed descriptions of the present invention. It cannot be determined that the specific embodiments of the present invention are only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions and substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A bridge arm circuit with zero-voltage turn-off and zero-current turn-on. The bridge arm circuit is located between the power supply end and the load end, and includes cascaded first, second, third, and fourth bridge arms. The upper and lower arms of the first bridge arm are respectively provided with a first switching device and a second switching device. The upper and lower arms of the second bridge arm are respectively provided with a third switching device and a fourth switching device. The upper and lower arms of the third bridge arm are respectively provided with a fifth switching device and a sixth switching device. The upper and lower arms of the fourth bridge arm are respectively provided with a seventh switching device and an eighth switching device. The eight switching devices are connected to a control module, and it is characterized in that, The midpoint of the first arm is connected to the first inductor, the midpoint of the second arm is connected to the second inductor, the first inductor and the second inductor are connected, and a first capacitor is provided between the midpoint of the first arm and the midpoint of the second arm; the midpoint of the third arm is connected to the third inductor, the midpoint of the fourth arm is connected to the fourth inductor, the third inductor and the fourth inductor are connected, and a second capacitor is provided between the midpoint of the third arm and the midpoint of the fourth arm; a fifth inductor is provided between the midpoint of the second arm and the midpoint of the fourth arm, and a sixth inductor is provided between the midpoint of the first arm and the midpoint of the third arm; the common connection point of the first inductor and the second inductor, and the common connection point of the third inductor and the fourth inductor are connected to the energy transfer inductor, and the energy transfer inductor is connected to the power supply terminal.

2. The arm circuit with zero-voltage turn-off and zero-current turn-on according to claim 1, characterized in that, The switching device is a transistor, which can be any one or more of MOSFET, IGBT, BJT, and triode.

3. The arm circuit with zero-voltage turn-off and zero-current turn-on according to claim 1, characterized in that, All the switching devices in the arm circuit are IGBTs. The emitter of the first switching device is connected to the collector of the second switching device, the emitter of the third switching device is connected to the collector of the fourth switching device, the emitter of the fifth switching device is connected to the collector of the sixth switching device, and the emitter of the seventh switching device is connected to the collector of the eighth switching device; the collector of the first switching device is connected to the collector of the third switching device, the collector of the third switching device is connected to the collector of the fifth switching device, and the collector of the fifth switching device is connected to the collector of the seventh switching device; the emitter of the second switching device is connected to the emitter of the fourth switching device, the emitter of the fourth switching device is connected to the emitter of the sixth switching device, and the emitter of the sixth switching device is connected to the emitter of the eighth switching device. The gates of the eight switching devices are all connected to the control module.

4. A leg circuit with zero-voltage turn-off and zero-current turn-on according to any one of claims 1-3, characterized in that, The number of the arm circuits is at least two.

5. A control method for a leg circuit with zero-voltage turn-off and zero-current turn-on, characterized in that, The execution subject of the method is the control module, which is used to control the arm circuit according to any one of claims 1-4, and includes the following steps: Control the switching sequence of the switching devices in each arm to charge and discharge the first capacitor and the second capacitor. Through the charge and discharge process of the first capacitor and the second capacitor, turn off the switching devices on the zero-voltage side of the first capacitor and the second capacitor to achieve zero-voltage turn-off. Control the switching sequence of the switching devices in each arm to adjust the current changes in the first inductor, the second inductor, the third inductor, the fourth inductor, the fifth inductor, and the sixth inductor, delay the rising speed of the current in the corresponding inductor, and turn on the switching devices in zero current to achieve zero-current turn-on.

6. The control method of the bridge arm circuit with zero-voltage turn-off and zero-current turn-on according to claim 5, characterized in that, Zero-voltage turn-off includes: In the positive half-cycle of the AC power supply: When turning off the third switching device, the second switching device, the fifth switching device, and the eighth switching device, and turning on the first switching device, the fourth switching device, the seventh switching device, and the sixth switching device, the voltages at the midpoints of the second arm and the third arm are zero. Turn off the fourth switching device and the sixth switching device, and the voltages at one end of the first capacitor close to the midpoint of the second arm and one end of the second capacitor close to the midpoint of the third arm rise, realizing zero-voltage turn-off of the fourth switching device and the sixth switching device. When the first switch device, the fourth switch device, the seventh switch device, and the sixth switch device are turned off and the third switch device, the second switch device, the fifth switch device, and the eighth switch device are turned on, the voltages at the midpoints of the first arm and the fourth arm are zero. When the second switch device and the eighth switch device are turned off, the voltages at one end of the first capacitor close to the midpoint of the first arm and one end of the second capacitor close to the midpoint of the fourth arm rise, achieving zero-voltage turn-off of the second switch device and the eighth switch device; In the negative half-cycle of the AC power supply: When the first switch device, the fourth switch device, the seventh switch device, and the sixth switch device are turned off and the second switch device, the third switch device, the eighth switch device, and the fifth switch device are turned on, the voltages at the midpoints of the second arm and the third arm are zero. When the third switch device and the fifth switch device are turned off, zero-voltage turn-off of the third switch device and the fifth switch device is achieved, and the voltages at one end of the first capacitor close to the midpoint of the second arm and one end of the second capacitor close to the midpoint of the third arm rise; When the second switch device, the third switch device, the fifth switch device, and the eighth switch device are turned off and the first switch device, the fourth switch device, the seventh switch device, and the sixth switch device are turned on, the voltages at the midpoints of the first arm and the fourth arm are zero. When the first switch device and the seventh switch device are turned off, zero-voltage turn-off of the first switch device and the seventh switch device is achieved, and the voltages at one end of the first capacitor close to the midpoint of the first arm and one end of the second capacitor close to the midpoint of the fourth arm rise; Zero-current turn-on includes: In the positive half-cycle of the AC power supply, when the first switch device, the third switch device, the fifth switch device, and the seventh switch device are in the off state initially: When the second switch device and the sixth switch device are turned off and the fourth switch device and the eighth switch device are turned on, the currents in the first inductor and the fourth inductor are zero. When the fourth switch device and the eighth switch device are turned off, the currents in the second inductor and the third inductor flow through the diodes on the third switch device and the seventh switch device, and the first switch device and the fifth switch device are turned on, achieving zero-current turn-on of the first switch device and the fifth switch device; When the fourth switch device and the eighth switch device are turned off and the second switch device and the sixth switch device are turned on, the currents in the second inductor and the third inductor are zero. When the second switch device and the sixth switch device are turned off, the currents in the first inductor and the fourth inductor flow through the diodes on the first switch device and the fifth switch device, and the third switch device and the seventh switch device are turned on, achieving zero-current turn-on of the third switch device and the seventh switch device; In the negative half-cycle of the AC power supply, when the second switch device, the fourth switch device, the sixth switch device, and the eighth switch device are in the off state initially: When the first switch device and the fifth switch device are turned off and the third switch device and the seventh switch device are turned on, the currents in the second inductor and the third inductor are zero. Turn off the third switch device and the seventh switch device. The currents in the first inductor and the fourth inductor flow through the diodes of the fourth switch device and the eighth switch device. Turn on the second switch device and the sixth switch device to achieve zero-current turn-on of the second switch device and the sixth switch device. The current flowing through the fourth switch device via the first inductor is zero, and the current flowing through the eighth switch device via the fourth inductor is zero. When the third switch device and the seventh switch device are turned off and the first switch device and the fifth switch device are turned on, the current flowing through the fourth switch device via the first inductor is zero and the current flowing through the eighth switch device via the fourth inductor is zero. Turn off the third switch device and the seventh switch device. The currents in the second inductor and the third inductor flow through the second switch device and the sixth switch device. Turn on the fourth switch device and the eighth switch device to achieve zero-current turn-on of the fourth switch device and the eighth switch.

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