A soft switch bridge arm circuit and control method

Abstract

The present invention discloses a soft switch bridge arm circuit and control method, which belongs to the field of soft switch circuits. An inductor is respectively introduced at the midpoint of the two bridge arms of the bridge arm circuit, and the conduction and shutdown timing control of the switch device are coordinated to realize the zero current conduction of the switch device; on the basis of introducing an inductor at the midpoint of the two bridge arms, a capacitor is arranged between the two bridge arms, and the conduction and shutdown timing control of the switch device are coordinated based on the capacitor charging and discharging principle to realize the zero voltage shutdown of the switch device. The above zero current conduction circuit and zero voltage shutdown circuit can adapt to all existing bridge arm type circuits, without the need to design an LC resonant circuit separately, and have a wide range of applications.

Description

Technical Field

[0001] The present invention relates to the field of soft-switching circuits, and particularly to a soft-switching bridge arm circuit and a control method thereof. 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 are switched. As Figure 1 shown, in a traditional hard-switching circuit, both the voltage and current are non-zero during the switching process, resulting in overlap and generating switching losses; moreover, the voltage and current change rapidly, and the waveform shows 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 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 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. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of the prior art and provide a soft-switching bridge arm circuit and a control method thereof.

[0005] The purpose of the present invention is achieved through the following technical solutions: A soft-switching bridge arm circuit, the bridge arm circuit is a single-bridge arm circuit located between the power supply end and the load end; the single-bridge arm circuit includes a first bridge arm and a second 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, and 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 four switching devices are connected to a control module. It is characterized in that 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, and the first inductor is connected to the second inductor. The common connection point of the first inductor and the second inductor is connected to the power supply end, and an energy transfer inductor is provided at the positive pole of the power supply, thereby forming a zero-current conduction circuit.

[0006] In an example, a first capacitor is provided between the midpoint of the first bridge arm and the midpoint of the second bridge arm, thereby forming a zero-voltage turn-off circuit.

[0007] In one example, a first capacitor and a fifth switching device connected in series are provided between the midpoints of the first bridge arm and the second bridge arm. The fifth switching device is connected to the control module. By controlling the turn-off and turn-on of the fifth switching device, the switching between the zero-current turn-on circuit and the zero-voltage turn-off circuit is achieved, that is, a zero-current turn-on and zero-voltage turn-off switching circuit is formed.

[0008] A soft-switching bridge arm circuit of the present invention includes at least two single bridge arm circuits formed by combining any one of the above examples or a plurality of examples. The single bridge arm circuits can be cascaded, paralleled, or mixedly connected, and each bridge arm circuit realizes the single bridge arm control in the switching power supply topology as an independent module.

[0009] The present invention further includes a soft-switching bridge arm circuit and a control method for controlling the zero-current turn-on circuit. Taking the control module as the execution body, the method includes the following steps:

[0010] Control the switching timings of the switching devices in each bridge arm to adjust the current changes of the first inductor and the second inductor, thereby delaying the rising speed of the current on the corresponding inductor, and turn on the switching device in zero current to achieve zero-current turn-on.

[0011] In one example, zero-current turn-on includes:

[0012] In the positive half-cycle of the AC power supply, when the first switching device and the third switching device are in the off state in the initial state:

[0013] When the second switching device is off and the fourth switching device is on, the current I1 on the first inductor is zero. After turning off the fourth switching device, the first switching device is turned on to achieve zero-current turn-on of the first switching device, and the current I3 flowing through the third switching device via the second inductor is zero;

[0014] When the fourth switching device is off and the second switching device is on, the current I3 flowing through the third switching device via the second inductor is zero. After turning off the second switching device, the third switching device is turned on to achieve zero-current turn-on of the third switching device;

[0015] In the negative half-cycle of the AC power supply, when the second switching device, the fourth switching device, and the fifth switching device are in the off state in the initial state:

[0016] When the first switching device is off and the third switching device is on, the current I2' on the second inductor is zero. After turning off the third switching device, the second switching device is turned on to achieve zero-current turn-on of the second switching device, and the current I4' flowing through the fourth switching device via the first inductor is zero;

[0017] When the fourth switching device is turned off and the second switching device is turned on, the current I4' flowing through the fourth switching device via the first inductor is zero. After turning off the second switching device and then turning on the fourth switching device, zero-current turn-on of the fourth switching device is achieved.

[0018] A soft-switching bridge arm circuit and a control method thereof according to the present invention are used to control a zero-voltage turn-off circuit, with a control module as the execution entity. The method includes the following steps:

[0019] Control the switching timing of the switching devices in each bridge arm to charge and discharge the first capacitor. Through the charge and discharge process of the first capacitor, turn off the switching device on the zero-voltage side of the first capacitor to achieve zero-voltage turn-off.

[0020] In an example, zero-voltage turn-off includes:

[0021] When the first switching device, the second switching device, and the third switching device are in the off state and the fourth switching device is in the on state, then turn on the first switching device. At this time, the voltages at both ends of the fourth switching device are both zero, and the voltage difference between the two ends is zero. Turn off the fourth switching device, and the voltage at the end of the first capacitor close to the midpoint of the second bridge arm rises slowly. The fourth switching device is turned off at zero voltage.

[0022] When the second switching device, the third switching device, and the fourth switching device are in the off state and the first switching device is in the on state, turn on the fourth switching device. At this time, the voltages at both ends of the first switching device are both the rectified DC voltage, and the voltage difference between the two ends is zero. Turn off the first switching device, and the voltage at the end of the first capacitor close to the midpoint of the first bridge arm drops slowly. At this time, the first switching device is turned off at zero voltage.

[0023] When the first switching device, the second switching device, and the fourth switching device are in the off state and the third switching device is in the on state, turn on the second switching device. The voltages at both ends of the third switching device are both the rectified DC voltage, and the voltage difference between the two ends is zero. Turn off the third switching device, and the voltage at the end of the first capacitor close to the midpoint of the second bridge arm drops slowly. At this time, the third switching device is turned off at zero voltage.

[0024] When the first switching device, the third switching device, and the fourth switching device are in the off state and the second switching device is in the on state, turn on the third switching device. At this time, the voltages at both ends of the second switching device are both zero, and the voltage difference between the two ends is zero. Turn off the second switching device, and the voltage at the end of the first capacitor close to the midpoint of the first bridge arm drops slowly. The second switching device is turned off at zero voltage.

[0025] A soft-switching bridge arm circuit and a control method thereof according to the present invention are characterized in that they are used to control a zero-current turn-on and zero-voltage turn-off switching circuit. The method includes the following steps:

[0026] Turn off the fifth switching device, control the switching timings of the switching devices in each arm to adjust the current variations of the first inductor and the second inductor, thereby delaying the rising speed of the current on the corresponding inductor, and turn on the switching device in zero current state to achieve zero-current turn-on;

[0027] Turn on the fifth switching device, control the switching timings of the switching devices in each arm to enable the first capacitor to be charged and discharged. Through the charging and discharging process of the first capacitor, turn off the switching device on the zero-voltage side of the first capacitor to achieve zero-voltage turn-off.

[0028] In one example, when controlling the fifth switching device to turn off, the method includes the following steps:

[0029] In the negative half-cycle of the AC power supply, when the first switching device, the third switching device, and the fifth switching device are in the off state in the initial state:

[0030] When the second switching device is off and the fourth switching device is on, the current I1 on the first inductor is zero. After turning off the fourth switching device, turn on the first switching device to achieve zero-current turn-on of the first switching device, and the current I3 flowing through the third switching device via the second inductor is zero;

[0031] When the fourth switching device is off and the second switching device is on, the current I3 flowing through the third switching device via the second inductor is zero. After turning off the second switching device, turn on the third switching device to achieve zero-current turn-on of the third switching device;

[0032] In the negative half-cycle of the AC power supply, when the second switching device, the fourth switching device, and the fifth switching device are in the off state in the initial state:

[0033] When the first switching device is off and the third switching device is on, the current I2' on the second inductor is zero. After turning off the third switching device, turn on the second switching device to achieve zero-current turn-on of the second switching device, and the current I4' flowing through the fourth switching device via the first inductor is zero;

[0034] When the fourth switching device is off and the second switching device is on, the current I4' flowing through the fourth switching device via the first inductor is zero. After turning off the second switching device, turn on the fourth switching device to achieve zero-current turn-on of the fourth switching device;

[0035] When controlling the fifth switching device to turn on, the method includes the following steps:

[0036] When the first switch device, the second switch device, and the third switch device are in the off state and the fourth switch device is in the on state, the first switch device is turned on again. At this time, the voltages at both ends of the fourth switch device are zero, and the voltage difference between the two ends is zero. The fifth switch device is turned on, and the fourth switch device is turned off. The voltage at one end of the first capacitor close to the midpoint of the second bridge arm rises slowly, and the fourth switch device is turned off with zero voltage;

[0037] When the second switch device, the third switch device, and the fourth switch device are in the off state, and the first switch device is in the on state, the fourth switch device is turned on. At this time, the voltages at both ends of the first switch device are rectified DC voltages, and the voltage difference between the two ends is zero. When the first switch device is turned off, the voltage at one end of the first capacitor close to the midpoint of the first bridge arm slowly decreases. At this time, the first switch device is turned off with zero voltage;

[0038] When the first switch device, the second switch device, and the fourth switch device are in the off state and the third switch device is in the on state, the second switch device is turned on, the voltages at both ends of the third switch device are rectified DC voltages, and the voltage difference between the two ends is zero. When the third switch device is turned off, the voltage at one end of the first capacitor close to the midpoint of the second bridge arm slowly decreases, and the third switch device is turned off with zero voltage;

[0039] When the first switch device, the third switch device, and the fourth switch device are in the off state and the second switch device is in the on state, the third switch device is turned on, at which time the voltages at both ends of the second switch device are zero, and the voltage difference between the two ends is zero. The fifth switch device is turned on, and the second switch device is turned off. The voltage at one end of the first capacitor close to the midpoint of the first bridge arm slowly decreases, and the second switch device is turned off with zero voltage.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. In one example, an inductor is introduced at the midpoint of each of the two bridge arms to slow down the rate of current rise. The zero current conduction of the switch device is achieved by coordinating the on and off timing control of the switch device. This can be applied to all existing bridge arm circuit application scenarios. Soft switching can be achieved without the need to design an LC resonant circuit separately, which reduces switching losses and has a wide range of applications.

[0042] 2. In one example, an inductor is introduced at the midpoint of each bridge arm, and a capacitor is set between the two bridge arms. Based on the capacitor charging and discharging principle and the on and off timing control of the switch device, the zero voltage shutdown of the switch device is achieved. It can be applied to all existing bridge arm circuit application scenarios. Soft switching processing can be achieved without the need to design an LC resonant circuit separately, reducing switching losses and having a wide range of applications.

[0043] ​3. In one example, on the basis of introducing an inductor at the midpoints of two bridge arms respectively and setting a capacitor between the bridge arms, a fifth switching device connected in series with the capacitor is introduced. By controlling the on and off of the fifth switching device, the switching between the zero-voltage turn-off circuit and the zero-current turn-on circuit is realized, which can well meet the requirements of soft-switching turn-on and turn-off of the circuit and has a wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The following further describes in detail the specific embodiments of the present invention with reference to the accompanying drawings. The accompanying drawings provided here are used to provide a further understanding of the present application and constitute a part of the present application. The same reference numerals are used to represent the same or similar parts in these drawings. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application.

[0045] Figure 1 It is a voltage and current curve diagram during the switching process of an existing hard-switching circuit;

[0046] Figure 2 It is a voltage and current curve diagram during the switching process of a soft-switching circuit with added resonant elements;

[0047] Figure 3 It is a schematic diagram of the zero-current turn-on circuit provided by an example of the present invention;

[0048] Figure 4 It is a schematic diagram of the zero-voltage turn-off circuit provided by an example of the present invention;

[0049] Figure 5 It is a schematic diagram of the zero-current turn-on and zero-voltage turn-off circuit provided by an example of the present invention;

[0050] Figure 6 It is a schematic diagram of an existing Boost converter circuit;

[0051] Figure 7 It is a schematic diagram of applying the zero-voltage turn-off circuit to the Boost converter provided by an example of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] 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 part of the embodiments of the present invention, rather than all of the embodiments. 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.

[0053] 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, rather than indicating or implying 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 to the present invention. In addition, the use of ordinal numbers (e.g., "first and second", "first to fourth", etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0054] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected", and "coupled" 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 circumstances.

[0055] 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.

[0056] A soft-switching bridge arm circuit of the present invention, the bridge arm circuit is a single-bridge arm circuit or a double-bridge arm circuit, or even multiple cascaded bridge arm circuits, and the bridge arm circuit is located between the power supply end and the load end.

[0057] In one example, taking a single-bridge-arm circuit as an example, at this time, the single-bridge-arm circuit includes a first bridge arm and a second bridge arm. The first bridge arm and the second bridge arm form an H-bridge circuit (single bridge arm), and the second bridge arm is connected to the load terminal. Optionally, the second bridge arm is connected to the load terminal through a voltage transformation processing circuit. For example, the second bridge arm is connected to the load terminal through a boost circuit. The upper arm and the lower arm of the first bridge arm are respectively provided with a first switching device Q1 and a second switching device Q2. The upper arm and the lower arm of the second bridge arm are respectively provided with a third switching device Q3 and a fourth switching device Q4. Q1, Q2, Q3, and Q4 are connected to the controller in the control module. The switching device is a transistor, such as any one or more of MOSFET, IGBT, BJT, triode, etc. A diode is provided between the source and the drain of the transistor or between the emitter and the collector of the transistor. Of course, if the emitter and the collector of the transistor are integrated with a diode itself, a new diode may not be integrated additionally. For example, IGBT does not need to integrate a diode again. In this example, IGBT is used. The emitter of Q1 is connected to the collector of Q2. The collector of Q1 is connected to the collector of Q3. The emitter of Q3 is connected to the collector of Q4. The emitter of Q4 is connected to the emitter of Q2. The gates of Q1, Q2, Q3, and Q4 are connected to the controller (not shown in the figure).

[0058] As Figure 3 shown, based on the existing circuit, a first inductor L1 is connected to the midpoint of the first bridge arm, and a second inductor L2 is connected to the midpoint of the second bridge arm in the single-bridge-arm circuit of the present invention. Moreover, the first inductor L1 and the second inductor L2 are connected. The common connection point of the first inductor L1 and the second inductor L2 is connected to the power supply terminal. An energy transfer inductor is provided at the positive pole of the power supply, that is: the common connection point of the first inductor L1 and the second inductor L2 is connected to the energy transfer inductor L, and the energy transfer inductor L is connected to the positive pole of the AC power supply. In this example, inductors L1 and L2 are introduced to delay the rising rate of the current and form a zero-current turn-on circuit. The zero-current turn-on working principle of the bridge arm circuit of the present invention is as follows:

[0059] In the positive half-cycle of the AC power supply, when Q1 and Q3 are in the off state initially:

[0060] When Q2 is off and Q4 is on, at this time, the current on L1 is 0, then I1 = 0. At this time, turn off Q4. The current on L2 flows through the diode on Q3. At this time, turn on Q1. I1 rises slowly. Q1 is turned on with zero current. The current I3 on L2 will gradually be pulled to 0 current. Similarly, when Q4 is off and Q2 is on, at this time, the current on L2 is 0, then I3 = 0. At this time, turn off Q2. The current on L1 flows through the diode on Q1. At this time, turn on Q3. I3 rises slowly. Q3 is turned on with zero current. The current I1 on L1 will gradually be pulled to 0 current.

[0061] During the negative half - cycle of the AC power supply, when Q2 and Q4 are in the off state initially:

[0062] When Q1 is off and Q3 is on, the current I1 on L1 will gradually decrease to 0, the current I2' on L2 is 0. After turning off Q3 and then turning on Q2, the current on L2 starts to flow through the diode on Q3. By turning on Q2, zero - current turn - on of Q2 is achieved, and the current I4' flowing through Q4 via the first inductor is zero;

[0063] When Q4 is off and Q2 is on, the current I3 on the second inductor L2 will gradually decrease to 0, and the current I4' flowing through Q4 via the first inductor is zero. After turning off Q2, the current on L1 starts to flow through the diode on Q1, and then Q4 is turned on to achieve zero - current turn - on of Q4; as Q4 turns on, the current I3 on L2 will gradually be pulled to 0 current.

[0064] Preferably, the zero - current turn - on circuit of the present invention is used to replace the existing bridge - arm circuit. At this time, at the circuit control level, the soft - switch control of the present invention is embedded in the control of the original circuit, which is essentially adding a layer of judgment to the original circuit control method. It can achieve zero - current turn - on while realizing level - conversion processing, thereby reducing the turn - on loss of the switching device. Of course, the bridge - arm circuit of the present invention can also be integrated with the existing circuit.

[0065] Based on the previous example, as Figure 4 shown, a first capacitor C is provided between the mid - point of the first bridge - arm and the mid - point of the second bridge - arm to form a zero - voltage turn - off circuit. At this time, the connection point of the first capacitor C and the mid - point of the first bridge - arm is defined as B1, the connection point of the first capacitor C and the mid - point of the second bridge - arm is defined as B2, the end of the first capacitor close to B1 is defined as terminal 1, and the end of the first capacitor close to B2 is defined as terminal 2. The zero - voltage turn - off working principle of the bridge - arm circuit of the present invention is as follows:

[0066] I. When Q2 and Q3 are in the off state and Q1 and Q4 are in the on state, there are two cases to enter this state:

[0067] (1) It may be that when Q1, Q2, and Q3 are in the off state and Q4 is in the on state, turning on Q1 enters this state,

[0068] (2) It may also be that when Q2, Q3, and Q4 are in the off state and Q1 is in the on state, turning on Q4 enters this state.

[0069] If entering this state from (1), at this time, since the voltages at both ends of Q4 are both 0 and the voltage difference between the two ends is 0, turning off Q4, the voltage at terminal 2 of the capacitor rises slowly. At this time, Q4 is turned off with zero voltage. After Q4 is completely turned off, turn off Q5.

[0070] If entering this state from (2), at this time, since the voltages at both ends of Q1 are both Vdc and the voltage difference between the two ends is 0, turn off Q1, and the voltage at one end of the capacitor slowly drops. At this time, Q1 is turned off with zero voltage.

[0071] Second, when Q1 and Q4 are in the off state and Q2 and Q3 are in the on state, there are two situations to enter this state at this time:

[0072] (3) It may be that when Q1, Q2, and Q4 are in the off state and Q3 is in the on state, turn on Q2 to enter this state.

[0073] (4) It may also be that when Q1, Q3, and Q4 are in the off state and Q2 is in the on state, turn on Q3 to enter this state.

[0074] If entering this state from (3), at this time, since the voltages at both ends of Q3 are both Vdc and the voltage difference between the two ends is 0, turn off Q3, and the voltage at the second end of the capacitor slowly drops. At this time, Q3 is turned off with zero voltage.

[0075] If entering this state from (4), at this time, since the voltages at both ends of Q2 are both 0 and the voltage difference between the two ends is 0, turn off Q2. After that, the voltage at one end of the capacitor slowly drops. At this time, Q2 is turned off with zero voltage. After Q2 is completely turned off, turn off Q5.

[0076] Based on the previous example, as Figure 5 shown, a fifth switching device Q5 connected in series with the first capacitor C is provided between the midpoint of the first bridge arm and the midpoint of the second bridge arm, and Q5 is connected to the control module. At this time, when Q5 is turned off, the circuit is equivalent to a zero-current conduction circuit; when Q5 is turned on, the circuit is equivalent to a zero-voltage turn-off circuit. Q5 needs to be turned on an instant before Q4 or Q2 is turned off and turned off after Q4 or Q2 is completely turned off. Specifically, the working principle of the bridge arm circuit at this time is as follows:

[0077] For zero-current conduction control, in the positive half-cycle of the AC power supply, at this time, the initial states of Q1, Q3, and Q5 are off states. When Q2 is turned off and Q4 is turned on, at this time, the current on L1 is 0, that is, I1 = 0. At this time, turn off Q4, and the current on L2 flows through the diode on Q3. At this time, turn on Q1, and I1 slowly rises. Q1 is zero-current conduction, and the current I3 on L2 will gradually be pulled to 0 current. When Q4 is turned off and Q2 is turned on, at this time, as known from the above item 1, the current on L2 is 0 at this time, that is, I3 = 0. At this time, turn off Q2, and the current on L1 flows through the diode on Q1. At this time, turn on Q3, and I3 slowly rises. Q3 is zero-current conduction, and the current I1 on L1 will gradually be pulled to 0 current.

[0078] For zero-current conduction control, in the negative half-cycle of the AC power supply, at this time, the initial states of Q2, Q4, and Q5 are off states.

[0079] When Q1 is turned off and Q3 is turned on, the current I1 on L1 will gradually decrease to 0, and the current I2' on L2 is 0. After turning off Q3 and then turning on Q2, the current on L2 starts to flow through the diode on Q3. By turning on Q2, zero-current turn-on of Q2 is achieved, and the current I4' flowing through Q4 via the first inductor is zero. When Q4 is turned off and Q2 is turned on, the current I3 on the second inductor L2 will gradually decrease to 0, and the current I4' flowing through Q4 via the first inductor is zero. After turning off Q2, the current on L1 starts to flow through the diode on Q1, and by turning on Q4, zero-current turn-on of Q4 is achieved. As Q4 is turned on, the current I3 on L2 will gradually be pulled to 0 current.

[0080] For zero-voltage turn-off control, control the fifth switching device to turn on. At this time:

[0081] When Q1, Q2, and Q3 are in the off state and Q4 is in the on state, then turn on Q1. At this time, the voltages at both ends of Q4 are both 0, and the voltage difference between the two ends is 0. Turn on Q5 and turn off Q4. The voltage at both ends of capacitor 2 rises slowly. Q4 is turned off with zero voltage. After Q4 is completely turned off, turn off Q5. Q4 is turned off with zero voltage. After Q4 is completely turned off, turn off Q5. When Q2, Q3, and Q4 are in the off state and Q1 is in the on state, turn on Q4. At this time, the voltages at both ends of Q1 are both Vdc, and the voltage difference between the two ends is 0. Turn off Q1. The voltage at both ends of capacitor 1 drops slowly. At this time, Q1 is turned off with zero voltage.

[0082] When Q1, Q2, and Q4 are in the off state and Q3 is in the on state, turn on Q2. The voltages at both ends of Q3 are both Vdc, and the voltage difference between the two ends is 0. Turn off Q3. The voltage at both ends of capacitor 2 drops slowly. At this time, Q3 is turned off with zero voltage. When Q1, Q3, and Q4 are in the off state and Q2 is in the on state, turn on Q3. At this time, the voltages at both ends of Q2 are both 0, and the voltage difference between the two ends is 0. Turn on Q5 and turn off Q2. The voltage at both ends of capacitor 1 drops slowly. Q2 is turned off with zero voltage. After Q2 is completely turned off, turn off Q5.

[0083] In one example, a soft-switching bridge arm circuit includes a plurality of single bridge arm circuits described in 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 serves as an independent module to achieve single bridge arm control in the switching power supply topology. Taking the cascading of single bridge arm circuits as an example, a double bridge arm circuit or a multilevel conversion circuit is formed. Two inductors led out from the midpoints of the two bridge arms in the first-stage single bridge arm circuit (the single bridge arm circuit close to the power supply end) are connected to the energy transfer inductor, and the energy transfer inductor is connected to the positive pole of the power supply. The two inductors led out from the midpoints of the two bridge arms in the subsequent single bridge arm circuits are both connected to the negative pole of the power supply. Taking the double bridge arm circuit as an example, at this time, the two single bridge arm circuits are connected in cascade. Specifically, the double bridge arm includes a first single bridge arm circuit and a second single bridge arm circuit. The first bridge arm circuit includes a first bridge arm and a second bridge arm. Switching devices Q1 and Q2 are respectively provided on the upper and lower bridge arms of the first bridge arm, and switching devices Q3 and Q4 are respectively provided on the upper and lower bridge arms of the second bridge arm. The midpoint of the first bridge arm is connected to inductor L1, and the midpoint of the second bridge arm is connected to inductor L2, and inductors L1 and L2 are connected. The common connection point of inductors L1 and L2 is connected to the energy transfer inductor; the second bridge arm circuit includes a third bridge arm and a fourth bridge arm. The fourth bridge arm is connected to the load end. Optionally, the fourth bridge arm is connected to the load end through a voltage transformation processing circuit. Switching devices Q1' and Q2' are respectively provided on the upper and lower bridge arms of the third bridge arm, and switching devices Q3' and Q4' are respectively provided on the upper and lower bridge arms of the fourth bridge arm. The midpoint of the third bridge arm is connected to inductor L1', and the midpoint of the fourth bridge arm is connected to inductor L1', and inductors L1' and L2' are connected. The common connection point of inductors L1' and L2' is connected to the negative pole of the AC power supply, and the positive pole of the AC power supply is connected to the energy transfer inductor. Preferably, a first capacitor C is provided between the midpoint of the first bridge arm and the midpoint of the second bridge arm, and a second capacitor C' is provided between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm. More preferably, a switching device Q5 in series with the first capacitor C is provided between the midpoint of the first bridge arm and the midpoint of the second bridge arm, and a switching device Q5' in series with the second capacitor C' is provided between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm.

[0084] Now, the application of the bridge arm circuit of the present invention will be further described. In this example, the zero voltage turn-off circuit is applied to a conventional boost converter as an example for description. The conventional boost converter circuit is as Figure 6 shown, and the zero voltage turn-off circuit of the present invention can be incorporated into the conventional boost converter. It should be noted that only the soft-switching principle is schematically shown by us. At this time, the voltage conversion process is simplified in the present invention, that is, the boost processing circuit cascaded after the bridge arm circuit is not schematically shown. At this time, in combination with the bridge arm circuit of the conventional boost converter, as Figure 7As shown, the boost converter with soft-switching function includes two leg circuits (the first leg circuit and the second leg circuit), and the two leg circuits are cascaded. Specifically, the first leg circuit includes a first leg and a second leg. Switching devices Q1 and Q2 are respectively provided on the upper leg and the lower leg of the first leg. Switching devices Q3 and Q4 are respectively provided on the upper leg and the lower leg of the second leg. The midpoint of the first leg is connected to inductor L1, and the midpoint of the second leg is connected to inductor L2. And inductors L1 and L2 are connected. The common connection point of inductors L1 and L2 is connected to the energy transfer inductor. The second leg circuit includes a third leg and a fourth leg. The fourth leg is connected to the load end (capacitor C2 and resistor R connected in parallel with the fourth leg). Switching devices Q1' and Q2' are respectively provided on the upper leg and the lower leg of the third leg. Switching devices Q3' and Q4' are respectively provided on the upper leg and the lower leg of the fourth leg. The midpoint of the third leg is connected to inductor L1', and the midpoint of the fourth leg is connected to inductor L1'. And inductors L1' and L2' are connected. The common connection point of inductors L1' and L2' is connected to the negative pole of the AC power supply, and the positive pole of the AC power supply is connected to the energy transfer inductor. Further, a first capacitor C1 is provided between the midpoint of the first leg and the midpoint of the second leg, and a second capacitor C1' is provided between the midpoint of the third leg and the midpoint of the fourth leg.

[0085] Applying the solution of the present invention to a conventional boost converter only requires inserting the corresponding soft-switching control sequence within the control sequence and duty cycle of the conventional solution. Q1 / Q3, Q2 / Q4, Q1' / Q3', Q2' / Q4' of the soft-switching solution respectively correspond to Q1, Q2, Q3, Q4 of the conventional solution (hereinafter, Q1o, Q2o, Q3o, Q4o are used instead). At this time, the control method is as follows: during the positive half-cycle of the AC, Q4o conducts, and Q1o and Q2o conduct alternately; during the negative half-cycle of the AC, Q3o conducts, and Q1o and Q2o conduct alternately.

[0086] Assume that it is the positive half-cycle of the AC at this time. During the switching process of the alternate conduction of Q1o and Q2o, the switching time (corresponding to the duty cycle) is the same as that of the conventional boost converter, and the switching method can directly insert the control method of the previous zero-voltage turn-off solution. At this time, the working principle of zero-voltage turn-off is as follows: when Q2 and Q3 are turned off and Q1 and Q4 are conducting, the voltage at B1 is Vdc (the DC voltage processed by the leg circuit), and the voltage at B2 is 0. At this time, when Q4 is turned off, the voltage at the 2 end of capacitor C1 will slowly rise to Vdc, and Q4 is zero-voltage turned off. Similarly, when Q4 and Q1 are turned off and Q3 and Q2 are conducting, the voltage at B2 is Vdc, and the voltage at B1 is 0. At this time, when Q2 is turned off, the voltage at the 1 end of capacitor C1 will slowly rise to Vdc, and Q2 is zero-voltage turned off.

[0087] When switching between the positive and negative half - cycles of the AC, Q4o will switch to Q2o conducting. The switching time point is the same as that of a conventional boost converter, and the switching method can also directly insert the control method of the previous zero - voltage turn - off scheme. Assume that during the positive half - cycle of the AC, Q4’ in Q4o conducts, and Q2’ in Q4o and Q1’, Q3’ in Q3o are all turned off. When switching, turn on Q1’. At this time, the state and control method of the right - hand bridge arm (the third bridge arm and the fourth bridge arm) referring to the control method of zero - voltage turn - off are: when Q2’, Q3’ are turned off and Q1’, Q4’ are conducting, the voltage at B1’ is Vdc, and the voltage at B2’ is 0. At this time, turn off Q4’, and the voltage at the two ends of capacitor C1’ will slowly rise to Vdc, and Q4’ is zero - voltage turn - off.

[0088] During the subsequent switching process where Q1o and Q2o conduct alternately, the switching time (corresponding to the duty cycle) is the same as that of a conventional boost converter, and the switching method can also directly insert the control method of the previous zero - voltage turn - off scheme. At this time, the control principle of the zero - voltage turn - off scheme is: when Q2, Q3 are turned off and Q1, Q4 are conducting, the voltage at B1 is Vdc, and the voltage at B2 is 0. At this time, turn off Q4, and the voltage at the two ends of capacitor C1 will slowly rise to Vdc, and Q4 is zero - voltage turn - off. Similarly, when Q4, Q1 are turned off and Q3, Q2 are conducting, the voltage at B2 is Vdc, and the voltage at B1 is 0. At this time, turn off Q2, and the voltage at the two ends of capacitor C1 will slowly rise to Vdc, and Q2 is zero - voltage turn - off.

[0089] The present invention controls each single - bridge - arm circuit as an independent part, and can complete soft - switching processing on the basis of the voltage conversion processing of the boost converter. Of course, this is just one application of the present invention. For all bridge - arm circuits, the zero - current turn - on and zero - voltage turn - off schemes of the present invention are applicable. Of course, the bridge - arm circuit of the present invention can also be directly used to replace the existing bridge - arm circuit, and soft - switching processing can be realized on the basis of realizing the voltage conversion processing of the existing bridge - arm circuit, with a wider application range.

[0090] The present invention also includes a control method for a soft - switching bridge - arm circuit, which is used to control the zero - current turn - on circuit. With the control module as the execution subject, the core idea of the method is: controlling the switching timing of the switching devices in each bridge arm, adjusting the current change of the first inductor L1 and the second inductor L2, thereby delaying the rising speed of the current on the corresponding inductor, and turning on the switching device in zero - current state to achieve zero - current turn - on.

[0091] Specifically, zero - current turn - on includes:

[0092] During the positive half - cycle of the AC power supply, when Q1 and Q3 are initially in the off state:

[0093] When Q2 is turned off and Q4 is turned on, the current I1 in the first inductor L1 is zero. Turn off Q4, and the current in L2 flows through the diode on Q3. At this time, turn on Q1, and the current I1 slowly rises from zero, that is, when Q1 is turned on, it is zero-current turn-on. The current I3 flowing through Q3 via the second inductor L2 is zero;

[0094] When Q4 is turned off and Q2 is turned on, the current I3 flowing through Q3 via the second inductor L2 is zero. Turn off Q2, and the current in L1 flows through the diode on Q1. At this time, turn on Q3, and I3 slowly rises from zero, that is, when Q3 is turned on, it is zero-current turn-on. The current I1 in L1 will gradually be pulled to zero current.

[0095] In the negative half-cycle of the AC power supply, when Q2 and Q4 are initially in the off state:

[0096] When Q1 is turned off and Q3 is turned on, the current I1 in L1 will gradually decrease to 0, and the current I2' in L2 is 0. After turning off Q3 and then turning on Q2, the current in L2 starts to flow through the diode on Q3. When Q2 is turned on, zero-current turn-on of Q2 is achieved, and the current I4' flowing through Q4 via the first inductor is zero;

[0097] When Q4 is turned off and Q2 is turned on, the current I3 in the second inductor L2 will gradually decrease to 0, and the current I4' flowing through Q4 via the first inductor is zero. After turning off Q2, the current in L1 starts to flow through the diode on Q1. When Q4 is turned on, zero-current turn-on of Q4 is achieved; as Q4 is turned on, the current I3 in L2 will gradually be pulled to zero current.

[0098] The present invention further includes a control method for a soft-switching bridge arm circuit, which is used to control the zero-voltage turn-off circuit. With a control module as the execution entity, the core concept of the method is: controlling the switching timing of the switching devices in each bridge arm to charge and discharge the capacitor C, and through the charge and discharge process of the capacitor C, turning off the switching device on the zero-voltage side of the capacitor C to achieve zero-voltage turn-off.

[0099] Specifically, zero-voltage turn-off includes:

[0100] When Q1, Q2, and Q3 are in the off state and Q4 is in the on state, then turn on Q1. At this time, the voltages at both ends of Q4 are both 0, and the voltage difference between the two ends is 0. Turn on Q5 and turn off Q4. The voltage at the two ends of the capacitor slowly rises, and Q4 is zero-voltage turned off. After Q4 is completely turned off, turn off Q5; when Q2, Q3, and Q4 are in the off state and Q1 is in the on state, turn on Q4. At this time, the voltages at both ends of Q1 are both Vdc, and the voltage difference between the two ends is 0. Turn off Q1, and the voltage at one end of the capacitor slowly decreases. At this time, Q1 is zero-voltage turned off;

[0101] When Q1, Q2, and Q4 are in the off state and Q3 is in the on state, turn on Q2. The voltages at both ends of Q3 are both Vdc, and the voltage difference between the two ends is 0. Turn off Q3, and the voltage at both ends of the capacitor slowly decreases. At this time, Q3 is turned off with zero voltage. When Q1, Q3, and Q4 are in the off state and Q2 is in the on state, turn on Q3. At this time, the voltages at both ends of Q2 are both 0, and the voltage difference between the two ends is 0. Turn on Q5, turn off Q2, and the voltage at both ends of the capacitor slowly decreases. Q2 is turned off with zero voltage. After Q2 is completely turned off, turn off Q5.

[0102] The present invention further includes a control method for a soft-switching bridge arm circuit, which is used to control the zero-current conduction and zero-voltage turn-off switching circuit. Taking the control module as the execution body, the core concept of the method is as follows:

[0103] Control Q5 to turn off, control the switching timings of the switching devices in each bridge arm, adjust the current changes of the first inductor L1 and the second inductor L2, and then delay the rising speed of the current on the corresponding inductor, and turn on the switching device in zero current to achieve zero-current conduction;

[0104] Control Q5 to turn on, control the switching timings of the switching devices in each bridge arm, charge and discharge the capacitor C, and turn off the switching device on the zero-voltage side of the capacitor C through the charge and discharge process of the capacitor C to achieve zero-voltage turn-off.

[0105] Specifically, when controlling Q5 to turn off to achieve zero-current conduction control, the method includes the following steps:

[0106] In the positive half-cycle of the AC power supply, the initial states of Q1, Q3, and Q5 are off states. When Q2 is off and Q4 is on, at this time, the current on L1 is 0, that is, I1 = 0. At this time, turn off Q4, and the current on L2 flows through the diode on Q3. At this time, turn on Q1, and I1 slowly rises. Q1 is zero-current conduction, and the current I3 on L2 will gradually be pulled to 0 current. When Q4 is off and Q2 is on, at this time, as known from the above item 1, the current on L2 is 0, that is, I3 = 0. At this time, turn off Q2, and the current on L1 flows through the diode on Q1. At this time, turn on Q3, and I3 slowly rises. Q3 is zero-current conduction, and the current I1 on L1 will gradually be pulled to 0 current.

[0107] In the negative half-cycle of the AC power supply, the initial states of Q2, Q4, and Q5 are off states.

[0108] When Q1 is turned off and Q3 is turned on, the current I1 on L1 will gradually decrease to 0, the current I2' on L2 is 0. After turning off Q3 and then turning on Q2, the current on L2 starts to flow through the diode on Q3. By turning on Q2, zero-current turn-on of Q2 is achieved, and the current I4' flowing through Q4 via the first inductor is zero. When Q4 is turned off and Q2 is turned on, the current I3 on the second inductor L2 will gradually decrease to 0, and the current I4' flowing through Q4 via the first inductor is zero. After turning off Q2, the current on L1 starts to flow through the diode on Q1, and by turning on Q4, zero-current turn-on of Q4 is achieved. As Q4 is turned on, the current I3 on L2 will gradually be pulled to 0 current.

[0109] Further, when controlling Q5 to be turned on, zero-voltage turn-off control is achieved. The method includes the following steps:

[0110] When Q1, Q2, and Q3 are in the off state and Q4 is in the on state, then turn on Q1. At this time, the voltages at both ends of Q4 are both 0, and the voltage difference between the two ends is 0. Turn on Q5 and turn off Q4. The voltage at both ends of capacitor 2 rises slowly. Q4 is turned off with zero voltage. After Q4 is completely turned off, turn off Q5. When Q2, Q3, and Q4 are in the off state and Q1 is in the on state, turn on Q4. At this time, the voltages at both ends of Q1 are both Vdc, and the voltage difference between the two ends is 0. Turn off Q1. The voltage at both ends of capacitor 1 drops slowly. At this time, Q1 is turned off with zero voltage.

[0111] When Q1, Q2, and Q4 are in the off state and Q3 is in the on state, turn on Q2. The voltages at both ends of Q3 are both Vdc, and the voltage difference between the two ends is 0. Turn off Q3. The voltage at both ends of capacitor 2 drops slowly. At this time, Q3 is turned off with zero voltage. When Q1, Q3, and Q4 are in the off state and Q2 is in the on state, turn on Q3. At this time, the voltages at both ends of Q2 are both 0, and the voltage difference between the two ends is 0. Turn on Q5 and turn off Q2. The voltage at both ends of capacitor 1 drops slowly. Q2 is turned off with zero voltage. After Q2 is completely turned off, turn off Q5.

[0112] The above 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 belongs, 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 control method for a soft switch bridge arm circuit, wherein the bridge arm circuit is a single bridge arm circuit, located between a power supply end and a load end; the single bridge arm circuit comprises a first bridge arm and a second bridge arm, the upper bridge arm and the lower bridge arm of the first bridge arm are respectively provided with a first switch device and a second switch device, the upper bridge arm and the lower bridge arm of the second bridge arm are respectively provided with a third switch device and a fourth switch device, the four switch devices are connected to a control module, characterized in that: The midpoint of the first bridge arm is connected to the first inductor, the midpoint of the second bridge arm is connected to the second inductor, the first inductor is connected to the second inductor, and the common connection point of the first inductor and the second inductor is connected to the power supply end, and the power supply end is provided with an energy transfer inductor; A first capacitor and a fifth switch device connected in series are provided between the midpoint of the first bridge arm and the midpoint of the second bridge arm, and the fifth switch device is connected to the control module; The method comprises the following steps: Controlling the fifth switch device to turn off, controlling the switching timing of the switch devices in each bridge arm, so as to adjust the current change of the first inductor and the second inductor, thereby delaying the rising speed of the current on the corresponding inductor, turning on the switch device at zero current, and realizing zero current conduction; The fifth switch device is controlled to be turned on, and the switching timing of the switch devices in each bridge arm is controlled to charge and discharge the first capacitor. Through the charging and discharging process of the first capacitor, the switch device on the zero voltage side of the first capacitor is turned off to achieve zero voltage shutdown.

2. The control method of the soft switching bridge arm circuit according to claim 1, characterized in that: When the fifth switch device is controlled to be turned off, the method comprises the following steps: In the negative half cycle of the AC power supply, when the first switch device, the third switch device, and the fifth switch device are in the off state in the initial state: When the second switch device is turned off and the fourth switch device is turned on, the current I1 on the first inductor is zero, and after the fourth switch device is turned off, the first switch device is turned on to achieve zero current conduction of the first switch device, and the current I3 flowing through the second inductor and the third switch device is zero; When the fourth switch device is turned off and the second switch device is turned on, the current I3 flowing through the third switch device via the second inductor is zero, and the third switch device is turned on after the second switch device is turned off, so that the third switch device is turned on with zero current; In the negative half cycle of the AC power supply, when the second switch device, the fourth switch device, and the fifth switch device are in the off state in the initial state: When the first switch device is turned off and the third switch device is turned on, the current I2' on the second inductor is zero. After the third switch device is turned off, the second switch device is turned on to achieve zero current conduction of the second switch device. The current I4' flowing through the first inductor and the fourth switch device is zero. When the fourth switch device is turned off and the second switch device is turned on, the current I4' flowing through the fourth switch device via the first inductor is zero, and the fourth switch device is turned on after the second switch device is turned off, so that the fourth switch device is turned on with zero current; When the fifth switch device is controlled to be turned on, the method comprises the following steps: When the first switch device, the second switch device, and the third switch device are in the off state and the fourth switch device is in the on state, the first switch device is turned on again, at which time the voltages at both ends of the fourth switch device are both zero, and the voltage difference at both ends is zero, the fifth switch device is turned on, and the fourth switch device is turned off, the voltage at one end of the first capacitor close to the midpoint of the second bridge arm rises slowly, and the fourth switch device is turned off with zero voltage; When the second switch device, the third switch device, and the fourth switch device are in the off state, and the first switch device is in the on state, the fourth switch device is turned on, at which time the voltages at both ends of the first switch device are both rectified DC voltages, and the voltage difference between the two ends is zero, and the first switch device is turned off, and the voltage at one end of the first capacitor close to the midpoint of the first bridge arm slowly decreases, and at this time the first switch device is turned off with zero voltage; When the first switch device, the second switch device, and the fourth switch device are in the off state and the third switch device is in the on state, the second switch device is turned on, the voltages at both ends of the third switch device are both rectified DC voltages, and the voltage difference between the two ends is zero. When the third switch device is turned off, the voltage at one end of the first capacitor close to the midpoint of the second bridge arm slowly decreases, and at this time, the third switch device is turned off with zero voltage; When the first switch device, the third switch device, and the fourth switch device are in the off state and the second switch device is in the on state, the third switch device is turned on, at which time the voltages at both ends of the second switch device are zero and the voltage difference between the two ends is zero, the fifth switch device is turned on, and the second switch device is turned off, the voltage at one end of the first capacitor close to the midpoint of the first bridge arm slowly decreases, and the second switch device is turned off with zero voltage.

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