Soft-switching power converter

Abstract

A soft switching power converter includes a main switch, a freewheeling switch, and an inductive coupling unit. The main switch is a controllable switch. The freewheeling switch is coupled to the main switch. The inductive coupling unit is coupled to the main switch and the freewheeling switch. The inductive coupling unit includes a first inductor, a second inductor coupled to the first inductor, and an auxiliary switch unit. The auxiliary switch unit is coupled to the second inductor to form a closed loop. The main switch and the freewheeling switch are alternately turned on and turned off. The auxiliary switch unit is controlled to start to be turned on before the main switch is turned on to provide at least one current path.

Description

Technical Field

[0001] This invention relates to a flexible power converter, and more particularly to a flexible power converter with an inductive coupling unit to achieve zero-voltage or zero-current operation. Background Technology

[0002] Please see Figure 1 and Figure 2 The figures shown are circuit diagrams of an existing buck DC-DC converter and an existing boost DC-DC converter, respectively. Because... Figure 1 and Figure 2 The converter shown has a simple topology and easy modulation methods, and is therefore widely used. However, when operating in continuous conduction mode (CCM), the switching elements undergo hard switching between on and off states. For example... Figure 3 As shown, it is Figure 1 The waveform shown is that of an existing buck converter operating in continuous conduction mode. When operating in continuous conduction mode, there are switching losses during both on and off states, and the switch experiences high switching stress. Therefore, to mitigate these issues, soft switching circuits are typically used, or adjustments are made to the operating mode, such as changing from continuous conduction mode to discontinuous conduction mode (DCM), or as... Figure 4 As shown, it is changed to critical conduction mode (CRM) in order to turn on the switch when the current is zero.

[0003] Under hard switching conditions, the switching losses of the switching elements and the reverse recovery loss of the diodes have a significant impact on efficiency. This also limits the switching frequency, preventing an increase in power density. To address this issue, critical conduction modes (such as...) are used. Figure 4 As shown in the diagram, this method can improve the switching losses caused by the switch during turn-on. However, its disadvantages include the need to adjust the switching frequency according to the load, making control more difficult. Furthermore, it results in greater input current variation compared to continuous conduction mode, placing higher demands on the preceding and following stage filters. The effective current value and turn-off current of the switch are also larger, leading to higher voltage and current stress on the switch. Therefore, this control method is not suitable for high-power applications. In other words, for applications requiring high power, continuous conduction mode remains the better choice.

[0004] In recent years, many flexible circuits based on continuous current mode have been proposed. For example... Figure 5 and Figure 6 The figures shown are circuit diagrams for existing zero-voltage switching buck converters and boost converters, respectively. Their principle is to utilize an external capacitor Cs, inductor Ls, and switch Ss to create a current source across the inductor Ls. This current source conducts the reverse diode before the main switch is turned on, thereby achieving zero-voltage switching and aiming to minimize switching losses. However, these circuit architectures all require additional switches, inductors, and capacitors. Therefore, the increase in passive components significantly impacts circuit size and increases circuit complexity and cost.

[0005] Therefore, how to design a flexible power converter, especially a flexible power converter with an inductive coupling unit to achieve zero voltage or zero current operation, and solve the problems and technical bottlenecks of the prior art, is an important research topic of the inventors of this disclosure. Summary of the Invention

[0006] One objective of this invention is to provide a flexible power converter that solves the problems of the prior art.

[0007] To achieve the aforementioned objectives, the flexible power converter proposed in this invention includes a main switch, a power release switch, and an inductive coupling unit. The main switch is a controllable switch. The power release switch is coupled to the main switch. The inductive coupling unit is coupled to both the main switch and the power release switch. The inductive coupling unit includes a first inductor, a second inductor, and an auxiliary switching unit. The second inductor is coupled to the first inductor. The auxiliary switching unit is coupled to the second inductor to form a closed loop. The main switch and the power release switch are alternately turned on and off, and the auxiliary switching unit is controlled to turn on before the main switch is turned on, thereby providing at least one current path.

[0008] By using the proposed inductive coupling unit, a zero-voltage or zero-current soft-switching function can be achieved simply by winding a coupling coil on the main inductor of a traditional power converter or by using a tap design on the main inductor, in conjunction with an auxiliary switching unit. This can significantly reduce circuit size, improve efficiency and power density, and simplify the design of the switch drive circuit.

[0009] Another object of the present invention is to provide a flexible power converter that solves the problems of the prior art.

[0010] To achieve the aforementioned objectives, the flexible power converter proposed in this invention includes a first switch, a second switch, and an inductive coupling unit. The second switch is coupled to the first switch at a common node. The inductive coupling unit has a first terminal and a second terminal, the first terminal being coupled to the common node. The inductive coupling unit includes a first inductor, a second inductor, and an auxiliary switching unit. The second inductor is coupled to the first inductor. The auxiliary switching unit is coupled to the second inductor to form a closed loop. During one cycle, the first switch and the second switch alternately turn on and off, and the auxiliary switching unit is controlled to turn on before the first switch turns on, so as to provide at least one current path.

[0011] By using the proposed inductive coupling unit, a zero-voltage or zero-current soft-switching function can be achieved simply by winding a coupling coil on the main inductor of a traditional power converter or by using a tap design on the main inductor, in conjunction with an auxiliary switching unit. This can significantly reduce circuit size, improve efficiency and power density, and simplify the design of the switch drive circuit.

[0012] To gain a deeper understanding of the techniques, means, and effects employed by this invention to achieve its intended purpose, please refer to the following detailed description and accompanying drawings. It is believed that the purpose, features, and characteristics of this invention can be understood in a thorough and specific manner from these drawings. However, the drawings are provided for reference and illustration only and are not intended to limit the scope of this invention. Attached Figure Description

[0013] Figure 1 : This is a circuit diagram of an existing step-down DC-DC converter.

[0014] Figure 2 : This is a circuit diagram of an existing boost DC-DC converter.

[0015] Figure 3 : The waveform of an existing buck converter operating in continuous conduction mode.

[0016] Figure 4 : The waveform of an existing buck converter operating in critical conduction mode.

[0017] Figure 5 : Circuit diagram of an existing zero-voltage switching buck converter.

[0018] Figure 6 : Circuit diagram of an existing zero-voltage switching boost converter.

[0019] Figure 7A : This is a circuit diagram of the first embodiment of the inductive coupling unit of the present invention.

[0020] Figure 7B : for correspondence Figure 7A A schematic diagram of the circuit components.

[0021] Figure 8A : This is a circuit diagram of a second embodiment of the inductive coupling unit of the present invention.

[0022] Figure 8B : for correspondence Figure 8A A schematic diagram of the circuit components.

[0023] Figure 9A : This is a circuit diagram of the third embodiment of the inductive coupling unit of the present invention.

[0024] Figure 9B : for correspondence Figure 9A A schematic diagram of the circuit components.

[0025] Figure 10 For use with step-down converters Figure 7A The circuit diagram of the inductive coupling unit is shown.

[0026] Figure 11A : for correspondence Figure 10 Waveform diagram of zero-voltage switching control.

[0027] Figure 11B : for correspondence Figure 10 Waveform diagram of zero-current switching control.

[0028] Figure 12 :for Figure 11A A schematic diagram of the current path from time t0 to time t1.

[0029] Figure 13A , Figure 13B :for Figure 11A A schematic diagram of the current path from time t1 to time t2.

[0030] Figure 14 :for Figure 11A A schematic diagram of the current path from time t2 to time t3.

[0031] Figure 15A , Figure 15B :for Figure 11A A schematic diagram of the current path from time t3 to time t4.

[0032] Figure 16 :for Figure 11A A schematic diagram of the current path from time t4 to time t5.

[0033] Figure 17 :for Figure 11B A schematic diagram of the current path from time t0 to time t1.

[0034] Figure 18 :for Figure 11B A schematic diagram of the current path from time t1 to time t2.

[0035] Figure 19 :for Figure 11B A schematic diagram of the current path from time t2 to time t3.

[0036] Figure 20 :for Figure 11B A schematic diagram of the current path from time t3 to time t4.

[0037] Figure 21 :for Figure 11B A schematic diagram of the current path from time t4 to time t5.

[0038] Figure 22 : This is a circuit diagram of another embodiment of the auxiliary switching unit of the present invention.

[0039] Figure 23 : This is a circuit diagram of another embodiment of the auxiliary switching unit of the present invention.

[0040] Figure 24 For use with full-bridge converters Figure 7A The circuit diagram of the inductive coupling unit is shown.

[0041] Figure 25 For use with half-bridge converters Figure 7A The circuit diagram of the inductive coupling unit is shown.

[0042] Figure 26 For use with T-type converters Figure 7A The circuit diagram of the inductive coupling unit is shown.

[0043] Figure 27 For use with multi-stage converters Figure 7A The circuit diagram of the inductive coupling unit is shown.

[0044] Figure 28 For use in single-bus boost power factor correction circuits Figure 7A The circuit diagram of the inductive coupling unit is shown.

[0045] Figure 29 For use in dual-bus boost power factor correction circuits Figure 7A The circuit diagram of the inductive coupling unit is shown.

[0046] Figure 30 For use in single-bus totem-pole power factor correction circuits Figure 7A The circuit diagram of the inductive coupling unit is shown.

[0047] Figure 31 For use in dual-bus bridgeless power factor correction circuits Figure 7A The circuit diagram of the inductive coupling unit is shown.

[0048] Explanation of reference numerals in the attached figures:

[0049] 10: Inductive coupling unit

[0050] 11: Main Inductor

[0051] 12: Auxiliary inductor

[0052] 13: Auxiliary switching unit

[0053] Lm: Magnetizing inductance

[0054] Ls: Leakage inductance

[0055] A, B, C, D: Coupling terminals

[0056] S1: Main switch

[0057] S2: Energy release switch

[0058] SA1: First transistor switch

[0059] SA2: Second transistor switch

[0060] C1, C2: Capacitors

[0061] SA: Transistor switch

[0062] D1: First diode

[0063] D2: Second diode

[0064] D3: Third diode

[0065] D4: Fourth diode

[0066] Cs: Capacitor

[0067] Ls: Inductance

[0068] Ss: Switch

[0069] i Lm Magnetizing inductor current

[0070] i Ls Leakage inductance current

[0071] i S1 i S2 Current Detailed Implementation

[0072] The technical content and detailed description of the present invention are explained below with reference to the accompanying drawings.

[0073] The core technology of the flexible power converter proposed in this invention lies in using an inductive coupling unit to achieve zero-voltage or zero-current operation. The inductive coupling unit includes a first inductor, a second inductor, and an auxiliary switching unit. The second inductor couples to the first inductor, and the auxiliary switching unit is coupled to the second inductor to form a closed loop.

[0074] Please see Figure 7A and Figure 7B The figures shown are circuit diagrams of the first embodiment of the inductive coupling unit 10 of the present invention and their corresponding circuit diagrams. Figure 7A A schematic diagram of the circuit elements is provided. In this embodiment, the inductive coupling unit 10 includes a coupling inductor composed of a main inductor 11 (or illustrated as a magnetizing inductor Lm) and an auxiliary inductor 12 (or illustrated as a leakage inductance Ls), as well as an auxiliary switching unit 13. The coupling inductor can be considered as a coupling transformer, which achieves coupling by winding an auxiliary coil (i.e., auxiliary inductor 12) on the main inductor 11 (i.e., by an iron core and a main coil wound on it). The turns ratio of the main inductor 11 to the auxiliary inductor 12 is 1:N. Furthermore, the auxiliary switching unit 13 includes at least one auxiliary switch that is a controllable switch, providing at least one current path (described in detail later).

[0075] like Figure 7A In the illustrated embodiment, the first inductor is the main inductor 11, which provides a first coupling terminal A and a second coupling terminal B, while the second inductor is the auxiliary inductor 12, which provides coupling terminals C and D. The first coupling terminal A and the second coupling terminal B of the first inductor can be used to couple to the two ends of an inductor in a conventional power converter, replacing the conventional inductor. An auxiliary switch unit 13 is coupled between the coupling terminals C and D of the auxiliary inductor 12 to form the closed loop. Thus, in DC or AC circuit applications, the coupled inductor replaces the external inductor element with leakage inductance, and the capacitor element shares the capacitance connected to the inductor terminals. Therefore, this circuit does not require additional inductors and capacitors. Consequently, the absence of additional passive components significantly reduces circuit size, improves efficiency and power density, and the use of coupling provides electrical isolation, further simplifying the design of the auxiliary switch's drive circuit.

[0076] like Figure 7AIn the illustrated embodiment, the selection of the auxiliary switching unit 13 can be based on the type or application of the power converter. If the inductor coupling unit 10 is bidirectional current-operated, for example, in a bidirectional power converter, where the current flowing through the inductor has two directions, then the auxiliary switching unit 13 may include two controllable auxiliary switches, namely a first transistor switch SA1 and a second transistor switch SA2. In this embodiment, the first transistor switch SA1 and the second transistor switch SA2 may be composed of an insulated gate bipolar transistor (IGBT) in parallel with a diode, or a metal-oxide-semiconductor field-effect transistor (MOSFET), but are not limited thereto. The emitter of the second transistor switch SA2 is connected in series with the emitter of the first transistor switch SA1 to form a series structure. The series structure is formed by coupling the collector of the second transistor switch SA2 to the coupling terminal C of the second inductor (auxiliary inductor 12 in this embodiment), and by coupling the collector of the first transistor switch SA1 to the coupling terminal D of the second inductor to form a closed loop. Through this closed loop, the energy stored in the inductor continues internally via the switch without being transferred to the external circuit.

[0077] Incidentally, if the inductive coupling unit 10 operates with unidirectional current, such as in a boost or buck converter, where the current flowing through the inductor is in only one direction, then one of the controllable switches in the auxiliary switching unit 13 (including the first transistor switch SA1 and the second transistor switch SA2) of this embodiment can also be replaced with a diode. That is, one is an auxiliary switch of the controllable switch, and the other is an auxiliary diode of the series auxiliary switch, without affecting the circuit operation. In this case, the auxiliary switching unit 13 provides the conduction and cutoff of a unidirectional current path. If the inductive coupling unit 10 operates with bidirectional current, then both auxiliary switches used by the auxiliary switching unit 13 must be controllable switches to form a series structure. In different directions of current operation, it provides two current paths with opposite currents under bidirectional current operation. In this case, the auxiliary switching unit 13 provides the conduction and cutoff of a bidirectional current path.

[0078] Please see Figure 8A and Figure 8B The figures shown are circuit diagrams and corresponding circuit diagrams of the second embodiment of the inductive coupling unit 10 of the present invention. Figure 8A A schematic diagram of the circuit components. Compared to Figure 7A and Figure 7BIn the first embodiment shown, the coupling terminal C of the auxiliary inductor 12 (i.e., the second inductor) is connected to the second coupling terminal B of the main inductor 11 (i.e., the first inductor) to form the architecture of the second embodiment. Similarly, the auxiliary switching unit 13 is coupled between the coupling terminals C and D of the auxiliary inductor 12 to form the closed loop. Similarly, taking the auxiliary switching unit 13 as containing two controllable switches, including the first transistor switch SA1 and the second transistor switch SA2, which are insulated gate bipolar transistors (IGBTs) in parallel diodes as an example, the emitter of the second transistor switch SA2 is series-coupled to the emitter of the first transistor switch SA1 to form a series structure. The series structure is formed by coupling the collector of the second transistor switch SA2 to the coupling terminal C of the second inductor (auxiliary inductor 12 in this embodiment), and by coupling the collector of the first transistor switch SA1 to the coupling terminal D of the second inductor to form a closed loop.

[0079] Please see Figure 9A and Figure 9B The figures shown are circuit diagrams and corresponding circuit diagrams of the third embodiment of the inductive coupling unit 10 of the present invention. Figure 9A The circuit element diagram is shown below. In this embodiment, the flexible circuit includes a main inductor 11 and an auxiliary switching unit 13. Specifically, the main coil of the main inductor 11 is coupled (connected) in a tapped manner, that is, the main inductor 11 provides a first coupling terminal A and a second coupling terminal B, wherein a part of the main inductor 11 provides the first inductance, corresponding to coupling terminals A and C, and the other part of the main inductor 11 provides the second inductance, corresponding to coupling terminals B and C. In other words, the first inductor and the second inductor are connected in series to form the main inductor 11. Therefore, the auxiliary switching unit 13 is coupled between the coupling terminals B and C of the main inductor 11 to form the closed loop. Similarly, taking the auxiliary switching unit 13 as containing two auxiliary switches that are controllable switches, including the first transistor switch SA1 and the second transistor switch SA2 which are insulated gate bipolar transistors (IGBTs), the emitter of the second transistor switch SA2 is connected in series with the emitter of the first transistor switch SA1 to form a series structure. The series structure is connected to the coupling terminal C of the main inductor 11 through the collector of the second transistor switch SA2, and to the coupling terminal B of the main inductor 11 through the collector of the first transistor switch SA1 to form a closed loop.

[0080] Please see Figure 10 and Figure 11A As shown, they are respectively used in buck converters Figure 7A The circuit diagram of the inductive coupling unit shown, and the corresponding... Figure 10 The waveform diagram for zero-voltage switching control is shown. Please also refer to... Figures 12-16 As shown, where, Figure 12 for Figure 11A A schematic diagram of the current path from time t0 to time t1. Figure 13A , Figure 13B for Figure 11A A schematic diagram of the current path from time t1 to time t2. Figure 14 for Figure 11A A schematic diagram of the current path from time t2 to time t3. Figure 15A , Figure 15B for Figure 11A A schematic diagram of the current path from time t3 to time t4, and Figure 16 for Figure 11A A schematic diagram of the current path from time t4 to time t5.

[0081] As previously stated, since the inductive coupling unit 10 is used in a buck converter, which operates with unidirectional current (meaning the inductor current is unidirectional), the resulting flexible power converter includes a controllable main switch S1, a release switch S2 (which can be a synchronous rectifier switch or a diode), and the inductive coupling unit 10. For ease of explanation, the auxiliary switching unit 13 is illustrated using two controllable switches (a first transistor switch SA1 and a second transistor switch SA2). However, as mentioned earlier, in buck converter applications, the second transistor switch SA2 can be replaced by a diode without affecting circuit operation. Furthermore, if the zero-voltage switching control of this invention is to be used, the release switch S2 must be a controllable switch (synchronous rectifier switch); if the zero-current switching control of this invention is to be used, the release switch S2 can be a synchronous rectifier switch or a diode. Incidentally, the definitions of the main switch and the energy release switch in this invention are as follows: In the case of a switching power converter, energy is stored in the inductor by controlling the conduction of at least one switch; this switch is defined as the main switch in this invention. When the main switch is not conducting, the switch through which the inductor freewheels is passed is defined as the energy release switch in this invention. Figure 10 Taking a step-down converter as an example (capacitor C1 is the input and capacitor C2 is the output), the main switch S1 is turned on to store energy in the inductor, and when the main switch S1 is turned off, the inductor freewheels through the energy release switch S2.

[0082] like Figure 11A As shown, this is a schematic diagram of the present invention operating in zero-voltage switching control, during time t0 to time t1 (corresponding to...). Figure 12 With the main switch S1 in the turned-off state, the main inductor 11 (or represented by the magnetizing inductor Lm) releases energy to the output capacitor C2 through the energy release switch S2. Therefore, the magnetizing inductor current i Lm The voltage gradually decreases. At time t1, while the energy release switch S2 is still conducting, the voltage V... gs3 The voltage level is switched to a high level to control the first transistor switch SA1 (i.e., the auxiliary switch) to turn on. At this time, if Figure 13AAs shown, the output capacitor C2 stores energy in the auxiliary inductor (or, schematically, the leakage inductance Ls) through coil coupling. Therefore, the leakage inductance current i Ls It begins to increase. Correspondingly, the magnetizing inductor current i at this time... Lm The current continuously decreases. Therefore, by turning on the auxiliary switch (i.e., the first transistor switch SA1) before the energy release switch S2 is turned off, the current in the closed loop (i.e., the leakage inductance current i) is reduced. Ls )rise.

[0083] When the leakage inductance current i Ls Rise to greater than the excitation inductor current i Lm For the sake of simplicity, the turns ratio N is assumed to be 1 when / N is used. Figure 13B As shown, the current i of the energy release switch S2 S2 The change from a negative value to a positive value means that the leakage inductance current i Ls It has been increased to a level sufficient to make the current i S2 Reverse, and able to maintain the excitation inductor current i Lm The continuation of the stream. For example... Figure 14 As shown, at time t2, i.e., at the leakage inductance current i Ls Greater than the leakage inductance current i Ls When it reaches a certain level, such as Figure 11A As shown, the energy release switch S2 is turned off. Therefore, the current i that originally flowed to the energy release switch S2... S2 The current flows to the diode in the main switch S1, and at this time the voltage across the main switch S1 is V. S1 It will drop to zero, and the leakage inductance current i Ls The voltage will also begin to drop due to the connection to the input voltage. Therefore, at time t3, turning on the main switch S1 will achieve zero-voltage switching, as shown below. Figure 15A , Figure 15B as well as Figure 16 As shown. Then, the main inductor (i.e., the magnetizing inductor Lm) is converted to an energy storage operation, therefore, the magnetizing inductor current i Lm The leakage inductance current i gradually increases, while the leakage inductance current i Ls It will then continue to decrease to zero.

[0084] Incidentally, the leakage inductance current i Ls As time t4 decreases to zero, since the second transistor switch SA2 is not turned on and its parallel diode blocks the reverse current, the leakage inductance current i LsThis avoids changing the current direction and prevents unnecessary current from being generated in the closed circuit during the conduction of the main switch S1. In other words, the second transistor switch SA2 can be replaced by a diode, and the first transistor switch SA1 conducts before the main switch S1 is turned on. This allows the auxiliary switching unit 13 to provide a unidirectional current path, enabling the main switch S1 to conduct at zero voltage. Furthermore, during zero-voltage switching control operation, because the current i... S2 It will reverse, so the energy release switch S2 must use a controllable switch (synchronous rectifier switch) and cannot use a diode.

[0085] Incidentally, if we take the application of the inductive coupling unit 10 in a boost converter as an example, it is equivalent to... Figure 10 With capacitor C2 as input and capacitor C1 as output, the roles of the aforementioned main switch S1 and release switch S2 will be interchanged, and the roles of the first transistor switch SA1 and the second transistor switch SA2 will also be interchanged, thus achieving zero-voltage switching of the main switch S2 (S2 in boost applications). Since the inductive coupling unit 10 of this invention is applicable to buck converters and boost converters with different current directions, it can also be applied to bidirectional current-operated power converters, such as full-bridge converters, half-bridge converters, T-type converters, etc. Therefore, if applied to a bidirectional current-operated power converter, both the first transistor switch SA1 and the second transistor switch SA2 must be controllable switches or designed as a full-bridge circuit architecture (described later) to ensure one is on and the other is off, providing two current paths with opposite currents under bidirectional current operation.

[0086] Please see Figure 10 and 11B As shown, they are respectively used in buck converters Figure 7A The circuit diagram of the inductive coupling unit shown, and the corresponding... Figure 10 Waveform diagram of zero-current switching control. Also, please refer to... Figures 17-21 As shown, where, Figure 17 for Figure 11B A schematic diagram of the current path from time t0 to time t1. Figure 18 for Figure 11B A schematic diagram of the current path from time t1 to time t2. Figure 19 for Figure 11B A schematic diagram of the current path from time t2 to time t3. Figure 20 for Figure 11B A schematic diagram of the current path from time t3 to time t4, and Figure 21 for Figure 11B A schematic diagram of the current path from time t4 to time t5.

[0087] Compared to the aforementioned zero-voltage switching mode, the main difference in the zero-current switching mode lies in controlling the auxiliary switch (in this embodiment, the first transistor switch SA1) of the auxiliary switching unit 13 to turn on after the energy release switch S2 is turned off. Figure 11B As shown, during time t0 to time t1 (corresponding to Figure 17 With the main switch S1 off, the main inductor (i.e., the magnetizing inductor Lm) is in an energy-releasing operation, and the magnetizing inductor current i Lm The voltage gradually decreases, and the energy release switch S2 acts as a synchronous rectifier switch. At time t1, the energy release switch S2 is turned off, and then the first transistor switch SA1 (i.e., the auxiliary switch) is turned on. At this time, as... Figure 18 As shown, the output capacitor C2 stores energy in the auxiliary inductor (or, represented by the leakage inductance Ls) through coil coupling, therefore the leakage inductance current i Ls Start increasing. For simplicity, the turns ratio N is assumed to be 1 here. When the leakage inductance current i increases... Ls The rising and decreasing excitation inductance current i Lm When the same size (e.g.) Figure 11B At time t2 (as shown), since the synchronous rectifier switch S2 is turned off (or if a diode is used instead of the synchronous rectifier switch S2, it will be reverse-biased and cut off), the leakage inductance Ls will no longer store energy. Figure 19 As shown, the magnetizing inductor current i at this time Lm It is coupled to the freewheeling on the auxiliary switch side via a coil.

[0088] At time t3, such as Figure 20 As shown, when the main switch S1 is turned on, the current i in the main switch S1 is... S1 The rise in current is limited by the leakage inductance Ls (clamping), resulting in a very slow current rise rate (i.e., small di / dt). Therefore, the main switch S1 can achieve near-zero current switching (ZCS). Incidentally, because the first transistor switch SA1 only turns on after the release switch S2 is turned off in zero-current switching mode, there is no current i as in zero-voltage switching mode. S2 Due to its reverse characteristic, in zero-current switching mode, the energy release switch S2 can be a diode, which does not affect the circuit operation. The same effect can be achieved simply by turning on the first transistor switch SA1 before the main switch S1 turns on. Incidentally, if the inductive coupling unit 10 is applied to a boost converter, the roles of the aforementioned main switch S1 and energy release switch S2 will be interchanged, and the roles of the first transistor switch SA1 and the second transistor switch SA2 will also be interchanged, thus achieving zero-current switching of the main switch S2 as well.

[0089] Please see Figure 22 The diagram shown is a circuit diagram of another embodiment of the auxiliary switching unit of the present invention. Compared to Figure 7A The auxiliary switching unit 13 shown is composed of a first transistor switch SA1 and a second transistor switch SA2 connected in series. Figure 22 The auxiliary switching unit 13 shown includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, and a transistor switch SA. Specifically, the cathode of the second diode D2 is coupled to the anode of the first diode D1 at a first common junction, and the first common junction is coupled to the coupling terminal C of the auxiliary inductor 12. The cathode of the fourth diode D4 is coupled to the anode of the third diode D3 at a second common junction, and the second common junction is coupled to the coupling terminal D of the auxiliary inductor 12. The cathode of the first diode D1 is coupled to the cathode of the third diode D3 at a third common junction; the anode of the first diode D2 is coupled to the anode of the fourth diode D4 at a fourth common junction, thereby forming a bridge circuit structure that provides two current paths with opposite currents. In this embodiment, the transistor switch SA may be an insulated gate bipolar transistor (IGBT), but this is not intended to limit the invention. The first terminal (e.g., collector) of the transistor switch SA is coupled to the third common junction, and the second terminal (e.g., emitter) of the transistor switch SA is coupled to the fourth common junction. Therefore, in this embodiment, the auxiliary switching unit 13 is coupled to the second inductor (auxiliary inductor 12 in this embodiment) to form a closed loop. Furthermore, the auxiliary switching unit 13 of this embodiment can be applied to power converters that operate with either unidirectional or bidirectional current.

[0090] Please see Figure 23 The diagram shown is a circuit diagram of another embodiment of the auxiliary switching unit of the present invention. Figure 23 The auxiliary switching unit 13 shown includes a first diode D1, a second diode D2, a first transistor switch SA1, and a second transistor switch SA2. Specifically, the cathode of the second diode D2 is coupled to the anode of the first diode D1 at a first common junction, and the first common junction is coupled to the coupling terminal C of the auxiliary inductor 12, thereby forming a bridge circuit structure and providing two current paths with opposite currents. In this embodiment, the first transistor switch SA1 and the second transistor switch SA2 may be insulated gate bipolar transistors (IGBTs), but this is not intended to limit the invention. The first terminal (e.g., emitter) of the first transistor switch SA1 is coupled to the second terminal (e.g., collector) of the second transistor switch SA2 at a second common junction, and the second common junction is coupled to the coupling terminal D of the auxiliary inductor 12. The second terminal (e.g., collector) of the first transistor switch SA1 is coupled to the cathode of the first diode D1; the first terminal (e.g., emitter) of the second transistor switch SA2 is coupled to the anode of the second diode D2. Thus, the auxiliary switching unit 13 of this embodiment is coupled to the second inductor (auxiliary inductor 12 in this embodiment) to form a closed loop. Furthermore, the auxiliary switching unit 13 of this embodiment can be applied to power converters that operate with unidirectional current or bidirectional current.

[0091] In summary, the inductive coupling unit 10 disclosed in this invention can be used not only in buck converters and boost converters, but also in full-bridge converters (such as...). Figure 24 As shown), used in half-bridge converters (such as...) Figure 25 As shown), it is used for T-type converters (such as...) Figure 26 As shown), it is used in multi-stage converters (such as...). Figure 27 As shown), it is used in a single-bus boost power factor correction circuit (such as...). Figure 28 As shown), it is used in a dual-bus boost power factor correction circuit (such as...). Figure 29 As shown), it is used in a single-bus totem-pole power factor correction circuit (such as...). Figure 30 (as shown) and used in dual-bus bridgeless power factor correction circuits (such as Figure 31 (As shown). However, the application of the inductive coupling unit 10 disclosed in this invention is not limited to the above-mentioned circuits and devices. The inductive coupling unit 10 disclosed in this invention can be used in any circuit topology that requires the use of inductive elements for zero-voltage and / or zero-current switching.

[0092] It is worth mentioning that, with Figure 25 Taking the half-bridge converter (half-bridge DC-to-AC power converter) shown as an example, it has a first switch S1, a second switch S2, and an inductive coupling unit 10. The second switch S2 is coupled to the first switch S1 at a common connection node. The first end of the inductive coupling unit 10 is coupled to the common connection node. During one cycle, the first switch S1 and the second switch S2 alternately turn on and off. During the positive half-cycle, the principle and operation of the half-bridge converter are similar. Figure 10 The illustrated embodiments, and their specific operations, can be found in the corresponding examples. Figure 10 The contents of the instruction manual will not be repeated here. During the negative half-cycle, as mentioned above, the roles of the first switch S1 and the second switch S2 will be interchanged, and the roles of the first transistor switch SA1 and the second transistor switch SA2 included in the auxiliary switching unit will also be interchanged, which can also achieve zero-voltage or zero-current operation.

[0093] like Figure 26 The T-type converter shown is Figure 25 The illustrated half-bridge converter further includes a third switch S3 and a fourth switch S4. The fourth switch S4 is connected in series with the third switch S3 to form a series structure, and the series structure is coupled between the first and second terminals of the inductive coupling unit 10. Similarly, by alternately turning the first switch S1 and the second switch S2 on and off within one cycle, and correspondingly controlling the on and off of the first transistor switch SA1 and the second transistor switch SA2, zero-voltage or zero-current operation can also be achieved.

[0094] In summary, the present invention has the following features and advantages:

[0095] 1. The inductive coupling unit of the present invention only needs to wind a coupling coil on the main inductor or use the tap design of the main inductor, and then cooperate with the auxiliary switching unit to achieve the zero voltage or zero current soft switching function.

[0096] 2. In DC or AC circuit applications, the coupled inductor replaces the external inductor element with leakage inductance, and the capacitor element shares the capacitor connected to the inductor terminal. Without additional passive components, the circuit size can be greatly reduced, and the efficiency and power density can be improved. In addition, this circuit uses a coupling method and has the function of electrical isolation, which can further simplify the design of the switch drive circuit.

[0097] 3. The inductive coupling unit of the present invention can be flexibly adapted to the application of the required circuit topology to achieve the flexible cutting function.

[0098] The above description is merely a detailed explanation and accompanying drawings of preferred embodiments of the present invention, and the features of the present invention are not limited thereto, nor are they intended to limit the present invention. The full scope of the present invention should be determined by the claims. All embodiments that conform to the concept of the claims of the present invention and similar variations thereof should be included in the scope of the present invention. Any variations or modifications that can be easily conceived by those skilled in the art within the field of the present invention can be covered by the claims disclosed herein.

Claims

1. A flexible power converter, comprising: One main switch, which is a controllable switch; A release switch, coupled to the main switch; and An inductive coupling unit, coupled to the main switch and the energy release switch, includes: One main inductor; An auxiliary inductor is wound around the main inductor; and An auxiliary switching unit is coupled to the auxiliary inductor to form a closed loop; A third switch; A fourth switch is connected in series with the third switch to form a series structure, which is coupled between the first and second terminals of the inductive coupling unit. wherein The inductive coupling unit also includes a circular magnet, on which the main inductor is wound and the auxiliary inductor is wound. The main inductor has a first coupling terminal coupled to the main switch and a second coupling terminal coupled to an output capacitor of the flexible power converter. The auxiliary inductor has a third coupling terminal and a fourth coupling terminal. The third coupling terminal is coupled to one end of the auxiliary switching unit, and the fourth coupling terminal is coupled to the other end of the auxiliary switching unit. The third coupling terminal of the auxiliary inductor is further coupled to the second coupling terminal of the main inductor. The main switch and the energy release switch are alternately turned on and off. Before the main switch is turned on, the auxiliary switch unit is controlled to start conducting to provide at least one current path. The turns ratio between the main inductor and the auxiliary inductor is 1:N.

2. The soft-chopped power converter of claim 1, wherein, When the leakage current of the auxiliary inductor increases to more than 1 / N of the magnetizing current of the main inductor, the auxiliary switching unit starts to conduct before the energy release switch is closed, so that the main switch operates in a zero-voltage switching mode.

3. The soft-chopped power converter of claim 1, wherein, When the leakage current of the auxiliary inductor rises to the same level as the magnetizing current of the main inductor, the auxiliary switching unit begins to conduct after the energy release switch is closed, so that the main switch operates in a zero-current switching mode.

4. The soft-chopped power converter of claim 1, wherein, The inductive coupling unit operates with unidirectional current, and the auxiliary switching unit includes: An auxiliary switch, which is a controllable switch; and An auxiliary diode is connected in series with the auxiliary switch to form a series structure, providing the at least one current path.

5. The soft-chopped power converter of claim 1, wherein, The inductive coupling unit is bidirectional current-operated, and the auxiliary switching unit includes: A first transistor switch; and A second transistor switch is connected in series with the first transistor switch to form a series structure, providing two current paths with opposite currents; The series structure is coupled to the two ends of the auxiliary inductor.

6. The soft-chopped power converter of claim 1, wherein, The inductive coupling unit is unidirectional or bidirectional current-operated, and the auxiliary switching unit includes: A first diode having a first terminal and a second terminal; A second diode having a first terminal and a second terminal; A third diode has a first terminal and a second terminal; A fourth diode, having a first terminal and a second terminal; and An auxiliary switch, which is a transistor switch, has a first terminal and a second terminal; Wherein, the first terminal of the transistor switch is connected to the first terminal of the first diode and the first terminal of the third diode; the second terminal of the transistor switch is connected to the first terminal of the second diode and the first terminal of the fourth diode; the second terminal of the first diode is connected to the second terminal of the second diode, and the second terminal of the third diode is connected to the second terminal of the fourth diode, so as to form a bridge structure and provide two current paths with opposite currents; The bridge structure is coupled to both ends of the auxiliary inductor.

7. The soft-chopped power converter of claim 1, wherein, The inductive coupling unit is unidirectional or bidirectional current-operated, and the auxiliary switching unit includes: A first diode having a first terminal and a second terminal; A second diode having a first terminal and a second terminal; and Two auxiliary switches, including: A first transistor switch having a first terminal and a second terminal; and A second transistor switch having a first terminal and a second terminal; Wherein, the first terminal of the first diode is connected to the first terminal of the first transistor switch; The first terminal of the second diode is connected to the first terminal of the second transistor switch; the second terminal of the first diode is connected to the second terminal of the second diode, and the second terminal of the first transistor switch is connected to the second terminal of the second transistor switch, to form a bridge structure that provides two current paths with opposite currents. The bridge structure is coupled to both ends of the auxiliary inductor.

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