TWI742997B - Soft-switching power converter - Google Patents

Abstract

A soft-switching power converter includes a main switch, an energy-releasing switch, and an inductive coupled unit. The main switch is a controllable switch. The energy-releasing switch is coupled to the main switch. The inductive coupled unit is coupled to the main switch and the energy-releasing switch. The inductive coupled unit includes a first inductance, a second inductance coupled to the first inductance, and an auxiliary switch unit. The auxiliary switch unit is coupled to the second inductance to form a closed loop. The main switch and the energy-releasing switch are alternately turned on and turned off. The auxiliary switch unit is controlled to start turning on before the main switch is turned on so as to provide at least one current path.

Description

Soft cut power converter

The present invention relates to a soft-cut power converter, in particular to a soft-cut power converter with an inductive coupling unit to achieve zero voltage or zero current operation.

Please refer to FIG. 1 and FIG. 2, which are circuit diagrams of an existing step-down DC-DC converter and an existing step-up DC-DC converter, respectively. Because the converter shown in Fig. 1 and Fig. 2 has simple topology and easy modulation method, it is widely used. However, when it is operated in a continuous conduction mode (CCM), the switching element is hard switching when it is turned on and off. As shown in FIG. 3, it is the waveform of the conventional step-down converter shown in FIG. 1 operating in the continuous conduction mode. When operating in continuous conduction mode, there will be switching loss when the switch is turned on and when the switch is turned off, and the switch needs to withstand higher switching stress. Therefore, in order to improve these problems, usually through the use of soft switching (soft switching) circuit, or make adjustments from the operating mode, such as changing from continuous conduction mode to discontinuous conduction mode (DCM), as shown in Figure 4. As shown, change to the critical conduction mode (CRM), in order to turn on the switch again when the current is zero.

Operating under hard switching, the switching loss of the switching element and the reverse recovery loss of the diode have a great impact on the efficiency. The switch is also restricted by this and cannot increase the switching frequency, so that the power density cannot be increased. To solve this problem, use the critical conduction mode (as shown in Figure 4), which can improve the switching loss caused by the switch at the moment of conduction, but the disadvantage is that the switching frequency needs to be adjusted with the load, and the control is more difficult, and it is more difficult to control than the input in continuous conduction mode. The current changes greatly, and the requirements for the front and rear filters are higher, and the effective current value of the switch and the turn-off current are also larger, resulting in higher voltage and current stress of the switch. However, this control method is not suitable for higher power applications. In other words, if higher power applications are required, the continuous conduction mode is still a better choice.

In recent years, many soft-cut circuits based on continuous current mode have been proposed. As shown in FIG. 5 and FIG. 6, the circuit diagrams of the conventional buck converter and boost converter with zero voltage switching are respectively. The principle is to use an external capacitor Cs, an inductor Ls and a switch Ss to create a current source on the inductor Ls to turn on the reverse diode before the main switch is turned on, so as to achieve zero voltage switching, in order to achieve a turn-on switching loss close to For zero purpose. However, these circuit architectures require additional switches, inductors, and capacitors. Therefore, the increase of passive components has a great impact on the circuit volume and increases circuit complexity and cost.

Therefore, how to design a soft-cut power converter, especially a soft-cut power converter with an inductive coupling unit to achieve zero-voltage or zero-current operation, to solve the problems and technical bottlenecks in the prior art, is this case An important subject studied by the inventor.

One purpose of the present invention is to provide a soft-cut power converter to solve the problems of the prior art.

In order to achieve the aforementioned purpose, the soft-cut power converter proposed in the present invention includes a main switch, an energy release switch, and an inductive coupling unit. The main switch is a controllable switch. The release switch is coupled to the main switch. The inductive coupling unit is coupled to the main switch and the release switch. The inductive coupling unit includes a first inductor, a second inductor, and an auxiliary switch unit. The second inductance is coupled to the first inductance. The auxiliary switch unit is coupled to the second inductor to form a closed loop. Wherein, the main switch and the discharging switch are turned on and off alternately, and the auxiliary switch unit is controlled to be turned on before the main switch is turned on to provide at least one current path.

With the proposed inductive coupling unit, it is only necessary to wind the coupling coil on the main inductor of the traditional power converter or through the tap design of the main inductor, and cooperate with the auxiliary switch unit to achieve the zero voltage or zero current soft cut function. And can greatly reduce the circuit volume, improve efficiency, power density and simplify the design of the drive circuit of the switch.

Another object of the present invention is to provide a soft-cut power converter to solve the problems of the prior art.

In order to achieve the aforementioned purpose, the soft-cut power converter provided by the present invention includes a first switch, a second switch, and an inductive coupling unit. The second switch is coupled to the first switch at the common connection node. The inductive coupling unit has a first end and a second end, and the first end is coupled to the common node. The inductive coupling unit includes a first inductor, a second inductor, and an auxiliary switch unit. The second inductance is coupled to the first inductance. The auxiliary switch unit is coupled to the second inductor to form a closed loop. During a period of time, the first switch and the second switch are turned on and off alternately, and the auxiliary switch unit is controlled to be turned on before the first switch is turned on to provide at least one current path.

With the proposed inductive coupling unit, it is only necessary to wind the coupling coil on the main inductor of the traditional power converter or through the tap design of the main inductor, and cooperate with the auxiliary switch unit to achieve the zero voltage or zero current soft cut function. And can greatly reduce the circuit volume, improve efficiency, power density and simplify the design of the drive circuit of the switch.

In order to have a better understanding of the technology, means and effects adopted by the present invention to achieve the intended purpose, please refer to the following detailed description and drawings of the present invention. I believe that the purpose, features and characteristics of the present invention can be obtained from this in depth and For specific understanding, however, the accompanying drawings are only provided for reference and illustration, and are not intended to limit the present invention.

The technical content and detailed description of the present invention are described below in conjunction with the drawings.

The core technology of the soft-cut power converter proposed in the present invention is to use an inductive coupling unit to achieve zero-voltage or zero-current operation of the soft-cut power converter. The inductive coupling unit includes a first inductor, a second inductor, and an auxiliary switch unit. Wherein, the second inductor is coupled to the first inductor, and the auxiliary switch unit is coupled to the second inductor to form a closed loop.

Please refer to FIG. 7A and FIG. 7B, which are respectively the circuit diagram of the first embodiment of the inductive coupling unit 10 of the present invention and the schematic diagram of the circuit elements corresponding to FIG. 7A. In this embodiment, the inductive coupling unit 10 includes a coupling inductance composed of a main inductance 11 (or indicated by a magnetizing inductance Lm) and an auxiliary inductance 12 (or indicated by a leakage inductance Ls), and an auxiliary switch unit 13. The coupling inductor can be regarded as the principle of the coupling transformer, which is connected to the main inductor 11 (that is, realized by the iron core and the main coil wound on it) and then an auxiliary coil (ie, the auxiliary inductor 12) is wound to achieve the coupling effect. Among them, the coil turns ratio of the main inductor 11 and the auxiliary inductor 12 is 1:N. Furthermore, the auxiliary switch unit 13 includes at least one auxiliary switch that is a controllable switch, and provides at least one current path (detailed later).

In the embodiment shown in FIG. 7A, the first inductor is the main inductor 11, which provides the first coupling terminal A and the second coupling terminal B, and the second inductor is the auxiliary inductor 12, which provides the coupling terminal C , D, where the first coupling end A and the second coupling end B of the first inductor can be used to couple the two ends of the conventional power converter for connecting the inductor to replace the conventional inductor. The auxiliary switch unit 13 is coupled between the coupling ends C and D of the auxiliary inductor 12 to form the closed loop. As a result, in the application of DC or AC circuits, the coupled inductor replaces the external inductance element through the leakage inductance, and the capacitive element shares the capacitance connected to the end of the inductor. Therefore, this circuit does not require additional inductors and capacitors. Therefore, without additional passive components, the circuit volume can be greatly reduced, and the efficiency and power density can be improved. The circuit uses a coupling method and has the function of electrical isolation, which further simplifies the drive circuit design of the auxiliary switch.

As shown in the embodiment shown in FIG. 7A, the selection of the auxiliary switch unit 13 can be selected according to the type or application of the power converter. If the inductive coupling unit 10 is bidirectional current operation, for example, it is applied to a bidirectional power converter, and the inductor flows through the inductor. There are two directions of current on the auxiliary switch unit 13 can include two auxiliary switches that are controllable switches, including a first transistor switch SA ₁ and a second transistor switch SA ₂ . In this embodiment, the first transistor switch SA ₁ and the second transistor switch SA ₂ may be composed of insulated gate bipolar transistors (IGBT) in parallel with diodes, or metal oxide semi-field effect transistors (MOSFET) , But not limited by this. The second transistor switch SA ₂ (the emitter) is coupled in series to the first transistor switch SA ₁ (the emitter) to form a series structure. The series structure is coupled to the coupling terminal C of the second inductor (the auxiliary inductor 12 in this embodiment) through the collector of the second transistor switch SA ₂ and is coupled to the coupling terminal C of the second inductor _{through the collector of the first transistor switch SA 1} The terminal D is coupled to form a closed loop. Through this closed loop, the energy stored in the inductor is free-wheeled internally through the switch, and will not be transferred to the external circuit.

Incidentally, if the inductive coupling unit 10 is unidirectional current operation, for example, applied to a boost or buck converter, and the current flowing through the inductor is only in one direction, the auxiliary switch unit 13 (including the first One of the controllable switches of the one transistor switch SA ₁ and the second transistor switch SA ₂ ) can also be replaced with a diode, that is, one is the auxiliary switch of the controllable switch, and the other is the auxiliary switch of the series-connected auxiliary switch. The pole body does not affect the circuit operation. At this time, the auxiliary switch unit 13 provides a single-direction current path on and off. If the inductive coupling unit 10 is operated by bidirectional current, the two auxiliary switches used by the auxiliary switch unit 13 must both be controllable switches to form a series structure. In the current operation of different directions, the current under bidirectional current operation is provided. In the opposite two current paths, at this time, the auxiliary switch unit 13 provides the on and off of the bidirectional current path.

Please refer to FIG. 8A and FIG. 8B, which are respectively the circuit diagram of the second embodiment of the inductive coupling unit 10 of the present invention and the schematic diagram of the circuit elements corresponding to FIG. 8A. Compared with the first embodiment shown in FIGS. 7A and 7B, the coupling terminal C of the auxiliary inductor 12 (ie, the second inductor) is commonly connected to the second coupling terminal B of the main inductor 11 (ie, the first inductor). To form the architecture of the second embodiment. Similarly, the auxiliary switch unit 13 is coupled between the coupling ends C and D of the auxiliary inductor 12 to form the closed loop. Similarly, the auxiliary switch unit 13 includes two auxiliary switches that are controllable switches, including a first transistor switch SA ₁ and a second transistor switch SA _{2 which} are insulated gate bipolar transistors (IGBT) connected in parallel as an example. , The second transistor switch SA ₂ (the emitter) is coupled in series to the first transistor switch SA ₁ (the emitter) to form a series structure. The series structure is coupled to the coupling terminal C of the second inductor (the auxiliary inductor 12 in this embodiment) through the collector of the second transistor switch SA ₂ and is coupled to the coupling terminal C of the second inductor _{through the collector of the first transistor switch SA 1} The terminal D is coupled to form a closed loop.

Please refer to FIG. 9A and FIG. 9B, which are respectively a circuit diagram of a third embodiment of the inductive coupling unit 10 of the present invention and a schematic diagram of circuit elements corresponding to FIG. 9A. In this embodiment, the soft cut circuit includes a main inductor 11 and an auxiliary switch unit 13. Specifically, the main coil of the main inductor 11 adopts a tapped coupling (wiring) manner, that is, the main inductor 11 provides a first coupling end A and a second coupling end B, and a part of the main inductor 11 provides the first inductance. , Corresponding to the coupling terminals A and C, another part of the main inductor 11 provides a second inductance, corresponding to the 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 switch unit 13 is coupled between the coupling ends B and C of the main inductor 11 to form the closed loop. Similarly, taking the auxiliary switch unit 13 including two auxiliary switches that are controllable switches, including the first transistor switch SA ₁ and the second transistor switch SA ₂ are insulated gate bipolar transistors (IGBT) as an example, the second transistor The (emitter of) transistor switch SA _{2 is} coupled in series to (the emitter of) the first transistor switch SA ₁ to form a series structure. The series structure is coupled to the coupling terminal C of the main inductor 11 through the collector of the second transistor switch SA ₂ and coupled to the coupling terminal B of the main inductor 11 through _{the collector of the first transistor switch SA 1} to form a closed loop.

Please refer to FIG. 10 and FIG. 11A, which are respectively a circuit diagram of a step-down converter using the inductive coupling unit shown in FIG. 7A, and a waveform diagram corresponding to the zero voltage switching control of FIG. 10. At the same time, please refer to Figures 12 to 16, where Figure 12 is a schematic diagram of the current path from time t0 to time t1 in Figure 11A, and Figure 13A and Figure 13B are schematic diagrams of the current path from time t1 to time t2 in Figure 11A Figure 14 is a schematic diagram of the current path from time t2 to time t3 in Figure 11A, Figure 15A and Figure 15B are schematic diagrams of the current path from time t3 to time t4 in Figure 11A, and Figure 16 is a schematic diagram of the current path from time t4 to time in Figure 11A Schematic diagram of the current path of t5.

As mentioned above, since the inductive coupling unit 10 is applied to a buck converter, it is a unidirectional current operation, which means that the inductor current is unidirectional. Therefore, the formed soft-cut power converter includes: The main switch S _{1 of the} controllable switch, the discharging switch S ₂ (which may be a synchronous rectifier switch or a diode), and the inductive coupling unit 10. For the convenience of description, the auxiliary switch unit 13 takes two controllable switches (the first transistor switch SA ₁ and the second transistor switch SA ₂ ) as an example. However, as mentioned above, in the application of a step-down converter, the second transistor switch SA ₂ can be replaced by a diode, which does not affect the circuit operation. Furthermore, if you want to use the zero voltage switching control of the present invention, the release switch S ₂ must use a controllable switch (synchronous rectifier switch); if you want to use the zero current switching control of the present invention, the release switch S ₂ can be Use a synchronous rectifier switch or a diode can also be used. Incidentally, the definition of the main switch and the energy-discharging switch of the present invention: If a switching power converter is used, the inductor will store energy by controlling the conduction of at least one switch, and this switch is defined as the main switch in the present invention; When the main switch is not conducting, the switch through which the inductor freewheels is defined as a release switch in the present invention. Take the step-down converter of FIG. 10 as an example (capacitor C ₁ is input and capacitor C ₂ is output). The main switch S ₁ is controlled to be turned on to store energy in the inductor, and when the main switch S _{1 is} turned off, the inductor flows freely through the energy-releasing switch S _2.

As shown in FIG. 11A, which is a schematic diagram of the present invention operating in zero-voltage switching control, from time t0 to time t1 (corresponding to FIG. 12), the main switch S ₁ is in the turned-off state, and the main inductor 11 (or magnetizing inductance Lm schematically) through a discharging switch S ₂ release energy output capacitor C _2, and therefore, the magnetizing inductor current I _Lm decreases. When the time t1 is reached, when the _{discharging switch S 2 is} still on, the voltage V gs3 transitions to a high voltage level to control the first transistor switch SA ₁ (that is, the auxiliary switch) to turn on. At this time, as shown in the figure As shown in 13A, the output capacitor C ₂ stores energy to the auxiliary inductance (or indicated by the leakage inductance Ls) through the coil coupling. Therefore, the leakage inductance current i _Ls starts to increase. Correspondingly, the magnetizing inductance current i _Lm continues to decrease at this time. Therefore, the auxiliary switch (ie, the first transistor switch SA ₁ ) is turned on before the discharging switch S _{2 is} turned off, so that the current of the closed loop (ie, the leakage inductance current i _Ls ) rises.

When the leakage inductance current i _Ls rises to greater than the magnetizing inductance current i _Lm /N, for the convenience of explanation, the turns ratio N here is assumed to be 1, as shown in Figure 13B, the current i _{S2 of the release switch S 2} will be changed by The negative value turns into a positive value, which means that the leakage inductance current i _Ls has increased enough to _{reverse the current i S2} , and the freewheeling of the magnetizing inductance current i _{Lm can be maintained.} As shown in Fig. 14, at time t2, that is, when the leakage inductance current i _{Ls is} greater than the leakage inductance current i _Ls to a certain extent, as shown in Fig. 11A _{, the discharging switch S 2 is} turned off, so the original flow to the discharging switch S current i _{S2 2} is a main flow to the body diode switch S ₁ when the main switch S cross voltage V _{S1 1} will fall to zero, and the leakage inductance current i _Ls connected to the input voltage due to reasons Will start to decline. Thus, at time t3, the main switch S ₁ is turned on, can achieve zero voltage switching, as shown in FIG. 15A, 15B and 16. Then, the main inductance (ie, the magnetizing inductance Lm) is converted to an energy storage operation. Therefore, the magnetizing inductance current i _Lm gradually increases, and the leakage inductance current i _Ls continuously decreases to zero.

Incidentally, the leakage inductance current i _Ls decreases to zero at time t4. Since the second transistor switch SA _{2 is} not turned on, and its parallel diode blocks the current in the opposite direction, the leakage inductance current i _Ls will not changing the current direction, to avoid unnecessary current in the closed loop during the main switch S ₁ is turned on. In other words, the second transistor switch SA ₂ can be replaced by only a diode, and the first transistor switch SA _{1 is} turned on before the main switch S _{1 is} turned on, so that the auxiliary switch unit 13 provides a unidirectional current path. The main switch S ₁ can be turned on at zero voltage. In addition, zero voltage switching operation control, by the current i _S2 will be reversed, so that the discharging switch S ₂ must use the controllable switch (synchronous rectifier switch), diodes can not be used.

Incidentally, if the inductive coupling unit 10 is applied to the boost converter (boost converter), for example, FIG. 10 is equivalent to the capacitance C ₂ and the input capacitance C is _{output. 1,} the main switch S ₁ and the discharging switch S _{The roles of 2} will be swapped, and the roles of the first transistor switch SA ₁ and the second transistor switch SA ₂ will also be swapped, which can also achieve zero voltage _{to the main switch S 2} (the main switch is S _{2 in boost applications)} Switch. Since the inductive coupling unit 10 of the present invention can be applied to buck converters and boost converters with different current directions, the inductive coupling unit 10 can also be applied to power converters with bidirectional current operation, such as full-bridge converters. Application of converters, half-bridge converters, T-converters...etc. Therefore, if applied to a bidirectional current-operated power converter, both the first transistor switch SA ₁ and the second transistor switch SA ₂ must use controllable switches or be designed as a full-bridge circuit architecture (described later) to achieve One is on and the other is off, providing two current paths with opposite currents under bidirectional current operation.

Please refer to FIGS. 10 and 11B, which are respectively a circuit diagram of a step-down converter using the inductive coupling unit shown in FIG. 7A, and a waveform diagram corresponding to the zero-current switching control of FIG. 10. At the same time, please refer to Figure 17 to Figure 21, where Figure 17 is a schematic diagram of the current path from time t0 to time t1 in Figure 11B, and Figure 18 is a schematic diagram of the current path from time t1 to time t2 in Figure 11B, and Figure 19 It is a schematic diagram of the current path from time t2 to time t3 in FIG. 11B, FIG. 20 is a schematic diagram of the current path from time t3 to time t4 in FIG. 11B, and FIG. 21 is a schematic diagram of the current path from time t4 to time t5 in FIG. 11B.

Compared with the aforementioned zero voltage switching mode, the difference of the zero current switching mode is mainly that the auxiliary switch of the auxiliary switch unit 13 (in this embodiment, the first transistor switch SA ₁ ) is _{controlled to turn on after the discharging switch S 2 is turned off.} As shown in Figure 11B, from time t0 to time t1 (corresponding to Figure 17), the main switch S ₁ is in the off state, so the main inductor (ie, the magnetizing inductance Lm) is a release operation, and the magnetizing inductance current i _Lm gradually decreases , The release switch S ₂ is a synchronous rectifier switch. When the time t1 is reached, the discharging switch S _{2 is} turned off, and then the first transistor switch SA ₁ (ie auxiliary switch) is turned on. At this time, as shown in Figure 18, the output capacitor C _{2 is} coupled to the auxiliary inductor ( Or as indicated by the leakage inductance Ls) energy storage, so the leakage inductance current i _Ls starts to increase. For the convenience of description, the turns ratio N here is assumed to be 1. When the increased leakage inductance current i _Ls rises to the same magnitude as the decreased magnetizing inductance current i _Lm (at time t2 as shown in Fig. 11B), Since the synchronous rectifier switch S ₂ has been turned off (or if the synchronous rectifier switch S ₂ is replaced by a diode, it is reverse biased), the leakage inductance Ls will no longer store energy, as shown in Figure 19, at this time the magnetizing inductance The current i _{Lm is} coupled to the freewheeling on the auxiliary switch side through the coil.

At time t3, as shown in Figure 20, the main switch S _{1 is} turned on, and the rise of the current i _{S1 of the main switch S 1} will be limited by the effect of the leakage inductance Ls (clamping), making the current rise very slow (ie, di/dt is small) ), so the main switch S ₁ can achieve almost zero current switching (ZCS). Incidentally, in the zero current switching mode, the first transistor switch SA _{1 is} turned on after the discharging switch S _{2 is} turned off, so there is no _{reverse characteristic of the current i S2 in the} zero voltage switching mode. Therefore, at zero In the current switching mode, the energy-releasing switch S ₂ can be a diode, which does not affect the circuit operation. It is only necessary to turn on the first transistor switch SA _{1 before the main switch S 1 is} turned on to achieve the same effect. Incidentally, if the inductive coupling unit 10 is applied to a boost converter as an example, _{the roles of the aforementioned main switch S 1} and the _{discharge switch S 2} will be reversed, and the first transistor switch SA ₁ and the second transistor The roles of the two transistor switches SA ₂ will also be exchanged, and the zero current switching _{of the main switch S 2 can also be realized.}

Please refer to FIG. 22, which is a circuit diagram of another embodiment of the auxiliary switch unit of the present invention. Compared with the auxiliary switch unit 13 shown in FIG. 7A which is composed of a first transistor switch SA ₁ and a second transistor switch SA ₂ coupled in series, the auxiliary switch unit 13 shown in FIG. 22 includes a first diode D ₁ , the second diode D ₂ , the third diode D ₃ , the fourth diode D ₄ and the transistor switch SA. Specifically, the cathode of the second diode D ₂ is coupled to the anode of the first diode D ₁ at the 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 D ₄ is coupled to the anode of the third diode D ₃ at the 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 D ₁ is coupled to the cathode of the third diode D ₃ at the third common junction; _{the anode of the second diode D 2} is coupled to the anode of the fourth diode D ₄ at the fourth common The contacts, thereby forming a bridge circuit structure, provide two current paths with opposite currents. In this embodiment, the transistor switch SA may be an insulated gate bipolar transistor (IGBT), but the present invention is not limited by this. The first terminal (such as the collector) of the transistor switch SA is coupled to the third common contact, and the second terminal (such as the emitter) of the transistor switch SA is coupled to the fourth common contact. Thereby, the auxiliary switch unit 13 of this embodiment is coupled to the second inductor (the auxiliary inductor 12 in this embodiment) to form a closed loop. In addition, the auxiliary switch unit 13 of this embodiment can be applied to a unidirectional current operation or a bidirectional current operation power converter.

Please refer to FIG. 23, which is a circuit diagram of yet another embodiment of the auxiliary switch unit of the present invention. The auxiliary switch unit 13 shown in FIG. 23 includes a first diode D ₁ , a second diode D ₂ , a first transistor switch SA ₁ and a second transistor switch SA ₂ . Specifically, the cathode of the second diode D ₂ is coupled to the anode of the first diode _{D. 1} in a first common terminal and the first common contact 12 is coupled to the auxiliary inductor connected to terminal C coupled, thereby forming The bridge circuit structure provides two current paths with opposite currents. In this embodiment, the first transistor switch SA ₁ and the second transistor switch SA ₂ may be insulated gate bipolar transistors (IGBT), but the present invention is not limited by this. The first terminal (such as the emitter) of the first transistor switch SA ₁ is coupled to the second terminal (such as the collector) of the second transistor switch SA ₂ at a second common contact, and the second common contact is coupled to the auxiliary The coupling terminal D of the inductor 12. The second end (for example, the collector) of the first transistor switch SA _{1 is coupled to the cathode of the first diode D 1} ; the first end (for example, the emitter) of the second transistor switch SA _{2 is coupled to the second diode} The anode of body D _2. Thereby, the auxiliary switch unit 13 of this embodiment is coupled to the second inductor (the auxiliary inductor 12 in this embodiment) to form a closed loop. Moreover, the auxiliary switch unit 13 of this embodiment can be applied to a unidirectional current operation or a bidirectional current operation power converter.

In summary, the inductive coupling unit 10 disclosed in the present invention can be used not only for buck converters and boost converters, but also for full-bridge converters (as shown in FIG. 24), and can also be used for half-bridge converters (as shown in FIG. 24). Used by bridge converters (as shown in Figure 25), used by T-shaped converters (as shown in Figure 26), used by multi-stage converters (as shown in Figure 27), and used by single busbars Used by boost power factor correction circuit (as shown in Figure 28), used by dual bus boost power factor correction circuit (as shown in Figure 29), used by single bus totem pole power factor correction circuit (As shown in Figure 30) and used for the dual-bus bridgeless power factor correction circuit (as shown in Figure 31). However, the application of the inductive coupling unit 10 disclosed in the present invention is not limited to the above-mentioned circuits and devices. For example, any circuit topology that requires the use of inductive components for zero-voltage and/or zero-current switching can be used as disclosed in the present invention. Inductive coupling unit 10.

It is worth mentioning that, taking the half-bridge converter (half-bridge DC-to-AC power converter) shown in FIG. 25 as an example, it has a first switch S ₁ , a second switch S ₂ and an inductive coupling unit 10. The second switch S _{2 is} coupled to the first switch S ₁ at the common connection node. The first end of the inductive coupling unit 10 is coupled to the common node. In a period of time, the first switch S ₁ and the second switch S ₂ are turned on and off alternately. Wherein, in the positive half cycle, the principle and operation of the half-bridge converter can be similar to the embodiment shown in FIG. 10, that is, its specific operation can be referred to the description of FIG. 10 correspondingly, and will not be repeated here. In the negative half cycle, as mentioned above, _{the roles of the first switch S 1} and the second switch S ₂ will be reversed, and the roles of the first transistor switch SA ₁ and the second transistor switch SA ₂ included in the auxiliary switch unit will also be Will be interchanged, the same can realize the soft cut of zero voltage or zero current operation.

The T-shaped converter shown in FIG. 26 is a half-bridge converter shown in FIG. 25 and further includes a third switch S ₃ and a fourth switch S ₄ . The fourth switch S _{4 is} connected in series with the third switch S ₃ to form a series structure, and the series structure is coupled between the first terminal and the second terminal of the inductive coupling unit 10. Similarly, through a period of time, the first switch S ₁ and the second switch S ₂ are turned on and off alternately, and the first transistor switch SA ₁ and the second transistor switch SA ₂ are controlled to turn on and off accordingly. , It can also realize the soft cut of zero voltage or zero current operation.

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

1. The inductive coupling unit of the present invention only needs to wind the coupling coil on the main inductance or through the tap design of the main inductance, and cooperate with the auxiliary switch unit to achieve the soft cutting function of zero voltage or zero current.

2. In the application of DC or AC circuits, the coupled inductor replaces the external inductance element through the leakage inductance, and the capacitive element shares the capacitor connected to the inductor terminal. Without additional passive components, the circuit volume can be greatly reduced, and the efficiency and power density can be improved. And this circuit uses a coupling method and has the function of electrical isolation, which can further simplify the design of the drive circuit of the switch.

3. The inductive coupling unit of the present invention can flexibly cooperate with the application of the required circuit topology to realize the soft cutting function.

The above are only detailed descriptions and drawings of the preferred embodiments of the present invention. However, the features of the present invention are not limited to these, and are not intended to limit the present invention. The full scope of the present invention should be covered by the following patent application scope As the standard, all embodiments that conform to the spirit of the patent application of the present invention and similar changes should be included in the scope of the present invention. Anyone familiar with the art in the field of the present invention can easily think of changes or Modifications can be covered in the following patent scope of this case.

10: Inductive coupling unit

11: main inductance

12: auxiliary inductance

13: Auxiliary switch unit

Lm: Magnetizing inductance

Ls: Leakage inductance

A, B, C, D: coupling terminal

S ₁ : Main switch

S ₂ : Energy release switch

SA ₁ : The first transistor switch

SA ₂ : The second transistor switch

C ₁ , C ₂ : Capacitance

SA: Transistor Switch

D ₁ : The first diode

D ₂ : The second diode

D ₃ : The third diode

D ₄ : The fourth diode

Cs: Capacitance

Ls: inductance

Ss: switch

i _Lm : Magnetizing inductance current

i _Ls : Leakage inductance current

i _S1 , i _S2 : current

Figure 1: The circuit diagram of an existing step-down DC-DC converter.

Figure 2: It is a circuit diagram of an existing step-up DC-DC converter.

Figure 3: The waveform of the existing step-down converter operating in continuous conduction mode.

Figure 4: The waveform of the existing step-down converter operating in critical conduction mode.

Figure 5: It is a circuit diagram of an existing zero-voltage switching step-down converter.

Figure 6: It is the circuit diagram of the existing boost converter with zero voltage switching.

Fig. 7A is a circuit diagram of the first embodiment of the inductive coupling unit of the present invention.

Fig. 7B is a schematic diagram of the circuit element corresponding to Fig. 7A.

Fig. 8A is a circuit diagram of the second embodiment of the inductive coupling unit of the present invention.

Fig. 8B is a schematic diagram of the circuit element corresponding to Fig. 8A.

Fig. 9A is a circuit diagram of the third embodiment of the inductive coupling unit of the present invention.

Fig. 9B is a schematic diagram of the circuit element corresponding to Fig. 9A.

Figure 10: It is a circuit diagram of a step-down converter using the inductive coupling unit shown in Figure 7A.

Fig. 11A is a waveform diagram corresponding to the zero voltage switching control of Fig. 10.

Fig. 11B is a waveform diagram corresponding to the zero current switching control of Fig. 10.

Fig. 12 is a schematic diagram of the current path from time t0 to time t1 in Fig. 11A.

Fig. 13A and Fig. 13B are schematic diagrams of the current path from time t1 to time t2 in Fig. 11A.

Fig. 14 is a schematic diagram of the current path from time t2 to time t3 in Fig. 11A.

Fig. 15A and Fig. 15B are schematic diagrams of the current path from time t3 to time t4 in Fig. 11A.

Fig. 16: is a schematic diagram of the current path from time t4 to time t5 in Fig. 11A.

Fig. 17 is a schematic diagram of the current path from time t0 to time t1 in Fig. 11B.

Fig. 18 is a schematic diagram of the current path from time t1 to time t2 in Fig. 11B.

Fig. 19 is a schematic diagram of the current path from time t2 to time t3 in Fig. 11B.

Fig. 20 is a schematic diagram of the current path from time t3 to time t4 in Fig. 11B.

Fig. 21 is a schematic diagram of the current path from time t4 to time t5 in Fig. 11B.

Fig. 22 is a circuit diagram of another embodiment of the auxiliary switch unit of the present invention.

Fig. 23 is a circuit diagram of still another embodiment of the auxiliary switch unit of the present invention.

Figure 24: This is a circuit diagram of a full-bridge converter using the inductive coupling unit shown in Figure 7A.

Figure 25: It is a circuit diagram of a half-bridge converter using the inductive coupling unit shown in Figure 7A.

Figure 26: It is a circuit diagram of a T-converter using the inductive coupling unit shown in Figure 7A.

Figure 27: It is a circuit diagram of a multi-stage converter using the inductive coupling unit shown in Figure 7A.

Fig. 28 is a circuit diagram of a single-bus-bar boost power factor correction circuit using the inductive coupling unit shown in Fig. 7A.

Fig. 29: It is a circuit diagram of a dual-bus-bar boost power factor correction circuit using the inductive coupling unit shown in Fig. 7A.

Figure 30: It is a circuit diagram of a single-bus totem pole power factor correction circuit using the inductive coupling unit shown in Figure 7A.

Figure 31: It is a circuit diagram of a dual-bus bridgeless power factor correction circuit using the inductive coupling unit shown in Figure 7A.

10: Inductive coupling unit

11: The first inductance, the main inductance

12: The second inductance, auxiliary inductance

13: Auxiliary switch unit

Lm: Magnetizing inductance

Ls: Leakage inductance

A, B, C, D: coupling terminal

SA ₁ : The first transistor switch

SA ₂ : The second transistor switch

Claims (16)

A soft-cut power converter, including: One main switch, which is a controllable switch; A discharging switch, coupled to the main switch; and An inductive coupling unit, coupled to the main switch and the release switch, includes: A first inductance; A second inductor, coupled to the first inductor; and An auxiliary switch unit coupled to the second inductor to form a closed loop; Wherein, the main switch and the discharging switch are turned on and off alternately, and the auxiliary switch unit is controlled to be turned on before the main switch is turned on to provide at least one current path. The flexible cut power converter according to claim 1, wherein the first inductor includes a first coupling end and a second coupling end, and the first inductor is a part of the flexible cut power converter Main inductance. The soft-cut power converter according to claim 2, wherein one end of the second inductor is commonly connected to the second coupling end. The flexible cut power converter according to claim 1, wherein the first inductor and the second inductor are connected in series to form a main inductor of the flexible cut power converter. The soft-cut power converter according to claim 1, wherein the energy release switch is a controllable switch. The soft-cut power converter according to claim 5, wherein the auxiliary switch unit starts to conduct before the disabling switch is turned off, so that the main switch is operated in a zero voltage switching mode. The soft-cut power converter according to claim 5, wherein the auxiliary switch unit starts to conduct after the disabling switch is turned off, so that the main switch is operated in a zero current switching mode. The soft-cut power converter according to claim 1, wherein the inductive coupling unit is unidirectional current operation, and the auxiliary switch unit includes: An auxiliary switch, which is a controllable switch; and An auxiliary diode connected in series with the auxiliary switch to form a series structure to provide the at least one current path; Wherein, the series structure is coupled to both ends of the second inductor. The soft-cut power converter according to claim 1, wherein the inductive coupling unit is bidirectional current operation, and the auxiliary switch unit includes: A first transistor switch; and A second transistor switch, coupled in series to the first transistor switch to form a series structure, providing two current paths with opposite currents; Wherein, the series structure is coupled to both ends of the second inductor. The flexible cut power converter according to claim 1, wherein the inductive coupling unit is unidirectional current operation or bidirectional current operation, and the auxiliary switch unit includes: A first diode having a first end and a second end; A second diode having a first end and a second end; A third diode having a first end and a second end; A fourth diode having a first end and a second end; and An auxiliary switch, which is a transistor switch, has a first terminal and a second terminal; Wherein, the first end of the transistor switch is connected to the first end of the first diode and the first end of the third diode; the second end of the transistor switch is connected to the second end The first end of the pole body and the first end of the fourth diode; the second end of the first diode is connected to the second end of the second diode, the third diode The second end of the fourth diode is connected to the second end of the fourth diode to form a bridge structure to provide two current paths with opposite currents; Wherein, the bridge structure is coupled to both ends of the second inductor. The flexible cut power converter according to claim 1, wherein the inductive coupling unit is unidirectional current operation or bidirectional current operation, and the auxiliary switch unit includes: A first diode having a first end and a second end; A second diode having a first end and a second end; 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 end of the first diode is connected to the first end of the first transistor switch; the first end of the second diode is connected to the first end of the second transistor switch; The second end of the first diode is connected to the second end of the second diode, and the second end of the first transistor switch is connected to the second end of the second transistor switch to form One bridge structure provides two current paths with opposite currents; Wherein, the bridge structure is coupled to both ends of the second inductor. A soft-cut type power converter, which is a direct current AC power converter, including: A first switch; A second switch, coupled to the first switch at a common connection node; and An inductive coupling unit has a first end and a second end, the first end is coupled to the common connection node, and the inductive coupling unit includes: A first inductance; A second inductor, coupled to the first inductor; and An auxiliary switch unit coupled to the second inductor to form a closed loop; Wherein, within a period of time, the first switch and the second switch are turned on and off alternately, and the auxiliary switch unit is controlled to be turned on before the first switch is turned on to provide at least one current path. The soft-cut power converter described in claim 12 further includes: A third switch; A fourth switch is connected in series with the third switch to form a series structure, and the series structure is coupled between the first terminal and the second terminal of the inductive coupling unit. The flexible cut power converter according to claim 12 or 13, wherein the first inductor is a main inductor of the flexible cut power converter, and includes a first coupling end and a second coupling The first coupling end is the first end of the inductive coupling unit, and the second coupling end is the second end of the inductive coupling unit. The soft-cut power converter according to claim 14, wherein one end of the second inductor is commonly connected to the second coupling end. The flexible cut power converter according to claim 12 or 13, wherein the first inductor and the second inductor are connected in series to form a main inductor of the flexible cut power converter.

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