Power converter

Abstract

To provide a power conversion device capable of enhancing the degree of freedom in device selection of a ZVS assist circuit, and of shortening a reset time period of a resonance current in the ZVS assist circuit to reduce a turn-off loss of a main switch.SOLUTION: A power conversion device comprises: a converter that includes a main switch element, a main rectification element, an output capacitor, and a primary coil of a coupled inductor; and a resonance assist circuit configured as a closed loop circuit that includes a first series circuit having a secondary coil of the coupled inductor, a first rectification element, and an auxiliary switch element, a second series circuit having a tertiary coil of the coupled inductor and a second rectification element, and an auxiliary capacitor connected with the first and second series circuits. The secondary coil and the tertiary coil are separately formed. The power conversion device has a configuration in which the first and second series circuits are connected in parallel with the auxiliary capacitor or a configuration in which the tertiary coil is integrated with the secondary coil.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power conversion device.

Background Art

[0002] A ZVS (Zero Voltage Switching) circuit is known. The ZVS circuit switches on / off the switching element in a state where the applied voltage of the switching element becomes 0V by a soft switching method.

[0003] Patent Document 1 describes a boost converter and a buck converter provided with a ZVS assist circuit (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the ZVS assist circuit described in the patent document, since the reset period of the resonance current is long, the turn-off loss of the main switch (for example, switches 101 and 102 described in Patent Document 1) may increase.

[0006] The present disclosure has been made in consideration of such circumstances, and an object thereof is to provide a power conversion device that can increase the degree of freedom in device selection of a ZVS assist circuit, shorten the reset period of the resonance current in the ZVS assist circuit, and reduce the turn-off loss of the main switch. 。

[0007] Furthermore, this disclosure has been made in consideration of these circumstances and aims to provide a power converter equipped with a ZVS assist circuit and an effective control circuit. 。 [Means for solving the problem]

[0008] One aspect of the present disclosure is a converter including a main switch element, a main rectifier element, an output capacitor, and a primary winding of a coupled inductor; a resonance assist circuit comprising a closed-loop circuit including a first series circuit of the secondary winding of the coupled inductor, a first rectifier element, and an auxiliary switch element; a second series circuit of the tertiary winding of the coupled inductor and a second rectifier element; and an auxiliary capacitor to which the first and second series circuits are connected, wherein the secondary and tertiary windings are separate, and the first and second series circuits are connected in parallel to the auxiliary capacitor, or the tertiary winding is integrated with the secondary winding. Furthermore, the system includes a control unit, which turns on the main switch element after turning on the auxiliary switch element, and then turns off the main switch element after turning off the auxiliary switch element or simultaneously with turning off the auxiliary switch element, and the control unit determines the on-timing of the main switch element using the voltage of the tertiary winding or the auxiliary winding of the coupled inductor and the voltage of the auxiliary capacitor. It is a power conversion device.

[0009] One aspect of the present disclosure is a power conversion device comprising: a converter including a main switch element, a main rectifier element, an output capacitor, and a primary winding of a coupled inductor; a resonant assist circuit comprising a closed-loop circuit including a first series circuit of the secondary winding of the coupled inductor, a first rectifier element, and an auxiliary switch element; a second series circuit of the tertiary winding of the coupled inductor and a second rectifier element; and an auxiliary capacitor to which the first and second series circuits are connected, wherein the secondary and tertiary windings are separate components, the first and second series circuits are connected in parallel to the auxiliary capacitor, or the tertiary winding is integrated with the secondary winding, and the converter is a boost converter or a buck converter, and obtains a constant voltage source from the voltage of the second rectifier element via a rectifier diode. [Effects of the Invention]

[0018] According to the power conversion device described herein, the degree of freedom in selecting devices for the ZVS assist circuit can be increased, and the reset period of the resonant current in the ZVS assist circuit can be shortened, thereby reducing the turn-off loss of the main switch. 。

[0019] Furthermore, the power converter according to this disclosure makes it possible to provide a power converter equipped with a ZVS assist circuit and an effective control circuit. 。 [Brief explanation of the drawing]

[0020] [Figure 1] This figure shows an example of the circuit configuration of a power conversion device equipped with a ZVS assist circuit according to the present invention. [Figure 2]It is a diagram showing an example of the circuit configuration of a power conversion device including a ZVS assist circuit according to an embodiment. [Figure 3] It is a diagram showing an example of the circuit configuration of a power conversion device including a ZVS assist circuit according to an embodiment. [Figure 4] It is a diagram showing an example of the circuit configuration of a power conversion device including a ZVS assist circuit according to an embodiment. [Figure 5] It is a diagram showing a leakage inductor or an additional inductor according to an embodiment. [Figure 6] It is a diagram showing an example of waveforms in a power conversion device including a ZVS assist circuit according to an embodiment. [Figure 7] It is a diagram showing an example of the circuit configuration of a power conversion device related to an application example of a ZVS assist circuit according to an embodiment. [Figure 8] It is a diagram showing an example of the circuit configuration of a power conversion device related to an application example of a ZVS assist circuit according to an embodiment. [Figure 9] It is a diagram showing an example of the circuit configuration of a power conversion device related to an application example of a ZVS assist circuit according to an embodiment. [Figure 10] It is a diagram showing an example of the circuit configuration of a power conversion device related to an application example of a ZVS assist circuit according to an embodiment. [Figure 11] It is a diagram showing an example of the circuit configuration of a modified example of a ZVS assist circuit according to an embodiment. [Figure 12] It is a diagram showing an example of the circuit configuration of a modified example of a ZVS assist circuit according to an embodiment. [Figure 13] It is a diagram showing an example of the circuit configuration of a multiphase power conversion device including a ZVS assist circuit according to an embodiment. [Figure 14] It is a diagram showing an example of the circuit configuration of a power conversion device composed of an AC converter including a ZVS assist circuit according to an embodiment. [Figure 15] It is a diagram showing an example of the circuit configuration of a power conversion device composed of an AC converter including a ZVS assist circuit according to an embodiment. [Figure 16]It is a diagram showing an example of the circuit configuration of a power conversion device composed of an AC converter provided with a ZVS assist circuit according to an embodiment. [Figure 17] It is a diagram showing an example of waveforms in a power conversion device composed of an AC converter provided with a ZVS assist circuit according to an embodiment. [Figure 18] It is a diagram showing an example of the configuration of the control unit (drive circuit) of the ZVS assist circuit according to an embodiment. [Figure 19] It is a diagram showing an example of the configuration of the control unit (drive circuit) of the ZVS assist circuit according to an embodiment. [Figure 20] It is a diagram showing an example of the configuration of the control unit (drive circuit) of the ZVS assist circuit according to an embodiment. [Figure 21] (A), (B), and (C) are diagrams showing an example of the circuit configuration of a power conversion device provided with a quasi-ZVS assist circuit according to an embodiment. [Figure 22] It is a diagram showing an example of the circuit configuration of a power conversion device provided with a quasi-ZVS assist circuit according to an embodiment. [Figure 23] It is a diagram showing an example of the circuit configuration of a power conversion device provided with a quasi-ZVS assist circuit according to an embodiment. [Figure 24] It is a diagram showing an example of the circuit configuration of a power conversion device provided with a quasi-ZVS assist circuit according to an embodiment. [Figure 25] It is a diagram showing an example of waveforms in a power conversion device provided with a quasi-ZVS assist circuit according to an embodiment. [Figure 26] It is a diagram showing an example of the circuit configuration of a power conversion device composed of an AC converter provided with a quasi-ZVS assist circuit according to an embodiment. [Figure 27] It is a diagram showing an example of the circuit configuration of a power conversion device composed of an AC converter provided with a quasi-ZVS assist circuit according to an embodiment. [Figure 28] It is a diagram showing an example of an equivalent circuit of the circuit configuration of a power conversion device composed of an AC converter provided with a quasi-ZVS assist circuit according to an embodiment. [Figure 29]This figure shows an example of a waveform in a power conversion device consisting of an AC converter equipped with a quasi-ZVS assist circuit according to the embodiment. [Figure 30] This figure shows an example of the circuit configuration of a power conversion device consisting of an AC converter equipped with a quasi-ZVS assist circuit according to the embodiment. [Figure 31] (A) and (B) are diagrams showing an example of the circuit configuration of a power converter equipped with a quasi-ZVS assist circuit according to the embodiment. [Figure 32] This figure shows an example of the circuit configuration of a power conversion device equipped with a quasi-ZVS assist circuit according to the embodiment. [Figure 33] This figure shows an example configuration of the control unit (drive circuit) of the ZVS assist circuit according to the embodiment. [Figure 34] This figure shows an example configuration of the control unit (drive circuit) of the quasi-ZVS assist circuit according to the embodiment. [Figure 35] This figure shows an example configuration of the control unit (drive circuit) of the quasi-ZVS assist circuit according to the embodiment. [Figure 36] This figure shows an example configuration of the control unit (drive circuit) of the quasi-ZVS assist circuit according to the embodiment. [Figure 37] This figure shows an example configuration of a power conversion device including a quasi-ZVS assist circuit according to an embodiment. [Figure 38] This figure shows an example configuration of a power conversion device including a quasi-ZVS assist circuit according to an embodiment. [Figure 39] This figure shows an example configuration of the control unit (drive circuit) of the quasi-ZVS assist circuit according to the embodiment. [Figure 40] This figure shows an example of the circuit configuration of a power conversion device consisting of an AC converter equipped with a quasi-ZVS assist circuit according to the embodiment. [Figure 41] This figure shows an example of the circuit configuration of a power conversion device consisting of an AC converter equipped with a quasi-ZVS assist circuit according to the embodiment. [Figure 42] This figure shows an example of the circuit configuration of a multiphase power converter equipped with a ZVS assist circuit according to the embodiment. [Figure 43]This figure shows an example of the circuit configuration of a multiphase power converter equipped with a quasi-ZVS assist circuit according to the embodiment. [Figure 44] This figure shows an example of the circuit configuration of a power conversion device equipped with a ZVS assist circuit according to the present invention. [Figure 45] This figure shows an example of the circuit configuration of a power conversion device equipped with a quasi-ZVS assist circuit according to the embodiment. [Modes for carrying out the invention]

[0021] The embodiments of this disclosure will be described below with reference to the drawings. In the following embodiment, the switch element is considered to be in a conductive state when it is in the ON state, and in an open state when it is in the OFF state.

[0022] (Example of basic configuration of a power converter equipped with a ZVS assist circuit) Referring to Figures 1 to 5, a basic configuration example of a power converter equipped with a ZVS assist circuit (ZVS resonant assist circuit) will be explained. Figures 1 to 5 show the case where the power conversion device consists of a boost converter.

[0023] <Power converter device as shown in Figure 1> Figure 1 shows an example of the circuit configuration of a power converter 1 equipped with a ZVS assist circuit A1 according to an embodiment. In the example shown in Figure 1, the control circuit is not shown.

[0024] The power converter 1 comprises a main circuit and a ZVS assist circuit A1. The main circuit comprises a main switching element 11 (Qmain) made of a MOS-type FET (Field Effect Transistor), a main diode 12 (Dm), an output capacitor 13 (Co), and a primary winding 31 (Np) of a coupled inductor. Figure 1 also shows a DC power supply 21(Vi). Here, power supply 21 may be, for example, a power supply obtained by converting a commercial AC power supply to DC using a rectifier circuit (for example, a diode bridge). Generally, in a coupled inductor, two or more windings that make up the component are magnetically coupled to each other. These windings include, for example, a primary winding and a secondary winding, and there may also be a tertiary winding, auxiliary windings, etc.

[0025] For the sake of explanation, in the power converter 1, the two output terminals on the side to which the load (not shown in the figure) is connected will be referred to as the first output terminal T1 and the second output terminal T2. In the example in Figure 1, the first output terminal T1 is the ground (GND) side, and the second output terminal T2 is the positive (+) side.

[0026] In the main circuit, the power supply 21 and the switching element 11 are connected to each end of the primary winding 31 of the coupled inductor. The switching element 11 and the diode 12 are connected in series. The series circuit of the switching element 11 and the diode 12 is connected in parallel to the capacitor 13.

[0027] The ZVS assist circuit A1 comprises a coupled inductor with a primary winding 31 (Np), a secondary winding 32 (Ns), and a tertiary winding 33 (Nt), a diode 34 (Ds1), a switching element 35 (Qsub) made of a MOS-type FET, a diode 36 (Ds2), and an auxiliary capacitor 37 (Cs). Here, the primary winding 31(Np) of the coupled inductor can be considered as not being included in the ZVS assist circuit A1.

[0028] The first output terminal T1 is connected to one end of the capacitor 13, the source of the switch element 11, and one end of the power supply 21 (the negative terminal in the example in Figure 1). The second output terminal T2 is connected to the other end of capacitor 13 and to the cathode of diode 12. The other end of the power supply 21 (the + terminal in the example in Figure 1) is connected to one end of the primary winding 31 of the ZVS assist circuit A1. The other end of the primary winding 31 is connected to the drain of the switching element 11 and to the anode of the diode 12.

[0029] The first output terminal T1 is connected to one end of the capacitor 37, one end of the tertiary winding 33, and the source of the switch element 35. The drain of the switch element 35 is connected to the cathode of the diode 34. The anode of diode 34 is connected to one end of the secondary winding 32. The other end of the secondary winding 32 is connected to the other end of the capacitor 37, and the cathode of the diode 36 is connected to it. The other end of the tertiary winding 33 is connected to the anode of the diode 36.

[0030] <Power converter related to the example in Figure 2> Figure 2 shows an example of the circuit configuration of a power converter 2 equipped with a ZVS assist circuit A2 according to the embodiment. In the example shown in Figure 2, the control circuit is not shown.

[0031] The power converter 2 comprises a main circuit and a ZVS assist circuit A2. The main circuit is the same as the main circuit shown in the example in Figure 1, and the circuit elements of the main circuit are shown using the same reference numerals. Furthermore, Figure 2 shows a power supply 21(Vi) similar to that shown in Figure 1.

[0032] The ZVS assist circuit A2 is equipped with the same circuit elements as the ZVS assist circuit A1 shown in the example in Figure 1, and these circuit elements are shown using the same reference numerals. The ZVS assist circuit A2 differs from the ZVS assist circuit A1 shown in the example in Figure 1 in that one end of the capacitor 37, one end of the tertiary winding 33, and the source of the switch element 35 are not connected to the first output terminal T1.

[0033] Here, the negative (-) potential of the ZVS assist circuit A2 is generally set to the same ground potential as the main switch element 11, but it may be set to any potential. In the example shown in Figure 2, one end of the capacitor 37, one end of the tertiary winding 33, and the source of the switch element 35 may be connected to terminals of any potential.

[0034] <Power converter device as shown in Figure 3> Figure 3 shows an example of the circuit configuration of a power converter 3 equipped with a ZVS assist circuit A3 according to the embodiment. In the example shown in Figure 3, the control circuit is not shown.

[0035] The power converter 3 comprises a main circuit and a ZVS assist circuit A3. The main circuit is the same as the main circuit shown in the example in Figure 1, and the circuit elements of the main circuit are shown using the same reference numerals. Furthermore, Figure 3 shows a power supply 21(Vi) similar to that shown in Figure 1.

[0036] In the ZVS assist circuit A3, circuit elements similar to those in the ZVS assist circuit A1 shown in the example in Figure 1 are indicated using the same reference numerals. Compared to the ZVS assist circuit A1 shown in the example in Figure 1, the ZVS assist circuit A3 includes a tertiary winding 41(Nt) and a diode 42(Ds2) with the connection order of the tertiary winding 33 and diode 36 shown in Figure 1 reversed. The anode of diode 42 is connected to the first output terminal T1. The cathode of diode 42 is connected to one end of the tertiary winding 41. The other end of the tertiary winding 41 is connected to the other end of the secondary winding 32 and the other end of the capacitor 37.

[0037] <Power converter device as shown in Figure 4> Figure 4 shows an example of the circuit configuration of a power converter 4 equipped with a ZVS assist circuit A4 according to the embodiment. In the example shown in Figure 4, the control circuit is not shown.

[0038] The power converter 4 comprises a main circuit and a ZVS assist circuit A4. The main circuit is the same as the main circuit shown in the example in Figure 1, and the circuit elements of the main circuit are shown using the same reference numerals. Furthermore, Figure 4 shows a power supply 21(Vi) similar to that shown in Figure 1.

[0039] In the ZVS assist circuit A4, circuit elements similar to those in the ZVS assist circuit A1 shown in the example in Figure 1 are indicated using the same reference numerals. Compared to the ZVS assist circuit A1 shown in Figure 1, the ZVS assist circuit A4 includes a winding 51 (Nc=Ns-Nt), a tertiary winding 52 (Nt), and a diode 53 (Ds2) instead of the secondary winding 32, tertiary winding 33, and diode 36 shown in Figure 1. One end of winding 51 is connected to the anode of diode 34. The other end of winding 51 is connected to one end of tertiary winding 52. The other end of the tertiary winding 52 is connected to the other end of the capacitor 37. The cathode of diode 53 is connected to the first output terminal T1. The other end of diode 53 is connected to the other end of winding 51, and one end of tertiary winding 52 is connected to it.

[0040] The secondary winding (Ns) is composed of winding 51 and tertiary winding 52. In this embodiment, for the sake of explanation, the tapped winding is described as consisting of two windings (winding 51 and tertiary winding 52 in the example of Figure 4), but these two windings may also be described as a single tapped winding.

[0041] Figure 5 shows a leakage inductor or additional inductor according to the embodiment. Additional inductors are used, for example, when adjustments are needed. Figure 5 shows a portion of the circuitry in the ZVS assist circuit A1 shown in Figure 1 (the circuitry related to the secondary winding 32 and tertiary winding 33).

[0042] For example, the inductor 71 located between the secondary winding 32 and the diode 34 corresponds to the leakage inductor (Lks) of the secondary winding 32. Alternatively, an additional inductor (Ladd) 71 may be provided between the secondary winding 32 and the diode 34 (at the insertion point). For example, the inductor 72 located between the tertiary winding 33 and the diode 36 corresponds to the leakage inductor (Lkt) of the tertiary winding 33. Alternatively, an additional inductor (Ladd) 72 may be provided between the tertiary winding 33 and the diode 36 (at the insertion point).

[0043] In this embodiment, the ZVS assist circuit A1 (and similarly the ZVS assist circuits A2 to A4) generates a resonant operation between the leakage inductor or an additional inductor (additional inductor) in one or both of the secondary winding 32 and tertiary winding 33 of the tapped inductor, and the resonant capacitance component (Cr) in parallel with the main switch (switch element 11 in the examples of Figures 1 to 4) and the main rectifier element (diode 12 in the examples of Figures 1 to 4). Here, the resonant capacitance component (Cr) in parallel with the switch corresponds to the sum of the parasitic capacitance component of the switch and the capacitance of the capacitor connected in parallel with the switch.

[0044] <Example of power converter operation> Referring to Figure 6, an example of the operation performed in the power converter 1 shown in Figure 1 will be explained. The same applies to the examples of operations performed in power converters 2 to 4 shown in Figures 2 to 4.

[0045] Figure 6 shows an example of a waveform in a power converter 1 equipped with a ZVS assist circuit A1 according to an embodiment. In this embodiment, the control unit turns on the switch element 35 (Qsub) and then the switch element 11 (Qmain). Furthermore, the same control turns off the switch element 35 (Qsub) and then, simultaneously, turns off the switch element 11 (Qmain).

[0046] In the graph shown in Figure 6, the horizontal axis represents time (t), and the vertical axis represents the level of each waveform. Figure 6(A) shows waveforms 2011 representing the ON and OFF states of the gate of the switch element 35 (Qsub). Figure 6(B) shows waveform 2012 representing the ON and OFF states of the gate of switch element 11 (Qmain).

[0047] Figure 6(C) shows the waveform 2013 of the current flowing through the switch element 35 (Qsub). Furthermore, Figure 6(C) shows the current (IDs2) flowing through diode 36 for mode 5. Figure 6(D) shows the waveform 2014 of the current flowing through the excitation inductor Lm in the equivalent circuit of the primary winding 31 (Np) side, converted from the secondary winding 32 (Ns) side. Furthermore, Figure 6(D) shows the waveform 2015 of the current flowing through the switch element 11 (Qmain). Furthermore, Figure 6(D) shows the waveforms of the input current Iin for modes 2 and 3.

[0048] Figure 6(E) shows the waveform 2016 of the voltage across the excitation inductor Lm in the equivalent circuit of the primary winding 31 (Np) side, converted from the secondary winding 32 (Ns) side. Figure 6(F) shows the waveform 2017 of the voltage applied to the switch element 35 (Qsub). Figure 6(G) shows the waveform 2018 of the voltage applied to the switch element 11 (Qmain).

[0049] Figure 6 shows the transitions between operating modes. In the power converter 1, the state transitions sequentially from mode 1 to mode 7 according to the passage of time, and after being in mode 7, it returns to mode 1 again.

[0050] Here, we show an overview of modes 1 to 7, which are shown in Figure 6. Here, we assume an ideal device, and that the input voltage Vi is constant during the switching period Tsw.

[0051] (Mode 1) Mode 1 is the off-duty period of the converter when the inductor excitation current ILm conducts diode 12(Dm).

[0052] (Mode 2) During mode 2, the switch element 35 (Qsub) turns on. The current flowing through the switch element 35 (Qsub) increases with a predetermined current gradient, and the input current Iin decreases.

[0053] (Mode 3) During mode 3, the current flowing through diode 12(Dm) becomes 0[A], and diode 12(Dm) turns off. At this time, a soft recovery operation is obtained with a predetermined current slope, and the recovery loss of diode 12(Dm) can be reduced.

[0054] Here, assuming that the minimum voltage applied to the switch element 11 (Qmain) is 0 or less as the ZVS ON condition, the ZVS condition in (Equation 1) is obtained. Equation 1 adds an adjustable Nt / Ns to the ZVS condition (Vo>Vi / 2), which is the current critical mode (CRM) condition for a typical boost circuit. By designing a turns ratio of Ns and Nt that satisfies Equation 1, ZVS becomes possible over the entire input voltage range. Assuming a lower limit of the boost ratio, Vo=Vi, the upper limit of the turns ratio, Nt / Ns≦1 / 2, can be determined.

[0055] (Mode 4) During mode 4, when the voltage across the switch element 11(Qmain) becomes 0[V] due to resonant operation, the body diode of the switch element 11(Qmain) conducts. ZVS is turned on by turning on the switch element 11(Qmain) during this diode conduction period tm4_Neg. Here, a predetermined voltage is applied to the leakage inductor (Lks), and the current flowing through the switch element 35 (Qsub) decreases with a predetermined current gradient. The input current Iin increases to the excitation current ILm with a predetermined current gradient.

[0056] (Mode 5) During mode 5, the input current Iin reaches the excitation current ILm, and the converter enters its on-duty cycle. The current flowing through the auxiliary diode (Ds1) becomes 0[A], and the converter turns off with a soft recovery operation based on a predetermined current slope. Furthermore, because the assist current in modes 2 to 4 reduces the voltage of the auxiliary capacitor (Cs), a charging current flows from the tertiary winding through the leakage inductor (Lkt) and diode (Ds2). This charging current flows through the transformer and is superimposed on the input current Iin, flowing through the switch element 11 (Qmain).

[0057] (Mode 6) During mode 6, once the auxiliary capacitor (Cs) is fully charged, only the excitation current ILm conducts through the switch element 11 (Qmain). Furthermore, if the switch element 35 (Qsub) is turned off between modes 4 and 6, no turn-off loss occurs for the switch element 35 (Qsub).

[0058] (Mode 7) During mode 7, the switch element 11 (Qmain) is turned off. At this time, the parallel capacitors of diode 12 and switch element 11 (Qmain) result in ZVS turn-off. Here, if the excitation inductor (Lm) is sufficiently large and the system is approximated as a current source, the voltage across the switch element 11 (Qmain) rises to the output voltage Vo, and the system switches back to mode 1. Although the switch element 35 (Qsub) is already turned off, applying voltage causes a parasitic capacitance charge current ICoss to flow.

[0059] As described above, the power converters 1 to 4 according to this embodiment increase the degree of freedom in selecting devices for the ZVS assist circuit and shorten the reset period of the resonant current in the ZVS assist circuits A1 to A4, thereby reducing the turn-off loss of the main switch (Qmain). In the power converters 1 to 4 according to this embodiment, the reset period of the resonant current in the ZVS assist circuits A1 to A4 can be shortened by lowering the bias voltage of the auxiliary capacitor (Cs), thereby reducing the turn-off loss of the main switch (Qmain).

[0060] In the power conversion devices 1 to 4 according to this embodiment, the voltage of the ZVS assist circuit can be configured so that it does not depend on the voltage of the main circuit, thereby suppressing the increase in device costs.

[0061] In the power converters 1 to 4 according to this embodiment, a low dI / dt soft recovery effect and ZVS and Valley switching due to resonant operation are achieved with a small number of components using tapped inductors, enabling loss reduction and low noise. Furthermore, in the power converters 1 to 4 according to this embodiment, the voltage of the ZVS assist circuits A1 to A4 can be arbitrarily designed by the turns ratio, increasing the degree of freedom in device selection.

[0062] In the power converters 1 to 4 according to this embodiment, ZVS is achieved with a small number of components using coupled inductors, and the desired element breakdown voltage can be selected by the turns ratio of the coupled inductors. Therefore, it is expected that power semiconductors with excellent recovery characteristics and low ringing due to parasitic capacitance charge can be selected. Furthermore, in the power converters 1 to 4 according to this embodiment, ZVS operation is possible over a wide range of input-output voltage ratios by using auxiliary capacitors (Cs). Furthermore, since the sub-switch element (Qsub) is turned on in ZCS (Zero Current Switching) mode, parasitic capacitance charge is discharged and consumed by the on-resistance of the switch. However, by lowering the voltage, a reduction in parasitic capacitance loss can also be expected.

[0063] In this embodiment, power converters 1 to 4 show the case where an FET is used as the switching element, but other switching elements may be used. Furthermore, although the power conversion devices 1 to 4 according to this embodiment show the case in which a diode is used as the rectifying element, other rectifying elements may be used. For example, a switching element such as a MOS-type FET may be used instead of the main diode 12(Dm).

[0064] The ZVS assist circuit according to this embodiment can be applied, for example, to a boost converter, buck converter, buck-boost converter, or flyback converter in which the primary winding (Np) of a coupled inductor is connected for the purpose of smoothing, boosting, or bucking.

[0065] In the examples shown in Figures 1 to 4, a DC power supply 21 is used. However, as an example of other configurations, this power supply may also be a full-wave rectified voltage or a half-wave rectified voltage including pulsation, and it can also be applied to general power factor correction (PFC) circuits.

[0066] (Example of application configuration for a power converter equipped with a ZVS assist circuit) Referring to Figures 7 to 10, an example of an application configuration for a power converter equipped with a ZVS assist circuit (ZVS resonant assist circuit) will be explained.

[0067] <Power converter shown in the example in Figure 7> Figure 7 shows an example of the circuit configuration of a power converter 101 according to an application example of the ZVS assist circuit according to the embodiment. In the example shown in Figure 7, the control circuit is not shown.

[0068] The power converter 101 comprises a main circuit, a ZVS assist circuit, and a diode 118. The main circuit is the same as the main circuit in the example shown in Figure 1, and all circuit elements of the main circuit are shown using the same reference numerals, except for the primary winding 111(Np) of the coupled inductor. Furthermore, Figure 7 shows a power supply 21(Vi) similar to that shown in Figure 1. Figure 7 also shows the ground terminal G1, which is connected to the first output terminal T1.

[0069] The ZVS assist circuit in the example shown in Figure 7 has the same circuit elements as the ZVS assist circuit A4 in the example shown in Figure 4. Specifically, the ZVS assist circuit shown in the example in Figure 7 comprises a primary winding 111 (Np), winding 112 (Nc), and tertiary winding 113 (Nt) of a coupled inductor, a diode 114 (Ds1), a switching element 115 (Qsub) made of a MOS-type FET, a diode 116 (Ds2), and an auxiliary capacitor 117 (Cs). Here, the primary winding 111(Np) of the coupled inductor can be considered as not being included in the ZVS assist circuit. The secondary winding (Ns=Nc+Nt) is formed by winding 112 and the tertiary winding 113.

[0070] Here, the ZVS assist circuit in the example of Figure 7 has a circuit configuration similar to the ZVS assist circuit A4 in the example of Figure 4. In the example of Figure 7, the circuit configuration of the ZVS assist circuit is shown in the diagram with the left and right sides reversed (the polarity of the primary winding 111 is reversed) compared to the example of Figure 4.

[0071] The power converter 101 is further equipped with a diode 118 compared to the power converter 4 shown in Figure 4. The anode of diode 118 is connected to the cathode of diode 116. In the power converter 101 shown in the example in Figure 7, a voltage source (Vcc) can be obtained at the cathode of the diode 116. The voltage source (Vcc) may be used for any purpose, for example, to control the gate voltage of switch element 11 or switch element 115.

[0072] In the power converter 101 shown in Figure 7, the turn ratio that satisfies the ZVS condition is expressed by (Equation 1). In (Equation 1), Nt represents the number of turns of the tertiary winding 113, Ns represents the number of turns of the secondary winding, Vo represents the output voltage of the main circuit (the voltage between the first output terminal T1 and the second output terminal T2), and Vi represents the voltage of the power supply 21.

[0073]

number

[0074] The operating principle of the ZVS assist circuit in the power converter 101 is the same as that of the ZVS assist circuits A1 to A4 shown in Figures 1 to 4.

[0075] <Power converter device related to the example in Figure 8> Figure 8 shows an example of the circuit configuration of a power converter 102 according to an application example of the ZVS assist circuit according to the embodiment. The power converter 102 consists of a buck converter. In the example shown in Figure 8, the control circuit is not shown.

[0076] The power converter 102 comprises a main circuit, a ZVS assist circuit, and a diode 158. The main circuit comprises a capacitor 131 (Co) which is an output capacitor, a main switching element 132 (Qmain) consisting of a MOS-type FET, a main diode 133 (Dm), and a primary winding 151 (Np) of a coupled inductor. Figure 8 also shows the DC power supply 121(Vi). Here, power supply 121 is the same as power supply 21 shown in Figure 7.

[0077] For the sake of explanation, in the power converter 102, the two output terminals on the side to which the load (not shown) is connected will be referred to as the first output terminal T11 and the second output terminal T12. In the example in Figure 8, the first output terminal T11 is the ground (GND) side, and the second output terminal T12 is the positive (+) side. Figure 8 shows the ground terminal G1 connected to the first output terminal T11.

[0078] In the main circuit, a series circuit of the power supply 121 and the switching element 132, a diode 133, and a capacitor 131 are connected in parallel to one end of the primary winding 151 of the coupled inductor.

[0079] The first output terminal T11 is connected to one end of the capacitor 131, to the anode of the diode 156, and to one end of the power supply 121 (the negative terminal in the example in Figure 8). The other end of the power supply 121 (the + terminal in the example in Figure 8) is connected to the drain of the switch element 132. The second output terminal T12 is connected to the other end of capacitor 131. The cathode of diode 133 and the source of switch element 132 are connected to the second output terminal T12 via the primary winding 111 of the ZVS assist circuit.

[0080] The ZVS assist circuit comprises a coupled inductor with primary windings 151 (Np), 152 (Nc), and tertiary winding 153 (Nt), a diode 154 (Ds1), a switching element 155 (Qsub) consisting of a MOS-type FET, a diode 156 (Ds2), and an auxiliary capacitor 157 (Cs). Here, the primary winding 151(Np) of the coupled inductor can be considered as not being included in the ZVS assist circuit. The secondary winding (Ns=Nc+Nt) is formed by winding 152 and tertiary winding 153.

[0081] The circuit configuration of the ZVS assist circuit in the example shown in Figure 8 is the same as that of the ZVS assist circuit shown in Figure 7. The ZVS assist circuit in the example shown in Figure 8 is placed between the capacitor 131 and the diode 133 of the main circuit.

[0082] The power converter 102 is further equipped with a diode 158. The anode of diode 158 is connected to the cathode of diode 156. In the power converter 102 shown in the example in Figure 8, a voltage source (Vcc) can be obtained at the cathode of the diode 156. The voltage source (Vcc) may be used for any purpose, for example, to control the gate voltage of switch element 132 or switch element 155.

[0083] In the power converter 102 shown in Figure 8, the turn ratio that satisfies the ZVS condition is expressed by (Equation 2). In (Equation 2), Nt represents the number of turns of the tertiary winding 153, Ns represents the number of turns of the secondary winding, Vo represents the output voltage of the main circuit (the voltage between the first output terminal T11 and the second output terminal T12), and Vi represents the voltage of the power supply 121.

[0084]

number

[0085] The operating principle of the ZVS assist circuit in the power converter 102 is the same as that of the ZVS assist circuits A1 to A4 shown in Figures 1 to 4.

[0086] <Power converter related to the example in Figure 9> Figure 9 shows an example of the circuit configuration of a power converter 103 according to an application example of the ZVS assist circuit according to the embodiment. The power converter 103 consists of a buck-boost converter. In the example shown in Figure 9, the control circuit is not shown.

[0087] The power converter 103 includes a main circuit and a ZVS assist circuit. The main circuit comprises an output capacitor 181 (Co), a main diode 182 (Dm), a main switching element 183 (Qmain) consisting of a MOS-type FET, and a primary winding 211 (Np) of a coupled inductor. Figure 9 also shows the DC power supply 171(Vi). Here, power supply 171 is the same as power supply 21 shown in Figure 7.

[0088] For the sake of explanation, in the power converter 103, the two output terminals on the side to which the load (not shown) is connected will be referred to as the first output terminal T21 and the second output terminal T22. In the example in Figure 9, the first output terminal T21 is the ground (GND) side, and the second output terminal T22 is the positive (+) side.

[0089] In the main circuit, the primary winding 211 of the coupled inductor is connected in parallel to a series circuit of the power supply 171 and the switching element 183, and to a connection circuit of the diode 182 and the capacitor 181.

[0090] The first output terminal T21 is connected to one end of the capacitor 181 and to one end of the power supply 171 (the negative terminal in the example in Figure 9). The other end of the power supply 171 (the + terminal in the example in Figure 9) is connected to the drain of the switch element 183. The second output terminal T22 is connected to the other end of capacitor 181 and to the anode of diode 182. The cathode of diode 182 is connected to the source of switch element 183.

[0091] The ZVS assist circuit comprises a coupled inductor with primary windings 211 (Np) and 212 (Nc), a tertiary winding 213 (Nt), a diode 214 (Ds1), a switching element 215 (Qsub) consisting of a MOS-type FET, a diode 216 (Ds2), and an auxiliary capacitor 217 (Cs). Here, the primary winding 211(Np) of the coupled inductor can be considered as not being included in the ZVS assist circuit. The secondary winding (Ns = Nc + Nt) is formed by winding 212 and the tertiary winding 213.

[0092] One end of the primary winding 211 is connected to the first output terminal T21. The other end of the primary winding 211 is connected to the cathode of the diode 182 and the source of the switching element 183. Furthermore, except for the arrangement of the primary winding 211, the circuit configuration of the ZVS assist circuit in the example shown in Figure 9 is the same as that of the ZVS assist circuit shown in Figure 7. The ZVS assist circuit in the example shown in Figure 9 is positioned between the capacitor 181 and the primary winding 211 of the main circuit.

[0093] In the power converter 103 shown in Figure 9, the turn ratio that satisfies the ZVS condition is expressed by (Equation 3). In (Equation 3), Nt represents the number of turns of the tertiary winding 213, Ns represents the number of turns of the secondary winding, Vo represents the output voltage of the main circuit (the voltage between the first output terminal T21 and the second output terminal T22), and Vi represents the voltage of the power supply 171.

[0094]

number

[0095] The operating principle of the ZVS assist circuit in the power converter 103 is the same as that of the ZVS assist circuits A1 to A4 shown in Figures 1 to 4.

[0096] Furthermore, although the power conversion device 103 according to this embodiment is shown to use a diode as the rectifier element, other rectifier elements may be used. For example, a switching element such as a MOS-type FET may be used instead of the main diode 182(Dm).

[0097] <Power converter shown in the example in Figure 10> Figure 10 shows an example of the circuit configuration of a power converter 104 according to an application example of the ZVS assist circuit according to the embodiment. The power converter 104 consists of a flyback converter. In the example shown in Figure 10, the control circuit is not shown.

[0098] The power converter 104 includes a main circuit and a ZVS assist circuit. The main circuit comprises a capacitor 241 (Co) which is an output capacitor, a main diode 242 (Dm), two windings that constitute a switching transformer (referred to as winding 243 and primary winding 244 (Np)), and a main switching element 245 (Qmain) which is a MOS-type FET. The turns ratio between winding 243 and primary winding 244 is 1 to n. Figure 10 also shows a DC power supply 251(Vi). Here, power supply 251 is the same as power supply 21 shown in Figure 7.

[0099] For the sake of explanation, in the power converter 104, the two output terminals on the side to which the load (not shown) is connected will be referred to as the first output terminal T31 and the second output terminal T32. In the example in Figure 10, the first output terminal T31 is the ground (GND) side, and the second output terminal T32 is the positive (+) side.

[0100] In the main circuit, a power supply 251 and a switching element 245 are connected to each end of the primary winding 244 of the coupled inductor. A series circuit of winding 243, which is paired with the primary winding 244, and diode 242 is connected in parallel to capacitor 241.

[0101] The first output terminal T31 is connected to one end of the capacitor 241 and to one end of the winding 243. The other end of winding 243 is connected to the anode of diode 242. The second output terminal T32 is connected to the other end of capacitor 241 and to the cathode of diode 242. One end of the power supply 251 (the negative terminal in the example in Figure 10) is connected to the source of the switch element 245. The drain of the switch element 183 is connected to one end of the primary winding 244. The other end of the primary winding 244 is connected to the other end of the power supply 251 (the + terminal in the example in Figure 10).

[0102] The ZVS assist circuit comprises a coupled inductor with primary windings 244 (Np), 261 (Nc), and tertiary winding 262 (Nt), a diode 263 (Ds1), a switching element 264 (Qsub) consisting of a MOS-type FET, a diode 265 (Ds2), and an auxiliary capacitor 266 (Cs). Here, the primary winding 244(Np) of the coupled inductor can be considered as not being included in the ZVS assist circuit. The secondary winding (Ns=Nc+Nt) is formed by winding 261 and tertiary winding 262.

[0103] Except for the arrangement of the primary winding 244, the circuit configuration of the ZVS assist circuit in the example shown in Figure 10 is the same as that of the ZVS assist circuit A4 shown in Figure 4. The ZVS assist circuit in the example shown in Figure 10 is positioned between the switch element 245 of the main circuit and the power supply 251.

[0104] Here, in the power converter 104 shown in Figure 10, the turn ratio that satisfies the ZVS condition is expressed by (Equation 4). In (Equation 4), Nt represents the number of turns of the tertiary winding 262, Ns represents the number of turns of the secondary winding, Vo represents the output voltage of the main circuit (the voltage between the first output terminal T31 and the second output terminal T32), Vi represents the voltage of the power supply 251, and n represents the turns ratio of the transformer consisting of winding 243 and primary winding 244.

[0105]

number

[0106] The operating principle of the ZVS assist circuit in the power converter 104 is the same as that of the ZVS assist circuits A1 to A4 shown in Figures 1 to 4.

[0107] Furthermore, although the power conversion device 104 according to this embodiment is shown to use a diode as the rectifier element, other rectifier elements may be used. For example, a switching element such as a MOS-type FET may be used instead of the main diode 242(Dm).

[0108] In the examples shown in Figures 7 to 10, DC power supplies 21, 121, 171, and 251 are used. However, as an example of other configurations, this power supply may also be a full-wave rectified voltage or a half-wave rectified voltage including pulsation, and it can also be applied to a general power factor correction (PFC) circuit.

[0109] (Modified example of ZVS assist circuit) A modified example of the ZVS assist circuit (ZVS resonant assist circuit) will be explained with reference to Figures 11 and 12.

[0110] <ZVS assist circuit related to the example in Figure 11> Figure 11 shows an example of a circuit configuration according to a modified example of the ZVS assist circuit 301 according to the embodiment. The ZVS assist circuit 301 is a modified example of the ZVS assist circuit A2 shown in Figure 2, where the turns ratio between the number of turns of the secondary winding (Ns) and the number of turns of the tertiary winding (Nt) is 2:1 (Ns:Nt=2:1). In the example shown in Figure 11, the primary winding (Np) of the coupled inductor is omitted from the illustration.

[0111] The ZVS assist circuit 301 comprises a secondary winding 311 (Ns), a sub-switching element 312 (Qsub) consisting of a MOS-type FET, an auxiliary capacitor 313 (Cs), a diode 314 (Ds1'), a diode 315 (Ds2'), an auxiliary capacitor 316 (Cs), and a diode 317 (Ds1').

[0112] The source of the switch element 312 is connected to the anode of the diode 314 and to one end of the capacitor 316. The drain of the switch element 312 is connected to one end of the secondary winding 311. The cathode of diode 314 is connected to one end of capacitor 313, and the anode of diode 315 is connected to it. The other end of capacitor 316 is connected to the cathode of diode 315 and the anode of diode 317. The other end of the secondary winding 311 is connected to the other end of the capacitor 313, and the cathode of the diode 317 is connected to it.

[0113] <ZVS assist circuit related to the example in Figure 12> Figure 12 shows an example of a circuit configuration according to a modified example of the ZVS assist circuit 302 according to the embodiment. The ZVS assist circuit 302 is a modified example of the ZVS assist circuit A2 shown in Figure 2, where the turns ratio between the number of turns of the secondary winding (Ns) and the number of turns of the tertiary winding (Nt) is 3:1 (Ns:Nt=3:1). In the example shown in Figure 12, the primary winding (Np) of the coupled inductor is omitted from the illustration.

[0114] The ZVS assist circuit 302 comprises a secondary winding 331 (Ns), a sub-switching element 332 (Qsub) consisting of a MOS-type FET, an auxiliary capacitor 333 (Cs), a diode 334 (Ds1'), a diode 335 (Ds2'), an auxiliary capacitor 336 (Cs), a diode 337 (Ds2'), a diode 338 (Ds1'), a diode 339 (Ds1'), an auxiliary capacitor 340 (Cs), and a diode 341 (Ds1').

[0115] The source of the switch element 332 is connected to the anode of the diode 334, one end of the capacitor 336 is connected to the anode of the diode 339. The drain of the switch element 332 is connected to one end of the secondary winding 331. The cathode of diode 334 is connected to one end of capacitor 333, and the anode of diode 335 is connected to it. The cathode of diode 339 is connected to one end of capacitor 340, and the anode of diode 337 is connected to it. The cathode of diode 335 is connected to the other end of capacitor 340, and the anode of diode 341 is connected to it. The cathode of diode 337 is connected to the other end of capacitor 336, and the anode of diode 338 is connected to diode 338. The other end of the secondary winding 331 is connected to the cathode of diode 338, the other end of capacitor 333 is connected to the cathode of diode 341.

[0116] Note that while Figure 11 shows the case where (Ns:Nt=2:1) ​​and Figure 12 shows the case where (Ns:Nt=3:1), a similar modified circuit configuration is possible even when (Ns:Nt=q:1) and q is 4 or greater.

[0117] As shown in the examples in Figures 11 and 12, nonlinear capacitors can simplify the assist winding and the number of terminals (pins). While a larger number of series nonlinear capacitors (m) results in a lower component count, it allows for a reduction in the number of pins on the tapped inductor. In this case, Nt / Ns = 1 / m.

[0118] In the examples shown in Figures 11 and 12, a modified version of the ZVS assist circuit is applied to a boost converter. However, the modified version of the ZVS assist circuit may also be applied to a buck converter, a buck-boost converter, or a flyback converter.

[0119] Furthermore, similar to the examples in Figures 11 and 12, when (Ns:Nt=q:1), a circuit can be constructed by combining one or more rectifier elements (Ds1'), one or more rectifier elements (Ds2'), q auxiliary capacitors (Cs), a switch element (Qsub), and a secondary winding (Ns). When either one of the rectifier elements (Ds1') or (Ds2') is on and the other is off, the equivalent circuit is such that q auxiliary capacitors (Cs) are connected in series, and when the other is on and the other is off, the equivalent circuit is such that q auxiliary capacitors (Cs) are connected in parallel.

[0120] The circuit in the example shown in Figure 11 has a closed-loop circuit in which the secondary winding (Ns) of a coupled inductor is connected to an auxiliary capacitor (Cs), the cathode of a rectifier element (Ds2') via its anode, the auxiliary capacitor (Cs), and an auxiliary switch element (Qsub). It also has a closed-loop circuit in which the auxiliary capacitor (Cs), the secondary winding (Ns), the auxiliary switch element (Qsub), and the rectifier element (Ds1') are connected. The circuit in the example shown in Figure 12 includes an auxiliary capacitor (Cs), a rectifier element (Ds1'), and a rectifier element (Ds2') having the same connection rules as in the example shown in Figure 11. For example, it has a cascaded connection circuit consisting of a rectifier element (Ds1'), an auxiliary capacitor (Cs), and a rectifier element (Ds1').

[0121] (Example configuration of a multiphase power converter equipped with a ZVS assist circuit) Referring to Figure 13, an example configuration of a multiphase power converter equipped with a ZVS assist circuit (ZVS resonant assist circuit) will be described. Figure 13 shows a case where the power conversion device consists of a boost converter.

[0122] <ZVS assist circuit related to the example in Figure 13> Figure 13 shows an example of the circuit configuration of a multiphase power converter 401 equipped with a ZVS assist circuit according to the embodiment. Figure 13 shows an example configuration of a two-phase power converter 401. In the example shown in Figure 13, the control circuit is not shown.

[0123] The power converter 401 comprises a main circuit and a ZVS assist circuit. The main circuit comprises a main switching element 411 (Qmain) and a main diode 412 (Dm) consisting of a MOS-type FET for the first phase, a main switching element 413 (Qmain) and a main diode 414 (Dm) consisting of a MOS-type FET for the second phase, a capacitor 415 (Co) which is an output capacitor, a primary winding 431 (Np) of a coupled inductor corresponding to the first phase, and a primary winding 432 (Np) of a coupled inductor corresponding to the second phase. Figure 13 shows power supply 423.

[0124] For the sake of explanation, in the power converter 401, the two output terminals on the side to which the load (not shown in the figure) is connected will be referred to as the first output terminal T51 and the second output terminal T52. In the example in Figure 13, the first output terminal T51 is the ground (GND) side, and the second output terminal T52 is the positive (+) side.

[0125] The ZVS assist circuit includes a primary winding 431(Np) of a coupled inductor corresponding to the first phase and a primary winding 432(Np) of a coupled inductor corresponding to the second phase. Furthermore, the ZVS assist circuit includes a circuit section corresponding to the primary winding 431 of the first phase, comprising a winding 441 (Nt), a tertiary winding 442, a diode 445 (Ds1), a switching element 446 (Qsub) consisting of a MOS-type FET, a diode 447 (Ds2), and an auxiliary capacitor 448 (Cs). The secondary winding (Ns=Nc+Nt) is formed by winding 441 and tertiary winding 442. Furthermore, the ZVS assist circuit includes a winding 451 (Nt), a tertiary winding 452, a diode 453 (Ds1), and a switching element 454 (Qsub) consisting of a MOS-type FET, as a circuit section corresponding to the primary winding 432 of the second phase. Here, the primary windings 431(Np) and 432(Np) of the coupled inductor may be considered as not being included in the ZVS assist circuit.

[0126] The secondary winding (Ns=Nc+Nt) is formed by winding 451 and tertiary winding 452. In this explanation, we will describe the winding 451(Nt) and the tertiary winding 452 separately in order to explain the case where diode 461 is provided. However, if diode 461 is not provided, winding 451(Nt) and the tertiary winding 452 will be described as a single winding without taps.

[0127] The first output terminal T51 is connected to one end of capacitor 415, the source of switch element 411, the source of switch element 413, and one end of power supply 423 (the negative terminal in the example in Figure 1). The second output terminal T52 is connected to the other end of capacitor 415, the cathode of diode 412, and the cathode of diode 414. The other end of power supply 423 (the + terminal in the example in Figure 1) is connected to one end of primary winding 431 and one end of primary winding 432 of the ZVS assist circuit. The other end of the primary winding 431 is connected to the drain of the switch element 411 and to the anode of the diode 412. The other end of the primary winding 432 is connected to the drain of the switch element 413 and to the anode of the diode 414.

[0128] Here, the first phase circuit of the ZVS assist circuit has a circuit configuration similar to that of the ZVS assist circuit A4 in the example shown in Figure 4. Furthermore, the second phase circuit of the ZVS assist circuit shares the same capacitor 448 as the first phase. Furthermore, the second phase circuit section of the ZVS assist circuit may or may not include a diode 461. If a diode 461 is included, its anode is connected to the first output terminal T51, and its cathode is connected to a point between winding 451 and tertiary winding 452.

[0129] In the example shown in Figure 13, a configuration example of a two-phase power converter 401 is shown, but it is also possible to provide a ZVS assist circuit section corresponding to each phase in a power converter with three or more phases. Furthermore, while the example in Figure 13 shows a configuration in which some circuit elements (capacitor 448 in the example in Figure 13) are shared between the first phase circuit section and the second phase circuit section of the ZVS assist circuit, the ZVS assist circuit section may be provided separately for each phase.

[0130] In the example shown in Figure 13, the ZVS assist circuit is applied to a multiphase boost converter. However, the ZVS assist circuit may also be applied to a multiphase buck converter, a multiphase buck-boost converter, or a multiphase flyback converter.

[0131] In the example shown in Figure 13, a DC power supply 423 is used. However, as an example of other configurations, this power supply may also be a full-wave rectified voltage or a half-wave rectified voltage including pulsation, and it can also be applied to general power factor correction (PFC) circuits.

[0132] Furthermore, although the power conversion device 401 according to this embodiment is shown to use a diode as the rectifier element, other rectifier elements may be used. For example, instead of the main diodes 412(Dm) and 414(Dm), switching elements such as MOS-type FETs may be used.

[0133] (Example configuration of a power conversion device consisting of an AC converter equipped with a ZVS assist circuit) Referring to Figures 14 to 16, an example configuration of a power conversion device consisting of an AC converter equipped with a ZVS assist circuit will be described. Figures 14 to 16 show the case where the power conversion device consists of a boost converter.

[0134] <Power converter device as shown in Figure 14> Figure 14 shows an example of the circuit configuration of a power converter 501 equipped with a ZVS assist circuit according to the embodiment. In the example shown in Figure 14, the control circuit is not shown. Figure 14 shows an example of an application circuit to a totem pole PFC. In the example in Figure 14, the ZVS assist circuit controls whether or not the upper and lower arms assist based on the current polarity.

[0135] The power converter 501 includes a main circuit and a ZVS assist circuit. The main circuit comprises main switching elements 511 (Qmain) and 512 (Qmain) made of MOS-type FETs, half-wave rectifier diodes 513 (BD+) and 514 (BD-) which are half-wave rectifier elements for the input voltage, capacitor 515 (Co) which is an output capacitor, and primary winding 541 (Np) of a coupled inductor. Figure 14 also shows the AC power supply 523(Vi). Here, power supply 523 may be, for example, a commercial AC power supply. Here, the two main switching elements (Qmain), switch element 511 and switch element 512, have the following characteristics: during periods when the AC power supply 523 is positive, switch element 512 acts as the main rectifier element (QSR+) responsible for the recirculation of the excitation current of the primary winding 541; and during periods when the AC power supply 523 is negative, switch element 511 acts as the main rectifier element (QSR-) responsible for the recirculation of the excitation current of the primary winding 541. In this way, depending on whether the input voltage is positive or negative, one of the two main switching elements (Qmain), switch element 511 and switch element 512, becomes the main rectifier element (QSR).

[0136] For the sake of explanation, in the power converter 501, the two output terminals on the side to which the load (not shown in the figure) is connected will be referred to as the first output terminal T61 and the second output terminal T62. In the example in Figure 14, the first output terminal T61 is the ground (GND) side, and the second output terminal T62 is the positive (+) side.

[0137] The ZVS assist circuit comprises a coupled inductor with primary windings 541 (Np) and 542 (Nc), a tertiary winding 543 (Nt), a diode 544 (Ds1+), a switching element 545 (Qsub+) made of a MOS-type FET, a diode 546 (Ds2+), and an auxiliary capacitor 547 (Cs+). The ZVS assist circuit also includes a diode 548 (Ds1-), a switching element 549 (Qsub-) made of a MOS-type FET, a diode 550 (Ds2-), and an auxiliary capacitor 551 (Cs-). Here, the primary winding 541(Np) of the coupled inductor can be considered as not being included in the ZVS assist circuit. The secondary winding (Ns=Nc+Nt) is formed by winding 542 and tertiary winding 543.

[0138] The first output terminal T61 is connected to one end of capacitor 515, the anode of half-wave rectifier diode 513, the source of switch element 511, the source of switch element 545, the anode of diode 546, and one end of capacitor 547. The second output terminal T62 is connected to the other end of capacitor 515, the cathode of half-wave rectifier diode 514, and the drain of switch element 512. One end of power supply 523 (the negative terminal in the example in Figure 1) is connected to the cathode of half-wave rectifier diode 513 and the anode of half-wave rectifier diode 514. The other end of the power supply 523 (the + terminal in the example in Figure 1) is connected to one end of the primary winding 541. The other end of the primary winding 541 is connected to the drain of the switch element 511 and the source of the switch element 512.

[0139] The drain of the switch element 545 is connected to the cathode of the diode 544. One end of winding 542 is connected to the anode of diode 544 and to the source of switch element 549. The other end of winding 542 is connected to one end of tertiary winding 543, the cathode of diode 546 is connected to the anode of diode 550. The other end of the tertiary winding 543 is connected to the other end of capacitor 547, and one end of capacitor 551 is connected to it. The drain of the switch element 549 is connected to the cathode of the diode 548. The other end of capacitor 551 is connected to the cathode of diode 550 and the anode of diode 548.

[0140] In the example in Figure 14, direction P1 is shown. In the example in Figure 14, we assume that direction P1 is the direction with positive polarity.

[0141] <Power converter shown in the example in Figure 15> Figure 15 shows an example of the circuit configuration of a power converter 502 equipped with a ZVS assist circuit according to the embodiment. Figure 15 shows an example of an application circuit to the totem pole PFC. In the example shown in Figure 15, the control circuit is not shown.

[0142] The power converter 502 includes a main circuit and a ZVS assist circuit. The main circuit is the same as the main circuit shown in the example in Figure 14, and the circuit elements of the main circuit are shown using the same reference numerals. Furthermore, the primary winding 541 and direction P1 are the same as in the example in Figure 14, and are illustrated using the same reference numerals. Furthermore, Figure 15 shows a power supply 523 similar to the one shown in Figure 14.

[0143] The ZVS assist circuit comprises a coupled inductor with primary windings 541 (Np) and 572 (Nc), tertiary windings 573 (Nt) and 574 and 575, a diode 576 (Ds1+), a switching element 577 (Qsub+) made of a MOS-type FET, a thyristor 578 (SCR+), and an auxiliary capacitor 579 (Cs). Furthermore, the ZVS assist circuit includes a diode 580 (Ds1-), a switching element 581 (Qsub-) consisting of a MOS-type FET, and a thyristor 582 (SCR-). Here, the primary winding 541(Np) of the coupled inductor can be considered as not being included in the ZVS assist circuit. The secondary winding (Ns=Nc+Nt) is formed by winding 572 and tertiary winding 573. The secondary winding (Ns=Nc+Nt) is formed by winding 574 and tertiary winding 575. Capacitor 579 is shared by tertiary windings 573 and 575.

[0144] Here, the circuit section consisting of the primary winding 541, winding 572 (Nc), tertiary winding 573, diode 576, switch element 577, thyristor 578, and capacitor 579 is the same as the ZVS assist circuit A4 shown in Figure 4, except that it has a thyristor 578 instead of the diode 53 shown in Figure 4. Note that in the example in Figure 15, the circuit configuration of the circuit section is shown inverted left to right in the drawing compared to the example in Figure 4 (the polarity of winding 572 and tertiary winding 573 is reversed left to right).

[0145] Furthermore, the circuit section consisting of the primary winding 541, winding 574 (Nc), tertiary winding 575, diode 580, switch element 581, thyristor 582, and capacitor 579 is similar to the ZVS assist circuit A4 shown in Figure 4, except that it is equipped with a thyristor 582 instead of the diode 53 shown in Figure 4.

[0146] In the power converter 502 shown in the example in Figure 15, the device is implemented using only a low-side drive, and the driving of thyristors 578 and 582 is controlled according to the polarity of the current.

[0147] <Power converter shown in the example in Figure 16> Figure 16 shows an example of the circuit configuration of a power converter 503 equipped with a ZVS assist circuit according to the embodiment. Figure 16 shows an example of an application circuit to a totem pole PFC. In the example shown in Figure 16, the control circuit is not shown.

[0148] The power converter 503 includes a main circuit and a ZVS assist circuit. The main circuit is the same as the main circuit shown in the example in Figure 14, and the circuit elements of the main circuit are shown using the same reference numerals. Furthermore, the primary winding 541 and direction P1 are the same as in the example in Figure 14, and are illustrated using the same reference numerals. Furthermore, Figure 16 shows a power supply 523 similar to the one shown in Figure 14.

[0149] The ZVS assist circuit is similar to the ZVS assist circuit shown in the example in Figure 15, except that it includes diodes 592 and 593 instead of thyristors 578 and 582 shown in Figure 15, and also includes a switching element FET 591. The same reference numerals are used in the diagram. FET591 is located between the first output terminal T61 and capacitor 579. The source of FET591 is connected to the first output terminal T61. The drain of FET591 is connected to one end of capacitor 579. FET591 is an OR-Drive switch for switch elements 577 (Qsub+) and 581 (Qsub-).

[0150] Referring to Figure 17, we will now summarize and explain examples of operations performed in the power converter 502 shown in Figure 16 and the power converter 503 shown in Figure 17.

[0151] Figure 17 shows examples of waveforms in power converters 502 and 503, which consist of AC converters equipped with a ZVS assist circuit according to the embodiment. In the power converter 502, the on / off switching of switch element 577 (Qsub+), switch element 581 (Qsub-), thyristor 578 (SCR+), and thyristor 582 (SCR-) can be switched by control performed by the control unit. In the power converter 503, the on / off switching of switch element 577 (Qsub+), switch element 581 (Qsub-), and FET 591 are switched by control performed by the control unit.

[0152] In the graph shown in Figure 17, the horizontal axis represents time (t), and the vertical axis represents the level of each waveform. Figure 17(A) shows waveform 2111, which represents the ON and OFF states of FET591. Figure 17(B) shows waveform 2112, which represents the ON and OFF states of thyristor 582(SCR-). Figure 17(C) shows waveform 2113 representing the ON and OFF states of thyristor 578(SCR+).

[0153] Figure 17(D) shows waveforms 2114 representing the ON and OFF states of the switch element 581(Qsub-). Figure 17(E) shows waveforms 2115 representing the ON and OFF states of the switch element 577(Qsub+). Figure 17(F) shows waveform 2116 representing the voltage (Vi) of power supply 523, and waveform 2117 representing the current (Iin) from power supply 523.

[0154] In the examples shown in Figures 14 to 16, the half-wave rectifier diodes 513 and 514 in the main circuit may be replaced with switching elements such as MOS-type FETs, in which case a bidirectional converter can be realized.

[0155] Here, the examples in Figures 14 to 17 show the application of the ZVS assist circuit to a boost converter, but the ZVS assist circuit may also be applied to a buck converter, buck-boost converter, or flyback converter.

[0156] Furthermore, in the totem pole PFC, if the half-wave rectifier diodes (corresponding to half-wave rectifier diodes 513 and 514 in the examples of Figures 14 to 16) are turned off by reverse current and interfere with this resonant operation, interference with the resonant operation can be prevented by connecting a capacitive component in parallel with the half-wave rectifier diodes (corresponding to half-wave rectifier diodes 513 and 514 in the examples of Figures 14 to 16). Alternatively, interference with the resonant operation can also be prevented by replacing half-wave rectifier diodes 513 and 514 in the examples of Figures 14 to 16 with a switching element such as an FET, so that a reverse current can flow through the half-wave rectifier diodes (corresponding to half-wave rectifier diodes 513 and 514 in the examples of Figures 14 to 16).

[0157] (Example configuration of the control unit (drive circuit) of the ZVS assist circuit) Referring to Figures 18 to 20, an example of the configuration of the control unit (drive circuit) of the ZVS assist circuit (ZVS resonant assist circuit) will be explained. Figures 18 to 20 show the case where the power conversion device consists of a boost converter.

[0158] <Control unit of the ZVS assist circuit in the example shown in Figure 18> Figure 18 shows an example of the configuration of the control unit (drive circuit) of the ZVS assist circuit according to the embodiment. Figure 18 shows a power converter 601 having a similar configuration to the power converter 4 shown in Figure 4, but also equipped with a control unit. In the example in Figure 18, the same reference numerals are used for the same circuit components as in Figure 4. Figure 18 shows the power supply 23. The first output terminal T1 is connected to the ground terminal G1.

[0159] The control unit comprises an auxiliary winding 611, an arithmetic unit 612, a comparator 613, an AND gate 614, an AND gate 615, an on-delay circuit 616, and an OR gate 617. The AND614 receives an enable signal and a PWM (Pulse Width Modulation) signal as inputs and outputs the logic results of these signals to the gate of the switch element 35 (Qsub). Generally, on-delay circuits delay only the rising edge, while off-delay circuits delay only the falling edge.

[0160] In this embodiment, a control IC (not shown) outputs an enable signal and a PWM signal. The enable signal controls whether or not ZVS assist is enabled. For example, the enable signal can be used to disable ZVS assist operation under certain conditions, thereby adding a function to reduce reactive current loss and prevent surge voltage to the switch element 35 (Qsub).

[0161] One end of the auxiliary winding 611 is connected to the first output terminal T1, and the other end of the auxiliary winding 611 is connected to the + input terminal of the comparator 613. Furthermore, a diode 621 may or may not be provided between the auxiliary winding 611 and the + input terminal of the comparator 613, such that the direction from the auxiliary winding 611 to the comparator 613 is forward.

[0162] The arithmetic unit 612 is connected to the other end of the capacitor 37 and outputs the voltage across the capacitor 37 multiplied by K to the negative input terminal of the comparator 613. Comparator 613 outputs values ​​to AND 615 corresponding to the inputs at the + and - terminals. Specifically, comparator 613 outputs a value of 1 if the input at the + terminal is greater than the input at the - terminal, and outputs a value of 0 if the input at the + terminal is less than the input at the - terminal.

[0163] The AND615 receives the PWM signal and the output from the comparator 613 as input and outputs the logic results of these to the OR617. The on-delay circuit 616 delays the PWM signal and outputs it to the OR 617. The OR617 receives the output from the AND615 and the output from the on-delay circuit 616, and outputs these logic results to the gate of the switch element 11 (Qmain).

[0164] Here, the value multiplied by the arithmetic unit 612 (in this example, K times) is determined, for example, by the leakage inductor (and the additional inductor if one is provided), and the threshold value of the comparator 613 (minus the value at the input terminal) is determined from this value and the voltage across the capacitor 37. As a concrete example, the theoretical value for a tapped inductor constructed using only leakage inductors (Lk) is basically K = 1 / 2. However, if the leakage inductance ratio is unbalanced between the primary and secondary windings, K will be adjusted accordingly. When resonance assistance is provided solely by the leakage inductor (Lk) of a tapped inductor, the ON timing of the switch element 11 (Qmain) can be determined by comparing half the voltage of capacitor 37 (Cs) with the voltage of the tertiary winding 52 (Nt) or the auxiliary winding 611 (Nt').

[0165] Furthermore, if an additional inductor (Ladd) is present, K needs to be adjusted, so K = 1 / 2 ± α, where α is the adjustment value. When using an additional inductor (Ladd), the coefficient K of the voltage of the capacitor 37 (Cs) being compared is changed.

[0166] Furthermore, the same operation can be achieved by setting the number of turns of the auxiliary winding 611(Nt') to Nt / K and comparing it with the voltage of the capacitor 37(Cs).

[0167] <Control unit of the ZVS assist circuit in the example shown in Figure 19> Figure 19 shows an example of the configuration of the control unit (drive circuit) of the ZVS assist circuit according to the embodiment. Figure 19 shows a power converter 602 having a similar configuration to the power converter 4 shown in Figure 4, but equipped with a control unit. In the example in Figure 19, the same reference numerals are used for circuit components that are the same as those shown in Figure 4. Figure 19 shows the power supply 23. The first output terminal T1 is connected to the ground terminal G1.

[0168] The control unit comprises a diode 651, a capacitor 652, an arithmetic unit 642, a comparator 643, an AND gate 644, an AND gate 645, an on-delay circuit 646, and an OR gate 647. Here, the configuration of the control unit shown in Figure 19 differs from the configuration of the control unit shown in Figure 18 in that the input side configuration of the comparator 643 is different, but other aspects are the same.

[0169] The anode of diode 651 is connected to the negative input terminal of comparator 643, and the cathode of diode 53 is connected to it. Furthermore, a diode 661 may or may not be provided between the cathode of diode 53 and the negative input terminal of comparator 643, with the direction from diode 53 to comparator 643 being the forward direction.

[0170] One input terminal of the arithmetic unit 642 is connected to the other terminal of the capacitor 37(Cs). The other input terminal of the arithmetic unit 642 is connected to the cathode of the diode 651. One end of capacitor 652 is connected to the ground terminal G1. The other end of capacitor 652 is connected to the cathode of diode 651. The output terminal of the arithmetic unit 642 is connected to the + input terminal of the comparator 643.

[0171] The example in Figure 19 shows a case where neither the tertiary winding (Nt) nor the auxiliary winding (Nt') is used. The function f(n) of the arithmetic unit 642 obtains its output value using the voltage across capacitor 37 (Cs) (the input voltage Vi obtained from it) and a voltage that is n times the output voltage (Vo) obtained from the voltage across diode 53 (Ds2). The comparator 643 compares the output of the arithmetic unit 642 with the voltage of the diode 53 (Ds2) to generate a signal for controlling the switch element 11 (Qmain).

[0172] <Control unit of the ZVS assist circuit in the example shown in Figure 20> Figure 20 shows an example of the configuration of the control unit (drive circuit) of the ZVS assist circuit according to the embodiment. Figure 20 shows a power converter 603 that has a similar configuration to the power converter 2 shown in Figure 2, but also includes a control unit. In the example in Figure 20, the same reference numerals are used for circuit components that are the same as those shown in Figure 2. Figure 20 shows the power supply 23. The first output terminal T1 is connected to the ground terminal G1.

[0173] The control unit comprises an arithmetic unit 682, a comparator 683, an AND gate 684, an AND gate 685, an on-delay circuit 686, and an OR gate 687. Here, the configuration of the control unit shown in Figure 20 differs from the configuration of the control unit shown in Figure 18 in that the input side configuration of the comparator 683 is different, but other aspects are the same.

[0174] The anode of diode 36 (Ds2) is connected to the + input terminal of comparator 683. Furthermore, a diode 691 may be provided between the anode of diode 36(Ds2) and the + input terminal of comparator 683, such that the direction from the anode of diode 36(Ds2) to comparator 683 is forward, or it may not be provided.

[0175] The arithmetic unit 682 is connected to the other end of capacitor 37 and the cathode of diode 36 (Ds2), and outputs the voltage across capacitor 37 multiplied by K to the negative input terminal of comparator 683.

[0176] In the example shown in Figure 20, the tertiary winding 33 (Nt) is treated as a separate winding, and the auxiliary winding (Nt') is not used.

[0177] In addition, in the examples of FIGS. 18 to 20, a configuration in which the on-delay circuits 616, 646, and 686 are not provided may be used. In the examples of FIGS. 18 to 20, since there is a case where the switching element 35 (Qsub) does not turn on during the transient operation, the on-delay circuits 616, 646, and 686 force it to turn on after the prescribed dead time (tdead) has elapsed.

[0178] Here, in the examples of FIGS. 18 to 20, the case where the ZVS assist circuit is applied to the boost converter is shown, but the ZVS assist circuit may be applied to a buck converter, a buck-boost converter, or a flyback converter.

[0179] Here, in the examples of FIGS. 18 to 20, the case where the DC power supply 23 is used is shown, but as another configuration example, this power supply may be a full-wave rectified voltage or a half-wave rectified voltage including pulsating current, and is also applicable to a general power factor correction circuit (PFC).

[0180] (Basic configuration example of a power conversion device equipped with a quasi-ZVS assist circuit) Referring to FIGS. 21 to 24, a basic configuration example of a power conversion device equipped with a quasi-ZVS assist circuit (quasi-ZVS resonance assist circuit) will be described.

[0181] (Power conversion device according to the example of FIG. 21) FIG. 21(A) is a diagram showing an example of the circuit configuration of a power conversion device 1001 equipped with a quasi-ZVS assist circuit according to an embodiment. In FIG. 21(A), the case where the power conversion device is composed of a boost (step-up type) converter is shown. In the example of FIG. 21(A), the illustration of the control circuit is omitted.

[0182] The power conversion device 1001 includes a main circuit and a quasi-ZVS assist circuit. The main circuit is the same as the main circuit according to the example of FIG. 1, and circuit elements of the main circuit are shown using the same reference numerals except for the primary winding 1131 (Np) of the coupled inductor. Furthermore, Figure 21(A) shows a power supply 21(Vi) similar to that shown in Figure 1.

[0183] The quasi-ZVS assist circuit comprises a primary winding 1131 (Np) and a secondary winding 1132 (Ns) of a coupled inductor, a diode 1133 (Ds1), and a switching element 1134 (Qsub) consisting of a MOS-type FET. Here, the primary winding 1131(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit.

[0184] The first output terminal T1 is connected to one end of the secondary winding 1132 and to the source of the switch element 1134. The other end of the secondary winding 1132 is connected to the anode of the diode 1133. The cathode of diode 1133 is connected to the drain of switch element 1134.

[0185] Here, the configuration of the quasi-ZVS assist circuit shown in Figure 21(A) differs from that of the ZVS assist circuit A1 shown in Figure 1 in that it lacks the tertiary winding 33(Nt), the diode 36(Ds2), and the capacitor 37(Cs).

[0186] Here, in the power converter 1001, the input-output voltage ratio that satisfies the quasi-ZVS condition is expressed by (Equation 5). In (Equation 5), Vo represents the output voltage of the main circuit (the voltage between the first output terminal T1 and the second output terminal T2), and Vi represents the voltage of the power supply 21.

[0187]

number

[0188] The quasi-ZVS assist circuit is also applicable when Vo and Vi do not satisfy the ZVS conditions. For example, if the ZVS condition is satisfied even when Nt / Ns ≤ 0, it is possible to create a configuration (quasi-ZVS assist circuit) by removing the auxiliary capacitor (Cs) and diode (Ds2). In the quasi-ZVS assist circuit, valley switching is used instead of ZVS, and parasitic capacitance loss occurs when the switch element 11 (Qmain) is turned on, but soft recovery effect and soft switching effect are obtained, resulting in low loss.

[0189] Figure 21(B) shows another configuration example of the quasi-ZVS assist circuit shown in Figure 21(A). The quasi-ZVS assist circuit shown in Figure 21(B) comprises a primary winding 1131a (Np) and a secondary winding 1132a (Ns) of a coupled inductor, a diode 1133a (Ds1), and a switching element 1134a (Qsub) consisting of a MOS-type FET. Here, the primary winding 1131a(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit. In the quasi-ZVS assist circuit shown in Figure 21(B), the way the circuit elements are connected differs from the example in Figure 21(A), and the arrangement of diode 1133a(Ds1) is different. Even if the position of diode 1133a (Ds1) is changed, as in the example in Figure 21(B), it remains equivalent to the example in Figure 21(A).

[0190] Figure 21(C) shows another example of the quasi-ZVS assist circuit shown in Figure 21(A). The quasi-ZVS assist circuit shown in Figure 21(C) comprises a primary winding 1131b(Np) and a secondary winding 1132b(Ns) of a coupled inductor, a diode 1133b(Ds1), and a switching element 1134b(Qsub) consisting of a MOS-type FET. Here, the primary winding 1131b(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit. In the quasi-ZVS assist circuit shown in FIG. 21(C), compared with the example of FIG. 21(A), the connection method of circuit elements is different, and the arrangement of the diode 1133b (Ds1) is different. In the example of FIG. 21(C), the drain of the switch element 1134b is connected to one end of the secondary winding 1132b, the cathode of the diode 1133b is connected to the other end of the secondary winding 1132b, and the source of the switch element 1134b and the anode of the diode 1133b are connected to the first output terminal T1. Even if the position of the diode 1133b (Ds1) changes as in the example of FIG. 21(C), it is equivalent to the example of FIG. 21(A).

[0191] In addition, in the power conversion device 1001 according to the present embodiment, although the case where a diode is used as the rectifying element is shown, other rectifying elements may be used. For example, instead of the main diode 12 (Dm), a switch element such as a MOS type FET may be used.

[0192] <Power conversion device according to the example of FIG. 22> FIG. 22 is a diagram showing an example of the circuit configuration of a power conversion device 1002 provided with a quasi-ZVS assist circuit according to an embodiment. FIG. 22 shows the case where the power conversion device is composed of a buck (step-down) converter. In the example of FIG. 22, the illustration of the control circuit is omitted.

[0193] The power conversion device 1002 includes a main circuit and a quasi-ZVS assist circuit. The main circuit is the same as the main circuit according to the example of FIG. 8, and circuit elements of the main circuit are shown using the same reference numerals except for the primary winding 1151 (Np) of the coupled inductor. Also, FIG. 22 shows a power supply 121 (Vi) similar to that shown in FIG. 8. Also, FIG. 22 shows a ground terminal G1.

[0194] The quasi-ZVS assist circuit comprises a primary winding 1151 (Np) and a secondary winding 1152 (Ns) of a coupled inductor, a diode 1153 (Ds1), and a switching element 1154 (Qsub) consisting of a MOS-type FET. Here, the primary winding 1151(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit.

[0195] The first output terminal T11 is connected to one end of the secondary winding 1152 and to the source of the switch element 1154. The other end of the secondary winding 1152 is connected to the anode of the diode 1153. The cathode of diode 1153 is connected to the drain of switch element 1154.

[0196] Here, the configuration of the quasi-ZVS assist circuit shown in Figure 22 differs from the ZVS assist circuit shown in Figure 8 in that it lacks the tertiary winding 153 (Nt), the diode 156 (Ds2), and the capacitor 157 (Cs).

[0197] Here, in the power converter 1002, the input-output voltage ratio that satisfies the quasi-ZVS condition is expressed by (Equation 6). In (Equation 6), Vo represents the output voltage of the main circuit (the voltage between the first output terminal T11 and the second output terminal T12), and Vi represents the voltage of the power supply 121.

[0198]

number

[0199] The power converter 1002 further includes a diode 1155. The anode of diode 1155 is connected to the anode of diode 1153. In the power converter 1002 shown in the example in Figure 22, a voltage source (Vcc) can be obtained at the cathode of the diode 1155. The voltage source (Vcc) may be used for any purpose, for example, to control the gate voltage of switch element 132 or switch element 1154.

[0200] Furthermore, although the power conversion device 1002 according to this embodiment is shown as using a diode as the rectifier element, other rectifier elements may be used. For example, a switching element such as a MOS-type FET may be used instead of the main diode 133(Dm).

[0201] <Power converter related to the example in Figure 23> Figure 23 shows an example of the circuit configuration of a power converter 1003 equipped with a quasi-ZVS assist circuit according to the embodiment. Figure 23 shows a case where the power conversion device consists of a buck-boost converter. In the example shown in Figure 23, the control circuit is not shown.

[0202] The power converter 1003 comprises a main circuit and a quasi-ZVS assist circuit. The main circuit is the same as the main circuit shown in the example in Figure 9, and all circuit elements of the main circuit are shown using the same reference numerals, except for the primary winding 1171(Np) of the coupled inductor. Furthermore, Figure 23 shows a power supply 171(Vi) similar to that shown in Figure 9. Figure 23 also shows the ground terminal G1.

[0203] The quasi-ZVS assist circuit comprises a primary winding 1171 (Np) and a secondary winding 1172 (Ns) of a coupled inductor, a diode 1173 (Ds1), and a switching element 1174 (Qsub) consisting of a MOS-type FET. Here, the primary winding 1171(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit. The arrangement of the primary winding 1171 is the same as in the example in Figure 9.

[0204] The first output terminal T21 is connected to one end of the secondary winding 1172 and to the source of the switch element 1174. The other end of the secondary winding 1172 is connected to the anode of the diode 1173. The cathode of diode 1173 is connected to the drain of switch element 1174.

[0205] Here, the configuration of the quasi-ZVS assist circuit shown in Figure 23 differs from the ZVS assist circuit shown in Figure 9 in that it lacks the tertiary winding 213 (Nt), the diode 216 (Ds2), and the capacitor 217 (Cs).

[0206] Here, in the power converter 1003, the input-output voltage ratio that satisfies the quasi-ZVS condition is expressed by (Equation 7). In (Equation 7), Vo represents the output voltage of the main circuit (the voltage between the first output terminal T21 and the second output terminal T22), and Vi represents the voltage of the power supply 171.

[0207]

number

[0208] The power converter 1003 further includes a diode 1181. The anode of diode 1181 is connected to the anode of diode 1173. In the power converter 1003 shown in the example in Figure 23, a voltage source (Vcc) can be obtained at the cathode of the diode 1181. The voltage source (Vcc) may be used for any purpose, for example, to control the gate voltage of switch element 183 or switch element 1174.

[0209] Furthermore, although the power converter 1003 according to this embodiment shows a case where a diode is used as the rectifier element, other rectifier elements may be used. For example, a switching element such as a MOS-type FET may be used instead of the main diode 182(Dm).

[0210] <Power converter related to the example in Figure 24> Figure 24 shows an example of the circuit configuration of a power converter 1004 equipped with a quasi-ZVS assist circuit according to the embodiment. Figure 24 shows a case where the power converter consists of a flyback converter. In the example shown in Figure 24, the control circuit is not shown.

[0211] The power converter 1004 comprises a main circuit and a quasi-ZVS assist circuit. The main circuit is the same as the main circuit shown in the example in Figure 10, and the circuit elements of the main circuit are shown using the same reference numerals. Furthermore, Figure 24 shows a power supply 251(Vi) similar to that shown in Figure 10. Figure 24 also shows the ground terminal G1.

[0212] The quasi-ZVS assist circuit comprises a primary winding 244 (Np) and a secondary winding 1211 (Ns) of a coupled inductor, a diode 1212 (Ds1), and a switching element 1213 (Qsub) consisting of a MOS-type FET. Here, the primary winding 244(Np) of the coupled inductor can be considered as not being included in the quasi-ZVS assist circuit.

[0213] The source of switch element 245 (Qmain) is connected to one end of power supply 251, one end of secondary winding 1211, and the source of switch element 1213. The other end of the secondary winding 1211 is connected to the anode of the diode 1212. The cathode of diode 1212 is connected to the drain of switch element 1213.

[0214] Here, the configuration of the quasi-ZVS assist circuit shown in Figure 24 differs from the ZVS assist circuit shown in Figure 10 in that it lacks the tertiary winding 262 (Nt), the diode 265 (Ds2), and the capacitor 266 (Cs).

[0215] Here, in the power converter 1004, the input-output voltage ratio that satisfies the quasi-ZVS condition is expressed by (Equation 8). In (Equation 8), Vo represents the output voltage of the main circuit (the voltage between the first output terminal T31 and the second output terminal T32), and Vi represents the voltage of the power supply 251.

[0216]

number

[0217] The power converter 1004 is further equipped with a diode 1221. The anode of diode 1221 is connected to the anode of diode 1212. In the power converter 1004 shown in the example in Figure 24, a voltage source (Vcc) can be obtained at the cathode of the diode 1221. The voltage source (Vcc) may be used for any purpose, for example, to control the gate voltage of switch element 245 or switch element 1213.

[0218] Furthermore, although the power conversion device 1004 according to this embodiment is shown to use a diode as the rectifier element, other rectifier elements may be used. For example, a switching element such as a MOS-type FET may be used instead of the main diode 242(Dm).

[0219] In the examples shown in Figures 21 to 24, DC power supplies 21, 121, 171, and 251 are used. However, as an example of other configurations, this power supply may also be a full-wave rectified voltage or a half-wave rectified voltage including pulsation, and it can also be applied to a general power factor correction (PFC) circuit.

[0220] <Example of power converter operation> Referring to Figure 25, an example of the operation performed in the power converter 1001 shown in Figure 21 will be explained. The same applies to the examples of operations performed in the power converters 1002 to 1004 shown in Figures 22 to 24.

[0221] Figure 25 shows an example of a waveform in a power converter 1001 equipped with a quasi-ZVS assist circuit according to an embodiment. In this embodiment, the control unit turns on switch element 11(Qmain) after switch element 1134(Qsub) has been turned on. Furthermore, the same control turns off switch element 11(Qmain) either after or simultaneously with switch element 1134(Qsub).

[0222] In the graph shown in Figure 25, the horizontal axis represents time (t), and the vertical axis represents the level of each waveform. Figure 25(A) shows waveforms 3011 representing the ON and OFF states of the gate of the switch element 1134 (Qsub). Figure 25(B) shows waveforms 3012 representing the ON and OFF states of the gate of the switch element 11 (Qmain).

[0223] Figure 25(C) shows the waveform 3013 of the current flowing through the switch element 1134 (Qsub). Figure 25(D) shows the waveform 3014 of the current flowing through the excitation inductor Lm in the equivalent circuit of the primary winding 1131 (Np) side, converted from the secondary winding 1132 (Ns) side. Figure 25(D) also shows the waveform 3015 of the current flowing through the switch element 11(Qmain). Furthermore, Figure 25(D) shows the waveforms of the input current Iin for modes 2 and 3.

[0224] Figure 25(E) shows the waveform 3016 of the voltage across the excitation inductor Lm in the equivalent circuit of the primary winding 1131 (Np) side, converted from the secondary winding 1132 (Ns) side. Figure 25(F) shows the waveform 3017 of the voltage applied to the switch element 1134 (Qsub). Figure 25(G) shows the waveform 3018 of the voltage applied to the switch element 11(Qmain).

[0225] In the power converter 1001, the state transitions sequentially from mode 1 to mode 6 according to the passage of time, and after being in mode 6, it returns to mode 1 again.

[0226] As described above, in the power converters 1001 to 1004 according to this embodiment, the number of components can be further reduced when the ZVS condition is satisfied even if Nt / Ns ≤ 0, thanks to the quasi-ZVS assist circuit. In the power converters 1001 to 1004 according to this embodiment, the degree of freedom in selecting devices for the quasi-ZVS assist circuit is increased, and the reset period of the resonant current in the quasi-ZVS assist circuit is shortened, thereby reducing the turn-off loss of the main switch.

[0227] In addition, the quasi-ZVS assist circuit operates in a way that does not generate a charging current for the auxiliary capacitor (Cs) in mode 5. The quasi-ZVS assist circuit according to this embodiment can be applied, for example, to a boost converter, buck converter, buck-boost converter, or flyback converter in which the primary winding (Np) of a coupled inductor is connected for the purpose of smoothing, boosting, or bucking.

[0228] (Example configuration of a power conversion device consisting of an AC converter equipped with a quasi-ZVS assist circuit) Referring to Figures 26 and 27, an example configuration of a power conversion device consisting of an AC converter equipped with a quasi-ZVS assist circuit will be described. Figures 26 and 27 show the case where the power conversion device consists of a boost converter.

[0229] <Semi-ZVS assist circuit of a power converter shown in the example in Figure 26> Figure 26 shows an example of the circuit configuration of a quasi-ZVS assist circuit according to the embodiment. In the example shown in Figure 26, the main circuit and control circuit are not shown. Here, the main circuit is the same as the main circuit shown in Figure 14.

[0230] The quasi-ZVS assist circuit comprises a coupled inductor with a primary winding 541 (Np), secondary windings 1311 (Ns+) and 1312 (Ns-), a diode 1313 (Ds1+), a switch element 1314 (Qsub+) made of a MOS-type FET, a diode 1315 (Ds1-), and a switch element 1316 (Qsub-) made of a MOS-type FET. Here, the primary winding 541(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit. Note that in the example shown in Figure 26, the primary winding 541(Np) is not shown.

[0231] One end of the secondary winding 1312 is connected to the anode of the diode 1315. The cathode of diode 1315 is connected to the drain of switch element 1316. The other end of the secondary winding 1312 is connected to one end of the secondary winding 1311, the source of the switch element 1316 is connected to the source of the switch element 1314. The other end of the secondary winding 1311 is connected to the anode of the diode 1313. The cathode of diode 1313 is connected to the drain of switch element 1314.

[0232] <Power converter related to the example in Figure 27> Figure 27 shows an example of the circuit configuration of a power converter 1301 equipped with a quasi-ZVS assist circuit according to the embodiment. In the example shown in Figure 27, the control circuit is not shown.

[0233] The power converter 1301 comprises a main circuit and a quasi-ZVS assist circuit. The main circuit is the same as the main circuit in the example shown in Figure 14, and all circuit elements of the main circuit are shown using the same reference numerals, except for the primary winding 1331(Np) of the coupled inductor. Furthermore, Figure 27 shows a power supply 523 similar to the one shown in Figure 14.

[0234] The quasi-ZVS assist circuit comprises a primary winding 1331 (Np) and a secondary winding 1332 (Ns) of a coupled inductor, a switching element 1333 (Qsub+) made of a MOS-type FET, and a switching element 1334 (Qsub-) made of a MOS-type FET. Here, the primary winding 1331(Np) of the coupled inductor can be considered as not being included in the quasi-ZVS assist circuit. The arrangement of the primary winding 1331 is the same as that of the primary winding 541 shown in Figure 14.

[0235] One end of the secondary winding 1332 is connected to the drain of the switch element 1334. The other end of the secondary winding 1332 is connected to the drain of the switch element 1333. The source of switch element 1333 is connected to the source of switch element 1334.

[0236] In the example shown in Figure 27, the switch element 1333 (Qsub+) is composed of a MOSFET that does not have a reverse blocking function, and it can be assumed that there is a rectifier element (Ds1-) connected in parallel with its switching section. Similarly, in the example in Figure 27, the switching element 1334 (Qsub-) is composed of a MOSFET that does not have a reverse blocking function, and it can be assumed that there is a rectifier element (Ds1+) connected in parallel with its switching section. As an example of another configuration, other components may be used as components for one or both of the rectifier elements (Ds1-) and (Ds1+).

[0237] Here, the potential of the source of the switching elements (Qsub+, Qsub-) in the quasi-assist circuit may be connected to the potential at any point. Generally, the potentials used in this case are the potential of the first output terminal T61 (the potential at point B1 in Figure 27), the potential of the drain of switch element 511 and the potential of the source of switch element 512 (the potential at point B2 in Figure 27), or the potential of the cathode of half-wave rectifier diode 513 and the potential of the anode of half-wave rectifier diode 514 (the potential at point B3 in Figure 27). Note that points B1, B2, and B3 in Figure 27 are shown for illustrative purposes only and do not limit the circuit configuration of the power converter 1301.

[0238] In the examples shown in Figures 26 and 27, a quasi-ZVS assist circuit is applied to a boost converter. However, the quasi-ZVS assist circuit may also be applied to a buck converter, a buck-boost converter, or a flyback converter.

[0239] <Example of operation of a quasi-ZVS assist circuit using current suction in synchronous rectification> Referring to Figures 28 to 29, an example of the operation of the quasi-ZVS assist circuit related to the example in Figure 27 will be explained. This section describes the ZVS assist operation (SR-ZVS assist operation) by current suction of synchronous current in a half-bridge configuration such as a totem pole PFC.

[0240] <Equivalent circuit related to the example in Figure 28> Figure 28 shows an example of an equivalent circuit 1401 of the circuit configuration of a power converter 1301 consisting of an AC converter equipped with a quasi-ZVS assist circuit according to the embodiment. Equivalent circuit 1401 is the equivalent circuit when Vi > 0.

[0241] The equivalent circuit 1401 shows the first output terminal T61, the second output terminal T62, and the power supply 523, as well as the switch element 1411 (Qmain) made of a MOS type FET, the switch element 1412 (QSR) made of a MOS type FET, the excitation inductor 1421 (Lm), the inductor 1422 (Lks), the switch element 1423 (Qsub+) made of a MOS type FET, and the switch element 1424 (Qsub-) made of a MOS type FET. In mode S, a half-wave rectifier diode 1431 is provided, or it is not provided, with the forward direction from the first output terminal T61 to the power supply 523. Furthermore, if the half-wave rectifier diode 1431 in the totem pole PFC is turned off by reverse current and interferes with the resonant operation, interference with the resonant operation can be prevented by connecting a capacitive component in parallel with the half-wave rectifier diode 1431 (corresponding to half-wave rectifier diodes 513 and 514 in the example of Figure 27). Alternatively, interference with the resonant operation can also be prevented by replacing the half-wave rectifier diodes 513 and 514 in the example of Figure 27 with a switching element such as an FET, so that a reverse current can flow through the half-wave rectifier diode 1431 (corresponding to half-wave rectifier diodes 513 and 514 in the example of Figure 27).

[0242] Figure 28 shows the current flow in a predetermined mode (referred to as mode S for convenience of explanation). In the example shown in Figure 28, the switch element 1412 (QSR), which is responsible for the recirculation operation of the excitation current of the primary winding (Np), is controlled to perform a paired on / off operation (synchronous rectification operation) with the switch element 1411 (Qmain) with a short-circuit prevention period in place.

[0243] Referring to Figure 29, an example of the operation performed in the power converter 1301 (equivalent circuit 1401) shown in Figure 28 will be explained.

[0244] Figure 29 shows an example of a waveform in a power converter 1301 (equivalent circuit 1401) consisting of an AC converter equipped with a quasi-ZVS assist circuit according to the embodiment. In this embodiment, the control unit turns on the switch element 1423 (Qsub+) and then turns on the switch element 1411 (Qmain). Furthermore, the same control turns off the switch element 1423 (Qsub+) and then, simultaneously, turns off the switch element 1411 (Qmain).

[0245] In the graph shown in Figure 29, the horizontal axis represents time (t), and the vertical axis represents the level of each waveform. Figure 29(A) shows waveforms 3111 representing the ON and OFF states of the gate of the switch element 1423 (Qsub+). Figure 29(B) shows waveforms 3112 representing the ON and OFF states of the gate of the switch element 1411 (Qmain). Figure 29(C) shows waveforms 3113 representing the ON and OFF states of the gate of the switch element 1412(QSR).

[0246] Figure 29(D) shows the waveform 3114 of the current flowing through the switch element 1423 (Qsub+). Figure 29(E) shows the waveform 3115 of the current flowing through the excitation inductor 1421 (Lm). Figure 29(E) also shows the waveform 3116 of the current flowing through the switch element 1411(Qmain). Furthermore, Figure 29(E) shows the waveforms of the input current Iin for modes 2, S, and 3.

[0247] Figure 29(F) shows the waveform 3117 of the voltage applied to the excitation inductor 1421 (Lm). Figure 29(G) shows the waveform 3118 of the voltage applied to the switch element 1423 (Qsub+). Figure 29(H) shows the waveform 3119 of the voltage applied to the switch element 1411(Qmain).

[0248] In the power converter 1301 (equivalent circuit 1401), the state transitions sequentially from mode 1 to mode 2, then to mode S, then from mode 3 to mode 6, and after mode 6, it returns to mode 1 again.

[0249] In the example shown in Figure 29, after switch element 1423 (Qsub+) is turned on, when the current in switch element 1412 (QSR) becomes an arbitrary negative current value, turning switch element 1412 (QSR) off results in mode 3. In mode 3, after the transition time tb has elapsed for the voltage (V Qmain) across switch element 1411 (Qmain) to transition to zero voltage, the turn-on of switch element 1411 (Qmain) becomes ZVS-on, and the system transitions to mode 4. Subsequently, in mode 6, when switch element 1411 (Qmain) is turned off, after the charging and discharging period tc of the capacitive component in parallel with the switch has elapsed, switch element 1412 (QSR) enters freewheeling operation, and the system returns to mode 1. In mode 1, turning switch element 1412 (QSR) on enables a reduction in conduction loss due to synchronous rectification.

[0250] The power converter 1301 (equivalent circuit 1401) enables ZVS operation over the entire input voltage range Vi, including Vi > Vo / 2. In the power converter 1301 (equivalent circuit 1401), even if Vi > Vo / 2, valley switching occurs and soft recovery operation is obtained. When the input voltage (Vi) is high, such as Vi > Vo / 2, the PFC loss is smaller than when the input voltage (Vi) is low. Also, as with CRM-PFC, the switching frequency does not increase when the input voltage (Vi) is high.

[0251] In the example shown in Figure 27, the half-wave rectifier diodes 513 and 514 in the main circuit may be replaced with switching elements such as MOS-type FETs, in which case a bidirectional converter can be realized.

[0252] In the examples shown in Figures 28 and 29, a quasi-ZVS assist circuit is applied to a boost converter. However, the quasi-ZVS assist circuit may also be applied to a buck converter, a buck-boost converter, or a flyback converter.

[0253] <Power converter device as shown in Figure 30> Figure 30 shows an example of the circuit configuration of a power converter 1501 equipped with a quasi-ZVS assist circuit according to the embodiment. Figure 30 shows an example where a quasi-ZVS assist circuit is applied to a bridgeless PFC of an AC switch. In the example shown in Figure 30, the control circuit is not shown.

[0254] The power converter 1501 comprises a main circuit and a quasi-ZVS assist circuit. The main circuit comprises four switching elements 1511 to 1514 made of MOS-type FETs, a capacitor 1515 (Co) which is an output capacitor, two switching elements 1516 to 1517 made of MOS-type FETs, and a primary winding 1541 (Np) of a coupled inductor. Figure 30 also shows an AC power supply 1523. Here, power supply 1523 may be, for example, a commercial AC power supply.

[0255] For the sake of explanation, in the power converter 1501, the two output terminals on the side to which the load (not shown in the figure) is connected will be referred to as the first output terminal T101 and the second output terminal T102. In the example in Figure 30, the first output terminal T101 is the ground (GND) side, and the second output terminal T102 is the positive (+) side.

[0256] The first output terminal T101 is connected to the source of switch element 1511, the source of switch element 1513, and one end of capacitor 1515. The second output terminal T102 is connected to the drain of switch element 1512, the drain of switch element 1514, and the other end of capacitor 1515. The drain of switch element 1511 is connected to the source of switch element 1512, the drain of switch element 1516 is connected to one end of power supply 1523. The other end of power supply 1523 is connected to one end of primary winding 1541. The other end of the primary winding 1541 is connected to the drain of switch element 1513, the source of switch element 1514, and the drain of switch element 1517. The source of switch element 1516 is connected to the source of switch element 1517.

[0257] The quasi-ZVS assist circuit comprises a primary winding 1541 (Np) and a secondary winding 1542 (Ns) of a coupled inductor, a switching element 1543 (Qsub+) made of a MOS-type FET, and a switching element 1544 (Qsub-) made of a MOS-type FET. Here, the primary winding 1541(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit. The configuration of the quasi-ZVS assist circuit is the same as in the example shown in Figure 27.

[0258] In addition, as with the example in Figure 27, the potentials of the switching elements (Qsub+, Qsub-) of the quasi-ZVS assist circuit may be connected to any potential in the example in Figure 30. Generally, in the example shown in Figure 30, the potential in question is one of the source potentials of the FETs in the power circuit.

[0259] <Power converter device as shown in the example in Figure 31> Figure 31(A) shows an example of the circuit configuration of a power converter 1601 equipped with a quasi-ZVS assist circuit according to the embodiment. The example in Figure 31(A) shows an example of applying a quasi-ZVS assist circuit to an inverter. In the example shown in Figure 31(A), the control circuit is not shown.

[0260] The power converter 1601 comprises a main circuit and a quasi-ZVS assist circuit. The main circuit comprises four switching elements 1611-1614, each consisting of a MOS-type FET, and a primary winding 1641(Np) of a coupled inductor. Figure 31(A) also shows a DC power supply 1631 and an AC power supply 1623.

[0261] The drain of switch element 1613, the source of switch element 1614, and one end of the primary winding 1641 are connected. The other end of the primary winding 1641 is connected to one end of the power supply 1623. The drain of switch element 1611 is connected to the source of switch element 1612, and the other end of power supply 1623 is connected to it. The source of switch element 1613, the source of switch element 1611, and one end of power supply 1631 are connected. The drain of switch element 1614 is connected to the drain of switch element 1612, and the other end of power supply 1631 is connected to it.

[0262] The quasi-ZVS assist circuit comprises a primary winding 1641 (Np) and a secondary winding 1642 (Ns) of a coupled inductor, a switching element 1643 (Qsub+) made of a MOS-type FET, and a switching element 1644 (Qsub-) made of a MOS-type FET. Here, the primary winding 1641(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit. The configuration of the quasi-ZVS assist circuit is the same as in the example shown in Figure 27.

[0263] In the example shown in Figure 31(A), the potentials of the switch elements (Qsub+, Qsub-) of the quasi-ZVS assist circuit are such that the sources of switch element 1643 and switch element 1644 are connected to the sources of switch element 1613 and switch element 1611 (as well as one end of power supply 1631).

[0264] Here, the power supply 1623 may be replaced with the load circuit shown in Figure 31(B). The circuit shown in Figure 31(B) is a parallel circuit of resistor 1671 and capacitor 1672.

[0265] <Power converter device as shown in the example in Figure 32> Figure 32 shows an example of the circuit configuration of a power converter 1701 equipped with a quasi-ZVS assist circuit according to the embodiment. The example in Figure 32 shows an example of applying a quasi-ZVS assist circuit to an H-bridge buck-boost converter. In the example shown in Figure 31, the control circuit is not shown.

[0266] The power converter 1701 comprises a main circuit and a quasi-ZVS assist circuit. The main circuit comprises four switching elements 1711-1714 made of MOS-type FETs, a capacitor 1715(Co) which is an output capacitor, and a primary winding 1741(Np) of a coupled inductor. Figure 31 also shows the DC power supply 1731.

[0267] For the sake of explanation, in the power converter 1701, the two output terminals on the side to which the load (not shown) is connected will be referred to as the first output terminal T121 and the second output terminal T122. In the example in Figure 32, the first output terminal T121 is the ground (GND) side, and the second output terminal T122 is the positive (+) side.

[0268] The first output terminal T121 is connected to the source of switch element 1711, the source of switch element 1713, one end of capacitor 1715, and one end of power supply 1731. The second output terminal T122 is connected to the drain of the switch element 1712 and to the other end of the capacitor 1715. The other end of power supply 1731 is connected to the drain of switch element 1714. The drain of switch element 1713, the source of switch element 1714, and one end of the primary winding 1741 are connected. The other end of the primary winding 1741 is connected to the drain of the switch element 1711 and the source of the switch element 1712.

[0269] The quasi-ZVS assist circuit comprises a primary winding 1741 (Np) and a secondary winding 1742 (Ns) of a coupled inductor, a switching element 1743 (Qsub+) made of a MOS-type FET, and a switching element 1744 (Qsub-) made of a MOS-type FET. Here, the primary winding 1741(Np) of the coupled inductor can be considered as not being included in the quasi-ZVS assist circuit. The configuration of the quasi-ZVS assist circuit is the same as in the example shown in Figure 27.

[0270] In the example shown in Figure 32, the sources of switch element 1743 and switch element 1744 are connected to the sources of switch element 1711 and switch element 1713 (as well as the first output terminal T121 and one end of the power supply 1731) as potentials of the switch elements (Qsub+, Qsub-) of the quasi-ZVS assist circuit.

[0271] (Example configuration of the control unit (drive circuit) of a quasi-ZVS assist circuit) The configuration example of the control unit (drive circuit) of the quasi-ZVS assist circuit is the same as the configuration example of the control unit (drive circuit) shown in Figures 18 to 20, but differs in that the quasi-ZVS assist circuit does not use an auxiliary capacitor (Cs). In the example shown in Figure 18, when applied to a quasi-ZVS assist circuit, the tertiary winding 52, diode 53, and capacitor 37 are not provided, so it is thought that the input terminal of the arithmetic unit 612 will be short-circuited. In this case, the potential at the negative input terminal of the comparator 613 will be 0[V], and the on / off timing of the main switch element (Qmain) will be controlled based on the comparison result of the comparator 613.

[0272] Note that the potential at the negative input terminal of comparator 613 does not necessarily have to be 0[V]. For example, a configuration in which an offset voltage with a noise margin set at 0[V] is applied to the negative input terminal of comparator 613 may be used. Here, the offset voltage may be set considering the input voltage range of the comparator 613, for example, an offset voltage of about 0[V] to 1[V] may be set.

[0273] Below, we will provide further configuration examples for ZVS and quasi-ZVS. <Control unit of the ZVS assist circuit in the example shown in Figure 33> Figure 33 shows an example of the configuration of the control unit (drive circuit) of the ZVS assist circuit according to the embodiment. The example in Figure 33 is, in general terms, an example where the order of AND and OR is reversed in the example in Figure 18, and a D-type flip-flop with an asynchronous clear terminal is used as a substitute for AND. In the example shown in Figure 33, the flip-flop and latch functions prevent double pulses from reaching the gate of the main switch element 11 (Qmain).

[0274] Figure 33 shows a power converter 4001 equipped with a control unit with a different configuration from the control unit of the power converter 601 shown in Figure 18. In the example in Figure 33, the same reference numerals are used for circuit components that are the same as those shown in Figure 18. Figure 33 also shows the power supply 23. The first output terminal T1 is connected to the ground terminal G1.

[0275] Here, in the example in Figure 33, instead of winding 51, tertiary winding 52, diode 53, diode 34, switching element 35, and capacitor 37 as in the example in Figure 18, a configuration is shown that includes winding 4051, tertiary winding 4052, diode 4053, diode 4034, switching element 4035, and capacitor 4037, but these are essentially the same ZVS assist circuits.

[0276] The control unit comprises an auxiliary winding 4111 (Nt':NZCD), an arithmetic unit 4112, a comparator 4113, an on-delay circuit 4116, an OR 4117, an off-delay circuit 4118, and a D-type flip-flop (D-FF) 4119 with an asynchronous clear terminal. In the example shown in Figure 33, an auxiliary winding 4111 is provided as a component corresponding to the auxiliary winding 611 in the example shown in Figure 18.

[0277] One end of the auxiliary winding 4111 is connected to the first output terminal T1, and the other end of the auxiliary winding 4111 is connected to the + input terminal of the comparator 4113. Furthermore, a diode (not shown in Figure 33) may or may not be provided between the auxiliary winding 4111 and the + input terminal of the comparator 4113, such that the direction from the auxiliary winding 4111 to the comparator 4113 is forward.

[0278] The arithmetic unit 4112 is connected to the point between capacitor 4037 and the tertiary winding 4052 (corresponding to the other end of capacitor 37 in the example in Figure 18), and outputs the voltage across capacitor 4037 multiplied by K to the - input terminal of comparator 4113. Comparator 4113 outputs values ​​to OR4117 corresponding to the inputs at the + and - terminals. Specifically, comparator 4113 outputs a value of 1 if the input at the + terminal is greater than the input at the - terminal, and outputs a value of 0 if the input at the + terminal is less than the input at the - terminal.

[0279] In this embodiment, a control IC (not shown) outputs a PWM signal. This PWM signal is output to the gate of the auxiliary switch element 4035 (Qsub), the on-delay circuit 4116, the off-delay circuit 4118, and the D terminal (input terminal) of the D-type flip-flop 4119.

[0280] The on-delay circuit 4116 receives a PWM signal and outputs the result of the on-delay operation to the OR4117. The OR4117 receives the output from the comparator 4113 and the output from the on-delay circuit 4116, and outputs these logic results to the clock terminal of the D-type flip-flop 4119.

[0281] The off-delay circuit 4118 receives a PWM signal and outputs the result of the off-delay operation to the asynchronous clear terminal (negative logic R) of the D-type flip-flop 4119. The D-type flip-flop 4119 outputs the result based on the input to the D terminal, the clock terminal, and the asynchronous clear terminal (negative logic R) from the Q terminal to the gate of the main switch element 11 (Qmain).

[0282] In the example shown in Figure 33, the PWM signal output from the PFC control IC is input to the D-type flip-flop 4119. In the example shown in Figure 33, the rising edge of the zero-current detection ZCD comparator (comparator 4113 in the example shown in Figure 33) using the NZCD tap (the tap of the auxiliary winding 4111 in the example shown in Figure 33) is input to the D-type flip-flop 4119, thereby turning on the main switch element 11 (Qmain) in ZVS mode while simultaneously achieving a latching function.

[0283] However, at startup, regardless of the zero-current detection ZCD, it is necessary to force the main switch element 11 (Qmain) to turn on. Therefore, the OR signal of the output of the ZCD comparator and the output of the on-delay circuit 4116 is connected to the edge input of the D-type flip-flop 4119 to implement a latch function and a forced-on function. In addition, the off-delay circuit 4118 is connected to the asynchronous clear terminal of the D-type flip-flop 4119 to control the off timing of the main switch element 11 (Qmain), thereby causing the auxiliary switch element 4035 (Qsub) to turn off before the main switch element 11 (Qmain). Thus, the adjustment elements in this circuit configuration are the delay time of the PWM signal by the on-delay circuit 4116, the delay time of the PWM signal by the off-delay circuit 4118, and the ZCD comparator.

[0284] <Control unit of the quasi-ZVS assist circuit in the example shown in Figure 34> Figure 34 shows an example of the configuration of the control unit (drive circuit) of the quasi-ZVS assist circuit according to the embodiment. Figure 34 shows a power converter 4201 having a configuration similar to the power converter 1001 shown in Figure 21(A), and equipped with a control unit substantially similar to the example in Figure 18. In the example in Figure 34, the same reference numerals are used for circuit components similar to those shown in Figure 21(A) or Figure 18. Figure 34 also shows the power supply 21. The first output terminal T1 is connected to the ground terminal G1.

[0285] Here, in the example of Figure 34, instead of the primary winding 1131, secondary winding 1132, diode 1133, and switch element 1134 in the example of Figure 21(A), a configuration is shown that includes a primary winding 4231, secondary winding 4232, diode 4233, and switch element 4234. However, these are essentially similar quasi-ZVS assist circuits.

[0286] The control unit comprises an auxiliary winding 611, a comparator 613, an AND 614, an AND 615, an on-delay circuit 616, an OR 617, and an offset power supply 4251. Furthermore, diode 621 may or may not be provided. In this embodiment, a control IC (not shown) outputs an enable signal and a PWM signal.

[0287] In this example, the configuration of the control unit in Figure 34 differs from the configuration of the control unit in Figure 18 in that the input to the - input terminal of the comparator 613 is different. In the example shown in Figure 34, the voltage from the offset power supply 4251 is output to the negative input terminal of the comparator 613. The offset power supply 4251 outputs an offset voltage of 0[V] or higher.

[0288] <Control unit of the quasi-ZVS assist circuit shown in the example in Figure 35> Figure 35 shows an example of the configuration of the control unit (drive circuit) of the quasi-ZVS assist circuit according to the embodiment. The example in Figure 35 is, in general terms, an example where the order of AND and OR is reversed in the example in Figure 34, and a D-type flip-flop with an asynchronous clear terminal is used as a substitute for AND. In the example shown in Figure 35, the flip-flop and latch functions prevent double pulses from reaching the gate of the main switch element 11 (Qmain).

[0289] Figure 35 shows a power converter 4301 with a control unit configuration different from that of the power converter 4201 shown in Figure 34, and which is substantially the same as the example in Figure 33. In the example in Figure 35, the same reference numerals are used for circuit components that are the same as those shown in Figure 34 or Figure 33. Figure 35 also shows the power supply 21. The first output terminal T1 is connected to the ground terminal G1.

[0290] Here, in the example shown in Figure 35, instead of the primary winding 4231, secondary winding 4232, diode 4233, and switch element 4234 as in the example in Figure 34, a configuration is shown with primary winding 4331, secondary winding 4332, diode 4333, and switch element 4334. However, these are essentially similar quasi-ZVS assist circuits.

[0291] The control unit comprises an auxiliary winding 4111, a comparator 4113, an on-delay circuit 4116, an OR 4117, an off-delay circuit 4118, a D-type flip-flop (D-FF) 4119 with an asynchronous clear terminal, and an offset power supply 4351. Furthermore, a diode (not shown in Figure 35) may or may not be provided between the auxiliary winding 4111 and the + input terminal of the comparator 4113, with the direction from the auxiliary winding 4111 to the comparator 4113 being the forward direction. In this embodiment, a control IC (not shown) outputs a PWM signal.

[0292] In this example, the configuration of the control unit in Figure 35 differs from the configuration of the control unit in Figure 33 in that the input to the - input terminal of the comparator 4113 is different. In the example shown in Figure 35, the voltage from the offset power supply 4351 is output to the negative input terminal of the comparator 4113. The offset power supply 4351 outputs an offset voltage of 0[V] or higher.

[0293] <Control unit of the quasi-ZVS assist circuit shown in the example in Figure 36> Figure 36 shows an example of the configuration of the control unit (drive circuit) of the quasi-ZVS assist circuit according to the embodiment. Here, Figure 28 shows the equivalent circuit 1401 in the case of Vi > 0 (the period when the polarity of Vi is positive) in the example of Figure 27, and explains an example of operation. Figure 36 shows an example of the control circuit when the operation described in the example in Figure 28 is being performed.

[0294] The power converter 4501 shown in Figure 36 will be described below. The power converter 4501 includes a first output terminal T211, a second output terminal T212, a main switch element 4511 (Qmain), a switch element 4512 (QSR), a capacitor 4515, a primary winding 4531, a secondary winding 4532, an auxiliary switch element 4533 (Qsub), and a diode 4534. These correspond to the first output terminal T61, the second output terminal T62, the main switch element 511 (QSR-), the switch element 512 (QSR+), the capacitor 515, the primary winding 1331, the secondary winding 1332, the auxiliary switch element 1333 (Qsub+), and the auxiliary switch element 1334 (Qsub-) in the example in Figure 27, respectively. Furthermore, Figure 36 shows power supply 4523. Note that the first output terminal T211 is connected to the ground terminal G1.

[0295] The control unit comprises an auxiliary winding 4611 (Nt':NZCD), an offset power supply 4612, a comparator 4613, an AND gate 4614, an on-delay circuit 4615, an OR gate 4616, a NOT gate 4617, an on-delay circuit (SR) 4618, an AND gate 4619, a PWM control unit 4711, a detection unit 4721, and a circuit unit 4731. The AND4614 takes an enable signal and a PWM signal as input and outputs the logic results of these signals to the gate of an auxiliary switch element 4533 (Qsub).

[0296] In this embodiment, the control IC outputs an enable signal and a PWM signal. In the example shown in Figure 36, the PWM control unit 4711 that constitutes the control IC is shown. The PWM control unit 4711 has the function of outputting a PWM signal. The function of outputting an enable signal may be provided, for example, in the PWM control unit 4711, or it may be provided separately from the PWM control unit 4711. The enable signal controls whether or not ZVS assist is enabled. For example, the enable signal can be used to disable ZVS assist operation under certain conditions, adding a function to reduce reactive current loss and prevent surge voltage to the auxiliary switch element 4533 (Qsub).

[0297] One end of the auxiliary winding 4611 is connected to the first output terminal T211, and the other end of the auxiliary winding 4611 is connected to the + input terminal of the comparator 4613. Furthermore, a diode (not shown in Figure 36) may or may not be provided between the auxiliary winding 4611 and the + input terminal of the comparator 4613, such that the direction from the auxiliary winding 4611 to the comparator 4613 is forward.

[0298] The offset power supply 4612 outputs an offset voltage of 0[V] or greater to the negative input terminal of the comparator 4613. Comparator 4613 outputs values ​​to OR4616 corresponding to the inputs at the + and - terminals. Specifically, comparator 4613 outputs a value of 1 if the input at the + terminal is greater than the input at the - terminal, and outputs a value of 0 if the input at the + terminal is less than the input at the - terminal.

[0299] The PWM control unit 4711 outputs the PWM signal to AND 4614, the on-delay circuit 4615, and AND 4619, respectively. Here, the detection unit 4721 detects the current (ILSENS) flowing on the side of the first output terminal T211 of the power supply 4523 and outputs the detection result to the PWM control unit 4711. The PWM control unit 4711 outputs a PWM signal based on the detection result of the current.

[0300] Furthermore, the PWM control unit 4711 outputs a voltage (gate SR signal) for controlling the switch element 4512 (QSR) to the gate of the switch element 4512 (QSR) via the circuit unit 4731. The voltage in question (the gate SR signal) is also output from the PWM control unit 4711 to the NOT4617. Note that the circuit section 4731 may be any circuit. For example, circuit 4731 has the function of driving QSR gate inputs with different GND potentials. Circuit 4731 may be any circuit, such as an isolated gate driver or a gate driver with a bootstrap circuit.

[0301] The on-delay circuit 4615 delays the PWM signal and outputs it to the OR4616. The OR4616 receives the output from comparator 4613 and the output from on-delay circuit 4615, and outputs the result of these logics to AND4619. NOT4617 inverts (reverses the positive and negative) the voltage from the PWM control unit 4711 and outputs it to the on-delay circuit (SR) 4618. The on-delay circuit (SR) 4618 delays the signal (e.g., voltage) input from the NOT 4617 and outputs it to the AND 4619. The AND4619 receives the PWM signal, the output from the OR4616, and the output from the on-delay circuit (SR)4618, and outputs the result of these logics to the gate of the main switch element 4511 (Qmain).

[0302] Here, Figures 28 and 29 illustrate an example of operation including a predetermined mode (mode S). In the control unit shown in the example in Figure 36, the gate voltage to the main switch element 4511 (Qmain) (the signal for Qmain) and the gate voltage to the switch element 4512 (QSR) (the signal for QSR) can be controlled so that the switch element 4512 (QSR), which is responsible for the recirculation operation of the excitation current of the primary winding, performs a paired on / off operation (synchronous rectification operation) with a short-circuit prevention period in place with the main switch element 4511 (Qmain).

[0303] In the example in Figure 36, the ZVS on-timing of the main switch is achieved by an NZCD detection comparator (comparator 4613 in the example in Figure 28) in the assist operation related to Figure 28. In the example shown in Figure 36, a 3-input AND gate is used as the AND gate 4619 that outputs the gate voltage (Qmain signal) to the main switch element 4511 (Qmain) in order to provide a short-circuit protection period. The three inputs are the PWM signal (gate main signal), the output from OR gate 4616 (NZCD detection comparator signal), and the output signal from the on-delay circuit (SR) 4618 (the inverted gate SR signal with a short-circuit protection period (tdead_SR) added).

[0304] (Explanation of Figures 37-39) <Power converter including a quasi-ZVS assist circuit as shown in the example in Figure 37> Figure 37 shows an example configuration of a power converter 5001 including a quasi-ZVS assist circuit according to an embodiment. The control unit of the power converter 5001 will be explained using Figure 39.

[0305] The power converter 5001 shown in Figure 37 will now be described. The power converter 5001 includes a first output terminal T231, a second output terminal T232, a main switch element 5111 (Qmain+), a switch element 5112 (Qmain-), a capacitor 5113, a primary winding 5131, secondary windings 5151 and 5152, a diode 5153, a sub switch element 5154 (Qsub+), a diode 5155, and a sub switch element 5156 (Qsub-). Furthermore, Figure 37 shows the power supply 5123. Note that the first output terminal T231 is connected to the ground terminal G1.

[0306] Here, the arrangement of the first output terminal T231, the second output terminal T232, the switch element 5111 (Qmain+), the switch element 5112 (Qmain-), the capacitor 5113, the primary winding 5131, and the power supply 5123 is the same as the arrangement of the first output terminal T211, the second output terminal T212, the switch element 4511 (Qmain), the switch element 4512 (QSR), the capacitor 4515, the primary winding 4531, and the power supply 4523 in the example of Figure 36.

[0307] Furthermore, the arrangement of secondary windings 5151 and 5152, diode 5153, switch element 5154 (Qsub+), diode 5155, and switch element 5156 (Qsub-) is the same as the arrangement of secondary windings 1311 and 1312, diode 1313, switch element 1314 (Qsub+), diode 1315, and switch element 1316 (Qsub-) in the example of Figure 26. In the example shown in Figure 37, the source of switch element 5154 (Qsub+), the source of switch element 5156 (Qsub-), and the connection point between secondary winding 5151 and secondary winding 5152 are connected to the first output terminal T231.

[0308] Figure 37 shows the components of the control unit, including the auxiliary winding 5211 (Nt':NZCD), diode 5212, diode 5213, detection unit 5221, and circuit unit 5231. Here, the anodes of diode 5212 and diode 5213 are connected to the first output terminal T231. An auxiliary winding 5211 is provided between the cathode of diode 5212 and the cathode of diode 5213. In the control unit of the power converter 5001, the signal from the cathode side of diode 5212 (e.g., voltage signal) is extracted as a P signal, and the signal from the cathode side of diode 5213 (e.g., voltage signal) is extracted as an N signal.

[0309] The detection unit 5221 detects the current flowing through the same location as the detection unit 4721 in the example shown in Figure 36. Circuit section 5231 is located on the gate side of the switch element 5112 (Qmain-), similar to circuit section 4731 in the example in Figure 36.

[0310] <Power converter including a quasi-ZVS assist circuit as shown in the example in Figure 38> Figure 38 shows an example configuration of a power converter 5301 including a quasi-ZVS assist circuit according to an embodiment. The control unit of the power converter 5301 will be explained using Figure 39.

[0311] The power converter 5301 shown in Figure 38 will now be described. Here, the configuration of the power converter 5301 is the same as that of the power converter 5001 in the example of Figure 37, except that the quasi-ZVS circuit portion is different. For this reason, in Figure 38, components that are the same as those shown in Figure 37 are given the same reference numerals. In the example shown in Figure 38, instead of the circuit portions of secondary windings 5151 and 5152, diode 5153, switch element 5154 (Qsub+), diode 5155, and switch element 5156 (Qsub-) in the example shown in Figure 37, the example includes secondary winding 5332, sub-switch element 5333 (Qsub+), and sub-switch element 5334 (Qsub-).

[0312] The source of the sub-switch element 5333 (Qsub+) and the source of the sub-switch element 5334 (Qsub-) are connected to the first output terminal T231. A secondary winding 5332 is provided between the drain of the sub-switch element 5333 (Qsub+) and the drain of the sub-switch element 5334 (Qsub-).

[0313] <Control unit of the quasi-ZVS assist circuit shown in the example in Figure 39> Figure 39 shows an example of the configuration of the control unit (drive circuit) of the quasi-ZVS assist circuit according to the embodiment. The control unit shown in the example in Figure 39 is applicable to both the power converter 5001 shown in Figure 37 and the power converter 5301 shown in Figure 38, and will be described together here.

[0314] The control unit comprises an auxiliary winding 5211, two diodes 5212 and 5213, a detection unit 5221, a circuit unit 5231, and a PWM control unit 5711. The control unit also includes an offset power supply 5512, a comparator 5513, an AND gate 5514, an on-delay circuit 5515, an OR gate 5516, a NOT gate 5517, an on-delay circuit (SR) 5518, and an AND gate 5519. The control unit also includes an offset power supply 5612, a comparator 5613, an AND gate 5614, an on-delay circuit 5615, an OR gate 5616, a NOT gate 5617, an on-delay circuit (SR) 5618, and an AND gate 5619. Note that the on-delay circuit (SR) 5518 has a different delay time than the on-delay circuit 5515. Furthermore, the on-delay circuit (SR) 5618 has a different delay time than the on-delay circuit 5615.

[0315] In this embodiment, the control IC outputs an enable signal and a PWM signal. In the example shown in Figure 39, the PWM control unit 5711 that constitutes the control IC is shown. The PWM control unit 5711 has the function of outputting a PWM signal. The function of outputting an enable signal may be provided, for example, in the PWM control unit 5711, or it may be provided separately from the PWM control unit 5711. The enable signal controls whether or not ZVS assist is enabled. For example, the enable signal can be used to disable ZVS assist operation under certain conditions, adding a function to reduce reactive current loss and prevent surge voltage to the auxiliary switch element (Qsub). In the example shown in Figure 39, an enable (ENA+) signal corresponding to the sub-switch element (Qsub+) and an enable (ENA-) signal corresponding to the sub-switch element (Qsub-) are used.

[0316] The PWM control unit 5711 outputs the PWM signal to AND5514, on-delay circuit 5515, AND5519, AND5614, on-delay circuit 5615, and AND5619, respectively. Here, the detection unit 5221 detects the current (ILSENS) flowing on the side of the first output terminal T231 of the power supply 5123 and outputs the detection result to the PWM control unit 5711. The PWM control unit 5711 outputs a PWM signal based on the detection result of the current.

[0317] The AND5514 takes an enable (ENA+) signal and a PWM signal corresponding to a sub-switch element (Qsub+) as inputs, and outputs the logic results of these signals to the gate of the sub-switch element (Qsub+). In the example of Figure 37, the switch element (Qsub+) is switch element 5154 (Qsub+), and in the example of Figure 38, it is switch element 5333 (Qsub+).

[0318] The offset power supply 5512 outputs an offset voltage of 0[V] or greater to the negative input terminal of the comparator 5513. The P signal, as shown in the example in Figure 37 and Figure 38, is input to the + input terminal of comparator 5513. Comparator 5513 outputs values ​​to OR 5516 according to the inputs at the + and - terminals. Specifically, comparator 5513 outputs a value of 1 if the input at the + terminal is greater than the input at the - terminal, and outputs a value of 0 if the input at the + terminal is less than the input at the - terminal.

[0319] The on-delay circuit 5515 delays the PWM signal and outputs it to the OR5516. The OR5516 receives the output from the comparator 5513 and the output from the on-delay circuit 5515, and outputs the result of these logics to the AND5519. NOT5517 receives the output voltage from AND5619, inverts the input voltage (reverses its positive and negative signs), and outputs it to the on-delay circuit (SR) 5518. The on-delay circuit (SR) 5518 delays the input from NOT 5517 and outputs it to AND 5519. The AND5519 receives the PWM signal, the output from the OR5516, and the output from the on-delay circuit (SR)5518, and outputs the result of these logics to the gate of the main switch element (Qmain+). The switch element (Qmain+) in the example in Figure 37 and the example in Figure 38 is switch element 5111 (Qmain+).

[0320] The AND5614 takes an enable (ENA-) signal and a PWM signal corresponding to a sub-switch element (Qsub-) as inputs, and outputs the logic results of these signals to the gate of the sub-switch element (Qsub-). In the example of Figure 37, the switch element (Qsub-) is switch element 5156 (Qsub+), and in the example of Figure 38, it is switch element 5334 (Qsub+).

[0321] The offset power supply 5612 outputs an offset voltage of 0[V] or greater to the negative input terminal of the comparator 5613. The N signal, as shown in the examples in Figure 37 and Figure 38, is input to the + input terminal of comparator 5613. Comparator 5613 outputs values ​​to OR 5616 according to the inputs at the + and - terminals. Specifically, comparator 5613 outputs a value of 1 if the input at the + terminal is greater than the input at the - terminal, and outputs a value of 0 if the input at the + terminal is less than the input at the - terminal.

[0322] The on-delay circuit 5615 delays the PWM signal and outputs it to the OR5616. The OR5616 receives the output from the comparator 5613 and the output from the on-delay circuit 5615, and outputs the result of these logics to the AND5619. NOT5617 receives the output voltage from AND5519, inverts the input voltage (reverses its positive and negative signs), and outputs it to the on-delay circuit (SR)5618. The on-delay circuit (SR) 5618 delays the input from NOT 5617 and outputs it to AND 5619. The AND5619 receives the PWM signal, the output from the OR5616, and the output from the on-delay circuit (SR)5618, and outputs the result of these logics to the gate of the switch element (Qmain-) via the circuit section 5231. The switch element (Qmain-) in the example in Figure 37 and the example in Figure 38 is switch element 5112 (Qmain-).

[0323] Here, the example in Figure 39 is an example of a control circuit that uses an auxiliary winding 5211 to realize ZVS for the main switching elements, switch element 5111 (Qmain+) and switch element 5112 (Qmain-), in an AC converter as shown in Figures 26 and 27. For example, the control circuit of the unidirectional converter can be easily expanded by adding the detection unit 5221 (ILSENS) and the enable signals (ENA+, ENA-) for assist operation, which are generated based on the AC input voltage polarity. This is because, at the on-timing of the main rectifier element (QSR), which switches depending on the polarity, the comparator output of the corresponding NZCD detection point (P / N) is high, and therefore does not affect the on-timing of the main rectifier element (QSR) for NZCD detection.

[0324] (Example configuration of a power conversion device consisting of an AC converter equipped with a quasi-ZVS assist circuit) Referring to Figures 40 to 41, an example configuration of a power conversion device consisting of an AC converter equipped with a quasi-ZVS assist circuit will be described. Figures 40 and 41 show the case where the power conversion device consists of a boost converter.

[0325] <Semi-ZVS assist circuit of a power converter shown in the example in Figure 40> Figure 40 shows an example of the circuit configuration of a quasi-ZVS assist circuit according to the embodiment. In the example shown in Figure 40, the main circuit and control circuit are not shown. Here, the main circuit is the same as the main circuit shown in Figure 14.

[0326] The quasi-ZVS assist circuit comprises a primary winding 541 (Np) and a secondary winding 6011 of a coupled inductor, a diode 6012 (Dsub+), a switching element 6013 (Qsub+) made of a MOS-type FET, a diode 6014 (Dsub-), and a switching element 6015 (Qsub-) made of a MOS-type FET. Here, the primary winding 541(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit. Note that in the example shown in Figure 40, the primary winding 541(Np) is not shown.

[0327] One end of the secondary winding 6011 is connected to the cathode of diode 6012 and the anode of diode 6014. The cathode of diode 6014 is connected to the drain of switch element 6015. The other end of the secondary winding 6011 is connected to the source of the switch element 6015 and the drain of the switch element 6013. The anode of diode 6012 is connected to the source of switch element 6013.

[0328] <Power converter device as shown in Figure 41> Figure 41 shows an example of the circuit configuration of a power converter 6001 equipped with a quasi-ZVS assist circuit according to the embodiment. In the example shown in Figure 41, the control circuit is not shown.

[0329] The power converter 6001 comprises a main circuit and a quasi-ZVS assist circuit. The main circuit is the same as the main circuit in the example shown in Figure 14, and all circuit elements of the main circuit are shown using the same reference numerals, except for the primary winding 6051(Np) of the coupled inductor. Furthermore, Figure 41 shows a power supply 523 similar to the one shown in Figure 14.

[0330] The quasi-ZVS assist circuit has a configuration similar to the example in Figure 40. Specifically, the quasi-ZVS assist circuit comprises a primary winding 6051 (Np) and a secondary winding 6011 of a coupled inductor, a diode 6012 (Dsub+), a switching element 6013 (Qsub+) made of a MOS-type FET, a diode 6014 (Dsub-), and a switching element 6015 (Qsub-) made of a MOS-type FET. Here, the primary winding 6051(Np) of the coupled inductor may be considered not to be included in the quasi-ZVS assist circuit. The arrangement of the primary winding 6051 is the same as that of the primary winding 541 shown in Figure 14.

[0331] One end of the secondary winding 6011 is connected to the cathode of the half-wave rectifier diode 513 and to the anode of the half-wave rectifier diode 514. The cathode of diode 6012 (Dsub+) is connected to the anode of half-wave rectifier diode 513. The anode of diode 6014 (Dsub-) is connected to the cathode of half-wave rectifier diode 514.

[0332] In the circuit configuration shown in Figure 26, two secondary windings 1311 and 1312 (Ns windings) are required, whereas in the example shown in Figure 40, only one secondary winding 6011 is needed. The circuit configuration shown in Figure 40, like the circuit configuration shown in Figure 26, is effective when the body diode characteristics of the auxiliary FET are poor, or when it simplifies ZVS on control using an auxiliary winding.

[0333] The circuit configuration shown in Figure 41 is the same as the configuration shown in Figure 40, but applied to a totem pole PFC. The circuit configuration shown in Figure 41 can solve the following problems related to the AC diodes, namely the half-wave rectifier diodes 513 (BD+) and 514 (BD-).

[0334] In other words, in a totem pole PFC, the AC diode (BD+ / -) is turned off by a predetermined negative current (iQSR_off), resulting in recovery losses in the AC diode (BD+ / -). Furthermore, it is known that turning off the AC diode (BD+ / -) worsens the common-mode noise at the zero-crossing point of the AC diode's current. Therefore, it is common practice to replace the AC diodes (BD+ / -) with FETs to perform synchronous rectification, but this increases costs. As another example, connecting a relatively large capacitor to the AC diode (BD+ / -) alleviates the problem, but it is not a sufficient solution.

[0335] To address these challenges with AC diodes, the configuration of a ZVS assist circuit having TCM (Triangular Current Mode) shown in Figure 41 may be used. In the circuit shown in Figure 41, a switch element 6013 (Qsub+), which is an auxiliary switch that performs assist operation only when the input voltage is positive, and a switch element 6015 (Qsub-), which is an auxiliary switch that performs assist operation only when the input voltage is negative, are connected to the secondary winding 6011 (Ns) via AC diodes (BD+ / -) and auxiliary diodes (Dsub+ / -) of the corresponding polarities.

[0336] Here, if the number of turns of the secondary winding 6011 (Ns) is equal to the number of turns of the primary winding 6051 (Np), the current that conducts the AC diode (BD+ / -) will be equal to the input current ILm without the superimposed assist current. Therefore, the AC diode (BD+ / -) will not be turned off by a negative current (iQSR_off). This solves the above problem and makes it possible to replace the AC diode (BD+ / -) from a synchronous rectifier FET to an inexpensive general-purpose rectifier diode. However, a larger Vds = Vi + Vo is applied to the switch element (Qsub) that is always off during the polarity half-cycle when no assist operation is performed, compared to the example in Figure 40. In the example shown in Figure 41, for example, the arrangement (order of arrangement) of diode 6012 (Dsub+) and switch element 6013 (Qsub+) may be reversed, and the arrangement (order of arrangement) of diode 6014 (Dsub-) and switch element 6015 (Qsub-) may also be reversed.

[0337] (Example configuration of a multiphase power converter equipped with a ZVS assist circuit) Referring to Figure 42, an example configuration of a multiphase power converter equipped with a ZVS assist circuit (ZVS resonant assist circuit) will be described. Figure 42 shows a case where the power conversion device consists of a boost converter.

[0338] <ZVS assist circuit related to the example in Figure 42> Figure 42 shows an example of the circuit configuration of a multiphase power converter 6301 equipped with a ZVS assist circuit according to the embodiment. The example in Figure 42 shows the case where the ZVS assist circuit is applied to a Dual-Boost PFC circuit, illustrating an example configuration of a two-phase power converter 6301. In the example shown in Figure 42, the control circuit is not shown. For example, a control circuit configuration including auxiliary windings may be applied to the example in Figure 42. In the example shown in Figure 42, components similar to those shown in Figure 13 are given the same reference numerals. Dual-Boost PFC is sometimes also called Dual-Boost-bridgeless PFC or Dual-Boost semi-bridgeless PFC.

[0339] The power converter 6301 comprises a main circuit and a ZVS assist circuit. The main circuit comprises a main switch element 411 (Qmain) and a main diode 412 (Dm) consisting of a MOS-type FET for the first phase, a main switch element 413 (Qmain) and a main diode 414 (Dm) consisting of a MOS-type FET for the second phase, a capacitor 415 (Co) which is an output capacitor, a primary winding 431 (Np) of a coupled inductor corresponding to the first phase, and a primary winding 432 of a coupled inductor (Np) corresponding to the second phase. Furthermore, the main circuit includes diode 6391 corresponding to the first phase and diode 6392 corresponding to the second phase. Figure 42 also shows the power supply 6423, which is a single-phase AC power supply.

[0340] Here, the anode of diode 6391, the anode of diode 6392, and the first output terminal T51 are connected. The cathode of diode 6391 is connected to the first phase side of power supply 6423. The cathode of diode 6392 is connected to the second phase side of power supply 6423.

[0341] The ZVS assist circuit includes a primary winding 431(Np) of a coupled inductor corresponding to the first phase and a primary winding 432(Np) of a coupled inductor corresponding to the second phase. Furthermore, the ZVS assist circuit includes a circuit section corresponding to the first phase primary winding 431, comprising winding 6341 (Nc), tertiary winding 6342 (Nt), diode 6345 (Ds1), switching element 6346 (Qsub+ / -) made of MOS type FET, diode 6347 (Ds2), and auxiliary capacitor 6348 (Cs). The secondary winding (Ns=Nc+Nt) is formed by winding 6341 and tertiary winding 6342. Here, the arrangement of these circuit components is the same as in the example in Figure 13, except that the example in Figure 42 includes two diodes 6391 and 6392.

[0342] Furthermore, the ZVS assist circuit includes a winding 6351 (Nc), a tertiary winding 6352 (Nt), a diode 6353 (Ds1), and a diode 6361 as the circuit section corresponding to the primary winding 432 of the second phase. In addition, the circuit section corresponding to the primary winding 432 of the second phase shares the switch element 6346 (Qsub+ / -) with the first phase. Here, the primary windings 431(Np) and 432(Np) of the coupled inductor may be considered as not being included in the ZVS assist circuit. The secondary winding (Ns=Nc+Nt) is formed by winding 6351 and tertiary winding 6352.

[0343] Now, let's explain the arrangement of these circuit components. The first output terminal T51 is connected to one end of capacitor 6381 and to the anode of diode 6361. The other end of capacitor 6381 is connected to one end of winding 6351(Nc). The other end of winding 6351 is connected to the cathode of diode 6361 and to one end of tertiary winding 6352. The other end of the tertiary winding 6352 is connected to the anode of the diode 6353 (Ds1). The cathode of diode 6353 (Ds1) is connected to the drain of the sub-switch element 6346 (Qsub+ / -).

[0344] Here, the second phase circuit of the ZVS assist circuit shares the same sub-switching element 6346 (Qsub+ / -) as the first phase. In the example shown in Figure 42, a configuration example of a two-phase power converter 6301 is shown, but it is also possible to provide a ZVS assist circuit section corresponding to each phase in a power converter with three or more phases.

[0345] Here, the example in Figure 42 is an application example of a ZVS circuit for a dual-boost PFC using a single auxiliary switch element, switch element 6346 (Qsub+ / -). The gate signal of the switch element 6346 (Qsub+ / -) is generated based on the Q1+ gate signal (the gate signal of Qmain+) when the input polarity is positive, and based on the Q1- gate signal (the gate signal of Qmain-) when the input polarity is negative. When the input polarity is positive, the voltage across the negative inductor L- is 0[V] excluding the resistance drop, so no assist current is generated by turning on the switch element 6346(Qsub+ / -). Therefore, without causing operational interference, a ZVS operation similar to the operating waveform shown in Figure 6 can be obtained in the positive-side boost circuit.

[0346] (Example configuration of a multiphase power converter equipped with a quasi-ZVS assist circuit) Referring to Figure 43, an example configuration of a multiphase power converter equipped with a quasi-ZVS assist circuit (quasi-ZVS resonant assist circuit) will be explained. Figure 43 shows a case where the power conversion device consists of a boost converter.

[0347] <Semi-ZVS assist circuit related to the example in Figure 43> Figure 43 shows an example of the circuit configuration of a multiphase power converter 6501 equipped with a quasi-ZVS assist circuit according to the embodiment. The example in Figure 43 shows the application of a quasi-ZVS assist circuit to a dual-boost PFC circuit, illustrating an example configuration of a two-phase power converter 6501. In the example shown in Figure 43, the control circuit is not shown. For example, a control circuit configuration including auxiliary windings may be applied to the example in Figure 43. In the example shown in Figure 43, components similar to those shown in Figure 42 are given the same reference numerals.

[0348] The power converter 6501 comprises a main circuit and a quasi-ZVS assist circuit. The configuration of the main circuit is the same as the configuration of the main circuit in the example shown in Figure 42. Figure 43 also shows the power supply 6423.

[0349] The quasi-ZVS assist circuit includes a primary winding 431(Np) of a coupled inductor corresponding to the first phase and a primary winding 432(Np) of a coupled inductor corresponding to the second phase. Furthermore, the quasi-ZVS assist circuit includes a secondary winding 6531 (Ns), a diode 6532, and an auxiliary switching element 6533 (Qsub+ / -) consisting of a MOS-type FET, as a circuit section corresponding to the primary winding 431 of the first phase.

[0350] Here, one end of the secondary winding 6531(Ns) is connected to the first output terminal T51. The other end of the secondary winding 6531(Ns) is connected to the anode of the diode 6532. The cathode of diode 6532 is connected to the drain of auxiliary switch element 6533 (Qsub+ / -). The source of the auxiliary switch element 6533 (Qsub+ / -) is connected to the first output terminal T51.

[0351] Furthermore, the quasi-ZVS assist circuit includes a secondary winding 6551 (Ns) and a diode 6552 as the circuit section corresponding to the primary winding 432 of the second phase. In addition, the circuit section corresponding to the primary winding 432 of the second phase shares an auxiliary switching element 6533 (Qsub+ / -) with the first phase. Here, one end of the secondary winding 6551(Ns) is connected to the first output terminal T51. The other end of the secondary winding 6551(Ns) is connected to the anode of the diode 6552. The cathode of diode 6552 is connected to the drain of auxiliary switch element 6533 (Qsub+ / -).

[0352] Thus, the second phase circuit of the quasi-ZVS assist circuit shares the same switching element 6533 (Qsub+ / -) as the first phase. In the example shown in Figure 43, a configuration example of a two-phase power converter 6501 is shown, but it is also possible to provide a quasi-ZVS assist circuit section corresponding to each phase in a power converter with three or more phases.

[0353] Here, the example in Figure 43 is an application example of a quasi-ZVS circuit for a dual-boost PFC using a single auxiliary switch element, switch element 6533 (Qsub+ / -). The gate signal of the switch element 6533 (Qsub+ / -) is generated based on the Q1+ gate signal (the gate signal of Qmain+) when the input polarity is positive, and based on the Q1- gate signal (the gate signal of Qmain-) when the input polarity is negative. When the input polarity is positive, the voltage across the negative inductor L- is 0[V] excluding the resistance drop, so no assist current is generated by turning on the switch element 6533(Qsub+ / -). Therefore, without causing operational interference, a quasi-ZVS operation similar to the operating waveform shown in Figure 25 can be obtained in the positive-side boost circuit.

[0354] (Diode clamp circuit) Refer to Figures 44 and 45 to see the diode clamp circuit.

[0355] <Power converter related to the example in Figure 44> Figure 44 shows an example of the circuit configuration of a power converter 7001 equipped with a ZVS assist circuit according to the embodiment. In the example shown in Figure 44, the control circuit is not shown.

[0356] The power converter 7001 comprises a main circuit and a ZVS assist circuit. The main circuit is the same as the main circuit shown in the example in Figure 4, and the circuit elements of the main circuit are shown using the same reference numerals. Furthermore, Figure 44 shows a power supply 21(Vi) similar to that shown in Figure 4.

[0357] The ZVS assist circuit comprises a primary winding 7031 (Np), a winding 7051 (Nc=Ns-Nt), a tertiary winding 7052 (Nt), a diode 7034, a switching element 7035, a capacitor 7037, and a diode 7053.

[0358] Here, in the example in Figure 44, instead of the primary winding 31 (Np), winding 51 (Nc=Ns-Nt), tertiary winding 52 (Nt), diode 34, switch element 35, capacitor 37, and diode 53 in the example in Figure 4, a configuration is shown that includes a primary winding 7031 (Np), winding 7051 (Nc=Ns-Nt), tertiary winding 7052 (Nt), diode 7034, switch element 7035, capacitor 7037, and diode 7053. However, these are essentially similar ZVS assist circuits.

[0359] Furthermore, the power converter 7001 according to this embodiment includes a diode 7111. The anode of diode 7111 is connected to the cathode of diode 7034 and the drain of switch element 7035. The cathode of diode 7111 is connected to the second output terminal T2.

[0360] This diode clamp circuit using diode 7111 serves as a surge voltage countermeasure for the auxiliary switch (switch element 7035) in the actual device.

[0361] This configuration realizes a lossless clamping circuit that can be used when VQsub is smaller than Vo in (Equation 9). In equation (9), VQsub represents the voltage across the switch element 7035, VNs represents the voltage across the secondary winding (Ns), VCc represents the voltage across the capacitor 7037, Np represents the number of turns of the primary winding 7031, Ns represents the number of turns of the secondary winding, Nt represents the number of turns of the tertiary winding 7052, Vo represents the output voltage of the main circuit (the voltage between the first output terminal T1 and the second output terminal T2), and Vi represents the voltage of the power supply 21.

[0362]

number

[0363] <Power converter shown in the example in Figure 45> Figure 45 shows an example of the circuit configuration of a power converter 7301 equipped with a quasi-ZVS assist circuit according to the embodiment. In the example shown in Figure 45, the control circuit is not shown.

[0364] The power converter 7301 comprises a main circuit and a quasi-ZVS assist circuit. The main circuit is the same as the main circuit in the example shown in Figure 21(A), and the circuit elements of the main circuit are shown using the same reference numerals. Furthermore, Figure 45 shows a power supply 21(Vi) similar to the one shown in Figure 21(A).

[0365] The quasi-ZVS assist circuit comprises a primary winding 7331 (Np), a secondary winding 7332 (Ns), a diode 7333, and a switching element 7334. Here, the arrangement of these circuits is essentially the same as in the case of the quasi-ZVS assist circuit shown in Figure 21(C).

[0366] Furthermore, the power converter 7301 according to this embodiment includes a diode 7411 and a diode 7412. The anode of diode 7411 is connected to the cathode of diode 7333. The cathode of diode 7411 is connected to the second output terminal T2. The anode of diode 7412 is connected to the drain of auxiliary switch element 7334. The cathode of diode 7412 is connected to the second output terminal T2.

[0367] Diode clamp circuits using diodes 7411 and 7412 serve as a surge voltage countermeasure for the auxiliary switch (switch element 7334) in actual equipment.

[0368] With this configuration, the clamp circuit can be connected when VDsub is smaller than Vo in (Equation 10). In equation (10), VDsub represents the voltage across diode 7333, VNs represents the voltage across secondary winding 7332(Ns), Np represents the number of turns of primary winding 7331, Ns represents the number of turns of secondary winding 7332, and Vi represents the voltage of power supply 21.

[0369]

number

[0370] <Example Configuration> [Example of ZVS assist circuit configuration] As one example configuration (as shown in Figures 1-4 and 7-10), the power converter includes a converter comprising a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and the primary winding (Np) of a coupled inductor; a first series circuit comprising the secondary winding (Ns) of the coupled inductor, a first rectifier element (Ds1), and an auxiliary switch element (Qsub); a second series circuit comprising the tertiary winding (Nt) of the coupled inductor and a second rectifier element (Ds2); and a closed-loop resonance assist circuit (ZVS assist circuit) comprising an auxiliary capacitor (Cs) to which the first and second series circuits are connected. Furthermore, the secondary and tertiary windings are separate components, and the configuration involves either the first and second series circuits being connected in parallel to an auxiliary capacitor (examples in Figures 1-3), or the tertiary winding being integrated with the secondary winding (examples in Figures 4, 7-10). Here, a configuration in which the secondary winding and tertiary winding are separate means that the secondary winding and tertiary winding are separate windings (in the example in Figure 1, the secondary winding 32 and the tertiary winding 33 are separate windings). Furthermore, a configuration in which the tertiary winding is integrated with the secondary winding indicates that the secondary winding is composed of the tertiary winding and other windings (in the example in Figure 4, the secondary winding (Ns) is composed of winding 51 and tertiary winding 52).

[0371] As one example configuration (as shown in Figures 6 and 18), the power converter further includes a control unit (for example, a control circuit), which turns on the auxiliary switch element (Qsub), then turns on the main switch element (Qmain), and then turns off the main switch element (Qmain) after turning off the auxiliary switch element (Qsub) or simultaneously with turning off the auxiliary switch element (Qsub).

[0372] In one example configuration (as shown in Figure 18), the power converter uses the voltage of the tertiary winding (Nt) or auxiliary winding (Nt') and the voltage of the auxiliary capacitor (Cs) to determine the ON timing of the main switch element (Qmain).

[0373] As one example configuration (as shown in Figures 7 and 8), in a power conversion device, the converter is either a boost converter or a buck converter, and a constant voltage source (Vcc) is obtained from the voltage of the second rectifier element (Ds2) via rectifier diodes (diodes 118 and 158 in the examples of Figures 7 and 8).

[0374] As one example configuration (the example in Figure 13), the power converter has a multiphase system including a main switch element (Qmain) and a main rectifier element (Dm), and the resonant assist circuit is a multiphase resonant assist circuit corresponding to this multiphase system. As one example configuration (see Figure 13), in a power converter, in a multiphase resonant assist circuit, one or both of the auxiliary capacitor (Cs) and the second rectifier element (Ds2) are shared by at least two phases.

[0375] As an example configuration (as shown in Figure 11), the power converter includes a converter comprising a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and the primary winding (Np) of a coupled inductor; a first series circuit of a first rectifier element (diode 317 (Ds1') in the example of Figure 11) and a first auxiliary capacitor (capacitor 316 (Cs) in the example of Figure 11); and a second auxiliary capacitor (capacitor 313 (Cs) in the example of Figure 11). The device comprises a second series circuit of a coupled inductor and a second rectifier element (in the example in Figure 11, diode 314 (Ds1')), a third series circuit in which the first series circuit and the second series circuit are connected in parallel, including the secondary winding (Ns) of the coupled inductor and an auxiliary switch element (Qsub), and a third rectifier element (Ds2') positioned between the anode of the first rectifier element and the cathode of the second rectifier element, and a closed-loop resonant assist circuit (ZVS assist circuit).

[0376] As an example configuration (the example in Figure 12), the power converter includes a converter containing a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and the primary winding (Np) of a coupled inductor; a first series circuit of a first rectifier element (in the example in Figure 12, diode 338 (Ds1')) and a first auxiliary capacitor (in the example in Figure 12, capacitor 336 (Cs)); a second series circuit of a second auxiliary capacitor (in the example in Figure 12, capacitor 333 (Cs)) and a second rectifier element (in the example in Figure 12, diode 334 (Ds1')); and a third rectifier element (in the example in Figure 12, diode 341 (Ds1')) and a third auxiliary capacitor (in the example in Figure 12, capacitor...). The device comprises a third series circuit of 340(Cs)) and a fourth rectifier element (diode 339(Ds1') in the example of Figure 12), a fourth series circuit in which the first series circuit, the second series circuit and the third series circuit are connected in parallel, including the secondary winding (Ns) of the coupled inductor and an auxiliary switch element (Qsub), and a closed-loop resonant assist circuit (ZVS assist circuit) including a fifth rectifier element (diode 337(Ds2') in the example of Figure 12) placed between the anode of the first rectifier element and the cathode of the fourth rectifier element, and a sixth rectifier element (diode 335(Ds2') in the example of Figure 12) placed between the cathode of the second rectifier element and the anode of the third rectifier element.

[0377] As an example configuration (the example in Figure 14), the power converter includes a converter comprising a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and the primary winding (Np) of a coupled inductor, wherein the current polarity of the primary winding is switched between positive and negative, and a closed-loop resonant assist circuit (ZVS assist circuit), the closed-loop circuit comprising a first series circuit of the secondary winding (Ns) of the coupled inductor, a first rectifier element (Ds1+), and a first auxiliary switch (Qsub+) which is driven when the current polarity of the primary winding is positive, and the coupled inductor The closed-loop circuit includes a second series circuit of the tertiary winding (Nt) and a second rectifier element (Ds2+), and a first auxiliary capacitor (Cs+) to which the first series circuit and the second series circuit are connected. Furthermore, the closed-loop circuit includes a third rectifier element (Ds1-), a second auxiliary switch (Qsub-) driven when the current polarity of the primary winding is negative, a third series circuit of the secondary winding (Ns), a fourth series circuit of the tertiary winding (Nt) and a fourth rectifier element (Ds2-), and a second auxiliary capacitor (Cs-) to which the third series circuit and the fourth series circuit are connected, and which is also connected to the first auxiliary capacitor (Cs+). Furthermore, the secondary and tertiary windings are separate components, and the configuration involves either the first series circuit and the second series circuit being connected in parallel to the first auxiliary capacitor, or the tertiary winding being integrated with the secondary winding. Similarly, the secondary and tertiary windings are separate components, and the third and fourth series circuits are connected in parallel to the second auxiliary capacitor, or the tertiary winding is integrated with the secondary winding. In the example shown in Figure 14, the tertiary winding is integrated with the secondary winding. However, other configurations may be used in which the secondary and tertiary windings are separate.

[0378] As one example configuration (the example in Figure 42), the power converter is applied to a dual-boost PFC connected to a single-phase AC input and has two boost circuits including a main switch element (Qmain) and a main rectifier element (Dm). The resonant assist circuit corresponds to these two boost circuits, and the auxiliary switch element (Qsub+ / -) is shared in the resonant assist circuit.

[0379] [Example of a quasi-ZVS assist circuit configuration] As one example configuration (as shown in Figures 21 to 24), the power converter comprises a converter including a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and the primary winding (Np) of a coupled inductor, and a resonant assist circuit (ZVS assist circuit) which is a closed-loop circuit including a series circuit of the secondary winding (Ns) of the coupled inductor, a first rectifier element (Ds1), and an auxiliary switch element (Qsub).

[0380] As one example configuration (the example in Figure 25), the power converter further includes a control unit (for example, a control circuit), which turns on the auxiliary switch element (Qsub), then turns on the main switch element (Qmain), and then turns off the main switch element (Qmain) after turning off the auxiliary switch element (Qsub) or simultaneously with turning off the auxiliary switch element (Qsub).

[0381] As one example configuration (a modified version of Figures 21-24 and 25), the power converter further includes a second control unit (for example, a control circuit), which causes the main rectifier element (Dm), a switch element responsible for the return current operation of the excitation current of the primary winding (Np), to perform a pair of on / off operations with the main switch element (Qmain) with a short-circuit prevention period, and after turning on the auxiliary switch element (Qsub), the second control unit turns off the main rectifier element (Dm) when the current of the main rectifier element (Dm) becomes an arbitrary negative current value. In the examples shown in Figures 21 to 24, the main rectifier element (Dm) is a diode. However, as a modification, the above control can be achieved by using a switch element instead of the main rectifier element (Dm). The second control unit may be the same as the control unit in the example shown in Figure 25, or it may be a different control unit.

[0382] As one example configuration (as shown in Figures 22, 23, and 24), in a power conversion device, the converter is either a step-up / step-down converter, a flyback converter, or a buck converter, and a constant voltage source (Vcc) is obtained from the voltage of the secondary winding via rectifier diodes (diodes 1155, 1181, and 1221 in the examples of Figures 22, 23, and 24).

[0383] As one example configuration (the example in Figure 26), the power converter includes a converter that includes a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and a primary winding (Np) of a coupled inductor, and the current polarity of the primary winding is switched between positive and negative; a first closed-loop circuit that includes the positive secondary winding (Ns+) of the coupled inductor, a first rectifier element (Ds1+), and a first auxiliary switch (Qsub+) that is driven when the current polarity of the primary winding (Np) is positive; and a second closed-loop circuit that includes the negative secondary winding (Ns-) of the coupled inductor, a second rectifier element (Ds1-), and a second auxiliary switch (Qsub-) that is driven when the current polarity of the primary winding (Np) is negative, thereby comprising a resonance assist circuit (ZVS assist circuit).

[0384] As one example configuration (the example in Figure 27), the power converter includes a converter that switches the current polarity of the primary winding (Np) between positive and negative, a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and a primary winding (Np) of a coupled inductor, and a closed-loop resonant assist circuit that includes a secondary winding (Ns) of the coupled inductor, a first rectifier element connected in parallel to a first auxiliary switch (Qsub+) which is driven when the current polarity of the primary winding (Np) is positive, and a second rectifier element connected in parallel to a second auxiliary switch (Qsub-) which is driven when the current polarity of the primary winding (Np) is negative.

[0385] As one example configuration (see Figures 28-29), the power converter further includes a control unit (for example, a control circuit), which causes the main rectifier element (QSR), a switching element responsible for the return current operation of the excitation current of the primary winding (Np), to perform a pair of on / off operations with the main switch element (Qmain) with a short-circuit prevention period, and after turning on either the first auxiliary switch (Qsub+) or the second auxiliary switch (Qsub-), the control unit turns off the main rectifier element (QSR) when the current of the main rectifier element (QSR) becomes an arbitrary negative current value.

[0386] As one example configuration (see Figures 34-35), the power converter includes a converter comprising a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and the primary winding (Np) of a coupled inductor; a resonant assist circuit (ZVS assist circuit) formed by a closed-loop circuit including a series circuit of the secondary winding (Ns) of the coupled inductor, a first rectifier element (Ds1), and an auxiliary switch element (Qsub); and a control unit that determines the on-timing of the main switch element (Qmain) using the voltage of the auxiliary winding (Nt'). As one example configuration (see Figures 34-35), in a power converter, the control unit turns on the auxiliary switch element (Qsub), then turns on the main switch element (Qmain) using the voltage of the auxiliary winding (Nt'), and then turns off the main switch element (Qmain) after turning off the auxiliary switch element (Qsub) or simultaneously with turning off the auxiliary switch element (Qsub). Furthermore, as an example configuration (see Figures 34-35), the power converter includes a second control unit, which causes the main rectifier element (Dm), a switch element responsible for the recirculation operation of the excitation current of the primary winding (Np), to perform a paired on / off operation with the main switch element (Qmain) with a short-circuit prevention period, and after turning on the auxiliary switch element (Qsub), turns off the main rectifier element (Dm) when the current of the main rectifier element (Dm) becomes an arbitrary negative current value.

[0387] As an example configuration (see Figures 37 and 39), the power converter includes a main switch element (Qmain+), a main rectifier element (Qmain-), an output capacitor (Co), and a primary winding (Np) of a coupled inductor, and a converter that switches the current polarity of the primary winding (Np) between positive and negative, a positive secondary winding (Ns+) of the coupled inductor, a first rectifier element (Ds1+), and a first auxiliary switch that is driven when the current polarity of the primary winding (Np) is positive. The device comprises a first closed-loop circuit including Qsub+, a second closed-loop circuit including the negative secondary winding (Ns-) of the coupled inductor, a second rectifier element (Ds1-), and a second auxiliary switch (Qsub-) driven when the current polarity of the primary winding (Np) is negative, and a control unit that determines the on-timing of the main switch element (Qmain+) using the voltage of the auxiliary winding (Nt':NZCD).

[0388] As one example configuration (see Figures 38 and 39), the power converter includes a converter that switches the current polarity of the primary winding (Np) between positive and negative, a converter that includes a main switch element (Qmain+), a main rectifier element (Qmain-), an output capacitor (Co), and a primary winding (Np) of a coupled inductor, a secondary winding (Ns) of the coupled inductor, a first rectifier element connected in parallel to a first auxiliary switch (Qsub+) that is driven when the current polarity of the primary winding (Np) is positive, and a second rectifier element connected in parallel to a second auxiliary switch (Qsub-) that is driven when the current polarity of the primary winding (Np) is negative, and a control unit that determines the on-timing of the main switch element (Qmain+) using the voltage of the auxiliary winding (Nt':NZCD). Furthermore, as an example configuration (as shown in Figures 38 and 39), in a power converter, the control unit causes the main rectifier element (Qmain-), which is a switch element responsible for the return current operation of the excitation current of the primary winding (Np), to perform a paired on / off operation with the main switch element (Qmain+) with a short-circuit prevention period. After turning on either the first auxiliary switch (Qsub+) or the second auxiliary switch (Qsub-), the control unit turns off the main rectifier element (Qmain-) when the current of the main rectifier element (Qmain+) reaches an arbitrary negative current value.

[0389] As one example configuration (the example in Figure 40), the power converter includes a converter that includes a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and a primary winding (Np) of a coupled inductor, and the current polarity of the primary winding (Np) is switched between positive and negative; a first closed-loop circuit that includes a secondary winding (Ns) of a coupled inductor, a first rectifier element (Dsub+), and a first auxiliary switch (Qsub+) that is driven when the current polarity of the primary winding (Np) is positive; and a resonance assist circuit (ZVS assist circuit) formed by a second closed-loop circuit that includes a secondary winding (Ns) of a coupled inductor, a second rectifier element (Dsub-), and a second auxiliary switch (Qsub-) that is driven when the current polarity of the primary winding (Np) is negative. As one example configuration (as shown in Figure 41), the power converter is applied to a totem pole PFC, with the positive AC diode (BD+) of the totem pole PFC connected between the series circuit of the secondary winding (Ns), the first rectifier element (Dsub+), and the first auxiliary switch (Qsub+), and the negative AC diode (BD-) of the totem pole PFC connected between the series circuit of the secondary winding (Ns), the second rectifier element (Dsub-), and the second auxiliary switch (Qsub-).

[0390] As an example configuration (see Figure 43), the power converter comprises a converter including a main switch element (Qmain), a main rectifier element (Dm), an output capacitor (Co), and the primary winding (Np) of a coupled inductor, and a resonant assist circuit (ZVS assist circuit) which is a closed-loop circuit including the secondary winding (Ns) of a coupled inductor, a first rectifier element, and an auxiliary switch element in series. The power converter has two boost circuits including a main switch element (Qmain) and a main rectifier element (Dm) that are applied to a dual boost PFC connected to a single-phase AC input, and the resonant assist circuit corresponds to the two boost circuits, with the auxiliary switch element (Qsub+ / -) being shared in the resonant assist circuit. Furthermore, as one example configuration (the example in Figure 43), the power converter includes a control unit that uses the voltage of the auxiliary winding (Nt') of the coupled inductor to determine the on-timing of the main switch element (Qmain).

[0391] While embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include designs and other elements that do not depart from the gist of this disclosure. [Explanation of symbols]

[0392] 1-4, 101-104, 401, 501-503, 601-603, 1001-1004, 1301, 1501, 1601, 1701, 4001, 4201, 4301, 4501, 5001, 5301, 6001, 6301, 6501, 7001, 7301... Power converter, 1 1, 35, 115, 132, 155, 183, 215, 245, 264, 312, 332, 411, 413, 446, 454, 511, 5 12, 545, 549, 577, 581, 591, 1134, 1134a, 1134b, 1154, 1174, 1213, 1314, 131 6, 1333, 1334, 1411, 1412, 1423, 1424, 1511~1514, 1516, 1517, 1543, 1544, 1611~1614, 1643, 1644, 1711~1714, 1743, 1744, 4035, 4234, 4334, 5111, 511 2, 5154, 5156, 5333, 5334, 6013, 6346, 6533, 7035, 7334... switch elements, 12, 34, 36, 42, 53, 114, 116, 118, 133, 154, 156, 158, 182, 214, 216, 242, 263, 265, 314, 315, 317, 334, 335, 337, 338, 339, 341, 412, 414, 445, 447, 453, 461, 544, 54 6, 548, 550, 576, 580, 592, 593, 621, 651, 661, 691, 1133, 1133a, 1133b, 1153 ,1155,1173,1181,1212,1221,1313,1315,4034,4053,4233,4333,5153,5155,5212,5213,6012,6014,6345,6347,6353,6361,6391,6392,6532,6552 ,7053,7333,7411,7412…diodes, 13,37,117,131,157,181,217,241,266,313,316,333,336,340,415,448,515,547,551,579,652,1413,1515,1672,1715,4037,5113,6348,6381,7037…capacitors, 21,23,121,171,251,423,523,1523,1623,1631,1731,5123,6423…power supplies, 31,111,151,211,244,431,432,541,1131, 1131a, 1131b, 1151, 1171, 1331, 1541, 1641, 1741, 4231, 4331, 5131, 6051, 7031, 7331… Primary winding, 32, 311, 331, 1132, 1132a, 1132b, 1152, 1172, 1211, 1311, 1312, 1332, 1542, 1642, 1742, 4232, 4332, 5151, 5152, 5332, 6011, 6531, 6551, 7332… Secondary winding, 33, 41, 52, 113, 153, 213, 262, 442 ,452,543,573,575,4052,6342,6352,7052...Tertiary winding, 51,112,152,212,243,261,441,451,542,572,574,4051,6341,6351,7051...Winding, 71,72,1422...Inductor, 578,582...Thyristor, 611,4111,5211...Auxiliary winding, 612,642,682,4112...Calculator, 613,643,683,4113,5513,5613...Comparator, 614,615,644,645,684,685 5514, 5519, 5614, 5619…AND, 616, 646, 686, 4116, 4615, 5515, 5615…On-delay circuit, 617, 647, 687, 4117, 5516, 5616…OR, 1401…Equivalent circuit, 1421…Excitation inductor, 513, 514, 1431…Half-wave rectifier diode, 1671…Resistor, 2011~2018, 2111~2117, 3011~3018, 3111~3119…Waveform, 4118…Off-delay circuit, 4119…D-type flip-flop, 4251, 4351, 5512, 5612...Offset power supply, 4711...PWM control unit, 4731, 5231...Circuit unit, 5221...Detection unit, 5517, 5617...NOT, 4618, 5518, 5618...On-delay circuit (SR), A1~A4, 301, 302...ZVS assist circuit, B1~B3...Point, G1...Ground terminal, P1...Direction, T1, T12, T22, T32, T52, T62, T102, T121, T231...First output terminal, T2, T11, T21, T31, T51, T61, T101, T122, T232...Second output terminal,

Claims

1. A converter including a main switching element, a main rectifying element, an output capacitor, and the primary winding of a coupled inductor, A resonant assist circuit comprising a closed-loop circuit including a first series circuit of the secondary winding of the coupled inductor, a first rectifier element, and an auxiliary switch element, a second series circuit of the tertiary winding of the coupled inductor and a second rectifier element, and an auxiliary capacitor to which the first series circuit and the second series circuit are connected, Equipped with, The secondary winding and the tertiary winding are separate components, and the first series circuit and the second series circuit are connected in parallel to the auxiliary capacitor, or the tertiary winding is integrated with the secondary winding. Furthermore, it includes a control unit, The control unit turns on the auxiliary switch element, then turns on the main switch element, and then turns off the main switch element after turning off the auxiliary switch element or simultaneously with turning off the auxiliary switch element. The control unit determines the on-timing of the main switch element using the voltage of the tertiary winding or the auxiliary winding of the coupled inductor and the voltage of the auxiliary capacitor. Power converter.

2. The converter is either a boost converter or a buck converter. A constant voltage source is obtained from the voltage of the second rectifier element via a rectifier diode. The power conversion device according to claim 1.

3. It has a multiphase system including the main switch element and the main rectifier element, The aforementioned resonance assist circuit is a multiphase resonance assist circuit corresponding to the multiphase. A power conversion device according to claim 1 or claim 2.

4. In the aforementioned multiphase resonant assist circuit, one or both of the auxiliary capacitor and the second rectifier element are shared in at least two phases. The power conversion device according to claim 3.

5. Applicable to dual boost PFC connected to single-phase AC input, It has two boost circuits, one of which includes the main switch element and the other of which includes the main rectifier element. The aforementioned resonance assist circuit corresponds to the two boost circuits, In the aforementioned resonance assist circuit, the auxiliary switch element is shared. A power conversion device according to any one of claims 1 to 3.

6. A converter including a main switching element, a main rectifying element, an output capacitor, and the primary winding of a coupled inductor, A resonant assist circuit comprising a closed-loop circuit including a first series circuit of the secondary winding of the coupled inductor, a first rectifier element, and an auxiliary switch element, a second series circuit of the tertiary winding of the coupled inductor and a second rectifier element, and an auxiliary capacitor to which the first series circuit and the second series circuit are connected, Equipped with, The secondary winding and the tertiary winding are separate components, and the first series circuit and the second series circuit are connected in parallel to the auxiliary capacitor, or the tertiary winding is integrated with the secondary winding. The converter is either a boost converter or a buck converter. A constant voltage source is obtained from the voltage of the second rectifier element via a rectifier diode. Power converter.

7. Furthermore, it includes a control unit, The control unit turns on the auxiliary switch element, then turns on the main switch element, and then turns off the main switch element after turning off the auxiliary switch element or simultaneously with turning off the auxiliary switch element. The power conversion device according to claim 6.

8. It has a multiphase system including the main switch element and the main rectifier element, The aforementioned resonance assist circuit is a multiphase resonance assist circuit corresponding to the multiphase. The power conversion device according to claim 6 or claim 7.

9. In the aforementioned multiphase resonant assist circuit, one or both of the auxiliary capacitor and the second rectifier element are shared in at least two phases. The power conversion device according to claim 8.

10. Applicable to dual boost PFC connected to single-phase AC input, It has two boost circuits, one of which includes the main switch element and the other of which includes the main rectifier element. The aforementioned resonance assist circuit corresponds to the two boost circuits, In the aforementioned resonance assist circuit, the auxiliary switch element is shared. A power conversion device according to any one of claims 6 to 8.

Images