Power conversion device

Abstract

To provide a current resonance type capacitor at a stage after a boosting capacitor, and achieve high efficiency even when an input voltage of the boosting capacitor can take two or more kinds of input voltage levels.SOLUTION: In a power conversion device, a control circuit sets an output voltage of a boosting capacitor to a first output voltage level or a second output voltage level according to a voltage detected by an input voltage detection circuit that detects a voltage corresponding to an input voltage. When the first output voltage level is set, a current resonance type capacitor is caused to operate in a full bridge mode. When the second output voltage level is set, the current resonance type capacitor is caused to operate in a half-bridge mode. The first output voltage level or the second output voltage level is set at a prescribed timing after the input of the input voltage. Until the setting of the first output voltage level or the second output voltage level is reset, the set operation mode is maintained.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In a power conversion device including a current resonant converter in the rear stage of a boost converter, the input voltage of the boost converter may be at two or more input voltage levels. As a specific example, the input voltage level may differ depending on the country in which the power conversion device is used.

[0003] Patent Document 1 describes a current resonant converter that converts a DC input voltage into AC, which switches between a full-bridge switching circuit and a half-bridge switching circuit depending on the DC input voltage (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-289354 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional techniques described above, in a power conversion device including a current resonant converter in the subsequent stage of a boost converter, when two or more types of input voltage levels are possible, efficiency may decrease.

[0006] The present disclosure has been made in consideration of the above circumstances, and has an objective of providing a power conversion device that can achieve high efficiency in a configuration that includes a current resonant converter in a subsequent stage of a boost converter, even when the input voltage of the boost converter can have two or more input voltage levels. [Means for solving the problem]

[0007] One aspect is a power conversion device including a boost converter, a current resonant converter connected to a downstream side of the boost converter, and a control circuit, wherein the boost converter boosts an input voltage to generate an output voltage and outputs the output voltage while charging a first output capacitor with the output voltage, the control circuit controls the boost converter based on a voltage detected by an output voltage detection circuit that detects a voltage of the first output capacitor, the control circuit sets the output voltage of the boost converter to a first output voltage level or a second output voltage level according to a voltage detected by an input voltage detection circuit that detects a voltage according to the input voltage, and when the first output voltage level is set, the control circuit operates the current resonant converter in a full-bridge mode operation mode, and when the second output voltage level is set, the control circuit operates the current resonant converter in a half-bridge mode operation mode, the output voltage detection circuit and the input voltage detection circuit are a common circuit or separate circuits, the first output voltage level or the second output voltage level is set at a predetermined timing after the input voltage is input, and the set operation mode is maintained until the setting of the first output voltage level or the second output voltage level is reset. Effect of the Invention

[0008] According to the present disclosure, in a power conversion device configured to include a current resonant converter in a subsequent stage of a boost converter, high efficiency can be achieved even when the input voltage of the boost converter can be two or more different input voltage levels. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of a circuit configuration of a power conversion system according to a first embodiment. [Figure 2A] FIG. 4 is a diagram illustrating an example of switching loss of a switching element. [Figure 2B] 11A and 11B are diagrams illustrating another example of switching loss of a switching element. [Figure 2C] 11A and 11B are diagrams illustrating another example of switching loss of a switching element. [Diagram 3] 5A and 5B are diagrams illustrating an example of switching loss and conduction loss of a switching element. [Figure 4A] FIG. 1 is a diagram illustrating an example of a relationship between an operating frequency and an output voltage ratio of a current resonant converter. [Figure 4B] FIG. 11 is a diagram illustrating another example of the relationship between the operating frequency and the output voltage ratio of the current resonant converter. [Figure 5A] FIG. 11 is a diagram showing an example of a relationship between an AC input voltage and an output voltage for explaining switching between a full-bridge operation and a half-bridge operation according to the embodiment. [Figure 5B] 1 is a diagram showing a half-bridge operation in a current resonant converter according to an embodiment of the present invention; [Figure 5C] 1 is a diagram showing a full-bridge operation in a current resonant converter according to an embodiment of the present invention; [Figure 5D] 5 is a diagram showing an example of a voltage applied to a primary side of a transformer during half-bridge operation according to the embodiment. FIG. [Figure 5E] 5 is a diagram showing an example of a voltage applied to a primary side of a transformer during a full-bridge operation according to the embodiment. FIG. [Figure 6A] FIG. 2 is a diagram illustrating an example of a drive signal switching circuit according to the embodiment. [Figure 6B] 5A and 5B are diagrams illustrating an example of input and output signals of a drive signal switching circuit according to the embodiment. [Figure 7] FIG. 11 is a diagram illustrating an example of a circuit configuration of a power conversion system according to a second embodiment. [Figure 8] FIG. 11 is a diagram showing a process flow illustrating an example of a boost voltage selection process according to the second embodiment. [Figure 9A] FIG. 11 is a diagram illustrating an example of a circuit configuration of a power conversion system according to a third embodiment. [Figure 9B] FIG. 11 is a diagram showing a table illustrating an example of the relationship between the input voltage, the output voltage of the boost converter, and the operation mode of the current resonant converter according to the third embodiment. [Figure 10]FIG. 13 is a diagram illustrating an example of a circuit configuration of a power conversion system according to a fourth embodiment. [Figure 11] FIG. 13 is a diagram illustrating an example of a circuit configuration of a power conversion system according to a fifth embodiment. [Figure 12] FIG. 13 is a diagram illustrating an example of a circuit configuration of a power conversion system according to a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0011] (First embodiment) A first embodiment will be described. [Power conversion system] FIG. 1 is a diagram showing an example of a circuit configuration of a power conversion system A1 according to the first embodiment. The power conversion system A1 includes a power conversion device 1, a single-phase AC power supply 11, and a resistor 12. The power conversion device 1 includes a boost converter B1, a current resonant converter B2, and a control circuit 111. In this embodiment, the current resonant converter B2 is an LLC type. The current resonant converter B2 is connected to the rear stage of the boost converter B1. In this embodiment, the input voltage of the boost converter B1 is a single-phase AC voltage.

[0012] In this embodiment, the AC power supply 11 and the resistor 12 are circuits external to the power conversion device 1. However, as another example, a configuration in which one or both of the AC power supply 11 and the resistor 12 are circuits internal to the power conversion device 1 may be used. For example, when both the AC power supply 11 and the resistor 12 are circuits inside the power conversion device 1, the power conversion system A1 according to this embodiment and the power conversion device 1 are the same.

[0013] The boost converter B1 includes a diode bridge 31, an inductor 32, a diode 33, a capacitor 34, and a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) Q1 which is a switching element. The current resonant converter B2 includes four MOSFETs Q11 to Q14 which are switching elements, an inductor 51, a primary winding 52, a capacitor 53, secondary windings 71 and 72, two diodes 91 and 92, and a capacitor 93. The control circuit 111 includes a boost converter control circuit 131, a voltage detection circuit 132, an operation mode setting circuit 133, and a current resonant converter drive circuit . The voltage detection circuit 132 includes an input voltage detection circuit 151 and an output voltage detection circuit 152 .

[0014] Here, the primary winding 52 and the secondary windings 71 and 72 form a transformer TR1. In this embodiment, the secondary windings 71 and 72 are divided into two parts at the center tap point by a center tap method, and for convenience of explanation, they will be referred to as the secondary winding 71 and the secondary winding 72, respectively. The secondary windings 71 and 72 may be integrated.

[0015] Moreover, the MOSFETs Q1, Q11 to Q14 which are the switching elements in this embodiment are a type of power semiconductor element. In this embodiment (and the following embodiments), the body diode of the MOSFET is also illustrated. In addition, the switching elements are not limited to MOSFETs, and power semiconductor elements such as bipolar transistors (or unipolar transistors), GaN transistors (Gallium Nitride Transistors), IGBTs (Insulated Gate Bipolar Transistors), and SiCFETs (Silicon Carbide Field Effect Transistors) may be used.

[0016] <Circuit connections> Two of the four terminals of the diode bridge 31 are connected to two terminals of the AC power supply 11, respectively. One of the other two terminals of the diode bridge 31 is connected to one end of the inductor 32. The other of the two other terminals of diode bridge 31 is connected to the source of MOSFET Q1, one end of capacitor 34, the source of MOSFET Q12, and the source of MOSFET Q14.

[0017] The other end of the inductor 32, the anode of the diode 33, and the drain of the MOSFET Q1 are connected. The cathode of diode 33, the drain of MOSFET Q11, the drain of MOSFET Q13, and the other end of capacitor 34 are connected.

[0018] The source of MOSFET Q11, the drain of MOSFET Q12 and one end of inductor 51 are connected together. The other end of the inductor 51 and one end of the primary winding 52 are connected to each other. The other end of the primary winding 52 and one end of the capacitor 53 are connected. The other end of capacitor 53 is connected to the source of MOSFET Q13 and the drain of MOSFET Q14.

[0019] One end of the secondary winding 71 and the anode of the diode 91 are connected. One end of the secondary winding 72 and the anode of the diode 92 are connected. The cathode of the diode 91, the cathode of the diode 92, one end of the capacitor 93, and one end of the resistor 12 are connected together. The other end of the secondary winding 71 and the other end of the secondary winding 72 are common to each other, and the common end is connected to the other end of the capacitor 93 and the other end of the resistor 12 .

[0020] Thus, in this embodiment, the current resonant converter B2 includes a leg in which MOSFET Q11 and MOSFET Q12 are connected in series, a leg in which MOSFET Q13 and MOSFET Q14 are connected in series, a transformer TR1 having a primary winding 52 and secondary windings 71, 72, a resonant inductor (inductor 51), a resonant capacitor (capacitor 53), and a rectifier circuit (a circuit including diodes 91, 92). The two legs are connected in parallel. In the primary circuit (primary circuit) of transformer TR1, both ends of a primary winding 52 are connected to the connection point between MOSFET Q11 and MOSFET Q12 and the connection point between MOSFET Q13 and MOSFET Q14 via a resonant inductor (inductor 51) and a resonant capacitor (capacitor 53). In the secondary circuit of the transformer TR1, both ends of secondary windings 71 and 72 are connected to the input terminals (anode of diode 91 and anode of diode 92) of the rectifier circuit.

[0021] The input voltage detection circuit 151 detects a voltage corresponding to an input voltage (Vin) to the power conversion device 1 (boost converter B1). In this embodiment, the input voltage detection circuit 151 has a function of detecting a voltage corresponding to the potential at the other end of the capacitor 34 (the potential at the cathode of the diode 33). The input voltage detection circuit 151 detects the voltage applied across the capacitor 34 as the voltage. The output voltage detection circuit 152 detects the output voltage. In this embodiment, the output voltage detection circuit 152 has a function of detecting a voltage corresponding to the potential at the other end of the capacitor 34 (the potential at the cathode of the diode 33). The output voltage detection circuit 152 detects the voltage applied across the capacitor 34 as the voltage. Instead of detection, it may be called measurement or measurement.

[0022] Here, the input voltage detection circuit 151 is required to detect a voltage corresponding to the input voltage (Vin). As another example, the input voltage detection circuit 151 may detect a voltage corresponding to the potential between one end of the AC power supply 11 and the diode bridge 31, or may detect a voltage corresponding to the potential between the diode bridge 31 and the inductor 32. In this embodiment, the input voltage detection circuit 151 detects a voltage that is referred to in order to determine the input voltage system (in this embodiment, the 200 VAC system, the 400 VAC system). It should be noted that a reference value (for example, a threshold value) related to the voltage is set according to the voltage detected by the input voltage detection circuit 151. That is, the threshold value can change according to the voltage detected as the voltage according to the input voltage.

[0023] Moreover, output voltage detection circuit 152 detects a voltage (output voltage) that is referenced in order to keep the output voltage of boost converter B1 constant. Therefore, the input voltage detection circuit 151 may detect a voltage at a point different from the voltage detected by the output voltage detection circuit 152 . In this embodiment, since the input voltage detection circuit 151 and the output voltage detection circuit 152 detect the same voltage, they may be shared.

[0024] The boost converter control circuit 131 has a function of outputting a control voltage to the gate of the MOSFET Q1. In this embodiment, the boost converter control circuit 131 performs control based on the voltage detected by the output voltage detection circuit 152 to maintain the output voltage of the boost converter B1 at a predetermined value. In this embodiment, the predetermined value is switchable between a plurality of values ​​(380V, 760V).

[0025] The operation mode setting circuit 133 has a function of setting the operation mode. Current resonant converter drive circuit 134 has a function of outputting a control voltage to the gate of MOSFET Q11 in accordance with the operation mode, and a function of outputting a control voltage to the gate of MOSFET Q12 in accordance with the operation mode. Current resonant converter drive circuit 134 also has a function of outputting a control voltage to the gate of MOSFET Q13 in accordance with the operation mode, and a function of outputting a control voltage to the gate of MOSFET Q14 in accordance with the operation mode.

[0026] In this embodiment, the input voltage detection circuit 151 detects a voltage corresponding to the input voltage (Vin), the operation mode setting circuit 133 sets an operation mode based on this detected voltage, and the boost converter control circuit 131 and the current resonant converter drive circuit 134 each operate based on the set operation mode. At this time, the operation mode setting circuit 133 determines a target boost voltage and notifies the determined target boost voltage to the boost converter control circuit 131. The boost converter control circuit 131 controls (feedback control) the MOSFET Q1 based on the voltage detected by the output voltage detection circuit 152 so that the output voltage becomes constant (the target boost voltage). Here, the control circuit 111 may be composed of, for example, a microcomputer. In this embodiment, for the sake of convenience, the control circuit 111 is shown to include a boost converter control circuit 131, a voltage detection circuit 132, an operation mode setting circuit 133, and a current resonant converter drive circuit 134, but the internal functions of the control circuit 111 do not necessarily have to be clearly divided. As another example, the functions of the control circuit 111 may be separated into a plurality of circuit sections.

[0027] <Examples of environments in which power conversion devices are used> An example of an environment in which the power conversion device 1 according to this embodiment is used will be described. In this embodiment, a description will be given assuming an environment in which the input voltage to the boost converter B1 of the power conversion device 1 can be at two or more different input voltage levels.

[0028] An example of such an environment is when the voltage of the power supply that supplies the input voltage to the boost converter B1 of the power conversion device 1 varies depending on the country. In this embodiment, an example is shown in which the public power supply in a first country is a system in which the voltage is an AC voltage of 200V (200VAC system), and the public power supply in a second country different from the first country is a system in which the voltage is an AC voltage of 400V (400VAC system).

[0029] Here, in a 200VAC system, for example, an alternating current (AC) of 200 to 240V is supplied. In addition, in a 400VAC system, for example, an alternating current (AC) of 400 to 480V is supplied. In this manner, in this embodiment, the input voltage to the boost converter B1 of the power conversion device 1 can be a wide input.

[0030] As a specific example, when the power conversion device 1 is used in a first country, a 200 VAC power supply is connected to the power conversion device 1 (boost converter B1) and the power conversion device 1 is started up. In this case, in this embodiment, the boost converter B1 outputs a DC voltage of 380V with a target boost voltage of 380V, and the current resonant converter B2 operates in the full-bridge mode (full-bridge operation).

[0031] Furthermore, when the power conversion device 1 is used in a second country, a 400 VAC power supply is connected to the power conversion device 1 (boost converter B1) and the power conversion device 1 is started up. In this case, in this embodiment, the boost converter B1 outputs a DC voltage of 760V with a target boost voltage of 760V, and the current resonant converter B2 operates in the half-bridge mode (half-bridge operation).

[0032] Here, in this embodiment, after being started, the power conversion device 1 does not change the set operation mode and operates while maintaining the set operation mode until a predetermined reset occurs. The reset occurs, for example, when the input voltage (or input power) to the power conversion device 1 (boost converter B1) is equal to or lower than a predetermined value for a predetermined period of time or more. The predetermined period of time or more is, for example, a time for causing the reset to occur that is determined in advance, such as when a breaker is turned off.

[0033] In other words, a reset occurs when the input voltage to the power conversion device 1 (boost converter B1) is essentially cut off, for example, because the breaker of the power supply that supplies the input voltage to the power conversion device 1 (boost converter B1) is turned off. The power conversion device 1 may be configured so that the occurrence of an instantaneous power outage in which the power supply is momentarily turned off is not treated as a reset.

[0034] In this embodiment, input voltage levels of 200 VAC and 400 VAC are exemplified, but other input voltage levels may be used as the multiple types of input voltage levels. Furthermore, in this embodiment, the output voltage level of the boost converter B1 is either 380V or 760V, but other output voltage levels may be used as the output voltage level. For example, in this embodiment, voltages with a ratio of 1:2 are used, such as 200V and 400V or 380V and 760V, but in other examples, such ratios may deviate as long as they do not cause any practical problems, and ratios such as 0.9:2 or 1:2.1 may be used.

[0035] In addition, this embodiment illustrates a case where the input voltage to the power conversion device 1 (boost converter B1) can be two or more input voltage levels depending on the country, but the present invention may be applied to a case where the input voltage can be two or more input voltage levels due to factors other than the country. In addition, in this embodiment, a case is described in which the input voltage to the power conversion device 1 (boost converter B1) can be two types of input voltage levels, but the present invention may be applied to a case in which the input voltage can be three or more types of input voltage levels. The power conversion device 1 according to this embodiment will be described in further detail below.

[0036] <Description of Related Art> First, the related art will be described with reference to FIGS. 2A to 2C, 3, and 4A to 4B.

[0037] FIG. 2A is a diagram showing an example of switching loss of a switching element (in this example, a MOSFET Q1). In the example of FIG. 2A, the input voltage of the boost converter is 400V alternating current (AC), and the output voltage of the boost converter is 760V direct current (DC). In the graph shown in FIG. 2A, the horizontal axis represents time, and the vertical axis represents the level of each index. The graph shows, as indicators, the characteristics of the drain-source voltage 3011 (Vds) of a switching element (in this example, MOSFET Q1), the characteristics of the drain current 3012 (Id) of the switching element (in this example, MOSFET Q1), and the characteristics of the switching loss 3013 arising from these.

[0038] FIG. 2B is a diagram showing another example of the switching loss of a switching element (in this example, MOSFET Q1). In the example of FIG. 2B, the input voltage of the boost converter is 200V alternating current (AC), and the output voltage of the boost converter is 760V direct current (DC). In the graph shown in FIG. 2B, the horizontal axis represents time, and the vertical axis represents the level of each index. The graph shows, as indicators, the characteristics of the drain-source voltage 3021 (Vds) of a switching element (in this example, MOSFET Q1), the characteristics of the drain current 3022 (Id) of the switching element, and the characteristics of the switching loss 3023 resulting from these.

[0039] FIG. 2C is a diagram showing another example of the switching loss of the switching element (in this example, the MOSFET Q1). In the example of FIG. 2C, the input voltage of the boost converter is 200V alternating current (AC), and the output voltage of the boost converter is 380V direct current (DC). In the graph shown in FIG. 2C, the horizontal axis represents time, and the vertical axis represents the level of each index. The graph shows, as indicators, the characteristics of the drain-source voltage 3031 (Vds) of a switching element (in this example, MOSFET Q1), the characteristics of the drain current 3032 (Id) of the switching element, and the characteristics of the switching loss 3033 resulting from these.

[0040] Here, the output voltage of the boost converter needs to be set higher than the upper limit of the input range, but in the case of a wide input, if the voltage is boosted from a low input voltage, switching loss increases and efficiency decreases. For example, when the input voltage is an AC voltage of 200V to 480V, the boost voltage (Vc1) of the boost converter is set to about 760V (Vc1>480×1.1×1.412=747V). Since the switching loss of a semiconductor is proportional to (voltage × current), the switching loss Psw is proportional to (output voltage Vc1 × input current Iin). In the case of hard switching, the switching loss when the input voltage is 200V is twice as much as the switching loss when the input voltage is 400V (see, for example, Figures 2A and 2B).

[0041] FIG. 3 is a diagram showing an example of switching loss and conduction loss of a switching element (in this example, a MOSFET Q1). FIG. 3 shows the degree of switching loss 3111 and conduction loss 3112 when the input voltage is 400 V AC and the output voltage is 760 V DC, the degree of switching loss 3121 and conduction loss 3122 when the input voltage is 200 V AC and the output voltage is 380 V DC, and the degree of switching loss 3131 and conduction loss 3132 when the input voltage is 200 V AC and the output voltage is 760 V DC. The units of the switching loss and the conduction loss are, for example, watts.

[0042] FIG. 4A is a diagram showing an example of the relationship between the operating frequency and the output voltage ratio of the current resonant converter. FIG. 4A shows the case where the coupling coefficient k of the transformer is k=0.75. 4A, the horizontal axis represents the operating frequency (Normalized Frequency) of the current resonant converter, and the vertical axis represents the output voltage ratio (output voltage Vo / input voltage Vi) of the current resonant converter. Here, the input voltage Vi to the current resonant converter is equal to the output voltage Vc1 from the previous boost converter. FIG. 4A shows a characteristic 3211 in the case of a low load and a characteristic 3212 in the case of a high load with respect to the relationship between the operating frequency and the output voltage ratio of the current resonant converter. In the example of FIG. 4A, the resonance frequency is set to 1.0.

[0043] FIG. 4B is a diagram showing another example of the relationship between the operating frequency and the output voltage ratio of the current resonant converter. FIG. 4B shows the case where the coupling coefficient k of the transformer is k=0.95. In the graph shown in FIG. 4B, the horizontal axis represents the operating frequency (Normalized Frequency) of the current resonant converter, and the vertical axis represents the output voltage ratio (output voltage Vo / input voltage Vi) of the current resonant converter. FIG. 4B shows a characteristic 3221 in the case of a low load and a characteristic 3222 in the case of a high load with respect to the relationship between the operating frequency and the output voltage ratio of the current resonant converter. Here, in the example of FIG. 4B, the resonant frequency is set to 1.0.

[0044] Here, if the output voltage of the boost converter is set to two stages, 380V and 760V, the downstream current resonant converter (DC-DC converter) will operate with this range as its input voltage, but generally, the efficiency of a current resonant converter decreases when a wide input is used. As shown in the example of Figure 4A, when the coupling coefficient k of the transformer is small, the output voltage ratio can be changed by more than a factor of two by changing the frequency, so the output voltage of the current resonant converter can be kept constant even if the voltage of the boost converter changes by a factor of two. However, when the coupling coefficient k is small, the excitation current of the transformer increases relatively, reducing efficiency. On the other hand, as shown in the example of Fig. 4B, when the coupling coefficient k of the transformer is large, the excitation current can be reduced and high efficiency can be achieved, but the voltage adjustment range is narrow and it cannot accommodate the output voltage range of the boost converter. However, even when the coupling coefficient k is large, if the operating frequency is fixed at the resonant frequency (around where the low load characteristic 3221 and the high load characteristic 3222 meet), there is almost no load fluctuation.

[0045] <Example of Control of Current Resonant Converter in This Embodiment> Next, an example of control of the current resonant converter B2 in this embodiment will be described with reference to FIGS. 5A to 5E.

[0046] In the power conversion device 1 according to the present embodiment, in a system (400 VAC system) in which the input voltage of the boost converter B1 is 400 V AC, the boost voltage (output voltage) is set to 760 V. On the other hand, in the power conversion device 1 according to the present embodiment, in a system (200 VAC system) in which the input voltage of the boost converter B1 is 200 V AC, the boost voltage (output voltage) is set to 380 V (= 760 V × 1 / 2). As a result, in the power conversion device 1 according to this embodiment, the switching losses in the 200 VAC system and the 400 VAC system can be made substantially equal (see, for example, FIGS. 2A and 2C).

[0047] Furthermore, in the power conversion device 1 of this embodiment, the MOSFETs Q11 to Q14 are controlled so that the primary side of the current resonant converter B2 is configured in a full-bridge configuration when the input voltage of the boost converter B1 is at a low level (Vin_L), and the primary side of the current resonant converter B2 is configured in a half-bridge configuration when the input voltage of the boost converter B1 is at a high level (Vin_H).

[0048] Here, when the input voltage (Vboost) of the current resonant converter B2 is at a high level, the primary side is put into half-bridge operation, so that the amplitude of the primary side voltage of the transformer TR1 becomes equal to the amplitude of full-bridge operation at a low level, and the output voltage also becomes equal. The input voltage (Vboost) is constant due to the control of the boost converter B1 even if the AC input voltage (Vac) or the load current varies. Therefore, for example, the output voltage (Vo) of the current resonant converter B2 can be stabilized without using feedback control by fixing the operating frequency to the resonant frequency (or near it).

[0049] FIG. 5A is a diagram showing an example of a relationship between an AC input voltage and an output voltage for illustrating switching between a full-bridge operation and a half-bridge operation according to the embodiment. In the graph shown in FIG. 5A, the horizontal axis represents the AC input voltage (Vac) of the boost converter B1, and the vertical axis represents the output voltage of the boost converter B1 (=the input voltage of the current resonant converter B2). FIG. 5A shows a voltage range from a minimum value Vin_L_min to a maximum value Vin_L_max as a voltage range when the AC input voltage (Vac) is at a low level (Vin_L). FIG. 5A also shows a voltage range from a minimum value Vin_H_min to a maximum value Vin_H_max as a voltage range when the AC input voltage (Vac) is at a high level (Vin_H). Where, Vin_L_max <Vin_H_minである。

[0050] When the AC input voltage (Vac) is in the voltage range from the low-level minimum value Vin_L_min to the maximum value Vin_L_max, the output voltage of the boost converter B1 becomes a low-level output voltage (V_L). On the other hand, when the AC input voltage (Vac) is in the voltage range from the high-level minimum value Vin_H_min to the high-level maximum value Vin_H_max, the output voltage of boost converter B1 becomes a high-level output voltage (V_H).

[0051] In this embodiment, a threshold voltage Vth is set between the low-level output voltage (V_L) and the high-level output voltage (V_H). The threshold voltage Vth may be, for example, the midpoint (or its vicinity) between the low-level output voltage (V_L) and the high-level output voltage (V_H), or may be another point.

[0052] FIG. 5B is a diagram showing the half-bridge operation in the current resonant converter according to the embodiment. FIG. 5C is a diagram showing the state of a full-bridge operation in the current resonant converter according to the embodiment.

[0053] For convenience of explanation, FIGS. 5B and 5C show an example of control of the current resonant converter B2. In this embodiment, when the input voltage of the current resonant converter B2 is at a high level (V_H), the current resonant converter B2 is controlled to perform a half-bridge operation as shown in Fig. 5B. In this embodiment, the high level (V_H) is 760V. Specifically, the control circuit 111 (operation mode setting circuit 133 and current resonant converter drive circuit 134) controls MOSFET Q13 to be in an open state, MOSFET Q14 to be in a conductive state, and MOSFET Q11 and MOSFET Q12 to perform a half-bridge operation.

[0054] On the other hand, in this embodiment, when the input voltage of the current resonant converter B2 is at a low level (V_L), the current resonant converter B2 is controlled to perform a full-bridge operation as shown in Fig. 5C. In this embodiment, the low level (V_L) is 380V. Specifically, the control circuit 111 (the operation mode setting circuit 133 and the current resonant converter drive circuit 134) controls the four MOSFETs Q11 to Q14 to perform a full-bridge operation.

[0055] FIG. 5D is a diagram illustrating an example of a voltage applied to the primary side of the transformer TR1 during half-bridge operation according to the embodiment. FIG. 5D shows an example of voltage Vx, which is the voltage applied to the primary side of transformer TR1 during the half-bridge operation shown in FIG. 5B (in this embodiment, voltage 3311 applied across the portion including inductor 51, primary winding 52, and capacitor 53). Specifically, the voltage applied to the primary side is a periodic pulse voltage 3311. The voltage 3311 has two levels: 0 V and +760 V (Vboost). Taking the midpoint of this voltage range (1 / 2 × Vboost) as the reference, it becomes a pulse with a level of ±380 V.

[0056] FIG. 5E is a diagram illustrating an example of a voltage applied to the primary side of the transformer TR1 during full-bridge operation according to the embodiment. FIG. 5E shows an example of voltage Vx, which is the voltage applied to the primary side of transformer TR1 during full-bridge operation as shown in FIG. 5C (in this embodiment, voltage 3312 applied across the portion including inductor 51, primary winding 52, and capacitor 53). Specifically, the voltage applied to the primary side is a periodic pulse voltage 3312. The level of the voltage 3312 has two values, −380V (−Vboost) and +380V (+Vboost). This results in a pulse with a level of ±380V.

[0057] <Drive signal switching circuit> The drive signal switching circuit will be described with reference to FIGS. 6A and 6B. FIG. 6A is a diagram showing an example of a drive signal switching circuit 201 according to an embodiment. The drive signal switching circuit 201 switches the operation mode of the current resonant converter B2 between a full-bridge mode and a half-bridge mode. In this embodiment, the control circuit 111 (for example, the current resonant converter drive circuit 134) includes a drive signal switching circuit 201.

[0058] The drive signal switching circuit 201 includes a NOT circuit 211, a NOR circuit 212, and an OR circuit 213. Here, the control circuit 111 has an oscillator (not shown), and the output from the oscillator will be described as an oscillator output OSC.

[0059] Moreover, the control circuit 111 generates an input voltage determination signal Vsel indicating either the 200 VAC system or the 400 VAC system as a result of the input voltage determination. In this embodiment, when the input voltage detected by the input voltage detection circuit 151 is at a low level, the control circuit 111 sets the input voltage determination signal Vsel to a low level signal, and when the input voltage detected by the input voltage detection circuit 151 is at a high level, the control circuit 111 sets the input voltage determination signal Vsel to a high level signal.

[0060] In the drive signal switching circuit 201, the oscillator output OSC is used as a switch drive signal (a control voltage applied to the gate) for the MOSFET Q11. The oscillator output OSC is input to the input terminal of a NOT circuit 211, and the output from the output terminal of the NOT circuit 211 (a signal obtained by inverting the oscillator output OSC) is used as a switch drive signal for MOSFET Q12 (a control voltage applied to the gate).

[0061] Furthermore, the oscillator output OSC and the input voltage determination signal Vsel are input to two input terminals of a NOR circuit 212, and the output from the output terminal of the NOR circuit 212 is used as a switch drive signal (control voltage applied to the gate) for the MOSFET Q13. Furthermore, the oscillator output OSC and the input voltage determination signal Vsel are input to two input terminals of an OR circuit 213, respectively, and the output from the output terminal of the OR circuit 213 is used as a switch drive signal (control voltage applied to the gate) for MOSFET Q14.

[0062] FIG. 6B is a diagram showing an example of input / output signals of the drive signal switching circuit 201 according to the embodiment. In the graph shown in FIG. 6B, the horizontal axis represents time, and the vertical axis represents the voltage level of each signal.

[0063] As input signals to the drive signal switching circuit 201, a signal 3511 corresponding to the oscillator output OSC and a signal 3512 corresponding to the input voltage determination signal Vsel are shown. Also shown as output signals of drive signal switching circuit 201 are signal 3521 of a control voltage for MOSFET Q11, signal 3522 of a control voltage for MOSFET Q12, signal 3523 of a control voltage for MOSFET Q13, and signal 3524 of a control voltage for MOSFET Q14. These signals enable the current resonant converter B2 to switch between full-bridge operation and half-bridge operation.

[0064] It should be noted that the circuits and signals shown in FIGS. 6A and 6B are merely examples, and any other configuration may be used as the configuration for switching between full-bridge operation and half-bridge operation in the current resonant converter B2.

[0065] <Example of timing for switching the operating mode of a current resonant converter> In this embodiment, at the moment when the primary side of the current resonant converter B2 is switched between the full-bridge configuration and the half-bridge configuration, it is conceivable that a fluctuation occurs in the output voltage and an overcurrent and an overvoltage occur in the elements. Therefore, in this embodiment, the bridge operation is not switched during operation of the power conversion device 1. For example, the power conversion device 1 is controlled to select an operation mode of full-bridge operation when the input voltage is lower than a reference value (threshold) at start-up, and is controlled to select an operation mode of half-bridge operation when the input voltage is higher than the reference value (threshold) at start-up. After this selection is made, the power conversion device 1 fixes the selected operation mode even if the input voltage fluctuates. In the power conversion device 1, when a reset operation is performed due to input interruption, a new operation mode is selected when the power conversion device 1 is started up thereafter. In other words, when the reset operation is performed in the power conversion device 1, the operation mode is in a state in which it can be changed.

[0066] <Example of power conversion device operation> An example of the operation of the power conversion device 1 according to this embodiment will be shown with reference to FIG. The boost converter B1 boosts the input voltage Vin input to an input terminal (in this embodiment, a terminal connected to the AC power supply 11) to produce an output voltage (voltage Vc1), and outputs the output voltage while charging an output capacitor (capacitor 34) connected to an output terminal (in this embodiment, a terminal connected to the current resonant converter B2).

[0067] In this embodiment, the boost converter B1 is configured as an AC input, but as another example, it may be configured as a DC input. In addition, in this embodiment, a PFC (Power Factor Correction) converter that performs power factor correction control (PFC control) is used as the boost converter B1, but the PFC function is not necessarily provided.

[0068] The output voltage detection circuit 152 detects the voltage of the output capacitor (capacitor 34). The boost converter control circuit 131 controls the boost converter B1 based on the voltage detected by the output voltage detection circuit 152.

[0069] The input voltage detection circuit 151 detects a voltage corresponding to the input voltage (Vin) to the boost converter B1. Operation mode setting circuit 133 sets the output voltage of boost converter B1 to a low level (low level mode) or a high level (high level mode) according to the value of the voltage detected by input voltage detection circuit 151.

[0070] The control circuit 111 (current resonant converter drive circuit 134) controls the full-bridge current resonant converter B2 in accordance with the level (mode) set by the operation mode setting circuit 133. Specifically, the control circuit 111 (current resonant converter drive circuit 134) controls so as to operate in full-bridge mode when at low level, and controls so as to operate in half-bridge mode when at high level.

[0071] In this embodiment, the set level is determined at any timing after the input voltage is input, and the operation mode of the current resonant converter is maintained until the set level is reset.

[0072] <Example of fixed frequency operation of current resonant converter> The current resonant converter B2 may be configured to operate at a fixed frequency. Specifically, the switching elements (MOSFETs Q11 to Q14) operating in the full-bridge mode or half-bridge mode are configured to operate at a fixed frequency, rather than operating under feedback control of the output voltage output from the secondary circuit (control that feeds back the voltage on the secondary side of the transformer TR1). The fixed frequency is, for example, a frequency near the resonant frequency (see, for example, FIG. 4B).

[0073] In a configuration in which the current resonant converter B2 operates at a fixed frequency, a control circuit for changing the frequency is not required, and the control circuit can be simplified. Even if the frequency is variable, if the control point is constant, the operation is the same as that at a fixed frequency. As a result, the current resonant converter B2 operates at 380V when the input is at a low level (380V), and operates at 760V when the input is at a high level (760V).

[0074] As described above, in the power conversion system A1 of this embodiment, in the power conversion device 1, in a configuration in which the current resonant converter B2 is provided in the subsequent stage of the boost converter B1, high efficiency can be achieved even when the input voltage of the boost converter B1 can be two types of input voltage levels.

[0075] In this embodiment, the secondary circuit of the current resonant converter B2 includes a rectifier circuit using two diodes 91 and 92, but may include another rectifier circuit. In addition, in the present embodiment, the resistor 12 is provided on the output side of the current resonant converter B2. However, instead of the resistor 12, any other circuit may be connected.

[0076] Second embodiment A second embodiment will be described. [Power conversion system] FIG. 7 is a diagram showing an example of a circuit configuration of a power conversion system A11 according to the second embodiment. Here, in this embodiment, for convenience of explanation, components similar to those shown in FIG. 1 according to the first embodiment are denoted by the same reference numerals, and detailed explanations thereof will be omitted.

[0077] The power conversion system A11 according to this embodiment includes a power conversion device 301, an AC power supply 11, and a resistor 12. The power conversion device 301 includes a boost converter B11 and a current resonant converter B2. In the example of FIG. 7, the control circuit 111 shown in FIG. 1 is omitted.

[0078] The configuration and operation of the power conversion system A11 of this embodiment differs, generally speaking, from the configuration and operation of the power conversion system A1 of the first embodiment shown in FIG. 1 in that the boost converter B11 is equipped with an inrush current limiting circuit 310. The inrush current limiting circuit 310 includes a resistor 311 and a switch 312 . A resistor 311 and a switch 312 are connected in parallel between one terminal of the AC power supply 11 and the diode bridge 31 .

[0079] In this embodiment, for ease of explanation, the inrush current limiting circuit 310 provided in the upstream stage of the boost converter B11 is considered to be a circuit part of the boost converter B11. However, for example, the inrush current limiting circuit 310 may be considered to be a circuit separate from the boost converter B11.

[0080] <Example of inrush current limiting circuit operation> The boost converter B11 has an inrush current limiting circuit 310 in the path that charges the output capacitor (capacitor 34). At startup, the control circuit 111 (for example, the boost converter control circuit 131) controls the switch 312 of the inrush current limiting circuit 310 to be open (OFF) so that the inrush current is suppressed by passing through the resistor 311. Thereafter, at a predetermined timing when the inrush current terminates, the control circuit 111 (for example, the boost converter control circuit 131) controls the switch 312 of the inrush current limiting circuit 310 to be conductive (ON).

[0081] In this embodiment, the control circuit 111 (e.g., the boost converter control circuit 131) determines a target boost voltage of the boost converter B11 according to the value of the voltage detected by the input voltage detection circuit 151 after the inrush current at start-up has ceased and the inrush current limitation of the inrush current limiting circuit 310 has been released (the switch 312 has been turned on). This determination process may be, for example, a process of selecting one target boost voltage from a plurality of target boost voltages (380V or 760V in this embodiment). In this embodiment, the start-up time indicates the time when the AC power supply 11 starts up (rises up).

[0082] <Example of boost voltage selection process> FIG. 8 is a diagram illustrating a process flow illustrating an example of a boost voltage selection process according to the second embodiment. The control circuit 111 performs a process of selecting a boost voltage based on the result of detection of the input voltage. In the graph shown in FIG. 8, the horizontal axis represents time, and the vertical axis represents the voltage Vc1 applied across the capacitor . The horizontal axis of the graph indicates time t0 to time t3. The vertical axis of the graph shows, for the boost converter B11, the low-level input voltage Vin_L, the low-level output voltage V_L, the threshold voltage Vth, the high-level input voltage Vin_H, and the high-level output voltage V_H.

[0083] Here, the range of the low-level input voltage Vin_L is represented by the range of Vin_L_min to Vin_L_max. Also, the midpoint of this range is represented by Vin_L_typ. Also, the range of the high-level input voltage Vin_H is represented by the range of Vin_H_min to Vin_H_max. Also, the midpoint of this range is represented by Vin_H_typ.

[0084] In the example of FIG. 8, characteristics 3411 when the input voltage is Vin_L_min, characteristics 3412 when the input voltage is Vin_L_typ, characteristics 3413 when the input voltage is Vin_L_max, characteristics 3431 when the input voltage is Vin_H_min, characteristics 3432 when the input voltage is Vin_H_typ, and characteristics 3433 when the input voltage is Vin_H_max are shown.

[0085] Also, the threshold voltage Vth is a level that serves as a reference for switching the operation mode. In this embodiment, it is set such that (Vin_L_max < Vth < Vin_H_min).

[0086] At time t0, an input voltage is applied to the power conversion device 301. First, in the power conversion device 301, the switch 312 of the inrush current limiting circuit 310 is opened, and the boost converter B11 charges the output capacitor (capacitor 34) via the inrush current prevention resistor (resistor 311).

[0087] Thereafter, at time t1, in the power conversion device 301, the switch 312 parallel to the inrush current prevention resistor (resistor 311) is made conductive (the switching element is turned on). At this time, the voltage of the output capacitor (capacitor 34) further rises by the difference between the voltage applied to the inrush current prevention resistor (resistor 311) and the voltage applied when switch 312 is in the conductive state.

[0088] After that, at time t2, the power conversion device 301 detects and determines the input voltage. In other words, in the power conversion device 301, when it is determined that the input voltage Vin (in this embodiment, the voltage Vc1 applied across the capacitor 34) is lower than the threshold voltage Vth serving as a reference value, the target value of the boost voltage is set to a low-level output voltage V_L, and the current resonant converter B2 is controlled to perform full-bridge operation. On the other hand, in the power conversion device 301, when it is determined that the input voltage Vin (in this embodiment, the voltage Vc1 applied across the capacitor 34) is higher than the threshold voltage Vth serving as a reference value, the target value of the boost voltage is set to a high-level output voltage V_H, and the current resonant converter B2 is controlled to perform half-bridge operation. In this embodiment, the input voltage Vin (in this embodiment, the voltage Vc1 applied across the capacitor 34) is set so that it will never be equal to the threshold voltage Vth, which is the reference value. However, if such a case occurs, the input voltage Vin may be set to transition to a predetermined operating mode (in this embodiment, either full-bridge mode or half-bridge mode).

[0089] Then, at time t3, the power conversion device 301 performs control so that the boost circuit (boost converter B11) starts operating and outputs the set target boost voltage value, and also starts operating the current resonant circuit (current resonant converter B2) in accordance with the set target boost voltage value.

[0090] In this manner, in the power conversion device 301 of this embodiment, the output capacitor (capacitor 34) is charged from time t0 to time t1, a voltage corresponding to the input voltage of the boost converter B11 (in this embodiment, the voltage Vc1 across the capacitor 34) is detected at time t2, which is after time t1, and the system to be adapted (200 VAC system and 400 VAC system) is switched at time t3.

[0091] As described above, in the power conversion system A11 according to this embodiment, in the power conversion device 301, in a configuration in which a current resonant converter B2 is provided in a subsequent stage of the boost converter B11, high efficiency can be achieved even when the input voltage of the boost converter B11 can be two different input voltage levels.

[0092] Third embodiment A third embodiment will be described. [Power conversion system] FIG. 9A is a diagram showing an example of a circuit configuration of a power conversion system A21 according to the third embodiment. Here, in this embodiment, for convenience of explanation, components similar to those shown in FIG. 7 according to the second embodiment are denoted by the same reference numerals, and detailed explanations thereof will be omitted.

[0093] The power conversion system A21 according to this embodiment includes a power conversion device 401, an AC power supply 11, and a resistor 12. The power conversion device 401 includes a boost converter B11 and a current resonant converter B12. In the example of FIG. 9A, the control circuit 111 shown in FIG. 1 is omitted.

[0094] The configuration and operation of the power conversion system A21 according to this embodiment differs, generally speaking, from the configuration and operation of the power conversion system A11 according to the second embodiment shown in FIG. 7 in that switching between three operating modes is performed, and also in the configuration and operation of the secondary side of the current resonant converter B12.

[0095] The current resonant converter B12 includes a secondary winding 411, an inductor 431, a capacitor 432, four diodes 451 to 454 which are rectifying elements, a switch 471, and a capacitor 472 on the secondary side. Here, the switch 471 may be configured using, for example, a semiconductor switch element, or may be configured using a mechanical switch (for example, a relay, etc.). Furthermore, the primary winding 52 and the secondary winding 411 form a transformer TR11. In this embodiment, a full-bridge rectifier circuit is provided.

[0096] <Circuit connections> The connections of the secondary circuit of the current resonant converter B12 will be described. One end of the secondary winding 411 and one end of the inductor 431 are connected. The other end of the secondary winding 411 and one end of the capacitor 432 are connected. The other end of the inductor 431 is connected to an anode of a diode 451 and a cathode of a diode 452 . The other end of the capacitor 432, the anode of the diode 453, the cathode of the diode 454, and one end of the switch 471 are connected. The cathode of the diode 451, the cathode of the diode 453, one end of the capacitor 472, and one end of the resistor 12 are connected together. The anode of the diode 452, the anode of the diode 454, the other end of the switch 471, the other end of the capacitor 472, and the other end of the resistor 12 are connected.

[0097] Thus, in the secondary circuit of the current resonant converter B12, the rectifier circuit includes a leg in which the diode 451 and the diode 452 are connected in series, and a leg in which the diode 453 and the diode 454 are connected in series. The two legs are connected in parallel. Both ends of the secondary winding 411 are connected to both connection points, namely, the connection point between the diodes 451 and 452 and the connection point between the diodes 453 and 454, via the inductor 431 and the capacitor 432.

[0098] The control circuit 111 controls the on / off switching of the switch 471. The control circuit 111 can switch the rectifier circuit to a voltage-doubling rectifier circuit by short-circuiting (i.e., turning on the switch 471) any one of the four diodes 451 to 454 (in this embodiment, the diode 454) with the switch 471.

[0099] <Example of a CLLC-type resonant circuit> In the example of FIG. 9A, the current resonant converter B12 is of the CLLC type. The CLLC resonant circuit in the current resonant converter B12 is composed of the capacitor 53 and the inductor 51 in the primary-side circuit and the inductor 431 and the capacitor 432 in the secondary-side circuit. In this way, the input terminal of the rectifier circuit and both ends of the secondary winding 411 are connected via the resonant inductor (inductor 431) and the resonant capacitor (capacitor 432).

[0100] <Example of using leakage inductance> For example, one or both of the resonant inductor (inductor 51) in the primary-side circuit of the transformer TR11 and the resonant inductor (inductor 431) in the secondary-side circuit of the transformer TR11 may be the leakage inductance of the transformer TR11.

[0101] <Example of operation> FIG. 9B is a diagram showing a table 5011 representing an example of the relationship between the input voltage, the output voltage of the boost converter B11, and the operation modes of the current resonant converter B12 according to the third embodiment. In this embodiment, three operation modes are switchable. In this embodiment, the operation mode setting circuit 133 sets one of the three operation modes. In this embodiment, the three operation modes are an operation mode corresponding to a 100 VAC system, an operation mode corresponding to a 200 VAC system, and an operation mode corresponding to a 400 VAC system.

[0102] In this embodiment, when the input voltage to the power conversion device 401 (boost converter B11) is 100-120 VAC (100 VAC), the output voltage of the boost converter B11 is 190 VDC, the primary side of the current resonant converter B12 is controlled to perform full-bridge operation, and the secondary side of the current resonant converter B12 is controlled to perform voltage doubler rectification operation.

[0103] Furthermore, in this embodiment, when the input voltage to the power conversion device 401 (boost converter B11) is 200-240 VAC (200 VAC system), the output voltage of the boost converter B11 is 380 VDC, the primary side of the current resonant converter B12 is controlled to perform full-bridge operation, and the secondary side of the current resonant converter B12 is controlled to perform full-bridge rectification operation.

[0104] Furthermore, in this embodiment, when the input voltage to the power conversion device 401 (boost converter B11) is 400-480 VAC (400 VAC system), the output voltage of the boost converter B11 is 760 VDC, the primary side of the current resonant converter B12 is controlled to perform half-bridge operation, and the secondary side of the current resonant converter B12 is controlled to perform full-bridge rectification operation.

[0105] Thus, in the power conversion device 401 of this embodiment, when the voltage detected by the input voltage detection circuit 151 (voltage corresponding to the input voltage at start-up) is lower than the specified voltage Vth1, the primary side of the current resonant converter B12 is controlled in full-bridge mode, and the secondary side rectifier circuit is short-circuited by the switch 471 to operate as a voltage doubler rectifier circuit. Furthermore, in the power conversion device 401 according to this embodiment, when the voltage detected by the input voltage detection circuit 151 (voltage corresponding to the input voltage at the time of startup) is higher than the specified voltage Vth1 and lower than the specified voltage Vth2, the primary side of the current resonant converter B12 is controlled in full-bridge mode, and the rectifier circuit on the secondary side is not short-circuited by the switch 471 and operates as a full-bridge rectifier circuit. Furthermore, in the power conversion device 401 according to this embodiment, when the voltage detected by the input voltage detection circuit 151 (voltage corresponding to the input voltage at the time of startup) is higher than the specified voltage Vth2, the primary side of the current resonant converter B12 is controlled in half-bridge mode, and the rectifier circuit on the secondary side is not short-circuited by the switch 471 and operates as a full-bridge rectifier circuit.

[0106] When the voltage detected by the input voltage detection circuit 151 (the voltage corresponding to the input voltage at the time of startup) is equal to the specified voltage Vth1, for example, the circuit may be configured to perform control similar to that performed when the voltage is lower than the specified voltage Vth1, or the circuit may be configured to perform control similar to that performed when the voltage is higher than the specified voltage Vth1. In addition, when the voltage detected by the input voltage detection circuit 151 (the voltage corresponding to the input voltage at the time of startup) is equal to the specified voltage Vth2, for example, the circuit may be configured to perform control similar to that performed when the voltage is lower than the specified voltage Vth2, or the circuit may be configured to perform control similar to that performed when the voltage is higher than the specified voltage Vth2.

[0107] As described above, in the power conversion system A21 according to this embodiment, in the power conversion device 401, in a configuration including a current resonant converter B12 in a downstream stage of the boost converter B11, high efficiency can be achieved even when the input voltage of the boost converter B11 can be two or more types of input voltage levels.

[0108] (Fourth embodiment) A fourth embodiment will be described. [Power conversion system] FIG. 10 is a diagram showing an example of a circuit configuration of a power conversion system A101 according to the fourth embodiment. The power conversion system A101 includes a power conversion device 601, a three-phase AC power supply unit 611, and a resistor 612. The power conversion device 601 includes a boost converter B101, a current resonant converter B102, and a control circuit 111a. The current resonant converter B102 is connected to the rear stage of the boost converter B101. In this embodiment, the input voltage of the boost converter B101 is a three-phase AC voltage.

[0109] Here, broadly speaking, the configuration and operation of the power conversion system A101 of this embodiment differs from the configuration and operation of the power conversion system A11 of the second embodiment in that three-phase AC is input to the power conversion device 601, but is otherwise similar. The control circuit 111a includes, for example, functions similar to those of the control circuit 111 shown in Fig. 1. For this reason, in this embodiment, with regard to the control circuit 111a, illustrations and detailed descriptions of functions similar to those of the control circuit 111 shown in Fig. 1 will be omitted.

[0110] In this embodiment, the AC power supply unit 611 and the resistor 612 are external circuits of the power conversion device 601. However, as another example, a configuration in which one or both of the AC power supply unit 611 and the resistor 612 are internal circuits of the power conversion device 601 may be used. For example, when both the AC power supply unit 611 and the resistor 612 are circuits inside the power conversion device 601, the power conversion system A101 according to this embodiment and the power conversion device 601 are the same.

[0111] The AC power supply unit 611 is a power supply that outputs three-phase AC, and is configured by combining three single-phase AC power supplies 611a, 611b, and 611c. The boost converter B101 includes three inrush current limiting circuits 630a, 630b, and 630c, and three inductors 651a, 651b, and 651c corresponding to the three phases, respectively. The boost converter B101 also includes six MOSFETs Q101-Q106 and a capacitor 652.

[0112] The inrush current limiting circuit 630a is composed of a resistor 631a and a switch 632a connected in parallel. The inrush current limiting circuit 630b is composed of a resistor 631b and a switch 632b connected in parallel. The inrush current limiting circuit 630c is composed of a resistor 631c and a switch 632c connected in parallel.

[0113] In this embodiment, for ease of explanation, the inrush current limiting circuits 630a to 630c provided in the upstream stage of the boost converter B101 are assumed to be circuit parts of the boost converter B101. However, for example, the inrush current limiting circuits 630a to 630c may be regarded as circuits separate from the boost converter B101.

[0114] A first phase terminal of AC power supply unit 611 is connected to the source of MOSFET Q101 and the drain of MOSFET Q102 via inrush current limiting circuit 630a and inductor 651a. A second phase terminal of AC power supply unit 611 is connected to the source of MOSFET Q103 and the drain of MOSFET Q104 via inrush current limiting circuit 630b and inductor 651b. A third phase terminal of AC power supply unit 611 is connected to the source of MOSFET Q105 and the drain of MOSFET Q106 via inrush current limiting circuit 630c and inductor 651c.

[0115] The drain of MOSFET Q101, the drain of MOSFET Q103, the drain of MOSFET Q105 and one end of capacitor 652 are connected. The source of MOSFET Q102, the source of MOSFET Q104, the source of MOSFET Q106, and the other end of capacitor 652 are connected together.

[0116] The current resonant converter B102 includes four MOSFETs Q111 to Q114, an inductor 671, a primary winding 672, a capacitor 673, secondary windings 711 and 712, two diodes 731 and 732, and a capacitor 733. Here, the primary winding 672 and the secondary windings 711 and 712 constitute a transformer TR101. In this embodiment, the secondary windings 711 and 712 are divided into two parts at the center tap point by a center tap method, and for convenience of explanation, they will be referred to as the secondary winding 711 and the secondary winding 712, respectively. The secondary windings 711 and 712 may be integrated.

[0117] The internal circuit configuration of the current resonant converter B102 is similar to the internal circuit configuration of the current resonant converter B2 shown in FIG. In addition, the connection relationship in which the current resonant converter B102 is connected between the capacitor 652 and resistor 612 of the boost converter B101 is similar to the connection relationship in which the current resonant converter B2 is connected between the capacitor 34 and resistor 12 of the boost converter B11 shown in Figure 7.

[0118] Control circuit 111a detects the output voltage (the voltage across capacitor 652) of boost converter B101, and controls the control voltage applied to the gates of six MOSFETs Q101-Q106 in accordance with the three-phase AC based on the detected voltage. In addition, the control circuit 111a controls the switches 632a, 632b, and 632c of the three inrush current limiting circuits 630a, 630b, and 630c.

[0119] The control circuit 111a detects a voltage corresponding to the input voltage, and sets the operation mode (full-bridge mode or half-bridge mode) of the current resonant converter B102 based on the detected voltage. Control circuit 111a controls the control voltage applied to the gates of MOSFETs Q111-Q114 of current resonant converter B102 according to the set operation mode.

[0120] As described above, in the power conversion system A101 according to this embodiment, in the power conversion device 601, in a configuration in which the current resonant converter B102 is provided in the subsequent stage of the boost converter B101, high efficiency can be achieved even when the input voltage of the boost converter B101 can be two different input voltage levels.

[0121] Fifth embodiment A fifth embodiment will be described. [Power conversion system] FIG. 11 is a diagram showing an example of a circuit configuration of a power conversion system A111 according to the fifth embodiment. Here, in this embodiment, for convenience of explanation, components similar to those shown in FIG. 10 according to the fourth embodiment are denoted by the same reference numerals, and detailed explanations thereof will be omitted.

[0122] The power conversion system A111 according to this embodiment includes a power conversion device 801, an AC power supply unit 611, and a resistor 612. The power conversion device 801 includes a boost converter B101 and a current resonant converter B112. In the example of FIG. 11, the control circuit 111a shown in FIG. 10 is omitted.

[0123] The configuration and operation of the power conversion system A111 according to this embodiment differs, generally speaking, from the configuration and operation of the power conversion system A101 according to the fourth embodiment shown in FIG. 10 in terms of the configuration and operation of the secondary side of the current resonant converter B112.

[0124] The current resonant converter B112 includes a secondary winding 811, an inductor 831, a capacitor 832, four diodes 851 to 854 which are rectifying elements, and a capacitor 833 on the secondary side. Here, the primary winding 672 and the secondary winding 811 constitute a transformer TR111. In this embodiment, a full-bridge rectifier circuit is provided.

[0125] <Connection relationship of the circuit> The connection relationship of the secondary-side circuit of the current resonance type converter B112 will be described. One end of the secondary winding 811 and one end of the inductor 831 are connected. The other end of the secondary winding 811 and one end of the capacitor 832 are connected. The other end of the inductor 831, the anode of the diode 851, and the cathode of the diode 852 are connected. The other end of the capacitor 832, the anode of the diode 853, and the cathode of the diode 854 are connected. The cathode of the diode 851, the cathode of the diode 853, one end of the capacitor 833, and one end of the resistor 612 are connected. The anode of the diode 852, the anode of the diode 854, the other end of the capacitor 833, and the other end of the resistor 612 are connected.

[0126] Thus, in the secondary-side circuit of the current resonance type converter B112, the rectifier circuit includes a leg in which the diodes 851 and 852 are connected in series, and a leg in which the diodes 853 and 854 are connected in series. These two legs are connected in parallel. Both ends of the secondary winding 811 are connected to both connection points of the connection point between the diodes 851 and 852 and the connection point between the diodes 853 and 854 via the inductor 831 and the capacitor 832.

[0127] <Example of CLLC resonance circuit> In the example of FIG. 11, the current resonance type converter B112 is of the CLLC type. The CLLC resonance circuit in the current resonance type converter B112 is composed of the capacitor 673 and the inductor 671 in the primary-side circuit, and the inductor 831 and the capacitor 832 in the secondary-side circuit. In this manner, the input terminal of the rectifier circuit and both ends of the secondary winding 811 are connected via the resonant inductor (inductor 831) and the resonant capacitor (capacitor 832).

[0128] <Example of using leakage inductance> For example, one or both of the resonant inductor (inductor 671) of the primary circuit of the transformer TR111 and the resonant inductor (inductor 831) of the secondary circuit of the transformer TR111 may be a leakage inductance of the transformer TR111.

[0129] As described above, in the power conversion system A111 according to this embodiment, in the power conversion device 801, in a configuration including a current resonant converter B112 in a stage subsequent to the boost converter B101, high efficiency can be achieved even when the input voltage of the boost converter B101 can be two different input voltage levels.

[0130] Sixth embodiment A sixth embodiment will now be described. [Power conversion system] FIG. 12 is a diagram showing an example of a circuit configuration of a power conversion system A211 according to the sixth embodiment. Here, in this embodiment, for convenience of explanation, components similar to those shown in FIG. 11 according to the fifth embodiment are denoted by the same reference numerals, and detailed explanations thereof will be omitted.

[0131] The power conversion system A211 according to this embodiment includes a power conversion device 901, an AC power supply unit 611, and a resistor 612. The power conversion device 901 includes a boost converter B101 and a current resonant converter B212. In the example of FIG. 12, the control circuit 111a shown in FIG. 10 is omitted.

[0132] The configuration and operation of the power conversion system A211 according to this embodiment differs, generally speaking, from the configuration and operation of the power conversion system A111 according to the fifth embodiment shown in FIG. 11 in terms of the configuration and operation of the secondary side of the current resonant converter B212.

[0133] A power conversion system A211 according to this embodiment generally includes four MOSFETs 911-914 instead of the four diodes 851-854 in the power conversion system A111 according to the fifth embodiment shown in FIG. These four MOSFETs 911 to 914 form a rectifier circuit. In this embodiment, the control circuit 111a has a function of controlling the control voltage applied to the gates of these four MOSFETs 911-914.

[0134] As described above, in the power conversion system A211 according to this embodiment, in the power conversion device 901, in a configuration including a current resonant converter B212 in a downstream stage of the boost converter B101, high efficiency can be achieved even when the input voltage of the boost converter B101 can be two different input voltage levels.

[0135] (Regarding the above embodiment) A program for implementing the functions of any of the components in any of the above-described devices may be recorded in a computer-readable recording medium, and the program may be read into a computer system and executed. The term "computer system" as used herein includes hardware such as an operating system or peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CDs (Compact Discs)-ROMs (Read Only Memory), and storage devices such as hard disks built into computer systems. The term "computer-readable recording medium" also refers to storage devices that hold a program for a certain period of time, such as volatile memory in a computer system that is a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. The volatile memory may be, for example, a RAM (Random Access Memory). The recording medium may be, for example, a non-transitory recording medium.

[0136] The above-mentioned program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium or by transmission waves in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has a function of transmitting information, such as a network such as the Internet or a communication line such as a telephone line. The above program may be for implementing some of the above functions. Furthermore, the above program may be a so-called differential file that can implement the above functions in combination with a program already recorded in the computer system. The differential file may be called a differential program.

[0137] In addition, the function of any of the components in any of the above-described devices may be realized by a processor. For example, each process in the embodiment may be realized by a processor that operates based on information such as a program and a computer-readable recording medium that stores information such as a program. Here, the functions of each part of the processor may be realized by individual hardware, or the functions of each part may be realized by integrated hardware. For example, the processor may include hardware, and the hardware may include at least one of a circuit that processes digital signals and a circuit that processes analog signals. For example, the processor may be configured using one or more circuit devices mounted on a circuit board, or one or both of one or more circuit elements. An IC (Integrated Circuit) or the like may be used as the circuit device, and a resistor or a capacitor or the like may be used as the circuit element.

[0138] Here, the processor may be, for example, a CPU. However, the processor is not limited to a CPU, and various processors such as a GPU (Graphics Processing Unit) or a DSP (Digital Signal Processor) may be used. The processor may be, for example, a hardware circuit using an ASIC (Application Specific Integrated Circuit). The processor may be, for example, a plurality of CPUs, or a hardware circuit using a plurality of ASICs. The processor may be, for example, a combination of a plurality of CPUs and a hardware circuit using a plurality of ASICs. The processor may include, for example, one or more of an amplifier circuit or a filter circuit that processes an analog signal.

[0139] Although the embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of this disclosure are also included.

[0140] [Note] [Configuration Example 1] to [Configuration Example 8] are shown.

[0141] [Configuration example 1] A boost converter, a current resonant converter connected to a downstream stage of the boost converter, and a control circuit, the boost converter boosts an input voltage to produce an output voltage, and outputs the output voltage while charging a first output capacitor with the output voltage; the control circuit controls the boost converter based on a voltage detected by an output voltage detection circuit that detects a voltage of the first output capacitor; the control circuit sets the output voltage of the boost converter to a first output voltage level or a second output voltage level in response to a voltage detected by an input voltage detection circuit that detects a voltage in response to the input voltage, and when the first output voltage level is set, operates the current resonant converter in a full-bridge mode operation mode, and when the second output voltage level is set, operates the current resonant converter in a half-bridge mode operation mode; the output voltage detection circuit and the input voltage detection circuit are a common circuit or separate circuits; the first output voltage level or the second output voltage level is set at a predetermined timing after the input voltage is input, and the set operation mode is maintained until the setting of the first output voltage level or the second output voltage level is reset. Power conversion equipment.

[0142] Here, in the power conversion device 1 according to the example of FIG. 1, the boost converter B1, the current resonant converter B2, the control circuit 111, the capacitor 34, the output voltage detection circuit 152, and the input voltage detection circuit 151 are examples of a boost converter, a current resonant converter, a control circuit, a first output capacitor, an output voltage detection circuit, and an input voltage detection circuit, respectively. Moreover, in the power conversion device 1 according to the example of FIG. 1, 380V and 760V are used as an example of the first output voltage level and the second output voltage level. In power conversion device 301 according to the example of FIG. 7, boost converter B11 is an example of a boost converter. In the power conversion device 401 according to the example of FIG. 9A, the current resonant converter B12 is an example of a current resonant converter.

[0143] 10, the boost converter B101, the current resonant converter B102, the control circuit 111a, and the capacitor 652 are examples of a boost converter, a current resonant converter, a control circuit, and a first output capacitor, respectively. In the example of FIG. 10, the control circuit 111a has a function similar to that of the output voltage detection circuit 152 and a function similar to that of the input voltage detection circuit 151. In the power conversion device 801 according to the example of FIG. 11, the current resonant converter B112 is an example of a current resonant converter. In the power conversion device 901 according to the example of FIG. 12, the current resonant converter B212 is an example of a current resonant converter.

[0144] [Configuration example 2] The current resonant converter comprises: a first leg in which a first switching element and a second switching element are connected in series; a second leg in which a third switching element and a fourth switching element are connected in series; a transformer having a primary winding and a secondary winding; A first resonant inductor; A first resonant capacitor; A first rectifier circuit; Equipped with in a primary side circuit of the transformer, the first leg and the second leg are connected in parallel, and both ends of the primary winding are connected to both a connection point between the first switching element and the second switching element and a connection point between the third switching element and the fourth switching element via the first resonant inductor and the first resonant capacitor, In the secondary circuit of the transformer, both ends of the secondary winding are connected to an input terminal of the first rectifier circuit, In the set operation mode, the first switching element, the second switching element, the third switching element, and the fourth switching element are operated at a fixed frequency rather than being controlled to feed back an output from the secondary side circuit. The power conversion device according to [Configuration Example 1].

[0145] Here, in the power conversion devices 1, 301, 401 according to the examples of Figures 1, 7 and 9A, the MOSFETs Q11 to Q14 are an example of the first to fourth switching elements, the inductor 51 is an example of the first resonant inductor, and the capacitor 53 is an example of the first resonant capacitor. In the power conversion devices 1, 301 according to the examples of Figures 1 and 7, the transformer TR1 is an example of a transformer, the primary winding 52 is an example of a primary winding, the secondary windings 71, 72 are an example of a secondary winding, and the rectifier circuit constituted by diodes 91, 92 is an example of a first rectifier circuit. In the power conversion device 401 according to the example of FIG. 9A, the transformer TR11 is an example of a transformer, the primary winding 52 is an example of a primary winding, the secondary winding 411 is an example of a secondary winding, and the rectifier circuit constituted by the diodes 451 to 454 is an example of a first rectifier circuit.

[0146] In power conversion devices 601, 801, 901 according to the examples of Figures 10, 11 and 12, MOSFETs Q111-Q114 are an example of first to fourth switching elements, inductor 671 is an example of a first resonant inductor, and capacitor 673 is an example of a first resonant capacitor. In the power conversion device 601 of the example of Figure 10, the transformer TR101 is an example of a transformer, the primary winding 672 is an example of a primary winding, the secondary windings 711 and 712 are an example of a secondary winding, and the rectifier circuit composed of diodes 731 and 732 is an example of a first rectifier circuit. In the power conversion device 801 of the example of Figure 11, the transformer TR111 is an example of a transformer, the primary winding 672 is an example of a primary winding, the secondary winding 811 is an example of a secondary winding, and the rectifier circuit composed of diodes 851 to 854 is an example of a first rectifier circuit. In the power conversion device 901 of the example of Figure 12, the transformer TR111 is an example of a transformer, the primary winding 672 is an example of a primary winding, the secondary winding 811 is an example of a secondary winding, and the rectifier circuit composed of MOSFETs 911-914 is an example of a first rectifier circuit.

[0147] [Configuration example 3] the first rectifier circuit is a full-bridge rectifier circuit, In the secondary side circuit, an input terminal of the first rectifier circuit and both ends of the secondary winding are connected via a second resonant inductor and a second resonant capacitor. The power conversion device according to [Configuration Example 2].

[0148] Here, in power conversion device 401 according to the example of FIG. 9A, inductor 431 is an example of a second resonant inductor, and capacitor 432 is an example of a second resonant capacitor. In the power conversion devices 801 and 901 according to the examples of FIGS. 11 and 12, the inductor 831 is an example of a first resonant inductor, and the capacitor 832 is an example of a first resonant capacitor.

[0149] [Configuration example 4] a leakage inductance of the transformer is used as the first resonant inductor and the second resonant inductor; The power conversion device according to [Configuration Example 3].

[0150] [Configuration example 5] an inrush current limiting circuit is provided in a path for charging the first output capacitor; the control circuit determines a target boost voltage of the boost converter in response to a voltage detected by the input voltage detection circuit after an inrush current at the time of startup has ceased and the inrush current limitation of the inrush current limiting circuit has been released. The power conversion device according to any one of the configuration examples [Configuration Example 1] to [Configuration Example 4].

[0151] Here, in the power conversion devices 301 and 401 according to the examples of FIG. 7 and FIG. 9A, the inrush current limiting circuit 310 is an example of an inrush current limiting circuit. In the power conversion devices 601, 801, and 901 according to the examples of FIGS. 10, 11, and 12, the three-phase inrush current limiting circuits 630a to 630c are an example of an inrush current limiting circuit.

[0152] [Configuration example 6] The input voltage is a single-phase AC voltage or a three-phase AC voltage, The boost converter is a PFC converter that performs power factor correction control. The power conversion device according to any one of the configuration examples [Configuration Example 1] to [Configuration Example 5].

[0153] Here, in the power conversion devices 1, 301, and 401 according to the examples of FIG. 1, FIG. 7, and FIG. 9A, the input voltage is a single-phase AC voltage. In the power conversion devices 601, 801, and 901 according to the examples of FIGS. 10, 11, and 12, the input voltage is a three-phase AC voltage.

[0154] [Configuration example 7] The first rectifier circuit is a third leg in which the first rectifying element and the second rectifying element are connected in series; a fourth leg in which a third rectifier element and a fourth rectifier element are connected in series; having the third leg and the fourth leg are connected in parallel, and both ends of the secondary winding are connected to a connection point between the first rectifier element and the second rectifier element and a connection point between the third rectifier element and the fourth rectifier element, The first rectifier circuit can operate as a voltage doubler rectifier circuit by shorting one target rectifier element, which is any one of the first rectifier element, the second rectifier element, the third rectifier element, and the fourth rectifier element, with a first switch; The first switch is a semiconductor switch element or a relay. The power conversion device according to [Configuration Example 3] or [Configuration Example 4].

[0155] In the power conversion device 401 according to the example of FIG. 9A, the diodes 451 to 454 are an example of a first to fourth rectifier elements, and the switch 471 is an example of a first switch. In the example of FIG. 9A, diode 454 (fourth switch element) is the target rectifying element to be short-circuited.

[0156] [Configuration example 8] The control circuit includes: When the voltage detected by the input voltage detection circuit is lower than a first specified voltage, the current resonant converter is operated in the operation mode of the full-bridge mode, and the target rectifier element is short-circuited by the first switch to operate the first rectifier element as the voltage doubler rectifier circuit; When the voltage detected by the input voltage detection circuit is higher than the first specified voltage and lower than the second specified voltage, the current resonant converter is controlled in the operation mode of the full-bridge mode, and the target rectifier element is not short-circuited by the first switch, and the first rectifier element is operated as a full-bridge rectifier circuit; When the voltage detected by the input voltage detection circuit is higher than the second specified voltage, the current resonant converter is operated in the operation mode of the half-bridge mode, and the first rectifier circuit is operated as a full-bridge rectifier circuit without shorting the target rectifier element by the first switch. The power conversion device according to [Configuration Example 7].

[0157] In the power conversion device 401 according to the example of FIG. 9A, the specified voltages Vth1 and Vth2 are examples of a first specified voltage and a second specified voltage, respectively. [Explanation of symbols]

[0158] 1, 301, 401, 601, 801, 901... Power conversion device, 11, 611a to 611c... AC power source, 12, 311, 612, 631a to 631c... Resistor, 31... Diode bridge, 32, 51, 431, 651a to 651c, 671, 831... Inductor, 33, 91, 92, 731, 732, 851 to 854... Diode, 34, 53, 93, 432, 472, 652, 673, 733, 832, 833... Capacitor, 52 ...primary winding, 71, 72, 411, 672, 711, 712, 811...secondary winding, 111, 111a...control circuit, 131...boost converter control circuit, 132...voltage detection circuit, 133...operation mode setting circuit, 134...current resonance type converter drive circuit, 151...input voltage detection circuit, 152...output voltage detection circuit, 211...NOT circuit, 212...NOR circuit, 213...OR circuit, 310, 630a to 630c...inrush current limiting circuit, 312...switch switch, 451-454...diodes, 471, 632a-632c...switches, 611...AC power supply section, 911-914, Q1, Q11-Q14, Q101-Q106, Q111-Q114...MOSFETs, 3011, 3021, 3031, 3311, 3312...voltage, 3012, 3022, 3032...drain current, 3013, 3023, 3033, 3111, 3121, 3131...switching loss, 3112, 3122, 3132 ...conduction loss, 3211, 3212, 3221, 3222, 3411-3413, 3431-3433...characteristics, 3511-3512, 3521-3524...signal, 5011...table, A1, A11, A21, A101, A111, A211...power conversion system, B1, B11, B101...boost converter, B2, B12, B102, B112, B212...current resonant converter, TR1, TR11, TR101, TR111...transformer

Claims

1. A boost converter, a current resonant converter connected to a downstream stage of the boost converter, and a control circuit, the boost converter boosts an input voltage to produce an output voltage, and outputs the output voltage while charging a first output capacitor with the output voltage; the control circuit controls the boost converter based on a voltage detected by an output voltage detection circuit that detects a voltage of the first output capacitor; the control circuit sets the output voltage of the boost converter to a first output voltage level or a second output voltage level in response to a voltage detected by an input voltage detection circuit that detects a voltage in response to the input voltage, and when the first output voltage level is set, operates the current resonant converter in a full-bridge mode operation mode, and when the second output voltage level is set, operates the current resonant converter in a half-bridge mode operation mode; the output voltage detection circuit and the input voltage detection circuit are a common circuit or separate circuits; the first output voltage level or the second output voltage level is set at a predetermined timing after the input voltage is input, and the set operation mode is maintained until the setting of the first output voltage level or the second output voltage level is reset. Power conversion equipment.

2. The current resonant converter comprises: a first leg in which a first switching element and a second switching element are connected in series; a second leg in which a third switching element and a fourth switching element are connected in series; a transformer having a primary winding and a secondary winding; A first resonant inductor; A first resonant capacitor; A first rectifier circuit; Equipped with In a primary side circuit of the transformer, the first leg and the second leg are connected in parallel, and both ends of the primary winding are connected to both a connection point between the first switching element and the second switching element and a connection point between the third switching element and the fourth switching element via the first resonant inductor and the first resonant capacitor, In the secondary circuit of the transformer, both ends of the secondary winding are connected to an input terminal of the first rectifier circuit, In the set operation mode, the first switching element, the second switching element, the third switching element, and the fourth switching element are operated at a fixed frequency rather than being controlled to feed back an output from the secondary side circuit. The power conversion device according to claim 1 .

3. the first rectifier circuit is a full-bridge rectifier circuit, In the secondary side circuit, an input terminal of the first rectifier circuit and both ends of the secondary winding are connected via a second resonant inductor and a second resonant capacitor. The power conversion device according to claim 2 .

4. a leakage inductance of the transformer is used as the first resonant inductor and the second resonant inductor; The power conversion device according to claim 3 .

5. an inrush current limiting circuit is provided in a path for charging the first output capacitor; the control circuit determines a target boost voltage of the boost converter in response to a voltage detected by the input voltage detection circuit after an inrush current at the time of startup has ceased and the inrush current limitation of the inrush current limiting circuit has been released. The power conversion device according to any one of claims 1 to 4.

6. The input voltage is a single-phase AC voltage or a three-phase AC voltage, The boost converter is a PFC converter that performs power factor correction control. The power conversion device according to any one of claims 1 to 4.

7. The first rectifier circuit is a third leg in which the first rectifying element and the second rectifying element are connected in series; a fourth leg in which a third rectifying element and a fourth rectifying element are connected in series; having the third leg and the fourth leg are connected in parallel, and both ends of the secondary winding are connected to a connection point between the first rectifier element and the second rectifier element and a connection point between the third rectifier element and the fourth rectifier element, The first rectifier circuit can operate as a voltage doubler rectifier circuit by shorting one target rectifier element, which is any one of the first rectifier element, the second rectifier element, the third rectifier element, and the fourth rectifier element, with a first switch; The first switch is a semiconductor switch element or a relay. The power conversion device according to claim 3 or 4.

8. The control circuit includes: When the voltage detected by the input voltage detection circuit is lower than a first specified voltage, the current resonant converter is operated in the operation mode of the full-bridge mode, and the target rectifier element is short-circuited by the first switch to operate the first rectifier element as the voltage doubler rectifier circuit; When the voltage detected by the input voltage detection circuit is higher than the first specified voltage and lower than the second specified voltage, the current resonant converter is controlled in the operation mode of the full-bridge mode, and the target rectifier element is not short-circuited by the first switch, and the first rectifier element is operated as a full-bridge rectifier circuit; When the voltage detected by the input voltage detection circuit is higher than the second specified voltage, the current resonant converter is operated in the operation mode of the half-bridge mode, and the first rectifier circuit is operated as a full-bridge rectifier circuit without shorting the target rectifier element by the first switch. The power converter according to claim 7.

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