Converter device

Abstract

The present disclosure addresses the problem of providing a converter device capable of achieving high efficiency. A converter device (100) comprises a first rectifier (2), a half-bridge inverter (3), an input inductor (Li), a transformer (Tr1), a second rectifier (4), an output inductor (Lo1), and a control device (5). The input inductor (Li) is connected between an AC power supply (8) and the first rectifier (2) or the half-bridge inverter (3). A primary winding (N1) of the transformer (Tr1) is connected between a first output end (34) and a second output end (35) of the half-bridge inverter (3). The second rectifier (4) is connected to a secondary winding (N2) of the transformer (Tr1). The output inductor (Lo1) is connected between the secondary winding (N2) and an output capacitor (Co). The control device (5) controls at least the half-bridge inverter (3).

Description

Converter Device

[0001] The present disclosure relates to a converter device.

[0002] Patent Document 1 discloses a power conversion device (converter device) that converts input power from an AC power source into desired DC power.

[0003] The power conversion device disclosed in Patent Document 1 includes a transformer, a series resonant reactor and a series resonant capacitor connected in series to a primary winding of the transformer, and a parallel resonant reactor connected in parallel to the primary winding of the transformer.

[0004] In an isolated converter device equipped with a transformer, further improvement in efficiency is desired.

[0005] Patent No. 6388745

[0006] An object of the present disclosure is to provide a converter device that can achieve high efficiency.

[0007] A converter device according to one aspect of the present disclosure includes a first rectifier, a half-bridge inverter, an input inductor, a transformer, a second rectifier, an output inductor, and a control device. The first rectifier has a first diode and a second diode connected in series, and a first AC output terminal of an AC power supply is connected to a connection point between the first diode and the second diode. The half-bridge inverter has a first series circuit of a first switching element and a second switching element, and a second series circuit of a first capacitor and a second capacitor. The second series circuit is connected in parallel to the first series circuit. In the half-bridge inverter, the first switching element is connected to the cathode of the first diode. In the half-bridge inverter, the second switching element is connected to the anode of the second diode. In the half-bridge inverter, the second AC output terminal of the AC power supply is connected to the connection point between the first switching element and the second switching element. The input inductor is connected between the AC power supply and the first rectifier or the half-bridge inverter. The transformer includes a primary winding and a secondary winding. The first winding of the transformer is connected between a first output terminal between the first switching element and the second switching element and a second output terminal between the first capacitor and the second capacitor. The second rectifier is connected to the secondary winding of the transformer and outputs an output voltage obtained by rectifying a secondary voltage generated in the secondary winding to an output capacitor. The output inductor is connected between the secondary winding and the output capacitor. The control device controls at least the half-bridge inverter.

[0008] FIG. 1 is a circuit diagram showing a converter device of a first embodiment. FIG. 2 is a timing chart for explaining the operation of the converter device of the same. FIG. 3 is an explanatory diagram of the operation of the converter device of the same when the polarity of the input voltage is positive. FIGS. 4A to 4C are explanatory diagrams of the operation of the converter device of the same when the polarity of the input voltage is positive. FIG. 5 is an operational waveform diagram of the converter device of the same. FIG. 6 is an explanatory diagram of the operation of the converter device of the same when the polarity of the input voltage is negative. FIGS. 7A to 7C are explanatory diagrams of the operation of the converter device of the same when the polarity of the input voltage is negative. FIG. 8 is a block diagram showing a control device provided in the converter device of the same. FIG. 9 is a circuit diagram showing a converter device of a second embodiment.

[0009] The following embodiments generally relate to a converter device, and more particularly to an isolated converter device including a transformer.

[0010] The following embodiment is merely an example of an embodiment of the present disclosure. The present disclosure is not limited to the following embodiment, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0011] (Embodiment 1) (1) Overview of Converter Device A converter device 100 of this embodiment is an isolated AC-DC converter having the configuration shown in FIG. 1 and converting AC power into DC power.

[0012] The converter device 100 includes a first rectifier 2, a half-bridge inverter 3, an input inductor Li, a transformer Tr1, a second rectifier 4, an output inductor Lo1, and a control device 5.

[0013] The first rectifier 2 has a first diode D1 and a second diode D2 connected in series with each other, and a first AC output terminal 81 of the AC power supply 8 is connected to a connection point 21 between the first diode D1 and the second diode D2.

[0014] The half-bridge inverter 3 has a first series circuit 31 consisting of a first switching element Q1 and a second switching element Q2, and a second series circuit 32 consisting of a first capacitor C1 and a second capacitor C2. The second series circuit 32 is connected in parallel to the first series circuit 31. The first switching element Q1 is connected to the cathode of a first diode D1, and the second switching element Q2 is connected to the anode of a second diode D2. A second AC output terminal 82 of the AC power supply 8 is connected to a connection point 33 between the first switching element Q1 and the second switching element Q2.

[0015] The input inductor Li is connected between the AC power supply 8 and the first rectifier 2 or the half-bridge inverter 3 .

[0016] The transformer Tr1 includes a primary winding N1 and a secondary winding N2. The primary winding N1 is connected between a first output terminal 34 between the first switching element Q1 and the second switching element Q2 and a second output terminal 35 between the first capacitor C1 and the second capacitor C2.

[0017] The second rectifier 4 is connected to the secondary winding N2 of the transformer Tr1, and outputs an output voltage Vo obtained by rectifying a secondary voltage V2 generated in the secondary winding N2 to the output capacitor Co.

[0018] The output inductor Lo1 is connected between the secondary winding N2 and the output capacitor Co.

[0019] The control device 5 controls at least the half-bridge inverter 3 .

[0020] The converter device 100 can achieve high efficiency.

[0021] For example, the second rectifier 4 outputs an output current Io (see FIG. 1 ) via an output inductor Lo1. In the converter device 100, the output current Io is smoothed by the output inductor Lo1, and the ripple component contained in the output current Io is suppressed, thereby suppressing loss in the output capacitor Co due to the output current Io.

[0022] (2) Details As shown in FIG. 1 , the converter device 100 includes an input filter 1, a first rectifier 2, a half-bridge inverter 3, a second rectifier 4, a control device 5, a pair of input terminals 11 and 12, a pair of output terminals 13 and 14, an input inductor Li, a transformer Tr1, an output inductor Lo1, and an output capacitor Co.

[0023] (2.1) Input Terminal and Output Terminal The input terminals 11 and 12 are connected to an AC power supply 8. The AC power supply 8 is, for example, a 100 V or 200 V commercial power supply, has a first AC output terminal 81 and a second AC output terminal 82, and generates an AC input voltage Vi between the first AC output terminal 81 and the second AC output terminal 82. The input terminal 11 is connected to the first AC output terminal 81, and the input terminal 12 is connected to the second AC output terminal 82. That is, the AC input voltage Vi is applied between the input terminals 11 and 12.

[0024] The converter device 100 converts an AC input voltage Vi into a DC output voltage Vo and outputs the DC output voltage Vo from output terminals 13 and 14. That is, the DC output voltage Vo is applied between the output terminals 13 and 14.

[0025] The AC power supply 8 may be a power supply that utilizes renewable energy such as solar power, wind power, geothermal power, water, biomass, etc. The AC power supply 8 may also be a power supply that generates AC power from charging power of a storage battery.

[0026] (2.2) Input Filter The input filter 1 is a filter circuit having at least one of an inductor and a capacitor. The input filter 1 includes, for example, any of a low-pass filter, a high-pass filter, a band-pass filter, and a band-stop filter.

[0027] A pair of input ends of the input filter 1 are connected to input terminals 11 and 12, respectively. One of a pair of output ends of the input filter 1 is connected to a connection point 21 (described later) of the first rectifier 2. The other of the pair of output ends of the input filter 1 is connected to a connection point 33 (described later) of the half-bridge inverter 3 via an input inductor Li.

[0028] AC power input from an AC power source 8 to input terminals 11 and 12 is supplied via an input filter 1 to a first rectifier 2 and a half-bridge inverter 3 in the subsequent stage.

[0029] (2.3) First Rectifier The first rectifier 2 includes a first diode D1 and a second diode D2. The cathode of the second diode D2 is connected to the anode of the first diode D1, and the first diode D1 and the second diode D2 are connected in series. The connection point between the anode of the first diode D1 and the cathode of the second diode D2 forms a connection point 21. In the first rectifier 2, the first AC output terminal 81 of the AC power supply 8 is connected to the connection point 21 via the input terminal 11 and the input filter 1.

[0030] (2.4) Input Inductor The input inductor Li is connected between the second AC output terminal 82 of the AC power supply 8 and a connection point 33 (described later) of the half-bridge inverter 3. More specifically, the input inductor Li has a first end and a second end. The first end of the input inductor Li is connected to the second AC output terminal 82 of the AC power supply 8 via the input filter 1 and the input terminal 12. The second end of the input inductor Li is connected to the connection point 33 of the half-bridge inverter 3.

[0031] (2.5) Half-Bridge Inverter The half-bridge inverter 3 has a first series circuit 31 including a first switching element Q1 and a second switching element Q2, and a second series circuit 32 including a first capacitor C1 and a second capacitor C2. The second series circuit 32 is connected in parallel to the first series circuit 31. In the half-bridge inverter 3, the first switching element Q1 is connected to the cathode of a first diode D1, and the second switching element Q2 is connected to the anode of a second diode D2.

[0032] In the half-bridge inverter 3, the connection point between the first switching element Q1 and the second switching element Q2 constitutes a connection point 33. The connection point 33 is connected to a second AC output end 82 of the AC power supply 8 via an input inductor Li, an input filter 1, and an input terminal 12.

[0033] In the half-bridge inverter 3, the first switching element Q1 and the second switching element Q2 are each semiconductor switching elements having a control terminal, a first main terminal, and a second main terminal. The control terminals of the first switching element Q1 and the second switching element Q2 are connected to the control device 5. The first switching element Q1 is turned on and off in response to a first switching signal S1 provided by the control device 5. The second switching element Q2 is turned on and off in response to a second switching signal S2 provided by the control device 5. The first switching element Q1 and the second switching element Q2 are, for example, GaN-based GITs (Gate Injection Transistors). The control terminal, the first main terminal, and the second main terminal of the first switching element Q1 and the second switching element Q2 are, respectively, a gate terminal, a drain terminal, and a source terminal.

[0034] The drain terminal of the first switching element Q1 is connected to the cathode of the first diode D1, the source terminal of the first switching element Q1 is connected to the drain terminal of the second switching element Q2, and the source terminal of the second switching element Q2 is connected to the anode of the second diode D2.

[0035] A first end of the first capacitor C1 is connected to the drain terminal of the first switching element Q1 and the cathode of the first diode D1. A second end of the first capacitor C1 is connected to the first end of the second capacitor C2. A second end of the second capacitor C2 is connected to the source terminal of the second switching element Q2 and the anode of the second diode D2.

[0036] (2.6) Transformer The transformer Tr1 includes a primary winding N1 and a secondary winding N2. The primary winding N1 is connected between a first output terminal 34 of the half-bridge inverter 3, which is located between the first switching element Q1 and the second switching element Q2, and a second output terminal 35 of the half-bridge inverter 3, which is located between the first capacitor and the second capacitor.

[0037] The secondary winding N2 is connected to the second rectifier 4 .

[0038] Then, in the half-bridge inverter 3, when the first switching element Q1 and the second switching element Q2 are turned on and off, the primary voltage V1 generated in the primary winding N1 becomes an alternating voltage, and the secondary voltage V2 generated in the secondary winding N2 becomes an alternating voltage.

[0039] (2.7) Second Rectifier The second rectifier 4 of this embodiment is configured by a full-bridge inverter 40 .

[0040] The full-bridge inverter 40 is connected to the secondary winding N2 of the transformer Tr1. The full-bridge inverter 40 has a third switching element Q3, a fourth switching element Q4, a fifth switching element Q5, and a sixth switching element Q6. The full-bridge inverter 40 generates a DC output voltage Vo by full-wave rectifying a secondary voltage V2 generated in the secondary winding N2 by turning on and off the third to sixth switching elements Q3 to Q6, respectively.

[0041] More specifically, the full-bridge inverter 40 includes a series circuit 41 including a third switching element Q3 and a fourth switching element Q4, and a series circuit 42 including a fifth switching element Q5 and a sixth switching element Q6. The series circuit 41 is connected between the output terminals 13 and 14 via an output inductor Lo1. The series circuit 42 is connected between the output terminals 13 and 14 via the output inductor Lo1.

[0042] The full-bridge inverter 40 also includes a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6. The third diode D3 is connected in anti-parallel to the third switching element Q3. The fourth diode D4 is connected in anti-parallel to the fourth switching element Q4. The fifth diode D5 is connected in anti-parallel to the fifth switching element Q5. The sixth diode D6 is connected in anti-parallel to the sixth switching element Q6.

[0043] In the full-bridge inverter 40, the third to sixth switching elements Q3 to Q6 are each semiconductor switching elements having a control terminal, a first main terminal, and a second main terminal. The control terminals of the third to sixth switching elements Q3 to Q6 are connected to the control device 5. The third to sixth switching elements Q3 to Q6 are respectively turned on and off in response to third to sixth switching signals S3 to S6 provided by the control device 5. The third to sixth switching elements Q3 to Q6 are, for example, metal-oxide-semiconductor field effect transistors (MOSFETs). More specifically, each of the third to sixth switching elements Q3 to Q6 is an n-channel MOSFET. Here, the n-channel MOSFET is a normally-off Si-based MOSFET. In the third to sixth switching elements Q3 to Q6, the control terminal, the first main terminal, and the second main terminal are, respectively, the gate terminal, the drain terminal, and the source terminal.

[0044] The drain terminal of the third switching element Q3 is connected to the output terminal 13 via the output inductor Lo1. The source terminal of the third switching element Q3 is connected to the drain terminal of the fourth switching element Q4. The source terminal of the fourth switching element Q4 is connected to the output terminal 14.

[0045] The drain terminal of the fifth switching element Q5 is connected to the output terminal 13 via the output inductor Lo1. The source terminal of the fifth switching element Q5 is connected to the drain terminal of the sixth switching element Q6. The source terminal of the sixth switching element Q6 is connected to the output terminal 14.

[0046] The third to sixth diodes D3 to D6 are parasitic diodes of the MOSFETs of the third to sixth switching elements Q3 to Q6, respectively. Each of the third to sixth diodes D3 to D6 has an anode and a cathode. The anode and cathode of each of the third to sixth diodes D3 to D6 are connected to the second main terminal (source terminal) and the first main terminal (drain terminal) of the corresponding one of the third to sixth switching elements Q3 to Q6, respectively.

[0047] The full-bridge inverter 40 has a first input terminal 44 between the third switching element Q3 and the fourth switching element Q4, and a second input terminal 45 between the fifth switching element Q5 and the sixth switching element Q6. Specifically, the first input terminal 44 is a connection point between the source of the third switching element Q3 and the drain of the fourth switching element Q4. The second input terminal 45 is a connection point between the source of the fifth switching element Q5 and the drain of the sixth switching element Q6. A secondary winding N2 of a transformer Tr1 is connected between the first input terminal 44 and the second input terminal 45.

[0048] The full-bridge inverter 40 has a first DC output terminal 46 and a second DC output terminal 47. The drains of the third switching element Q3 and the fifth switching element Q5 are connected to the first DC output terminal 46, and the output terminal 13 is also connected via an output inductor Lo1. The sources of the fourth switching element Q4 and the sixth switching element Q6 are connected to the second DC output terminal 47, and the output terminal 14 is also connected.

[0049] The above-described full-bridge inverter 40 full-wave rectifies the secondary voltage V2 generated in the secondary winding N2 by turning on and off the third to sixth switching elements Q3 to Q6, respectively. The full-bridge inverter 40 outputs the DC voltage obtained by full-wave rectifying the secondary voltage V2 as an output voltage Vo from the first DC output terminal 46 and the second DC output terminal 47. The current output from the first DC output terminal 46 by the full-bridge inverter 40 is referred to as an output current Io.

[0050] (2.8) Output Inductor The output inductor Lo1 is connected between the output capacitor Co and one of the pair of DC output terminals, i.e., the first DC output terminal 46 and the second DC output terminal 47, of the second rectifier 4. In FIG. 1 , the output inductor Lo1 is connected between the first DC output terminal 46 and the output terminal 13 of the full-bridge inverter 40. That is, a first terminal of the output inductor Lo1 is connected to the first DC output terminal 46, and a second terminal of the output inductor Lo1 is connected to the output terminal 13.

[0051] The output inductor Lo1 smoothes the output current Io output from the full-bridge inverter 40 .

[0052] (2.9) Output Capacitor The output capacitor Co is connected between the output terminals 13 and 14.

[0053] Specifically, a first end of the output capacitor Co is connected to the output terminal 13 and is also connected to a first DC output terminal 46 of the full-bridge inverter 40 via an output inductor Lo1. A second end of the output capacitor Co is connected to the output terminal 14 and is also connected to a second DC output terminal 47 of the full-bridge inverter 40. The output capacitor Co smoothes the output voltage Vo output from the first DC output terminal 46 and the second DC output terminal 47. The output voltage Vo is output from the output terminals 13 and 14.

[0054] (2.10) Control Device The control device 5 controls the half-bridge inverter 3 and the full-bridge inverter 40. The control device 5 controls the first switching element Q1 and the second switching element Q2 of the half-bridge inverter 3. The control device 5 also controls the third switching element Q3, the fourth switching element Q4, the fifth switching element Q5, and the sixth switching element Q6 of the full-bridge inverter 40. The control device 5 is configured to provide first to sixth switching signals (control signals) S1 to S6 to the first to sixth switching elements Q1 to Q6, respectively. The first to sixth switching signals S1 to S6 are gate voltages (gate signals) applied between the control terminals and the second main terminals of the first to sixth switching elements Q1 to Q6, respectively, to turn on and off the first to sixth switching elements Q1 to Q6. The first to sixth switching signals S1 to S6 are voltages whose voltage levels change between a voltage level (hereinafter also referred to as a high level) higher than the threshold voltages (gate threshold voltages) of the first to sixth switching elements Q1 to Q6 and a voltage level (hereinafter also referred to as a low level) lower than the threshold voltages. The control device 5 is configured to be able to change the frequencies of the first to sixth switching signals S1 to S6. In other words, the control device 5 can control the output voltage Vo by controlling the half-bridge inverter 3 and the full-bridge inverter 40.

[0055] 2 is a time chart when the control device 5 controls the first to sixth switching elements Q1 to Q6. From the top to bottom, FIG. 2 shows the waveforms of the first switching signal S1, the second switching signal S2, the third switching signal S3, the fourth switching signal S4, the fifth switching signal S5, the sixth switching signal S6, the primary voltage V1, and the secondary voltage V2. The primary voltage V1 is the voltage between the first output terminal 34 and the second output terminal 35 when the potential of the second output terminal 35 is set as the reference potential. The secondary voltage V2 is the voltage between the first input terminal 44 and the second input terminal 45 when the potential of the second input terminal 45 is set as the reference potential.

[0056] The control device 5 alternately switches the first switching signal S1 between high and low levels and alternately switches the second switching signal S2 between high and low levels. At this time, the control device 5 sets the second switching signal S2 to low level when the first switching signal S1 is high level, and sets the second switching signal S2 to high level when the first switching signal S1 is low level. In other words, the control device 5 alternately turns on and off the first and second switching elements Q1 and Q2.

[0057] In this embodiment, the control device 5 equalizes the duty of the first switching signal S1 that controls the first switching element Q1 and the duty of the second switching signal S2 that controls the second switching element Q2. The duty of a switching signal is the ratio of the high-level period to the total time of the high-level period and the low-level period in one cycle of the switching signal. Specifically, the duty of each of the first and second switching signals S1 and S2 is 50%. In this way, by equalizing the duty of the first switching signal S1 and the duty of the second switching signal S2, the control device 5 can simplify the process of generating the first switching signal S1 and the second switching signal S2.

[0058] As described above, the control device 5 controls the first and second switching elements Q1 and Q2, so that a primary voltage V1 is generated across the primary winding N1 (between the first output terminal 34 and the second output terminal 35), and a secondary voltage V2 is generated across the secondary winding N2 (between the first input terminal 44 and the second input terminal 45). Specifically, the primary voltage V1 is an alternating voltage that is positive when the first switching element Q1 is on and negative when the second switching element Q2 is on. The secondary voltage V2 is an alternating voltage that is positive when the first switching element Q1 is on and negative when the second switching element Q2 is on.

[0059] The full-bridge inverter 40, which serves as the second rectifier 4, full-wave rectifies the secondary voltage V2 to generate and output a DC output voltage Vo. The control device 5 turns on the third and sixth switching elements Q3, Q6 and turns off the fourth and fifth switching elements Q4, Q5 during a period when the polarity of the secondary voltage V2 is positive (the potential of the first input terminal 44 is higher than the potential of the second input terminal 45). The control device 5 turns on the fourth and fifth switching elements Q4, Q5 and turns off the third and sixth switching elements Q3, Q6 during a period when the polarity of the secondary voltage V2 is negative (the potential of the second input terminal 45 is higher than the potential of the first input terminal 44). That is, the control device 5 alternately turns on the third and sixth switching elements Q3, Q6 and the fourth and fifth switching elements Q4, Q5 depending on the polarity of the secondary voltage V2.

[0060] Furthermore, the control device 5 equalizes the duty of the third switching signal S3 that controls the third switching element Q3, the duty of the fourth switching signal S4 that controls the fourth switching element Q4, the duty of the fifth switching signal S5 that controls the fifth switching element Q5, and the duty of the sixth switching signal S6 that controls the sixth switching element Q6. The duty of a switching signal is the ratio of the high-level period to the total time of the high-level period and the low-level period in one cycle of the switching signal. Specifically, the duty of each of the third to sixth switching signals S3 to S6 is 50%. By equalizing the duties of the third to sixth switching signals S3 to S6, the control device 5 can simplify the process of generating the third to sixth switching signals S3 to S6.

[0061] In this embodiment, the control device 5 synchronizes the drive timing of the first switching element Q1 and the second switching element Q2 with the drive timing of the third switching element Q3, the fourth switching element Q4, the fifth switching element Q5, and the sixth switching element Q6. By synchronizing the drive timing of the first to sixth switching elements Q1 to Q6, the control device 5 can simplify the process of generating the first to sixth switching signals S1 to S6.

[0062] 2, the first switching signal S1, the third switching signal S3, and the sixth switching signal S6 are in-phase signals that switch to the same voltage level at the same time. That is, the first switching signal S1, the third switching signal S3, and the sixth switching signal S6 switch from low to high and from high to low at the same time. Therefore, the first switching element Q1, the third switching element Q3, and the sixth switching element Q6 turn on and off at the same time.

[0063] The second switching signal S2, the fourth switching signal S4, and the fifth switching signal S5 are in-phase signals that switch to the same voltage level at the same time. That is, the second switching signal S2, the fourth switching signal S4, and the fifth switching signal S5 switch from low to high and from high to low at the same time. Therefore, the second switching element Q2, the fourth switching element Q4, and the fifth switching element Q5 turn on and off at the same time.

[0064] Furthermore, when the control device 5 alternately turns on and off the two series-connected switching elements, it is preferable to provide a dead time Td. The dead time Td is a period during which both of the series-connected switching elements are maintained in an off state. During the dead time Td, both of the two switching signals for driving the two series-connected switching elements are maintained at a low level.

[0065] Specifically, the dead time Td is provided when the voltage levels of the first switching signal S1 and the second switching signal S2 are inverted. The dead time Td is also provided when the voltage levels of the third switching signal S3 and the fourth switching signal S4 are inverted. The dead time Td is also provided when the voltage levels of the fifth switching signal S5 and the sixth switching signal S6 are inverted. That is, during the dead time Td, the first to sixth switching signals S1 to S6 are maintained at a low level, and the first to sixth switching elements Q1 to Q6 are maintained in an off state.

[0066] Furthermore, the control device 5 controls the first switching element Q1 and the second switching element Q2 so that the mode of the current (inductor current IL1) flowing through the input inductor Li is a discontinuous current mode.

[0067] FIG. 3 illustrates the relationship between the first switching signal S1 and the second switching signal S2, the inductor current IL1, and the primary voltage V1 when the polarity of the input voltage Vi is positive (the potential of the input terminal 11 is higher than the potential of the input terminal 12).

[0068] When the polarity of the input voltage Vi is positive, the control device 5 generates the first switching signal S1 and the second switching signal S2 so as to transition as shown in FIG. 3 , in the order of first period T1-dead time Td-second period T2-third period T3-dead time Td-first period T1-... The first period T1 is a period during which the first switching signal S1 is at a high level and the second switching signal S2 is at a low level. The second period T2 and the third period T3 are periods during which the first switching signal S1 is at a low level and the second switching signal S2 is at a high level. The dead time Td is a period during which the first switching signal S1 and the second switching signal S2 are at a low level. The switching period Tsw of the half-bridge inverter 3 is composed of the dead time Td-first period T1-dead time Td-second period T2-third period T3.

[0069] 4A, 4B, and 4C are diagrams illustrating the operation of the first period T1, the second period T2, and the third period T3 of FIG. 3, respectively. In FIGS. 4A and 4B, the current path of the inductor current IL1 (see FIG. 5) is indicated by a thin dashed line. During the first period T1, as shown in FIG. 4A, energy is stored in the input inductor Li by the inductor current IL1. During the second period T2, as shown in FIG. 4B, energy is released from the input inductor Li. During the third period T3, the inductor current IL1 becomes zero, so the inductor current IL1 is not shown in FIG. 4C. Furthermore, in FIGS. 4A, 4B, and 4C, the primary current I1 flowing through the primary winding N1 of the transformer Tr1 is indicated by a thick dashed line.

[0070] Specifically, during the first period T1 in Fig. 3, the first switching element Q1 is on and the second switching element Q2 is off, so that an inductor current IL1 flows through the path of the first diode D1, the first switching element Q1, and the input inductor Li, as shown in Fig. 4A. During the first period T1, the inductor current IL1 increases with the passage of time from the start of the first period T1, and energy is stored in the input inductor Li. Also, during the first period T1 in Fig. 3, as shown in Fig. 4A, a primary current I1 flows through the path of the first capacitor C1, the first switching element Q1, the primary winding N1, and the first capacitor C1.

[0071] When the dead time Td has elapsed since the end of the first period T1, the voltage across the second switching element Q2 has dropped to zero volts. As a result, the second switching element Q2 is switched to zero volts at the start of the second period T2.

[0072] During the second period T2 in Fig. 3, the first switching element Q1 is off and the second switching element Q2 is on, so as shown in Fig. 4B, an inductor current IL1 flows through the path of the first diode D1-first capacitor C1-second capacitor C2-second switching element Q2-input inductor Li. At this time, the stored energy in the input inductor Li is released from the input inductor Li, and the inductor current IL1 decreases to zero as time passes from the start of the second period T2. Also, during the second period T2, a primary current I1 flows through the path of the second capacitor C2-primary winding N1-second switching element Q2-second capacitor C2.

[0073] The third period T3 in Figure 3 is a zero-current period in which no current flows through the input inductor Li. That is, the control device 5 controls the first switching element Q1 and the second switching element Q2 so that the third period T3 in which the inductor current IL1 is zero is included, thereby setting the mode of the inductor current IL1 to a discontinuous current mode. Furthermore, during the third period T3, the primary current I1 flows through the path of the second capacitor C2-primary winding N1-second switching element Q2-second capacitor C2. Note that during the third period T3, resonance occurs due to stray capacitance.

[0074] FIG. 6 illustrates the relationship between the first switching signal S1, the second switching signal S2, the inductor current IL1, and the primary voltage V1 when the polarity of the input voltage Vi is negative (the potential of the input terminal 12 is higher than the potential of the input terminal 11).

[0075] When the polarity of the input voltage Vi is negative, the control device 5 generates the first switching signal S1 and the second switching signal S2 so as to transition as shown in FIG. 6 : fourth period T11 - dead time Td - fifth period T12 - sixth period T13 - dead time Td - fourth period T11 - .... The fourth period T11 is a period during which the first switching signal S1 is at a low level and the second switching signal S2 is at a high level. The fifth period T12 and sixth period T13 are periods during which the first switching signal S1 is at a high level and the second switching signal S2 is at a low level. The dead time Td is a period during which the first switching signal S1 and the second switching signal S2 are at a low level. The switching period Tsw of the half-bridge inverter 3 is composed of the dead time Td - fourth period T11 - dead time Td - fifth period T12 - sixth period T13.

[0076] 7A, 7B, and 7C are diagrams illustrating the operation of the fourth period T11, the fifth period T12, and the sixth period T13, respectively, of FIG. 6. In FIGS. 7A and 7B, the current path of the inductor current IL1 is indicated by a thin dashed line. During the fourth period T11, as shown in FIG. 7A, energy is stored in the input inductor Li by the inductor current IL1. During the fifth period T12, as shown in FIG. 7B, energy is released from the input inductor Li. During the sixth period T13, the inductor current IL1 becomes zero, so the inductor current IL1 is not shown in FIG. 7C. Furthermore, in FIGS. 7A, 7B, and 7C, the primary current I1 flowing through the primary winding N1 of the transformer Tr1 is indicated by a thick dashed line.

[0077] Specifically, during the fourth period T11 in Fig. 6, the first switching element Q1 is off and the second switching element Q2 is on, so that an inductor current IL1 flows through the path of the input inductor Li, the second switching element Q2, and the second diode D2, as shown in Fig. 7A. During the fourth period T11, the inductor current IL1 (its absolute value) increases with the passage of time from the start of the fourth period T11, and energy is stored in the input inductor Li. Also, during the fourth period T11, as shown in Fig. 7A, a primary current I1 flows through the path of the second capacitor C2, the primary winding N1, the second switching element Q2, and the second capacitor C2.

[0078] When the dead time Td has elapsed since the end of the fourth period T11, the voltage across the first switching element Q1 has dropped to zero volts. As a result, the first switching element Q1 is switched to zero volts at the start of the fifth period T12.

[0079] During the fifth period T12 in Fig. 6, the first switching element Q1 is on and the second switching element Q2 is off, so as shown in Fig. 7B, an inductor current IL1 flows through the path of the input inductor Li, first switching element Q1, first capacitor C1, second capacitor C2, and second diode D2. At this time, the stored energy in the input inductor Li is released from the input inductor Li, and the inductor current IL1 (its absolute value) decreases to zero as time passes from the start of the fifth period T12. Also, during the fifth period T12, a primary current I1 flows through the path of the first capacitor C1, first switching element Q1, primary winding N1, and first capacitor C1.

[0080] The sixth period T13 in Figure 6 is a zero-current period in which no current flows through the input inductor Li. That is, the control device 5 controls the first switching element Q1 and the second switching element Q2 so that the sixth period T13, in which the inductor current IL1 is zero, is included, thereby setting the mode of the inductor current IL1 to a discontinuous current mode. Furthermore, during the sixth period T13, the primary current I1 flows through the path of the first capacitor C1-first switching element Q1-primary winding N1-first capacitor C1. Note that during the sixth period T13, resonance occurs due to stray capacitance.

[0081] As described above, the control device 5 controls the first switching element Q1 and the second switching element Q2 so as to enter a discontinuous current mode that includes a period during which the inductor current IL1 is zero. Note that Fig. 5 also shows the waveform of the input current Ii (see Fig. 1) that flows from the AC power supply 8 to the converter device 100.

[0082] In the converter device 100, when the peak value of the inductor current IL1 flowing through the input inductor Li is ILmax, ILmax is expressed by the following equation 1. Here, [Li] is the inductance of the input inductor Li. Ton is the on-time in the switching cycle Tsw of the half-bridge inverter 3, and is the respective lengths of the first period T1 and the fourth period T11. In this embodiment, the duties of the first switching signal S1 and the second switching signal S2 are equal to each other, so the respective lengths of the first period T1 and the fourth period T11 are the same on-time Ton.

[0083]

[0084] Therefore, if the on-time Ton and the inductance [Li] of the input inductor Li are constant, the peak value ILmax of the inductor current IL1 changes in proportion to the instantaneous value of the input voltage Vi, making it possible to improve the power factor.

[0085] The control device 5 also controls the DC bus voltage Vdc of the half-bridge inverter 3 and controls the output voltage Vo of the full-bridge inverter 40. The DC bus voltage Vdc is the voltage across the second series circuit 32 of the first capacitor C1 and the second capacitor C2.

[0086] The DC bus voltage Vdc is expressed by the following equation 2. Note that Vmax is the maximum value (peak value) of the input voltage Vi. Po is the output power of the converter device 100. Tsw is the switching period of the half-bridge inverter 3 (see FIGS. 3 and 6). Ton is the on-time in the switching period Tsw of the half-bridge inverter 3, and is the duration of each of the first period T1 and the fourth period T11. [Li] is the inductance of the input inductor Li.

[0087]

[0088] In the converter device 100, the control device 5 makes the duties of the first switching signal S1 and the second switching signal S2 equal to each other, so that if the output power Po is constant, the DC bus voltage Vdc can be kept constant.

[0089] The control device 5 can control the output voltage Vo by controlling the DC bus voltage Vdc.

[0090] In addition, in the converter device 100, the control device 5 controls the switching frequencies of the first to sixth switching elements Q1 to Q6, thereby controlling the DC bus voltage Vdc of the half-bridge inverter 3 and the output voltage Vo of the full-bridge inverter 40.

[0091] For example, the control device 5 controls the switching frequencies of the first switching element Q1 and the second switching element Q2 by PI control based on the command value Vdc* of the DC bus voltage Vdc of the half-bridge inverter 3 and the detected value [Vdc] of the DC bus voltage Vdc, or by PI control based on the command value Vo* of the output voltage Vo of the full-bridge inverter 40 and the detected value [Vo] of the output voltage Vo. Then, the control device 5 sets the switching frequencies of the third switching element Q3, the fourth switching element Q4, the fifth switching element Q5, and the sixth switching element Q6 to be the same as the switching frequencies of the first switching element Q1 and the second switching element Q2. That is, in the converter device 100, the control device 5 controls the DC bus voltage Vdc and the output voltage Vo by PFM (Pulse Frequency Modulation) control of the first to sixth switching elements Q1 to Q6. The control device 5 acquires the detected value [Vdc] of the DC bus voltage Vdc and the detected value [Vo] of the output voltage Vo from the detector for the DC bus voltage Vdc and the detector for the output voltage Vo, respectively. The detectors for the DC bus voltage Vdc and the output voltage Vo may be provided in the converter device 100 or may be provided outside the converter device 100.

[0092] Specifically, as shown in FIG. 8, the control device 5 includes a subtraction unit 51, a PI control unit 52, and a generation unit 53.

[0093] First, the PI control based on the command value Vdc* of the DC bus voltage Vdc and the detected value [Vdc] of the DC bus voltage Vdc will be described.

[0094] A subtraction unit 51 calculates the difference between the command value Vdc* and the detected value [Vdc]. A PI control unit 52 generates a switching frequency command value fsw* for feedback control to bring the difference calculated by the subtraction unit 51 closer to zero. A generation unit 53 generates first and second switching signals S1 and S2, which are rectangular wave signals having a frequency based on the switching frequency command value fsw*, to control the switching frequencies of the first and second switching elements Q1 and Q2. Furthermore, the generation unit 53 generates third to sixth switching signals S3 to S6, which are rectangular wave signals having the same frequency as the first and second switching signals S1 to S2. Thus, the switching frequencies of the third to sixth switching elements Q3 to Q6 are controlled to the same frequency as the switching frequencies of the first and second switching elements Q1 to Q2.

[0095] As described above, the converter device 100 controls the DC bus voltage Vdc by PFM controlling the first and second switching elements Q1 and Q2. As a result, the converter device 100 can suppress fluctuations in the DC bus voltage Vdc when the load fluctuates.

[0096] Furthermore, when performing PI control based on a command value Vo* of the output voltage Vo and a detected value [Vo] of the output voltage Vo, a subtraction unit 51 calculates the difference between the command value Vo* and the detected value [Vo]. A PI control unit 52 generates a switching frequency command value fsw* for feedback control that brings the difference calculated by the subtraction unit 51 closer to zero. A generation unit 53 generates first to sixth switching signals S1 to S6 in the same manner as described above. In this case, the converter device 100 controls the output voltage Vo by PFM-controlling the first to sixth switching elements Q1 to Q6. As a result, the converter device 100 can suppress fluctuations in the output voltage Vo during load fluctuations.

[0097] Furthermore, the command value Vdc* for the DC bus voltage Vdc and the command value Vo* for the output voltage Vo are determined in the control device 5 based on an external command from an external device to the control device 5. In other words, the control device 5 has a function of generating the command value Vdc* or the command value Vo* based on an external command from the external device. The communication protocol used for communication between the external device and the control device 5 may be, for example, MODBUS, CAN, or another serial communication protocol. The external device may be, for example, an external controller. Note that it is not essential to use a specific communication protocol for communication of an external command from the external device to the control device 5.

[0098] Further, the control device 5 may be configured to hold data of the command value Vdc* in advance.

[0099] As described above, in the converter device 100, the control device 5 performs PFM control, in which the control device 5 controls the switching frequencies of the first to sixth switching elements Q1 to Q6 by PI control. As a result, the converter device 100 can bring the DC bus voltage Vdc or the output voltage Vo closer to the command value even if the output power Po of the converter device 100 fluctuates due to load fluctuations or the like.

[0100] The control device 5 preferably includes a computer system. The computer system executes a program to realize some or all of the functions of the control device 5. The computer system's main hardware configuration is a processor that operates according to the program. The processor may be of any type, as long as it can realize its functions by executing the program. The processor may be composed of one or more electronic circuits, including a semiconductor integrated circuit (integrated circuit) or an LSI (large-scale integration). While ICs and LSIs are used here, the names may vary depending on the degree of integration, and may also be called system LSIs, VLSIs (very large-scale integration), or ULSIs (ultra-large-scale integration). Field-programmable gate arrays (FPGAs), which are programmed after the LSI is manufactured, or reconfigurable logic devices that can reconfigure the connections within the LSI or set up circuit partitions within the LSI, can also be used for the same purpose. Multiple electronic circuits may be integrated on a single chip or provided on multiple chips. Multiple chips may be integrated into a single device or provided on multiple devices. The program is recorded on a non-transitory recording medium such as a computer-readable ROM, an optical disk, a hard disk drive, etc. The program may be stored in the recording medium in advance, or may be supplied to the recording medium via a wide area communication network including the Internet.

[0101] The control device 5 may be realized by either a single computer device or a plurality of computers linked to each other. The control device 5 may also be constructed as a cloud computing system.

[0102] (2.11) Summary In the converter device 100 according to the first embodiment described above, the output current Io is smoothed by the output inductor Lo1, and the ripple component contained in the output current Io is suppressed, so that the loss in the output capacitor Co due to the output current Io can be suppressed.

[0103] As a comparative example, there is an AC-DC converter in which an inductor is connected in series to the primary winding N1 of the transformer Tr1. In this comparative example, an AC current flows through the inductor connected in series to the primary winding N1, which generates iron loss. However, the converter device 100 does not have an inductor connected in series to the primary winding N1 of the transformer Tr1. Therefore, the converter device 100 can reduce iron loss compared to a configuration that has an inductor connected in series to the primary winding N1 of the transformer Tr1.

[0104] Therefore, the converter device 100 can achieve high efficiency.

[0105] Furthermore, in the converter device 100 according to embodiment 1, the control device 5 makes the duty of the first switching signal S1 and the duty of the second switching signal S2 equal to each other, thereby simplifying the process of generating the first switching signal S1 and the second switching signal S2.

[0106] Furthermore, in the converter device 100 according to the first embodiment, the control device 5 makes the duties of the third to sixth switching signals S3 to S6 equal to each other, thereby simplifying the process of generating the third to sixth switching signals S3 to S6.

[0107] Furthermore, in the converter device 100 according to the first embodiment, the control device 5 synchronizes the drive timings of the first to sixth switching elements Q1 to Q6, thereby simplifying the process of generating the first to sixth switching signals S1 to S6.

[0108] Furthermore, in the converter device 100 according to the first embodiment, the control device 5 controls the first switching element Q1 and the second switching element Q2 so that the mode of the current flowing through the input inductor Li is a discontinuous current mode, thereby improving the power factor.

[0109] Furthermore, in the converter device 100 according to the first embodiment, the control device 5 controls the switching frequencies of the first and second switching elements Q1 and Q2 by PI control based on the command value Vdc* and the detected value [Vdc] of the DC bus voltage Vdc, or by PI control based on the command value Vo* and the detected value [Vo] of the output voltage Vo, thereby making the switching frequencies of the third to sixth switching elements Q3 to Q6 the same as the switching frequencies of the first and second switching elements Q1 to Q2. As a result, the converter device 100 according to the first embodiment can suppress fluctuations in the DC bus voltage Vdc or the output voltage Vo during load fluctuations.

[0110] (Embodiment 2) A converter device 100A according to embodiment 2 will be described below with reference to Fig. 9. Regarding the converter device 100A according to embodiment 2, components similar to those of the converter device 100 according to embodiment 1 (see Fig. 1) are denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0111] (1) Overview The converter device 100A according to the second embodiment includes a first half-bridge inverter 3A having the same configuration as the half-bridge inverter 3 in the converter device 100 according to the first embodiment. The converter device 100A also includes a second half-bridge inverter 40A as the second rectifier 4, instead of the full-bridge inverter 40 of the converter device 100. The converter device 100A also includes an output inductor Lo2, instead of the output inductor Lo1 of the converter device 100. The converter device 100A also includes a control device 5A, instead of the control device 5 of the converter device 100.

[0112] In the converter device 100A, the second rectifier 4 is a second half-bridge inverter 40A including a third switching element Q3, a fourth switching element Q4, a third capacitor C3, and a fourth capacitor C4. The output inductor Lo2 is connected in series with the secondary winding N2. The control device 5A controls the first half-bridge inverter 3A and the second half-bridge inverter 40A.

[0113] The control device 5A controls the first to fourth switching elements Q1 to Q4, thereby converting the AC input voltage Vi into a DC output voltage Vo. That is, the control device 5A controls the first half-bridge inverter 3A and the second half-bridge inverter 40A, thereby controlling the output voltage Vo.

[0114] (2) Details The first half-bridge inverter 3A has the same configuration as the half-bridge inverter 3 and includes a first switching element Q1, a second switching element Q2, a first capacitor C1, and a second capacitor C2. Control terminals of the first switching element Q1 and the second switching element Q2 are connected to the control device 5A. The first switching element Q1 is turned on and off in response to a first switching signal S1 provided by the control device 5A. The second switching element Q2 is turned on and off in response to a second switching signal S2 provided by the control device 5A.

[0115] The second half-bridge inverter 40A is connected to the secondary winding N2 of the transformer Tr1 via an output inductor Lo2. The second half-bridge inverter 40A includes a third capacitor C3 and a fourth capacitor C4 instead of the fifth switching element Q5 and the sixth switching element Q6 in the converter device 100 according to the first embodiment. The second half-bridge inverter 40A includes a series circuit 41 of the third switching element Q3 and the fourth switching element Q4 and a series circuit 43 of the third capacitor C3 and the fourth capacitor C4. The series circuit 41 of the third switching element Q3 and the fourth switching element Q4 is connected between the output terminal 13 and the output terminal 14. The series circuit 43 of the third capacitor C3 and the fourth capacitor C4 is connected between the output terminal 13 and the output terminal 14. The output capacitor Co is connected between the output terminal 13 and the output terminal 14.

[0116] The second half-bridge inverter 40A also includes a third diode D3 and a fourth diode D4. The third diode D3 is connected in anti-parallel to the third switching element Q3. The fourth diode D4 is connected in anti-parallel to the fourth switching element Q4.

[0117] In the second half-bridge inverter 40A, the third switching element Q3 and the fourth switching element Q4 each have a control terminal, a first main terminal, and a second main terminal. The control terminals of the third switching element Q3 and the fourth switching element Q4 are connected to the control device 5A. The third switching element Q3 is turned on and off in response to a third switching signal S3 provided by the control device 5A. The fourth switching element Q4 is turned on and off in response to the third switching signal S3 provided by the control device 5A.

[0118] The second half-bridge inverter 40A has a first input terminal 44 between the third switching element Q3 and the fourth switching element Q4 and a second input terminal 45a between the third capacitor C3 and the fourth capacitor C4. In the second half-bridge inverter 40A, a series circuit of a secondary winding N2 of a transformer Tr1 and an output inductor Lo2 is connected between the first input terminal 44 and the second input terminal 45a. In FIG. 9 , a first terminal of the secondary winding N2 is connected to the first input terminal 44, a second terminal of the secondary winding N2 is connected to a first terminal of the output inductor Lo2, and a second terminal of the output inductor Lo2 is connected to the second input terminal 45a.

[0119] The second half-bridge inverter 40A has a first DC output terminal 46a and a second DC output terminal 47a. The first DC output terminal 46a is connected to the drain of the third switching element Q3 and the high-potential pole of the third capacitor C3, and is also connected to the output terminal 13. The second DC output terminal 47a is connected to the source of the fourth switching element Q4 and the low-potential pole of the fourth capacitor C4, and is also connected to the output terminal 14.

[0120] The second half-bridge inverter 40A described above full-wave rectifies the secondary voltage V2 generated in the secondary winding N2 by turning on and off the third to fourth switching elements Q3 to Q4, respectively. The second half-bridge inverter 40A then outputs the DC voltage obtained by full-wave rectifying the secondary voltage V2 as the output voltage Vo from the first DC output terminal 46a and the second DC output terminal 47a.

[0121] The control device 5A controls the first half-bridge inverter 3A and the second half-bridge inverter 40A. The control device 5A controls the first switching element Q1 and the second switching element Q2 of the first half-bridge inverter 3A. The control device 5A also controls the third switching element Q3 and the fourth switching element Q4 of the second half-bridge inverter 40A. The control device 5A is configured to provide first to fourth switching signals (control signals) S1 to S4 to the first to fourth switching elements Q1 to Q4, respectively. The first to fourth switching signals S1 to S4 are gate voltages (gate signals) applied between the control terminals and second main terminals of the first to fourth switching elements Q1 to Q4 to turn the first to fourth switching elements Q1 to Q4 on and off. The first to fourth switching signals S1 to S4 are voltages whose voltage levels change between a voltage level (hereinafter also referred to as a high level) higher than the threshold voltages (gate threshold voltages) of the first to fourth switching elements Q1 to Q4 and a voltage level (hereinafter also referred to as a low level) lower than the threshold voltages. The control device 5A is configured to be able to change the frequencies of the first to fourth switching signals S1 to S4. The first to fourth switching signals S1 to S4 are the same as the first to fourth switching signals S1 to S4 described in the first embodiment.

[0122] Furthermore, the control device 5A, like the control device 5 of embodiment 1, makes the duty of the first switching signal S1 that controls the first switching element Q1 equal to the duty of the second switching signal S2 that controls the second switching element Q2. Specifically, the duty of each of the first and second switching signals S1 and S2 is 50%.

[0123] Furthermore, the control device 5A, like the control device 5 of embodiment 1, sets the duty of the third switching signal S3 that controls the third switching element Q3 to be equal to the duty of the fourth switching signal S4 that controls the fourth switching element Q4. Specifically, the duty of each of the third to fourth switching signals S3 to S4 is 50%.

[0124] Similarly to the control device 5 of the first embodiment, the control device 5A controls the first switching element Q1 and the second switching element Q2 so that the mode of the current flowing through the input inductor Li is a discontinuous current mode.

[0125] Furthermore, similar to the control device 5 of the first embodiment, the control device 5A synchronizes the drive timing of the first switching element Q1 and the second switching element Q2 with the drive timing of the third switching element Q3 and the fourth switching element Q4.

[0126] Furthermore, similar to the control device 5 of the first embodiment, the control device 5A controls the DC bus voltage Vdc of the first half-bridge inverter 3A and controls the output voltage Vo of the second half-bridge inverter 40A.

[0127] Similarly to the control device 5 of embodiment 1, the control device 5A controls the switching frequencies of the first switching element Q1 and the second switching element Q2 by PI control based on the command value Vdc* of the DC bus voltage Vdc of the first half-bridge inverter 3A and the detected value [Vdc] of the DC bus voltage Vdc, or by PI control based on the command value Vo* of the output voltage Vo of the second half-bridge inverter 40A and the detected value [Vo] of the output voltage Vo. The control device 5A then sets the switching frequencies of the third switching element Q3 and the fourth switching element Q4 to be the same as the switching frequencies of the first switching element Q1 and the second switching element Q2.

[0128] (3) Summary In the converter device 100A according to the second embodiment described above, the output inductor Lo2 is connected in series to the secondary winding N2, and the output inductor Lo2 is provided between the secondary winding N2 and the second half-bridge inverter 40A. As a result, the output current Io is smoothed by the output inductor Lo2, and the ripple component contained in the output current Io is suppressed, thereby reducing loss in the output capacitor Co due to the output current Io. Therefore, the converter device 100A can achieve high efficiency.

[0129] Furthermore, in the converter device 100A according to the second embodiment, the control device 5A makes the duty of the first switching signal S1 and the duty of the second switching signal S2 equal to each other, thereby simplifying the process of generating the first switching signal S1 and the second switching signal S2.

[0130] Furthermore, in the converter device 100A according to the second embodiment, the control device 5A makes the duty of the third switching signal S3 and the duty of the fourth switching signal S4 equal to each other, thereby simplifying the process of generating the third to fourth switching signals S3 to S4.

[0131] Furthermore, in the converter device 100A according to the second embodiment, the control device 5A synchronizes the drive timings of the first to fourth switching elements Q1 to Q4, thereby simplifying the process of generating the first to fourth switching signals S1 to S4.

[0132] Furthermore, in the converter device 100A according to the second embodiment, the control device 5A controls the first switching element Q1 and the second switching element Q2 so that the mode of the current flowing through the input inductor Li is a discontinuous current mode, thereby improving the power factor.

[0133] Furthermore, in the converter device 100A according to the second embodiment, the control device 5 controls the switching frequencies of the first and second switching elements Q1 and Q2 by PI control based on the command value Vdc* and the detected value [Vdc] of the DC bus voltage Vdc, or by PI control based on the command value Vo* and the detected value [Vo] of the output voltage Vo, thereby making the switching frequencies of the third and fourth switching elements Q3 and Q4 the same as the switching frequencies of the first and second switching elements Q1 and Q2. This allows the converter device 100A according to the second embodiment to suppress fluctuations in the DC bus voltage Vdc or the output voltage Vo during load fluctuations. Suppressing fluctuations in the DC bus voltage Vdc also suppresses fluctuations in the output voltage Vo.

[0134] (Modifications) The above-described first and second embodiments are merely examples of various embodiments of the present disclosure. The above-described first and second embodiments can be modified in various ways depending on the design and the like as long as the object of the present disclosure can be achieved.

[0135] For example, each of the first switching element Q1 and the second switching element Q2 is not limited to a GaN-based MOSFET, but may be, for example, a Si-based MOSFET, a SiC-based MOSFET, or an IGBT (Insulated Gate Bipolar Transistor).

[0136] The third to sixth switching elements Q3 to Q6 are not limited to n-channel MOSFETs but may be p-channel MOSFETs. The MOSFETs constituting the third to sixth switching elements Q3 to Q6 are not limited to Si-based MOSFETs but may be, for example, SiC-based MOSFETs, IGBTs, or GaN-based MOSFETs.

[0137] In the converter device 100 according to the first embodiment, the output inductor Lo1 may be connected between the second DC output terminal 47 of the full-bridge inverter 40 and the low-potential side pole of the output capacitor Co.

[0138] In the converter device 100A according to the second embodiment, the output inductor Lo2 may be connected between the first input terminal 44 and the secondary winding N2 of the second half-bridge inverter 40A.

[0139] The input filter 1 may also be, for example, a common mode filter.

[0140] The input inductor Li is not limited to being connected between the AC power supply 8 and the half-bridge inverter 3 or the first half-bridge inverter 3A, but may also be connected between the AC power supply 8 and the first rectifier 2. That is, the input inductor Li is not limited to being connected between the input terminal 12 and the connection point 33, but may also be connected between the input terminal 11 and the connection point 21. Furthermore, both the input inductor Li connected between the input terminal 12 and the connection point 33 and the input inductor Li connected between the input terminal 11 and the connection point 21 may be provided.

[0141] (Summary) A converter device (100, 100A) according to a first aspect of the present embodiment includes a first rectifier (2), a half-bridge inverter (3, 3A), an input inductor (Li), a transformer (Tr1), a second rectifier (4), output inductors (Lo1, Lo2), and a control device (5, 5A). The first rectifier (2) has a first diode (D1) and a second diode (D2) connected in series, and a first AC output terminal (81) of an AC power supply (8) is connected to a connection point (21) between the first diode (D1) and the second diode (D2). The half-bridge inverter (3, 3A) has a first series circuit (31) including a first switching element (Q1) and a second switching element (Q2), and a second series circuit (32) including a first capacitor (C1) and a second capacitor (C2). The second series circuit (32) is connected in parallel to the first series circuit (31). In the half-bridge inverter (3, 3A), the first switching element (Q1) is connected to the cathode of the first diode (D1). In the half-bridge inverter (3, 3A), the second switching element (Q2) is connected to the anode of the second diode (D2). In the half-bridge inverter (3, 3A), the second AC output terminal (82) of the AC power source (8) is connected to the connection point (33) between the first switching element (Q1) and the second switching element (Q2). The input inductor (Li) is connected between the AC power source (8) and the first rectifier (2) or the half-bridge inverter (3, 3A). The transformer (Tr1) includes a primary winding (N1) and a secondary winding (N2). The primary winding (N1) of the transformer (Tr1) is connected between a first output terminal (34) between the first switching element (Q1) and the second switching element (Q2) and a second output terminal (35) between the first capacitor (C1) and the second capacitor (C2). The second rectifier (4) is connected to the secondary winding (N2) of the transformer (Tr1) and outputs an output voltage (Vo) obtained by rectifying a secondary voltage (V2) generated in the secondary winding (N2) to the output capacitor (Co). The output inductors (Lo1, Lo2) are connected between the secondary winding (N2) and the output capacitor (Co). The control device (5, 5A) controls at least the half-bridge inverter (3).

[0142] The above-described converter device (100, 100A) can achieve high efficiency.

[0143] In the converter device (100) of the second aspect of the embodiment, in the first aspect, the second rectifier (4) is preferably a full-bridge inverter (40) having a third switching element (Q3), a fourth switching element (Q4), a fifth switching element (Q5), and a sixth switching element (Q6). The output inductor (Lo1) is connected between one of a pair of DC output terminals (46, 47) of the full-bridge inverter (40) and an output capacitor (Co). The control device (5) controls the half-bridge inverter (3) and the full-bridge inverter (40).

[0144] The converter device (100) described above can control the output voltage (Vo) by controlling the half-bridge inverter (3) and the full-bridge inverter (40).

[0145] In the converter device (100) of the third aspect of the embodiment, in the second aspect, it is preferable that the control device (5) controls the DC bus voltage (Vdc) of the half-bridge inverter (3) and controls the output voltage (Vo) of the full-bridge inverter (40).

[0146] The converter device (100) described above can control the output voltage (Vo) with high precision.

[0147] In the converter device (100) of the fourth aspect of the embodiment, in the third aspect, it is preferable that the control device (5) makes the duty of the first switching signal (S1) that controls the first switching element (Q1) and the duty of the second switching signal (S2) that controls the second switching element (Q2) equal to each other.

[0148] The converter device (100) described above can simplify the process of generating the first switching signal (S1) and the second switching signal (S2).

[0149] In the converter device (100) of the fifth aspect of the embodiment, in the third or fourth aspect, it is preferable that the control device (5) makes the duty of the third switching signal (S3) that controls the third switching element (Q3), the duty of the fourth switching signal (S4) that controls the fourth switching element (Q4), the duty of the fifth switching signal (S5) that controls the fifth switching element (Q5), and the duty of the sixth switching signal (S6) that controls the sixth switching element (Q6) equal to each other.

[0150] The converter device (100) described above can simplify the process of generating the third to sixth switching signals (S3 to S6).

[0151] In the converter device (100) of the sixth aspect of the embodiment, in any one of the third to fifth aspects, it is preferable that the control device (5) controls the first switching element (Q1) and the second switching element (Q2) so that the mode of the current (IL1) flowing through the input inductor (Li) is a discontinuous current mode.

[0152] The converter device (100) described above is capable of improving the power factor.

[0153] In the converter device (100) of the seventh aspect of the embodiment, in any one of the third to sixth aspects, it is preferable that the control device (5) synchronizes the drive timing of the first switching element (Q1) and the second switching element (Q2) with the drive timing of the third switching element (Q3), the fourth switching element (Q4), the fifth switching element (Q5), and the sixth switching element (Q6).

[0154] The converter device (100) described above can simplify the process of generating the first to sixth switching signals (S1 to S6).

[0155] In the converter device (100) of an eighth aspect according to the present embodiment, in any one of the third to seventh aspects, the control device (5) preferably controls the switching frequencies of the first switching element (Q1) and the second switching element (Q2) by PI control based on a command value (Vdc*) of a DC bus voltage (Vdc) of the half-bridge inverter (3) and a detected value ([Vdc]) of the DC bus voltage (Vdc), or by PI control based on a command value (Vo*) of an output voltage (Vo) of the full-bridge inverter (40) and a detected value ([Vo]) of the output voltage (Vo). The control device (5) sets the switching frequencies of the third switching element (Q3), the fourth switching element (Q4), the fifth switching element (Q5), and the sixth switching element (Q6) to be the same as the switching frequencies of the first switching element (Q1) and the second switching element (Q2).

[0156] The converter device (100) described above can suppress fluctuations in the DC bus voltage (Vdc) or the output voltage (Vo) when the load fluctuates.

[0157] In a converter device (100A) according to a ninth aspect of the embodiment, in the first aspect, the half-bridge inverter is a first half-bridge inverter (3A). The second rectifier (4) is preferably a second half-bridge inverter (40A) having a third switching element (Q3), a fourth switching element (Q4), a third capacitor (C3), and a fourth capacitor (C4). The output inductor (Lo2) is connected in series with the secondary winding (N2). The control device (5A) controls the first half-bridge inverter (3A) and the second half-bridge inverter (40A).

[0158] The converter device (100A) described above can control the output voltage (Vo) by controlling the first half-bridge inverter (3A) and the second half-bridge inverter (40A).

[0159] In the converter device (100A) of the tenth aspect of the embodiment, in the ninth aspect, it is preferable that the control device (5A) controls the DC bus voltage (Vdc) of the first half-bridge inverter (3A) and controls the output voltage (Vo) of the second half-bridge inverter (40A).

[0160] The above-described converter device (100A) can control the output voltage (Vo) with high precision.

[0161] In the converter device (100A) of the eleventh aspect of the embodiment, in the tenth aspect, it is preferable that the control device (5A) makes the duty of the first switching signal (S1) that controls the first switching element (Q1) and the duty of the second switching signal (S2) that controls the second switching element (Q2) equal to each other.

[0162] The converter device (100A) described above can simplify the process of generating the first switching signal (S1) and the second switching signal (S2).

[0163] In the converter device (100A) of the twelfth aspect of the embodiment, in the tenth or eleventh aspect, it is preferable that the control device (5A) makes the duty of the third switching signal (S3) that controls the third switching element (Q3) and the duty of the fourth switching signal (S4) that controls the fourth switching element (Q4) equal to each other.

[0164] The above-described converter device (100A) can simplify the process of generating the third and fourth switching signals (S3 and S4).

[0165] In the converter device (100A) of the thirteenth aspect of the embodiment, in any one of the tenth to twelfth aspects, it is preferable that the control device (5A) controls the first switching element (Q1) and the second switching element (Q2) so that the mode of the current (IL1) flowing through the input inductor (Li) is a discontinuous current mode.

[0166] The above-described converter device (100A) can improve the power factor.

[0167] In the converter device (100A) of the fourteenth aspect of the embodiment, in any one of the tenth to thirteenth aspects, it is preferable that the control device (5A) synchronizes the drive timing of the first switching element (Q1) and the second switching element (Q2) with the drive timing of the third switching element (Q3) and the fourth switching element (Q4).

[0168] The above-described converter device (100A) can simplify the process of generating the first to fourth switching signals (S1 to S4).

[0169] In a converter device (100A) according to a fifteenth aspect of the present embodiment, in any one of the tenth to fourteenth aspects, the control device (5A) preferably controls the switching frequencies of the first switching element (Q1) and the second switching element (Q2) by PI control based on a command value (Vdc*) of a DC bus voltage (Vdc) of the first half-bridge inverter (3A) and a detected value ([Vdc]) of the DC bus voltage (Vdc), or by PI control based on a command value (Vo*) of an output voltage (Vo) of the second half-bridge inverter (40A) and a detected value ([Vo]) of the output voltage (Vo). The control device (5A) sets the switching frequencies of the third switching element (Q3) and the fourth switching element (Q4) to be the same as the switching frequencies of the first switching element (Q1) and the second switching element (Q2).

[0170] The above-described converter device (100A) can suppress fluctuations in the DC bus voltage (Vdc) or the output voltage (Vo) when the load fluctuates.

[0171] 100, 100A Converter device 2 First rectifier 21 Connection point 3 Half-bridge inverter 3A First half-bridge inverter 31 First series circuit 32 Second series circuit 33 Connection point 34 First output terminal 35 Second output terminal 4 Second rectifier 40 Full-bridge inverter 40A Second half-bridge inverter 46 First DC output terminal (DC output terminal) 47 Second DC output terminal (DC output terminal) 5, 5A Control device 8 AC power supply 81 First AC output terminal 82 Second AC output terminal Li Input inductor Lo1, Lo2 Output inductor Tr1 Transformer Q1 First switching element Q2 Second switching element Q3 Third switching element Q4 Fourth switching element Q5 Fifth switching element Q6 Sixth switching element C1 First capacitor C2 Second capacitor Co Output capacitor D1 First diode D2 Second diode N1 Primary winding N2 Secondary winding S1 First switching signal S2 Second switching signal S3 Third switching signal S4 Fourth switching signal S5 Fifth switching signal S6 Sixth switching signal Vdc DC bus voltage Vdc* Command value of DC bus voltage [Vdc] Detected value of DC bus voltage Vo Output voltage Vo* Command value of output voltage [Vo] Detected value of output voltage IL1 Inductor current

Claims

1. A first rectifier having a first diode and a second diode connected in series with each other, a first AC output end of an AC power supply being connected to a connection point between the first diode and the second diode; a half-bridge inverter having a first series circuit of a first switching element and a second switching element and a second series circuit of a first capacitor and a second capacitor connected in parallel to the first series circuit, the first switching element being connected to the cathode of the first diode, the second switching element being connected to the anode of the second diode, and a second AC output end of the AC power supply being connected to the connection point between the first switching element and the second switching element; an input inductor connected between the AC power supply and the first rectifier or the half-bridge inverter; a transformer including a primary winding and a secondary winding, the primary winding being connected between a first output end between the first switching element and the second switching element and a second output end between the first capacitor and the second capacitor; A converter device comprising: a second rectifier connected to the secondary winding of the transformer and outputting an output voltage obtained by rectifying a secondary voltage generated in the secondary winding to an output capacitor; an output inductor connected between the secondary winding and the output capacitor; and a control device that controls at least the half-bridge inverter.

2. The converter device according to claim 1, wherein the second rectifier is a full-bridge inverter having a third switching element, a fourth switching element, a fifth switching element and a sixth switching element, the output inductor is connected between one of a pair of DC output terminals of the full-bridge inverter and the output capacitor, and the control device controls the half-bridge inverter and the full-bridge inverter.

3. The converter device according to claim 2, wherein the control device controls a DC bus voltage of the half-bridge inverter and controls the output voltage of the full-bridge inverter.

4. The converter device according to claim 3, wherein the control device makes a duty of a first switching signal for controlling the first switching element and a duty of a second switching signal for controlling the second switching element equal to each other.

5. A converter device as described in claim 3 or 4, wherein the control device makes the duty of a third switching signal that controls the third switching element, the duty of a fourth switching signal that controls the fourth switching element, the duty of a fifth switching signal that controls the fifth switching element, and the duty of a sixth switching signal that controls the sixth switching element equal to each other.

6. The converter device according to any one of claims 3 to 5, wherein the control device controls the first switching element and the second switching element so that a mode of a current flowing through the input inductor is a discontinuous current mode.

7. A converter device according to any one of claims 3 to 6, wherein the control device synchronizes the drive timing of the first switching element and the second switching element with the drive timing of the third switching element, the fourth switching element, the fifth switching element and the sixth switching element.

8. The converter device according to any one of claims 3 to 7, wherein the control device controls the switching frequencies of the first switching element and the second switching element by PI control based on a command value of the DC bus voltage of the half-bridge inverter and a detected value of the DC bus voltage, or by PI control based on a command value of the output voltage of the full-bridge inverter and a detected value of the output voltage, and makes the switching frequencies of the third switching element, the fourth switching element, the fifth switching element and the sixth switching element the same as the switching frequencies of the first switching element and the second switching element.

9. The converter device according to claim 1, wherein the half-bridge inverter is a first half-bridge inverter, the second rectifier is a second half-bridge inverter having a third switching element, a fourth switching element, a third capacitor and a fourth capacitor, the output inductor is connected in series with the secondary winding, and the control device controls the first half-bridge inverter and the second half-bridge inverter.

10. The converter apparatus of claim 9, wherein the control device controls a DC bus voltage of the first half-bridge inverter and controls the output voltage of the second half-bridge inverter.

11. The converter device according to claim 10, wherein the control device makes a duty of a first switching signal for controlling the first switching element and a duty of a second switching signal for controlling the second switching element equal to each other.

12. The converter device according to claim 10 or 11, wherein the control device makes a duty of a third switching signal for controlling the third switching element and a duty of a fourth switching signal for controlling the fourth switching element equal to each other.

13. The converter device according to any one of claims 10 to 12, wherein the control device controls the first switching element and the second switching element so that a mode of a current flowing through the input inductor is a discontinuous current mode.

14. The converter device according to any one of claims 10 to 13, wherein the control device synchronizes the drive timing of the first switching element and the second switching element with the drive timing of the third switching element and the fourth switching element.

15. The converter device according to any one of claims 10 to 14, wherein the control device controls the switching frequencies of the first switching element and the second switching element by PI control based on a command value of the DC bus voltage of the first half-bridge inverter and a detected value of the DC bus voltage, or by PI control based on a command value of the output voltage of the second half-bridge inverter and a detected value of the output voltage, and makes the switching frequencies of the third switching element and the fourth switching element the same as the switching frequencies of the first switching element and the second switching element.

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