Power conversion device and power conversion system

Abstract

The power conversion device of the present application includes a first power terminal, a first lever, a second lever, a first inductor, a second inductor, a first capacitor, a first transformer, a rectification circuit, a second power terminal, and a control circuit. The first lever includes a first switching element between the first terminal and a first node, a second switching element between the first node and a second node, and a third switching element between the second node and the second terminal. The second lever includes a fourth switching element between the first terminal and a third node, a fifth switching element between the third node and a fourth node, and a sixth switching element between the fourth node and the second terminal. The first inductor is between the second node and a fifth node, and the second inductor is between the fourth node and the fifth node. The first capacitor is between the fifth node and the second terminal. The first transformer includes a first winding and a second winding disposed on a path connecting the first node and the third node.

Description

Technical Field

[0001] This invention relates to a power conversion device and a power conversion system for converting electricity. Background Technology

[0002] Power conversion devices convert electricity by stepping up or stepping down the input voltage. Patent Document 1 discloses a power conversion device having a transformer and an arm consisting of three transistors disposed on the primary side of the transformer, which steps up the input voltage and transforms the stepped-up voltage.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-187021 Summary of the Invention

[0006] In power conversion devices, it is desirable to operate according to a wide variety of input voltages to achieve a wide input voltage range.

[0007] The aim is to provide a power conversion device and power conversion system that can broaden the input voltage range.

[0008] A first power conversion device according to one embodiment of the present invention includes a first power terminal, a first rod, a second rod, a first inductor, a second inductor, a first capacitor, a first transformer, a rectifier circuit, a second power terminal, and a control circuit. The first power terminal is configured to have a first terminal and a second terminal. The first rod is disposed on a first path connecting the first terminal and the second terminal, and has a first switching element, a second switching element, and a third switching element. The first switching element is disposed between the first terminal and a first node, the second switching element is disposed between the first node and a second node, and the third switching element is disposed between the second node and the second terminal. The second rod is disposed on a second path connecting the first terminal and the second terminal, and has a fourth switching element, a fifth switching element, and a sixth switching element. The fourth switching element is disposed between the first terminal and a third node, the fifth switching element is disposed between the third node and the fourth node, and the sixth switching element is disposed between the fourth node and the second terminal. The first inductor is disposed between the second node and the fifth node. The second inductor is disposed between the fourth node and the fifth node. The first capacitor is disposed between the fifth node and the second terminal. The first transformer has a first winding and a second winding, the first winding being disposed on the path connecting the first node and the third node. The rectifier circuit has multiple rectifier elements connected to the second winding. A second power terminal is connected to the rectifier circuit and has a third terminal and a fourth terminal. The control circuit is configured to control the switching action of the first and second levers based on the voltage at the second power terminal.

[0009] A second power conversion device according to one embodiment of the present invention includes a first power terminal, a rod, an inductor, a first capacitor, a second capacitor, a third capacitor, a transformer, a rectifier circuit, a second power terminal, and a control circuit. The first power terminal is configured to have a first terminal and a second terminal. The rod is disposed on a path connecting the first terminal and the second terminal, and has a first switching element, a second switching element, and a third switching element. The first switching element is disposed between the first terminal and a first node, the second switching element is disposed between the first node and a second node, and the third switching element is disposed between the second node and the second terminal. The inductor is disposed between the second node and the third node. The first capacitor is disposed between the third node and the second terminal. The second capacitor is disposed between the first terminal and a fourth node. The third capacitor is disposed between the fourth node and the second terminal. The transformer has a first winding and a second winding, and the first winding is disposed on a path connecting the first node and the fourth node. The rectifier circuit has a plurality of rectifier elements connected to the second winding. The second power terminal is connected to the rectifier circuit and has a third terminal and a fourth terminal. The control circuit is configured to control the switching operation of the rod according to the voltage of the second power terminal.

[0010] One embodiment of the power conversion system of the present invention includes a power conversion device and a DC power supply device. The power conversion device is either the first power conversion device or the second power conversion device described above. The DC power supply device is connected to a first power terminal of the power conversion device.

[0011] According to one embodiment of the present invention, the power conversion device and power conversion system can broaden the input voltage range. Attached Figure Description

[0012] Figure 1 This is a circuit diagram illustrating a structural example of a power conversion system according to the first embodiment of the present invention.

[0013] Figure 2 It means Figure 1 The timing waveform diagram shows an example of an operation of the power conversion system.

[0014] Figure 3 It means Figure 1 Other timing waveforms of an example operation of the power conversion system shown.

[0015] Figure 4A It means Figure 1 The diagram illustrates one operating state of the power conversion system.

[0016] Figure 4B It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0017] Figure 4C It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0018] Figure 4D It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0019] Figure 4E It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0020] Figure 4F It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0021] Figure 5 This is a circuit diagram illustrating a structural example of a power conversion system according to a variation of the first embodiment.

[0022] Figure 6 It means Figure 5The timing waveform diagram shows an example of an operation of the power conversion system.

[0023] Figure 7 This is a circuit diagram illustrating a structural example of a power conversion system of another variation of the first embodiment.

[0024] Figure 8 It means Figure 7 The timing waveform diagram shows an example of an operation of the power conversion system.

[0025] Figure 9 This is a circuit diagram illustrating a structural example of a power conversion system of another variation of the first embodiment.

[0026] Figure 10 It means Figure 9 The timing waveform diagram shows an example of an operation of the power conversion system.

[0027] Figure 11 This is a circuit diagram illustrating a structural example of the power conversion system according to the second embodiment.

[0028] Figure 12 It means Figure 11 The timing waveform diagram shows an example of an operation of the power conversion system.

[0029] Figure 13A It means Figure 11 The diagram illustrates one operating state of the power conversion system.

[0030] Figure 13B It means Figure 11 The diagram illustrates other operating states of the power conversion system.

[0031] Figure 13C It means Figure 11 The diagram illustrates other operating states of the power conversion system.

[0032] Figure 13D It means Figure 11 The diagram illustrates other operating states of the power conversion system. Detailed Implementation

[0033] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The description will proceed in the following order.

[0034] 1. First Implementation Method

[0035] 2. Second Implementation Method

[0036] <First Implementation Method>

[0037] [Structure Example]

[0038] Figure 1 This section illustrates a structural example of a power conversion system 1 incorporating a power conversion device according to an embodiment of the present invention. The power conversion system 1 includes a DC power supply device PDC, a power conversion device 10, and a load device LD. The power conversion system 1 is configured to convert power by stepping down the voltage supplied by the DC power supply device PDC, and then supply the converted power to the load device LD.

[0039] The DC power supply device (PDC) is configured to supply DC power to the power conversion device 10. The DC power supply device (PDC) can also be, for example, a battery. Alternatively, the DC power supply device (PDC) can also include a battery and a DC / DC converter, which converts the DC power supplied by the battery and supplies the converted DC power to the power conversion device 10.

[0040] The power conversion device 10 is configured to convert the voltage (input voltage) supplied by the DC power supply device PDC into electrical power, and then provide the converted electrical power to the load device LD. The power conversion device 10 is an interleaved circuit with two links. The power conversion device 10 has input terminals T11, T12, an input capacitor Cin, links 11, 12, inductors 13, 14, a capacitor 15, a resonant inductor Lr, a resonant capacitor Cr, a transformer 20, a rectifier and smoothing circuit 17, a voltage sensor 18, a control circuit 19, and output terminals T21, T22. The DC power supply device PDC, the input capacitor Cin, links 11, 12, inductors 13, 14, a capacitor 15, the resonant inductor Lr, and the resonant capacitor Cr constitute the primary side circuit of the power conversion system 1, while the rectifier and smoothing circuit 17 and the load device LD constitute the secondary side circuit of the power conversion system 1.

[0041] Input terminals T11 and T12 are configured to supply power from a DC power supply device (PDC). Within the power conversion device 10, input terminal T11 is connected to voltage line L11, and input terminal T12 is connected to reference voltage line L12.

[0042] One end of the input capacitor Cin is connected to voltage line L11, and the other end is connected to reference voltage line L12.

[0043] Rod 11 is disposed on the path connecting voltage line L11 and reference voltage line L12. Rod 11 has three transistors S1 to S3. Rod 12 is disposed on a path connecting voltage line L11 and reference voltage line L12, but on a different path than the path where rod 11 is disposed. Rod 12 has three transistors S4 to S6. Transistors S1 to S6 are switching elements that are switched according to gate signals G1 to G6 respectively. Transistors S1 to S6 are each constructed, for example, using an N-type field-effect transistor (FET). Transistors S1 to S6 each have a parasitic diode Dp. For example, in transistor S1, the anode of the parasitic diode Dp is connected to the source of transistor S1, and the cathode is connected to the drain of transistor S1. In addition, the capacitor Cp representing the parasitic capacitance of transistor S1 is also shown in this figure. The same applies to transistors S2 to S6. Furthermore, although an N-type field-effect transistor is used in this example, any switching element can be used.

[0044] Transistor S1 is configured such that it is positioned between voltage line L11 and node N1, and node N1 is connected to voltage line L11 by being turned on. The drain of transistor S1 is connected to voltage line L11, its gate is supplied with gate signal G1, and its source is connected to node N1. Transistor S2 is configured such that it is positioned between node N1 and node N2, and node N1 is connected to node N2 by being turned on. The drain of transistor S2 is connected to node N1, its gate is supplied with gate signal G2, and its source is connected to node N2. Transistor S3 is configured such that it is positioned between node N2 and reference voltage line L12, and node N2 is connected to reference voltage line L12 by being turned on. The drain of transistor S3 is connected to node N2, its gate is supplied with gate signal G3, and its source is connected to reference voltage line L12. Node N1 is the connection point between the source of transistor S1 and the drain of transistor S2. Node N2 is the connection point between the source of transistor S2 and the drain of transistor S3.

[0045] Transistor S4 is configured such that it is positioned between voltage line L11 and node N3, and node N3 is connected to voltage line L11 by being turned on. The drain of transistor S4 is connected to voltage line L11, its gate is supplied with gate signal G4, and its source is connected to node N3. Transistor S5 is configured such that it is positioned between node N3 and node N4, and node N3 is connected to node N4 by being turned on. The drain of transistor S5 is connected to node N3, its gate is supplied with gate signal G5, and its source is connected to node N4. Transistor S6 is configured such that it is positioned between node N4 and reference voltage line L12, and node N4 is connected to reference voltage line L12 by being turned on. The drain of transistor S6 is connected to node N4, its gate is supplied with gate signal G6, and its source is connected to reference voltage line L12. Node N3 is the connection point between the source of transistor S4 and the drain of transistor S5. Node N4 is the connection point between the source of transistor S5 and the drain of transistor S6.

[0046] One end of inductor 13 is connected to node N2 of rod 11, and the other end is connected to node N5. One end of inductor 14 is connected to node N4 of rod 12, and the other end is connected to node N5. One end of capacitor 15 is connected to node N5, and the other end is connected to reference voltage line L12.

[0047] One end of the resonant inductor Lr is connected to node N1 of rod 11, and the other end is connected to one end of winding 21 of transformer 20 (described later). One end of the resonant capacitor Cr is connected to node N3 of rod 12, and the other end is connected to the other end of winding 21 of transformer 20 (described later).

[0048] Transformer 20 is configured to DC-isolate and AC-couple the primary and secondary circuits, and to convert the AC voltage supplied from the primary circuit using the transformer ratio N, and then supply the converted AC voltage to the secondary circuit. Transformer 20 has windings 21, 22A, and 22B. One end of winding 21 is connected to the other end of the resonant inductor Lr, and the other end is connected to the other end of the resonant capacitor Cr. One end of winding 22A is connected to the cathode of diode DA (described later) in the rectifier-smoothing circuit 17, and the other end is connected to voltage line L21. One end of winding 22B is connected to voltage line L21, and the other end is connected to the cathode of diode DB (described later) in the rectifier-smoothing circuit 17.

[0049] The rectifier-smoothing circuit 17 is configured to generate a DC voltage by rectifying the AC voltage output from the windings 22A and 22B of the transformer 20. The rectifier-smoothing circuit 17 includes diodes DA and DB, and a capacitor Cout. The anode of diode DA is connected to the reference voltage line L22, and its cathode is connected to one end of the winding 22A of the transformer 20. The anode of diode DB is connected to the reference voltage line L22, and its cathode is connected to the other end of the winding 22B of the transformer 20. One end of the capacitor Cout is connected to the voltage line L21, and the other end is connected to the reference voltage line L22.

[0050] Voltage sensor 18 is configured to detect the voltage on voltage line L21. One end of voltage sensor 18 is connected to voltage line L21, and the other end is connected to reference voltage line L22. Voltage sensor 18 detects the voltage on voltage line L21, which is referenced to the voltage on reference voltage line L22, and uses it as the output voltage Vout. Furthermore, voltage sensor 18 provides the detection result of output voltage Vout to control circuit 19.

[0051] The control circuit 19 is configured to control the operation of levers 11 and 12 based on the output voltage Vout detected by the voltage sensor 18, thereby controlling the operation of the power conversion device 10. Specifically, the control circuit 19 generates gate signals G1 to G6 based on the output voltage Vout, and performs PWM (Pulse Width Modulation) control through these gate signals G1 to G6, thereby controlling the operation of the power conversion device 10. Furthermore, although in this example the operation of levers 11 and 12 is controlled based on the output voltage Vout detected by the voltage sensor 18, it is not limited to this. Alternatively, the control circuit 19 may estimate the output voltage Vout and control the operation of levers 11 and 12 based on the estimated output voltage Vout. Specifically, the control circuit 19 may, for example, estimate the output voltage Vout based on the voltage between the two ends of the winding 21 of the transformer 20 and the duty cycle of power transfer from the primary circuit to the secondary circuit (the duty cycle of the AC voltage Vac, described later). Furthermore, the control circuit 19 can, for example, estimate the output voltage Vout based on the switching frequency of the levers 11 and 12, the inductance of the resonant inductor Lr, the capacitance of the resonant capacitor Cr, and the voltage across the resonant inductor Lr.

[0052] Output terminals T21 and T22 are configured to supply DC power generated by the power conversion device 10 to the load device LD. Within the power conversion device 10, output terminal T21 is connected to voltage line L21, and output terminal T22 is connected to reference voltage line L22.

[0053] The load device LD is the load of the power conversion device 10. The load device LD can also be a constant current load, for example.

[0054] Through this structure, in the power conversion system 1, the voltage supplied by the DC power supply device PDC is stepped down, thereby converting the power and providing the converted power to the load device LD.

[0055] Here, input terminals T11 and T12 correspond to a specific example of the "first power terminal" of this disclosure. Input terminal T11 corresponds to a specific example of the "first wiring terminal" of this disclosure. Input terminal T12 corresponds to a specific example of the "second wiring terminal" of this disclosure. Rod 11 corresponds to a specific example of the "first rod" of this disclosure. Rod 12 corresponds to a specific example of the "second rod" of this disclosure. Transistor S1 corresponds to a specific example of the "first switching element" of this disclosure. Transistor S2 corresponds to a specific example of the "second switching element" of this disclosure. Transistor S3 corresponds to a specific example of the "third switching element" of this disclosure. Node N1 corresponds to a specific example of the "first node" of this disclosure. Node N2 corresponds to a specific example of the "second node" of this disclosure. Transistor S4 corresponds to a specific example of the "fourth switching element" of this disclosure. Transistor S5 corresponds to a specific example of the "fifth switching element" of this disclosure. Transistor S6 corresponds to a specific example of the "sixth switching element" of this disclosure. Node N3 corresponds to a specific example of the "third node" of this disclosure. Node N4 corresponds to a specific example of the "fourth node" of this disclosure. Inductor 13 corresponds to a specific example of the "first inductor" of this disclosure. Inductor 14 corresponds to a specific example of the "second inductor" of this disclosure. Capacitor 15 corresponds to a specific example of the "first capacitor" of this disclosure. Node N5 corresponds to a specific example of the "fifth node" of this disclosure. Transformer 20 corresponds to a specific example of the "first transformer" of this disclosure. Winding 21 corresponds to a specific example of the "first winding" of this disclosure. Windings 22A and 22B correspond to a specific example of the "second winding" of this disclosure. Rectifier smoothing circuit 17 corresponds to a specific example of the "rectifier circuit" of this disclosure. Diodes DA and DB correspond to a specific example of the "multiple rectifier elements" of this disclosure. Output terminals T21 and T22 correspond to a specific example of the "second power terminal" of this disclosure. Output terminal T21 corresponds to a specific example of the "third terminal" of this disclosure. Output terminal T22 corresponds to a specific example of the "fourth terminal" of this disclosure. Control circuit 19 corresponds to a specific example of the "control circuit" of this disclosure. DC power supply device PDC corresponds to a specific example of the "DC power supply device" of this disclosure. Resonant inductor Lr corresponds to a specific example of the "resonant inductor" of this disclosure. Resonant capacitor Cr corresponds to a specific example of the "resonant capacitor" of this disclosure.

[0056] [Actions and Functions]

[0057] Next, the operation and function of the power conversion system 1 in this embodiment will be explained.

[0058] (Overall action summary)

[0059] First, refer to Figure 1 2. A general overview of the operation of the power conversion system 1 is provided. Transistors S1 to S6 of levers 11 and 12 switch according to gate signals G1 to G6, respectively. Transformer 20 converts the AC voltage supplied from the primary circuit at its transformation ratio N and provides the converted AC voltage to the secondary circuit. Rectification and smoothing circuit 17 performs rectification and smoothing based on the AC voltage supplied from transformer 20. Voltage sensor 18 detects the voltage on voltage line L21, which is based on the voltage on reference voltage line L22, and uses it as the output voltage Vout. Control circuit 19 controls the operation of levers 11 and 12 based on the output voltage Vout detected by voltage sensor 18, thereby controlling the operation of power conversion device 10. Thus, power conversion system 1 converts power by stepping down the voltage supplied by DC power supply device PDC and provides the converted power to load device LD.

[0060] (Detailed actions)

[0061] Figure 2 This represents an example of an operation of the power conversion system 1. (A) to (F) represent the waveforms of gate signals G1 to G6, respectively. (G) represents the waveform of the voltage (AC voltage Vac) at node N1 based on the voltage at node N3, and the waveform of the current (AC current Iac) flowing from one end (node ​​N1 side) of the winding 21 of transformer 20 to the other end (node ​​N3 side). (H) represents the waveform of the current (inductor current IL13) flowing from node N5 through inductor 13 to node N2, and the waveform of the current (inductor current IL14) flowing from node N5 through inductor 14 to node N4. Figure 2 In (A) to (F), "ON" and "OFF" respectively represent the switching states of transistors S1 to S6 that are supplied with gate signals G1 to G6. In this example, the DC power supply device PDC supplies a DC voltage of 100V to the power conversion device 10.

[0062] The power conversion system 1 operates by repeatedly performing actions during the period from time t1 to t5. The length of the period from time t1 to t5 is the switching period Tsw. The period from time t1 to t5 includes the period from time t1 to t2 (P1), the period from time t2 to t3 (P2), the period from time t3 to t4 (P3), and the period from time t4 to t5 (P4).

[0063] The control circuit 19 generates gate signals G1 to G6 based on the output voltage Vout, and performs PWM control through these gate signals G1 to G6, thereby controlling the operation of the power conversion device 10.

[0064] At time t1, control circuit 19 changes gate signals G1 and G6 from high level to low level. Figure 2 (A), (F)). Additionally, at the moment when only the dead time Td (not shown) has elapsed from time t1, the control circuit 19 changes the gate signals G3 and G5 from low to high. Figure 2 (C), (E)). Thus, transistors S2 to S5 are turned on, and transistors S1 and S6 are turned off.

[0065] At time t2, control circuit 19 changes gate signal G2 from high level to low level. Figure 2 (B)). Additionally, at the moment when only the dead time Td (not shown) has elapsed from time t2, the control circuit 19 changes the gate signal G1 from low to high. Figure 2 (A)). As a result, transistors S1, S3 to S5 are turned on, and transistors S2 and S6 are turned off.

[0066] At time t3, control circuit 19 changes gate signals G3 and G4 from high level to low level. Figure 2 (C), (D)). Additionally, at the moment when only the dead time Td (not shown) has elapsed from time t3, control circuit 19 changes gate signals G2 and G6 from low to high. Figure 2 (B), (F)). Thus, transistors S1, S2, S5, and S6 become on, and transistors S3 and S4 become off.

[0067] At time t4, control circuit 19 changes gate signal G5 from high level to low level. Figure 2 (E)). Additionally, at the moment when only the dead time Td (not shown) has elapsed from time t4, the control circuit 19 changes the gate signal G4 from low to high. Figure 2 (D)). As a result, transistors S1, S2, S4, and S6 are turned on, and transistors S3 and S5 are turned off.

[0068] Control circuit 19 controls the operation of transistors S1 to S6 by changing the duty cycle of transistors S1, S2, S4, and S5 according to the output voltage Vout. Additionally, control circuit 19 maintains the duty cycle of transistors S3 and S6 at approximately 50%. The duty cycle of transistor S1 is the ratio of the time transistor S1 is in the on-state corresponding to the switching cycle Tsw. The same applies to transistors S2 to S6. In this example, since the voltage supplied by the DC power supply device PDC (input voltage Vin) is 100V, the voltage at node N5 is approximately 50V.

[0069] In power conversion system 1, such as Figure 2As shown in (H), inductor currents IL13 and IL14 flow through inductors 13 and 14, as follows: Figure 2 As shown in (G), an AC voltage Vac is generated between nodes N1 and N3. In this example, the AC voltage Vac is 0V during periods P2 and P4, approximately -100V during period P1 (roughly the same as -Vin), and approximately 100V during period P3 (roughly the same as Vin). Then, as... Figure 2 As shown in (G), an alternating current Iac flows through the winding 21 of transformer 20. Transformer 20 converts the AC signal supplied from the primary circuit at its transformation ratio N and provides the converted AC signal to the secondary circuit. Thus, in power conversion system 1, current flows through the secondary circuit, and the rectifier-smoothing circuit 17 performs rectification and smoothing operations. In this way, power conversion system 1 generates a DC voltage and provides the generated DC voltage to the load device LD.

[0070] When control circuit 19 changes the duty cycle of transistors S1, S2, S4, and S5, such as... Figure 2 As shown by the arrows in (A) and (B), the transition times of gate signals G1 and G2 near time t2 are changed, and as... Figure 2 As indicated by the arrows in (D) and (E), the transition times of gate signals G4 and G5 near time t4 are changed. Specifically, control circuit 19 changes the transition time of gate signal G1 from low to high and the transition time of gate signal G2 from high to low near time t2. Furthermore, control circuit 19 changes the transition time of gate signal G4 from low to high and the transition time of gate signal G5 from high to low near time t4. Thus, power conversion system 1... Figure 2 As indicated by the arrow in (G), the transition times of the AC voltage Vac near time t2 and near time t4 are changed, thereby altering the duty cycle of the AC voltage Vac. The duty cycle of the AC voltage Vac is the ratio of the time during which the AC voltage Vac is not 0V, corresponding to the time of the switching period Tsw. The result is that the power transferred from the primary circuit to the secondary circuit changes in the power conversion system 1. The control circuit 19 changes the transition times of transistors S1, S2, S4, and S5 according to the output voltage Vout, thereby changing the duty cycle of the AC voltage Vac, and thus controlling the operation of the power conversion system 1 so that the output voltage Vout remains constant despite changes in the input voltage Vin.

[0071] For example, if the voltage supplied by the DC power supply device PDC (input voltage Vin) is constant, and the load current flowing through the load device LD increases, then the control circuit 19 extends the switching period Tsw to adjust the resonance condition, thus maintaining a constant duty cycle of the AC voltage Vac. Specifically, the control circuit 19 extends the lengths of the periods P1 (t1-t2), P2 (t2-t3), P3 (t3-t4), and P4 (t4-t5) by the same ratio as the switching period Tsw. Therefore, in the power conversion system 1, the output voltage Vout can be maintained.

[0072] Furthermore, for example, if the load current flowing through the load device LD is maintained, and the voltage supplied by the DC power supply device PDC (input voltage Vin) increases, then the control circuit 19 keeps the switching period Tsw constant and controls the duty cycle of the AC voltage Vac, reducing it by an amount corresponding to the increase in the input voltage. Specifically, the control circuit 19 shortens the lengths of periods P1 and P3 and extends the lengths of periods P2 and P4. Thus, in the power conversion system 1, the output voltage Vout can be maintained.

[0073] The operation of the power conversion system 1 during the period from time t1 to t5 will be described in detail below.

[0074] Figure 3The following diagrams illustrate the detailed operation of the power conversion system 1: (A) the waveforms of gate signals G1 to G6; (B) the waveforms of the voltage at node N1 (AC voltage Vac) referenced to the voltage at node N3 and the waveform of the current flowing from one end of winding 21 of transformer 20 to the other (AC current Iac); (C) the waveform of the current flowing from node N5 through inductor 13 to node N2 (inductor current IL13); and (D) the waveform of the current between the drain and source of transistor S1. (E) shows the waveforms of the voltage Vds1, the current IS1 flowing from the drain to the source of transistor S1, and the current ID1 flowing through the parasitic diode Dp of transistor S1; (F) shows the waveforms of the voltage Vds2 between the drain and source of transistor S2, the current IS2 flowing from the drain to the source of transistor S2, and the current ID2 flowing through the parasitic diode Dp of transistor S2; and (E) shows the waveforms of the voltage Vds3 between the drain and source of transistor S3. The waveforms of the current IS3 flowing from the drain to the source of transistor S3 and the current ID3 flowing through the parasitic diode Dp of transistor S3 are shown in Figure 1. (G) represents the waveform of the current (inductor current IL14) flowing from node N5 through inductor 14 to node N4. (H) represents the waveforms of the voltage Vds4 between the drain and source of transistor S4, the current IS4 flowing from the drain to the source of transistor S4, and the current ID3 flowing through the parasitic diode Dp of transistor S4. The waveforms of ID4 are shown in (I), which represents the waveforms of the voltage Vds5 between the drain and source of transistor S5, the current IS5 flowing from the drain to the source of the main body of transistor S5, and the current ID5 flowing through the parasitic diode Dp of transistor S5. The waveforms of (J) represent the waveforms of the voltage Vds6 between the drain and source of transistor S6, the current IS6 flowing from the drain to the source of the main body of transistor S6, and the current ID6 flowing through the parasitic diode Dp of transistor S6.

[0075] Figures 4A-4F This indicates the operation of power conversion system 1 with six operating states, ST1 to ST6. Figures 4A-4F For ease of explanation, the power conversion system 1 is described more simply. In the following text, the current flowing through inductors 13 and 14 is referred to as current I1, the current flowing through the winding 21 of transformer 20 is referred to as I2, the current flowing into or out of DC power supply device PDC is referred to as I3, and the current flowing through the secondary circuit is referred to as I9.

[0076] During the period P1 starting from time t1, such as Figure 2 As shown, transistors S3 and S5 change from the off state to the on state, transistors S1 and S6 change from the on state to the off state, and transistors S2 and S4 remain on. During this period P1, the operating state ST first becomes the operating state ST1. Figure 4A ), and then becomes action state ST2 ( Figure 4B ).

[0077] In action state ST1 ( Figure 4A In the primary circuit, current I1 flows sequentially through node N2, inductor 13, node N5, inductor 14, node N4, transistor S5, and node N3. Current I2 flows sequentially through node N3, resonant capacitor Cr, winding 21 of transformer 20, resonant inductor Lr, node N1, transistor S2, and node N2. Current I3 flows sequentially through node N3, transistor S4, voltage line L11, DC power supply device PDC, reference voltage line L12, transistor S3, and node N2. Because the current I1 flowing through inductors 13 and 14 is greater than the current I2 flowing through the transformer, current I3 flows in the DC power supply device PDC, resulting in energy regeneration.

[0078] In transistors S3 and S5, during the dead time Td, current flows through the parasitic diode Dp, and the gate signals G3 and G5 change from low to high. After that, current flows through the body of transistors S3 and S5. Figure 3 (A), (F), (I)). In this way, transistors S3 and S5 can switch from the off state to the on state when the drain-source voltage is low, thus achieving so-called soft switching. As a result, efficiency can be improved in power conversion system 1.

[0079] like Figure 3 As shown in (F) and (H), the absolute values ​​of currents IS3 and IS4 gradually decrease, and currents IS3 and IS4 change from negative to positive. Therefore, from the operating state ST1 ( Figure 4A ) becomes action state ST2( Figure 4B ).

[0080] In operating state ST2, in the primary circuit, current I1 flows sequentially through node N2, inductor 13, node N5, inductor 14, node N4, transistor S5, and node N3. Current I2 flows sequentially through node N3, resonant capacitor Cr, winding 21 of transformer 20, resonant inductor Lr, node N1, transistor S2, and node N2. Current I3 flows sequentially through node N2, transistor S3, reference voltage line L12, DC power supply device PDC, voltage line L11, transistor S4, and node N3. That is, before and after changing from operating state ST1 to operating state ST2, the direction of current I3 is reversed, ending the regeneration operation of operating state ST1. In the secondary circuit, current I9 flows sequentially through winding 22A, capacitor Cout, load device LD, diode DA, and winding 22A. Thus, power is transferred from the primary circuit to the secondary circuit.

[0081] During the period P2 starting from time t2, as Figure 2 As shown, transistor S1 changes from the off state to the on state, transistor S2 changes from the on state to the off state, transistors S3 to S5 remain on state, and transistor S6 remains off state. During this period, P2 changes from operating state ST to operating state ST3. Figure 4C ).

[0082] In operating state ST3, in the primary circuit, current I1 flows sequentially through node N3, transistor S5, node N4, inductor 14, node N5, inductor 13, and node N2. Current I2 flows sequentially through node N3, resonant capacitor Cr, winding 21 of transformer 20, resonant inductor Lr, node N1, transistor S1, and voltage line L11. Current I3 flows sequentially through node N2, transistor S3, reference voltage line L12, DC power supply device PDC, voltage line L11, transistor S4, and node N3.

[0083] In transistor S1, during the dead time Td, current flows through the parasitic diode Dp, the gate signal G1 changes from low to high, and then current flows through the body of transistor S1. Figure 3 (A), (D)). In this way, transistor S1 can switch from the off state to the on state when the voltage between the drain and source is small, thus achieving so-called soft switching. As a result, efficiency can be improved in power conversion system 1.

[0084] In a structure with a resonant circuit (resonant inductor Lr and resonant capacitor Cr), during the period when the energy stored in the resonant circuit in P4 is released, the operating state ST2 ( Figure 4B Similarly, current I9 flows in the secondary circuit. Thus, electricity is transferred from the primary circuit to the secondary circuit.

[0085] During the period P3 starting from time t3, such as Figure 2 As shown, transistors S2 and S6 change from the off state to the on state, transistors S3 and S4 change from the on state to the off state, and transistors S1 and S5 remain on. During this period, P3, the operating state ST first becomes the operating state ST4. Figure 4D ), then becomes action state ST5 ( Figure 4E ).

[0086] In action state ST4 ( Figure 4DIn the primary circuit, current I1 flows sequentially through node N4, inductor 14, node N5, inductor 13, node N2, transistor S2, and node N1. Current I2 flows sequentially through node N1, resonant inductor Lr, winding 21 of transformer 20, resonant capacitor Cr, node N3, transistor S5, and node N4. Current I3 flows sequentially through node N1, transistor S1, voltage line L11, DC power supply device PDC, reference voltage line L12, transistor S6, and node N4. Because the current I1 flowing through inductors 13 and 14 is greater than the current I2 flowing through the transformer, current I3 flows in the DC power supply device PDC, resulting in energy regeneration.

[0087] In transistors S2 and S6, during the dead time Td, current flows through the parasitic diode Dp, and the gate signals G2 and G6 change from low to high. After that, current flows through the body of transistors S2 and S6. Figure 3 (A), (E), (J)). In this way, transistors S2 and S6 can switch from the off state to the on state when the drain-source voltage is low, thus achieving so-called soft switching. As a result, efficiency can be improved in power conversion system 1.

[0088] like Figure 3 As shown in (D) and (J), the absolute values ​​of currents IS1 and IS6 gradually decrease, and currents IS1 and IS6 change from negative to positive. Therefore, from operating state ST4 ( Figure 4D ) becomes action state ST5( Figure 4E ).

[0089] In operating state ST5, in the primary circuit, current I1 flows sequentially through node N4, inductor 14, node N5, inductor 13, node N2, transistor S2, and node N1. Current I2 flows sequentially through node N1, resonant inductor Lr, winding 21 of transformer 20, resonant capacitor Cr, node N3, transistor S5, and node N4. Current I3 flows sequentially through node N4, transistor S6, reference voltage line L12, DC power supply device PDC, voltage line L11, transistor S1, and node N1. That is, before and after changing from operating state ST4 to operating state ST5, the direction of current I3 is reversed, ending the regeneration operation of operating state ST4. In the secondary circuit, current I9 flows sequentially through winding 22B, capacitor Cout, load device LD, diode DB, and winding 22B. Thus, power is transferred from the primary circuit to the secondary circuit.

[0090] During the period P4 starting from time t4, as Figure 2As shown, transistor S4 changes from the off state to the on state, transistor S5 changes from the on state to the off state, transistors S1, S2, and S6 remain on state, and transistor S3 remains off state. During this period, P4 changes from operating state ST to operating state ST6. Figure 4F ).

[0091] In operating state ST6, in the primary circuit, current I1 flows sequentially through node N1, transistor S2, node N2, inductor 13, node N5, inductor 14, and node N4. Current I2 flows sequentially through node N1, resonant inductor Lr, winding 21 of transformer 20, resonant capacitor Cr, node N3, transistor S4, and voltage line L11. Current I3 flows sequentially through node N4, transistor S6, reference voltage line L12, DC power supply device PDC, voltage line L11, transistor S1, and node N1.

[0092] In transistor S4, during the dead time Td, current flows through the parasitic diode Dp, the gate signal G4 changes from low to high, and then current flows through the body of transistor S4. Figure 3 (A), (H)). In this way, transistor S4 can switch from the off state to the on state when the voltage between the drain and source is small, thus achieving so-called soft switching. As a result, efficiency can be improved in power conversion system 1.

[0093] In a structure with a resonant circuit (resonant inductor Lr and resonant capacitor Cr), during the period when the energy stored in the resonant circuit in P2 is released, the operating state ST5 ( Figure 4E Similarly, current I9 flows in the secondary circuit. Thus, electricity is transferred from the primary circuit to the secondary circuit.

[0094] In the power conversion system 1, rods 11 and 12, inductors 13 and 14, and capacitor 15 are provided. Rod 11 is positioned on a first path connecting input terminal T11 and input terminal T12, and includes transistors S1, S2, and S3. Transistor S1 is positioned between input terminal T11 and node N1, transistor S2 between node N1 and node N2, and transistor S3 between node N2 and input terminal T12. Rod 12 is positioned on a second path connecting input terminal T11 and input terminal T12, and includes transistors S4, S5, and S6. Transistor S4 is positioned between input terminal T11 and node N3, transistor S5 between node N3 and node N4, and transistor S6 between node N4 and input terminal T12. Inductor 13 is positioned between node N2 and node N5. Inductor 14 is positioned between node N4 and node N5. Capacitor 15 is positioned between node N5 and input terminal T12. Therefore, power conversion system 1, through, as follows Figure 2 The action shown changes the duty cycle of the AC voltage Vac, thereby altering the power transferred from the primary circuit to the secondary circuit.

[0095] Specifically, control circuit 19 can control the switching operation of transistors S1 to S6 according to the output voltage Vout, thereby changing the duty cycle of transistors S1, S2, S4, and S5, and maintaining the duty cycle of transistors S3 and S6. For example, control circuit 19... Figure 2 As shown, during the period when transistor S3 is in the on state, the switching time of transistor S1 from the off state to the on state and the switching time of transistor S2 from the on state to the off state are changed. Furthermore, during the period when transistor S6 is in the on state, the control circuit 19 changes the switching time of transistor S4 from the off state to the on state and the switching time of transistor S5 from the on state to the off state. Thus, the control circuit 19 changes the duty cycle of transistors S1, S2, S4, and S5. Therefore, for example, when the voltage supplied by the DC power supply device PDC (input voltage Vin) is high, by decreasing the duty cycle of transistors S2 and S5 and increasing the duty cycle of transistors S1 and S4, the output voltage Vout can be maintained. Conversely, for example, when the voltage supplied by the DC power supply device PDC (input voltage Vin) is low, by increasing the duty cycle of transistors S2 and S5 and decreasing the duty cycle of transistors S1 and S4, the output voltage Vout can be maintained. The duty cycles of transistors S1, S2, S4, and S5 are set in a range, for example, between 50% and 100%. This allows for a wider input voltage range in the power conversion system 1.

[0096] Additionally, in power conversion system 1, such as Figure 2As shown in (A) of 3, during the period near time t1 when transistor S2 is in the on state, transistor S3 is turned on after a dead time Td elapsed from the time when transistor S1 is in the off state. Similarly, during the period near time t2 when transistor S3 is in the on state, transistor S1 is turned on after a dead time Td elapsed from the time when transistor S2 is in the off state. Likewise, during the period near time t3 when transistor S1 is in the on state, transistor S2 is turned on after a dead time Td elapsed from the time when transistor S3 is in the off state. The same applies to transistors S4 to S6. Therefore, in the power conversion system 1, because transistors S1 to S6 can be soft-switched, efficiency can be improved.

[0097] [Effect]

[0098] As described above, in this embodiment, rods 11 and 12, inductors 13 and 14, and capacitor 15 are provided. Rod 11 is disposed on a first path connecting input terminal T11 and input terminal T12, and has transistors S1, S2, and S3. Transistor S1 is disposed between input terminal T11 and node N1, transistor S2 is disposed between node N1 and node N2, and transistor S3 is disposed between node N2 and input terminal T12. Rod 12 is disposed on a second path connecting input terminal T11 and input terminal T12, and has transistors S4, S5, and S6. Transistor S4 is disposed between input terminal T11 and node N3, transistor S5 is disposed between node N3 and node N4, and transistor S6 is disposed between node N4 and input terminal T12. Inductor 13 is disposed between node N2 and node N5. Inductor 14 is disposed between node N4 and node N5. Capacitor 15 is disposed between node N5 and input terminal T12. This widens the input voltage range.

[0099] In this embodiment, since the duty cycle of transistors S1, S2, S4, and S5 can be changed according to the output voltage, while the duty cycle of transistors S3 and S6 is maintained, the input voltage range can be widened.

[0100] In this embodiment, since transistor S3 is turned on when transistor S2 is in the on state, and transistor S1 is turned on when a predetermined time has elapsed since the time when transistor S1 is in the off state; and transistor S1 is turned on when transistor S2 is in the on state, and transistor S2 is turned on when transistor S3 is in the off state, efficiency can be improved.

[0101] [Variation Example 1-1]

[0102] In the above embodiment, although inductors 13 and 14 are provided, the invention is not limited to this. As an alternative, such as... Figure 5 As shown in the power conversion system 1A, a transformer 30A can also be installed. This power conversion system 1A includes a power conversion device 10A. The power conversion device 10A includes a transformer 30A. The transformer 30A has windings 33 and 34. One end of winding 33 is connected to node N2 of the rod 11, and the other end is connected to node N5. One end of winding 34 is connected to node N5, and the other end is connected to node N4 of the rod 12. Winding 33 corresponds to the inductor 13 of the first embodiment described above, and winding 34 corresponds to the inductor 14 of the first embodiment described above. Figure 2 As shown in (H), since the inductor current IL13 flowing through inductor 13 and the inductor current IL14 flowing through inductor 14 are approximately the same in magnitude, and the polarities of the inductor currents IL13 and IL14 are opposite, in this modified example, inductors 13 and 14 are replaced by transformer 30A. In this way, by replacing the two inductors 13 and 14 with transformer 30A, the circuit can be miniaturized. Here, transformer 30A corresponds to a specific example of the "second transformer" of this disclosure.

[0103] Figure 6 This example illustrates an operation of the power conversion system 1A. (A) shows the waveform of the voltage (AC voltage Vac) at node N1, based on the voltage at node N3, and the waveform of the current (AC current Iac) flowing from one end (node ​​N1 side) of winding 21 of transformer 20 to the other end (node ​​N3 side). (B) shows the waveform of the current (transformer current IL33) flowing from node N5 through winding 33 to node N2, and the waveform of the current (transformer current IL34) flowing from node N5 through winding 34 to node N4. In this example, the DC power supply device PDC supplies a 100V DC voltage to the power conversion device 10A. Figure 6 (A) and (B) correspond to the embodiments described above. Figure 2 (G), (H). The power conversion system 1A is capable of performing the same operation as the power conversion system 1 of the above-described embodiment.

[0104] [Variations 1-2]

[0105] In the above embodiments, although a Figure 1 The rectifier smoothing circuit 17 shown is an example, but not limited to it. Several examples are provided below for detailed explanation.

[0106] Figure 7This illustrates a structural example of the power conversion system 1B according to this modification. The power conversion system 1B includes a power conversion device 10B. The power conversion device 10B has members 11 and 12, a transformer 20, and a rectifier-smoothing circuit 17B. One end of the winding 21 of the transformer 20 is connected to node N1 of member 11, and the other end is connected to node N3 of member 12. One end of the winding 22A is connected to the anode of diode DA of the rectifier-smoothing circuit 17B, and the other end is connected to a reference voltage line L22. One end of the winding 22B is connected to the reference voltage line L22, and the other end is connected to the anode of diode DB of the rectifier-smoothing circuit 17B. The rectifier-smoothing circuit 17B includes diodes DA and DB, an inductor 33B, and a capacitor Cout. The anode of diode DA is connected to one end of the winding 22A of the transformer 20, and the cathode is connected to the cathode of diode DB and one end of inductor 33B. The anode of diode DB is connected to the other end of winding 22B of transformer 20, and the cathode is connected to the cathode of diode DA and one end of inductor 33B. One end of inductor 33B is connected to the cathode of diodes DA and DB, and the other end is connected to voltage line L21. One end of capacitor Cout is connected to voltage line L21, and the other end is connected to reference voltage line L22. In this example, although one end of inductor 33B is connected to the cathode of diodes DA and DB, and the other end is connected to voltage line L21, it is not a limitation. Alternatively, one end of inductor 33B may be connected, for example, to the other end of winding 22A and one end of winding 22B, and the other end is connected to reference voltage line L22. Rectifier smoothing circuit 17B corresponds to a specific example of the "rectifier circuit" of this disclosure. Diodes DA and DB correspond to a specific example of the "multiple rectifier elements" of this disclosure.

[0107] In this example, the resonant circuit (resonant inductor Lr and resonant capacitor Cr) is omitted. In this structure, if the voltage supplied by the DC power supply device PDC (input voltage Vin) increases while the load current flowing through the load device LD is maintained, the control circuit 19 keeps the switching period Tsw constant and controls the duty cycle of the AC voltage Vac to decrease it by an amount corresponding to the increase in the input voltage, while keeping the load current of the load device LD constant. Specifically, the control circuit 19 shortens the lengths of periods P1 and P3 and extends the lengths of periods P2 and P4. Thus, in the power conversion system 1B, the output voltage Vout can be maintained.

[0108] Figure 8 This represents an example of an operation of the power conversion system 1B. Figure 8 Corresponding to the above embodiments Figure 3 The power conversion system 1B is capable of performing the same operations as the power conversion system 1 described in the above-described embodiment.

[0109] Figure 9This illustrates a structural example of the power conversion system 1C of this modification. The power conversion system 1C includes a power conversion device 10C. The power conversion device 10C has a transformer 20C and a rectifier-smoothing circuit 17C. The transformer 20C has windings 21 and 22. One end of winding 21 is connected to the other end of a resonant inductor Lr, and the other end is connected to the other end of a resonant capacitor Cr. One end of winding 22 is connected to node N6 of the rectifier-smoothing circuit 17C, and the other end is connected to node N7 of the rectifier-smoothing circuit 17C. The rectifier-smoothing circuit 17C is a bridge circuit, having diodes D11 to D14 and a capacitor Cout. The anode of diode D11 is connected to node N6, and the cathode is connected to voltage line L21. The anode of diode D12 is connected to reference voltage line L22, and the cathode is connected to node N6. The anode of diode D13 is connected to node N7, and the cathode is connected to voltage line L21. The anode of diode D14 is connected to reference voltage line L22, and the cathode is connected to node N7. One end of capacitor Cout is connected to voltage line L21, and the other end is connected to reference voltage line L22. Transformer 20C corresponds to a specific example of the "first transformer" of this disclosure. Rectifier smoothing circuit 17C corresponds to a specific example of the "rectifier circuit" of this disclosure. Diodes D11 to D14 correspond to a specific example of the "multiple rectifier elements" of this disclosure.

[0110] Figure 10 This represents an example of an operation in power conversion system 1C. Figure 10 Corresponding to the above embodiments Figure 3 The power conversion system 1C is capable of performing the same operations as the power conversion system 1 described in the above-described embodiment.

[0111] [Other variations]

[0112] Alternatively, two or more of these variations can be combined.

[0113] <Second Implementation Method>

[0114] Next, the power conversion system 2 of the second embodiment will be described. Although two rods 11 and 12 were provided in the first embodiment, only one rod is provided in this embodiment as a replacement. Furthermore, the same reference numerals are used for structural parts that are substantially the same as those in the power conversion system 1 of the first embodiment, and their descriptions are appropriately omitted.

[0115] Figure 11 This represents a structural example of a power conversion system 2. The power conversion system 2 includes a DC power supply device PDC, a power conversion device 40, and a load device LD.

[0116] The power conversion device 40 is configured to convert electricity by stepping down the voltage (input voltage) supplied by the DC power supply device PDC, and then supply the converted electricity to the load device LD. The power conversion device 40 includes a rod 11, an inductor 13, and capacitors 15, 41, and 42. That is to say, although the power conversion device 10 of the first embodiment described above... Figure 1 The power conversion device 40 of this embodiment has two rods 11 and 12, but it has only one rod 11.

[0117] The lever 11 is disposed on the path connecting the voltage line L11 and the reference voltage line L12. The lever 11 has three transistors S1 to S3. The transistors S1 to S3 are configured to switch according to the gate signals G1 to G3 respectively. Each of the transistors S1 to S3 is configured in the same way as in the first embodiment described above, for example, using an N-type field-effect transistor.

[0118] Transistor S1 is configured such that it is positioned between voltage line L11 and node N1, and node N1 is connected to voltage line L11 by being turned on. The drain of transistor S1 is connected to voltage line L11, its gate is supplied with gate signal G1, and its source is connected to node N1. Transistor S2 is configured such that it is positioned between node N1 and node N2, and node N1 is connected to node N2 by being turned on. The drain of transistor S2 is connected to node N1, its gate is supplied with gate signal G2, and its source is connected to node N2. Transistor S3 is configured such that it is positioned between node N2 and reference voltage line L12, and node N2 is connected to reference voltage line L12 by being turned on. The drain of transistor S3 is connected to node N2, its gate is supplied with gate signal G3, and its source is connected to reference voltage line L12.

[0119] One end of inductor 13 is connected to node N2 of rod 11, and the other end is connected to node N5. One end of capacitor 15 is connected to node N5, and the other end is connected to reference voltage line L12.

[0120] One end of capacitor 41 is connected to voltage line L11, and the other end is connected to node N3. One end of capacitor 42 is connected to node N3, and the other end is connected to reference voltage line L12. Node N3 is the connection point between the other end of capacitor 41 and one end of capacitor 42.

[0121] One end of the resonant inductor Lr is connected to node N3, and the other end is connected to one end of the winding 21 of the transformer 20. One end of the resonant capacitor Cr is connected to node N1 of the rod 11, and the other end is connected to the other end of the winding 21 of the transformer 20.

[0122] The control circuit 49 is configured to control the operation of the power conversion device 40 by controlling the action of the control lever 11 based on the voltage Vout detected by the voltage sensor 18. Specifically, the control circuit 49 generates gate signals G1 to G3 based on the output voltage Vout, and uses these gate signals G1 to G3 to perform PWM control on the variation of the voltage (input voltage Vin) supplied by the DC power supply device PDC and PFM (Pulse Frequency Modulation) control on the variation of the load current, thereby controlling the operation of the power conversion device 40.

[0123] Here, lever 11 corresponds to a specific example of a "lever" in this disclosure. Transistor S1 corresponds to a specific example of a "first switching element" in this disclosure. Transistor S2 corresponds to a specific example of a "second switching element" in this disclosure. Transistor S3 corresponds to a specific example of a "third switching element" in this disclosure. Node N1 corresponds to a specific example of a "first node" in this disclosure. Node N2 corresponds to a specific example of a "second node" in this disclosure. Inductor 13 corresponds to a specific example of an "inductor" in this disclosure. Capacitor 15 corresponds to a specific example of a "first capacitor" in this disclosure. Node N5 corresponds to a specific example of a "third node" in this disclosure. Capacitor 41 corresponds to a specific example of a "second capacitor" in this disclosure. Capacitor 42 corresponds to a specific example of a "third capacitor" in this disclosure. Node N3 corresponds to a specific example of a "fourth node" in this disclosure. Transformer 20 corresponds to a specific example of a "transformer" in this disclosure. Control circuit 49 corresponds to a specific example of a "control circuit" in this disclosure.

[0124] Figure 12The following diagrams illustrate the detailed operation of the power conversion system 2: (A) the waveforms of gate signals G1 to G3; (B) the waveforms of the voltage at node N3 (AC voltage Vac) based on the voltage at node N1 and the waveforms of the current (AC current Iac) flowing from one end (node ​​N1 side) of the winding 21 of transformer 20 to the other end (node ​​N3 side); (C) the waveform of the current (inductor current IL13) flowing from node N5 through inductor 13 to node N2; and (D) the waveforms of the drain-source voltage Vds1 of transistor S1 and the waveforms of the main body of transistor S1. The waveforms of the drain-to-source current IS1 and the current ID1 flowing through the parasitic diode Dp of transistor S1 are shown in (E). The waveforms of the drain-to-source voltage Vds2 of transistor S2, the drain-to-source current IS2 of the main body of transistor S2, and the current ID2 flowing through the parasitic diode Dp of transistor S2 are shown in (F). The waveforms of the drain-to-source voltage Vds3 of transistor S3, the drain-to-source current IS3 of the main body of transistor S3, and the current ID3 flowing through the parasitic diode Dp of transistor S3 are shown in (F).

[0125] Figures 13A-13D This indicates the operation of the power conversion system 2 with four operating states ST11 to ST14.

[0126] During the period P11 starting from time t41, as Figure 12 As shown in (A), transistor S2 changes from the off state to the on state, transistor S3 changes from the on state to the off state, and transistor S1 remains on. During this period P11, the operating state ST first becomes the operating state ST11 ( Figure 13A ), and then becomes action state ST12 ( Figure 13B ).

[0127] In action state ST11 ( Figure 13A In the primary circuit, current I1 flows sequentially through reference voltage line L12, capacitor 15, node N5, inductor 13, node N2, transistor S2, and node N1. Current I2 flows sequentially through node N1, resonant capacitor Cr, winding 21 of transformer 20, resonant inductor Lr, and node N3. Current I3 flows sequentially through node N3, capacitor 41, voltage line L11, and then sequentially through node N3, capacitor 42, and reference voltage line L12. Current I4 flows sequentially through voltage line L11, transistor S1, and node N1.

[0128] In transistor S2, during the dead time Td, current flows through the parasitic diode Dp, the gate signal G2 changes from low to high, and then current flows through the body of transistor S2. Figure 12(A), (E)). In this way, transistor S2 can switch from the off state to the on state when the voltage between the drain and source is small, thus achieving so-called soft switching. As a result, efficiency can be improved in power conversion system 2.

[0129] like Figure 12 As shown in (E), the absolute value of current IS2 gradually decreases, and current IS2 changes from negative to positive. Therefore, from the operating state ST11 ( Figure 13A ) becomes action state ST12 ( Figure 13B ).

[0130] In operating state ST12, in the primary circuit, current I1 flows sequentially through node N1, transistor S2, node N2, inductor 13, node N5, capacitor 15, and reference voltage line L12. Current I2 flows sequentially through node N1, resonant capacitor Cr, winding 21 of transformer 20, resonant inductor Lr, and node N3. Current I3 flows sequentially through node N3, capacitor 41, voltage line L11, and then sequentially through node N3, capacitor 42, and reference voltage line L12. Current I4 flows sequentially through voltage line L11, transistor S1, and node N1. In other words, in operating state ST12, the direction of current I1 is reversed compared to operating state ST11.

[0131] During the period P12 starting from time t42, as Figure 12 As shown, transistor S3 changes from the off state to the on state, transistor S1 changes from the on state to the off state, and transistor S2 remains on. During this period, P12 changes the operating state ST to the operating state ST13. Figure 13C ).

[0132] In operating state ST13, in the primary circuit, current I1 flows sequentially through node N1, transistor S2, node N2, inductor 13, node N5, capacitor 15, and reference voltage line L12. Current I2 flows sequentially through node N3, resonant inductor Lr, winding 21 of transformer 20, resonant capacitor Cr, and node N1. Current I3 flows sequentially through reference voltage line L12, DC power supply device PDC, voltage line L11, capacitor 41, and node N3, and also sequentially through reference voltage line L12, capacitor 42, and node N3. Current I5 flows sequentially through reference voltage line L12, transistor S3, and node N2.

[0133] In transistor S3, during the dead time Td, current flows through the parasitic diode Dp, the gate signal G3 changes from low to high, and then current flows through the body of transistor S3. Figure 12(A), (F)). In this way, transistor S3 can switch from the off state to the on state when the voltage between the drain and source is small, thus achieving so-called soft switching. As a result, efficiency can be improved in power conversion system 2.

[0134] During the period P13 starting from time t43, as Figure 12 As shown, transistor S1 changes from the off state to the on state, transistor S2 changes from the on state to the off state, and transistor S3 remains on. During this period, P13, operating state ST becomes operating state ST14. Figure 13D ).

[0135] In operating state ST14, in the primary circuit, current I1 flows sequentially through reference voltage line L12, capacitor 15, node N5, inductor 13, node N2, transistor S3, and reference voltage line L12. Current I2 flows sequentially through node N3, resonant inductor Lr, winding 21 of transformer 20, resonant capacitor Cr, and node N1. Current I3 flows sequentially through voltage line L11, capacitor 41, node N3, and then sequentially through reference voltage line L12, capacitor 42, and node N3. Current I4 flows sequentially through node N1, transistor S1, and voltage line L11.

[0136] In transistor S1, during the dead time Td, current flows through the parasitic diode Dp, the gate signal G1 changes from low to high, and then current flows through the body of transistor S1. Figure 12 (A), (D)). In this way, transistor S1 can switch from the off state to the on state when the voltage between the drain and source is small, thus achieving so-called soft switching. As a result, efficiency can be improved in power conversion system 2.

[0137] The control circuit 49 controls the operation of transistors S1 and S2 by changing their duty cycles according to the output voltage Vout. Additionally, the control circuit 49 maintains the duty cycle of transistor S3 at approximately 50%.

[0138] When the control circuit 49 changes the duty cycle of transistors S1 and S2, it also changes the transition time of gate signal G1 from low to high and the transition time of gate signal G2 from high to low near time t43. Therefore, the power conversion system 2 differs from the first embodiment (…). Figure 2 Similarly, by changing the transition time of the AC voltage Vac near time t43, the duty cycle of the AC voltage Vac is changed. The duty cycle of the AC voltage Vac corresponds to the time of the switching period Tsw. Figure 12The time ratio of (B) to the positive time (the time of period P12). As a result, the power transferred from the primary circuit to the secondary circuit changes in the power conversion system 2. The control circuit 49 changes the duty cycle of transistors S1 and S2 according to the output voltage Vout, thereby controlling the operation of the power conversion system 2 so that the output voltage Vout remains constant when the input voltage Vin changes.

[0139] In power conversion system 2, as in this example, a rod 11, an inductor 13, and capacitors 15, 41, and 42 are provided. Rod 11 is positioned on the first path connecting input terminal T11 and input terminal T12, and includes transistors S1, S2, and S3. Transistor S1 is positioned between input terminal T11 and node N1, transistor S2 between node N1 and node N2, and transistor S3 between node N2 and input terminal T12. Inductor 13 is positioned between node N2 and node N5. Capacitor 15 is positioned between node N5 and input terminal T12. Capacitor 41 is positioned between input terminal T11 and node N3. Capacitor 42 is positioned between node N3 and input terminal T12. Thus, power conversion system 2, similar to the first embodiment, changes the duty cycle of the AC voltage Vac, thereby altering the power transmitted from the primary circuit to the secondary circuit.

[0140] Specifically, control circuit 49 can control the switching operation of transistors S1 to S3 according to the output voltage Vout, thereby changing the duty cycle of transistors S1 and S2 and maintaining the duty cycle of transistor S3. For example, control circuit 49... Figure 12 As shown, the duty cycles of transistors S1 and S2 are changed by altering the switching times of transistors S1 and S2 during the period when transistor S3 is in the on state. Therefore, for example, when the voltage (input voltage) supplied by the DC power supply device PDC is high, the output voltage Vout can be maintained by increasing the duty cycle of transistor S1 and decreasing the duty cycle of transistor S2. Conversely, for example, when the voltage (input voltage) supplied by the DC power supply device PDC is low, the output voltage Vout can be maintained by decreasing the duty cycle of transistor S1 and increasing the duty cycle of transistor S2. The duty cycles of transistors S1 and S2 are set in a range, for example, between 50% and 100%. Therefore, the input voltage range can be widened in the power conversion system 2.

[0141] Additionally, in power conversion system 2, such as Figure 12As shown in (A), during the period near time t41 when transistor S1 is in the on state, transistor S2 is turned on after a dead time Td elapsed from the time when transistor S3 is in the off state. Similarly, for example, during the period near time t42 when transistor S2 is in the on state, transistor S3 is turned on after a dead time Td elapsed from the time when transistor S1 is in the off state. Furthermore, during the period near time t43 when transistor S3 is in the on state, transistor S1 is turned on after a dead time Td elapsed from the time when transistor S2 is in the off state. Therefore, in the power conversion system 2, because transistors S1 to S3 can be soft-switched, efficiency can be improved.

[0142] Furthermore, in power conversion system 2, compared with power conversion system 1 in the first embodiment ( Figure 1 In contrast, the number of transistors can be reduced by reducing the number of links, thus simplifying the circuit.

[0143] As described above, in this embodiment, a lever 11, an inductor 13, and capacitors 15, 41, and 42 are provided. Lever 11 is disposed on a first path connecting input terminal T11 and input terminal T12, and includes transistors S1, S2, and S3. Transistor S1 is disposed between input terminal T11 and node N1, transistor S2 is disposed between node N1 and node N2, and transistor S3 is disposed between node N2 and input terminal T12. Inductor 13 is disposed between node N2 and node N5. Capacitor 15 is disposed between node N5 and input terminal T12. Capacitor 41 is disposed between input terminal T11 and node N3. Capacitor 42 is disposed between node N3 and input terminal T12. This widens the input voltage range.

[0144] In this embodiment, since the duty cycles of transistors S1 and S2 can be changed according to the output voltage while the duty cycle of transistor S3 is maintained, the input voltage range can be widened.

[0145] In this embodiment, since transistor S2 is turned on when transistor S3 is turned off after a predetermined time elapses while transistor S1 is in the on state, transistor S3 is turned on after a predetermined time elapses while transistor S2 is in the on state, and transistor S1 is turned on after a predetermined time elapses while transistor S1 is in the off state, efficiency can be improved.

[0146] [Variation Example 2]

[0147] The variations 1-2 of the first embodiment described above can also be applied to the power conversion system 2 of the above embodiment.

[0148] The present invention has been described above with examples of embodiments and variations, but the present invention is not limited to these embodiments and various changes can be made.

[0149] For example, in the above embodiment, although diodes DA and DB are used as rectifier elements in the rectifier smoothing circuit 17, it is not a limitation. As an alternative, transistors can also be used as rectifier elements. In this case, so-called synchronous rectification can be performed by switching the transistor.

Claims

1. A power conversion device, comprising: The first power terminal has a first wiring terminal and a second wiring terminal; A first rod is disposed on a first path connecting the first terminal and the second terminal, and has a first switching element, a second switching element and a third switching element. The first switching element is disposed between the first terminal and the first node, the second switching element is disposed between the first node and the second node, and the third switching element is disposed between the second node and the second terminal. The second rod is disposed on the second path connecting the first terminal and the second terminal, and has a fourth switch element, a fifth switch element and a sixth switch element. The fourth switch element is disposed between the first terminal and the third node, the fifth switch element is disposed between the third node and the fourth node, and the sixth switch element is disposed between the fourth node and the second terminal. The first inductor is disposed between the second node and the fifth node; A second inductor is disposed between the fourth node and the fifth node; A first capacitor is disposed between the fifth node and the second terminal; The first transformer has a first winding and a second winding, wherein the first winding is disposed on the path connecting the first node and the third node; The rectifier circuit has a plurality of rectifier elements connected to the second winding; The second power terminal is connected to the rectifier circuit and has a third terminal and a fourth terminal. as well as The control circuit controls the switching action between the first and second levers based on the voltage of the second power terminal.

2. The power conversion device according to claim 1, wherein, Furthermore, it incorporates resonant inductors and resonant capacitors. The resonant inductor and the resonant capacitor are disposed on the path connecting the first node and the third node.

3. The power conversion device according to claim 1 or claim 2, wherein, Equipped with a second transformer, The second transformer has a first winding and a second winding. The first winding of the second transformer includes the first inductor. The second winding of the second transformer includes the second inductor.

4. The power conversion device according to any one of claims 1 to 3, wherein, The control circuit controls the switching action according to the voltage of the second power terminal to change the first duty cycle of the first switching element, the second switching element, the fourth switching element and the fifth switching element, and maintain the second duty cycle of the third switching element and the sixth switching element.

5. The power conversion device according to claim 4, wherein, The control circuit turns on the third switching element during a first period, turns on the sixth switching element during a second period outside the first period, and changes the first duty cycle by changing the switching times of the first and second switching elements during the first period and the switching times of the fourth and fifth switching elements during the second period.

6. The power conversion device according to any one of claims 1 to 5, wherein, During the period when the second switching element is in the on state, the control circuit turns the third switching element on after a predetermined time has elapsed from the time when the first switching element is in the off state. During the period when the third switching element is in the ON state, the first switching element is turned ON at a time after a predetermined time has elapsed from the time when the second switching element is in the OFF state; and during the period when the first switching element is in the ON state, the second switching element is turned ON at a time after a predetermined time has elapsed from the time when the third switching element is in the OFF state.

7. A power conversion device, comprising: The first power terminal has a first wiring terminal and a second wiring terminal; A rod is disposed on the path connecting the first terminal and the second terminal, and has a first switching element, a second switching element and a third switching element. The first switching element is disposed between the first terminal and the first node, the second switching element is disposed between the first node and the second node, and the third switching element is disposed between the second node and the second terminal. An inductor is disposed between the second node and the third node; A first capacitor is disposed between the third node and the second terminal; The second capacitor is disposed between the first terminal and the fourth node; A third capacitor is disposed between the fourth node and the second terminal; A transformer has a first winding and a second winding, the first winding being disposed on the path connecting the first node and the fourth node; The rectifier circuit has a plurality of rectifier elements connected to the second winding; The second power terminal is connected to the rectifier circuit and has a third terminal and a fourth terminal. as well as The control circuit controls the switching action of the lever based on the voltage of the second power terminal.

8. The power conversion device according to claim 7, wherein, Furthermore, it incorporates resonant inductors and resonant capacitors. The resonant inductor and the resonant capacitor are disposed on the path connecting the first node and the fourth node.

9. The power conversion device according to claim 7 or claim 8, wherein, The control circuit controls the switching action according to the voltage of the second power terminal to change the first duty cycle of the first and second switching elements, and maintain the second duty cycle of the third switching element.

10. The power conversion device according to claim 9, wherein, The control circuit turns the third switching element on during the first period and changes the first duty cycle by changing the switching time of the first and second switching elements during the first period.

11. The power conversion device according to any one of claims 7 to 10, wherein, During the period when the first switching element is in the ON state, the control circuit turns the second switching element in the ON state after a predetermined time has elapsed since the time when the third switching element was turned off. During the period when the second switching element is in the ON state, the third switching element is turned ON after a predetermined time has elapsed since the time when the first switching element was turned OFF; and during the period when the third switching element is in the ON state, the first switching element is turned ON after a predetermined time has elapsed since the time when the second switching element was turned OFF.

12. A power conversion system, comprising: The power conversion device according to any one of claims 1 to 11; and A DC power supply device is connected to the first power terminal of the power conversion device.

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