JP7351281B2 - power converter - Google Patents

Description

The present invention relates to a power conversion device, and particularly to a circuit that converts an alternating current voltage to a direct current voltage and insulates an input and an output.

Conventionally, circuits that isolate input and output and convert AC voltage to DC voltage include a transformer, a rectifier circuit installed on the primary side of the transformer, an inverter circuit installed on the secondary side of the transformer, and a rectifier circuit installed on the primary side of the transformer. A power conversion device including a rectifier circuit is known (for example, Patent Document 1). In the power conversion device described in Patent Document 1, both rectifier circuits and the inverter circuit are each configured by a full bridge circuit. In this circuit, the input AC voltage is converted to DC voltage in the rectifier circuit, then converted to high-frequency AC voltage in the inverter circuit, applied to the transformer, isolated by the transformer, transmitted, and then returned to the rectifier circuit. converted to direct current.

JP2019-41428A

However, in the conventional technology, a total of three bridge circuits, two rectifier circuits and an inverter circuit, are used, so it is difficult to reduce the number of active elements. Here, the active element is a general term for switching elements and rectifying elements.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a power conversion device that can reduce the number of active elements compared to the case where a full bridge circuit is used.

A power conversion device that achieves the above object is a power conversion device that converts an AC voltage input from an AC power source into a DC voltage, and includes a transformer having a primary winding and a secondary winding, a first capacitor, a primary side circuit including a second capacitor, a pair of input terminals to which the AC power source is connected, a first inductor, an upper arm switching element, a lower arm switching element, an upper arm rectifying element, and a lower arm rectifying element; A rectifying and smoothing circuit having an inductor, a secondary rectifying element, an output capacitor, a first output terminal, and a second output terminal, the upper arm switching element and the lower arm switching element are connected in series, and the upper arm rectifying element and the lower arm switching element are connected in series. The series connection of the arm rectifier elements constitutes a bridge circuit, and the connection point between the upper arm switching element and the lower arm switching element and the connection point between the upper arm rectification element and the lower arm rectification element form a pair of input ends, The primary side circuit is connected to the primary winding of the transformer through the first capacitor, and the rectifier circuit is connected to the secondary winding of the transformer through the second capacitor.

According to this configuration, by switching the upper arm switching element and the lower arm switching element, the input and output are insulated by the transformer, and alternating current voltage is converted to direct current voltage. This allows the number of active elements to be reduced compared to when a full bridge circuit is used.

In the power converter, the rectifying and smoothing circuit has a first output terminal connected to one end of the output capacitor, a second output terminal connected to the other end of the output capacitor, and one end of the second inductor connected to the secondary side. The transformer is connected to one end of the output capacitor via the rectifying element, the other end of the second inductor is connected to the other end of the output capacitor, and the primary and secondary windings of the transformer are connected to the upper arm switching element. The secondary side rectifying element may be magnetically coupled so that it has a polarity that makes the secondary side rectifying element conductive when either one of the lower arm switching elements is in a non-conductive state.

In the power converter, the rectifying and smoothing circuit has a first output terminal connected to one end of the output capacitor, a second output terminal connected to the other end of the output capacitor, and one end of the secondary rectifying element connected to the first output terminal and one end of the output capacitor. 2, one end of the output capacitor is connected to the other end of the output capacitor via an inductor, and the other end of the secondary side rectifying element is connected to the other end of the output capacitor, and the primary and secondary windings of the transformer are connected to the upper arm switching element. The secondary side rectifying element may be magnetically coupled so that it has a polarity that makes the secondary side rectifying element conductive when either one of the lower arm switching element and the lower arm switching element is in a non-conductive state.

In the power converter, at least one of the upper arm rectifier, the lower arm rectifier, and the secondary rectifier may be configured by a switching element.
According to this configuration, conduction loss in the rectifying element can be reduced compared to the case where a diode is used.

In the above power conversion device, the switching element when any or all of the upper arm switching element, the lower arm switching element, the upper arm rectifying element, the lower arm rectifying element, and the secondary side rectifying element are composed of switching elements. The control unit may further include a control unit that controls switching of the element, and the control unit controls the switching so that the power factor of the input power is improved based on the AC voltage and the current flowing through the first inductor. good.

According to this configuration, the power factor of the power supplied from the AC power source can be controlled.
In the above power conversion device, the switching element when any or all of the upper arm switching element, the lower arm switching element, the upper arm rectifying element, the lower arm rectifying element, and the secondary side rectifying element are composed of switching elements. The device further includes a control unit that controls switching of the element, and the control unit controls the switching so that a predetermined DC voltage is output based on the voltage between the first output terminal and the second output terminal. There may be.

According to this configuration, the output voltage can be controlled to a desired value.

According to the present invention, it is possible to realize a power conversion device that insulates input and output and converts alternating current voltage to direct current voltage with fewer active elements than when using a full bridge circuit.

FIG. 3 is a diagram showing an example of the operation of the power conversion device 1 according to the first embodiment. FIG. 3 is a diagram showing an example of the operation of the power conversion device 1 according to the first embodiment. FIG. 3 is a diagram showing an example of the operation of the power conversion device 1 according to the first embodiment. FIG. 3 is a diagram showing an example of the operation of the power conversion device 1 according to the first embodiment. The figure which shows an example of operation of the power conversion device 1 based on 2nd Embodiment. The figure which shows an example of operation of the power conversion device 1 based on 2nd Embodiment. The figure which shows an example of operation of the power conversion device 1 based on 2nd Embodiment. The figure which shows an example of operation of the power conversion device 1 based on 2nd Embodiment. FIG. 3 is a diagram showing another example of the configuration of the power conversion device 1.

<First embodiment>
An embodiment of the present invention will be described below. The power converter 1 is a device that converts an AC voltage supplied from an AC power supply V1 into a DC voltage, and supplies the DC voltage to a load connected to the power converter 1.

The power conversion device 1 includes, for example, a primary circuit 10, a first capacitor 17, a transformer 18, a second capacitor 19, a rectifying and smoothing circuit 20, and a control unit 50.
The primary side circuit 10 includes, for example, a first inductor 11, an upper arm diode 12, a lower arm diode 13, an upper arm switching element 15, a lower arm switching element 16, a first connection line CL1, and a second connection. It includes a line CL2, a first intermediate line ML1, a second intermediate line ML2, a first input end t21, and a second input end t22. The upper arm diode 12 is an example of an "upper arm rectifier", and the lower arm diode 13 is an example of a "lower arm rectifier".

The AC power supply V1 and the primary circuit 10 are electrically connected. Specifically, the first end t11 of the AC power supply V1 and the first input end t21 of the primary circuit 10 are connected by the first input line L1. The second end t12 of the AC power supply V1 and the second input end t22 of the primary circuit 10 are connected by a second input line L2. As a result, AC voltage is input to the input terminals t21 and t22.

The upper arm diode 12 and the lower arm diode 13 are connected in series to each other by a second connection line CL2. Specifically, the second connection line CL2 connects the anode of the upper arm diode 12 and the cathode of the lower arm diode 13.

The upper arm switching element 15 has a first end t31 and a second end t32, and the lower arm switching element 16 has a first end t41 and a second end t42. The first connection line CL1 connects the second end t32 of the upper arm switching element 15 and the first end t41 of the lower arm switching element 16.

The first intermediate line ML1 connects the first connection line CL1 and the first input end t21. A first inductor 11 is provided on the first intermediate line ML1. The second intermediate line ML2 connects the second connection line CL2 and the second input end t22. Therefore, the connection point between the upper arm switching element 15 and the lower arm switching element 16 (that is, the point on the first connection line CL1) and the connection point between the upper arm diode 12 and the lower arm diode 13 (that is, the point on the second connection line CL1) A point on CL2) is connected to a pair of input ends (input ends t21, t22) via the first inductor 11.

The cathode of the upper arm diode 12 and the first end t31 of the upper arm switching element 15 are connected, and the anode of the lower arm diode 13 and the second end t42 of the lower arm switching element 16 are connected. Therefore, the series connection of the upper arm switching element 15 and the lower arm switching element 16 and the series connection of the upper arm diode 12 and the lower arm diode 13 constitute the half bridge circuit 14.

The transformer 18 is an isolation transformer having a primary winding W1 and a secondary winding W2. The starting end of the primary winding W1 (the side marked with a black circle in FIG. 1) is electrically connected to the cathode of the upper arm diode 12 and the first end t31 of the upper arm switching element 15 via the first capacitor 17. Connected. Specifically, the first capacitor 17 has a first end t51 and a second end t52, and the starting end of the primary winding W1 is connected to the second end t52 of the first capacitor 17. A first end t51 of the capacitor 17 is connected to the cathode of the upper arm diode 12 and a first end t31 of the upper arm switching element 15. The terminal end of the primary winding W1 (the side not marked with a black circle in FIG. 1) is connected to the anode of the lower arm diode 13 and the second end t42 of the lower arm switching element 16. Therefore, the primary circuit 10 is connected to the primary winding W1 of the transformer 18 via the first capacitor 17.

The rectifying and smoothing circuit 20 includes a second inductor 21, a secondary diode 22, an output capacitor 23, a first output line OL1, a second output line OL2, a first output terminal t91, and a second output terminal t92. Equipped with. The second inductor 21 has a first end t71 and a second end t72, and the output capacitor 23 has a first end t81 and a second end t82. The secondary diode 22 is an example of a "secondary rectifying element." Further, the first end t81 is an example of "one end of the output capacitor", and the second end t82 is an example of "the other end of the output capacitor".

The starting end of the secondary winding W2 (the side marked with a black circle in FIG. 1) is electrically connected to the first end t71 of the second inductor 21 and the anode of the secondary diode 22 via the second capacitor 19. connected to. Specifically, the second capacitor 19 has a first end t61 and a second end t62, and the starting end of the secondary winding W2 is connected to the first end t61 of the second capacitor 19, The second end t62 of the second capacitor 19 is connected to the first end t71 of the second inductor 21 and the anode of the secondary diode 22. The terminal end of the secondary winding W2 (the side not marked with a black circle in FIG. 1) is connected to the second end t72 of the second inductor 21. Therefore, the rectifying and smoothing circuit 20 is connected to the secondary winding W2 of the transformer 18 via the second capacitor 19.

The output capacitor 23 is connected to both the first output line OL1 and the second output line OL2. Specifically, the first end t81 of the output capacitor 23 is connected to the first output line OL1. The second end t82 of the output capacitor 23 is connected to the second output line OL2.

The second inductor 21 is connected to both the first output line OL1 and the second output line OL2. Specifically, the first end t71 of the second inductor 21 is connected to the first output line OL1, and the second end t72 of the second inductor 21 is connected to the second output line OL2. The first end t71 is an example of "one end of the second inductor", and the second end t72 is an example of "the other end of the second inductor".

The secondary diode 22 is provided on the first output line OL1 between the second inductor 21 and the output capacitor 23. Specifically, the secondary diode 22 is provided at a portion between the connection point of the second inductor 21 and the connection point of the output capacitor 23 on the first output line OL1. As described above, the anode of the secondary diode 22 and the first end t71 of the second inductor 21 are connected. Furthermore, the cathode of the secondary diode 22 and the first end t81 of the output capacitor 23 are connected.

As shown in FIG. 1, the power conversion device 1 includes a current sensor C1 that detects the current flowing through the first inductor 11. The power converter 1 also includes a voltage sensor C2 that detects input voltage and a voltage sensor C3 that detects output voltage. Current sensor C1, voltage sensor C2, and voltage sensor C3 output their detection results to control section 50.

The control unit 50 turns on/off the upper arm switching element 15 and the lower arm switching element 16 based on signals from the current sensor C1, voltage sensor C2, and voltage sensor C3. The power conversion device 1 converts the AC voltage supplied by the AC power supply V1 into a DC voltage by turning on/off the upper arm switching element 15 and the lower arm switching element 16, and converts the DC voltage to both output terminals t91, Output from t92.

The details of the operation of the power conversion device 1 will be described below with reference to FIGS. 1 to 4. For convenience of explanation, it is assumed that each of the capacitors 17, 19, and 23 is charged at the timing when the power conversion device 1 starts operating.

First, switching control in a state where the potential at the first end t11 of the AC power supply V1 is higher than the potential at the second end t12 will be described with reference to FIGS. 1 and 2.
In this state, the control unit 50 changes the switching pattern of both switching elements 15 and 16 to a first state in which both switching elements 15 and 16 are in the ON state, and a first state in which the upper arm switching element 15 is in the ON state and the lower arm switching element 15 is in the ON state. The arm switching element 16 is alternately switched to the second state in which it is in the OFF state.

A current path when the switching pattern is in the first state will be described. As shown in FIG. 1, when the switching pattern is in the first state, there is a path rt11 associated with the supply of power from the AC power source V1, a path rt12 associated with the discharging of the first capacitor 17, and a path rt12 associated with the discharge of the first capacitor 17, and a Current flows through the path rt21 due to electromagnetic induction to the winding W2 and the discharge of the second capacitor 19, and the path rt22 due to the discharge of the output capacitor 23.

The route rt11 is a route from the first end t11 of the AC power supply V1 to the second end t12 of the AC power supply V1 via the first inductor 11, the lower arm switching element 16, and the lower arm diode 13. When the switching pattern is in the first state, the current flowing through the path rt11 increases over time, and the magnetic flux of the first inductor 11 also increases as the current increases.

The path rt12 is from the first end t51 of the first capacitor 17 to the second end t52 of the first capacitor 17 via the upper arm switching element 15, the lower arm switching element 16, and the end and start end of the primary winding W1. This is the route. The voltage across the first capacitor 17 is applied to the primary winding W1 of the transformer 18, and the potential at the end of the primary winding W1 becomes higher than the potential at the start end. As a result, a voltage is generated at both ends of the secondary winding W2 of the transformer 18 such that the potential at the end is higher than the potential at the start end.

The route rt21 is a route from the terminal end of the secondary winding W2 to the starting end of the secondary winding W2 via the second inductor 21 and the second capacitor 19. When the switching pattern is in the first state, the current flowing through the path rt21 increases over time, and the magnetic flux of the second inductor 21 also increases as the current increases.

The route rt22 is from the first end t81 of the output capacitor 23 to the second end t82 of the output capacitor 23 via the first output end t91, the load connected to the power converter 1, and the second output end t92. It is a route. A DC voltage, which is the voltage across the output capacitor 23, is generated between the first output terminal t91 and the second output terminal t92. When the switching pattern is in the first state, the secondary diode 22 is not in a conductive state.

On the other hand, as shown in FIG. 2, when the switching pattern is in the second state, current flows through the path rt13 and the path rt23.
The path rt13 is the AC power supply from the first end t11 of the AC power supply V1, via the first inductor 11, the upper arm switching element 15, the first capacitor 17, the starting end to the end of the primary winding W1, and the lower arm diode 13. This is the route to the second end t12 of V1. The first capacitor 17 is charged by the current flowing through the path rt13. On the other hand, the magnetic flux of the first inductor 11 decreases. Further, a voltage is applied to the primary winding W1 of the transformer 18 such that the potential at the starting end is higher than the potential at the ending end. As a result, a voltage is generated in the winding W2 of the transformer 18 such that the potential at the starting end is higher than the potential at the ending end.

Route rt23 includes two routes. One is the second inductor that passes from the first end t71 of the second inductor 21 to the secondary diode 22, the first output end t91, the load connected to the power converter 1, and the second output end t92. 21 to the second end t72. The other is from the starting end of the secondary winding W2 through the second capacitor 19, the secondary side diode 22, the first output terminal t91, the load connected to the power converter 1, and the second output terminal t92. , is the path to the end of the secondary winding W2. At this time, the magnetic flux of the second inductor 21 decreases. Furthermore, in the second state of the switching pattern, the secondary diode 22 is conductive. That is, when the upper arm switching element 15 is in a conductive state and the lower arm switching element 16 is in a non-conductive state, the primary winding W1 and the secondary winding W2 of the transformer 18 are polarized so that the secondary side diode 22 is conductive. Magnetically coupled.

Next, switching control in a state where the potential of the second end t12 of the AC power supply V1 is higher than the potential of the first end t11 will be described using FIGS. 3 and 4.
In this state, the control unit 50 changes the switching pattern of both switching elements 15 and 16 into a first state in which both switching elements 15 and 16 are in the ON state, and a first state in which the upper arm switching element 15 is in the OFF state and the lower arm switching element 15 is in the OFF state. The arm switching element 16 is alternately switched to the third state in which it is in the ON state.

As shown in FIG. 3, when the switching pattern is in the first state, there is a path rt14 associated with the supply of power from the AC power source V1, a path rt12 associated with the discharge of the first capacitor 17, and a path rt12 associated with the discharge of the second capacitor 19. A current flows through the path rt21 associated with the discharge of the output capacitor 23 and the path rt22 associated with the discharge of the output capacitor 23. The route rt12, the route rt21, and the route rt22 have already been described, so a detailed explanation will be omitted.

The route rt14 is a route from the second end t12 of the AC power supply V1 to the first end t11 via the upper arm diode 12, the upper arm switching element 15, and the first inductor 11. The current in the path rt14 increases over time, and the magnetic flux of the first inductor 11 increases as the current increases.

As shown in FIG. 4, when the switching pattern is in the third state, current flows through the path rt15 and the path rt23 due to the supply of power from the AC power source V1. At this time, the secondary diode 22 on the path rt23 is conductive. That is, when the upper arm switching element 15 is in a non-conductive state and the lower arm switching element 16 is in a conductive state, the primary winding W1 and the secondary winding W2 of the transformer 18 are polarized so that the secondary side diode 22 is conductive. Magnetically coupled. The route rt23 is the same as when the switching pattern is in the first state, so a description thereof will be omitted.

The path rt15 is a first path from the second end t12 of the AC power supply V1, via the upper arm diode 12, the first capacitor 17, the starting end to the end of the primary winding W1, the lower arm switching element 16, and the first inductor 11. This is the route to end t11. As the current flows through the path rt15, the first capacitor 17 is charged, while the magnetic flux of the first inductor 11 decreases.

As described above, when the potential of the first input terminal t21 is higher than the potential of the second input terminal t22, the control unit 50 alternately switches the switching pattern between the first state and the second state, and When the potential at the end t22 is higher than the potential at the first input end t21, the switching pattern is alternately switched between the first state and the third state. Thereby, power conversion is performed in the power conversion device 1.

Specifically, the switching pattern repeats the first state and the second state or repeats the first state and the third state depending on the polarity of the AC voltage V1, so that the second terminal of the lower arm switching element 16 The potential at the first end t31 of the upper arm switching element 15 is always higher than the potential at t42. That is, the half-bridge circuit 14 including the upper arm switching element 15, the lower arm switching element 16, the upper arm rectifying element 12, and the lower arm rectifying element 13 converts the AC voltage V1 into a DC voltage.

In the second state or the third state, the starting end of the first winding W1 has a higher potential than the ending end of the first winding W1. Also, at this time, the first capacitor 17 is charged by the current flowing through the first inductor 11 . Furthermore, at this time, the secondary rectifying element 22 becomes conductive, and current flows from the second winding W2 of the transformer 18 through the second capacitor 19 and the secondary rectifying element 22 to the load. Therefore, the current flowing through the first inductor 11 is supplied to the load via the transformer 18.

In the first state of the switching pattern, the voltage across the first capacitor 17 is applied to the first winding W1 of the transformer 18. At this time, the potential at the end of the first winding W1 becomes higher than the potential at the start end of the first winding W1. Further, at this time, current flows from the second winding W2 of the transformer 18 to the second inductor 21 and the second capacitor 19, and is stored as electromagnetic energy and electrostatic energy, respectively. The energy stored in the second inductor 21 and the second capacitor 19 in the first state is supplied to the load in the second or third state. Therefore, in the first state, the current from the first capacitor supplies current to the load via the second inductor 21 and energy storage in the second capacitor 19 . Even in the first state, the second state, or the third state, energy is transferred from the primary side to the secondary side of the transformer 18, so the utilization efficiency of the transformer 18 is high.

In particular, in this embodiment, the control unit 50 can control switching based on the current flowing through the first inductor 11 and the input voltage so that the power factor of the input power is improved. For example, the control unit 50 controls the upper arm rectifying element 12, the lower arm rectifying element 13, and the half bridge circuit 14 by controlling the first state time of the upper arm switching element 15 and the lower arm switching element 16. It operates as a power factor correction (PFC) circuit. In the switching pattern of the first state, the AC power source V1 and the first inductor 11 form a closed circuit, and the current from the AC power source V1 is limited by the first inductor 11. Since the increase in the current flowing through the first inductor is proportional to the time for which the switching pattern in the first state is continued, the current in the first inductor 11 is controlled by controlling the time for which the switching pattern in the first state is continued. It becomes possible to do so. The control unit 50 controls the current sensor C1 and the voltage sensor C2 so that the waveform of the current flowing through the first inductor 11 becomes approximately sinusoidal, and the frequency and phase of the sine wave match the frequency and phase of the AC power supply V1. The duration of the switching pattern in the first state is controlled based on the signal from the first state.

Further, the control unit 50 can also perform switching control so that a predetermined DC voltage is output based on the detection result of the voltage sensor C3. In detail, the control unit 50 controls the duty ratio of both the switching elements 15 and 16, for example, based on the difference between the output voltage detected by the voltage sensor C3 and a predetermined DC voltage (target voltage). Further, the control unit 50 can improve the power factor of input power and control the output voltage at the same time.

According to the above embodiment, the following effects can be obtained.
(1-1) The power conversion device 1 switches the switching pattern to repeat the first state and the second state or repeat the first state and the third state depending on the polarity of the AC voltage V1. Thereby, the half bridge circuit 14 converts the AC voltage V1 into a DC voltage.

At the same time, a high frequency alternating current voltage is applied to the primary winding W1 of the transformer 18 by the switching operation of the upper arm switching element 15 and the lower arm switching element 16. Thereby, power is transmitted to the secondary side of the transformer 18 through the transformer 18 while being insulated.

In conventional circuits, separate bridge circuits perform conversion from AC voltage to DC voltage and conversion from the converted DC voltage to high-frequency AC voltage. On the other hand, in the power conversion device 1 of this embodiment, a single bridge circuit performs conversion from alternating current to direct current and conversion from converted direct current to high-frequency alternating current.

Thereby, the power conversion device 1 of this embodiment can reduce the number of active elements such as switching elements and rectifying elements, compared to a case where a full bridge circuit is used like a conventional circuit. In addition, the power conversion device 1 of this embodiment has fewer active elements through which current passes than when using a full-bridge circuit like the conventional circuit, so that conduction loss in the active elements is reduced. be able to.

(1-2) The transformer 18 operates from the primary side to the secondary side in all of the first to third states of the switching pattern, regardless of the direction of the voltage applied to the starting and ending ends of the primary winding W1 of the transformer 18. Transfer power to the side. Therefore, the power conversion device 1 can increase the utilization efficiency of the transformer 18.

(1-3) The power conversion device 1 further includes a control unit 50 that controls switching of the upper arm switching element 15 and the lower arm switching element 16. The control unit 50 controls switching based on the current flowing through the first inductor 11 and the input voltage from the AC power supply V1 so that the power factor is improved.

According to this configuration, the power conversion device 1 can improve the power factor of the power supplied from the AC power source V1.
(1-4) The control unit 50 controls the upper arm switching element 15 and the lower arm so that a predetermined DC voltage is output based on the voltage between the first output terminal t91 and the second output terminal t92. Controls switching of the switching element 16.

According to this configuration, the power converter 1 performs feedback control based on the voltage between the first output terminal t91 and the second output terminal t92, and adjusts the DC voltage output by the power converter 1 to a predetermined DC voltage. (target voltage).

<Second embodiment>
A second embodiment will be described below with reference to the drawings. The second embodiment differs from the first embodiment in that the power conversion device 2 includes a rectification and smoothing circuit 30 instead of the rectification and smoothing circuit 20. Note that the same configurations as those in the first embodiment are given the same reference numerals and the description thereof will be omitted.

As shown in FIG. 5, the power conversion device 2 includes a primary circuit 10, a first capacitor 17, a transformer 18, a second capacitor 19, and a rectifying and smoothing circuit 30.
The rectifying and smoothing circuit 30 includes a second inductor 21, a secondary diode 22, an output capacitor 23, a first output line OL1, a second output line OL2, a first output terminal t91, and a second output terminal t92. Equipped with.

The terminal end of the secondary winding W2 is electrically connected to the first end t71 of the second inductor 21 and the cathode of the secondary diode 22 via the second capacitor 19. Specifically, the terminal end of the secondary winding W2 is connected to the first end t61 of the second capacitor 19, and the second end t62 of the second capacitor 19 is connected to the first end t71 of the second inductor 21. It is connected to the cathode of the next diode 22. A starting end of the secondary winding W2 is connected to the anode of the secondary diode 22 and the second output line OL2. In this embodiment, the cathode of the secondary diode 22 is an example of "one end of the secondary rectifying element," and the anode of the secondary diode 22 is an example of "the other end of the secondary rectifying element." be.

The output capacitor 23 is connected to both the first output line OL1 and the second output line OL2. Specifically, the first end t81 of the output capacitor 23 is connected to the first output line OL1 (specifically, between the connection point of the first output line OL1 with the secondary side diode 22 and the first output end t91). part). The second end t82 of the output capacitor 23 is connected to the second output line OL2 (specifically, the part between the connection point of the second output line OL2 with the secondary side diode 22 and the second output end t92). It is connected.

The second end t72 of the second inductor 21 is connected to the first output line OL1. As described above, the first end t71 of the second inductor 21 and the cathode of the secondary diode 22 are connected. Further, the second end t72 of the second inductor 21 and the first end t81 of the output capacitor 23 are connected. Therefore, the rectifying and smoothing circuit 30 is connected to the secondary winding W2 of the transformer 18 via the second capacitor 19.

The details of the operation of the power conversion device 2 will be described below with reference to FIGS. 5 to 8. FIG. 5 shows a current path when the switching pattern is in the first state in a state where the potential of the first end t11 is higher than the potential of the second end t12 in the AC power source V1, and FIG. The current path is shown when the switching pattern is in the second state in a state where the potential of the first end t11 is higher than the potential of the second end t12. FIG. 7 shows a current path when the switching pattern is in the first state in a state where the potential of the second end t12 is higher than the potential of the first end t11 in the AC power source V1, and FIG. The current path is shown when the switching pattern is in the third state in a state where the potential of the second end t12 is higher than the potential of the first end t11.

First, switching control when the voltage at the first end t11 of the AC power supply V1 is higher than the voltage at the second end t12 will be described with reference to FIGS. 5 and 6. In this state, the control unit 50 changes the switching patterns of both switching elements 15 and 16 into a first state in which both the upper arm switching element 15 and the lower arm switching element 16 are in the ON state, and a first state in which the upper arm switching element 15 is in the ON state. and a second state in which the lower arm switching element 16 is in the OFF state.

A current path when the switching pattern is in the first state will be described. As shown in FIG. 5, when the switching pattern is in the first state, there is a path rt11 associated with the supply of power from the AC power supply V1, a path rt12 associated with the discharge of the first capacitor 17, and a route rt12 associated with the discharge of the second capacitor 19. A current flows along the accompanying path rt31. Since the route rt11 and the route rt12 have already been explained, detailed explanation will be omitted.

The path rt31 is a load connected from the terminal end of the transformer 18 to the first end t61 of the second capacitor 19, the second end t62 of the second capacitor 19, the second inductor 21, the first output end t91, and the power converter 2. , which is a route to the starting end of the secondary winding W2 via the second output end t92. When the switching pattern is in the first state, the current flowing through the second inductor 21 increases over time, and the magnetic flux of the second inductor 21 increases as the current increases.

On the other hand, as shown in FIG. 6, when the switching pattern is in the second state, current flows through the path rt13, the path rt32, and the path rt33. Since the route rt13 has already been explained, its explanation will be omitted.

The route rt32 is a route from the starting end of the secondary winding W2 to the terminal end of the secondary winding W2 via the secondary side diode 22 and the second capacitor 19. Therefore, the primary winding W1 and the secondary winding W2 of the transformer 18 have polarities such that the secondary diode 22 is conductive when either the upper arm switching element 15 or the lower arm switching element 16 is in a non-conductive state. They are magnetically coupled.

The path rt33 is from the second end t72 of the second inductor 21 to the second inductor via the first output end t91, the load connected to the power converter 2, the second output end t92, and the secondary side diode 22. 21 to the first end t71. In this state, the magnetic flux of the second inductor 21 decreases.

Next, switching control in the second state in which the voltage at the second end t12 of the AC power supply V1 is higher than the voltage at the first end t11 will be described using FIGS. 7 and 8.
Similarly to the first embodiment, the control unit 50 sets the switching pattern of both switching elements 15 and 16 to a first state and a second state in which the upper arm switching element 15 is in the OFF state and the lower arm switching element 16 is in the ON state. Switch alternately to 3 states.

As shown in FIG. 7, when the switching pattern is in the first state in this state, current flows through the path rt14, the path rt12, and the path rt31. The route rt12, route rt14, and route rt31 have already been described, so detailed explanations will be omitted.

As shown in FIG. 8, when the switching pattern is in the third state, current flows through path rt15, path rt32, and path rt33. The route rt15, the route rt32, and the route rt33 have already been described, so detailed explanations will be omitted.

As described above, when the voltage at the first end t11 of the AC power supply V1 is higher than the voltage at the second end t12, the control unit 50 alternately switches the switching pattern between the first state and the second state, When the voltage at the second end t12 of the power supply V1 is higher than the voltage at the first end t11, the switching pattern is alternately switched between the first state and the third state. Thereby, power conversion is performed in the power conversion device 2.

According to the above embodiment, in addition to the same effects as the first embodiment, the following effects can be obtained.
(2-1) According to the power converter 2 of the present embodiment, the second inductor 21 , current is supplied to the load. Therefore, the power conversion device 2 can reduce the ripple current of the output capacitor 23.

Each of the above embodiments may be modified as follows. Note that the above embodiment and the following examples may be combined with each other within a technically consistent range.
In each of the embodiments described above, diodes are used as the upper arm rectifying element 12 and the lower arm rectifying element 13, but the present invention is not limited to this, and switching elements may be used instead of the diodes. In this case, so-called synchronous rectification control is performed in which the switching elements are turned on at the timing when the upper arm rectifying element 12 and the lower arm rectifying element 13 become conductive. By using a switching element instead of a diode, conduction loss can be reduced.

In the above description, the rectifying and smoothing circuit 20 and the rectifying and smoothing circuit 30 are provided with the secondary diode 22 as the secondary rectifying element, but the present invention is not limited to this. The rectifying and smoothing circuit 20 and the rectifying and smoothing circuit 30 may have a switching element instead of the secondary diode 22. FIG. 9 is a diagram showing the power converter 1 in which a switching element is used in place of the upper arm rectifying element 12 and the lower arm rectifying element 13, and a switching element 22 is used in place of the secondary side diode 22. In this case, so-called synchronous rectification control is performed in which the switching element is turned on in a state of a switching pattern in which the secondary side diode 22 is conductive. By using the switching element 22 instead of the secondary diode 22, conduction loss can be reduced.

- In each of the above embodiments, the first inductor 11 is connected between the first input end t21 and the first connection line CL1, but the position of the first inductor 11 is not limited to this, and the position is connected between the second input end t22 and the first inductor 11. and the second connection line CL2. Further, assuming that the first inductor 11 is two inductors, it is connected both between the first input terminal t21 and the first connection line CL1 and between the second input terminal t22 and the second connection line CL2. Good too.

In each of the embodiments described above, the first capacitor 17 was connected between the first end t31 of the upper arm switching element 15 and the starting end of the primary winding W1, but the position of the first capacitor 17 is not limited to this. Instead, it may be connected between the second end t42 of the lower arm switching element 16 and the terminal end of the primary winding W2. Further, the first capacitor 17 may be constituted by two capacitors, and in this case, one is connected between the first end t31 of the upper arm switching element 15 and the starting end of the primary winding W1, and the other is the second end of the lower arm switching element. t42 and the terminal end of the primary winding W2.

In the first embodiment described above, the second capacitor 19 was connected between the starting end of the secondary winding W2 and the anode of the secondary diode 22, but the position of the second capacitor 19 is limited to this. Instead, it may be connected between the terminal end of the secondary winding W2 and the second end t72 of the second inductor. Further, the second capacitor 19 may be constituted by two capacitors, and in this case, one is connected between the starting end of the secondary winding W2 and the anode of the secondary side diode 22, and the other is between the end of the secondary winding W2 and the anode of the secondary side diode 22. 2 and the second end t72 of the inductor.

In the second embodiment described above, the second capacitor 19 was connected between the starting end of the secondary winding W2 and the cathode of the secondary diode 22, but the position of the second capacitor is limited to this. Instead, it may be connected between the terminal end of the secondary winding W2 and the anode of the secondary diode 22. Further, the second capacitor 19 may be composed of two capacitors, and in this case, one is connected between the starting end of the secondary winding W2 and the cathode of the secondary side diode 22, and the other is between the end of the secondary winding W2 and the secondary side diode 22. and the cathode of the side diode 22.

The current sensor C1 may be provided not on the first intermediate line ML1 but on the second intermediate line ML2.

DESCRIPTION OF SYMBOLS 1, 2...Power converter, 10...Primary side circuit, 11...First inductor, 12...Upper arm diode, 13...Lower arm diode, 14...Half bridge circuit, 15...Upper arm switching element, 16...Lower arm switching Element, 17... First capacitor, 18, 18a, 18b... Transformer, 19... Second capacitor, 20, 30... Rectifying and smoothing circuit, 21... Second inductor, 22... Secondary side diode, 23... Output capacitor, 50... Control unit, C1... Current sensor, C2... Voltage sensor, CL1... First connection line, CL2... Second connection line, L1... First input line, L2... Second input line, ML1... First intermediate line, ML2... Second intermediate line, OL1...first output line, OL2...second output line, t21...first input terminal, t22...second input terminal, t91...first output terminal, t92...second output terminal, V1...AC Power supply, W1...primary winding, W2...secondary winding.

Claims (6)

A power conversion device that converts AC voltage input from an AC power source into DC voltage,
A transformer having a primary winding and a secondary winding;
a first capacitor;
a second capacitor;
a primary side circuit having a pair of input ends to which the AC power source is connected, a first inductor, an upper arm switching element, a lower arm switching element, an upper arm rectifying element, and a lower arm rectifying element;
a rectifying and smoothing circuit having a second inductor, a secondary rectifying element, an output capacitor, a first output terminal and a second output terminal;
A power conversion device comprising:
The series connection of the upper arm switching element and the lower arm switching element and the series connection of the upper arm rectifying element and the lower arm rectifying element constitute a half bridge circuit, and the upper arm switching element and the lower arm switching element constitute a half bridge circuit. A connection point with the element and a connection point between the upper arm rectifying element and the lower arm rectifying element are connected to the pair of input ends via the first inductor,
The primary side circuit is connected to the primary winding of the transformer via the first capacitor,
The rectifying and smoothing circuit is connected to a secondary winding of the transformer via the second capacitor.
Power converter. The rectifying and smoothing circuit is
the first output terminal and one end of the output capacitor are connected,
the second output terminal and the other end of the output capacitor are connected,
One end of the second inductor is connected to one end of the output capacitor via the secondary rectifying element, and the other end of the second inductor is connected to the other end of the output capacitor,
The primary winding and the secondary winding of the transformer are magnetically polarized so that the secondary rectifying element is conductive when either the upper arm switching element or the lower arm switching element is in a non-conducting state. are combined,
The power conversion device according to claim 1. The rectifying and smoothing circuit is
the first output terminal and one end of the output capacitor are connected,
the second output terminal and the other end of the output capacitor are connected,
One end of the secondary rectifying element is connected to one end of the output capacitor via the second inductor, and the other end of the secondary rectifying element is connected to the other end of the output capacitor,
The primary winding and the secondary winding of the transformer are magnetically polarized so that the secondary rectifying element is conductive when either the upper arm switching element or the lower arm switching element is in a non-conducting state. are combined,
The power conversion device according to claim 1. At least one of the upper arm rectifier, the lower arm rectifier, and the secondary rectifier is configured by a switching element.
The power conversion device according to any one of claims 1 to 3. The upper arm switching element, the lower arm switching element, and any or all of the upper arm rectifying element, the lower arm rectifying element, and the secondary rectifying element are configured of switching elements. further comprising a control section for controlling switching of the
The control unit controls switching based on the AC voltage and the current flowing through the first inductor so that the power factor of input power is improved.
The power conversion device according to any one of claims 1 to 4. In the case where any or all of the upper arm switching element, the lower arm switching element, the upper arm rectifying element, the lower arm rectifying element, and the secondary side rectifying element are composed of switching elements, the switching element further comprising a control unit that controls switching of the element,
The control unit controls switching so that a predetermined DC voltage is output based on the voltage between the first output terminal and the second output terminal.
The power conversion device according to any one of claims 1 to 4.