WO2025210370A1 - Power conversion device - Google Patents

Abstract

A power conversion device (1) is provided with an inverter circuit (10) and a rectifier circuit (20). The inverter circuit (10) converts the power input to a pair of input terminals (lt1, lt2) and outputs the converted power. The rectifier circuit (20) includes a diode (D) connected to a pair of output terminals (Ot1, Ot2). The rectifier circuit (20) rectifies the output power of the inverter circuit (10) and outputs the rectified power to the pair of output terminals (Ot1, Ot2). The power conversion device (1) is provided with first and second coolers (30c, 30a). The first cooler (30c) is connected to the cathode terminal side of the diode (D) and cools the diode (D). The second cooler (30a) is connected to the anode terminal side of the diode (D) and cools the diode (D). The first and second coolers (30c, 30a) are connected to the ground potential, respectively.

Description

Power Conversion Device

The present invention relates to a power conversion device.

Patent Document 1 discloses a power conversion device. In the power conversion device, a noise eliminator, which is made of a conductor covered with an insulator, is provided between a switching element and a heat sink. A flexible connection line connected to the conductor of the noise eliminator is connected to an on-board line that is wired on a board. By providing the noise eliminator, it is possible to balance the parasitic capacitance of the line on the high-potential side and the parasitic capacitance of the line on the low-potential side, preventing generated common mode noise from flowing to the line side and leaking to the external ground line connected to the heat sink.

JP 2017-17841 A

The method disclosed in Patent Document 1 has the problem that parasitic capacitance exists between the rectifier elements that make up the rectifier circuit and the heat sink, and this parasitic capacitance between the rectifier elements and the heat sink causes common mode noise to flow into the heat sink, resulting in common mode noise leaking to the outside.

The object of the present invention is to propose a power conversion device that can suppress the leakage of common-mode noise to the outside.

A power conversion device according to one aspect of the present invention includes an inverter circuit that converts power input to a pair of input terminals and outputs the converted power, a rectifier circuit that rectifies the output power of the inverter circuit and outputs the rectified power to a pair of output terminals, a first cooler connected to the cathode terminal side of a diode included in the rectifier circuit, and a second cooler connected to the anode terminal side of the diode. The first cooler and second cooler are each connected to ground potential.

According to one aspect of the present invention, it is possible to prevent common-mode noise from leaking to the outside.

FIG. 1 is a diagram schematically illustrating the configuration of a power conversion device according to the first embodiment. FIG. 2 is a diagram showing a connection state between the cathode terminal of the diode and the first cooler. FIG. 3 is a diagram showing a connection state between the cathode terminal of the diode and the first cooler. FIG. 4 is a diagram showing the transition of the common mode current. FIG. 5 is a diagram schematically illustrating the configuration of a power conversion device according to the second embodiment. FIG. 6 is a diagram illustrating another example of a power conversion device according to the second embodiment. FIG. 7 is a diagram illustrating another example of a power conversion device according to the second embodiment.

(First embodiment)
A power conversion device 1 according to this embodiment will be described with reference to Fig. 1. The power conversion device 1 includes first and second input terminals It1 and It2, a power conversion circuit, and first and second output terminals Ot1 and Ot2. A power source is connected to the first and second input terminals It1 and It2, and power, for example, AC power, is input. A DC load, such as a battery, is connected to the first and second output terminals Ot1 and Ot2, and power is output from the first and second output terminals Ot1 and Ot2. The power conversion device 1 converts the AC power input to the first and second input terminals It1 and It2 into DC power and supplies the DC power to the DC load connected to the first and second output terminals Ot1 and Ot2.

The power conversion circuit is connected between the first and second input terminals It1 and It2 and the first and second output terminals Ot1 and Ot2. The power conversion circuit includes an inverter circuit 10 and a rectifier circuit 20.

The inverter circuit 10 converts and outputs the power input to the first and second input terminals It1 and It2. In this embodiment, a high-frequency AC current is generated from the AC power input to the first and second input terminals It1 and It2. The inverter circuit 10 includes a switch 11 and a passive element 15.

The switch 11 is connected between the first and second input terminals It1 and It2. The switch 11 is a semiconductor switching element SW, such as an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The passive element 15 includes a capacitor, an inductor, etc. as needed. The inverter circuit 10 can operate as a class E inverter that performs soft switching using resonance, under the control of the switch 11 by a control unit (not shown). However, the inverter circuit 10 may also operate as a circuit that performs simple hard switching.

The rectifier circuit 20 rectifies the output power of the inverter circuit 10 and outputs it to the first and second output terminals Ot1 and Ot2. The rectifier circuit 20 includes a diode D and a passive element 25. The cathode terminal of the diode D is connected to the first output terminal Ot1, and the anode terminal of the diode D is connected to the second output terminal Ot2.

In this embodiment, the power conversion device 1 is equipped with first and second coolers 30c, 30a that cool the diode D. The first cooler 30c is connected to the cathode terminal side of the diode D, and the second cooler 30a is connected to the anode terminal side of the diode D. The first and second coolers 30c, 30a are heat sinks made of, for example, an aluminum alloy or copper material. The first and second coolers 30c, 30a cool the diode D by dissipating heat generated by the diode D to the outside.

The first and second coolers 30c, 30a are electrically connected to the housing of the power conversion device 1. In other words, the first and second coolers 30c, 30a are electrically connected to the frame ground FG, which is at ground potential.

When the first and second coolers 30c, 30a are connected to the frame ground FG, parasitic capacitances Cc, Ca are formed between the diode D and each cooler 30c, 30a. Specifically, a first parasitic capacitance Cc is formed between the cathode terminal of the diode D and the first cooler 30c, and a second parasitic capacitance Ca is formed between the anode terminal of the diode D and the second cooler 30a. The first parasitic capacitance Cc is configured to have the same capacitance as the second parasitic capacitance Ca.

Below, we will explain how to connect the diode D to the coolers 30c and 30a with reference to Figures 2 and 3. Figures 2 and 3 show an example of how to connect the cathode terminal Dc of the diode D to the first cooler 30c.

As shown in FIG. 2, the cathode terminal Dc and the first cooler 30c are connected via an intermediate member 35. The intermediate member 35 is a member that has insulating and thermally conductive properties. For example, the intermediate member 35 is made by attaching a conductive material to a ceramic material such as AlN or SiN. If the cathode terminal Dc is die-bonded to a substrate that includes the inverter circuit 10 and the rectifier circuit 20, the intermediate member 35 can also be realized by the substrate and the wiring pattern on the substrate.

With the above configuration, a parasitic capacitance Cc is formed by sandwiching an insulating material with a dielectric constant between the cathode terminal Dc of the diode D and the first cooler 30c. This allows the parasitic capacitance Cc to be formed without adding any components to the power conversion device 1.

Furthermore, as shown in FIG. 3, a plate member 40 may be interposed between the cathode terminal Dc and the intermediate member 35 to promote heat dissipation from the diode D. The plate member 40 is made of a material that has electrical conductivity and thermal conductivity.

Considering that the heat diffusion angle is 45°, it is preferable that the area of the plate member 40 is smaller than a value A that satisfies the following formula:
(Equation 1)

Here, W is the width of each side of the cathode terminal Dc of the diode D when the cathode terminal Dc is assumed to be a square plane. Furthermore, tp is the thickness of the plate member 40. In other words, the area of the plate member is smaller than the value A obtained by squaring the sum of the width W of the diode D and twice the thickness tp of the plate member 40.

Although Figures 2 and 3 illustrate the connection between the cathode terminal Dc and the first cooler 30c, the above method may also be applied to the connection between the anode terminal Da and the second cooler 30a. In addition to the above-mentioned form, the intermediate member 35 may also be an insulating heat-conductive sheet containing a ceramic material as a filler.

In a power conversion device 1 configured as described above, the first cooler 30c is connected to the cathode terminal Dc of the diode D, and the first cooler 30c is connected to ground potential. When the power conversion device 1 is operated, the first parasitic capacitance Cc allows current to pass from the cathode to the anode, which does not pass through the diode D. The current passed by the first parasitic capacitance Cc becomes a common mode current (common mode noise) and leaks out.

In this embodiment, on the other hand, a second cooler 30a is connected to the anode terminal Da side of the diode D, and the second cooler 30a is connected to ground potential. A second parasitic capacitance Ca is also formed on the anode terminal Da side, so that the common mode current flowing out from one of the parasitic capacitances Cc, Ca can be diverted to the circuit side via the other parasitic capacitance Ca, Cc. This makes it possible to prevent the common mode current from flowing out of the power conversion device 1.

Figure 4 shows the progression of the common mode current Ic flowing through the first parasitic capacitance Cc. Common mode current Ic1 shows the waveform when there is no second cooler 30a connected to the anode terminal Da of diode D, and common mode current Ic2 shows the waveform when there is a second cooler 30a connected to the anode terminal Da of diode D.

In the power conversion device 1 of this embodiment, the first parasitic capacitance Cc and the second parasitic capacitance Ca are configured to be the same, which makes it possible to further suppress common-mode current.

In the power conversion device 1 of this embodiment, the first and second coolers 30c, 30a are connected to the diode D and the wiring pattern electrically connected to the diode D via an intermediate member 35 that has insulating and thermal conductivity. This makes it possible to insulate the first and second coolers 30c, 30a from the diode D while maintaining the heat dissipation performance of the first and second coolers 30c, 30a. Furthermore, by using a substrate as the intermediate member 35, the first and second parasitic capacitances Cc, Ca can be formed without adding any new components.

According to the power conversion device 1 of this embodiment, a plate member 40 having electrical and thermal conductivity may be provided between the diode D and the intermediate member 35. In this case, it is preferable that the area of the plate member 40 is smaller than the value A that satisfies the above formula 1.

As a result, the size of the plate member 40 can be reduced by limiting its size to that required for heat dissipation. By reducing the size of the plate member 40 on which the diode D is mounted, one of the parasitic capacitances Cc, Ca can be reduced. Therefore, when providing the other parasitic capacitance Ca, Cc, simply adding a small capacitance can have a significant effect on noise suppression. This makes it possible to achieve both heat dissipation performance and noise suppression.

Second Embodiment
A power conversion device 1 according to the second embodiment will be described with reference to Fig. 5. The power conversion device 1 according to the second embodiment differs from the power conversion device 1 according to the first embodiment in the configuration of the inverter circuit 10.

The switch 11 is composed of two semiconductor switching elements SW1 and SW2 connected in series, and is a bidirectional switch that switches the direction of current flowing between a pair of input terminals It1 and It2. The two semiconductor switching elements SW1 and SW2 can be, for example, N-channel MOSFETs. In this embodiment, the first semiconductor switching element SW1 and the second semiconductor switching element SW2 are a series circuit with their source terminals connected to each other. In addition to MOSFETs, the semiconductor switch can also be, for example, an IGBT (Insulated Gate Bipolar Transistor), which is a bipolar transistor. The switch 11 using IGBTs can be composed of, for example, a bidirectional IGBT in which two IGBTs are connected in anti-parallel. The switch element 111 using IGBTs can also be composed of a reverse-conducting IGBT in which one IGBT and one FWD (Free Wheeling Diode) are connected in anti-parallel.

The passive element 15 includes a capacitor C11, a first inductor L1, and a second inductor L2. The capacitor C11 is connected in parallel with the switch 11 between the pair of input terminals It1 and It2. The first inductor L1 is connected in series between the connection point between the first input terminal It1 and the switch 11 and the connection point between the first output terminal Ot1 and the cathode terminal of the diode D. The second inductor L2 is connected in series between the connection point between the second input terminal It2 and the switch 11 and the connection point between the second output terminal Ot2 and the anode terminal of the diode D.

In this configuration, the power conversion device 1 is equipped with first and second switch coolers 30s1 and 30s2 that cool the semiconductor switching elements SW1 and SW2 that make up the switch 11. The first switch cooler 30s1 is connected to the first semiconductor switching element SW1, and the second switch cooler 30s2 is connected to the first semiconductor switching element SW1. The first and second switch coolers 30s1 and 30s2 are, for example, heat sinks. The first and second switch coolers 30s1 and 30s2 cool the first and second semiconductor switching elements SW1 and SW2 by dissipating heat generated in the first and second semiconductor switching elements SW1 and SW2 to the outside.

The first and second switch coolers 30s1 and 30s2 are electrically connected to the housing of the power conversion device 1. In other words, the first and second switch coolers 30s1 and 30s2 are electrically connected to the frame ground FG, which is at ground potential.

When the first and second switch coolers 30s1, 30s2 are connected to the frame ground FG, third and fourth parasitic capacitances Cs1, Cs2 are formed between each semiconductor switching element SW1, SW2 and each switch cooler 30s1, 30s2. Specifically, a third parasitic capacitance Cs1 is formed between the first semiconductor switching element SW1 and the first switch cooler 30s1, and a fourth parasitic capacitance Cs2 is formed between the second semiconductor switching element SW2 and the second switch cooler 30s2.

In the power conversion device 1 according to this embodiment, the common-mode current flowing from the semiconductor switching elements SW1 and SW2 of the inverter circuit 10 is commutated to the circuit side by the first and second parasitic capacitances Cc and Ca described above. This makes it possible to prevent the common-mode current from flowing outside the power conversion device 1. In particular, when the same elements are used for the first and second semiconductor switching elements SW1 and SW2 that make up the bidirectional switch, the noise suppression effect is even greater.

In this embodiment, the passive elements 15 that make up the inverter circuit 10 are arranged symmetrically on the first input terminal It1 side and the second input terminal It2 side. This allows for further suppression of common-mode current.

As shown in FIG. 6, the power conversion device 1 may have first and second capacitors C51 and C52 disposed between the inverter circuit 10 and the rectifier circuit 20. The first capacitor C51 is disposed between the first input terminal It1 and the first output terminal Ot1, and the second capacitor C52 is disposed between the second input terminal It2 and the second output terminal Ot2.

Furthermore, as shown in FIG. 7, the power conversion device 1 may include a transformer Tr between the inverter circuit 10 and the rectifier circuit 20. The passive element 15 of the inverter circuit 10 includes a capacitor C12 connected in series with the first inductor L1.

In this way, the power conversion device 1 may include an insulating section 50 between the inverter circuit 10 on the input side and the rectifier circuit 20 on the output side.

In the above-described embodiment, the power conversion device 1 converts AC power input to the first and second input terminals It1, It2 into DC power. However, the power conversion device 1 may also convert DC power input to the first and second input terminals It1, It2 into DC power of a different voltage, like an asynchronous (diode) rectification DC/DC converter. Also, while it has been described that the cooler for cooling the diode D is composed of the first and second coolers 30c, 30a, and that the coolers for cooling the semiconductor switching elements SW1, SW2 that make up the switch 11 are composed of the first and second switch coolers 30s1, 30s2, some or all of these coolers may be integrated.

As described above, an embodiment of the present invention has been described, but the descriptions and drawings that form part of this disclosure should not be understood as limiting this invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

REFERENCE SIGNS LIST 1 power conversion device 10 inverter circuit 11 switch 15 passive element 20 rectifier circuit 25 passive element D diode 30c, 30a cooler

Claims (7)

A power conversion device comprising: a pair of input terminals to which power is input; a power conversion circuit connected to the pair of input terminals; and a pair of output terminals to which a load is connected,
The power conversion circuit includes:
an inverter circuit including a switch connected between the pair of input terminals, converting power input to the pair of input terminals and outputting the converted power;
a rectifier circuit including a diode having a cathode terminal connected to one of the pair of output terminals and an anode terminal connected to the other of the pair of output terminals, rectifying the output power of the inverter circuit and outputting the rectified power to the pair of output terminals;
a first cooler connected to the cathode terminal side of the diode and cooling the diode;
a second cooler connected to the anode terminal side of the diode and cooling the diode,
the first cooler and the second cooler are each connected to a ground potential;
Power conversion device. a first parasitic capacitance between the cathode terminal of the diode and the first cooler is configured to be equal to a second parasitic capacitance between the anode terminal of the diode and the second cooler;
The power conversion device according to claim 1 . the power input to the pair of input terminals is AC power,
The switch of the inverter circuit is
a bidirectional switch that switches the direction of current flowing between the pair of input terminals;
The power conversion device according to claim 1 or 2. The inverter circuit
a capacitor connected in parallel with the bidirectional switch between the pair of input terminals;
a first inductor connected in series between a connection point between one of the pair of input terminals and the bidirectional switch and a connection point between the one of the pair of output terminals and the cathode terminal of the diode;
a second inductor connected in series between a connection point between the other of the pair of input terminals and the bidirectional switch and a connection point between the other of the pair of output terminals and the anode terminal of the diode,
The power conversion device according to claim 3 . the first cooler and the second cooler are connected to the diode via an intermediate member having insulating properties and thermal conductivity;
The power conversion device according to claim 2 . At least one of the first parasitic capacitance and the second parasitic capacitance is formed by a substrate including the inverter circuit and the rectifier circuit and a wiring pattern on the substrate.
The power conversion device according to claim 5 . the diode and the intermediate member are connected via a plate member having electrical conductivity and thermal conductivity;
the area of the plate member is smaller than the square of the sum of the width of the diode and twice the thickness of the plate member;
The power conversion device according to claim 6.