Power converter

Abstract

To provide a power conversion device capable of achieving miniaturization and stable operation.SOLUTION: A smoothing capacitor 21 outputs high side potential of DC voltage, and a smoothing capacitor 22 is connected in series to the smoothing capacitor 21 and outputs low side potential of DC voltage. An inverter circuit 103 converts DC voltage output from the smoothing capacitors 21 and 22 into AC voltage. A control circuit 104 controls the inverter circuit 103. The inverter circuit 103 is mounted on a main circuit board 61. Each of the smoothing capacitors 21 and 22 is arranged so that an axial direction for determining the longest size is approximately parallel to a surface direction of the main circuit board 61. The smoothing capacitor 21 is arranged in a position further away from the control circuit 104 than the smoothing capacitor 22.SELECTED DRAWING: Figure 3

Description

Background Art

[0001] The present invention relates to a power conversion device, for example, a power conversion device that supplies AC power to a load such as a motor.

Technical Field

[0002] A power conversion device for driving a motor generally includes a rectifier section that converts an AC voltage into a DC voltage, a smoothing capacitor that smooths the DC voltage, and an inverter circuit that inversely converts the DC voltage into an AC voltage. The rectifier section mainly uses two types of circuit systems depending on the voltage value of the AC voltage. When the AC voltage exceeds 200V, a full-wave rectifier circuit is used, and when the AC voltage is about 100V to 120V, a voltage-doubling rectifier circuit is used. When a voltage-doubling rectifier circuit is used, a DC voltage approximately twice the peak value of the AC voltage can be obtained.

[0003] As a configuration that combines two types of circuit systems, that is, a full-wave rectifier circuit and a voltage-doubling rectifier circuit, Patent Document 1 describes a power conversion device for driving a motor that switches between full-wave rectification and voltage-doubling rectification according to the rotational speed of the motor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The power conversion device described in Patent Document 1 operates a voltage doubler rectifier circuit by conducting a switch shown in Figure 1 of Patent Document 1. As shown in Figure 1, the voltage doubler rectifier circuit comprises a first electrolytic capacitor connected between the high-side potential node of the DC voltage and the AC power supply, and a second electrolytic capacitor connected between the AC power supply and the low-side potential node of the DC voltage. Figure 7 of Patent Document 1 shows the positional relationship between the inverter circuit and the first and second electrolytic capacitors. The first and second electrolytic capacitors are mounted on a substrate on which the inverter circuit is mounted, such that the height direction of the first and second electrolytic capacitors is perpendicular to the surface of the substrate.

[0006] Due to its operating principle, a voltage doubler rectifier circuit charges the electrolytic capacitor only within one half-cycle of either the positive or negative AC voltage. Therefore, using a voltage doubler rectifier circuit can result in larger ripple currents compared to using a full-wave rectifier circuit, which charges the capacitor in both positive and negative AC voltage cycles. Consequently, when using electrolytic capacitors of the same capacitance in both a full-wave rectifier circuit and a voltage doubler rectifier circuit with the same output capacity, the voltage doubler rectifier circuit tends to generate more heat from the electrolytic capacitor. For this reason, when comparing rectifier circuits with the same output capacity, it is common practice to design the electrolytic capacitor used in a voltage doubler rectifier circuit to have a larger capacitance than that used in a full-wave rectifier circuit.

[0007] Furthermore, electrolytic capacitors used in voltage-doubler rectifier circuits can have a voltage rating of approximately half that of electrolytic capacitors used in full-wave rectifier circuits. However, depending on the specifications of the power conversion device, the increase in volume due to the increased capacitance, as mentioned above, may be greater than the decrease in volume of the electrolytic capacitor due to this reduction in voltage rating. Generally, the radial or height of an electrolytic capacitor increases as its capacitance increases. For this reason, when electrolytic capacitors are mounted in the direction shown in Patent Document 1 in a power conversion device equipped with a voltage-doubler rectifier circuit, there was a risk that the size of the power conversion device would increase due to the increase in the radial or height of the electrolytic capacitors, or the increase in the substrate area due to the placement of a separate smoothing capacitor.

[0008] Furthermore, generally, the case potential of an electrolytic capacitor is an indeterminate potential between the negative terminal potential and the positive terminal potential. Therefore, if the wiring of a weak current signal, such as a current detection signal or gate signal in an inverter circuit, which is generated based on the lower side of the DC voltage potential, is close to the first electrolytic capacitor that outputs the higher side of the DC voltage potential, a high potential difference will occur between the case potential and the potential of the weak current signal. As a result, a large amount of noise may be superimposed on the weak current signal, potentially causing malfunctions. This type of malfunction problem can become more pronounced as the size of the power converter decreases.

[0009] This invention has been made in view of the above, and one of its objectives is to provide a power conversion device that can achieve both miniaturization and stable operation.

[0010] The aforementioned and other objects and novel features of the present invention will become apparent from the description herein and the accompanying drawings. [Means for solving the problem]

[0011] In one embodiment, the power conversion circuit comprises first and second capacitors, an inverter circuit, a control circuit, and a first circuit board. The first capacitor outputs the high-side potential of the DC voltage, and the second capacitor, connected in series with the first capacitor, outputs the low-side potential of the DC voltage. The inverter circuit converts the DC voltages output from the first and second capacitors into AC voltages. The control circuit controls the inverter circuit. The inverter circuit is mounted on the first circuit board. The first and second capacitors are arranged such that the axial direction determining their maximum size is substantially parallel to the plane direction of the first circuit board. The first capacitor is positioned further from the control circuit than the second capacitor. [Effects of the Invention]

[0012] To briefly explain the effects obtained by a representative embodiment of the invention disclosed in this application, it is possible to achieve both miniaturization and stable operation in a power conversion device. [Brief explanation of the drawing]

[0013] [Figure 1] This is a circuit diagram showing a schematic configuration example of a power conversion device according to Embodiment 1. [Figure 2] Figure 1 is a circuit diagram showing an example of the control circuit configuration. [Figure 3] Figure 1 is a bird's-eye view showing an example of the external appearance of the power conversion device. [Figure 4] Figure 3 is a side view of the power conversion device shown, viewed from a different direction. [Figure 5] This is a bird's-eye view showing a different external appearance from Figure 3 in the power conversion device according to Embodiment 2. [Figure 6] Figure 5 is a side view of the power converter shown, viewed from a different direction. [Figure 7] Figure 5 shows an example of a method for physically fixing a capacitor board to the main circuit board. [Figure 8] This is a bird's-eye view showing a different external appearance from Figure 5 for the power conversion device according to Embodiment 3. [Figure 9] Figure 8 is a side view of the power conversion device shown, viewed from a different direction. [Figure 10] This is a bird's-eye view showing a different external appearance from Figure 8 of the power conversion device according to Embodiment 4. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all drawings used to illustrate the embodiments, the same reference numerals are generally used for identical components, and repeated descriptions of such components will be omitted.

[0015] (Embodiment 1) <Circuit configuration of power converter> FIG. 1 is a circuit diagram showing a schematic configuration example of a power conversion device according to Embodiment 1. The power conversion device 1 shown in FIG. 1 includes a rectifier circuit 101, a smoothing capacitor unit 102, an inverter circuit 103, a control circuit 104, and an inrush current limiting circuit 105. The smoothing capacitor unit 102 includes a smoothing capacitor (first capacitor) 21 that outputs a high-side potential VP of a DC voltage, and a smoothing capacitor (second capacitor) 22 that is connected in series to the smoothing capacitor 21 and outputs a low-side potential VN of the DC voltage.

[0016] The rectifier circuit 101 rectifies an external AC voltage 2 using diodes 11 and 12, and charges the smoothing capacitors 21 and 22 in the smoothing capacitor unit 102 with the rectified DC voltage. The smoothing capacitor unit 102 smooths the DC voltage input from the rectifier circuit 101. The inverter circuit 103 converts the DC voltage output from the smoothing capacitor unit 102 into an AC voltage. The control circuit 104 controls the inverter circuit 103.

[0017] The rectifier circuit 101 and the smoothing capacitor unit 102 connected as shown in FIG. 1 are generally called a voltage doubler rectifier circuit. In the positive half cycle of the AC voltage 2, the diode 11 conducts and the smoothing capacitor 21 is charged. In the negative half cycle of the AC voltage 2, the diode 12 conducts and the smoothing capacitor 22 is charged.

[0018] As a result of the smoothing capacitors 21 and 22 being alternately charged in this way, for example, when the effective value of the AC voltage 2 is 100 V, the voltage across each of the smoothing capacitors 21 and 22 becomes about 141 V, which is the peak voltage of the AC voltage 2. Thereby, the DC voltage output from the smoothing capacitor unit 1, that is, the voltage of the high-side potential VP with respect to the low-side potential VN, becomes about 282 V, which is the sum of the voltages across the smoothing capacitors 21 and 22.

[0019] Various types of capacitors, such as film capacitors and ceramic capacitors, can be used as smoothing capacitors 21 and 22 in such a power conversion device 1. However, electrolytic capacitors are often used for smoothing capacitors 21 and 22 from the viewpoint of smoothing the DC voltage with a large capacitance and obtaining high voltage resistance. Therefore, in this embodiment, smoothing capacitors 21 and 22 will be described assuming that they are mainly electrolytic capacitors.

[0020] The inverter circuit 103 includes switching elements 31-36 and outputs AC power to a motor 3, which is an example of a load. The switching elements 31-36 shown in Figure 1 are typically composed of IGBTs, but may also be composed of other power semiconductor transistors such as MOSFETs. The control circuit 104 detects the current flowing through the motor 3 and the switching elements 31-36 and outputs drive signals to the switching elements 31-36 to make the motor 3 operate as desired.

[0021] The inrush current limiting circuit 105 includes a current-limiting resistor 51 and a relay 52, and is provided for the purpose of limiting the charging current to the smoothing capacitors 21 and 22, i.e., the large inrush current, when the AC voltage 2 is applied. When the potential difference between the high-side potential VP and the low-side potential VN of the DC voltage is lower than a predetermined value, such as immediately after the AC voltage 2 is applied, the relay 52 is controlled to the off state. As a result, the smoothing capacitors 21 and 22 are charged with a current limited by the current-limiting resistor 51. Subsequently, when the smoothing capacitors 21 and 22 are charged to a voltage value or higher, the relay 52 is controlled to the on state. Note that the relay 52 can be replaced with another element such as a thyristor.

[0022] As mentioned earlier, smoothing capacitor 21 is charged during the positive half-cycle of the AC voltage 2, and smoothing capacitor 22 is charged during the negative half-cycle of the AC voltage 2. Therefore, assuming that relay 52 is in the ON state, smoothing capacitor 21 smooths the relationship between the high-side potential VP of the DC voltage and the AC voltage 2, and smoothing capacitor 22 smooths the relationship between the AC voltage 2 and the low-side potential VN of the DC voltage.

[0023] Generally, the case potential of an electrolytic capacitor is an indeterminate potential between the negative terminal potential and the positive terminal potential of the electrolytic capacitor. Therefore, the case potential of smoothing capacitor 21 will be between the high-side DC voltage potential VP and the AC voltage 2, and the case potential of smoothing capacitor 22 will be between the AC voltage 2 and the low-side DC voltage potential VN. For example, if the DC voltage is 282V, using the low-side DC voltage potential VN as the reference, the case potential of smoothing capacitor 22 will be between 0V and 141V, and the case potential of smoothing capacitor 21 will be between 141V and 282V.

[0024] Figure 2 is a circuit diagram showing an example configuration of the control circuit 104 in Figure 1. The control circuit 104 shown in Figure 2 comprises a current sensing resistor 41, an amplification circuit 42, a microcontroller 43, and a gate driver 44. The current sensing resistor 41 converts the current flowing through the inverter circuit 103 into a voltage signal of, for example, about 1V, and outputs this voltage signal to the amplification circuit 42. The amplification circuit 42 amplifies the input voltage signal to about several volts and outputs it to the microcontroller 43 as a current sensing signal.

[0025] The microcontroller 43 outputs a drive signal of several volts to the gate driver 44 based on the input current detection signal. The gate driver 44 outputs a gate signal of, for example, several tens of volts to the inverter circuit 103 based on the drive signal from the microcontroller 43. The amplifier circuit 42 and the microcontroller 43 are not shown in the diagram, but they operate using a power supply voltage of several volts, for example, with a reference to the low-side potential VN of the DC voltage.

[0026] Thus, the inverter circuit 103 is a high-voltage section that handles a voltage of approximately 282V with respect to the lower-side potential VN of the DC voltage, while the control circuit 104 is a low-voltage section that handles a voltage of several to tens of volts with respect to the lower-side potential VN of the DC voltage. The power supply voltages for the microcontroller 43 and gate driver 44 are generated separately by, for example, a power supply circuit not shown.

[0027] <External shape of a power converter> Figure 3 is a bird's-eye view showing an example of the external shape of the power converter shown in Figure 1, and Figure 4 is a side view of the power converter shown in Figure 3 from a different direction. The power converter 1a shown in Figures 3 and 4 has the following additional major components compared to the configuration example shown in Figure 1: a main circuit board (first board) 61, a main circuit terminal block 62, electric wires 71-73, and an overvoltage protection element 81. In Figures 3 and 4, the mutually orthogonal directions are defined as the width direction W, the depth direction D, and the height direction H, and the plane direction determined by the width direction W and the height direction H is defined as the plane direction of the main circuit board 61. Figure 4 shows an example of the external shape when the plane determined by the depth direction D and the height direction H is considered the side.

[0028] The main circuit board (first board) 61 is equipped with a rectifier circuit 101, an inverter circuit 103, a control circuit 104, a current-limiting resistor 51, a relay 52, a main circuit terminal block 62, and an overvoltage protection element 81. These are appropriately connected via wiring patterns on the main circuit board 61. The main circuit terminal block 62 is provided with terminals for conducting the main circuit current, such as an input terminal for the AC voltage 2 and an output terminal for the motor 3. The AC voltage 2 input to the main circuit terminal block 62 is transmitted via the wiring patterns on the main circuit board 61, with one end going to the rectifier circuit 101 and the other end going to the current-limiting resistor 51 and relay 52, i.e., the inrush current limiting circuit 105.

[0029] On the main circuit board 61, the nodes for the high-side potential VP and low-side potential VN of the DC voltage output from the rectifier circuit 101, and the output node of the inrush current limiting circuit 105 are connected to the positive and negative terminals of the smoothing capacitors 21 and 22 via wires 71 to 73. Specifically, the node for the high-side potential VP on the main circuit board 61 is connected to the positive terminal of the smoothing capacitor 21 via wire 71. The node for the low-side potential VN on the main circuit board 61 is connected to the negative terminal of the smoothing capacitor 22 via wire 73. The output node of the inrush current limiting circuit 105, and thus the negative-side node of the AC voltage 2, is commonly connected to the negative terminal of the smoothing capacitor 21 and the positive terminal of the smoothing capacitor 22 via wire 72.

[0030] Furthermore, on the main circuit board 61, the nodes for the high-side potential VP and low-side potential VN of the DC voltage are also connected to the inverter circuit 103 via wiring patterns on the main circuit board 61. The three-phase AC voltage output from the inverter circuit 103 is transmitted to the main circuit terminal block 62 via wiring patterns on the main circuit board 61. In this example, the control circuit 104 is mounted on the main circuit board 61 and, as shown in Figure 2, is connected to the node for the low-side potential VN of the DC voltage, the inverter circuit 103, and a node for a power supply voltage (not shown) via wiring patterns on the main circuit board 61.

[0031] The overvoltage protection element 81 is provided to protect semiconductor elements from high voltages such as static electricity. For example, the overvoltage protection element 81 is a varistor element connected between the high-side potential VP and the low-side potential VN of a DC voltage, or between the lines of an AC voltage 2, for the purpose of protecting the diodes 11 and 12 of the rectifier circuit 101.

[0032] Here, for example, in Patent Document 1, the smoothing capacitors 21 and 22 are arranged on the main circuit board 61 such that the axial direction that determines their longest size is substantially perpendicular to the surface of the main circuit board 61. In particular, as shown in Figure 4, when using electrolytic capacitors with positive and negative terminals on the same surface, this arrangement is usually possible. However, in this case, if the longest size of the smoothing capacitors 21 and 22 increases, the size in the depth direction D in Figure 3 increases, which can lead to an increase in the size of the power conversion device.

[0033] Therefore, in the power converter 1a shown in Figures 3 and 4, the smoothing capacitors 21 and 22 are arranged such that the axial direction that determines the longest size, in this example the height direction H, is approximately parallel to the plane direction of the main circuit board 61. This suppresses the increase in the size in the depth direction D in Figure 3, and enables miniaturization of the power converter 1a.

[0034] Furthermore, the smoothing capacitor 21 that outputs the high-side potential VP is located further away from the control circuit 104 than the smoothing capacitor 22 that outputs the low-side potential VN. In this example, since the control circuit 104 is mounted on the main circuit board 61, the smoothing capacitor 21 is located further away from the main circuit board 61 than the smoothing capacitor 22. Specifically, in this example, the smoothing capacitor 21 is stacked on top of the smoothing capacitor 22 in the depth direction D.

[0035] As mentioned above, the case potential of the smoothing capacitor 21 is between the high-side potential VP of the DC voltage and the AC voltage 2, and the case potential of the smoothing capacitor 22 is between the AC voltage 2 and the low-side potential VN of the DC voltage. Therefore, when a low-voltage section that operates based on the low-side potential VN of the DC voltage, such as the control circuit 104, is in close proximity to the smoothing capacitor 21, a potential difference of at least 141V can occur in the space between the low-voltage section and the case of the smoothing capacitor 21. As a result, a large amount of noise may propagate from the smoothing capacitor 21 to the low-voltage section, potentially causing malfunctions in the control circuit 104 and other components.

[0036] Therefore, as shown in Figures 3 and 4, it is beneficial to position the smoothing capacitor 21 at an appropriate distance D in the depth direction from the main circuit board 61. This prevents malfunctions of the control circuit 104, etc., and enables stable operation in addition to the miniaturization of the power converter 1 mentioned above. Here, the smoothing capacitors 21 and 22 have positive and negative terminals on the same surface, but in some cases, the positive terminal may be on one of two opposing surfaces and the negative terminal on the other. In this case, for example, in Figure 4, the wires 71 and 73 are connected to the right side of the smoothing capacitors 21 and 22, and the wire 72 is connected to the left side.

[0037] Furthermore, while Figures 3 and 4 show an example where the smoothing capacitors 21 and 22 are stacked in the depth direction D, the arrangement of the smoothing capacitors 21 and 22 may be changed as appropriate, as long as the smoothing capacitor 21 is positioned further away from the control circuit 104 than the smoothing capacitor 22. However, for example, in Figure 3, if the control circuit 104, smoothing capacitor 22, and smoothing capacitor 21 are arranged in the width direction W, the area of ​​the main circuit board 61 may increase. On the other hand, the area of ​​the main circuit board 61 may be constrained by the application of the power conversion device 1. From this viewpoint, it is desirable to arrange the smoothing capacitors 21 and 22 in the depth direction D.

[0038] Furthermore, the method of Embodiment 1 can be applied not only to single-phase voltage doubler rectifier circuits but also to other circuits such as three-phase full-wave rectifier circuits, as long as the smoothing capacitors 21 and 22 are connected in series. For example, in a three-phase full-wave rectifier circuit, from the viewpoint of easily ensuring voltage withstand capability, it can also be applied to a configuration in which one smoothing capacitor with a 400V voltage withstand capability is replaced with two smoothing capacitors with a 200V voltage withstand capability connected in series. In this case, in Figure 4, the wire 72 connects the negative terminal of the smoothing capacitor 21 and the positive terminal of the smoothing capacitor 22, but it does not need to be connected to the main circuit board 61.

[0039] Although not shown in the diagram, the smoothing capacitors 21 and 22 can be fixed to the main circuit board 61 using various methods. For example, the wires 71 to 73 can be made of highly rigid copper bars or the like. Alternatively, the main circuit board 61 and the smoothing capacitor 22, and the smoothing capacitor 22 and the smoothing capacitor 21 can be fixed together with connecting members. Another method is to use a cover member (not shown) that houses the power converter 1a and determine the shape of the cover member so that the smoothing capacitors 21 and 22 can be fixed to it, or to attach holders for fixing the smoothing capacitors 21 and 22 to the cover member.

[0040] <Main effects of Embodiment 1> In the first embodiment described above, the smoothing capacitors 21 and 22 are arranged such that the axial direction that determines the longest size is substantially parallel to the plane direction of the main circuit board 61, and the smoothing capacitor 21 that outputs the high-side potential VP is positioned further from the control circuit 104 than the smoothing capacitor 22 that outputs the low-side potential VN. This makes it possible to achieve both miniaturization and stable operation in the power conversion devices 1 and 1a.

[0041] (Embodiment 2) <External shape of a power converter> Figure 5 is a bird's-eye view showing a different external configuration of the power converter according to Embodiment 2, compared to Figure 3, and Figure 6 is a side view of the power converter shown in Figure 5, viewed from a different direction. In the power converter 1b shown in Figures 5 and 6, a capacitor board (second board) 63 is added compared to the configuration example shown in Figure 3. The capacitor board 63 is positioned with its surface direction being approximately perpendicular to the surface of the main circuit board 61. That is, the surface direction of the capacitor board 63 is the surface direction defined by the width direction W and the depth direction D.

[0042] In the configuration examples shown in Figures 3 and 4, the smoothing capacitors 21 and 22 were connected to the main circuit board 61 only via wires 71 to 73. Therefore, in order to fix the smoothing capacitors 21 and 22 to the main circuit board 61 using the configuration examples shown in Figures 3 and 4, some kind of modification was necessary, such as applying copper bars to the wires 71 to 73.

[0043] On the other hand, in Figures 5 and 6, a capacitor board 63 is provided, and the smoothing capacitors 21 and 22 are mounted on the capacitor board 63. The capacitor board 63 has through holes for connecting the smoothing capacitors 21 and 22, and the smoothing capacitors 21 and 22 are fixed to the capacitor board 63 by connecting them to the through holes with solder or the like.

[0044] One end of each wire 71-73 is connected to a through-hole provided in the capacitor board 63 using solder, and the other end is connected to a through-hole provided in the main circuit board 61 using solder. This physically fixes the smoothing capacitors 21 and 22 to the main circuit board 61 via the capacitor board 63. Furthermore, the positive and negative terminals of the smoothing capacitors 21 and 22 are electrically connected to the main circuit board 61 via the capacitor board 63 and the wires 71-73.

[0045] Figure 7 shows an example of a method for physically fixing the capacitor board 63 to the main circuit board 61 in Figure 5. In Figure 7, the smoothing capacitors 21 and 22 are not shown in order to clearly show the contact areas between the boards. As shown in Figure 7, a projection is formed on the end of the capacitor board 63 so as to protrude in the depth direction D. On the other hand, the main circuit board 61 has an opening formed to fit into the projection of the capacitor board 63.

[0046] As shown in Figure 7, by fitting the projections on the capacitor board 63 into the openings on the main circuit board 61, the capacitor board 63 can be made to stand independently of the main circuit board 61. Furthermore, since the positional relationship between the capacitor board 63 and the main circuit board 61 is fixed, the positions of the smoothing capacitors 21 and 22 relative to the main circuit board 61 are also fixed.

[0047] Here, the power conversion device 1b shown in Figures 5 to 7 can be assembled, for example, by the following procedure. First, one end of the electric wires 71 to 73 is soldered to the capacitor board 63, and then the smoothing capacitors 21 and 22 are mounted on the capacitor board 63. After that, the capacitor board 63 is attached to the main circuit board 61, and the other ends of the electric wires 71 to 73 are soldered to the main circuit board 61. At this time, as shown in Figure 7, by using a mechanism that allows the capacitor board 63 to be inserted into the main circuit board 61, a series of assembly steps, including positioning, can be simplified.

[0048] In this example, the capacitor board 63 is used as a means of physically fixing the smoothing capacitors 21 and 22 to the main circuit board 61, but it can also be used as a means of electrical connection. Specifically, for example, a slot containing electrical terminals is mounted on the main circuit board 61, and electrical terminals are formed on the end of the capacitor board 63, which are connected to the positive and negative terminals of the smoothing capacitors 21 and 22 via wiring patterns. The end of the capacitor board 63 is then inserted into the slot of the main circuit board 61. As a result, the capacitor board 63 and the main circuit board 61 are physically fixed and electrically connected.

[0049] However, in this case, the main circuit board 61 needs to be provided with relatively large slots to accommodate high currents. In this case, a large mounting area for the slots needs to be secured on the main circuit board 61, and furthermore, component costs for the slots are also required. On the other hand, when using the method shown in Figures 5 to 7, such a mounting area for the slots is unnecessary, and furthermore, component costs for the slots are also not required.

[0050] <Main effects of Embodiment 2> As described above, by using the method of Embodiment 2, the same effects as those described in Embodiment 1 can be obtained. Furthermore, by providing the capacitor board 63, although the component cost may increase compared to the method of Embodiment 1, it becomes easier to physically fix the smoothing capacitors 21 and 22 to the main circuit board 61, and the assembly process can also be simplified.

[0051] (Embodiment 3) <External shape of a power converter> Figure 8 is a bird's-eye view showing a different external configuration of the power converter according to Embodiment 3, compared to Figure 5, and Figure 9 is a side view of the power converter shown in Figure 8, viewed from a different direction. In the power converter 1c shown in Figures 8 and 9, two connecting members 64 are added compared to the configuration example shown in Figure 5. One of the two connecting members 64 physically connects the smoothing capacitor 22 to the main circuit board 61, and the other of the two connecting members 64 physically connects the smoothing capacitor 21 to the smoothing capacitor 22.

[0052] For example, if the positions of the smoothing capacitors 21 and 22 are determined via the main circuit board 61 and capacitor board 63 using the method described in Embodiment 2, gaps may occur between the smoothing capacitor 22 and the main circuit board 61, or between the smoothing capacitors 21 and 22, due to dimensional tolerances. These gaps may induce vibration of the smoothing capacitors 21 and 22 when the product vibrates, for example, during transportation. Therefore, it is desirable to fill these gaps with an insulating material to fix the smoothing capacitors 21 and 22 in place.

[0053] Therefore, the power converter 1c shown in Figures 8 and 9 is configured to fill the gap by applying a joining member 64 to it. Specifically, adhesives, adhesive tapes, curable rubber, etc., can be used as the joining member 64.

[0054] <Main effects of Embodiment 3> As described above, by using the method of Embodiment 3, the same effects as those described in Embodiment 2 can be obtained. Furthermore, the bonding member 64 makes it possible to fix the smoothing capacitors 21 and 22 to the main circuit board 61 more firmly.

[0055] (Embodiment 4) <External shape of a power converter> Figure 10 is a bird's-eye view showing a different external configuration example of a power converter according to Embodiment 4, compared to Figure 8. In the power converter 1d shown in Figure 10, a control board (third board) 65 electrically connected to the main circuit board 61 is added compared to the configuration example shown in Figure 8. The control board 65 is positioned with its plane direction substantially perpendicular to the surface of the main circuit board 61, similar to the capacitor board 63.

[0056] Specifically, the control board 65 is positioned on one side of the main circuit board 61, oriented approximately perpendicular to the capacitor board 63. That is, the plane direction of the control board 65 is determined by the depth direction D and the height direction H, and the plane direction of the capacitor board 63 is determined by the depth direction D and the width direction W. The control circuit 104 is mounted on the control board 65, not on the main circuit board 61 as in the case of Figure 8.

[0057] Therefore, the smoothing capacitor 21, which outputs the high-side potential VP, is positioned further away from the control board 65 on which the control circuit 104 is mounted than the smoothing capacitor 22, which outputs the low-side potential VN. Also, weak current signals from the control circuit 104, etc., are transmitted to the main circuit board 61 via the control board 65. For this reason, the smoothing capacitor 21 is positioned further away from the main circuit board 61 than the smoothing capacitor 22.

[0058] Here, the low-voltage section described in Embodiment 1 is not limited to the control circuit 104, but may include various circuits depending on the function of the power converter, such as a communication circuit with an external interface, a power supply circuit for control, and a functional safety circuit. If, due to the addition of such functions, sufficient mounting area for the low-voltage section cannot be secured on the main circuit board 61, it is beneficial to provide a separate control board 65 as shown in Figure 10, rather than increasing the area of ​​the main circuit board 61, i.e., the size in the width direction W or height direction H. In this case, for example, the control board 65 handles the low-voltage section, and the main circuit board 61 handles the high-voltage section.

[0059] In the example shown in Figure 10, the control board 65 extends in the same direction as the stacking direction of the smoothing capacitors 21 and 22, i.e., in the depth direction D. This helps to suppress the increase in size of the power converter 1d. Furthermore, from the standpoint of device size, it is desirable that the size of the control board 65 in the depth direction D does not exceed the size of the stacked smoothing capacitors 21 and 22 in the depth direction D as much as possible.

[0060] In the example shown in Figure 10, the control board 65 is positioned approximately perpendicular to the main circuit board 61, but this is not limited to this configuration, and in some cases, it may be positioned approximately parallel to the main circuit board 61. Furthermore, the dimensions of the control board 65 depend on the specifications of the power converter and are not limited to the dimensions shown in Figure 10.

[0061] <Main effects of Embodiment 4> As described above, by using the method of Embodiment 4, the same effects as those described in Embodiment 3 can be obtained. Furthermore, by providing the control board 65, it is possible to increase the mounting area of ​​the low-voltage section while suppressing the increase in size of the power converter 1d, and by moving the smoothing capacitor 21 away from the low-voltage section, stable operation of the power converter 1d can be achieved.

[0062] The present invention has been described in detail above based on embodiments, but the present invention is not limited to the embodiments described above and can be modified in various ways without departing from its essence. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner and are not necessarily limited to those having all the described configurations. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add a configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with a configuration of another embodiment. [Explanation of symbols]

[0063] 1. 1a~1d Power conversion device 101 Rectifier circuit 103 Inverter Circuit 104 Control circuits 21,22 Smoothing Capacitor 61 Main circuit board 63 Capacitor board 64 Joining members 65 Control board 71~73 Electric wire VP high side potential VN Low side potential

Claims

1. A first capacitor that outputs a high-side potential of the DC voltage, A second capacitor connected in series with the first capacitor outputs a lower-side potential of the DC voltage, An inverter circuit that converts the DC voltage output from the first capacitor and the second capacitor into an AC voltage, A control circuit that controls the inverter circuit, A first circuit board on which the inverter circuit is mounted, Equipped with, When the external dimensions of a capacitor are expressed in terms of dimensions in three mutually orthogonal axes, The first capacitor and the second capacitor are arranged such that the axis having the longest size among the three axis directions is substantially parallel to the plane direction of the first substrate. The control circuit is mounted on the first substrate, The first capacitor is positioned further away from the first substrate than the second capacitor. The first capacitor is arranged to be stacked on the second capacitor in a direction substantially perpendicular to the surface of the first substrate. Power converter.

2. In the power conversion device according to claim 1, Furthermore, the first substrate is equipped with a rectifier circuit that rectifies an external AC voltage to charge the first capacitor and the second capacitor, The first capacitor is charged by the positive half-cycle of the external AC voltage, The second capacitor is charged by the negative half-cycle of the external AC voltage. Power converter.

3. In the power conversion device according to claim 1, Each of the first and second capacitors has a positive terminal and a negative terminal on the same side. Power converter.

4. In the power conversion device according to claim 3, Furthermore, the system includes a second substrate arranged with a surface direction substantially perpendicular to the surface of the first substrate, The first capacitor and the second capacitor are mounted on the second circuit board. Power converter.

5. In the power conversion device according to claim 4, The second substrate has a protrusion formed on it. The first substrate has an opening formed therein that fits into the projection. Power converter.

6. In the power conversion device according to claim 4, The positive terminal and the negative terminal of the first capacitor or the second capacitor are electrically connected to the first substrate via the second substrate and an electric wire, respectively. Power converter.

7. In the power conversion device according to claim 1, The first capacitor is physically joined to the first substrate via a bonding member. Power converter.

8. In the power conversion device according to claim 1, The first capacitor and the second capacitor are physically joined to each other via a connecting member. Power converter.

9. A first capacitor that outputs a high-side potential of a DC voltage, A second capacitor connected in series with the first capacitor outputs a lower-side potential of the DC voltage, An inverter circuit that converts the DC voltage output from the first capacitor and the second capacitor into an AC voltage, A control circuit that controls the inverter circuit, A first circuit board on which the inverter circuit is mounted, Equipped with, When the external dimensions of a capacitor are expressed in terms of dimensions in three mutually orthogonal axes, The first capacitor and the second capacitor are arranged such that the axis having the longest size among the three axis directions is substantially parallel to the plane direction of the first substrate. Furthermore, the system includes a third substrate electrically connected to the first substrate, The third substrate is arranged with its surface direction being substantially perpendicular to the surface of the first substrate. The control circuit is mounted on the third board, The first capacitor is arranged to be stacked on the second capacitor in a direction substantially perpendicular to the surface of the first substrate. The first capacitor is positioned further away from the third substrate than the second capacitor. Power converter.

10. In the power conversion device according to claim 9, Furthermore, the system includes a second substrate arranged with a surface direction substantially perpendicular to the surface of the first substrate, The first capacitor and the second capacitor are mounted on the second circuit board. Power converter.

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