JP2010193593A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance insulation performance between a capacitor and a pattern on a printed wiring board, in a power converter with a capacitor mounting board, and to reduce inductance of wiring. <P>SOLUTION: The power converter includes a DC link part that connects a rectifier with an inverter. The DC link part includes a printed wiring board 1 with a smoothing circuit constituted by connecting a plurality of capacitors 2 in series and in parallel. The printed wiring board includes: a negative electrode pattern N which constitutes the negative electrode of the DC link part, on the topside of an insulating board; a positive electrode pattern P which constitutes the positive electrode of the DC link part; and an intermediate electrode pattern C which is arranged adjacent to the positive electrode pattern and constitutes the intermediate connection electrode of the capacitor connected in series. The negative electrode pattern is formed only on the plane of projection of the capacitor that is connected to the negative electrode side of the DC link part among the capacitors connected in series. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power conversion device, and more particularly to a mounting structure of a smoothing capacitor disposed in a DC link portion.

  Patent Documents 1 and 2 are known as mounting structures for capacitors disposed in a DC link unit in a power converter including a DC link unit that connects a rectifying unit and an inverter unit. In the servo amplifier described in Patent Document 1 and the inverter device described in Patent Document 2, the wiring impedance is reduced by arranging a plurality of small capacitors on a conductive plate such as a printed circuit board, and A technique for realizing miniaturization is shown.

JP 2003-219661 A JP 2006-197735 A

  An electrolytic capacitor is widely used as a smoothing capacitor installed in a DC link portion of a power converter. In particular, a substrate self-supporting type aluminum electrolytic capacitor is used as a capacitor mounted on a conductive plate such as a printed circuit board. However, the substrate self-supporting type aluminum electrolytic capacitor may have the same potential as the negative electrode because the aluminum frame is connected to the negative electrode. The frame surface of the aluminum electrolytic capacitor is coated for printing, but this coating is not intended for insulation, so there is a risk that the frame surface will be exposed due to scratches caused by contact, age deterioration, etc. is there.

  In addition, the printed circuit board is coated to prevent rusting of the wiring pattern, but this is not intended for insulation, and the frame due to scratches, aging, etc., similar to the coating of the aluminum electrolytic capacitor frame. The surface may be exposed. Therefore, it is necessary to pay attention to ensuring insulation between the aluminum frame of the substrate self-supporting aluminum electrolytic capacitor and the wiring pattern of the printed circuit board. In particular, when the potential of the DC link portion of the power converter becomes high, a capacitor is connected in series from the viewpoint of withstand voltage, but the positive electrode of one capacitor and the negative electrode of the other capacitor are connected. Each aluminum frame has a different potential. In such a case, the substrate pattern becomes complicated.

  In order to solve such a problem, Patent Document 1 attempts to insulate the conductive plate from the electrolytic capacitor by covering the surface of the conductor plate with an insulator. For the insulation, a method of molding with a resin or the like, or a method of laying an insulating sheet or the like is adopted, but an increase in man-hours and an increase in cost are inevitable.

  Patent Document 2 describes an example in which a plurality of capacitors are arranged on a printed wiring board. In general, in a printed wiring board mounted with a capacitor, wiring inductance can be greatly reduced by stacking patterns. However, Patent Document 2 does not mention insulation treatment between the printed wiring board pattern and the electrolytic capacitor.

  The present invention has been made in view of such problems. In a power conversion device using a capacitor mounting board in which a plurality of capacitors are arranged on a printed wiring board, the insulation performance between the capacitor and the printed wiring board pattern is improved. An object of the present invention is to provide a power conversion device that can be increased and realize low wiring inductance.

  In order to solve the above problems, the present invention employs the following means.

  A rectification unit that converts the supplied AC power into DC power by opening and closing the switching elements inserted in each phase, and converts the converted DC power into AC power by opening and closing the switching elements inserted in each phase. In a power conversion device including an inverter unit that supplies a load, and a DC link unit that connects the rectifier unit and the inverter unit, the DC link unit includes a smoothing circuit formed by connecting a plurality of capacitors in series and in parallel. A printed wiring board, the printed wiring board having a negative electrode pattern constituting the negative electrode of the DC link part on the upper surface side of the insulating substrate, and a positive electrode pattern constituting the positive electrode of the DC link part on the lower surface side of the insulating substrate; And an intermediate electrode pattern that constitutes an intermediate connection electrode of the capacitor that is juxtaposed to the positive electrode pattern and connected in series, the negative electrode pattern, Serial of series connected capacitors are formed only on the projection surface of the capacitor connected to the negative electrode side of the DC link section.

  Since the present invention has the above configuration, it is possible to improve the insulation performance between the capacitor and the printed wiring board on which the capacitor is mounted, and to realize a reduction in wiring inductance.

It is a figure explaining the power converter device concerning the embodiment of the present invention. It is a side view (arrow view) of FIG. It is a circuit diagram of the printed wiring board shown in FIG. FIG. 3 is an enlarged view of a part (dotted line part) of FIG. 2. It is a figure which shows the simulation result of the electric current distribution in the pattern of the printed wiring board shown in FIG. It is a figure which shows the simulation result of the current distribution in the pattern of the wiring conductor shown in FIG. It is a figure explaining the conventional printed wiring board. It is a figure explaining the example of the wiring conductor pattern in the conventional printed wiring board.

  Hereinafter, the best embodiment will be described with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a power conversion device according to an embodiment of the present invention. As shown in the figure, a printed wiring board (capacitor board) 1 mounted with a capacitor includes capacitors 2p1 to 2p8, 2n1 to 2n8 mounted on the printed wiring board, switching elements 3R, 3S, 3T on the PWM rectifier side, and Inverter side switching elements 3U, 3V, 3W are provided.

  2 is a side view (arrow view) of the printed wiring board of FIG. 1 as viewed from the direction of the arrow (A). As shown in FIG. 2, the P-side wiring conductor is disposed between the printed wiring board 1 and the switching element. 4P and the N side wiring conductor 4N are arranged.

  FIG. 3 is a circuit diagram of the printed wiring board shown in FIG. 1. The switching elements 3R, 3S, and 3T on the rectifier side and the switching elements 3U, 3V, and 3W on the inverter side are connected via a DC link portion. The positive pole side (P side) of the DC link part is connected to the P pole pattern and the P side wiring conductor 4P of the printed wiring board 1, and the negative pole side (N side) of the DC link part is the N pole pattern of the printed wiring board 1 and It is connected to the N-side wiring conductor 4N.

  Capacitors 2p1 to 2p8 and 2n1 to 2n8 are assumed to have a large voltage value at the DC link portion. Capacitor 2p1 and capacitor 2n1, capacitor 2p2 and capacitor 2n2,. And the negative electrode side are connected in series to ensure a withstand voltage. Furthermore, the capacitance is ensured by connecting a plurality of capacitors in parallel (the first embodiment of FIG. 1 has a configuration of two series and eight parallel). The intermediate points of the capacitors connected in series are connected to the intermediate point pattern (C pole pattern) of the printed wiring board 1.

  By using a large number of small capacitors and connecting them in series and parallel, the height per capacitor (the length in the direction perpendicular to the paper surface in FIG. 1) can be reduced. In addition, since the weight of the single body can be reduced, the supporting portion of the capacitor can be simplified.

  The switching elements 3R, 3S, 3T on the rectifier side and the switching elements 3U, 3V, 3W on the inverter side use so-called 2in1 type elements in which two switching elements are mounted in one device as shown in FIG. As shown in FIG. 1, they are arranged symmetrically with respect to the center of the printed wiring board 1.

  In a 2-in-1 type element, there are generally a collector terminal (terminal connected to the positive electrode (P) side), an emitter terminal (terminal connected to the negative electrode (N) side), and an AC side terminal. In the example of FIG. 1, an element in which the terminal on the center side of the substrate is a collector connection terminal, the middle terminal is an emitter terminal, and the terminal on the outside of the substrate is an AC side terminal is taken as an example. By arranging the switching element as shown in FIG. 1, a cooling device such as a heat sink or a heat pipe (not shown) connected to the bottom of the switching element of the PWM rectifier and the inverter can be used in common. Has the effect of Furthermore, when switching the switching element, it is only necessary to connect the switching element to the terminal portion of the printed wiring board on which the capacitor is mounted, which is effective in reducing the number of man-hours for the replacement work. Note that the printed wiring board 1 shown in FIG. 1 is composed of a double-sided board using the front and back surfaces.

  FIG. 4 is an enlarged view of a dotted line portion of FIG. In the printed wiring board, the wiring pattern (shaded portion) on the capacitor side surface (upper side surface of the printed wiring board 1 in FIG. 2) is an N-pole pattern on the N side of the DC link portion. In addition, no wiring pattern is provided below the capacitors 2p1 to 2p8, and the substrate surface of the substrate (resin surface on which no conductor pattern is formed) is exposed.

  This is because insulation between the capacitor frame and the wiring pattern of the printed wiring board 1 can be secured even when a substrate self-standing electrolytic capacitor in which the aluminum frame of the capacitor is connected to the negative electrode is used as the capacitor. . That is, in the example of FIG. 1, since the negative electrodes of the capacitors 2n1 to 2n8 are at the same potential as the N-side pattern, no potential difference occurs between the aluminum frame and the N-side pattern, but the negative electrodes of the capacitors 2p1 to 2p8 are the capacitor Since it is connected to the positive electrodes 2n1 to 2n8, a potential difference is generated between the aluminum frame of the capacitors 2p1 to 2p8 and the N-side pattern by the potential of the capacitors 2n1 to 2n8.

  The frame surface of the aluminum electrolytic capacitor is coated for printing, but this is not intended for insulation, so there is a risk that the frame surface will be exposed due to scratches caused by contact or deterioration over time. . Also, the printed circuit board is coated to prevent rusting of the wiring pattern, but since this is not intended for insulation, the frame surface may be damaged or deteriorated over time, as with the capacitor frame coating. There is a risk of exposure.

  Conventionally, as in the case of the substrate surface shown in FIG. 7, an insulator 5 such as an insulating plate or an insulating sheet is inserted in order to ensure insulation. However, as shown in FIG. 1, a wiring pattern is not provided under the capacitors 2p1 to 2p8 on the surface on which the capacitor 2 is arranged, and insulation is ensured without inserting an insulator by exposing the fabric surface of the substrate. can do.

  However, with this configuration, since there is no pattern below the capacitors 2p1 to 2p8 on the capacitor side surface, the positive electrode layer (P electrode pattern), the intermediate electrode layer (C electrode pattern), and the negative electrode layer (N electrode pattern) ) And the wiring pattern stacking effect can hardly be expected. Note that the stacking effect is an effect that currents flow in opposite directions between the stacked wiring patterns so that magnetic fluxes generated by the respective currents cancel each other and the inductance of the wiring path can be reduced. .

  For this reason, when the printed wiring board 1 shown in FIG. 1 is used alone, the inductance of the wiring path cannot be ignored. As a result, for example, when the U-phase switching element 3U performs switching, the charging / discharging path of the nearby capacitor 2p1 and capacitor 2n1 has a low impedance because the wiring path is short. On the other hand, the charging / discharging path of the capacitor 2p8 and the capacitor 2n8 has a high impedance because the wiring path is long. For this reason, a large variation occurs in the amount of current flowing into and out of the capacitor (the amount of charge supplied), which may lead to a reduction in the life or destruction of the capacitor.

  Therefore, in the example of FIG. 1, the P-side wiring conductor 4P and the N-side wiring conductor 4N are arranged between the printed wiring board 1 and the switching element. The P-side wiring conductor 4P and the N-side wiring conductor 4N are disposed close to each other via an insulator (not shown) and the like, and the inductance of the wiring path is reduced by the above-described stacking effect.

  In other words, as in the example of FIG. 1, the printed wiring board 1, the P-side wiring conductor 4P, and the N-side wiring conductor 4N are electrically connected in parallel, so that any switching element can be switched. The majority of the current flowing in and out of the capacitor is once passed through the terminal portion of the switching element closest to each capacitor and then switched to the element switched through the P-side wiring conductor 4P and the N-side wiring conductor 4N having a small wiring inductance. Inflow and outflow. As a result, variation in the amount of current flowing in and out of each capacitor is reduced, and there is an effect that adverse effects such as a decrease in the lifetime of the capacitor can be suppressed.

  FIG. 5 is a diagram showing a pattern diagram of the printed wiring board 1 and a simulation result of current distribution in the example of FIG. Here, FIG. 5A is a pattern diagram of the capacitor side surface of the printed wiring board 1 (the upper side surface of the printed wiring board 1 in FIG. 2), and is configured by only the N-pole pattern. Further, dotted circles in the figure are projected portions of the capacitors 2p1 to 2p8 and 2n1 to 2n8.

  On the capacitor side surface of the printed wiring board 1, the projection surface of the capacitors 2p1 to 2p8 connected to the P side of the DC link has no N-pole pattern, and is a fabric surface (insulator surface on which no conductor pattern is formed) of the printed circuit board. Further, the projection surface of the capacitors 2n1 to 2n8 connected to the N side of the DC link has a structure in which an N pole pattern or a part of the N pole pattern is laid, and the negative terminals of the capacitors 2n1 to 2n8 are N pole patterns. Connected.

  FIG. 5B is a pattern diagram of the surface of the printed wiring board on the side of the switch element (the lower surface of the printed wiring board 1 in FIG. 2), which is composed of a C-pole pattern and a P-pole pattern. Separated while maintaining an insulation distance. The positive electrode terminals of the capacitors 2n1 to 2n8 and the negative electrode terminals of the capacitors 2p1 to 2p8 are connected to the C pole pattern, and the capacitors 2p1 to 2p8 are connected to the P pole pattern.

  5 (a) and 5 (b), the line drawn on the substrate surface assumes the switching of the U-phase switching element 3U, that is, the current distribution seen from between the U-phase element emitter terminal and the U-phase element collector terminal, that is, the capacitor The distribution of current supplied from 2p1 to 2p8 and 2n1 to 2n8 is calculated by electromagnetic field simulation.

  That is, the portion where the distance between the lines is narrow indicates that the current density is high. Further, as shown in FIGS. 5A and 5B, the currents flowing into and out of the capacitors 2p1 to 2p8 and 2n1 to 2n8 are substantially uniform although the currents of the capacitors 2p1 and 2n1 close to the U-phase switching element 3U are slightly larger. It can be seen that 5A and 5B are simulation results in a transient state immediately after switching, and as a result, the uniformity is further increased when a steady state is obtained with time. 5A and 5B, the current flowing into and out of the capacitors 2p1 to 2p8 and 2n1 to 2n8 is the terminal of the element closest to each capacitor in spite of the switching of the U-phase switching element 3U. Can be confirmed.

  FIG. 6 is a diagram illustrating a wiring conductor pattern diagram and a current distribution simulation result in the example of FIG. 1. 6A is a diagram showing the N-side wiring conductor 4N in FIG. 1, and FIG. 6B is a diagram showing the P-side wiring conductor 4P in FIG.

  The respective wiring conductors 4N and 4P are laminated close to each other. In particular, when the P-side wiring conductor 4P is projected onto the N-side wiring conductor 4N, most of the wiring conductors overlap. In addition, in the central part of each wiring conductor, each conductor part is completely laminated.

  As shown in FIGS. 6 (a) and 6 (b), the current flowing in and out from the terminals of each element (current flowing in and out from the printed wiring board in FIG. 5) passes through the laminated portion in the central portion and is a U-phase switching element 3U. Flowing into. Since the currents in the laminated portions of the respective conductor substrates flow in opposite directions, the generated magnetic flux is canceled out and the inductance can be reduced.

  That is, the factor that the current flowing into and out of the capacitors 2p1 to 2p8 and 2n1 to 2n8 in FIG. 5 flows to the terminal of the nearest element is also the effect that the inductance of the conductor substrate is extremely small, and the low inductance in the conductor substrate is reduced. It can be said that it contributes to equalization of the current flowing through each capacitor. As a result, excessive current concentration on a specific capacitor can be prevented, and the life of the capacitor can be extended.

  In addition, since only the structure of the printed wiring board shown in FIG. 5 does not provide a pattern stacking effect, the inductance of the path becomes large in the capacitor located away from the switching element. However, in the structure using the laminated wiring conductors shown in FIG. 6, the inductance can be reduced by the path passing through the nearest element terminal.

  As a result, it is possible to suppress the jumping voltage phenomenon that occurs when switching the element due to the energy accumulated in the inductance. For this reason, there is an effect that the snubber circuit connected for protection can be reduced. This effect is because when the printed wiring board 1 has a laminating effect itself as in the prior art of FIG. 7, the current can flow through the pattern of the printed wiring board 1 through a low inductance path. Low inductance can be achieved. In such a case, unlike the example of the wiring conductor pattern in the prior art shown in FIG. 8, it is not necessary to give the wiring conductor a lamination effect, and only a low-frequency current component (main current component) flows.

  That is, the present invention is characterized by simplifying the insulation between the printed wiring board and the capacitor frame and reducing the insulation for securing the insulation. Further, the example of FIG. 1 is also characterized in that a low-frequency current component (main current component) and a high-frequency current component that flows into the capacitor and is influenced by inductance flow through the wiring conductor.

  In addition, the N-side wiring conductor in FIG. 6A is provided with a current path that connects the left and right ends at the end in the vertical direction (longitudinal direction) of the wiring conductor, so that current can be introduced into the U-phase switch element. It has a different form. Thereby, the current concentration near the element terminal can be relaxed. Further, FIG. 6B also has an effect that the laminated portion with the P-side wiring conductor can be enlarged by extending the vertical direction (longitudinal direction) of the wiring conductor, and the inductance can be further reduced.

  In FIG. 5, the configuration implemented on the double-sided board is described as an example, but there is an N-pole pattern on the capacitor side surface of the printed wiring board, and at least a part of the pattern is on the N side of the DC link. It is important that the capacitor is located only under the connected capacitors 2n1 to 2n8, and it goes without saying that a multilayer substrate that satisfies this condition may be used as a printed wiring board. In FIG. 6, the P-pole wiring conductor is narrower in the lateral direction than the N-pole wiring conductor. However, it is important to increase the area of the overlapping portion by stacking. Needless to say, the wiring conductor may have a shape in which a hole is provided in the wiring conductor so as to have the same size as the N-pole wiring conductor. Furthermore, in the example of FIG. 1, a system using a PWM rectifier and an inverter is assumed. However, since a smoothing capacitor is connected in series is one of the features of the present invention, instead of the PWM rectifier. Needless to say, the same effect can be obtained even when a diode rectifier or a DC power supply is used.

  As described above, according to the embodiment of the present invention, the printed wiring board includes a plurality of small capacitors mounted on the printed wiring board and a wiring conductor having a laminated structure. The wiring pattern is configured to be the N pole pattern of the DC link of the power converter, and the main wiring pattern on the side surface of the element is the P pole pattern of the DC link and the intermediate point pattern (C pole pattern) of the capacitors connected in series. Configure as follows. Further, the wiring pattern on the side surface of the capacitor does not exist in the lower part of the capacitor connected to the P side of the DC link, and the wiring conductor having a laminated structure is arranged in parallel with the printed wiring board. Thus, since the wiring conductor has a laminated configuration, the current flowing in and out of the capacitor flows to the wiring conductor via the element terminal near the capacitor, and the inductance can be reduced. As described above, the insulation performance between the capacitor and the printed wiring board pattern on which the capacitor is mounted can be improved to reduce the insulation for ensuring insulation, and the inductance of the wiring path can be reduced.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

1 Printed wiring board with capacitor (capacitor board)
2p1 to 2p8 Capacitors 2n1 to 2n8 connected to the P side of the DC link Capacitors 3R R phase switching element 3S S phase switching element 3T T phase switching element 3U U phase switching element 3V V phase switching Element 3W W-phase switching element 4P P-side wiring conductor 4N N-side wiring conductor 5 Insulator

Claims (6)

A rectifier that opens and closes the switching elements inserted in each phase to convert the supplied AC power into DC power, and converts the converted DC power into AC power by opening and closing the switching elements inserted in each phase. In a power conversion device including an inverter unit that supplies a load, and a DC link unit that connects the rectifier unit and the inverter unit,
The DC link portion includes a printed wiring board equipped with a smoothing circuit formed by connecting a plurality of capacitors in series and in parallel,
The printed wiring board has a negative electrode pattern constituting the negative electrode of the DC link part on the upper surface side of the insulating substrate, and a positive electrode pattern constituting the positive electrode of the DC link part on the lower surface side of the insulating substrate and the positive electrode pattern. An intermediate electrode pattern constituting intermediate connection electrodes of the capacitors connected in series,
The power converter according to claim 1, wherein the negative electrode pattern is formed only on a projection surface of a capacitor connected to the negative electrode side of the DC link portion among the capacitors connected in series. A rectifier that opens and closes the switching elements inserted in each phase to convert the supplied AC power into DC power, and converts the converted DC power into AC power by opening and closing the switching elements inserted in each phase. In a power conversion device including an inverter unit that supplies a load, and a DC link unit that connects the rectifier unit and the inverter unit,
The DC link unit is a printed wiring board equipped with a smoothing circuit formed by connecting a plurality of capacitors in series and in parallel;
A P-side wiring conductor connecting between the positive terminals of the switching elements constituting the rectifying unit and the inverter part and an N-side wiring conductor connecting between the negative terminals of the switching elements constituting the rectifying part and the inverter part,
The printed wiring board is arranged in parallel with the negative electrode pattern constituting the negative electrode of the DC link portion on the upper surface side of the insulating substrate, and the positive electrode pattern constituting the positive electrode of the DC link portion on the lower surface side of the insulating substrate and the positive electrode pattern. An intermediate electrode pattern constituting intermediate connection electrodes of the capacitors connected in series,
The negative electrode pattern is formed only on the projection surface of the capacitor connected to the negative electrode side of the DC link portion among the capacitors connected in series, and connected to the P-side wiring conductor plate and the negative electrode pattern connected to the positive electrode pattern. An N-side wiring conductor plate that is laminated and disposed so that one of the N-side wiring conductor plates overlaps the projection surface. The power conversion device according to claim 1,
The printed wiring board has a double-sided board structure, the capacitor that divides the DC potential has a two-series configuration, and the main wiring pattern on the capacitor side substrate surface of the printed wiring board has the same potential as the negative electrode side of the DC potential, The main wiring pattern on the other surface of the printed wiring board is a pattern having the same potential as the positive electrode side of the DC potential and a pattern having the same potential as the midpoint of the DC potential. The power conversion device according to claim 1,
The semiconductor device operating as the inverter unit and the rectifying unit has a configuration in which two semiconductor switches are provided in a single device, and the inverter unit is symmetrical with respect to the center of the printed wiring board on which the plurality of capacitors are mounted. A semiconductor device that operates as a semiconductor device that operates as the rectifying unit, and a capacitor that is connected to the negative electrode side of the DC potential among the capacitors that are divided and connected is disposed at an end of the printed wiring board, The power converter according to claim 1, wherein the capacitor connected to the positive electrode side of the DC potential is disposed in the center of the printed wiring board. The power conversion device according to claim 1,
A semiconductor device that operates as an inverter unit and a semiconductor device that operates as a rectifying unit are configured to include two semiconductor switches in a single device, and the center of the printed wiring board on which the plurality of capacitors are mounted. The semiconductor device that operates as the inverter unit and the semiconductor device that operates as the rectifying unit are arranged in line symmetry, and are respectively connected to the positive electrode and the negative electrode in the link unit between the rectifying unit and the inverter unit A wiring conductor is disposed between the printed wiring board and the semiconductor device, connected to the semiconductor device in the vicinity of each end of the wiring conductor, and a central portion of each wiring conductor is laminated. A power conversion device characterized by that. The power conversion device according to claim 1,
The wiring conductors connected to the positive electrode and the negative electrode of the link part between the rectifying part and the inverter part are laminated to each other, and at least one of the wiring conductors is rectangular on the surface facing each other, and the rectangular side A terminal connected to the semiconductor device operating as an inverter is provided near the end of one long side, and a terminal connected to the semiconductor device operating as a rectifying unit is provided near the end of the other long side. And the path | route which can electrically connect a rectification | straightening part and an inverter part is provided in the edge part side rather than the terminal provided in the rectangular short side among the said terminals, The power converter device characterized by the above-mentioned.

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