JP2005318686A - Dc/dc converter equipped with snubber circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC/DC converter equipped with a snubber circuit in which the number of parts is reduced and assembling is simplified. <P>SOLUTION: Bus bars 51, 52 for snubbers are individually branched substantially perpendicularly from a bus bar 91 for input side rectifying current energizing and a bus bar 92 for output type rectifying current energizing, individually connected to both terminals of a diode 3. Further, the tip ends of the bus bars 51, 52 for these snubbers are soldered to the terminal holes 111, 112 of a printed board 11. The terminal holes 111, 112 are connected to the snubber circuit 5 through conductive patterns 113, 114. Thus, the snubber circuit 5 can be connected in parallel with the diode 3 by a small wiring impedance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a DC / DC converter having a snubber circuit.

  For example, in the field of electric vehicles such as hybrid vehicles, a dual power supply system combined system of a high-voltage power supply system for driving a vehicle and a conventional low-voltage power supply system for powering an in-vehicle electric device is employed. In this dual power supply system combined method, the power generator supplies the generated power to the high-voltage power supply system. Therefore, a step-down DC / DC converter for the vehicle that supplies power by stepping down DC power from the high-voltage power supply system to the low-voltage power supply system is essential. It has become. This vehicle step-down DC / DC converter has an inverter, a rectifier circuit, and a smoothing circuit in order, like a normal DC / DC converter, and preferably a step-down transformer is provided between the inverter and the rectifier circuit. It is installed. In a step-down DC / DC converter for a vehicle, since the step-down ratio is large and a current flowing through the rectifier element (hereinafter also referred to as a rectified current) becomes a large current, rectification is caused by the influence of wiring inductance connected in series with the rectifier element. A large surge voltage is generated during current switching by the element, and this surge voltage may cause breakdown of the rectifier element. For this reason, for example, as shown in Patent Document 1, it is usual to bypass the rectifier element to bypass the surge voltage, or to provide a snubber circuit to eliminate the accumulated charge in the diode.

  However, in the vehicle step-down DC / DC converter having a large rectified current flowing through the rectifying element as described above, the rectifying element must be fixed to a metal heat radiating plate that is cooled with water or air for cooling the rectifying element. I do not get. On the other hand, a snubber circuit composed of a high-frequency capacitor for small current is mounted on a printed circuit board in the same manner as many other small power circuit components. Therefore, conventionally, it is essential to install a snubber circuit dedicated bus bar in order to connect the terminal of the snubber circuit mounted on the printed circuit board to the terminal of the rectifying element fixed to the heat radiating plate. That is, one end of the snubber circuit bus bar is soldered to the conductive pattern of the printed circuit board to which the snubber circuit terminal is soldered, and the other end of the snubber circuit bus bar is fastened to the rectifier element terminal.

  However, the installation of such a dedicated bus bar for the snubber circuit requires that the rectified current energizing bus bar through which the rectified current of the rectifying device flows and the snubber circuit dedicated bus bar overlap and be fastened together to the rectifying device, which makes the connection work troublesome It was. In addition, the number of parts has increased due to the bus bar dedicated to the snubber circuit.

  The present invention has been made in view of the above problems, and an object thereof is to provide a DC / DC converter having a snubber circuit that can be easily connected and can reduce the number of components.

The present invention includes an inverter that converts input DC power into AC power, a rectifier circuit that includes a rectifier that rectifies the AC power output from the inverter, a smoothing circuit that smoothes the rectified power output from the rectifier circuit, and A control circuit for controlling the inverter; and a snubber circuit having at least one end connected to one main electrode terminal of the rectifying element and bypassing a high-frequency current. The control circuit and the snubber circuit are mounted on a printed circuit board as a low-power circuit component. In a DC / DC converter having a snubber circuit that is mounted, both main electrode terminals of the rectifying element are connected to a rectifying current energizing bus bar, and the rectifying element is fixed to a heat dissipation plate,
The rectified current energizing bus bar has a substrate bonding portion bonded to the snubber circuit conductive pattern of the printed circuit board, and the snubber circuit terminal is bonded to the substrate bonding portion of the rectified current energizing bus bar. It is characterized by being bonded to a conductive pattern for a snubber circuit on a substrate.

  That is, a DC / DC converter having a snubber circuit according to the present invention connects a rectifying element, an input-side inverter (which may include a step-down transformer), and an output-side smoothing circuit to energize a rectified current. The feature is that the rectified current supply bus bar itself is connected to the conductive pattern of the printed circuit board connected to the terminal of the snubber circuit.

  In this way, the conventional snubber circuit bus bar can be omitted, so when the bus bar is fastened to the rectifying element, the rectifying current energizing bus bar and the snubber circuit dedicated bus bar are overlapped and fastened together to the rectifying element. Since no effort is required and the dedicated bus bar for the snubber circuit can be omitted, the number of parts can be reduced, and a DC / DC converter having a snubber circuit with excellent practicality can be provided.

  In a preferred aspect, the snubber circuit is connected in parallel with the rectifier element. In this way, it is possible to reduce the inductance on the rectifying element side viewed from both ends of the snubber circuit, and to reduce the surge voltage applied to the rectifying element. That is, since the snubber circuit can be connected to both terminals of the rectifying element with a minimum wiring distance, the surge voltage generated by the wiring inductance can be favorably bypassed to the snubber circuit.

  In a preferred aspect, the board joint has a terminal that is inserted into a terminal hole of the printed board in contact with the snubber circuit conductive pattern and fixed by solder. In this way, the connection between the rectified current energizing bus bar and the snubber circuit can be completed robustly by slight processing of the rectified current energizing bus bar.

  A preferred embodiment of a DC / DC converter having a snubber circuit of the present invention will be described with reference to the following examples. However, it goes without saying that the technical idea of the present invention may be realized by a combination of other known techniques or equivalent techniques.

  One embodiment of the DC / DC converter having the snubber circuit of this embodiment is shown in the circuit diagram of FIG. Reference numeral 1 is an inverter circuit, 2 is a step-down transformer for full-wave rectification, 3 is a diode (rectifier element), 5 and 6 are snubber circuits, and 7 is a smoothing circuit. The inverter circuit 1 converts an input high voltage from a high-voltage power supply system of a vehicle into an AC voltage and applies it to the primary coil of the step-down transformer 2. A secondary voltage is applied to 4 individually. The voltage subjected to single-phase full-wave rectification by the diodes 3 and 4 is smoothed by the smoothing circuit 7 and output to the low-voltage power supply system of the vehicle as an output low voltage. The snubber circuits 5 and 6 discharge the accumulated charges of the diodes 3 and 4 and absorb the switching surge voltage applied to the diodes 3 and 4. The smoothing circuit 7 includes a choke coil and a smoothing capacitor disposed between the output side of the choke coil and the ground, and smoothes the rectified current. In FIG. 1, an inverter circuit 1 and a step-down transformer 2 constitute an inverter according to the present invention, and diodes 3 and 4 individually constitute a rectifier element according to the present invention, and constitute a rectifier circuit 8 according to the present invention as a whole. doing. The rectifying element may be a transistor that performs synchronous rectification instead of a diode, and various known DC / DC converter circuit systems other than the rectifying system shown in FIG. 1 may be employed.

  In FIG. 1, the rectifier circuit 8 connects the input side rectified current energizing bus bar 91 that connects the secondary coil 21 of the step-down transformer 2 and the anode terminal of the diode 3, and the cathode terminal of the diode 3 and the input terminal of the smoothing circuit 7. The output side rectified current energizing bus bar 92, the input side rectified current energizing bus bar 93 connecting the secondary coil 22 of the step-down transformer 2 and the anode terminal of the diode 4, the cathode terminal of the diode 4 and the input terminal of the smoothing circuit 7 are connected. The output side rectified current energizing bus bar 94 is connected. The snubber circuit 5 has snubber bus bars 51 and 52 for connecting both ends thereof to both ends of the diode 3, and the snubber circuit 6 is a snubber bus bars 61 and 62 for connecting both ends thereof to both ends of the diode 4. have.

  The feature of this embodiment is that the input side rectified current energizing bus bar 91 and the snubber bus bar 51 are integrated, the output side rectified current energizing bus bar 92 and the snubber bus bar 52 are integrated, and the input side rectified current energizing bus bar. 93 and the snubber bus bar 61 are integrated, and the output side rectified current energizing bus bar 94 and the snubber bus bar 64 are integrated. The bus bar dedicated to the snubber circuit, which is necessary in the past and has not been easy to perform the fastening operation, can be omitted.

  As an example, refer to FIGS. 2 to 4 for the shape and spatial arrangement of the input side rectified current energizing bus bar 91 and snubber bus bar 51, and the integrated output side rectified current energizing bus bar 92 and snubber bus bar 52. To explain.

  In FIG. 2, reference numeral 10 denotes a heat radiating plate. A diode 3 is placed on the boss portion and fixed by solder. A printed circuit board 11 is disposed above the heat radiating plate 10 in parallel with the heat radiating plate 10. The printed circuit board 11 is placed on a boss (not shown) of the heat radiating plate 10 and fastened in the same manner as described above. . On the printed circuit board 11, a control circuit for controlling the inverter circuit 1, a constant voltage circuit for forming the power supply power, and the like are mounted together with the snubber circuits 5 and 6.

  An opening 110 is formed in the printed board 11, and the diode 3 is disposed in the opening 110. An anode terminal 31 and a cathode terminal 32 protrude in an L shape from the opening 110 on the top surface of the diode 3. The anode terminal 31 has a bus bar 91 for energizing an input side rectified current, and the cathode terminal 32 has an output side. A rectification current energizing bus bar 92 is fastened by screws 33 and 34.

  The snubber bus bar 51 from the input-side rectified current energizing bus bar 91 and the snubber bus bar 52 from the output-side rectified current energizing bus bar 92 branch substantially at right angles and parallel to the printed circuit board 11. The snubber bus bars 51 and 52 referred to in this embodiment constitute the substrate bonding portion referred to in the present invention.

  A plan view of FIG. 2 is shown in FIG. In the printed circuit board 11, the shape and space arrangement of the snubber bus bar 52 in the vicinity of the diode 3 will be described with reference to FIGS. In FIG. 2, the tip end portion of the snubber bus bar 51 branched from the input side input side rectified current energizing bus bar 91 is bent at a right angle and inserted into the terminal hole 111 of the printed circuit board 11. The end portion of the snubber bus bar 52 branched from 92 is bent at a right angle and inserted into the terminal hole 112 of the printed circuit board 11.

  On the surface of the printed board 11, a snubber circuit conductive pattern 113 is formed surrounding the terminal hole 111, and a snubber circuit conductive pattern 114 is also formed surrounding the terminal hole 112.

  The pair of terminals formed on both sides of the lower surface of the snubber circuit 5 are individually soldered to the snubber circuit conductive patterns 113 and 114. Of course, it is possible to provide the snubber circuit 5 with a terminal to be inserted into the terminal hole and solder it from the back side of the printed circuit board 11. Thereby, the snubber circuit 5 is connected in parallel with the diode 3 by a short wiring, a small wiring resistance and a wiring inductance. That is, the snubber circuit 5 is arranged adjacent to the diode 3 and can be connected in parallel to the integrated bus bars 91 and 51 as well as the integrated bus bars 92 and 52 with a smaller wiring impedance. FIG. 4 is a side sectional view of FIG.

By doing in this way, the inductance of the diode 3 seen from both ends of the snubber circuit 5 can be reduced, and the application of the surge voltage to the diode 3 can be satisfactorily prevented. Further, the end portions of the snubber bus bars 51 and 52 as the board joint portions constitute terminals that are inserted into the terminal holes 111 and 112 of the printed board 11 in contact with the snubber circuit conductive patterns 113 and 114 and fixed by solder. ing. For this reason, the connection between the rectified current energizing bus bar and the snubber circuit can be completed with a slight amount of processing on the rectified current energizing bus bars 91 and 92.
(Modification)
In the above embodiment, the snubber circuits 5 and 6 are connected in parallel to the diodes 3 and 4. However, the snubber circuits 5 and 6 may have other circuit configurations.

1 is a circuit diagram of a DC / DC converter having a snubber circuit according to Embodiment 1. FIG. It is a principal part longitudinal cross-sectional view of the DC / DC converter which has the snubber circuit of FIG. It is a principal part top view of FIG. It is a principal part longitudinal cross-sectional view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter circuit 2 Step-down transformer 3 Diode 4 Diode 5 Snubber circuit 6 Snubber circuit 7 Smoothing circuit 8 Rectifier circuit 10 Heat dissipation plate 11 Printed circuit board 21 Secondary coil 22 Secondary coil 31 Anode terminal 32 Cathode terminal 51 Snubber bus bar 52 For snubber Bus bar 61 Snubber bus bar 62 Snubber bus bar 91 Input side rectified current energizing bus bar 92 Output side rectified current energizing bus bar 93 Input side rectified current energizing bus bar 94 Output side rectified current energizing bus bar 110 Opening 111 Terminal hole 112 Terminal hole 113 Snubber circuit conductive pattern 114 Snubber circuit conductive pattern

Claims (3)

An inverter that converts input DC power into AC power; a rectifier circuit that rectifies the AC power output from the inverter; a smoothing circuit that smoothes the rectified power output from the rectifier circuit; and the inverter is controlled And a snubber circuit having at least one end connected to one main electrode terminal of the rectifying element and bypassing a high-frequency current, the control circuit and the snubber circuit are mounted on a printed circuit board as a low-power circuit component, Both main electrode terminals of the rectifying element are connected to a rectifying current energizing bus bar, and the rectifying element is a DC / DC converter having a snubber circuit fixed to a heat radiating plate.
The rectified current energizing bus bar has a substrate bonding portion bonded to the conductive pattern for the snubber circuit of the printed circuit board,
A DC / DC converter having a snubber circuit, characterized in that a terminal of the snubber circuit is joined to a conductive pattern for a snubber circuit of the printed circuit board which is joined to the board joint portion of the rectified current energizing bus bar. A DC / DC converter having the snubber circuit according to claim 1.
The snubber circuit is connected in parallel with the rectifying element, and is a DC / DC converter. A DC / DC converter having the snubber circuit according to claim 2.
The substrate junction is
A DC / DC converter having a snubber circuit, comprising a terminal inserted into a terminal hole of the printed circuit board in contact with the conductive pattern for the snubber circuit and fixed by solder.

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