JP2010057333A - Power supply apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply apparatus which includes a power transformer having a plurality of output units and charges a capacitor in a bootstrap circuit with a voltage output from one of the output units to use the capacitor as a power supply that drives a high-side switching element, and enables initial charging of the bootstrap capacitor without destabilizing an output from the power transformer. <P>SOLUTION: The power supply apparatus includes the bootstrap circuit 14 connected to a high-side drive circuit 15 that drives the high-side switching element 20, and a regulator circuit 13 which is connected between the high-side drive circuit 15 and a first output unit 12a to output a control voltage to the bootstrap circuit 14. The power supply apparatus also includes a current limiting circuit which inhibits the fluctuation of an output voltage from the power transformer 10 due to the fluctuation of the control voltage when the bootstrap capacitor 17 is subjected to initial charging. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes a power transformer having a plurality of output units, and outputs an output voltage from the first output unit of the power transformer to a high-side switching element and a low-side switching element connected in series to a DC power source. The present invention relates to a power supply device used as a power source for driving a high-side drive circuit and a low-side drive circuit.

  2. Description of the Related Art Conventionally, a switching circuit that supplies power to a load connected to the middle point of two switching elements by alternately turning on and off two switching elements connected in series at both ends of a DC power supply by a control signal. Are known. This switching circuit requires a dedicated power source to drive the switching element connected to the high side of the DC power source. In order to create this power supply, it is conventionally known to use a drive circuit using a bootstrap circuit (see, for example, Patent Document 1).

  As a power supply device, there is a 1-transformer multi-output power supply device that extracts at least two outputs from the secondary side of one transformer. Then, two outputs are taken out from one input, and one of the outputs is driven by a power source for driving the switching element connected to the high side and a driving circuit for driving the switching element connected to the low side. There is a power supply configured to be used for the power supply of As shown in FIG. 4, the power supply device has two output units 52 a and 52 b on the secondary side of the power transformer 51, and one output unit 52 a is connected to the input side of the regulator circuit 53. The regulator circuit 53 has an output side connected to the input side of the high side drive circuit 55 and the bootstrap circuit 54. An input capacitor 56 is connected between the output unit 52 a and the regulator circuit 53, and an output capacitor 57 is connected between the regulator circuit 53 and the bootstrap circuit 54.

A high-side switching element 59 and a low-side switching element 60 are connected in series to the DC power supply 58, the high-side switching element 59 is controlled by a high-side drive circuit 55, and the low-side switching element 60 is a low-side drive circuit 61. Controlled by. The bootstrap circuit 54 includes a diode 62 and a bootstrap capacitor 63. One terminal of the bootstrap capacitor 63 is connected to the cathode of the diode 62, and the other terminal is a high-side switching element 59 and a low-side switching element. 60 is connected to the midpoint. The low-side drive circuit 61 is operated the output voltage of the regulator circuit 53 as a power supply, turns on and off the low-side switching element 60 based on a signal VL _IN from a control circuit not shown. High-side drive circuit 55, thereby complementarily turned on and off and the low side switching element 60 the high-side switching element 59 based on a signal VH _IN from a control circuit not shown.

In the power supply device, the bootstrap capacitor 63 is used as a drive power supply for the high-side switching element 59. Therefore, the voltage V _BC of the bootstrap capacitor 63 decreases with time due to energy consumption in the high-side switching element 59. Therefore, in the normal operation, the low side switching element 60 performs the switching operation, so that the bootstrap capacitor 63 is always charged. Since charging at this time has a small load fluctuation, the fluctuation of the control voltage can be suppressed by the presence of the output capacitor 57 (control voltage stabilizing capacitor).
JP 2007-6207 A

However, since the voltage (potential) of the bootstrap capacitor 63 is 0 V in the initial state, the bootstrap capacitor 63 is prior to normal control for complementarily turning on and off the high-side switching element 59 and the low-side switching element 60. Need to be charged. In FIG. 5, when the charging of the bootstrap capacitor 63 is started from the initial state, the voltage V _BC of the bootstrap capacitor 63, the control voltage, the output voltage of the output unit 52a (transformer output A), and the output voltage of the output unit 52b (transformer) Changes in output B) and the like are shown. At this time, unlike the normal operation, since the initial potential of the bootstrap capacitor 63 is 0 V, there is a problem that the control voltage, that is, the input voltage to the bootstrap circuit 54 fluctuates greatly due to the influence of a sudden load fluctuation. . Due to the fluctuation of the control voltage, the voltage of the input capacitor 56 that functions as the output capacitor of the power transformer 51 also fluctuates, and the control system becomes unstable. As a result, there is a problem that even the output voltage of the other output unit 52b of the power transformer 51 varies.

  An object of the present invention is to provide a power supply including a power transformer having a plurality of output units, and charging a capacitor of a bootstrap circuit with a voltage output from one of the output units to drive the capacitor on a high-side switching element. An object of the present invention is to provide a power supply device that can perform initial charging of a bootstrap capacitor without destabilizing the output of a power transformer.

  In order to achieve the above object, the invention according to claim 1 is provided with a power transformer having a plurality of output units, and an output voltage from the first output unit of the power transformer is connected in series to a DC power source. The power supply device is used as a power source for a high-side drive circuit and a low-side drive circuit that drive the high-side switching element and the low-side switching element, respectively. A bootstrap circuit connected to a high-side drive circuit that drives the high-side switching element; and a control voltage connected to the bootstrap circuit between the high-side drive circuit and the first output unit. And a regulator circuit that outputs a signal. In addition, a current limiting circuit is provided that suppresses fluctuations in the output voltage of the power transformer due to fluctuations in the control voltage when the bootstrap capacitor of the bootstrap circuit is initially charged.

  In this invention, when the bootstrap capacitor voltage is maintained from the initial state and the low-side switching element is kept on to charge the bootstrap capacitor, the inrush current flowing in the bootstrap circuit due to the presence of the current limiting circuit is This is smaller than when there is no limit circuit. And since the fluctuation | variation of a control voltage becomes small, the fluctuation | variation of the output voltage of a power transformer is suppressed. Accordingly, it is possible to prevent the electronic device driven by the output of the output unit other than the first output unit of the power transformer, for example, the CPU from being hindered. After the initial charging is completed, normal switching of the two switching elements is started, and the power of the DC power supply is supplied from the middle point of the two switching elements to the load. By providing the current limiting circuit, the initial charging time is lengthened, but there is no problem with the bootstrap capacitor charging in normal switching.

  According to a second aspect of the present invention, in the first aspect of the present invention, the bootstrap circuit includes a bootstrap diode and a bootstrap capacitor connected to the cathode of the bootstrap diode. The bootstrap diode has an anode connected to the output side of the regulator circuit via a resistor, and a junction point between the cathode and the bootstrap capacitor is connected to the high side drive circuit. An input capacitor is connected between the first output section and the input side of the regulator circuit, and an output capacitor is connected between the output side of the regulator circuit and the resistor.

  In the present invention, a stable voltage is supplied to the regulator circuit even if the output of the power transformer is slightly changed due to the presence of the input capacitor, and since the output capacitor is present, the control voltage supplied to the bootstrap circuit is further increased. Stabilize.

  According to the present invention, a power supply including a power transformer having a plurality of output units, and charging a capacitor of a bootstrap circuit with a voltage output from one of the output units to drive the capacitor on a high-side switching element. In the power supply device to be used, the bootstrap capacitor can be initially charged without making the output of the power transformer unstable.

  Hereinafter, the present invention includes a power transformer that extracts two outputs from the secondary side of one transformer, and two switching elements connected in series to a DC power source are connected to the output voltage from the first output section of the power transformer. An embodiment embodied in a power supply device used as a power supply for a drive circuit to be driven will be described with reference to FIGS.

  As shown in FIG. 1A, the power transformer 10 has a primary winding 11a and a secondary winding 11b, and the secondary winding 11b has an intermediate tap 11c. One end of the secondary winding 11b constitutes the first output unit 12a, and the intermediate tap 11c constitutes the second output unit 12b. That is, the power supply apparatus has two output units 12 a and 12 b on the secondary side (secondary winding 11 b) of the power transformer 10.

  The primary winding 11a is intermittently supplied (applied) with a switching operation of a switching element (not shown), and the voltage is output to the first output unit 12a and the second output unit 12b of the secondary winding 11b. The The number of turns on both sides of the intermediate tap 11c of the secondary winding 11b is such that the turn ratio with the primary winding 11a is the output voltage from the first output unit 12a and the second output unit 12b. The predetermined output voltage is required for 12a and 12b.

  The first output unit 12a is connected to the input side of the regulator circuit 13 via a diode D1. The output side of the regulator circuit 13 is connected to the bootstrap circuit 14 via a resistor R. The output side of the regulator circuit 13 is connected to the input sides of the high side drive circuit 15 and the low side drive circuit 21.

  The bootstrap circuit 14 includes a bootstrap diode 16 and a bootstrap capacitor 17 connected to the cathode of the bootstrap diode 16. The bootstrap diode 16 has an anode connected to the output side of the regulator circuit 13 via a resistor R, and a junction between the cathode and one terminal of the bootstrap capacitor 17 connected to the high side drive circuit 15. The other terminal of the bootstrap capacitor 17 is connected to the junction of the high-side switching element 20 and the low-side switching element 22 connected in series to the DC power supply Vcc and the high-side drive circuit 15.

  The second output unit 12b is connected to the output terminal via the diode D2. One terminal of the capacitor C is connected between the cathode of the diode D2 and the output terminal, and the other terminal of the capacitor C is grounded.

  The output terminal of the high-side drive circuit 15 is connected to the control terminal of the high-side switching element 20 out of the two switching elements 20 and 22 connected in series to the DC power supply Vcc. Is connected to the control terminal of the low-side switching element 22. Insulated gate bipolar transistors (IGBT) are used as the switching elements 20 and 22. The collector of the high-side switching element 20 is connected to the DC power source Vcc, the emitter of the high-side switching element 20 and the collector of the low-side switching element 22 are connected, and the collector of the low-side switching element 22 is grounded.

The high side drive circuit 15 and the low side drive circuit 21 are operated using the output voltage of the regulator circuit 13 as a power source. The low side drive circuit 21 turns on and off the low side switching element 22 based on a signal VL _IN from a control device (not shown). The high side drive circuit 15 turns on and off the high side switching element 20 in a complementary manner to the low side switching element 22 based on a signal VH _IN from a control device (not shown).

  As shown in FIG. 2, the regulator circuit 13 includes a switching transistor Q composed of a bipolar transistor, a collector is connected to the input terminal 13 a, and an emitter is connected to the output terminal 13 b via the current limiting circuit 23. In this embodiment, a resistor is used as the current limiting circuit 23. The base of the switching transistor Q is connected to the cathode of the shunt regulator 24, and the anode of the shunt regulator 24 is grounded. The collector and base of the switching transistor Q are connected via a resistor R1. Voltage dividing resistors R2 and R3 are connected to the output side of the current limiting circuit 23, and a voltage divided by the voltage dividing resistors R2 and R3 is applied to the reference of the shunt regulator 24. In order to stabilize the operation of the shunt regulator 24, a capacitor 25 is connected between the cathode of the shunt regulator 24 and the reference.

  When the bootstrap capacitor 17 of the bootstrap circuit 14 is charged from a voltage of 0 V, the resistance value of the resistor constituting the current limiting circuit 23 is in a state where the output voltage of the power transformer 10 varies due to the variation of the control voltage. It is set to a value that suppresses this.

Next, the operation of the power supply device configured as described above will be described.
This power supply device is mounted on a vehicle, for example, and the first output unit 12a is used as a power supply for a control circuit of an inverter device that controls driving of the electric motor, and the second output unit 12b is a control that controls the control circuit. Used as a power source for the device (CPU). Therefore, when a three-phase AC motor is used for the electric motor, as shown in FIG. 1B, a series circuit of three sets of the high-side switching element 20 and the low-side switching element 22 with respect to the DC power supply Vcc is provided. Connected in parallel. The midpoints of the high-side switching element 20 and the low-side switching element 22 of each set are connected to the U-phase, V-phase, and W-phase terminals of the three-phase AC motor 26, respectively. The three high-side switching elements 20 are controlled by separate high-side drive circuits 15, and the three low-side switching elements 22 are controlled by one low-side drive circuit 21. In FIG. 1B, only the high-side drive circuit 15 corresponding to one high-side switching element 20 is shown.

  Each high-side drive circuit 15 operates using a control voltage based on the output voltage of the regulator circuit 13 as a power supply, and controls on / off of the high-side switching element 20. The low-side drive circuit 21 operates using a control voltage based on the output voltage of the regulator circuit 13 as a power source, and controls the low-side switching element 22 on / off. When the three-phase AC motor 26 is operated, the high-side switching element 20 and the low-side switching element 22 of each set are complementarily turned on and off at predetermined intervals, whereby the U of the three-phase AC motor 26 is controlled. Current is supplied to the phase, V phase, and W phase, and the three-phase AC motor 26 is driven.

  In the regulator circuit 13, the switching transistor Q is turned on when the voltage is applied from the first output unit 12 a to the input terminal 13 a and the cathode and the anode of the shunt regulator 24 are not conductive, and the output terminal is turned on. A voltage is output from 13b. In the shunt regulator 24, when the output voltage from the output terminal 13b becomes excessive, the divided voltage by the voltage dividing resistors R2 and R3 becomes higher than the internal reference voltage, and the cathode and the anode are conducted to turn off the switching transistor Q. . Therefore, in the regulator circuit 13, the switching transistor Q is normally held in the ON state. Then, the voltage is input from the input terminal 13a in a state in which the current limiting circuit 23 existing between the emitter of the switching transistor Q and the output terminal 13b is limited as compared with the case where the current limiting circuit 23 is not provided.

The bootstrap capacitor 17 consumes energy when the high-side switching element 20 is driven, and the voltage V _BC decreases. On the other hand, the bootstrap capacitor 17 is charged when the low-side switching element 22 is on. For on-off cycle of the low-side switching element 22 during operation of the 3-phase AC motor 26 is short, the charging is carried out in a state not lower the voltage V _BC bootstrap capacitor 17, since the load fluctuation is small, the output capacitor The presence of 19 (control voltage stabilizing capacitor) suppresses fluctuations in the control voltage.

Meanwhile, in the initial state, the bootstrap the voltage V _BC of the capacitor 17 is in a state close to 0V or 0V, prior to normal control for complementarily turned on and off the high-side switching element 20 and the low-side switching element 22 The bootstrap capacitor 17 is charged. In FIG. 3, when charging of the bootstrap capacitor 17 is started from the initial state, the voltage V _BC of the bootstrap capacitor 17, the charging current, the control voltage, the output voltage (transformer output A) of the first output unit 12 a, and the second The change of the output voltage (transformer output B) of the output part 12b of FIG. A corresponding voltage change or the like when the current limiting circuit 23 is not present is indicated by a two-dot chain line.

  In the initial state, the initial potential of the bootstrap capacitor 17 is 0V or close to 0V. Therefore, unlike the normal operation at the time of charging, if the current limiting circuit 23 does not exist in the regulator circuit 13, a sudden load fluctuation occurs. As a result, the control voltage, that is, the input voltage to the bootstrap circuit 14 varies greatly. Due to the fluctuation of the control voltage, the voltage of the output capacitor 19 of the power transformer 10 also fluctuates, and the control system becomes unstable. As a result, as shown by a two-dot chain line in FIG. 3, even the output voltage of the second output unit 12b of the power transformer 10 varies.

  However, when the current limiting circuit 23 is present, the inrush current flowing through the bootstrap circuit 14 is smaller than when the current limiting circuit 23 is not present. And since the fluctuation | variation of a control voltage becomes small, the fluctuation | variation of the output voltage of the power supply transformer 10 is suppressed. Therefore, it is possible to prevent the electronic device driven by the output of the output unit (second output unit 12b) other than the first output unit 12a of the power transformer 10, such as a CPU, from being hindered. After completion of the initial charging, normal switching of the high-side switching element 20 and the low-side switching element 22 is started, and the power of the DC power source Vcc is supplied to the three-phase AC motor 26 from the midpoint between the switching elements 20 and 22. Although the initial charging time is increased by providing the current limiting circuit 23, there is no problem with the charging of the bootstrap capacitor 17 in normal switching.

According to this embodiment, the following effects can be obtained.
(1) The bootstrap circuit 14 connected to the high-side drive circuit 15 that drives the high-side switching element 20 is connected between the bootstrap circuit 14 and the first output unit 12a. And a regulator circuit 13 for outputting a control voltage. A current limiting circuit 23 is provided that suppresses fluctuations in the output voltage of the power supply transformer 10 due to fluctuations in the control voltage when the bootstrap capacitor 17 of the bootstrap circuit 14 is charged from a voltage of 0 V or close to 0 V. Yes. Therefore, at the time of initial charging of the bootstrap capacitor 17, an electronic device driven by an output unit other than the first output unit 12a of the power transformer 10, that is, the output of the second output unit 12b, such as a CPU, is hindered. It is prevented from coming. In addition, since the charging current can be limited, it is possible to use a resistor with a small rating as the resistor R connected between the regulator circuit 13 and the bootstrap circuit 14.

  (2) The bootstrap circuit 14 includes a bootstrap diode 16 and a bootstrap capacitor 17 connected to the cathode of the bootstrap diode 16. The bootstrap diode 16 has an anode connected to the output side of the regulator circuit 13 via a resistor R, and a junction between the cathode and the bootstrap capacitor 17 connected to the high side drive circuit 15. An input capacitor 18 is connected between the first output unit 12 a and the input side of the regulator circuit 13, and an output capacitor 19 is connected between the output side of the regulator circuit 13 and the resistor R. . Therefore, a stable voltage is supplied to the regulator circuit 13 even if the output of the power transformer 10 varies somewhat due to the presence of the input capacitor 18, and the control supplied to the bootstrap circuit 14 because the output capacitor 19 exists. The voltage becomes more stable.

  (3) The current limiting circuit 23 is configured by a resistor connected to the output terminal 13 b of the regulator circuit 13. That is, the current limiting circuit 23 is incorporated in the regulator circuit 13. Therefore, even if the current limiting circuit 23 is provided, the configuration is simplified.

  (4) The power supply device is used as a power supply device mounted on a vehicle. In recent years, various electric devices are mounted in vehicles, and there are a plurality of power supply voltages. For example, in a vehicle in which traveling wheels are driven by a traveling motor, the power supply voltage for the traveling motor is, for example, about several hundred volts, and the power supply voltage for auxiliary equipment (headlights and wipers) is 12 volts. The power supply voltage of the CPU is several volts. Therefore, since it is difficult to secure a mounting space if a number of batteries corresponding to each power supply voltage are mounted, a power supply device including a power transformer 10 having a plurality of output units is preferable. This embodiment can accommodate such a requirement.

The embodiment is not limited to the above, and may be embodied as follows, for example.
The power supply device is not limited to a power supply device that is used as a power source for the high-side drive circuit 15 and the low-side drive circuit 21 of a three-phase inverter in which the output of the first output unit 12 a includes three sets of switching elements 20 and 22. For example, the power source of the high-side drive circuit 15 and the low-side drive circuit 21 of the inverter having two sets of switching elements 20 and 22, the high-side drive circuit 15 and the low-side drive circuit of one set of switching elements 20 and 22 are not limited to the inverter. You may use as a power supply of 21.

  The power transformer 10 may have a configuration having a plurality of output units, and is not limited to a configuration having two output units, but a configuration having three or more output units, that is, the secondary winding 11b is an output unit. The number of intermediate taps 11c may be one less than the number. For example, a plurality of output units may be provided as power sources for CPUs having different driving voltages.

The high-side switching element 20 and the low-side switching element 22 are not limited to IGBTs, and for example, MOSEFTs or bipolar transistors may be used.
The resistor R existing between the regulator circuit 13 and the bootstrap circuit 14, that is, the resistor R connected to the anode of the bootstrap diode 16 may be omitted.

The current limiting circuit 23 is not limited to a configuration including only a resistor, and may be a configuration combining a resistor and a transistor, for example.
The current limiting circuit 23 may not be built in the regulator circuit 13 but may be externally attached to the output side of the regulator circuit 13.

  ○ Instead of providing a high-side drive circuit 15 corresponding to each high-side switching element 20 as a high-side drive circuit of a three-phase inverter, 3 connected to the control terminals of the three high-side switching elements 20 respectively 3 A high-side drive circuit 15 having a configuration in which a plurality of output terminals are provided and connected to three bootstrap circuits 14 may be used.

○ The power supply device is not limited to a device mounted on a vehicle, and may be applied to a power supply device for household electrical equipment or an electrical equipment power supply device used in a factory.
The following technical idea (invention) can be understood from the embodiment.

(1) In the invention according to claim 1 or 2, the current limiting circuit is incorporated in a regulator circuit.
(2) The power supply device according to any one of claims 1 and 2 and the technical idea (1) is an in-vehicle power supply device.

(A) is a circuit diagram of the power supply device of one Embodiment, (b) is a partial circuit diagram at the time of setting it as the power supply of the control circuit of an inverter apparatus. The circuit diagram of a regulator circuit. The graph which shows a time-dependent change of the bootstrap capacitor voltage at the time of bootstrap capacitor initial charge, charging current, control voltage, etc. The circuit diagram of the power supply device of a prior art. The graph which shows a time-dependent change of the bootstrap capacitor voltage, charging current, control voltage, etc. at the time of the initial charge of the bootstrap capacitor of a prior art.

Explanation of symbols

  R ... resistance, Vcc ... DC power supply, 10 ... power transformer, 12a, 12b ... output unit, 12a ... first output unit, 13 ... regulator circuit, 14 ... bootstrap circuit, 15 ... high side drive circuit, 16 ... boot Strap diode, 17 ... bootstrap capacitor, 18 ... input capacitor, 19 ... output capacitor, 20 ... high-side switching element, 21 ... low-side drive circuit, 22 ... low-side switching element, 23 ... current limiting circuit.

Claims (2)

A high-side switching element including a power transformer having a plurality of output units, and driving a high-side switching element and a low-side switching element connected in series to a DC power source with an output voltage from the first output unit of the power transformer A power supply device used as a power supply for a drive circuit and a low-side drive circuit,
A bootstrap circuit connected to a high side driving circuit for driving the high side switching element;
A regulator circuit connected between the high-side drive circuit and the first output unit and outputting a control voltage to the bootstrap circuit;
A power supply device comprising: a current limiting circuit that suppresses fluctuations in the output voltage of the power transformer due to fluctuations in the control voltage when the bootstrap capacitor of the bootstrap circuit is initially charged.   The bootstrap circuit includes a bootstrap diode and a bootstrap capacitor connected to the cathode of the bootstrap diode, and the anode of the bootstrap diode is connected to the output side of the regulator circuit via a resistor A junction between the cathode and the bootstrap capacitor is connected to the high-side drive circuit, and an input capacitor is connected between the first output section and the input side of the regulator circuit, and the regulator circuit The power supply device according to claim 1, wherein an output capacitor is connected between the output side of the power supply and the resistor.

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