JP5382535B2 - Power supply device for gate drive circuit - Google Patents

Description

  The present invention relates to a power supply device for a gate drive circuit that drives a power semiconductor switch element of a power conversion circuit, and more particularly to a self-feeding power supply device that diverts the energy of a snubber capacitor as the power supply for the gate drive circuit.

In many cases, a so-called snubber circuit is used in combination with the power semiconductor switching element constituting the power conversion circuit. Patent Documents 1 and 2 describe the configuration of a power supply device that uses the discharge energy of the snubber circuit as energy for operating the gate drive circuit of the power semiconductor switch element.
The power supply device is provided with a power supply capacitor for charging the discharge energy, and a terminal voltage of the power supply capacitor is supplied to the gate drive circuit as a power supply voltage.

Japanese Patent No. 3133166 JP-A-6-98553

At the time when the power switch is turned on and the main power supply is connected to the power conversion circuit, the power supply capacitor is in an uncharged state. In this state, since the power supply voltage is not applied to the gate drive circuit, the gate drive circuit does not operate.
Therefore, conventionally, an initial charging circuit for charging the power supply capacitor when the power switch is turned on is provided. Since this initial charging circuit is configured to cause a charging current to flow from the main power supply to the power supply capacitor when the power switch is turned on, a plurality of high-power resistors are used as its constituent elements. It is provided for each of a plurality of power semiconductor switch elements constituting the conversion circuit.
The high power resistor is expensive and large in shape. Therefore, in the conventional power supply device including the initial charging circuit, the initial charging circuit is a factor that hinders cost reduction and downsizing.

    Therefore, an object of the present invention is to provide a power supply device for a gate drive circuit that does not require an initial charging circuit.

  The present invention is a power supply device for a gate drive circuit for driving a power semiconductor switch element of a power conversion circuit, and in order to solve the above problems, a snubber diode and a snubber connected in parallel to the power semiconductor switch element A series circuit composed of a capacitor, a power supply capacitor that applies a terminal voltage as a power supply voltage to the gate drive circuit, a positive potential side terminal of the snubber capacitor and a positive potential side terminal of the power supply capacitor, A normally-on type switch element that supplies a charging current to the power supply capacitor; and a switch control circuit that controls the normally-on type switch element. The switch control circuit is configured to turn off the normally-on type switch element when a terminal voltage of the power supply capacitor becomes equal to or higher than a predetermined value.

  In one embodiment, a diode and a current limiting element are connected in series to the normally-on type switching element. As the current limiting element, for example, a reactor having a predetermined inductance can be used. If necessary, a zener diode for preventing overvoltage is connected in parallel to the power supply capacitor.

  The switch control circuit may include a discharge circuit connected in parallel to the power supply capacitor. For example, the discharge circuit is configured to perform a discharge operation when a terminal voltage of the power supply capacitor is equal to or higher than the predetermined value and the power semiconductor switch element is on.

For example, the discharge circuit may be configured to discharge the power supply capacitor via a discharge control switch element that performs an on / off operation opposite to that of the power semiconductor switch element.
The discharge circuit may include a resistor and a Zener diode connected in series with the discharge control switch element. In this case, the zener potential of the zener diode is set so that the zener diode becomes conductive when the terminal voltage of the power supply capacitor is equal to or higher than the predetermined value.

  The normally-on type switch element can be turned off by a voltage induced in the resistor. That is, for example, when the normally-on type switch element is an FET, a voltage induced by the resistor is applied as a reverse bias voltage between the gate and the source of the normally-on type switch element. Can be turned off.

  According to the present invention, when a self-powered power supply circuit is adopted as the power supply device of the gate drive circuit of the power semiconductor switch element, the power supply capacitor can be initially charged without providing an initial charge circuit. Therefore, an expensive and large-sized high-power resistor, which is a component of the initial charging circuit, is not required, and as a result, significant cost reduction and downsizing can be achieved.

It is a circuit diagram which shows the structural example of a power converter circuit. It is a circuit diagram which shows embodiment of the power supply device of the gate drive circuit which concerns on this invention. It is operation | movement explanatory drawing when the semiconductor switch element for electric power turns on. It is operation | movement explanatory drawing when the semiconductor switch element for electric power turns off. It is operation | movement explanatory drawing when a power switch is turned on (at the time of initial charge). It is explanatory drawing which shows the discharge operation of the capacitor | condenser for power supplies after a power switch is turned on.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration example of a power conversion circuit. The main circuit 1 of this power conversion circuit (in this example, the main circuit of a three-phase inverter) includes three semiconductor switch elements 3 on the upper arm side and three semiconductor switch elements 3 on the lower arm side corresponding thereto. 'Is connected in series between the power lines 5 and 7.
In the main circuit 1, IGBTs (Insulated Gate Bipolar Transistors) are used as the power semiconductor switch elements 3, 3 ′.

  Free-wheeling diodes 9 and 9 'are connected in parallel to the power semiconductor switch elements 3 and 3', respectively, and gate drive circuits 11 and 11 'are connected to the gates of the switch elements 3 and 3', respectively. Yes. In FIG. 1, only the gate drive circuits 11 and 11 ′ for one set of switch elements 3 and 3 ′ are shown to avoid complication, but of course, for other power semiconductor switch elements 3 and 3 ′. Also, the gate drive circuits 11 and 11 'are connected.

The power supply lines 5 and 7 of the main circuit 1 are connected to the positive and negative electrodes of the DC power supply 13, respectively. Each gate drive circuit 11, 11 ′ generates a gate signal based on the control signals Sc, Sc ′ (for example, PWM signal) from the control circuit 15, and the power semiconductor switch elements 3, 3 ′ are generated by this gate signal. Turn on and off. Therefore, the power controlled by the control signal is supplied to the three-phase motor 17 that is the load of the main circuit 1 via the power semiconductor switch elements 3 and 3 ′.
When the inverter including the main circuit 1 is an AC input inverter, the DC power supply 13 is constituted by a rectification / smoothing circuit (not shown). Reference numeral 19 denotes an inductance of the wiring material.

FIG. 2 shows an example of the configuration of the gate drive circuit 11 shown in FIG. 1 and an embodiment of a power supply device for a gate drive circuit according to the present invention that supplies power to the gate drive circuit 11.
The gate drive circuit 11 includes a photocoupler 21, transistors 23 and 25 connected in series so as to perform complementary operations, and a current limiting base resistor connected between the output terminal of the photocoupler 21 and the bases of the transistors 23 and 25. 27, and a current limiting gate resistor 29 connected between the emitters of the transistors 23 and 25 and the gate of the power semiconductor switch element 3 on the upper arm side.

In the gate drive circuit 11, a terminal voltage of a power supply capacitor 51 described later is applied as a power supply voltage between the power supply lines 31 and 33.
The logic level of the output signal of the photocoupler 21 is changed by the control signal Sc supplied from the control circuit 15 shown in FIG. 1, and the semiconductor switch element 3 is turned on / off according to the logic level. That is, when the “H” level signal is output from the photocoupler 21, the transistor 18 is turned on and current is supplied to the gate of the power semiconductor switch element 3, so that the switch element 3 is turned on. In a state where the power semiconductor switch element 3 is turned on, a current is supplied to the motor 17 via the switch element 3.
On the other hand, when the “L” level signal is output from the photocoupler 21, the other transistor 19 is turned on. In this case, since a current flows in a direction for discharging the gate charge accumulated in the power semiconductor switch element 3, the switch element 3 is turned off.

Next, the configuration of the power supply device for a gate drive circuit according to the present invention that functions as a power supply for the gate drive circuit 11 will be described.
As shown in FIG. 2, a series circuit (not shown in FIG. 1) including a snubber diode 35 and a snubber capacitor 37 is connected in parallel to the power semiconductor switch element 3. The snubber diode 35 and the snubber capacitor 37 are provided to constitute a snubber circuit for dv / dt suppression. The snubber diode 35 has an anode connected to the power supply line 5 and a cathode connected to the positive potential side end of the snubber capacitor 37.

A series connection point of the snubber diode 35 and the snubber capacitor 37 is connected to the positive potential side power supply line 31 of the gate drive circuit 11 through a series circuit including a diode 39, a current limiting element 41 and a normally-on type semiconductor switch element 43. ing.
In the present embodiment, a reactor (coil) having a predetermined inductance is used as the current limiting element 41, and a MOSFET is used as the semiconductor switch element 43.
A resistor 45 is connected between the gate and source of the semiconductor switch element 43. The gate of the semiconductor switch element 43 is connected to the negative potential side power supply line 33 of the gate drive circuit 11 through a series circuit including a Zener diode 47 and a semiconductor switch element 49. In the present embodiment, a MOSFET is used as the semiconductor switch element 49.

A power supply capacitor 51 is connected between the power supply lines 31 and 33 of the gate drive circuit 11. Therefore, a series circuit including the resistor 45, the Zener diode 47, and the semiconductor switch element 49 is connected in parallel to the power supply capacitor 51.
The power supply capacitor 51 is connected in parallel with a Zener diode 53 that prevents the overcharge. Further, the gate of the semiconductor switch element 49 is connected to the output terminal of the photocoupler 21 via the inverter 55.

  In the above description, the configuration of the gate drive circuit 11 and the configuration of the power supply device for the gate drive circuit with respect to the power semiconductor switch element 3 on the upper arm side have been described. Of course, the lower arm is within the dotted line frame in FIGS. A gate drive circuit and a power supply device for the gate drive circuit having the same configuration are provided for the power semiconductor switch element 3 ′ on the side.

The operation of the gate drive circuit power supply device according to this embodiment will be described below.
FIG. 3 shows an operation explanatory diagram when the power semiconductor switch element 3 is turned on.
In the state where the power semiconductor switch element 3 is turned off, the semiconductor switch element 49 is turned on, so that the discharge current of the power supply capacitor 51 flows through the resistor 45. Therefore, the normally-on semiconductor switch element 43 is in a state of being turned off by reverse biasing between its gate and source by the voltage Vb (see FIG. 4) generated across the resistor 45.

Here, when an “H” level signal is output from the photocoupler 21, the power semiconductor switch element 3 is turned on, and a current 56 (see the dotted line) passing through the switch element 3 and the motor 17 flows. The switch element 49 is turned off.
When the semiconductor switch element 49 is turned off, the reverse bias voltage applied between the gate and source of the semiconductor switch element 43 disappears, so that the semiconductor switch element 43 is turned on. Along with this, a current 57 (see the alternate long and short dash line) flows through the path of the capacitor 37, the diode 39, the reactor 41, the semiconductor switch element 43, the capacitor 51, and the capacitor 37, whereby the snubber capacitor 37 is discharged and the power source The capacitor 51 is charged.

  The terminal voltage of the snubber capacitor 37 decreases with time, and when the terminal voltage becomes zero, the current 57 passes through the freewheeling diode 9. Thereafter, the current 57 rapidly decreases, and finally, the electric energy charged in the snubber capacitor 37 is converted into the charging energy of the power supply capacitor 51.

FIG. 4 shows an operation explanatory diagram when the power semiconductor switch element 3 is turned off. When the power semiconductor switch element 3 is turned off, the current 59 commutated to the diode 9 ′ connected in parallel to the semiconductor switch element 3 ′ of the opposing arm and the charging current 61 to the snubber capacitor 37 are the main current as shown by the dotted line. Flowing as.
At this time, since the output of the photocoupler 21 is at the “L” level, the semiconductor switch element 49 is turned on. Here, in the design, assuming that a relationship of Vg ≧ Vz is established between the terminal voltage Vg of the capacitor 51 and the Zener voltage Vz of the Zener diode 47, a discharge current 63 of the capacitor 51 indicated by a one-dot chain line flows. . At this time, as described above, the voltage Vb across the resistor 45 is applied as a reverse bias voltage between the gate and source of the normally-on semiconductor switch element 43, so that the switch element 43 is turned off and the power supply capacitor 51 is turned off. Charging from the capacitor 37 side stops.

By the way, the output of the main power supply 13 is applied to the power supply lines 5 and 7 via the power switch 63 shown in FIG. Therefore, an example of operation when the power switch 63 is turned on (an example of operation during initial charging) will be described below.
When the power switch 63 is turned on, both the normally-on semiconductor switch element 43 on the upper arm side and the normally-on semiconductor switch element on the lower arm side (not shown) are both turned on. The current 65 flows, so that the power supply capacitor 51 on the upper arm side and the power supply capacitor on the lower arm side (not shown) are charged together.

  A terminal voltage Vg of the power supply capacitor 51 is applied to the gate drive circuit 11 as a power supply voltage. Therefore, when charging of the capacitor 51 proceeds and the terminal voltage Vg rises to a predetermined value or more, the photocoupler 21 operates and its output becomes “L”, so that the semiconductor switch element 49 is turned on. . Therefore, when the power supply capacitor 51 is further charged and a relationship of Vg ≧ Vz is established, a current 69 indicated by a one-dot chain line in FIG. 6 flows and the normally-on semiconductor switch element 43 is turned off. As a result, the charging of the power supply capacitor 51 ends when the terminal voltage Vg reaches the design value voltage defined by the Zener voltage Vz.

Thereafter, if the power semiconductor switch element 3 is not turned on, the power supply capacitor 51 is gradually discharged. When the power supply capacitor 51 is discharged until the relationship of Vg <Vz is established, the discharge current 69 is stopped, and the reverse bias voltage applied between the gate and the source of the normally-on semiconductor switch element 43 disappears. To do. As a result, the semiconductor switch element 43 is turned on and the current 65 shown in FIG. 5 flows, so that the power supply capacitor 51 is charged again. That is, after the power switch 63 is turned on, the operation shown in FIGS. 5 and 6 is repeated until the semiconductor switch element 3 is turned on, so that the terminal voltage Vg of the capacitor 51 is maintained at substantially the design value voltage. .
The power supply capacitor on the lower arm side corresponding to the power supply capacitor 51 on the upper arm side is also initially charged in the same manner as the power supply capacitor 51.

  As described above, according to the power supply device for a gate drive circuit according to the present embodiment, the electric energy charged in the snubber capacitor 37 is converted into the charge energy of the power supply capacitor 51, and this charge energy is converted into the gate drive circuit. It can be used as a power source. In addition, the power supply capacitor 51 can be initially charged without providing a dedicated initial charging means, which is advantageous in terms of cost reduction, size reduction, and simplification of the configuration.

The present invention is not limited to the above embodiment, and can include various modifications. For example, in the above-described embodiment, a power conversion device using an IGBT as a power semiconductor switching element is used. However, the present invention uses a normal bipolar transistor, MOSFET, GTO or the like as a power semiconductor switching element. It is also possible to apply to a conversion device.
In the above-described embodiment, a MOSFET is used as the normally-on semiconductor switch element 43. However, a semiconductor switch element made of SiC or a semiconductor switch element made of GaN is used as the normally-on semiconductor switch element 43. Is also possible.

DESCRIPTION OF SYMBOLS 1 Main circuit 3, 3 'Power semiconductor switch element 5, 7 Power supply line 9 Freewheeling diode 11, 11' Gate drive circuit 13 DC power supply 15 Control circuit 17 Motor 21 Photocoupler 23, 25 Transistor 31, 33 Power supply line 35, 35 'Snubber diode 37, 37' Snubber capacitor 39, 39 'Diode 41 Reactor 43 Normally-on semiconductor switch element 45 Resistor 47, 53 Zener diode 49 Semiconductor switch element 55 Inverter 63 Power switch

Claims (9)

A power supply device for a gate drive circuit for driving a power semiconductor switch element of a power conversion circuit,
A series circuit composed of a snubber diode and a snubber capacitor connected in parallel to the power semiconductor switch element;
A power supply capacitor for applying a terminal voltage as a power supply voltage to the gate drive circuit;
A normally-on type switching element that is interposed between the positive potential side terminal of the snubber capacitor and the positive potential side terminal of the power supply capacitor, and causes a charging current to flow to the power supply capacitor;
A switch control circuit for controlling the normally-on type switch element,
The power supply device for a gate drive circuit, wherein the switch control circuit is configured to turn off the normally-on type switch element when a terminal voltage of the power supply capacitor becomes a predetermined value or more.   2. The power supply device for a gate drive circuit according to claim 1, wherein a diode and a current limiting element are connected in series to the normally-on type switch element.   The power supply device for a gate drive circuit according to claim 2, wherein a reactor having a predetermined inductance is used as the current limiting element.   2. The power supply device for a gate drive circuit according to claim 1, wherein a Zener diode for preventing overvoltage is connected in parallel to the power supply capacitor.   The switch control circuit includes a discharge circuit connected in parallel to the power supply capacitor, and the discharge circuit when a terminal voltage of the power supply capacitor is equal to or higher than the predetermined value and the power semiconductor switch element is on. The power supply device for a gate drive circuit according to claim 1, wherein the power supply device is configured to perform a discharging operation.   The discharge circuit includes a discharge control switch element that performs an on / off operation opposite to that of the power semiconductor switch element, and is configured to discharge the power supply capacitor through the discharge control switch element. The power supply device for a gate drive circuit according to claim 5.   The discharge circuit includes a resistor and a Zener diode connected in series with the discharge control switch element, and the Zener diode has a Zener potential that is turned on when the terminal voltage of the power supply capacitor is equal to or higher than the predetermined value. The power supply device for a gate drive circuit according to claim 6, wherein the power supply device is set.   8. The power supply device for a gate drive circuit according to claim 7, wherein the normally-on type switch element is turned off by a voltage induced by the resistor.   The normally-on type switch element is an FET, and a voltage induced by the resistor is applied as a reverse bias voltage between a gate and a source of the normally-on type switch element. 9. A power supply device for a gate drive circuit according to 8.

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