JP2004274848A - Inverter drive circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter drive circuit capable of stably driving an inverter, even if the voltage supplied from a power source fluctuates or is instantaneously interrupted. <P>SOLUTION: A second power supply line 28 is provided parallel to a first power supply line 26. Conduction/non-conduction of the second power supply line 28 is controlled with a voltage, acquired by filtering a low band of the voltage of the first power supply line 26. So, even if the voltage supplied to a drive circuit 14 by way of the first power supply line 26 fluctuates or stops instantaneously, the conduction state of the second power supply line 28 is not affected by the fluctuation or instantaneous interruption of the supply voltage which via the first power supply line 26. Thus, a voltage is stably supplied to the drive circuit 14 by way of the second power supply line 28, enabling stable driving of an inverter 36. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inverter driving circuit provided with a driving circuit to which a voltage from a power supply is supplied and which outputs a signal for driving an inverter.
[0002]
[Prior art]
An example of an inverter device including a conventional inverter drive circuit is disclosed in Japanese Patent Application Laid-Open No. 9-23664 (Patent Document 1). In this conventional drive circuit, a MOSFET is connected in series to a transistor that controls the gate of a semiconductor switching element in an inverter via a gate resistor. Then, the voltage of the DC power supply connected to the inverter is detected, and when the detected voltage is higher than a predetermined voltage, the MOSFET in the drive circuit is turned off, and when the detected voltage is lower than the predetermined voltage, the MOSFET is turned on. I have. As a result, switching loss when the voltage of the DC power supply fluctuates is reduced.
[0003]
[Patent Document 1]
JP-A-9-23664
[Problems to be solved by the invention]
In this conventional drive circuit, when the voltage from the power supply supplied to the drive circuit fluctuates or is momentarily interrupted, the drive of the drive circuit is temporarily stopped, so that the drive of the inverter is temporarily stopped. . Therefore, in the conventional drive circuit, there is a problem that the inverter cannot be driven stably when the voltage from the power supply fluctuates or momentary interruption occurs.
[0005]
The present invention has been made in view of the above problems, and has as its object to provide an inverter drive circuit that can stably drive an inverter even when a supply voltage from a power supply fluctuates or is momentarily interrupted.
[0006]
[Means for Solving the Problems]
In order to achieve such an object, an inverter drive circuit according to the present invention is an inverter drive circuit that is supplied with a voltage from a power supply and includes a drive circuit that outputs a signal for driving an inverter. At least a first power supply line and a second power supply line are provided between the drive circuit and the drive circuit in parallel with each other, and switching between conduction and non-conduction in the second power supply line is possible. And a switch control circuit that controls conduction / non-conduction of the switch by outputting a supply voltage from the power supply to the switch after low-pass filtering or delaying the supply voltage for a predetermined time. I do.
[0007]
According to the present invention, at least the first power supply line and the second power supply line are provided between the power supply and the drive circuit in parallel with each other. Then, conduction / non-conduction in the second power supply line is controlled by inputting to the switch a voltage obtained by low-pass filtering or delaying the supply voltage from the power supply by the switch control circuit for a predetermined time. Thereby, even if the supply voltage to the drive circuit via the first power supply line fluctuates or momentarily interrupts, the fluctuation or momentary interruption of the input voltage to the switch at that time is caused by the low-pass filter function of the switch control circuit or the time. Suppressed by the delay function. Therefore, the conduction state of the second power supply line at that time is not affected by the fluctuation of the supply voltage passing through the first power supply line or the instantaneous interruption. As described above, according to the present invention, even if the supply voltage to the drive circuit via the first power supply line fluctuates or is momentarily interrupted, the drive circuit via the second power supply line is stabilized. Since a voltage can be supplied, the inverter can be driven stably.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter, referred to as embodiments) will be described with reference to the drawings.
[0009]
FIG. 1 is a circuit block diagram schematically illustrating a configuration of a motor drive system including an inverter drive circuit according to an embodiment of the present invention. The motor drive system of the present embodiment includes an inverter drive circuit 10, batteries 12, 40, a DC-DC converter 44, an inverter 36, and a motor 38. The inverter drive circuit 10 includes a drive circuit 14, a transistor 16, and a switch control circuit 18.
[0010]
A first power supply line 26 and a second power supply line 28 are provided between the battery 12 as a power supply and the drive circuit 14 in parallel with each other. The IG switch 20 and the diode 22 are provided on the first power supply line 26. Further, the first power supply line 26 is connected to the load 34 and the switch control circuit 18. The second power supply line 28 includes the transistor 16 and the diode 24.
[0011]
The IG switch 20 can switch between conduction and non-conduction in the first power supply line 26. When the IG switch 20 is turned on, the DC voltage from the battery 12 causes the load 34, the drive circuit 14, and the switch It is supplied to the control circuit 18. The diode 22 is provided between the IG switch 20 and the drive circuit 14 so as to allow only a current flowing from the battery 12 to the drive circuit 14.
[0012]
The transistor 16 serving as a switch can switch between conduction and non-conduction in the second power supply line 28, and by setting the transistor 16 to a conduction state, the DC voltage from the battery 12 is reduced to the second power supply line 28. Is supplied to the drive circuit 14 via the. The conduction / non-conduction of the transistor 16 is controlled by an output voltage from a switch control circuit 18 described later. The diode 24 is provided between the transistor 16 and the driving circuit 14 so as to allow only a current flowing from the battery 12 to the driving circuit 14.
[0013]
The switch control circuit 18 is configured by a circuit that functions as a low-pass filter having a predetermined time constant. When the IG switch 20 is conducting, a DC voltage from the battery 12 is supplied to the switch control circuit 18. The switch control circuit 18 performs low-pass filtering on the supply voltage from the battery 12 and outputs the resultant to the transistor 16. The conduction / non-conduction of the transistor 16 is controlled by the output voltage from the switch control circuit 18.
[0014]
In the drive circuit 14, when the IG switch 20 is in a conductive state, a DC voltage from the battery 12 is supplied as a power supply voltage of the drive circuit 14. Then, the drive circuit 14 outputs a drive signal to each switching element in the inverter 36. The drive signal controls the drive of the inverter 36.
[0015]
The inverter 36 includes three arms 36-1 to 36-3 each including a pair of switching elements connected in series, and converts a DC voltage from the battery 40 into a three-phase AC having a phase difference of 120 degrees by a switching operation. After the conversion, an AC current is supplied to each phase of a three-phase coil (not shown) of the electric motor 38. At this time, the DC voltage from the battery 40 is boosted by the DC-DC converter 44 before being supplied to the inverter 36. A capacitor 42 is provided in parallel with the arms 36-1 to 36-3.
[0016]
Regarding an example of the connection between the inverter drive circuit 10 and the battery 12 configured as described above, the positions of the IGCT terminal 30 between the IG switch 20 and the diode 22 and the + B terminal 32 between the battery 12 and the transistor 16 are as follows. A connection is made by a connector.
[0017]
Next, the operation of the inverter drive circuit 10 of the present embodiment will be described with reference to the time chart of FIG.
[0018]
When the IG switch 20 is switched from non-conduction to conduction (time t1 in FIG. 2), a DC voltage from the battery 12 is supplied to the drive circuit 14 as a power supply voltage via the first power supply line 26. . Further, the DC voltage from the battery 12 is also supplied to the load 34 and the switch control circuit 18. The switch control circuit 18 low-pass filters the supply voltage from the battery 12 and outputs it to the transistor 16, so that the transistor 16 is switched from non-conduction to conduction. When the transistor 16 is switched to the conductive state, the DC voltage from the battery 12 is supplied to the drive circuit 14 via the second power supply line 28 as the power supply voltage. However, while the IG switch 20 is conducting, the supply voltage to the drive circuit 14 via the IGCT terminal 30 (first power supply line 26) rises in a step-like manner, whereas the output voltage from the switch control circuit 18 is It is supplied to the transistor 16 with a delay due to the time constant. Therefore, as shown in the time chart of FIG. 2, the supply voltage to the drive circuit 14 via the + B terminal 32 (the second power supply line 28) changes with respect to the rise of the supply voltage via the IGCT terminal 30. It rises with a delay of the predetermined time δt1 (time t2 in FIG. 2).
[0019]
Here, since the first power supply line 26 is connected to the load 34, the voltage at the IGCT terminal 30 may fluctuate due to the load fluctuation. Then, the supply voltage to the drive circuit 14 via the IGCT terminal 30 may be momentarily cut off due to poor contact of the connector at the IGCT terminal 30 or noise. In these cases, when the IG switch 20 is in the conductive state, a stable voltage cannot be supplied to the drive circuit 14 as the power supply voltage via the IGCT terminal 30.
[0020]
However, in the present embodiment, a second power supply line 28 is provided in parallel with the first power supply line 26. The conduction / non-conduction of the second power supply line 28 is controlled by the voltage obtained by low-pass filtering the voltage of the first power supply line 26. Thereby, even if the supply voltage to the drive circuit 14 via the first power supply line 26 fluctuates or is momentarily interrupted, the switch control circuit 18 provides the second power supply line 28 with a low-pass filter function. Fluctuation or instantaneous interruption of the input voltage to the transistor 16 is suppressed. Therefore, the conduction state of the second power supply line 28 is not affected by a change in supply voltage via the first power supply line 26 or an instantaneous interruption. From the above, as shown in the time chart of FIG. 2, even if the supply voltage to the drive circuit 14 via the first power supply line 26 fluctuates or is momentarily interrupted (time t3 to t4 in FIG. 2), A stable voltage can be supplied to the drive circuit 14 via the second power supply line 28.
[0021]
When the IG switch 20 is switched from conduction to non-conduction (time t5 in FIG. 2), the supply of the voltage output from the battery 12 to the drive circuit 14 via the first power supply line 26 is cut off. . At the same time, the voltage supply to the load 34 and the switch control circuit 18 is also cut off. When the voltage supply to the switch control circuit 18 is cut off, the transistor 16 is switched from conduction to non-conduction, so that the supply of the voltage output from the battery 12 to the drive circuit 14 via the second power supply line 28 Is also shut off. However, when the IG switch 20 is turned off, the supply voltage to the drive circuit 14 via the IGCT terminal 30 (first power supply line 26) falls stepwise, whereas the output from the switch control circuit 18 The voltage is supplied to the transistor 16 with a time constant delay. Therefore, as shown in the time chart of FIG. 2, the supply voltage to the drive circuit 14 via the + B terminal 32 (the second power supply line 28) changes with respect to the fall of the supply voltage via the IGCT terminal 30. Fall with a delay of the predetermined time δt2 (time t6 in FIG. 2).
[0022]
As described above, according to the inverter drive circuit 10 of the present embodiment, even if the supply voltage to the drive circuit 14 via the first power supply line 26 fluctuates or is momentarily interrupted when the IG switch 20 is conducting. A stable voltage can be supplied to the drive circuit 14 via the second power supply line 28 without being affected by the fluctuation or the instantaneous interruption. Therefore, even if the supply voltage of the battery 12 fluctuates or is momentarily interrupted, the inverter 36 can be driven stably.
[0023]
Furthermore, in the present embodiment, when the IG switch 20 is switched from conduction to non-conduction, a voltage is supplied from the battery 12 to the drive circuit 14 via the second power supply line 28 for a predetermined time δt2. I have. By energizing one of the three-phase coils during the predetermined time δt2, the electric charge stored in the capacitor 42 can be discharged. Therefore, in the present embodiment, it is possible to reduce the resistance for discharging the electric charge stored in the capacitor 42 when the IG switch 20 is switched from conduction to non-conduction.
[0024]
In the above description, the case where the switch control circuit 18 is configured by a low-pass filter circuit having a predetermined time constant has been described. However, the switch control circuit 18 may be configured by a delay circuit that delays the supply voltage from the battery 12 for a predetermined time and outputs the result to the transistor 16.
[0025]
FIG. 3 shows a time chart when the switch control circuit 18 is configured by a delay circuit. Also in this configuration, even if the supply voltage to the drive circuit 14 via the first power supply line 26 fluctuates or is momentarily interrupted (time t3 to t4 in FIG. 3) in the conductive state of the IG switch 20, the second voltage is applied. A stable voltage can be supplied to the drive circuit 14 via the power supply line 28 of FIG. In this configuration, the supply voltage to the drive circuit 14 via the second power supply line 28 fluctuates or momentarily stops after the delay time of the delay circuit elapses (time t7 to t8 in FIG. 3). In this case, a stable voltage can be supplied to the drive circuit 14 via the first power supply line 26.
[0026]
As described above, the embodiments of the present invention have been described, but the present invention is not limited to these embodiments at all, and can be implemented in various forms without departing from the technical idea of the present invention. Of course.
[0027]
【The invention's effect】
As described above, according to the present invention, a stable voltage can be supplied to the drive circuit even if the supply voltage from the power supply fluctuates or is momentarily interrupted, so that the inverter can be driven stably. .
[Brief description of the drawings]
FIG. 1 is a circuit block diagram schematically illustrating a configuration of a motor drive system including an inverter drive circuit according to an embodiment of the present invention.
FIG. 2 is a time chart illustrating an operation of the inverter drive circuit according to the embodiment of the present invention.
FIG. 3 is a time chart illustrating an operation of a modification of the inverter drive circuit according to the embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 10 inverter drive circuit, 12, 40 battery, 14 drive circuit, 16 transistor, 18 switch control circuit, 20 IG switch, 26 first power supply line, 28 second power supply line, 34 load, 36 inverter, 38 motor , 44 DC-DC converter.

Claims (1)

An inverter drive circuit which is supplied with a voltage from a power supply and includes a drive circuit which outputs a signal for driving the inverter,
At least a first power supply line and a second power supply line are provided in parallel between the power supply and the drive circuit,
A switch capable of switching conduction / non-conduction in the second power supply line;
A switch control circuit that controls conduction / non-conduction of the switch by outputting a supply voltage from the power supply to the switch with a low-pass filtering or a predetermined time delay,
An inverter drive circuit, further comprising:

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