JPH11318085A - Power supply circuit and its disconnection method - Google Patents

Abstract

(57) [Problem] To provide a power supply circuit and a power supply circuit capable of consuming electric charges accumulated in a smoothing capacitor in a short time without using a discharge resistor or a dedicated discharge circuit when a main power supply is cut off. The aim is to provide a method. SOLUTION: When a battery 12 as a main power supply is cut off,
Each of the transistors 1 to 6 is controlled so that the switching mode of the inverter 10 is fixed to one of the switching modes in which both the upper transistor 8 and the lower transistor 9 are on, and the discharge current of the smoothing capacitor 13 is controlled by the motor. The fourteen stator coils 14u, 14v, and 14w were caused to flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit for smoothing a DC voltage from a main power supply with a smoothing capacitor and supplying the same to an inverter, and outputting a predetermined AC current from the inverter to a stator coil of a motor, and a method of shutting off the power supply circuit. Things.

[0002]

2. Description of the Related Art Conventionally, in an electric vehicle or the like, a DC voltage from a battery is converted into a predetermined AC current by an inverter to drive a motor. Then, the switching operation of the transistor in the inverter is controlled according to the accelerator operation or the like, and the output torque of the motor is controlled. In order to perform such control, it is necessary to suppress fluctuations in the DC voltage supplied to the inverter. Normally, a smoothing capacitor is used to suppress fluctuations in the DC voltage supplied from the main power supply (battery). Restrained.

On the other hand, when the main power supply is cut off for maintenance or the like, it is not preferable that accumulated charge remains in the smoothing capacitor. Therefore, in Japanese Utility Model Laid-Open Publication No. Hei 3-11393, a heat-resistant discharge resistor having a large volume such as an enamel resistor is provided, and both electrodes of a smoothing capacitor are connected by the discharge resistor when the main power supply is cut off. The charge stored in the capacitor is consumed. Further, Japanese Patent Application Laid-Open No. 9-201065 discloses a technique in which a dedicated discharge circuit is provided in an inverter, and charges accumulated in a smoothing capacitor are passed through a switching transistor and consumed. As shown in FIG. 4, a switch S for switching the resistance connected to the gate of the upper transistor 1 is provided in at least one arm of the inverter, and the switch S is operated when the main power supply is cut off. The resistance connected to the gate of the transistor 1 is switched from a small resistance Rl to a large resistance R2, and the control transistor Tr1 of the upper transistor 1 and the control transistor Tr3 of the lower transistor 4 are both turned on to set the transistor 1 and 4 are turned on so that the electric charge stored in the smoothing capacitor 13 flows through the transistors 1 and 4 and is consumed. At this time, the current (collector current) in the transistor 1 can be suppressed to a predetermined value in the active region of the transistor 1 because the voltage applied to the gate is limited by the large resistor R2. In this way, when the main power supply is cut off, discharge by the discharge resistor or
By discharging the electric charge accumulated in the smoothing capacitor by the discharge by the discharge dedicated circuit, it is possible to prevent the power supply line of the circuit from being maintained at a high voltage forever.

[0004]

In an electric vehicle or the like, a main power supply (battery) having a considerably high voltage is employed in order to obtain a sufficient output torque. Large capacitors are also used. In order to consume the charge stored in such a large-capacity smoothing capacitor in a short time, if a discharge resistor is used, the volume of the discharge resistor is further increased, and the circuit as a whole becomes large. In addition, there is a problem that the manufacturing cost is increased. Further, even when a dedicated discharge circuit is used, there is a problem that the circuit scale is increased by the area occupied by the dedicated discharge circuit, and the cost is also increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to consume a charge stored in a smoothing capacitor in a short time without using a discharging resistor or a dedicated discharging circuit when a main power supply is cut off. It is an object of the present invention to provide a power supply circuit and a method for shutting off the power supply circuit.

[0006]

According to a first aspect of the present invention, there is provided a method for shutting off a power supply circuit, wherein when a main power supply is shut off, electric charges accumulated in a smoothing capacitor are consumed by a motor coil. It is characterized by.

According to the power supply circuit of the present invention, when the main power supply is cut off, the switching mode of the inverter is set to:
Each transistor is controlled so as to fix the mode in which both the upper transistor and the lower transistor are turned on, and the discharge current of the smoothing capacitor flows to the motor coil.

According to a third aspect of the present invention, when the main power supply is cut off, the current flowing through the on-state transistor is controlled to a predetermined value.

[0009]

FIG. 1 is a circuit diagram showing a configuration of a motor system according to an embodiment of the present invention. A battery 12 as a main power supply is connected to a motor 14 via an inverter 10.
It is connected to the. The inverter 10 includes an upper transistor 8 composed of switching transistors 1, 3, and 5.
And three arms (1-4, 2-5, 3-6) each of which is connected in series with a lower transistor 9 including switching transistors 2, 4, and 6, and the control device 11 By controlling the gate voltages of the predetermined transistors 1 to 6 and turning on and off the transistors 1 to 6 in the order of the switching mode, three-phase alternating current is sequentially supplied to the stator coils 14u, 14v, and 14w of the motor 14, The rotor (not shown) of the motor 14 is rotated. For example, as shown in FIG. 2, each of the two switching modes of the voltage-type PWM inverter depends on whether one of the transistors 1 to 6 of the upper transistor 8 and the lower transistor 9 of the same arm is on for each phase. Therefore, there are eight patterns for the U phase, V phase, and W phase. Motor 1
In driving the inverter 4, the inverter 10 sequentially switches the eight switching modes, and converts the inverter voltage represented by the stepwise rotating vector having a phase shift of 60 degrees to the stator coils 14u, 14v,
Output to 14w. Each of the above transistors 1 to 6
Is an IGBT (Insulated Gate Bipolar Transistor)
or), and a feedback diode 7 for flowing back electromotive current is connected between each collector and emitter. Further, the control device 11 is supplied with information such as a torque command and the number of rotations of the motor 14 from the rotation sensor 15, and the control device 11 controls the switching operation of the transistors 1 to 6 based on the information, The driving of the motor 14 is controlled. In the present embodiment, a current sensor 17 is provided to detect a current flowing through the inverter, and a detection result signal is supplied to the control device 11. Further, a smoothing capacitor 13 is connected between the power supply and the ground of the inverter 10 to suppress the fluctuation of the DC voltage supplied from the battery 12. The main switch 16 disconnects the battery 12 from the inverter 10 by turning off an ignition switch of the electric vehicle.

Next, the operation will be described. When an ignition switch (not shown) of the electric vehicle is turned off, control device 11 sets transistors 1 to 6 to one of switching modes b to g in which both upper transistor 8 and lower transistor 9 are on. After fixing, the main switch 16 is turned off and preparation for discharging the smoothing capacitor 13 is started. For example, as shown in FIG. 3, if the ignition switch is turned off when the switching mode is a, the control device 11 switches the switching mode to b in the control section A, fixes the switching mode, and stores the switching mode b. I do. That is, when the ignition switch is off, the transistor 1 is off and the transistors 6 and 2 are on. Therefore, the control device 11 keeps the transistors 6 and 2 on and sets the switching pulse width of the transistor 1 on. The transistor 1 is gradually increased to turn on the transistor 1. At this time, the switching pulse width of the transistor 4 which is the same arm as the transistor 1 gradually decreases, and the transistor 4 is turned off. After the main switch 16 is turned off, the control device 11 applies a gate voltage to the stored switching mode b transistors 1, 6, and 2 so that the discharge current of the smoothing capacitor 13 flows, and flows through the transistors 1, 6, and 2. Controls collector current. Therefore, the charge stored in the smoothing capacitor 13 is
Through the stator coils 14u, 14v, 1 of the motor 14
4w consumed. Here, the discharge time of the smoothing capacitor 13 can be appropriately set by adjusting the gate voltages of the transistors 1, 6, and 2. The current flowing through the inverter, that is, the current sensor 1
When the detected current of 7 becomes 0, it is determined that the predetermined discharge has been completed, the transistors 1, 6, and 2 are turned off, and the discharge process is completed. In addition, the control device 11 prevents the rotation of the motor 14 during discharging by fixing the switching mode of the transistors 1 to 6 immediately before the vehicle stops in order to control the power on / off by itself.

As described above, according to the present embodiment, when the battery 12 serving as the main power supply is cut off, the switching mode of the inverter 10 is changed to the switching mode in which both the upper transistor 8 and the lower transistor 9 are on. Each transistor 1 to 1 is fixed to one of the modes (b to g).
6 and discharge current of the smoothing capacitor 13 to the motor 1
4, the electric charge accumulated in the smoothing capacitor 13 can be consumed in a short time without using a discharging resistor or a dedicated discharging circuit. Cost reduction can be achieved. The switching mode during discharging is
Since it is fixed in the same mode, the motor 14 does not rotate and the vehicle does not start moving, which is safe.

In the above embodiment, the termination of the discharge is determined based on the current detected by the current sensor 17, but may be determined by monitoring the voltage at both terminals of the smoothing capacitor 13. In the above example, IGBTs are used as the transistors 1 to 6;
er Modules). Further, in the above embodiment, the control of the inverter by the voltage-type PWM inverter has been described, but other inverter control may be performed.

[0013]

As described above, according to the first aspect of the present invention, when the main power supply is cut off, the electric charge accumulated in the smoothing capacitor is consumed by the motor coil. The electric charge stored in the smoothing capacitor can be consumed in a short time without using a resistor for use or a dedicated circuit for discharging.

According to the second aspect of the present invention, when the main power supply is cut off, each transistor is fixed so that the switching mode of the inverter is fixed to a mode in which both the upper transistor and the lower transistor are on. Control, the discharge current of the smoothing capacitor flows to the motor coil, so that the electric charge accumulated in the smoothing capacitor can be safely consumed in a short time without using a discharging resistor or a circuit dedicated to discharging. And cost reduction can be achieved.

According to the third aspect of the present invention, when the main power supply is cut off, the current flowing through the on-state transistor is controlled to a predetermined value, so that the discharge time of the smoothing capacitor can be easily set. Can be done.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a motor system according to the present embodiment.

FIG. 2 is a diagram illustrating a switching mode of an inverter.

FIG. 3 is a time chart showing an operation when a power supply circuit according to the present embodiment is cut off.

FIG. 4 is a diagram showing a configuration of a dedicated discharge circuit in a conventional power supply circuit.

[Explanation of symbols]

1-6 transistor, 7 diode, 8 upper transistor, 9 lower transistor, 10 inverter,
11 control device, 12 battery, 13 smoothing capacitor, 14 motor, 15 rotation sensor, 16 main switch, 17 current sensor

Claims (3)

[Claims] In a power supply circuit, a DC voltage from a main power supply is smoothed by a smoothing capacitor and supplied to an inverter, and a switching operation of each transistor of the inverter is controlled to output a predetermined AC current to a motor coil. A method for shutting off a power supply circuit, wherein when a power supply is cut off, electric charges accumulated in the smoothing capacitor are passed through the motor coil to be consumed. 2. A motor comprising: a smoothing capacitor for smoothing a DC voltage from a main power supply; and a control device for controlling a switching operation of each arm comprising upper and lower transistors of an inverter, and a predetermined AC current is supplied to the motor. In the power supply circuit that outputs to the coil, when the main power supply is cut off, the control device fixes the switching mode of the inverter to one of the modes in which both the upper transistor and the lower transistor are turned on. A power supply circuit wherein a discharge current of a capacitor is caused to flow to the motor coil. 3. The power supply circuit according to claim 2, wherein the control device controls the transistor so that a predetermined current flows through the transistor in the on state when the main power supply is cut off.