JPH0584196U - Motor control circuit - Google Patents

Abstract

(57) [Summary] [Purpose] In the conventional motor control circuit, the motor terminals were open when the power was copied, and braking could not be performed. The purpose of the present invention is to bring the power MOSs on both ends of the motor into conduction when the power is cut off so as to brake the motor. [Structure] A high-impedance drive circuit is provided in a gate drive circuit of a power MOS FET of a motor drive circuit, and a capacitor 20 for supplying electric charge to the gate when power is cut off is provided in parallel. As a result, when the power is cut off, the voltage of the gate is held for a certain period of time, and the rotating motor is braked. Alternatively, when the load is stroked with a load having a repulsive force such as a spring, it is possible to gradually return to a position where the repulsive force is attenuated by the counter electromotive force.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a motor control circuit, and more particularly to a motor control circuit that performs braking when power is cut off.

[0002]

[Prior Art]

 A conventional H-bridge motor control circuit using a power MOS FET is configured, for example, as shown in FIG. The current from the power supply 1 is supplied to the control unit 3, the power MOS FET drive unit 4 and the motor drive unit 5 via the current cutoff element 2 such as a switch or a relay.

The power MOS FET drive unit 4 is composed of four drive circuits 6, 7, 8 and 9, and in response to a signal from the control unit 3, the corresponding power MOS FETs 10, 11, 12, 13 of the motor drive unit 5 are driven. Charge and discharge the gate capacitance. The motor drive unit 5 controls the current from the power supply 1 and guides it to the motor 14 to control the rotation direction, rotation speed, rotation torque, and the like.

The power MOS FETs 10 and 13 lead to the power source a by turning ON between the source and drain, and rotate the motor 14 in the forward direction. The power MOS FETs 11 and 12 guide the power supply of b by turning on the source-drain and reverse the motor 14. Further, the power MOS FETs 10 and 11 conduct a current of c or d by turning on between the source and the drain to brake the motor 14. The same applies to the power MOS FETs 12 and 13.

FIG. 3 shows an example of the circuit configuration of the power MOS FET drive circuit 8 and the power MOS FET 12.

The transistors (or FETs) 15 and 16 are in the opposite state with respect to the input signal VA, and drive the power MOS FET 18. When VA is at "LOW" level, the transistor (or FET) 15 becomes conductive and the transistor (or FET) 16 becomes non-conductive, and the electric charge is charged from the transistor 15 through the gate resistor 17 to the gate capacitance of the power MOS FET 18. , 18 become conductive.

When the power MOS FETs 10 and 11 are P-channel and the power MOSFETs 12 and 13 are N-channel, the power MOS FET drive circuits 6, 7 and 9 have the same circuit configuration as 8. When the power MOS FETs 10 to 13 are all N-channel, the drive circuits 6 and 7 are connected to a power source in which a transistor corresponding to the charge side transistor 15 is pressed. The drive circuit 9 is similar to 8.

However, according to the conventional circuit configuration, when the power supply is cut off, the charge charged in the gate capacitance of the power MOS FET flows back through the charge side transistor through the gate resistance and is discharged. Therefore, all the power MOS FETs are turned off.

[0009]

[Problems to be solved by the device]

 In this conventional motor control circuit, all power MOS FETs in the motor drive circuit are cut off when the power is cut off, so the charge is cut off when the motor is rotating or when a load with repulsive force is operating. If this happens, there was a problem that braking could not be applied.

Therefore, the object of the present invention is to brake the rotating motor when the power is cut off, or to perform braking until the load with repulsive force is completely returned and the repulsive force disappears. It is to provide a motor control circuit.

[0011]

[Means for Solving the Problems]

 Therefore, in order to achieve the above-mentioned object, the present invention comprises a circuit for supplying electric charge to the gate of the power MOS FET of the motor drive circuit when the power is cut off, and a power MOS FET drive circuit which becomes high impedance when the power is cut off. It is a thing.

[0012]

【Example】

 Next, an embodiment of the present invention will be described with reference to FIG.

In the figure, reference numerals 15 to 18 are the same as those in FIG. 3, and the operation as described above is performed. The diode 19 prevents the gate charge of the power MOS FET 18 from being discharged via the transistor 15 when the power is cut off, and increases the impedance of the power MOS FET drive circuit when the power is cut off.

When energized, the capacitor 20 is almost charged to the power supply voltage via the diode 19. When the power supply is cut off, the electric charge of the capacitor 20 is separated from the power supply by the diode 19, and thus is held. Since the capacitor 20 is connected to the gate of the power MOS FET 18 via the resistor 21, the charge of the capacitor 20 passes through the resistor 21 and charges the gate capacitance of the power MOS FE T18. Since the high-impedance drive circuit is connected to the gate of the power MOS FET 18, the electric charge of the capacitor 20 is discharged by a minute leak current until the power MOS FET is turned off. , And the drain and source 2 are electrically connected. By providing the drive circuit 8 and 9 or the drive circuits 6 and 7 in FIG. 2 with the circuit of the present invention, it is possible to short-circuit the both ends of the motor 14 for a certain period of time when the power is shut off.

[0015]

[Effect of the device]

 As described above, according to the present invention, when the power is cut off, both terminals of the motor are short-circuited for a certain period of time. Therefore, if the power is cut off while the motor is rotating, the rotation can be stopped. Further, when a load having a repulsive force such as a spring is stroked, it is possible to gradually return to a position where the repulsive force is attenuated by the reverse power.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a power MOS FET drive circuit of the present invention.

FIG. 2 is a block diagram of a conventional motor drive circuit.

FIG. 3 is a conventional power MOS FET drive circuit.

[Explanation of symbols]

1 DC power supply 2 Switch or relay 3 Control unit 4 Power MOS FET drive unit 5 Motor drive unit 6, 7, 8, 9 Power MOS FET drive circuit 10, 11, 12, 13 Power MOS for motor drive
FET 14 Motor 15 Charge transistor 16 Discharge transistor 17 Gate resistance 18 Motor drive power MOS FET 19 Backflow prevention diode 20 Backup capacitor 21 Backup charge supply resistor

Claims (1)

[Scope of utility model registration request] 1. A motor drive circuit comprising a power MOS FET drive circuit having a capacitor for supplying electrification in parallel with the drive circuit of the gate of the power MOS FET.