JPH04372596A - Dc motor drive circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for protecting a DC motor and a drive circuit from overcurrent in a DC motor drive circuit.

0002

2. Description of the Related Art Conventionally, this type of technology has a configuration in which a drive signal is cut off and a DC motor is stopped based on a signal detected by a current detection unit 30, as shown in FIG. The configuration was such that the drive current was cut off and the DC motor was stopped based on the signal detected by the unit 40.

0003

[Problems to be Solved by the Invention] However, in the prior art described above, in a device that is controlled by a signal synchronized with the rotation of the DC motor, the drive signal is abruptly cut off when the DC motor is protected. The signal synchronized with the rotation of the device suddenly stops, resulting in a lack of stability in the operation of the entire device. Further, in the configuration shown in FIG. 3, operation is not guaranteed when the base voltage of the protection transistor is around the same level as the VBE of the transistor, and overcurrent may flow continuously.

The present invention has been made to solve these drawbacks, and provides efficient protection of the DC motor and drive circuit in a voltage and current range exceeding the DC motor rating, and a method for abruptly stopping the DC motor. By preventing this, the stability of the entire device can be improved.

[0005]

[Means for Solving the Problems] The present invention provides a drive circuit for driving a DC motor, which includes a current detection unit that detects the amount of current flowing through the DC motor, and a voltage that is determined based on the amount of current detected by the current detection unit and the drive voltage. The present invention is characterized in that it includes a correction value determining section that performs correction, and a voltage variable section that varies the drive voltage based on a signal from the correction value determining section.

[0006]

[Operation] According to the above structure of the present invention, when a current exceeding the rated value of the DC motor flows, the current detecting section detects the overcurrent, and the correction value determining section corrects it based on the detected signal and drive voltage. The voltage value is determined, and the voltage variable unit varies the drive voltage based on the signal output from the correction value determination unit, thereby regulating the amount of current flowing to the DC motor, thereby ensuring efficient protection of the DC motor and DC control in the event of an emergency. By preventing sudden stopping of the motor, the stability of the entire device is improved.

[0007]

Embodiment FIG. 1 is a block diagram of an embodiment of the present invention. When a current exceeding the rating of the motor 5 flows, the current detecting section 2 detects the overcurrent and outputs a signal to the voltage limiting section 3. The correction value determination unit 3 determines the voltage correction value by comparing the current drive voltage and the signal detected by the current detection unit 2. The voltage variable section 4 receives the signal from the correction value determining section and corrects the drive voltage. Further, the correction value determination section 3 outputs a stop request signal to the motor control section 6. Upon receiving the stop request signal, the motor control unit 6 performs speed-down and stop control of the motor.

FIG. 2 is a circuit example of the block diagram shown in FIG.

10 is I controlled by the CPU etc.
/O port, which controls the DC motor 11. The I/O port outputs two control lines, which perform ON/OFF control and speed-down control of the DC motor. This signal line passes through the OR gate 12, so that "00" is treated as an OFF signal, and other than that, "00" is treated as an OFF signal.
It is sent to the drive transistor 13 as an N signal.

When the drive transistor 13 is energized, current flows through the DC motor 11 to operate the motor. This causes a potential difference between both ends of the resistor 15 of the current detection section 14, and this voltage is compared by the comparator 16. The threshold level of this comparator is

[0011]

[Math 1]

It is expressed as: At this time, V is the motor drive voltage, R1 is the dividing resistor 17, and R2 is the dividing resistor 18. This threshold level is determined by the current rating of the DC motor.

The correction value determining section 19 determines the voltage based on the signal detected by the current detecting section 14 and the drive signal output from the I/O port 10. The output voltage is

001
4]

[Math 2]

It is expressed as: At this time, R1 is a resistance of 20,
R2 is resistor 21, R3 is resistor 22, R4 is resistor 23, V
1 is the terminal voltage of the resistor 20, V2 is the terminal voltage of the resistor 21,
V3 is the terminal voltage of the resistor 22. Resistance 20, 21, 2
The driving voltage for each state is determined by the ratio of 2. Here, the drive voltage is determined by correcting the three levels of motor drive voltage through the signal line from the I/O port and the current. This drive voltage is sent to the voltage variable section 24, and the differential amplifier and transistor 7 vary the drive voltage of the motor.

Further, the output voltage of the correction value determining section 19 is compared with a comparator and sent to the I/O port as a stop request. This allows the I/O port and CPU to perform speed-down control to ensure stable motor drive and efficient protection from overcurrent.

Although this embodiment has been described using an ordinary DC motor as an example, it can also be applied to a step motor or the like using the same method.

[0018]

[Effects of the Invention] As described above, according to the present invention, the DC
By efficiently protecting the motor and preventing sudden stoppage of the motor in an emergency, it is possible to improve the stability of the entire device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

FIG. 3 is a circuit diagram showing an example of a prior art.

FIG. 4 is a circuit diagram showing an example of conventional technology.

[Explanation of symbols]

1 Drive circuit 2 Current detection section 3 Correction value determination section 4 Voltage variable part 5 Motor 6 Motor control section

Claims (1)

[Claims] 1. A drive circuit that drives a DC motor, comprising: a current detection unit that detects the amount of current flowing through the DC motor; and a correction value determination unit that determines a correction voltage based on the amount of current detected by the current detection unit and the drive voltage. and a voltage variable section that varies the drive voltage based on a signal from the correction value determining section.