JPS6289485A - Driving circuit for motor - Google Patents

Abstract

PURPOSE:To prevent a motor from generating heat by stopping the energization of the motor when the motor rotates in the predetermined amount or when a predetermined time is elapsed. CONSTITUTION:When a switch SW1 is closed, a current flows through switches SW2A, SW1, and resistors R1, R3 to a Zener diode D1, and a transistor Q1 is turned ON. Thus, a motor M is driven. The charge of a capacitor C1 is discharged by the closure of the switch SW1. When the switch SW1 is opened in this state after discharging, the transistor Q1 is conducted for a predetermined time by the charging current from positive power source +B. When the motor M rotates in the predetermined amount, the actuators of switches SW2A, SW2B are switched to shut off the driving current of the motor M. When the motor M is stopped in the midway, the transistor Q1 is turned OFF after the capacitor C1 is charged.

Description

[Detailed description of the invention] The present invention relates to a motor drive circuit.

In general, in electronic machines, etc. (for example, tape recorders, televisions, etc.), operation knobs that are used relatively infrequently are placed together in one place as appropriate to prevent dirt from being contaminated by external dust, etc. Some have doors that open and close. Therefore, it is desired that the drive circuit for the door opening/closing motor suitable for the purpose of use as described above be economically inexpensive. SUMMARY OF THE INVENTION In order to satisfy the purpose of use of the device as described above, it is an object of the present invention to provide a motor drive circuit that can perform forward/reverse rotation of a motor for opening and closing a door with a simple configuration and at low cost.

This purpose will be explained in more detail.

As mentioned above, the drive motor used to open (or close) the door rotates in response to the start command, and when it has rotated a predetermined amount, that is, when 1.A is completely opened or closed. It needs to stop automatically. For this purpose, it is conceivable to detect when the motor rotates by the predetermined amount and cut off the drive current for the motor.

By the way, in the event that an accident occurs in which it is not possible to detect that the motor has rotated by the predetermined amount, or even if it is detected, the drive current cannot be cut off, the door must be opened (
Even after the motor is closed (or closed), drive current continues to be supplied to the motor in order to continue rotating, causing the motor to become overloaded, which may generate heat and cause a fire.

This invention prevents the motor from continuing to operate in an overloaded state.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The figure is an electrical wiring diagram showing a motor drive circuit, and the power supply system is composed of two power supplies, a positive power supply element B and a negative power supply -B, with respect to a midpoint B. SWI is the operation switch 5W2A and 5W for opening and closing the door.
Reference numeral 2B denotes a switch whose operator is switched by the rotational drive of the remoter M. transistor Q
1 and Q2 are transistors for driving the motor M,
Zener diodes DI and D2 are inserted in series between the bases of the transistor Q1.02, and are driven at a constant voltage so that the driving torque of the motor M is constant. Capacitor C inserted between the corephthal base of transistor Q1
The capacitor C2 and the resistor R4 inserted between the corephthal base of the transistor Q2, the resistor R3, and the transistor Q2 are time constant elements, and the resistor R5 and the resistor R6 are the current stabilizing resistors of the transistor Q1 and the transistor Q2. It is. Also, one terminal of the drive motor p4 for closing the door is connected to the connection point (midpoint B) of the Zener diodes DI and D2, and the other terminal is connected to the positive power source B or They are connected to the negative power source -B, respectively, and are rotated forward or reverse by driving the transistors Ql and Q2 to open and close the door.

When the switch SWI is closed with the operators of the switches 5W2A and 5W2B on the solid line side shown in the figure, the power from the positive power supply terminal B (relative to the middle point B) to the switches SW28 and SWI
, a current flows through the Zener diode D1 through the resistors R1 and R3, and a constant voltage is applied to the base and emitter of the transistor Q1, which turns on and connects the motor M from the positive power supply B to the resistor R5 and the transistor Q1. A drive current that has passed through the circuit is supplied. By closing this switch SWI, the charge in the capacitor C1 is instantly discharged via the low resistance R1. By opening the switch SWI in this post-discharge state, the charging current from the positive power supply element B flows through the resistor R3 to the Zener diode D1, and is applied as a reverse bias voltage. This results in transistor Q
A constant voltage is applied to the base of 1. That is, when the switch SWI is closed, the motor M is driven at a constant voltage by the current flowing through the transistor Q1 from the positive power supply element B, and even if the switch SWI is opened, the capacitor C1 remains unchanged for a while. Due to the charging current of transistor Q1
is electrically connected, a constant voltage is applied to the motor M, and the motor M is driven with a constant driving torque. The motor M is driven at a constant voltage as described above, and when its rotation reaches a predetermined value, the switch SW
The operators '2A and 5W2B are switched to the side shown by the broken line, and the drive current of the motor M passing through the l transistor Q1 is cut off. A time constant is determined by the capacitor C1 and the resistor R3 so that the switch 5W2A2B is switched before the charging of the capacitor CI is completed.
Since the base of the transistor Q2 is reverse biased by the charging current through R4 and the forward Zener diode D2, the transistor Q2 remains off, so that the direction of rotation of the motor M is cut off midway. It will never change.

In addition, if due to mechanical causes etc. while the motor M is rotating,
Motor M stops, which causes switches 5W2A and 5W2 to
Even when B is not switched, when the terminal voltage of the Zener diode D1 due to the charging current of the capacitor C1 becomes lower than the Zener voltage, the transistor Q1 is turned off and the motor M is stopped, thereby ensuring the safety of the motor. can be achieved. Next, when the operation switch SWI is closed when the switches 5W2A and 5W2B are in the state shown by the broken lines, the
-The transistor Q is
2, the motor M is driven at a constant voltage, and the direction of the drive current is opposite to that in the case where the motor M is driven by the transistor Q1, so the direction of rotation of the motor M is reversed.

As described in -1-, this invention includes a motor M and a Y transistor Q that controls on/off the drive current flowing through the motor.
1, Q2, switch S W 2 B, etc., a first control system that controls the operation of the switch, and a second control system that controls the operation of the switch.
a control system and a third control system, and a capacitor CI that sets a predetermined period longer than the time during which the motor rotates by a predetermined amount.
or a timer consisting of a time constant circuit including C2,
The first control system controls the switch to cut off the drive current when it is detected that the motor M has rotated by a predetermined amount, that is, controls the switch to cut off the drive current when the motor M has rotated by a predetermined amount. The second control system controls the switch so as to cause the drive current to flow in accordance with the starting command of the first mode, that is, controls the operation switch SWI. It is composed of a control system that turns on transistors Ql and Q2 that are turned on when operated, and a third control system is configured to flow the drive current only during a predetermined period set by the timer after the start command. In other words, the transistor Ql is controlled by the charging current of the capacitor C1 or C2.
For example, the transistor Q2 is configured to have a control system that turns on the transistor Q2, and the second control system and the third control system give priority to cutting off the drive current rather than passing the drive current. Ql, Q2 and switch SW
2 B are connected in series, so that even if the motor M rotates by a predetermined amount, the drive current to the motor will not be cut off due to a failure of the switch or its second control system. Even if there is, the third
Since the drive current to the motor is cut off by the control system, it is possible to prevent the motor from generating heat due to overload of the motor.

[Brief explanation of drawings]

The figure does not show one embodiment of the present invention, but is an electrical wiring diagram of a motor drive circuit. M...Motor, SWl...Operation switch, 5W2A
, 5W2B...Switch switched by motor, Q1 + Q2...Transistor, DI, D2...
...Zener diode, CI, C2...capacitor, R3, R4...resistance.

Claims (1)

[Claims] A motor, a switch that controls on/off the drive current flowing through the motor, a first control system, a second control system, and a third control system that control the operation of the switch, and a motor that rotates the motor by a predetermined amount. a timer for setting a predetermined period longer than time, and the first control system controls the switch to cut off the drive current when it is detected that the motor has rotated by a predetermined amount. , a second control system controls the switch so as to flow the drive current in response to the motor start command, and a third control system controls the switch only during a predetermined period set by the timer after the start command. controlling the switch to cause the drive current to flow;
Moreover, a motor drive circuit characterized in that the second control system and the third control system are configured to give priority to cutting off the drive current rather than flowing the drive current.