JP3564589B2 - DC motor control circuit - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control circuit for rotating and stopping a DC motor, and is used exclusively for a door mirror storage device of a car.
[0002]
[Prior art]
The conventional car door mirror storage device performs the opening and closing operation of the mirror by inverting the polarity of the power supply of the DC motor and changing the direction of rotation, and controls from the point that it does not matter the polarity of voltage or current. Used exclusively mechanical switches and electromagnetic relays.
[0003]
[Problems to be solved by the invention]
In the above-described conventional door mirror storage device for a car, in the opening and closing operation of the mirror, unnecessary electromagnetic waves due to chattering, which have a short life due to the contact point, are generated. Further, there is a problem that it is difficult to reduce the size to a certain degree or more, and depending on the type of the electromagnetic relay, the current consumption (hereinafter referred to as dark current) when the door mirror retracting operation is not performed is large.
[0004]
[Means for Solving the Problems]
The present invention has been made in view of the conventional problems, includes a switch for switching the polarity of the DC power supply applied to the DC motor in the opposite direction, when the DC power supply is switched, the DC motor starts rotating, After a lapse of a predetermined time, an overcurrent flowing when the rotation operation of the DC motor is forcibly stopped is detected, and an open collector type comparator IC, a semiconductor element, a resistor, and a capacitor that cut off a power supply of the DC motor are shut off. In the control circuit configured, even when the polarity of the DC power supply is switched, a bridge circuit including four diodes that outputs a voltage having a constant polarity, and operates using the voltage output from the bridge circuit as a power supply Two comparator circuits, one of which forms a flip-flop that always outputs a positive signal when the power supply polarity switches A comparator circuit configured to detect an overcurrent generated when a mechanical load is applied immediately before the DC motor stops, and to reset a flip-flop including the comparator circuit by the detection signal; The present invention proposes a DC motor control circuit including two field-effect transistors that are ON / OFF controlled by output .
[0005]
[Action]
A positive signal is output each time the polarity of the DC motor power supply is inverted, and the FF output, which is reset when the DC motor is forcibly stopped, is used as a FET control signal to rotate, stop, reverse, and stop the DC motor. Can be performed.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Even when the polarity of the DC power source is switched, two comparator circuits that operate using a voltage output from a bridge circuit composed of four diodes that output a voltage having a constant polarity as a power source. A flip-flop that always outputs a positive signal when it switches is configured, and the other detects an overcurrent that occurs when the DC motor is forcibly stopped rotating, and a flip-flop that configures a comparator circuit based on this detection signal. DC motor control circuit The DC motor is frequently rotated forward and reverse by a comparator circuit configured to reset the flip-flop and two field-effect transistors that are turned on / off by the output of the flip-flop.
[0007]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, S1 in the circuit diagram is a switch for manually changing the polarity of the power supply of the DC motor 1. By operating this switch S1, the polarity of the power supply of the DC motor is reversed after a momentary disconnection. The switch S1 is a break-make type switch which is temporarily disconnected at the time of operation in order to prevent a power supply short circuit.
[0008]
Next, a bridge circuit 2 composed of diodes D1 to D4 is for supplying power to the comparators IC1 and IC2, which always supplies forward power to the circuit even if the polarity of the power is inverted. The structure of the diode ZD1, the resistor R2, and the capacitor C1 is for stabilizing the power supply formed by the diode bridge circuit 2 at a constant voltage (hereinafter, referred to as Vcc). The operation of the circuit will be described based on the above configuration. First, when a positive power is applied to V1 and a negative (or 0V) power is applied to V2 by the switch S1, the comparator IC1 is connected to the (-) terminal by the capacitor C1 at 0V with respect to Vcc (hereinafter referred to as GND) and (+) Since the terminal is connected to the Vcc side by the capacitor C2, the (-) terminal instantaneously goes to the GND level and the (+) terminal goes to the Vcc level, and the comparator IC1 outputs a voltage almost close to Vcc. I do.
[0009]
In addition to the function described above, the capacitor C2 also serves to prevent the FF constituted by the comparator IC1 from being reset by noise. Here, assuming that the resistance is R3 = R4 << R5 = R6 = R7, the output of the comparator IC1 causes the (+) terminal of the comparator IC1 to charge the capacitor C3, and then to 1/2 Vcc by the resistors R3 and R4. The voltage of the difference between the divided voltage and Vcc is further divided by the resistors R5 and R7, and as a result, a voltage of 3/4 Vcc is added. In general, since the input impedance of the comparator is very high, a voltage of approximately 3/4 Vcc is applied to the (+) terminal by setting the resistors R3 to R7 to an appropriate value. On the other hand, after the capacitor C2 is charged, a voltage of 1/2 Vcc divided by the resistors R3 and R4 is applied to the (-) terminal through the resistor R6. Since the comparator IC1 is a comparator IC as described above, The (+) terminal> (-) terminal enables a stable state while substantially outputting the voltage of Vcc.
[0010]
Next, the output of the comparator IC1 is sent to the gates of field effect transistors (hereinafter referred to as FETs) FET1 and FET2 through resistors R15 and R16, respectively. Since V1 is positive and V2 is negative (or 0V), FET1 is reverse biased and is in the OFF state. Since FET2 is forward-biased to the gate, it is turned ON, and the DC motor 1 starts rotating by passing current through the path of the resistor R17, the diode D11, the DC motor 1, the FET2, and the resistor R18. The current at this time is defined as a steady current.
[0011]
Next, when the DC motor 1 mechanically stops after one rotation of the DC motor for a predetermined period, an overcurrent flows through the DC motor 1 and the current value becomes about twice or more the steady current. Due to this current, a voltage corresponding to the voltage drop is generated across the resistors R17 and R18. At this time, the voltage generated at the resistor R17 causes the diode D9 to be reverse-biased, so that the diode D9 is turned off, and the voltage generated at the resistor R18 is passed through the diode D10 and the resistor R14 to the comparator IC2. (-) Terminal. Diodes D9 and D10 form an OR circuit, and have a function of not only passing the voltage generated across the resistors R17 and R18 but also shifting the level of the voltage generated across the resistors R17 and R18 in the positive direction. That is, since the power of the comparators IC1 and IC2 is supplied from the diode bridge 2, the GND potential of the comparators IC1 and IC2 is one diode, and is in the positive direction from the potential of V2. It is indispensable when handling a signal having a direction voltage drop (about 0.7 V) or less.
[0012]
The comparator IC2 is a general comparator circuit in which a voltage obtained by dividing Vcc by resistors R11 and R12 is used as a reference voltage and hysteresis is provided by resistors R9 and R10. The voltage generated across the resistor R18 due to the overcurrent of the DC motor 1 is applied to the (-) terminal of the comparator IC2 through the resistor R14. When the reference voltage applied to the (+) terminal is set to be higher than the voltage generated across the resistor R18 by the steady current and lower than the voltage generated across the resistor R18 by the overcurrent, the comparator IC2 as shown in FIG. When the overcurrent flows, the output becomes the GND level.
[0013]
Utilizing the fact that the comparators IC1 and IC2 are open collectors, the outputs can be wired-ORed together, and when the output of the comparator IC2 goes to the GND level, the FF constituted by the comparator IC1 is reset and the comparator IC1 is reset. The FET 2 to which the output signal of the data IC 1 is applied to the gate is turned off, the power supply to the DC motor 1 is stopped, and the rotation is stopped. At this time, the (+) terminal of the comparator IC1 halves 1/2 Vcc (the voltage obtained by dividing Vcc by R3 and R4) by the resistors R5 and R7 because the output of the comparator IC1 is at the GND level. And the voltage becomes 1/4 Vcc. Since the (-) terminal of the comparator IC1 is at 1/2 Vcc, the comparator IC1 is in a stable state at the output 0 (GND level). That is, the operation of the FF is performed.
[0014]
The capacitor C4 is an integrating capacitor provided with a delay function for preventing malfunction due to noise and adjusting timing to mechanical operation. In addition, diodes D7 and D8 are used to rapidly discharge the electric charge stored in the capacitor C4 when the power sources of V1 and V2 are turned off. Similarly, the diode D5 is a diode of the capacitor C2. D6 is for accelerating the discharge of the capacitor C3.
[0015]
Next, when a negative (or 0 V) power is applied to V1 and a positive power is applied to V2 by operating the switch S1, the comparators IC1, IC2 and the peripheral circuits supplied with power from the diode bridge circuit 2 have the same configuration as described above. When the power is turned on, a voltage of approximately Vcc is applied to the gates of FET1 and FET2. In FET1 and FET2, FET1 is forward-biased and FET2 is reverse-biased, and FET1 is turned on, and the current to DC motor 1 is supplied to resistor R18, diode D12, DC motor 1, FET1, and resistor R17. Become a route. The OR circuit of the diodes D19 and D10 is turned off because the diode D10 is reverse biased, and the voltage generated at both ends of the resistor R17 is input to the circuit of the comparator IC2 through the diode D9. After this, the operation is exactly the same as the above-described operation, and the power is turned on, the DC motor is rotated once, the mechanical stop is performed, the FET is turned off, and the rotation is stopped.
[0016]
【The invention's effect】
According to the present invention, the DC motor control circuit enables semi-permanent life by turning on / off the power supplied to the DC motor by using a semiconductor, and forcibly stops the DC motor by using a comparator having a high input impedance. The mechanical delay of the generated overcurrent can be covered by selecting the time constant of the CR inserted into the input of IC2. Furthermore, in order to configure an FF with a comparator IC, an IC having two comparators built in one chip (for example, COMIC, NJR2903 manufactured by New Japan Radio Co., Ltd.) can be used, and there is an advantage that a separate power supply does not have to be made. Yes, since it is a CMOS, it can be operated with very little current. In addition, the generation of unnecessary electromagnetic waves can be reduced, the size can be reduced, and the dark current can be reduced.
[Brief description of the drawings]
FIG. 1 is an overall circuit diagram. FIG. 2 is a timing chart.
DESCRIPTION OF SYMBOLS 1 DC motor 2 Diode bridge circuit IC1 Comparator IC
IC2 Comparator IC
FET1 Field effect transistor FET2 Field effect transistors D1 to D12 Silicon diodes R1 to R18 Carbon resistors C1 to C3 Ceramic capacitor C4 Electrolytic or tantalum capacitor S1 Polarity switch

Claims (1)

A switch for switching the polarity of the DC power supply applied to the DC motor in a reverse direction, the DC motor starts rotating when the polarity of the DC power supply is switched, and after a predetermined time has elapsed, the rotation operation of the DC motor is forcibly performed; In a control circuit comprising an open collector type comparator IC, a semiconductor element, a resistor and a capacitor, which detects an overcurrent flowing when the power supply is stopped temporarily and cuts off the power supply to the DC motor, the polarity of the DC power supply is switched off. A bridge circuit composed of four diodes that output a voltage with a constant polarity even after switching, and two comparator circuits that operate using the voltage output from the bridge circuit as a power supply, one of which is a power supply polarity configure sure flip-flop a positive signal is outputted when the switched and the other DC motor mechanical load is immediately before stop Detecting an overcurrent occurring during took, detection and comparator circuit configured as to reset the flip-flop formed of the comparator circuit by a signal, the two field-effect output by the ON / OFF control of the flip-flop A DC motor control circuit, comprising a type transistor.

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