JP2714941B2 - Control circuit of DC motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control circuit for a DC motor. [Summary of the Invention] A DC motor is driven forward and reverse by a pair of a forward drive transistor and a reverse drive transistor in a bridge configuration, and each drive transistor pair is turned on by detecting an induced electromotive voltage of the motor and turning on. And a motor control circuit configured to maintain the power supply once the motor is rotated by an external force so that the rotation is continued, and to prevent the motor from being restarted when the motor is restrained thereafter. [Related Art] For example, in a toy car, once driven (running), the driving does not stop unless the switch is turned off. Therefore, when the running is stopped, excessive electric energy is consumed, which is uneconomical. In addition, excessive load was applied to the motor and other mechanisms, shortening the life of the toy car and causing trouble. [Problems to be Solved by the Invention] It is conceivable that a centrifugal force switch is connected to an axle or a motor shaft of a toy car to turn on / off the motor and obtain operability like a flywheel car. However, when a centrifugal switch is used, it is difficult to switch between normal rotation and reverse rotation, and it is easy to break down. In view of this problem, the present invention can achieve the same operation as a centrifugal switch, and can easily be changed to a reversible switching type.
Once the drive is stopped, a DC motor control circuit that does not consume more electric energy than necessary, and extends the life and eliminates trouble without imposing an excessive load on the motor mechanism etc. The purpose is to provide. Another object of the present invention is to provide a simple circuit means for reliably operating a motor control circuit capable of controlling forward rotation, reverse rotation, and stop by an external force (rotation start, restraint stop) on a rotor of a DC motor. . [Means for Solving the Problems] A control circuit for a DC motor according to the present invention includes a first opposing side of a bridge for supplying a normal rotation drive voltage to a DC motor connected between two bridge points of the bridge. The first drive transistor Q12 on the positive power supply side whose output terminal is connected to the positive terminal of the motor and the second drive transistor Q12 on the negative power supply side whose output terminal is connected to the negative terminal
In order to supply a forward drive voltage to the motor,
A third driving transistor Q22 on the positive power supply side having an output terminal connected to the negative terminal of the motor on the second opposing side of the bridge
And a reverse drive transistor pair including a fourth drive transistor Q42 on the negative power supply side whose output terminal is connected to the positive terminal. The induced electromotive voltages of the forward rotation and the reverse rotation generated at the terminals of the motor are respectively detected and turned on to turn on the first and third drive transistors Q12 and Q22 on the positive power supply side constituting each drive transistor pair. At the same time, the positive and negative positive and negative motors of the electric motor are turned off instantaneously by the pulse generated in the armature winding at each polarity switching point of the commutator of the electric motor to instantaneously turn off the corresponding drive transistor on the positive power supply side. Terminal and the first and third drive transistors Q12, Q22
And a pair of rotation detecting transistors Q11 and Q21 connected to the control input terminals of the first and second transistors. A connection for connecting the positive and negative terminals of the electric motor and the respective control input terminals of the pair of rotation detecting transistors Q11 and Q12 via resistors R1 and R2, and the respective control input terminals of the pair of rotation detecting transistors. And the respective current output terminals, and the respective control inputs of the positive and negative terminals of the motor and the second and fourth drive transistors Q32 and Q42 on the negative power supply side constituting the drive transistor pair. Resistor R3, R4
And a connection that is cross-connected via the. [Operation] Each time the rotation detecting transistor Q11 (Q21) is momentarily turned off, an induced electromotive voltage accompanying rotation of the motor is detected. When the motor is restrained, the induced electromotive force becomes extremely small immediately before stopping, and once the detection transistor is turned off, it cannot be turned on again. Therefore, the drive transistor is also turned off, and the power supply is cut off. Also, since the rotation detection transistor Q11 (Q21) is not operated in the saturation region,
Since the rotation detecting transistor is reliably turned off by the noise pulse of the motor, the control for stopping the motor by the external force (restraint) to the rotor can be surely performed. Embodiment FIG. 1 shows a control circuit for a DC motor according to an embodiment of the present invention. This control circuit is incorporated in, for example, a toy battery car, and the motor M is a well-known DC three-pole (phase) type commutator motor (micromotor). The four drive transistors Q12, Q22, Q32, and Q42 are connected to a bridge, and an electric motor M is connected between two bridge points A and B. Transistors Q12 and Q32 on opposite sides of the bridge
Is turned on, a positive voltage E is applied between the terminals T1 and T2 of the motor M, and the motor M rotates forward. When the transistors Q22 and Q42 on the other opposing sides are turned on, the terminals T1 and T2 of the motor M are turned on.
A reverse voltage is applied in between, and reverses. When the rotation detecting transistors Q11 (for normal rotation) and Q21 (for reverse rotation) for detecting the induced electromotive voltage of the motor M are provided, and when these transistors Q11 or Q21 are turned on,
The drive transistor Q12 or Q22 is turned on, and the drive voltage is supplied to the terminal of the electric motor M. Note that the drive transistor Q32 or Q42 in which the drive transistor Q12 or Q21 is on the opposite side is automatically turned on when Q12 or Q22 is turned on, as described later. Since the forward rotation circuit and the reverse rotation circuit in FIG. 1 are symmetrical,
Hereinafter, the normal rotation circuit will be described in detail. The driving transistor Q12 is a PNP, and its base is NPN
The collector-emitter of the rotation detecting transistor Q11 is directly connected in series. The base of the detection transistor Q11 is connected to the terminal T1 of the motor M via the resistor R1,
The emitter is connected to a terminal T2 (ground potential) of the motor M via a resistor R2. These transistors Q11 and Q12 are connected so that the ON state is self-held. That is, once Q11 is turned on, its collector current becomes the base current of Q12, and Q12 is turned on. Therefore, the collector voltage of Q12 rises and the drive voltage is supplied to the motor M. At this time, the base current is supplied from the collector of Q12 to Q11, so that the ON state of Q11 is maintained. When a drive voltage is supplied to the terminal T1 of the motor M, the terminal T1
Drive transistor Q3 with its base connected via resistor R4
2 turns on. Therefore, a voltage in the forward direction is supplied between the terminals T1 and T2 of the motor M. The control circuit for reverse rotation uses the resistors R1 and R2 as the emitter load resistance and the base resistance of the rotation detection transistor Q21. Terminal T2 and drive transistor Q4
The two bases are coupled via a resistor R3. The motor control circuit of FIG. 1 is kept off in the stationary state. Here, the motor M is rotated by an external force so that a positive voltage is generated at the terminal T1 of the motor M and a negative voltage is generated at the terminal T2 (this direction is defined as a forward rotation). Induced electromotive force E _n armature is proportional to the rotational speed N. E _n = AN (A is a constant) the base-emitter forward voltage V of E _n is the transistor Q11
Beyond _BE1 , base current flows through resistors R1 and R2, turning on Q11. Then the emitter-base of Q12 →
A current flows into the base of the driving transistor Q42 through the path from the collector to the emitter of Q11 to the resistors R2 and R3, and the transistors Q12 and Q42 are turned on. At this moment, the voltage at point B rises,
The base current flows to the driving transistor Q32 through the
Turns on. As a result, the terminal T1 of the motor M is at the positive potential, the terminal T2 is at the ground potential, and the drive transistor Q42 is turned off. Conversely, when the motor M is reversely rotated by an external force, the transistors Q21, Q22, and Q42 are turned on in order, and the motor M
Keeps reversing. After starting the electric motor M in this way, for example, when the electric motor M is restrained and stopped by hitting an obstacle with a battery car, the control circuit of FIG. 1 is automatically turned off according to the following principle. Figure 2 a~c shows the armature circuit of the motor M of Figure 1, the commutator C ₁ three-pole of the delta winding L ₁ of the three phases in the example, L _2, L _3, C _2, C ₃ and a pair of brushes B ₁ and B ₂ .
The rotational position of (a), the series of winding L ₂ and L ₃ is in parallel with winding L ₁ between the brush B _1, B _2. In the rotational position of (b) is a winding L ₃ shorted windings L _1, L ₂ and are parallel and in series with the winding L ₁ and L ₃ in the rotational position of (c) is a winding L ₂ Are in parallel. Accordingly, the winding impedance between the brushes sharply changes at the rotational position of (b), and as shown in the waveform diagram of FIG. 3, the steep positive and negative pulse voltages (susceptances) between the terminals T1 and T2 of the electric motor M due to electromagnetic induction. (Referred to as voltage). The connection state similar to that of FIG.
This pulse voltage occurs every 60 ° because it occurs six times per revolution. Accordingly, in FIG. 1, for example, when Q11, Q12, and Q32 are on and the motor M is rotating forward, the terminals T1,
Since the base and the emitter of the detection transistor Q11 are reverse-biased by the negative pulse generated during T2, these transistors are momentarily turned off every 60 degrees of rotation of the motor M. However, as long as the motor M is rotating, the control circuit is kept on by its positive induced electromotive voltage. When the motor M is restrained by an external force, the restraining current generally tends to continue to flow, but the transistor Q11 is turned off by a negative pulse generated in the connection state as shown in FIG. . If is reduced to the rotational speed close to the stop at this point, have an induced electromotive force E _n of terminals T1, T2 is significantly reduced, E _n ≦ V _BE1, and the sensing transistor Q11 can no longer turn on Can not. Therefore, the control circuit is turned off. In the control circuit of FIG. 1, the resistor R2 inserted into the emitter of the transistor Q11 acts as a negative feedback on the collector current of the transistor Q11. That is, when the base current of Q11 increases and the collector current tries to increase, the emitter voltage increases and the base current decreases. Therefore, the transistor Q11 can be operated in the active region, the excess minority carriers in the base region can be eliminated, and the turn-off delay time can be reduced. Therefore, the transistor Q11 can be completely turned off instantaneously by a pulse generated in the armature winding at the commutator polarity switching point with the rotation of the motor M. Therefore, the constraint detection is performed reliably. Since the collector current of the transistor Q11 is the base current of the transistor Q12, the value of the resistor R2 can be determined so that the transistor Q12 operates in a substantially saturated region when turned on. Also
If the motor M is restrained while Q12 is on and the motor M is rotating, Q12 reaches the cutoff region after passing through the active region and turns off. That is, when the electric motor M is rotating, a substantially power supply voltage E is generated at the terminal T1. Therefore, Q11 is substantially on, and a sufficient base current flows in Q12, and Q12 is on in a state where the base current is overdriven. When the motor M is decelerated to reach the restraint, its terminal
The potential of T1 drops rapidly, and the collector current of Q11 (base current of Q12) is reduced. For this reason, Q12 once operates in the active region where the collector current is substantially twice the DC amplification factor of the base current, so that Q11 is momentarily turned off by the pulse noise of the electric motor M as described above, so that Q12 is immediately turned on. Turns off. When Q12 turns off, Q32 also turns off. Note that the delay time T _stg when the transistor is turned off is
As is well known, it is represented by the following equation. (I _B1 : Base current at ON, _IB2 : Reverse recovery base current to neutralize excess base minority carriers at OFF, I _C : Collector current, h _FE : DC emitter gain at the end of saturation region,
f _b : base cutoff frequency, τ _C : lifetime of minority carriers in the collector layer) Therefore, the collector current I _C is h _FE times the base current I _B1 (I _C : h
_{When the} transistor is turned off from the active region of _FE・ I _B1 ), the denominator and the numerator of the first equation become substantially the same, and t _stg ≒ 0. Therefore, according to the control circuit of FIG. 1, when the electric motor M is constrained, the turn-off does not fail and the detection of the confinement and the interruption of the power supply are reliably performed. A negative pulse generated between the terminals T1 and T2 of the motor M is applied to the base and emitter of the reverse rotation detection transistor Q21. This pulse is generated by a capacitor C connected between the bases of the transistors Q11 and Q21. Absorbed at ₀ . Therefore, the transistors Q21, Q22, and Q42 do not turn on. When the electric motor control circuit of the embodiment is applied to a toy car, if it is pushed forward or backward to run the toy car, the circuit is turned on and continues running, and the obstacle is prevented from running or the driving wheels are blocked. The circuit turns off instantly when stopped by hand. Therefore, since there is no operation of a slide switch or the like which is particularly difficult for an infant, the operation can be performed as desired. Further, since the starting current and the restraining current of the DC motor (both of which are larger than those at the time of running) do not flow, the energy of the battery or the like is extremely little wasted. In addition, trouble is reduced because unreasonable load is not applied to the motor, mechanism, etc.
The life of the toy car can be extended. In addition, since the circuit is simple, these functions can be easily obtained at low cost, and unlike the method of detecting and controlling the current flowing through the motor like an overcurrent limiter, the supply voltage of the circuit fluctuates (decreases). This does not impair this function. This control circuit is not limited to a toy car, but can be used for various applications such as an automatic opening / closing curtain device, an automatic opening / closing blind device, and the like in accordion curtains and blinds. A start switch or a stop switch may be added to the control circuit shown in FIG. 1 if necessary. The start switch may be, for example, a push switch for short-circuiting between the collector and the emitter of the transistor Q11 or Q12 for normal rotation. The stop switch may be, for example, a push switch that short-circuits the base and the emitter of the transistor Q11 or Q12. If these start switches or stop switches are provided, control of start / stop / forward rotation / reverse rotation by switches can be performed in addition to the start and stop by the external force of the electric motor M. [Effects of the Invention] As described above, the present invention is intended to reliably operate a motor control circuit capable of controlling forward rotation, reverse rotation, and stop by external force (rotation start, restraint stop) on a rotor of a DC motor,
Do not operate the rotation detecting transistor in the saturation region, and connect a resistor connected between the positive and negative terminals of the motor and the control input terminal (base) and current output terminal (emitter) of each rotation detecting transistor. Since the forward drive circuit and the reverse drive circuit are shared, it is possible to reduce the number of components of the motor control circuit that can control forward, reverse, and stop with an external force to the rotor of the DC motor, thereby reducing the cost. Can be manufactured

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a control circuit diagram of a DC motor showing one embodiment of the present invention, FIGS. 2a to 2c are armature circuit diagrams of the motor, and FIG. 3 is a terminal voltage waveform diagram of the motor. It is. In still code used in the drawings, M ...... motor Q11, Q21 ...... rotation detecting transistor Q12, Q22, Q32, Q42 ...... driving transistor L ₁ ~L ₃ ...... armature windings C ₁ ~C ₃ ...... a commutator B ₁ ~B ₂ ...... brush T1, T2 ...... terminal.

Claims (1)

(57) [Claims] In order to supply a forward drive voltage to a DC motor connected between two bridge points of the bridge, a first drive on a positive power supply side having an output terminal connected to a positive terminal of the motor on a first opposite side of the bridge. A forward drive transistor pair including a transistor and a negative drive second drive transistor having an output terminal connected to the negative terminal; and a motor on a second opposite side of the bridge for supplying a reverse drive voltage to the motor. A driving transistor pair for reverse rotation, comprising a third driving transistor on the positive power supply side having an output terminal connected to the negative terminal thereof, and a fourth driving transistor on the negative power supply side having an output terminal connected to the positive terminal; The induced electromotive voltages of the forward rotation and the reverse rotation generated at the terminals are respectively detected and turned on to turn on the first and third drive transistors on the positive power supply side constituting each of the drive transistor pairs. At the same time, the positive and negative of the electric motor are turned off instantaneously by a pulse generated in the armature winding at each polarity switching point of the commutator of the electric motor to instantaneously turn off the corresponding drive transistor on the positive power supply side. A pair of rotation detecting transistors connected to a terminal and a control input terminal of each of the first and third driving transistors; a positive and negative terminal of the electric motor and each control input terminal of the pair of rotation detecting transistors; And a connection for mutually connecting the respective control input terminals and the respective current output terminals of the pair of rotation detecting transistors to each other, a positive and negative terminal of the electric motor, and the drive transistor. And a connection for cross-connecting, via a resistor, each of the control input terminals of the second and fourth drive transistors on the negative power supply side forming a pair. Control circuit.