JP2707079B2 - 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] The rotation detecting transistor and the driving transistor are sequentially turned on by the induced electromotive force of the DC motor so that the rotation by the external force is continued, and the pulse generated in the armature winding at the commutation switching point of the motor is used. In this way, the detection transistor is turned off instantaneously, so that it is not restarted after the motor is restrained, and the high-speed cutoff is performed as an emitter follower type so that the rotation detection transistor operates in the active region. It is a motor control circuit. [Background Art] For example, in a toy car, once driven (running), the driving does not stop unless the switch is turned off. Therefore, if the running is stopped, more electric energy than necessary is consumed and uneconomical. In addition, excessive load was applied to the motor and other mechanisms, shortening the life of the toy car and causing trouble. In order to solve this problem, a stop positioning mechanism is provided in the rotating system so that the binding current does not flow at the high-speed stop position of the motor, and a rotation mechanism that prevents the brush and the commutator from contacting at the stop position is used. ing. However, such a stop positioning structure is complicated and liable to break down, and requires an adjusting operation during assembly. For this purpose, the present applicant has proposed a control circuit for a DC motor as shown in FIG. (Japanese Patent Application No. 62-97082).
This control circuit includes a rotation detecting transistor Q11 and the like which are turned on by the induced electromotive force of the DC motor M, and a driving transistor Q12 which is turned on by the detecting transistor Q11 and supplies a driving voltage E to the DC motor. Prepare.
Also, at the switching point of the commutator of the DC motor, the detection transistor Q1
The terminal connected to the armature winding of the DC motor and the detection transistor are connected so that 1 is momentarily turned off. When an external force is applied to the motor M to forcibly rotate the motor M, an induced electromotive force is generated, whereby the rotation detecting transistor Q11
Is turned on, and the driving transistor Q12 is turned on. Therefore, the electric motor M keeps rotating. With the rotation of the electric motor M, the detection transistor is periodically forcibly turned off by a pulse generated in the armature winding at the polarity switching point of the commutator. However, as long as the motor generates induced electromotive force due to the inertia of the rotating system, the detection transistor
Q11 immediately returns to ON, so the driving transistor Q
12 is also turned on and rotation is maintained. The above-mentioned pulse functions as a sampling pulse for detecting the constraint (rotation stop) of the motor. When the motor is restrained, the induced electromotive force becomes extremely small immediately before the stop, and when the detection transistor Q11 is turned off by the above pulse generated at the rectification switching point, the detection transistor can no longer be turned on. . Therefore, the driving transistor Q12 is also turned off, and the motor stops. [Problems to be Solved by the Invention] In the control circuit of FIG. 4, it is necessary to connect a collector load resistor R11 and a base current limiting resistor R12 to a detection transistor Q11 whose base is connected to a terminal of the motor M, Also, it is necessary to connect the current limiting resistor R13 to the base of the transistor Q12 connected to the collector of the transistor Q11, and the number of circuit components is relatively large. Further, in order to control the driving transistor Q12 on / off by the detection transistor Q11, the transistor Q11 is used.
Must be operated in a large amplitude, and must be used in the saturation and cut-off regions. Therefore, since there is carrier accumulation in the base region of the transistor Q11, even if the base / emitter of the transistor Q11 is reverse-biased by a pulse instantaneously generated in the armature winding at each polarity switching point of the commutator of the motor M, Q11 May not turn off completely. Even if Q11 is turned off instantaneously, there is a case where Q12 does not turn off because Q12 also has carrier accumulation in the base region. Therefore, when the motor M is restrained, the restraining current flows without turning off the driving transistor Q12, and the circuit and the motor M may be damaged. SUMMARY OF THE INVENTION In view of this problem, an object of the present invention is to simplify the circuit configuration, and to ensure that the rotation detecting transistor is periodically turned off so that the supply can be reliably shut off during the restraint. [Means for Solving the Problems] The control circuit of the DC motor of the present invention is turned on by an induced electromotive voltage generated at a terminal of the DC motor, and has an armature winding for each polarity switching point of the commutator of the motor. A rotation detection transistor Q1 having a control input connected to one terminal of the electric motor so as to be momentarily turned off periodically by a pulse generated in the motor, and is directly connected so that an output current of the rotation detection transistor becomes a control current. When the rotation detecting transistor is turned on, it is turned on to supply a driving voltage to the terminal of the DC motor, and is turned off in accordance with the periodic turning off of the rotation detecting transistor. The transistor Q2 is connected between its current output terminal and the other terminal of the motor as a load resistance of the rotation detecting transistor, and has its control input ; And a resistor R1 for actuating the rotation detecting transistor in the non-saturated region by exerting a negative feedback action to. [Operation] Every time the rotation detecting transistor Q1 is momentarily turned off, the driving transistor Q2 is turned off, power supply to the motor is cut off, and an induced electromotive voltage accompanying rotation of the motor is detected. Since the transistor Q1 operates in the active region, the transistor Q1 performs a fast and reliable turn-off operation. When the motor is restrained, the induced electromotive voltage becomes extremely small immediately before the stop, and once the detection transistor is turned off, it cannot be turned on again. At this time, since the input control current (base current) of the drive transistor is reduced by the detection transistor which operates in the active region and the output current is reduced as the induced electromotive voltage decreases, the turn-off of the drive transistor is ensured. Happens. 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). An emitter-collector of a driving transistor Q2 for supplying a power supply voltage E is connected in series to a terminal T1 of the motor M, and a collector-emitter of a rotation detecting transistor Q1 is directly connected in series to a base of the transistor Q2. I have. The base of the detection transistor Q1 is connected to a terminal T1 of the motor M, and the emitter is connected to a terminal T2 (ground potential) of the motor M via a resistor R1. These transistors Q1 and Q2 are connected so that the ON state is self-held. That is, once Q1 turns on,
The collector current becomes the base current of Q2, turning on Q2. Therefore, the collector voltage of Q2 rises and the drive voltage is supplied to the motor M. At this time, a base current is supplied from the collector of Q2 to Q1, so that the ON state of Q1 is maintained. 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 is proportional to the rotational speed N of the armature. E _n = A · N (A is a constant) the base-emitter forward voltage V of E _n is the transistor Q1
Beyond _BE1 , base current flows through resistor R1 and Q1
Turns on. Therefore, the transistor Q2 is also turned on, and the forward rotation continues. After the electric motor M is started in this way, if, for example, the battery car hits an obstacle and the electric motor M is restrained and stopped, the circuit in 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. The rotational position of (b), in the winding L ₃ is short-circuited, the windings L _1, L ₂ and are parallel and (c)
The rotational position series between winding L ₁ and L ₃ is in parallel with winding L _2. 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. Voltage)
Occurs. Since the connection state similar to that shown in FIG. 2B occurs six times per rotation of the armature, this pulse voltage is generated every 60 degrees. Therefore, in FIG. 1, for example, when the control circuit is turned on and the motor M is rotating forward, a negative pulse generated between the terminals T1 and T2 causes the base of the detection transistor Q1 to rotate.
Since the emitters are reverse-biased, these transistors are momentarily turned off every 60 ° 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 Q1 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 Q1 can no longer turn on Can not. Therefore, the control circuit is turned off. In the control circuit of FIG. 1, the resistor R1 inserted into the emitter of the transistor Q1 acts as a negative feedback for the collector current of Q1. That is, when the base current of Q1 increases and the collector current attempts to increase, the emitter voltage increases and the base current decreases. Therefore, the transistor Q1 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 Q1 can be completely and instantaneously turned off by a pulse generated in the armature winding at the switching point of the commutator with the rotation of the motor M. Therefore, the constraint detection is performed reliably. Since the collector current of the transistor Q1 is the base current of the transistor Q2, the value of the resistor R1 can be determined so that the transistor Q2 operates in a substantially saturated region when turned on. Also, suppose that when Q2 is on and electric motor M is rotating, it is restrained. Q2 reaches the cutoff region after passing through the active region and turns off. That is, when the motor M is rotating, its terminal
A voltage substantially equal to the power supply voltage E is generated at T1. Therefore Q1
, The base current is sufficient to flow through Q2, and Q2 is turned on while the base current is overdriven. When the motor M is decelerated to be locked, the potential of the terminal T1 is rapidly reduced, and the collector current of Q1 (base current of Q2) is reduced. For this reason, Q2 once operates in the active region where the DC amplification factor of the base current becomes the collector current, so that Q1 is momentarily turned off by the pulse noise of the electric motor M as described above, so that Q2 is immediately turned on. 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 amplification factor at the end of the saturation region,
f _b: base cutoff frequency, tau _c: few life time of carriers) therefore the collector current I _c of the collector layer of the base current I _B1 h _FE times (I _c =
When the transistor is turned off from the active region of h _FE · I _B1 ), the denominator and the numerator of the first equation are 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. When the motor control circuit of the embodiment is applied to a toy car, if the user pushes the toy car forward, the circuit is turned on and continues to run, or the obstacle is prevented from running,
The circuit is turned off instantly when the driving wheels are 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 a push switch that short-circuits the collector and the emitter of the transistor Q1 or Q2. The stop switch may be, for example, a push switch that short-circuits the base and the emitter of the transistor Q1 or Q2. If these start switches or stop switches are provided, in addition to the start and stop by the external force of the electric motor M, the start / stop by the switches can be controlled. [Effects of the Invention] As described above, when the DC motor is forcibly rotated by an external force, the rotation is detected by the induced electromotive force and the drive transistor is turned on to continue the rotation, and the rotation is detected during the rotation. The motor transistor is periodically turned off instantaneously to ensure that rotation and stop detection based on the induced electromotive force is performed periodically, and when the motor is restrained and stopped, the induction at the time when the rotation detection transistor turns off is performed. When the electromotive voltage is low and it is not turned on again, the driving transistor is turned off and the voltage supply is cut off. Therefore, by automatically turning on / off the drive circuit by forcibly rotating and restraining the electric motor, an operation similar to an inertial operation like a flywheel can be obtained by electrical control and with a simple circuit configuration. Further, since the rotation detection transistor is periodically turned off by using a pulse periodically generated in the armature winding at the commutation switching point of the motor, and thus the drive transistor is turned off, the rotation detection is repeatedly performed. The operation is more reliable than the method of judging the rotation / restriction stop by finely discriminating the voltage level of the induced electromotive force, and even if the terminal voltage of the motor is at the power supply potential, the induced electromotive voltage accompanying the rotation / stop is obtained. Can be reliably detected in the power-off state due to the turning off of the drive transistor to discriminate rotation / restriction stop without erroneous operation. Furthermore, there is no need to incorporate a special pulse oscillator, making it easy and inexpensive to manufacture. it can. Further, since a negative feedback resistor is provided so as to operate the rotation detecting transistor Q1 in the active area, it operates at high speed with almost no delay of on / off switching. Therefore, even a minute negative pulse generated at the commutation switching point of the motor can be used. The detection transistor Q1 can be reliably turned off, and just before the restraint stops, the induced electromotive voltage of the motor decreases, the output current of the active rotation detection transistor Q1 decreases, and the output is controlled. Since the operating point of the driving transistor Q2 to which the input is directly connected shifts from the saturation region to the active region, when the detection transistor Q1 is turned off, the driving transistor Q2 is reliably turned off without a time delay. / It is possible to more reliably perform the detection of the stop of the restraint and the automatic power cutoff at the time of the restraint without malfunction.

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. FIG. 4 is a conventional control circuit diagram. In still code used in the drawings, M ...... motor Q ₁ ...... rotation detecting transistor Q ₂ ...... driving transistor R ₁ ...... resistor L ₁ ~L ₃ ...... armature windings C ₁ ~C ₃ ...... rectifier Children B ₁ , B ₂ … brush T ₁ , T ₂ … terminals.

Claims (1)

(57) [Claims] One of the DC motors is turned on by an induced electromotive voltage generated at a terminal of the DC motor and periodically turned off periodically by a pulse generated in an armature winding at each polarity switching point of the commutator of the DC motor. A rotation detection transistor having a control input connected to the terminal, and a direct connection so that an output current of the rotation detection transistor becomes a control current, and when the rotation detection transistor is turned on, is driven to the terminal of the DC motor. A drive transistor that is turned on to supply a voltage and is turned off with the periodic turning off of the rotation detection transistor; a current output terminal as a load resistance of the rotation detection transistor; It is connected between the other terminal of the motor and has a negative feedback effect on its control input, so that the rotation detecting Control circuit for a DC motor having a resistor and to operate the Njisuta in unsaturated.