JP2589989B2 - 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 maintained, and the detecting transistor is generated by a pulse generated in the armature winding at the commutation switching point of the motor. It is configured to be turned off momentarily and not restarted after the motor is restrained, and the rotation detection and drive transistors are configured with FETs, and the current interruption is reliably performed by the pulse generated in the armature winding A motor control circuit as described above.

[Conventional technology]

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, unnecessary electric energy is consumed and the motor is uneconomical. In addition, an excessive load is applied to other mechanisms to shorten the life of the toy car or cause trouble.

In order to solve this problem, a stop positioning mechanism is provided in the rotating system so that the restraint current does not flow at the restraint 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.

[Means for solving the problem]

However, such a stop positioning structure is complicated and liable to break down, and requires an adjusting operation during assembly.

SUMMARY OF THE INVENTION In view of this problem, an object of the present invention is to provide a motor control circuit that can automatically stop locking by electrical detection and control. Another object of the present invention is to provide a motor control circuit in which power consumption of the control circuit is minimized.

[Means for solving the problem]

The control circuit of the DC motor according to the present invention includes a rotation detecting field-effect transistor Q1 connected to a terminal of the DC motor M and turned on by the induced electromotive force.

Further, a drive field effect transistor Q2 is connected to the rotation detection transistor Q1 and is turned on to supply a drive voltage to the terminal of the DC motor when the detection transistor Q1 is turned on.

The rotation detection transistor Q1 is configured to be momentarily turned off by a pulse generated in the armature winding at each polarity switching point of the commutator of the DC motor M.

[Action]

Every time the rotation detecting transistor Q1 is momentarily turned off, an induced electromotive voltage accompanying rotation of the motor is detected (sampled). Since the transistor Q1 is composed of an FET, even a small pulse of the armature winding generated at each rectification switching point can be used.
Turns off quickly and reliably. 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. Therefore, the motor stops.

〔Example〕

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 drive T for supplying the power supply voltage E to the terminal T1 of the motor M
The drain-source of MOSFET transistor Q2 (P-channel, enhancement type) is connected in series, and the drain-source of rotation detecting MOSFET transistor Q1 (N-channel, enhancement type) is directly connected in series to the gate of this transistor Q2. I have. The gate of the detection transistor Q1 is connected to the terminal T1 of the motor M, the drain (gate of Q2) is connected to the power supply E via the resistor R1, and the source is connected to the terminal T2 (ground potential) of the motor M. ing.

These transistors Q1 and Q2 are connected so that the ON state is self-held. That is, once Q1 turns on,
The drain potential drops, and the gate potential of Q2 drops
Q2 is turned on, and the drive voltage is supplied to the electric motor M. At this time, a positive voltage is supplied from the source of Q2 to the gate of 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 generated is proportional to the rotational speed N of the armature.

E _n = A · N (A is a constant) E _n is applied to the gate of the transistor Q1 Q1 is turned on. Therefore, the transistor Q2 is also turned on, and the forward rotation continues.

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. 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. Therefore, at the rotational position (b), steep positive and negative pulse voltages due to the reactance voltage are generated between the terminals T1 and T2 of the electric motor M as shown in the waveform diagram of FIG. 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 ON and the motor M is rotating forward, a negative voltage is applied to the gate of the detection transistor Q1 by a negative pulse generated between the terminals T1 and T2. , Transistor Q1 is 60
な り It turns off momentarily with every rotation,
Q2 also turns off. However, as long as the motor M is rotating, the control circuit is kept on by its positive induced electromotive voltage.

Here, if the electric motor M is constrained by an external force, the constraining current 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, the induced electromotive force E _n of terminals T1, T2 have remarkably decreased, detecting transistor Q1 can no longer turn on. Therefore, the control circuit is turned off.

As described above, according to the control circuit shown in 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. In particular, since FETs are used for the rotation detection transistor Q1 and the drive transistor Q2, it is possible to reliably turn off the negative pulse of minute energy as described above that occurs at the rectification switching point of the electric motor M. Furthermore, the power consumption in the control circuit is very small.

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 constrained current flowing to the motor like an overcurrent limiter, the supply voltage of the circuit fluctuates (drops). 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.

Bridge connection using four basic circuits of FIG.
If a motor is connected between the bridging points, a control circuit for normal and reverse rotation can be configured. In this case, the channel polarity of the bridge and FETs Q1 and Q2 on each side is the direction (polarity) of the power supply.
Select as appropriate according to

〔The invention's effect〕

As described above, when the DC motor is forcibly rotated by an external force as described above, the rotation is detected by the induced electromotive force, the drive transistor is turned on, and the rotation is connected. To instantaneously turn off, so that rotation and stop detection based on the induced electromotive voltage is periodically and reliably performed.When the motor is restrained and stopped, the induced electromotive voltage at the time when the rotation detection transistor is turned off is low. By not turning on again, the drive transistor is turned off and the voltage supply is cut off. Therefore, the drive circuit can be automatically turned on / off by the forced rotation and restraint stop of the motor, and an operation similar to an inertial operation like a flywheel can be obtained by electrical control and with a simple circuit configuration. In addition, since mechanical means such as a centrifugal switch is not used for on / off control of the drive circuit,
Operation is reliable, stable, and long life.

In addition, since the rotation detection transistor is periodically and forcibly turned off instantaneously and the rotation is detected each time, the operation is more reliable than the method in which the voltage level of the induced electromotive force is finely discriminated and the rotation / restriction is determined. In addition, the detection transistor is momentarily turned off using a pulse periodically generated in the armature winding at the commutation switching point of the motor, so there is no need to incorporate a special pulse oscillator, and the circuit configuration is simplified. And inexpensive.

Further, since the rotation detecting transistor Q1 is constituted by a field effect transistor, the detecting transistor can be reliably turned off by a minute negative pulse generated at the rectification switching point of the motor. Therefore, it is possible to reliably perform the power supply cutoff at the time of restraint. In addition, since the driving transistor is also formed of a field effect transistor, the power consumed by the control circuit is extremely small, which is suitable for an energy saving device.

[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. In still code used in the drawings, M ...... motor Q ₁ ...... rotation detecting transistor Q ₂ ...... driving transistor L ₁ ~L ₃ ...... armature windings C ₁ ~C ₃ ...... commutator B _1, B ₂ … Brush T ₁ , T ₂ … Terminals.

Claims (1)

(57) [Claims] 1. A motor connected to a terminal of a DC motor and turned on by an induced electromotive force, and instantaneously turned off by a pulse generated in an armature winding at each polarity switching point of a commutator of the DC motor. A rotation effect field effect transistor, and a drive field effect transistor connected to the rotation detection transistor and turned on to supply a drive voltage to the terminal of the DC motor when the detection transistor is turned on. DC motor control circuit.