JP2822059B2 - DC motor control circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor control circuit, and more particularly to a DC motor drive circuit which cuts off a drive current when the DC motor is restrained. It is suitable.

[Summary of the Invention]

A transistor for turning on a driving transistor for supplying a driving voltage to the DC motor and a transistor for turning off the driving transistor are separately provided so that the driving transistor can be kept sufficiently on as long as an induced electromotive force is generated. Thus, the present invention provides a DC motor drive circuit in which heat generation of the drive transistor is prevented so that electric energy is not wasted.

[Conventional technology]

2. Description of the Related Art There is known a DC motor control circuit that senses an induced electromotive force generated in proportion to the rotation speed of an armature and controls driving of a DC motor. FIG. 2 is a circuit diagram showing a control circuit of a conventional induction electromotive force sensing type DC motor.

This circuit, along with the turn on the transistor Q ₁₀ in the induced electromotive force E _M generated at the terminal T _1, T ₂ of the DC motor M,
Turns on the transistor Q ₂₀ in the output current of the transistor Q ₁₀ applies a driving voltage of the power source E to the DC motor M.
Then, the driving transistor Q ₂₀ periodically turned off by instantaneously turning off the transistor Q ₁₀ in pulse generated in the armature winding with the polarity switching point of the commutator of a DC motor M, the drive voltage of the DC motor M Instantaneously shut off periodically.

Since the DC motor M armature if not constrained state be interrupted driving voltage continues to rotate by transmural, inductive electromotive force E _M is subsequently generated. Therefore, transistor Q ₁₀
And Q ₂₀ is turned on again. However, since the induced electromotive force E _M and the DC motor M is restricted not generated, the transistor Q _10, Q ₂₀ is not turned on again once turned off. Therefore, this circuit can prevent the binding current from flowing when the DC motor M is locked.

[Problems to be solved by the invention]

Since the magnitude of the induced electromotive force E _M is proportional to the rotational speed of the armature, very small immediately before the restraint stop. Thus, rotation becomes the output current of the sensing transistor Q ₁₀ is small, it can not be driven by the driving transistor Q ₂₀ sufficient on state immediately before the restraint stop. That is, the conventional control circuit driving transistors Q ₂₀ and induced electromotive force E _M is small and has a configuration that operates in an unsaturated region. Therefore, the waste of electric energy DC motor M is increased power consumption near the driving transistor Q ₂₀ to restraining the stop state, the driving transistor Q ₂₀
Had a problem of generating heat.

The present invention has been made in view of the above-described problem, and has as its object to enable a driving transistor to operate in a sufficiently ON state as long as induced electromotive force is generated.

[Means for solving the problem]

Control circuit for a DC motor of the present invention, the rotation detecting transistor Q ₁ which is turned on by the induced electromotive force E _M generated at the terminal T _1, T ₂ of the DC motor M, the rotation detecting transistor Q ₁ is turned on is turned on by the output current when being, a driving transistor Q ₂ supplies a drive voltage to the DC motor M, is turned on by a pulse P generated in the polarity switching of the commutator of the DC motor M, the DC a blocking transistor Q ₃ to instantaneously cut off the driving voltage supplied to the motor M periodically, in order to increase the effect of turning on the cut-off transistor Q ₃ by the pulse P, the motor terminal T ₁ And an inductor L connected to the

[Action]

The effect of turning off the driving transistor Q ₂ carried out in a blocking transistor Q _3. Accordingly, the rotation detecting transistor Q ₁ is may be performed only acts to turn on the driving transistor Q _2, the driving transistor regardless of the magnitude of the induced electromotive force E _M as long as the DC motor M is rotated Q ₂ can be operated in saturation.

Further, the blocking transistor Q ₃ by the pulse P generated in the polarity switching of the DC motor M by the action of the inductor L to ensure periodic operation for instant-on, the DC at the time of restraining the electrical lock detection and control motor M Improve the function to stop automatically.

〔Example〕

FIG. 1 is a circuit diagram of a control circuit of a DC motor showing one embodiment of the present invention.

This motor control circuit is kept off when the DC motor M is stationary. In the DC motor M, the motor terminal T ₁ is connected to the positive electrode of the power supply E via the inductor L,
Motor terminal T ₂ are the drain electrode D of the driving transistor Q ₂
And the source electrode S is grounded.

The base of rotary detecting transistor Q ₁ is the resistor R ₁
It is connected to the motor terminal T ₂ through. Rotation detecting transistor Q ₁ is a PNP transistor is used.
Thus, the positive motor terminal T _1, when a negative voltage to T ₂ is a direct current motor M is rotated by an external force to generate the rotation detecting transistor Q and negative induced electromotive force E _M is applied to the base ₁ turns on. When the rotation detecting transistor Q ₁ is turned on, collector current flows through the resistor R ₃ connected between the ground and its collector. Thus, a positive voltage is generated at the collector of the rotation detecting transistor Q _1, which is applied to the gate electrode G of the driver transistor Q _2. Accordingly, the driving transistor Q ₂ is turned on, and the DC motor M and the power source E is connected to the closed circuit. Therefore,
When the drive voltage of the power supply E is applied, the DC motor M
Keeps spinning.

Motor terminal T ₁ is grounded via a capacitor C and a resistor R _5. Therefore, when the pulse P at the polarity switching point of the armature (not shown) during rotation of the DC motor M is generated, positive voltage appears at the connection point between the capacitor C and the resistor R _5. By this positive voltage is applied to the base through a resistor R _4, it is cut off transistor Q ₃ periodically instant on. In the embodiment between the positive electrode of the motor terminal T ₁ and the power source E, it is provided with an inductor L which only a significant resistance component with respect to pulse P. Therefore, the operation is ensured for periodically turning off the blocking transistor Q ₃ by the pulse P.

It is grounded gate electrode G of the driver transistor Q ₂ through the collector and emitter of the blocking transistor Q _3. Therefore, the blocking transistor Q ₃ by the periodic instant on, the driving transistor Q ₂ is periodically turned off. When the driving transistor Q ₂ is turned off, the driving voltage to the DC motor M is not applied, because if unrestrained DC motor M continues to rotate by transmural resistance, the motor terminal T ₂ negative induced electromotive force E _M follows. Therefore, the rotation detecting transistor Q ₁ is the period of the pulse P is generated also sustain the ON state, the collector electrode is held at a positive potential. Therefore, when the cut-off transistor Q ₃ is turned off, the driving transistor Q ₂ is turned on since the positive voltage applied to the gate electrode, the DC motor M
Is applied again.

The magnitude of the induced electromotive force E _M is proportional to the rotational speed of the armature. Therefore, the rotational speed of the armature is reduced to the rotational speed close to the stop, induced electromotive force generated at the motor terminals T ₂
E _M becomes significantly smaller and the rotation sensing transistor Q ₁ can no longer be turned on. Accordingly, the driving transistor Q ₂ is remains being turned off by the pulse immediately before the stop restraint, control circuit is cut-off state.

Thus, the circuit embodiment since a dedicated transistor Q ₃ to turn off the driving transistor Q _2, the induced electromotive force E as _long as _M is occurring driving transistor Q ₂
Can be operated in a sufficient ON state.

Therefore, when it is the rotation speed of the DC motor M as described above is low, a driving transistor Q ₂ can eliminate a disadvantage to operate in an unsaturated region, good is no waste of heat generation or power driven Can be performed.

Also, since the inductor L is provided which ensures instantaneously turned off blocking transistor Q ₂ and easily generate the pulse P, it is possible to detect the constrained state with high precision, it is possible to reliably stop automatically when restraint .

〔The invention's effect〕

As described above, the present invention provides a rotation detecting transistor that is turned on by an induced electromotive force generated at a terminal of a DC motor to turn on the DC motor driving transistor, and a polarity switching point of a commutator of the DC motor. In addition to providing an interrupting transistor for instantaneously turning off the driving transistor by being instantaneously turned on by a pulse generated in the armature winding, and an inductor for assisting the generation of the pulse, When the DC motor is driven, the driving transistor can always be kept sufficiently on, and the driving transistor can be periodically and instantaneously turned off. Therefore, even if the rotation speed of the DC motor decreases to a value close to the restraint stop, the driving transistor can be operated in a saturated state, so that waste of electric energy and heat generation in the driving transistor can be suppressed. Also, despite the fact that the driving transistor is operated in the saturation region, the electrical constraint detection and control can be reliably performed, and the function of stopping the automatic constraint can be improved.

[Brief description of the drawings]

FIG. 1 is a control circuit diagram of a DC motor showing one embodiment of the present invention, and FIG. 2 is a control circuit diagram of a conventional DC motor. In the reference numerals used in the drawings, Q ₁ …… Rotation detecting transistor Q ₂ …… Drive transistor Q ₃ …… Cutting transistor M …… DC motor T ₁ , T ₂ …… Motor terminal E… Power supply P… ... Pulse L ... Inductor E _M ... Induced electromotive force.

Claims (1)

(57) [Claims] 1. A rotation detecting transistor which is turned on by an induced electromotive force generated at a terminal of a DC motor, and a driving voltage which is turned on by an output current when the rotation detecting transistor is turned on, and a driving voltage is applied to the DC motor. A driving transistor for supplying the DC motor, a turning-on transistor that is turned on by a pulse generated when the polarity of the commutator of the DC motor is switched, and periodically instantaneously cuts off the driving voltage supplied to the DC motor; A control circuit for a DC motor, comprising: an inductor connected to the motor terminal to increase an action of turning on the cutoff transistor by a pulse.