JPS6156709B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for a reversible DC motor.

In reversible DC motors used in various electrical equipment such as tape decks, when the control input signal of the control circuit is cut off, if braking is not applied at the same time, due to the inertia of the rotation system, the motor will continue to operate for a while.
It is well known that the DC motor continues to rotate. Therefore, in the case of tape decks and the like, various damage occurs due to this inertial rotation, and the necessity of a braking circuit becomes a problem. Therefore, for example, there are devices that electrically apply a drive input to reverse the DC motor for a certain period of time after the input signal is cut off, thereby producing a braking effect. However, in this method, if the inertia of the rotating system is not uniform, the braking effect may be insufficient or excessive, and there may be cases where the rotation starts to be reversed or cases where the rotation is not completely stopped. Furthermore, it is difficult in terms of circuitry to apply the inverted drive input for a certain period of time after the cutoff. On the other hand, there are systems that add a dedicated braking circuit separately from the motor drive circuit and short-circuit both ends of the DC motor when the input signal is cut off to generate a braking effect through dynamic braking. It has been difficult to create a braking circuit for a reversible DC motor that is driven in both directions.

The present invention improves the above-mentioned drawbacks, eliminates the need for a dedicated short circuit for braking, and always utilizes the drive circuit for forward and reverse rotation when the input signal for controlling the rotational direction is cut off. A braking circuit is formed by short-circuiting the DC motor, and at the same time as the input signal to the DC motor is cut off, a braking circuit is formed by the drive circuit, and dynamic braking is applied to the DC motor. In addition to instantaneous stopping, even if rotational force is applied to the DC motor for some reason while the motor is stopped, this braking circuit acts as a load and makes it difficult to rotate.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. As shown in the figure, a forward/reverse drive circuit for controlling a reversible DC motor M in the forward and reverse directions includes drive transistors Q1 to Q4, drive input signal level inversion. It is composed of transistors Q5 and Q6 for input signals, resistors R1 to R15, and switches S1 and S2 for input signals. A diode D1 is connected to the base of the driving transistor Q1.
The anode of a diode D2 is connected to the base of a driving transistor Q2, and the diodes D1 and D2 are connected to each other on the cathode side, and are driven through a resistor R9.
It is connected to the collector of a transistor Q7, which is an example of a brake switching element. The emitter of transistor Q7 is grounded, and the base of transistor Q7 is connected to power supply +B via resistor R5 and grounded via resistor R6. Diode D
3 has a cathode connected to the base of the transistor Q5, and an anode connected to the base of the transistor Q7. The diode D4 has a cathode connected to the transistor Q6 and an anode connected to the base of the transistor Q7. In addition, switch S1, S
2 is for applying an input signal for controlling the rotational direction of the DC motor M to the bases of the transistor Q5 and the transistor Q6. In the actual circuit, the signal from the external circuit is applied to the base of the transistor Q5 and the base of the transistor Q6, respectively. In this embodiment, for ease of explanation, a switch is shown as an example, and when the switch S1 is closed, the input signals are for forward rotation drive, and when the switch S2 is closed, the input signals are for reverse rotation drive. It is assumed that the information is entered separately.

Next, the operation of this circuit will be described. In a normal driving state, a well-known forward/reverse control operation is performed in response to opening/closing of the forward rotation drive input signal switch S1 or the reverse rotation drive input signal switch S2. At this time, since either the forward rotation drive input signal switch S1 or the reverse rotation drive input signal switch S2 is closed, the transistor Q5 (or Q6) is turned on.
Transistor Q3 (or Q4) turns on, and transistor Q, which is a switching element for control and driving, turns on.
2 (or Q1) is turned on, and the DC motor M rotates. At this time, one of the diode D3 and the diode D4 is turned on, and the base of the transistor Q7 is grounded, and the transistor Q7 is turned off. Therefore, the diode D1 and the diode D2 are originally turned off, and the drive circuit is not affected.
When the input signal to the DC motor M is cut off, that is, when no drive input signal is input (when both the forward rotation drive input signal switch S1 and the reverse rotation drive input signal switch S2 are open), the diode D3 and diode D4 are both turned off, and the base of transistor Q7 is connected to the power supply voltage R.
6/(R5+R6) times the potential is applied, turning on the transistor Q7, turning on the diode D1 and the diode D2, and supplying the power supply voltage to the bases of the driving transistor Q1 and the transistor Q2 through the resistor R7 and the resistor R11. Since the voltage divided by the parallel composite resistors and the resistor R9 is applied, the transistors Q1 and Q2
are both turned on, short-circuiting both ends of the DC motor M to form a braking circuit. In addition, when this input signal is cut off, a voltage obtained by dividing the power supply voltage by resistors R1 and R2 is applied to the base of transistor Q5, which turns on transistor R5, so that the base of transistor Q3 is grounded. As a result, the transistor Q3 is turned off. On the other hand, the power supply voltage is connected to the base of transistor Q6 through resistor R15 and resistor R.
Since the voltage divided by 14 is applied and the transistor Q6 is turned on, the base of the transistor Q4 is grounded and the transistor Q4 is turned off.
As a result of the above, when the drive input signal of the DC motor M is not input, both ends of the DC motor M are short-circuited by the drive transistor Q1 and the drive transistor Q2, so that dynamic braking is activated and the drive input signal is not input. After the cut-off, the DC motor M can be stopped instantly and its inertial rotation can be prevented.

As is clear from the above description, the present invention provides a reversible DC motor by providing a pair of control/drive switching elements (control/drive transistors Q1 and Q2 in the embodiment) in a forward/reverse drive circuit of a reversible DC motor. A drive circuit for forward and reverse rotation of a rotary DC motor,
Also serves as a braking circuit that short-circuits both ends of the motor,
A reversible rotary DC type, characterized in that it is provided with a drive/brake switching element that switches between the two circuits so that a drive circuit is formed when a rotational direction control input signal is applied and a braking circuit is formed when the input signal is cut off. This relates to a motor control circuit.

Therefore, according to the present invention, when a signal for controlling the rotational direction of the DC motor is not input, the drive circuit is used to short-circuit both ends of the DC motor as a control circuit. There is no need to add a dedicated circuit for this purpose, and since dynamic braking is performed at the same time as the control input signal is cut off, braking can be performed reliably without timing lag. In addition, in the present invention, even if a rotational force is applied from the outside for some reason while the DC motor is stopped, the braking circuit becomes a load, making it difficult to rotate, resulting in a very stable stopped state. Since a braking circuit that is independent of the direction of rotation of a DC motor can be easily realized at low cost using a pair of control/drive switching elements, it can be used in various electrical devices, and its practical value is extremely large.

[Brief explanation of the drawing]

The drawing is an electrical circuit diagram showing an embodiment of the present invention. M: DC motor, Q1, Q2: Control/drive transistor which is an example of control/drive switching element, Q3, Q4: Drive transistor, Q
5, Q6: Inversion transistor, Q7: Transistor which is an example of a drive/brake switching element, S1: Input signal switch for forward rotation drive, S2: Input signal switch for reverse rotation drive.

Claims (1)

[Claims] 1 By providing a pair of control/drive switching elements in the forward/reverse drive circuit of a reversible DC motor, it can serve as both the forward/reverse drive circuit of the reversible DC motor and a braking circuit that short-circuits both ends of the motor. Reversible rotation characterized in that a drive/brake switching element is provided for switching between the two circuits so that a drive circuit is formed when a rotational direction control input signal is applied and a braking circuit is formed when the input signal is cut off. Control circuit for type DC motor.