KR900001110B1 - Arrangement for starting electric motor - Google Patents

Abstract

The circuit for forward or backward driving of small DC motor includes a first and a second level comparator (20,30) detecting counter electromotive current caused by stoppage or direction change of a motor, a first and a second Darlington circuits (40,50) flowing the rush current to a ground line, and a circuit (70) biasing the first and the second comparators (20,30) by providing the ground path of the base current of transistors (Q9,Q12) for driving the level comparators when the counter electromotive current is detected.

Description

DC motor positive reverse rotation drive circuit

1 is a conventional DC motor forward reverse drive circuit.

2 is a block diagram of the present invention.

3 is a circuit diagram of an embodiment incorporating the block diagram of FIG. 2 in accordance with the present invention.

4 is a waveform diagram comparing an output state of a conventional circuit according to an input condition with a circuit of the present invention.

* Explanation of symbols for main parts of the drawings

10: bridge type reverse rotation drive plate 20, 30: level comparators 1 and 2

40, 50: Darlington configuration transistors 1 and 2

60: motor speed determination reference voltage stage 70: level comparator bias stage

The present invention relates to a direct-current motor driving circuit capable of driving a small direct-current motor in both the forward and reverse directions, and detects the counter electromotive voltage generated during motor braking and direction change using a level comparator composed of transistors. The present invention relates to a small DC motor driving circuit capable of absorbing inrush current generated by voltage and allowing immediate and stable forced braking and rotational direction change in any direction of motor driving.

In a circuit for driving a small DC motor that requires both driving and speed control in both directions such as a reel motor, a capstan motor and a loading motor of a video tape recorder, in particular, a stable braking and a change of direction, a direction of current applied to the motor is conventionally used. A simple bridge-type circuit was used to change the braking and direction. In such a conventional circuit, when the motor stops driving or changes the rotation direction, the braking or direction change is not immediately realized due to the inrush current caused by the counter electromotive voltage generated in the motor. There could be a problem that does not get the desired operating characteristics.

Accordingly, an object of the present invention is to solve the above problems and to provide an efficient small DC motor driving circuit which can achieve immediate and stable braking and direction change when driving a small DC motor.

Hereinafter, embodiments of the present invention as described above will be described in detail with reference to FIGS. 2, 3, and 4 as follows.

2 is a block diagram of the present invention, the bridge type forward reverse drive stage 10 for integrally driving the forward and reverse rotation of the motor, and the level for detecting the counter electromotive voltage generated during motor braking or direction change Comparator 1 (20) and level comparator 2 (30), Darlington transistor 1 (40) and Darlington transistor 2 (50), and motor for improving the absorption efficiency when absorbing inrush current by detecting counter voltage. A motor speed determination reference voltage stage 60 capable of controlling the speed of the motor by determining a voltage applied to the voltage level, and a level comparator for providing a bias to the level comparator 1 20 and the level comparator 2 30 when the counter voltage is detected. The bias stage 70 is comprised.

3 is a detailed circuit diagram of the present invention configured as shown in FIG. 2, wherein Q ₁ -Q ₁₄ is a transistor, D ₁ -D ₈ is a diode, R ₁ -R ₅ is a resistor, ZD is a zener diode, Vcc is a power supply voltage, V _REF is the base bias voltage of transistor (Q ₁₄ ), I _S1 -I _S4 is the constant current source, Fin is the forward rotation input signal terminal, Rin is the reverse rotation input signal terminal, 1 and 2 are the motor drive output terminals, 3 is the motor The speed determination reference voltage terminal, M represents a small DC motor, and Vcc represents the voltage of the motor speed determination reference voltage terminal 3.

In the block diagram of FIG. 2, the bridge type forward rotation drive stage 10 corresponds to transistors Q ₁ -Q ₆ and resistors R ₁ -R ₄ , and the level comparator 1 20 is a transistor ( Q ₉ , Q ₁₀ ), level comparator 2 30 corresponds to transistors Q ₁₁ , Q ₁₂ , and Darlington configuration transistor 1 40 corresponds to transistor Q ₇ , and Darlington configuration Transistor 2 50 corresponds to transistor Q ₈ , motor speed determination reference voltage terminal 60 corresponds to control diode ZD and diodes D ₁ -D ₄ , and level comparator bias stage 70. Corresponds to transistors Q ₁₃ , Q ₁₄ and diodes D ₅ -D ₈ and resistor R ₅ .

Referring to the circuit operation of the present invention having the configuration as described above is as follows.

The bridge type reverse rotation drive terminal 10 has a high rotational input signal terminal (Fin) high (Vc + 2V _D or more, Vcc or less, but V _D is a diode turn-on voltage), and a reverse rotation input signal terminal (Rin). Low is V _D + V _CE (Sat) or less, except that V _CE (Sat) is the voltage between the collector and emitter of the NPN transistor when the base voltage of transistor Q ₃ is V _D. Since + V _CE (Sat) <2V _BE (where V _BE is the turn-on voltage between the base actors of the transistor), transistors Q ₃ , Q ₄ and Q ₅ are turned off and the base voltage of transistor Q ₁ is V _C. Since + 2V _D (where V _C is greater than or equal to 2V _BE (sat) and less than Vcc-2V), transistors Q ₁ and Q ₂ are on and transistor Q ₆ is saturated. At this time, the motor drive output terminal 1 has a voltage of Vc, and the motor drive output terminal 2 has a voltage of V _CE (sat). Therefore, the voltage applied to both ends of the motor is Vc-V _CE (Sat). This case is called forward rotation more than one time.

When low is applied to the forward rotational input signal terminal Fin and high is applied to the reverse rotational input signal terminal Rin, the base voltage of the transistor Q ₁ is V _D + V _CE (Sat) <2V _BE, so that the transistor Q ₁ , Q ₂ and Q ₆ are turned off, and the base voltage of transistor Q ₃ is Vc + 2V _D, so transistors Q ₃ and Q ₄ are on and transistor Q ₅ is saturated. At this time, the motor drive output terminal 2 has a voltage of Vc and the motor drive output terminal 1 has a voltage of V _CE (sat). Accordingly, the voltage applied to both ends of the motor is Vc-V _CE (sat). do.

The input state where high is applied to both the forward rotation input signal terminal (Fin) and the reverse rotation input signal terminal (Rin) should not exist. When both are applied, the base voltage of the transistors (Q ₁ , Q ₃ ) is V. _{Since D} + V _CE (sat), transistors Q ₁ -Q ₄ are turned off, with transistors Q ₅ and Q ₆ in the vicinity of saturation at small current levels so that motor-driven output terminals 1 and 2 are both low. The motor stops.

In the level comparator 20, the transistor Q ₉ is always in the off state except when the counter electromotive voltage is generated as in the time point T _{1 of} FIG. 4, and the transistor Q ₁₀ is always in the on state. This transistor (Q _9), the base electric potential, the switching voltage which is twice the thermal voltage of the level comparator 20 of the; due (Thermal Voltage V _T is 26mV at room temperature) than always size.

Referring to the waveform diagram of FIG. 4, (a) of FIG. 4 is an input waveform applied to the forward rotation input signal terminal Fin, (b) is an application signal of the reverse rotation input signal terminal Rin, (c) and (d) are output waveforms of motor drive output terminals 1 and 2 of the conventional circuit as shown in FIG. 1, and (e) and (f) are output waveforms of motor drive output terminals 1 and 2 of the circuit of the present invention. , the time that the motor driving the output terminal 1, the transition from high to low as 4 degrees, the time (T ₁₎ to look at the time (T _1), the fourth degree (c) if the level comparator 20 in the absence as the first help The counter electromotive voltage becomes longer. When the level comparator 20 is present, the base potential of the transistor Q ₁ becomes low at the time T ₁ , and the motor driving output terminal 1 has the potential of Vc + counter voltage, so that the transistor Q ₁₀ is turned off and the transistor Q ₉ ) is turned on and the inrush current generated by the counter electromotive voltage is turned on by the transistors (Q ₅ , Q ₇ ) to the ground momentarily, so that the time when the motor drive terminal 1 transitions from high to low detects the counter electromotive voltage. As compared with the case where there is no level comparator 20, it becomes small enough to be ignored. The point of time when the level comparator 20 which detects the counter electromotive voltage is actually operated is a point at which the base potential of the transistor Q ₁₀ becomes larger than twice the thermal voltage of the base potential of the transistor Q ₉ . ₁ )

The principle of the counter voltage detection of the level comparator 2 30 at the time point T ₂ is also the same as the operation principle of the level comparator 1 20 at the time point T ₁ described above.

In the motor speed determination reference voltage terminal 60, the voltage applied to both ends of the motor by the voltage Vc of the motor speed determination reference voltage terminal 3 becomes Vc + V _CE (sat), thereby controlling the speed of the motor.

The Darlington transistor 1 (40) and the Darlington transistor 2 (50) are turned on when the counter voltage is detected to increase the efficiency of flowing the inrush current to ground, and the level comparator bias stage 70 detects the counter voltage. Provide a path for the base current of transistors Q ₉ and Q ₁₂ to flow through transistor Q ₁₃ to ground.

As described above, according to the circuit of the present invention, when driving a small DC motor in the forward and reverse rotation, the inrush current caused by the counter electromotive voltage generated when the motor is braked and the direction change is absorbed quickly and effectively, thereby making it possible to immediately and stably operate the motor in any direction. By providing a compact DC motor driving integrated circuit capable of switching the braking and rotation direction, driving and speed control in both directions such as reel motor, capster motor and loading motor of the video tape recorder set can be achieved. The small DC motor driving integrated circuit required can be provided.

Claims (1)

In a bridge type reverse rotation drive circuit for controlling a DC motor, a level comparator 1 (20) and a level comparator 2 (30) for detecting a counter electromotive voltage generated when the motor is braked or when the rotation direction is changed, and when a counter electromotive voltage is detected Darlington configured transistor 1 40, the Darlington configured transistor 2 (50), a transistor (Q ₉ wherein a two-level comparator (20, 30) during counter-electromotive voltage is detected to function to flow the surge current to ground, Q ₁₂ DC motor reverse rotation drive circuit comprising a level comparator bias stage (70) for providing a ground path of the base current.

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