KR930001678Y1 - Arrangement for starting electric motor - Google Patents

Abstract

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Description

DC motor drive circuit

1 is a conventional DC motor drive circuit diagram.

2 is a block diagram of the present invention.

3 is a detail of FIG.

4 is a signal waveform at the time of overload detection.

* Explanation of symbols for main parts of the drawings

1: Electric motor drive part 2: DC motor

3: switch control unit 4: switch unit

5: overload detection unit

The present invention relates to a DC motor driving circuit, and more particularly, to a motor driving circuit for stopping the rotation of the motor by detecting the motor control signal when the motor is overloaded.

As shown in FIG. 1, a conventional motor driving circuit includes four transistors Q ₁ -Q ₄ and low R ₁ -R ₅ .

The transistors are used to control the rotation direction of the motor according to the motor control signals S ₁ and S _2. Q _l and Q ₂ are PNP transistors, and Q ₃ and Q ₄ are NPN transistors. In FIG. 1, when the first selection signal S ₁ is applied as “H”, the transistor Q ₃ is turned on. Therefore, the collector terminal of Q ₃ is at a "L" becomes a do so on Q ₂ to the base terminal is "L" in Q _2. Thus, the power supply voltage Vcc flows through Q ₂ → motor → Q ₃ and the motor rotates in a specific direction.

Next, when the second selection signal S ₂ is selected, Q ₁ and Q ₄ are turned on in contrast to the above description, and the motor rotates in the opposite direction to the selection of the first selection signal S ₁ .

In such a conventional gaseol, the motor continues to rotate as long as a selection signal for selecting the rotational direction of the motor is input and power is applied. That is, even if the lamp is overloaded, the electric current continues to flow in the motor. As a result, overcurrent flows to the motor and the motor tends to be damaged. This example is apparent in the case of automatically performing focusing or zooming in the camera apparatus.

In other words, if focusing or zooming is done by using a motor, the focus ring or zoom ring is completely turned to one side and it can no longer be rotated. At this time, if the power supply voltage is continuously supplied to the motor, overcurrent flows to the motor. do. To prevent this, a separate device is used to stop the rotation of the motor when the focus ring or zoom ring is completely turned to one side. For example, a limit switch should be attached. However, attaching the limit switch to the focus ring is quite difficult and can easily break during mechanical shock or handling. However, if the switch is not attached or damaged during handling due to the difficulty in attaching the switch, leaving the motor in an overload condition will cause the motor to fail, shorten the life span, and increase the current consumption.

The present invention aims to provide a DC motor driving circuit which automatically detects when an overcurrent flows to the motor and blocks the selection signal, thereby cutting off the power flowing to the motor.

To this end, the present invention provides a switch unit 4 for cutting off or connecting the motor rotation selection signal to the conventional motor driving circuit 1, and an overload detector 5 for detecting an overcurrent of the motor, as shown in FIG. ) And a switch control unit 3 for controlling the switch unit in accordance with the signal of the overload detection unit.

3 shows an embodiment of the present invention showing the block diagram of FIG. 2 in detail. In FIG. 3, the dashed blocks indicated by the same reference numerals as those of FIG. 2 indicate the same parts as those of FIG.

In the drawing, 5 is provided with a comparator to compare the overload detection voltage Vdet applied to the resistor R ₅ and the reference voltage Vret, and outputs a "high" signal to the output terminal when an overcurrent flows in the motor driving circuit 1. It is an overload detector, and 3 is provided with two flip-flops FF ₁ and FF ₂ to input rotation selection signals S ₁ and S ₂ of the motor to the input terminal D of the flip-flop, and to the reset terminal R. A reset circuit consisting of a capacitor and a resistor is connected. The clock signal of the flip-flop uses the output of the comparator (OP ₁ ) and the flip-flop A switch control unit for outputting a signal, and 4 is a switch unit for supplying or interrupting the selection signal S ₁ .S ₂ to the motor drive circuit 1 using, for example, a transistor.

Hereinafter, an operation process will be described with reference to the accompanying drawings.

When the power supply (Vcc) is initially applied, the flip-flops (FF ₁ , FF ₂ ) are reset by a reset circuit composed of C _1, R _6, and C ₃ , C ₇ . Since the output to "high" the transistors (Q _5, Q ₆₎ of the switch unit 4 is in the on state. This is called an initial state.

In the initial state, when the one-way rotation signal of the motor (for example, S ₁ ) is applied to "high", the selection signal of the "high" state is applied to the base of the transistor Q ₃ because Q ₅ is on. ) transistor (Q ₃₎ of the turns on. Therefore, the collector stage of the transistor Q3 is turned low and the transistor Q ₂ is turned on.

Therefore, the power current flows through Q ₂ → motor → Q ₃ and the motor M is driven. This is called steady state.

When the motor is overloaded in the normal phase state, a large current flows in the motor, and as shown in (b) of FIG. ₄ , the voltage Vref applied to the resistor R ₅ becomes large. Therefore, the voltage Vdet becomes larger than the reference voltage Vref so that the output signal Vo of the comparator OP ₁ becomes "high" and this signal is input as the clock signal of the flip-flop of the switch controller 3. . Since the flip-flop FF ₁ has an input signal S ₁ of the flip-flop as an output. The output floats in the " low " state and therefore the transistor Q ₅ of the switch section 4 is turned off. Therefore, the control signal S ₁ applied to the motor driver 1 is cut off and the transistors Q ₃ and Q ₂ are turned off to stop the rotation of the motor. At this time, the overload detection voltage Vdet falls back to the "low" state and the motor drive is reduced to the initial state.

Here, when another selection signal S ₂ is applied, as in the case of the selection signal S ₁ described above, the motor M rotates in the opposite direction due to the current flowing through the transistors Q ₁ and Q ₄ . The overload detection process is detected as in the case of the selection signal S ₁ described above.

As described above, the present invention automatically detects when the motor is overloaded and cuts off the selection signal so that the power is cut off to stop the rotation of the motor, thereby preventing the motor from being worn due to overload.

Claims (3)

In the DC motor drive circuit having a motor drive unit (1) for driving the motor by determining the rotational direction of the motor in accordance with the rotation selection signal input consisting of a plurality of transistors and resistors, connected to one side of the motor drive unit of the motor Detection means for detecting an overload, control means for controlling the switch unit 3 according to the input rotation selection signal and a signal detected from the detection means, and a rotation selection signal and a control signal inputted from the control means. And a switching means for blocking or connecting the rotation selection signal of the motor. 2. The apparatus of claim 1, wherein the detecting means for detecting the overload includes a comparator OP ₁ for comparing the voltage Vdet applied to the resistor R ₅ with the reference voltage Vref by a current flowing in the motor. DC motor drive circuit, characterized in that. 2. The DC motor drive circuit according to claim 1, wherein the control means for controlling the switch is used as a clock signal of two flip-flops (FF ₁ , FF ₂ ).