KR920000257Y1 - Power circuit - Google Patents

Abstract

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Description

Overcurrent limiting device of motor drive circuit

1 is a schematic circuit diagram of an overcurrent control circuit of a conventional motor.

2 is a motor drive circuit diagram according to the present invention.

3 is a logic diagram of the current limiting circuit of the motor driving circuit diagram of FIG.

* Explanation of symbols for main parts of the drawings

6: Amateur 7 field coil

11: temperature sensor 12: magnetic sensor

15: control logic circuit 20: comparator

21: CPU 22D flip flop

23: output circuit

The present invention relates to an overcurrent limiting device of a motor driving circuit, and more particularly, to an apparatus for regulating a magnetic current of a motor driving circuit by replacing an overcurrent of a motor with a temperature and sensing the same.

In order to limit the overcurrent generated when the motor is driven, conventionally, overcurrent control is effectively performed by using a contactor, which is a kind of an external resistor and an interrupter. In the conventional motor overcurrent control circuit shown in FIG. 1 of such a configuration, a plurality of resistors (RA, R1, R2, R3, R4,) are connected in series, and both ends thereof each have an input power width and an armature of the motor. It is connected to the side 6. A plurality of contacts 1 to 5 are connected in parallel for each connection point between the input power supply side and the resistor R4 and each connection point between the resistors. (7) is the series coil of the motor and (8) is the shunt coil of the motor. 9 is a shunt field current limiting resistor. Therefore, the current flows to each contactor and the current is limited through each resistor to control the overcurrent generated at the start of the motor. In the case of over howling (plugging braking), too, the contactor (1 to 5) was opened and closed sequentially to limit the overcurrent generated in braking.

However, the conventional apparatus described above was unable to perform a complete protection against overcurrent. It is therefore an object of the present invention to provide a lower means for performing more reliable current control.

In order to achieve this purpose, the present invention limits the current by controlling the output of the switching transistor by using a microprocessor, and simultaneously adjusts the current reference value according to the temperature change by using a temperature sensor to appropriately set the current limit. To choose.

Hereinafter, with reference to the accompanying drawings will be described in detail the operation and effect of the present invention.

Referring to FIG. 2, which shows a driving circuit for driving a motor, (D1) is a flyback diode that continuously flows current from a power supply, and (D2) is a plugging diode that is turned on only when plugging braking. 6 denotes an armature of the motor, 7 denotes a field coil, 9 denotes a current amplifier, and TR1 denotes a motor driving switching transistor. The motor may be rotated forward and reverse with power applied according to the connection of the contactors C1 and C1 'or C2 and C2'.

In addition, the magnetic sensor 12 attached to the power supply side of the motor detects a magnetic field corresponding to the current during overload and generates a voltage output. This magnetic sensor 12 preferably comprises a hall sensor. Reference numeral 11 denotes a temperature sensor that detects heat generation of the field coil. These signals are input to the control logic circuit 15. 3 shows the control logic circuit 15 in detail.

The comparator 20 and the CPU 21 detect the overcurrent of the motor and control the driving signal of the motor. The CPU 21 also detects overheating of the motor. The CPU 21 converts the A / D converter 17 for converting the voltage signal transmitted from the magnetic sensor 12 into a digital signal and the converted comparison signal of the A / D converter 17 within itself. Since it includes a comparison unit 19 for comparing with a reference voltage set low for the over-current, control the motor drive output signal outputting a control signal corresponding to the overheat signal from the temperature sensor 11 Done.

The flip flop 20 is driven in accordance with the enable signal from the comparator 20 and the drive signal from the CPU 21, and preferably consists of a D-type flip flop. The output from this flip flop 22 is sent to the logic output circuit 23. This logic output circuit 23 is constituted by a NA ND gate so that the output is controlled in accordance with a control signal from the CPU 21.

Referring now to FIG. 2 again, after the contacts Cl and Cl 'or (C2 and C2') are connected, the drive signal is output to the (Pl) terminal of the control logic circuit 15. Is driven and a spherical pulse is applied to the motor. The motor will rotate forward and backward in response to this signal.

If an overload is applied to the motor at this time, overcurrent occurs in the power supply line of the motor. The magnetic sensor 12 senses this current and outputs the corresponding voltage output to the terminal P3. The comparator 20 of FIG. 3 outputs a ″ high ″ status signal to the output compared according to the signal. The ″ high ″ signal disables the D flip flop 23 and prevents the new output signal from passing through the output circuit 23.

In addition, when the controller is overheated by the overcurrent, the temperature sensor 11 detects this and transfers it to the CPU 21 via the P2 terminal of the control logic circuit 15. At this time, the CPU 21 compares the sensed voltage raised by the overcurrent transmitted from the magnetic sensor 12 through the terminal P3 with the reference voltage in itself.

If the comparison voltage is higher than the reference voltage, the CPU 21 outputs a signal capable of disabling the output circuit 23 to prevent the signal output from the flip flop 20 from passing through the output circuit 23. . This forms the current limiting circuit of the motor.

As described above, the current limit due to the conventional resistance caused excessive power consumption, but by using the device according to the present invention, the motor can be protected according to the more accurate overcurrent control effect, and power consumption can be reduced.

Claims (1)

A temperature sensor 11 attached to one side of the motor to detect overheating of the motor M; A magnetic sensor 12 attached to a power supply line of the motor for detecting an overcurrent of the motor M; A comparator (20) for comparing the voltage output from the magnetic sensor (12) with a reference voltage; A / D converter 17 for converting the voltage transmitted from the magnetic sensor 12 into a digital signal when the overheat signal is transmitted from the temperature sensor 11 and the comparison signal converted by the A / D converter And a CPU 21 configured to compare a reference signal in itself with a comparator 19 for generating a signal for blocking the final output; A flip flop 22 which is operated by a drive signal from the CPU 21 and is disabled according to a signal generated from the comparator 20 when an overcurrent occurs; And outputting the output signal of the flip-flop 22 and output circuit 23 disabled by the control signal output from the CPU 21 when overcurrent and overheating occur. Overcurrent limiting device in the circuit.