JPH0552149B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a motor protection device for preventing a brushless DC motor from being destroyed, and is particularly suitable for IC (integrated circuit). The purpose is to provide a motor protection device. (b) Conventional technology Brushless DC motors are currently widely used because they have a long life even when rotated at high speeds. The brushless motor is configured to rotate by detecting the position of the rotor and supplying a current according to the position of the rotor to a plurality of drive coils, and in order to increase the torque at startup, The current supplied to the drive coil at startup is set to be large.
Therefore, if the motor locks for a long time or continues to rotate at an abnormally low speed due to overload, heat generation and burnout of the drive coil will occur. When a motor lock occurs, the technology to immediately stop the motor drive and prevent damage was developed in Japanese Patent Application Laid-Open No. 1983.
-Described in Publication No. 154385. According to the above publication, a pulse of a predetermined period is generated by detecting the back electromotive force of the drive coil, and the rotation of the motor is detected by discharging a capacitor constituting the time measuring means using the pulse. . Therefore, in the case of the above-mentioned publication, when the motor lock occurs, the counter electromotive force is no longer generated, and the pulse is no longer generated, the terminal voltage of the capacitor exceeds a predetermined level, and it is possible to detect that the motor lock has occurred. . (c) Problems to be solved by the invention However, as in the above-mentioned publication, the method for detecting back electromotive force requires detecting the voltage across the drive coil, one end of which is connected to the power supply, so the entire detection circuit is must be connected to a high voltage power supply.
Therefore, the circuit in the above publication must be constructed entirely of high-voltage elements, and when the power supply voltage is high,
The drawback was that it was difficult to integrate it into an IC. Also,
Since the power supply voltage is applied to the entire circuit, it also has the disadvantage of being vulnerable to surge voltages. (d) Means for solving the problems The present invention has been made in view of the above-mentioned points. a Zener diode which is connected and returns the kickback pulse generated by the drive coil; an AND gate which ANDs the signals obtained at the input terminals of the first and second output circuits; and an output signal of the AND gate. The present invention is characterized in that it includes a capacitor whose charging and discharging are controlled accordingly, and a stop means which stops power supply to the first and second drive coils according to the terminal voltage of the capacitor. (E) Effect According to the present invention, the pulse width of the output signal of the AND gate can be increased, and the capacitor can be sufficiently discharged. As a result, the capacitance of the capacitor can be increased, and the value of the charging resistor can be decreased, thereby preventing an adverse effect on the bias current supplied to the IC. (F) Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention.
1 is a first drive coil, 2 is a second drive coil, and 3 is a Hall IC (a combination of a Hall element and a comparator) for detecting the position of the rotor driven by the first and second drive coils 1 and 2. IC), 4 is a waveform shaping circuit that shapes the waveform of the output signal of the Hall IC; 5 includes first and second transistors 6 and 7 whose emitters are commonly connected; a differential amplifier circuit that generates a first pulse train having the same phase as the output signal and a second pulse train having the opposite phase to the output signal; 8 , third and fourth transistors 9 whose base-emitter paths are cascade-connected; 10, which amplifies the first pulse train obtained at the collector of the first transistor 6 and supplies a corresponding current to the first drive coil 1.
The output circuit 11 includes fifth and sixth transistors 12 and 13 whose base-emitter paths are connected in cascade, amplifies the second pulse train obtained at the collector of the second transistor 7, and supplies a corresponding current to the second pulse train. a second output circuit for supplying the drive coil 2, 14;
15 is a first Zener diode whose cathode is connected to the output end of the first output circuit 8 and whose anode is connected to the input end of the first output circuit 8 ; 15 is a first Zener diode whose cathode is connected to the output end of the second output circuit 11 ; a second Zener diode 16 whose anode is connected to the input end of the second output circuit 11, respectively; 16, whose input end is connected to the first and second output circuits 8 and 11, respectively;
17 is an inverting transistor that inverts the output signal of the AND gate 16; 18 is charged by the power supply voltage (+V _CC2 ) via a charging resistor 19, and is discharged by the inverting transistor 17; 20 is the terminal voltage of the capacitor 18 and the reference voltage (+Vref)
This is a stop circuit that generates a stop signal to stop the operation of the waveform shaping circuit 4 when the terminal voltage becomes large. When the motor is rotating, a signal that changes synchronously to "H" and "L" is generated from the Hall IC 3, and after this signal is converted into a rectangular wave by the waveform shaping circuit 4, the differential amplifier circuit 5 is applied to Therefore, the first pulse train shown in FIG. 2A is generated at the collector of the first transistor 6 constituting the differential amplifier circuit 5 , and the second pulse train shown in FIG. 2B is generated at the collector of the second transistor 7. The first pulse train is applied to the first output circuit 8 and the second pulse train is applied to the second output circuit 11, respectively, and the first and second output circuits 8 and 11 apply the first and second drive coils 1 to
An operating current is supplied to and 2. Therefore, the output voltage of the first output circuit 8 is the same as that of the first drive coil 1.
In response to the kickback pulse and back electromotive force caused by this, the waveform becomes as shown in FIG. 2C, and the output voltage of the second output circuit 11 similarly takes the waveform as shown in FIG. 2D. Since the first and second Zener diodes 14 and 15 are connected between the input and output terminals of the first and second output circuits 8 and 11 , respectively, the kickback pulse exceeding the Zener voltage V _Z First and second output circuits 8 and 1
The voltage at the input terminal of the first output circuit 8 is as shown in FIG. 2E, and the voltage at the input terminal of the second output circuit 11 is as shown in FIG. In FIG. 2, range A is the voltage corresponding to the kickback pulse, and range B is the voltage corresponding to the back electromotive force. Furthermore, in FIG. 2, the first and second pulse trains indicated by A and B have sufficiently long pulse widths compared to the ranges A and B, so some of them are omitted for illustration purposes. The signals shown in FIG .
A signal as shown in FIG. 2 (G) is generated at the output terminal of.
Since the output signal of the AND gate 16 is applied to the base of the inverting transistor 17,
An inverted signal of the signal shown in FIG. 2G is generated at the collector of the inversion transistor 17.
The capacitor 18 is discharged when the collector of the inverting transistor 17 becomes "L", and is charged via the charging resistor 19 by the power supply voltage (+V _CC2 ) when the collector becomes "H". In that case, the charging time constant is determined according to the values of the capacitor 18 and the charging resistor 19, and the discharging time is determined according to the pulse width of the output signal of the AND gate 16. Therefore, the terminal voltage of the capacitor 18 becomes as shown in FIG. The output pulse of the AND gate 16 is generated at each falling edge of the first and second pulse trains, and each time the output pulse is generated by the capacitor 18.
Since the discharge occurs, the terminal voltage of the capacitor 18 does not exceed a predetermined level. The terminal voltage of the capacitor 18 is applied to the stop circuit 2.
Applied to 0. The stop circuit 20 includes a resistor 21
The terminal voltage of the capacitor 18 is compared with the reference voltage Vref created by As long as the pulse signal continues to be generated, the stop signal will not be generated. When a motor lock or the like occurs and pulses are no longer generated from the Hall IC 3, the output signal of the differential amplifier circuit 5 does not change, and one output remains "H" and the other output remains "L". Then, the output circuit on the "H" side continues to operate, and current continues to flow through the corresponding drive coil, creating a risk of destruction. When the output signal of the differential amplifier circuit 5 stops changing, the output pulse of the AND gate 16 also stops being generated, so that the capacitor 18 is not discharged and its terminal voltage increases. When the terminal voltage exceeds the reference voltage Vref, the stop circuit 20
Since a stop signal is generated from and applied to the waveform shaping circuit 4, both outputs of the differential amplifier circuit 5 become "L" in response, and destruction protection is achieved.
Note that the stop signal from the stop circuit 20 may be applied to, for example, the constant current source 23 of the differential amplifier circuit 5 so that the power supply to the first and second drive coils 1 and 2 is stopped at the same time. (G) Effects of the Invention As described above, according to the present invention, the fall delay of the first and second pulse trains is measured by feeding back the kickback pulse using a Zener diode, which is difficult to integrate into an IC. Motor rotation can be detected without using a capacitor. Also,
According to the present invention, rotation is detected by connecting an AND gate to the input terminal of the output circuit, so the entire detection circuit can be operated with a low power supply voltage, and it is possible to use elements with low breakdown voltage. This has the advantage of being possible. Furthermore, since the capacitor can be discharged for a period approximately equal to the width of the kickback pulse, a capacitor with a large capacity can be used, and the value of the charging resistor can be made small. By the way, if you follow the example, it will be 200 ~
A discharge time of 300 μs can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIGS. 2A to 2H are characteristic diagrams showing waveforms at various parts in FIG. Explanation of main drawing numbers, 1...first drive coil, 2...
...Second drive coil, 5 ...Differential amplifier circuit, 8 ...
First output circuit, 11 ...Second output circuit, 14...
First Zener diode, 15... Second Zener diode, 16... AND gate, 18... Capacitor, 20... Stop circuit.

Claims (1)

[Claims] 1 first and second drive coils, a position detection means for detecting the position of a rotor driven by the drive coil, and first and second pulse trains having opposite phases to each other according to an output signal of the position detection means. a first output circuit that supplies an operating current to the first drive coil in accordance with the first pulse train; and a first output circuit that supplies an operating current to the second drive coil in response to the second pulse train. and a Zener diode inserted between the input and output of the first and second output circuits, and an AND that takes signals obtained at the input terminals of the first and second output circuits. A gate, a capacitor whose charging and discharging are controlled according to an output signal of the AND gate, and a stop means that stops power supply to the first and second drive coils according to a terminal voltage of the capacitor, and a motor lock is provided. A motor protection device characterized in that the motor is protected by actuating the stopping means when the motor stops.