JPH0564007B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a DC motor drive power supply device for driving a relatively small DC motor used in rotating equipment and the like.

Conventional configuration and its problems In general, a power supply device that supplies power to a DC motor is required to have safety functions in addition to simply supplying DC power. For example, if a motor locks up due to an abnormal overload, the power may be cut off to prevent the overcurrent from flowing and burning out, or the overcurrent may not be cut off even after a short period of overcurrent during startup. Protection functions are required. In addition, if the motor circuit is shot, the power must be cut off immediately. Furthermore, if the power supply voltage itself decreases, the rotation of the motor becomes unstable. Therefore, it is desirable to shut it off in this case as well. Furthermore, it is necessary to supply a constant voltage to stabilize the rotation of the DC motor.

In conventional motor power supply circuits, each function is provided separately, resulting in a large-scale device, which has the problems of increasing the number of parts and increasing costs.

OBJECT OF THE INVENTION The present invention aims to eliminate the drawbacks of the above-mentioned conventional examples, and aims to provide motor power supply, motor lock protection,
The purpose is to achieve functions such as protection in case of load abnormality and continuous operation during protection operation with a simple circuit.

Structure of the Invention In order to achieve the above object, the present invention includes a constant voltage circuit that controls DC voltage to a constant voltage, and an overcurrent detection circuit that detects a current above a certain level between the constant voltage circuit and a motor load. , an integrating circuit that increases the voltage over time when the overcurrent detection circuit detects an overcurrent, a voltage drop detection circuit that detects a drop in constant voltage, an output voltage of the integration circuit, and an output voltage of the voltage drop detection circuit. a comparison circuit that compares the
This comparator circuit includes a cutoff circuit that cuts off the output of the constant voltage circuit when it detects that the output voltage of the integration circuit is higher than the output voltage of the voltage drop detection circuit.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram in one embodiment of the present invention. In the figure, 1 is a constant voltage circuit, which is composed of a bridge diode 2 that converts AC voltage to DC, a Zener diode 3 that generates a reference voltage, transistors 4 and 5 that maintain a constant DC voltage, etc. There is. A voltage drop detection circuit 6 detects a voltage drop due to a short circuit in a motor load, etc., and is comprised of a Zener diode 7, voltage dividing resistors 8 and 9, and the like. 10 is an overcurrent detection circuit, which includes a resistor 11 for converting overcurrent into voltage, and transistors 12, 13, and 1 that operate when a current exceeding a certain current flows.
4, a resistor 15, etc. Reference numeral 16 denotes an integrating circuit, which is composed of a resistor 17, a capacitor 18, and the like. 19 is a comparison circuit, which is composed of a comparator IC. Reference numeral 21 denotes a cutoff circuit, which cuts off the output of the constant voltage circuit 1 according to a signal from the comparison circuit 19, and includes transistors 22,
It consists of a capacitor 23, etc.

FIG. 2 is a diagram showing electrical signals of each part.

Next, the operation of the above embodiment will be explained. In FIG. 1, in the constant voltage circuit 1, the transistor 4
A voltage corresponding to the output voltage a is applied to the base of
A reference voltage from a Zener diode 3 is applied to the emitter, and the transistor 5 is controlled according to the base voltage to generate a constant DC voltage as the output voltage a. This DC voltage is reduced to a low voltage by a Zener diode 7 whose voltage is lower than the voltage of the output voltage a in a voltage drop detection circuit 6, and a voltage dividing resistor 8,
9, the voltage is lowered further and outputted to point C. In this voltage drop detection circuit, when the output voltage a becomes below a certain level, the output point C also becomes a low voltage in accordance with the output voltage a. In the overcurrent detection circuit 10, a voltage is generated in the resistor 11 according to the output voltage I of the constant voltage circuit 1, and when this voltage exceeds a certain level, the transistor 12 is turned on, the transistor 13 is turned on, and the transistor 14 is turned off. The transistor 14
When turned OFF, the next integrating circuit 16 is operated.
The integrating circuit 16 has a time constant of a resistor 17 and a capacitor 18, and the voltage at the output point b increases. When the transistor 14 is on, the voltage at the output point b is equal to the resistor 17,
A voltage divided by 15 is generated. The comparator circuit 19 compares the voltage at the output point c of the voltage drop detection circuit and the output point b of the integrating circuit 16, and when the voltage at the output point b of the integrating circuit 16 increases, the comparator
The output of IC20 becomes H level. Breaking circuit 21
The transistor 22 is turned on by the H level signal from the comparison circuit 19. As a result, the cutoff circuit 2
The voltage at point d of output 1 becomes L level, transistor 5 is turned off, and output voltage a is cut off.
Once it is cut off, the voltage at the output point c of the voltage drop detection circuit goes to L level, so it is intermittently cut off. To reset the cut-off state, turn off the power once. In other words, when the power is turned on, a charge current flows through the capacitor 23 of the cutoff circuit 21, and the time until the transistor 22 turns on is slower than the rise of the output voltage a, so the cutoff circuit does not operate and returns to normal. be.

Next, the operation under each load condition will be explained with reference to FIG. First, when the motor is started, the motor load current I, which is higher than the current i1 at which the overcurrent detection circuit 10 operates, flows for a time T1, so the overcurrent detection circuit 10 operates, and the voltage at the output point b of the integrating circuit 16 increases. However, before the voltage rises to the output point c of the voltage drop detection circuit 6, it falls below the voltage i1 at which the overcurrent detection circuit 10 operates. Therefore, because the cutoff circuit 21 does not operate due to the short-time overcurrent of T1, the output voltage a is not cut off.

Next, when the motor is locked, the motor load current I, which is higher than the current i1 at which the overcurrent detection circuit 10 operates, flows for a long period of time T2, so the overcurrent detection circuit 10 operates, and the voltage at the output point b of the integrating circuit 16 flows. increases to the voltage at the output point c of the voltage drop detection circuit 6, and the output point d of the cutoff circuit 21 becomes L level. Therefore, this L level output causes transistor 5 to
Since it is turned OFF, the output voltage a is cut off. The blocked state can be returned to normal by resetting it once.

In addition, when a motor load or the like is short-circuited, the voltage at the output point c of the voltage drop detection circuit 6 becomes lower than the voltage at the output point b of the integrating circuit 16 for a very short time T3, and the voltage at the output point d of the cutoff circuit 21 becomes lower. becomes L level. Therefore, the output voltage a is cut off in the same manner as described above.

Further, when the AC input power supply voltage itself decreases and the constant voltage circuit 1 cannot secure the specified voltage, the output voltage a decreases. Therefore, the voltage at the output point c of the voltage drop detection circuit 6 is the output b of the integrating circuit 16.
Since the voltage is lower than the voltage at the point, the output voltage a is cut off as described above.

Effects of the Invention As is clear from the above description, the present invention combines a constant voltage circuit, a voltage drop detection circuit, an overcurrent detection circuit, an integration circuit, a comparison circuit, and a cutoff circuit, so that the motor can be prevented from abnormal overload. Therefore, if the motor is locked, the power is cut off reliably, and even a short overcurrent at startup will not cut off the power, and if the motor circuit is short-circuited, the power will be cut off immediately. Furthermore, since a constant voltage is supplied to the DC motor, stable rotation can be obtained. Furthermore, even if the input power supply voltage of this device itself drops, the power supply to the DC motor is cut off, so it is possible to prevent the danger of the DC motor becoming unstable in rotation or locking up due to the voltage drop. Moreover, it has a simple configuration, can be expected to provide reliable operation with an extremely low failure rate, is inexpensive to manufacture, and can be used by operators with peace of mind.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a power supply device according to the present invention, and FIG. 2 is a signal waveform diagram of each part. 1... Constant voltage circuit, 6... Voltage drop detection circuit,
10...Overcurrent detection circuit, 16...Integrator circuit, 1
9... Comparison circuit, 21... Breaking circuit.

Claims (1)

[Claims] 1 Constant voltage circuit 1 that controls DC voltage to a constant voltage
an overcurrent detection circuit 10 that detects a current above a certain level between the constant voltage circuit 1 and the motor load; an integration circuit 16 that increases the voltage over time when the overcurrent detection circuit 10 detects an overcurrent; A voltage drop detection circuit 6 that detects a drop in constant voltage, a comparison circuit 19 that compares the output voltage of the integrating circuit 6 and the output voltage of the voltage drop detection circuit 6, and this comparison circuit 19 is the voltage drop detection circuit 6. A power supply device for driving a DC motor, comprising a cutoff circuit 21 that cuts off the output of the constant voltage circuit 1 by detecting that the output voltage of the integration circuit 6 is higher than the output voltage of the constant voltage circuit 1.