JPH0215146Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of the Invention The present invention relates to a control device for a load (such as a motor) applied to equipment such as a vending machine in which a microcomputer is used in the control section.

(b) Background Even after a microcomputer is supplied with a stable power supply voltage (generally 5V) when the power is turned on,
Normal operation will not occur until the internal oscillation is stabilized and set to the initial state. For this reason, a charging circuit has conventionally been connected to the reset terminal of a microcomputer to delay the sudden rise of the power supply voltage when the power is turned on, and to reset the microcomputer until the voltage reaches a threshold. At this time, the time constant of the charging circuit is set so that sufficient time is secured for the microcomputer to shift to a stable state after being supplied with the specified voltage. However, in general, it is uncertain whether a microcomputer outputs a high level "H" or a low level "L" to an I/O port in a reset state.
Or, most of the prescribed ones are designed to output "H". Therefore, even after the reset of the microcomputer is released, the I/O port will go "H" in a very short period of time until the I/O port is set to the initial state according to the program.
will be output. In devices where a DC motor or solenoid is controlled by a microcomputer, the driver IC for the motor, etc. is generally configured with a Darlington transistor array. When "H" is generated from the O port, the driver IC becomes "L", causing these drive devices to malfunction momentarily.

For example, in a vending machine, a microcomputer calculates the amount of money inserted, determines whether a product can be sold, calculates change, etc., and controls a motor or solenoid in accordance with the vending operation. Therefore, if a malfunction like the one described above occurs, the change or goods will be dispensed, or if the motor's stop position moves out of the standby position due to an instantaneous movement, the next time a drive signal is output to the motor, it will not operate and the change or item will be dispensed. This resulted in a situation where the goods were not delivered.

(c) Purpose of the invention Based on the above points, the present invention has two voltage detection circuits, and the lower voltage detection output controls the reset of the microcomputer, and the higher voltage detection output drives a motor or solenoid, etc. By controlling the power supply of the device, the drive device is enabled to operate after the microcomputer is set to its initial state, thereby preventing malfunctions when the power is turned on.

(d) Embodiment of the invention Figure 1 shows a circuit according to the invention, in which the power supply terminal 7
The DC power supplied by the regulator 8 is
It is stabilized at 24V, and further stabilized at 5V by the regulator 9 at the subsequent stage. and regulator 8
The output side of is a self-biased transistor 10
connected to motor 2 and solenoid 3 through
The output side of the regulator 9 is connected to the power supply terminal _VDD of the microcomputer 1. Also,
An integrating circuit 4 consisting of a resistor R ₁ and a capacitor C is connected to the output side of the regulator 8, and the voltage at point A of the integrating circuit 4 is connected to the (+) input terminal of a comparator 5 which is a voltage detection circuit _. , R ₃ and is applied to the (+) of comparator 6.
The voltage at point A is divided by resistors R ₄ and R ₅ and applied to the input terminal. At this time, the resistances R ₂ , R ₃ , R ₄ ,
The value of R ₅ is set so that the potential at point D V _D is greater than the potential at point E _VE . A Zener voltage from a Zener diode 10 is applied to the (-) input terminals of the comparators 5 and 6. Further, the output terminal of the comparator 5 is connected to the reset terminal R of the microcomputer 1, and the output terminal of the comparator 6 is connected to the base of a transistor 11 whose collector is connected to the base of a transistor 10. On the other hand, the I/O boat of the microcomputer 1 is connected to the motor 2 and the solenoid 3 through driver ICs formed by Darlington transistor arrays 12 and 13, respectively.

The operation according to the above configuration will be explained with reference to the waveform diagram in FIG. 2. First, when DC power is supplied to power terminal 7, B
The point potential V _B rises steeply toward 24 V, power is supplied to the comparators 5 and 6, and the Zener voltage V _Z is applied to each (-) input terminal. On the other hand, the potential at point _C also rises sharply toward 5V, and power is also supplied to the microcomputer 1. However, the A point potential V _A gradually increases due to the time constant of the capacitor C and the resistor R ₁ . The potential at point _D and the potential at point _E are also V _A R ₃ /R ₂ respectively.
+R ₃ ·V _A R ₅ /R ₄ It gradually increases toward +R ₅ , but when the D point potential V _D exceeds the Zener voltage V _Z , the comparator 5 generates an “H” output. Therefore, the microcomputer 1 in the reset state
Since "H" is input to the reset terminal R, the reset state is released. After that, the E point potential V _E
exceeds the Zener voltage V _Z , comparator 6
"H" output is generated, and V _CC is applied to the base of transistor 11, which turns it on, so transistor 10 turns on, and motor 2 and solenoid 3
is supplied with a power supply voltage V _S of 24V, and when "H" is output from the I/O port of the microcomputer 1, the motor 2 and solenoid 3 can be driven. However, when the power is turned on, power is supplied to the drive device with a slight delay after the reset of the microcomputer 1 is released, and at this point, the microcomputer 1 is operating normally and the initial setting of each input/output port I/O has been completed. Therefore, momentary malfunctions do not occur.

However, when the supply of DC power to the power supply terminal 7 is stopped, V _B rapidly decreases and the capacitor C
is instantaneously discharged through the diode 14, so that V _A follows V _B and drops rapidly. Therefore, first, V _E becomes less than the value obtained by subtracting the voltage for the hysteresis of comparator 6 from V _Z , and comparator 6 outputs "L", so transistor 1
1 is turned off, transistor 10 is also turned off, and power supply V _S to motor 2 and solenoid 3 is stopped. Next, when V _D becomes less than the value obtained by subtracting the hysteresis voltage of comparator 5 from V _Z and comparator 5 outputs "L", microcomputer 1 enters the reset state. Therefore the power supply
When the power is OFF, the power supply to the drive device has already been stopped before the microcomputer 1 is reset and the output of each I/O port becomes unstable or "H" output. Malfunctions are also prevented.

(e) Effects According to the present invention, when the voltage detection circuit is equipped with two high and low voltage detection circuits and the voltage of the integrating circuit gradually increases when the power is turned on, the reset of the microcomputer is first canceled using the lower voltage detection power. , the I/O of the microcomputer when the power is turned on in order to control the power supply to the drive device using the next higher voltage detection output.
This prevents the drive device from malfunctioning due to an undefined output from the O port. Furthermore, when the power is turned off, the power supply to the drive device is first stopped based on the higher voltage detection output, so malfunction of the drive device when the power is turned off can be prevented.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the control device according to the present invention, and FIG. 2 is a voltage waveform diagram showing the operation. 1...Microcomputer, 2...Motor,
3...Solenoid, 4...Integrator circuit, 5...First
Voltage detection circuit, 6... second voltage detection circuit.

Claims (1)

[Scope of utility model registration request] In equipment that has a microcomputer and a drive device controlled by the microcomputer connected to the same power line, the voltage of the integrating circuit gradually increases when the power is turned on, and the voltage of the integrating circuit rapidly decreases when the power is turned off. a discharge element;
a first voltage detection circuit that holds the microcomputer in a reset state when the voltage of the integration circuit is within a range below a first predetermined level, and releases the reset state when the voltage exceeds the first predetermined level; , a second circuit that allows power to be supplied to the drive device when the voltage of the integrating circuit exceeds a second predetermined level that is higher than the first predetermined level;
A control device consisting of a voltage detection circuit.