JPH05208099A - Protecting device for control circuit - Google Patents

Abstract

PURPOSE:To realize a protecting device for a control circuit which possesses the superior reliability with the less number of parts at a low cost by preventing the imperfect operation due to the continuous electric conduction of a heater or a motor due to the trouble or the erroneous operation of a microcomputer, in a control circuit using the microcomputer for a clothes dryer and washing machine. CONSTITUTION:A protecting device for a control circuit is constituted of a motor 4 connected with an ac power source 1, load such as a heater 5, switching means 3 for controlling the load, microcomputer 6, system clock oscillation circuit 7, driving circuit 8 which is connected with the microcomputer 6 and controls the switching means 3, and an output prohibiting circuit 9 connected in series with the driving circuit 8. When a timer circuit built in the microcomputer 6 and counting the system clock overflows, the output prohibiting circuit 9 is turned OFF, and the switching means 3 is turned OFF, and the continuous electric conduction of the load is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit protection device for household clothes dryers and washing machines.

[0002]

2. Description of the Related Art In recent years, the control circuit of a household clothes dryer or a washing machine can be controlled optimally by electronic control equipped with a sensor and a microcomputer.
However, when the microcomputer fails or malfunctions, the heater and the motor are continuously energized, which may cause a safety problem such as a fire.

As a conventional countermeasure against a malfunction or malfunction of a microcomputer, a method of providing a protection device outside the microcomputer is generally used, and FIG. 5 shows a conventional embodiment.

Briefly explaining the conventional example of FIG. 5, (a)
Is a protection circuit, and (b) is a periodic signal Vc from the microcomputer added to the protection circuit. (C) is the output inhibit signal Vd of the protection circuit. 12 is a diode,
Reference numeral 13 denotes a resistor, which applies the signal Vc to the signal conversion circuit 14.
The signal conversion circuit 14 allows only the AC component to pass through the capacitor 141, converts the AC to DC, and converts the AC component into DC.
4 generates a signal of Vd. If the microcomputer malfunctions and the periodic signal such as Vc disappears,
The DC signal Vd becomes almost zero, and the transistor 151 of the prohibiting circuit 15 is turned off, so that the heater and the motor are turned off to ensure safety.

[0005]

However, the conventional protection circuit has a drawback that the number of parts is large and the cost is high. In addition, a signal with a long cycle may be output depending on the type of malfunction of the microcomputer, and the output signal of the signal conversion circuit may be slightly output and the protection circuit may not operate.

In view of the above problems, it is an object of the present invention to reduce the number of parts and increase the accuracy of erroneous operation determination.

[0007]

To achieve this object, the present invention provides a load such as a heater and a motor connected to an AC power source, a switching means for controlling the load, and a micro controller for controlling the switching means. A computer,
The system clock oscillation circuit of the microcomputer, a drive circuit connected to the output terminal of the microcomputer to drive the switching means, and an output prohibition circuit connected in series with the drive circuit, the system of the microcomputer A program controllable timer circuit for counting a clock is built in the microcomputer, an output signal thereof is added to the output prohibiting circuit, and a control device for controlling the switching means by the output signal of the timer circuit is constituted.

[0008]

With this configuration, when the microcomputer is normal, the timer circuit is periodically reset so as not to overflow, and in the case of a failure or malfunction, the periodic reset cannot be performed, so that the timer circuit overflows. Since the output prohibiting circuit performs the prohibiting operation, the drive circuit of the switching means does not operate and the continuous energization of the heater and the motor load can be reliably prevented. In addition, because the timer circuit for protection is built in the inside of the microcomputer,
It is possible to realize an inexpensive and highly reliable control circuit protection device for a clothes dryer, a washing machine or the like, which has a small number of parts.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a control device for a clothes dryer according to the present invention. Reference numeral 1 is an AC power supply, 2 is a power switch, and 3 is a switching means such as a thyristor or a relay, which controls loads such as a motor 4, a heater 5a, and a heater 5b connected to the AC power supply 1. Reference numeral 6 denotes a microcomputer, which controls the drying operation by a key switch signal or a sensor signal on the operation display panel. Reference numeral 7 is a system clock oscillation circuit of the microcomputer 6. Reference numeral 8 denotes a drive circuit for the switching means 3, which is on / off controlled by the microcomputer 6. An output prohibiting circuit 9 is connected in series with the driving circuit 8 and can control the opening operation of the switching means 3 regardless of the operating state of the driving circuit 8. In FIG. 1, peripheral circuits such as a DC power supply of the microcomputer 6 are omitted.

FIG. 2 shows an embodiment of a washing machine controller according to the present invention. 10a is a water supply valve and 10b is a drain valve. 4'is a washing motor, and 11 is a phase advancing capacitor of the washing motor 4 '. Drive circuit 8 by output prohibition circuit 9
Can control the opening of the switching means 3 regardless of the operation of
When the microcomputer 6 malfunctions, the output prohibiting circuit 9 is turned off, and a failure such as continuous dehydration energization can be prevented.

FIG. 3 shows an embodiment of a timer circuit built in the microcomputer 6 according to the present invention. Programmable frequency divider 6 from system clock oscillator 7
Input a signal to 0. The programmable frequency dividing circuit 60 can control the frequency dividing ratio by the program signal and the data buffer 61. The frequency-divided output signal is applied to the NOR gate 62 via the inverter 62, and the output signal is input to the frequency dividing circuit 64. The frequency dividing circuit 64 can be cleared by a program signal from the microcomputer 3. The overflow signal of the frequency dividing circuit 64 is returned to the input of the NOR gate 63, and the count is stopped by the overflow signal. The output signal of the frequency dividing circuit 64 is also applied to the NOR gate 65, and the output signal Vt of the NOR gate 65 is applied to the drive circuit 9. A system reset signal is applied to one input of the NOR gate 65. When the system reset signal is L and the frequency divider circuit output signal is L, the signal Vt of the NOR gate 65 becomes H and the drive circuit 9 becomes operable. The frequency divider 64 overflows and H
Then, Vt becomes L, the drive circuit 9 does not operate, the switching means 3 does not operate, and the load is turned off.

FIG. 4 is a flow chart of one embodiment of the protection device according to the present invention. A program start 600 is the same as the reset release. An initial setting routine 601 can set the frequency dividing ratio of the programmable frequency dividing circuit 60 of FIG. 3 and can set the overflow time of the frequency dividing circuit 64. 602 is a counter clear process for resetting the frequency dividing circuit 64. A main routine 603 is an operation control processing program for the dryer or the washing machine, which periodically clears the frequency dividing circuit 64 so as to pass through a counter clear process after or during the process. When the microcomputer 6 malfunctions, periodic resetting becomes impossible, the frequency dividing circuit 64 overflows, the signal Vt to the output prohibiting circuit 9 becomes L, and the switching means 3 is turned off. When the microcomputer 3 operates normally, the frequency dividing circuit 64 is reset periodically, so that it does not overflow and the signal Vt becomes H.

Although the present embodiment has been described with respect to the control circuit of the clothes dryer and the washing machine, it can be applied to, for example, the control circuit of the dishwasher, and the point is that the control circuit is configured to control the load by the microcomputer. It can be used as a protection device.

[0015]

As described above, according to the present invention, a load such as a heater and a motor connected to an AC power source, a switching means for controlling the load, a microcomputer for controlling the switching means, and a microcomputer for controlling the switching means are provided. A system clock oscillator circuit, a drive circuit connected to the output terminal of the microcomputer to drive the switching means, and an output prohibition circuit connected in series with the drive circuit to count the system clock of the microcomputer. The output signal of a programmable timer circuit is added to the output prohibition circuit, and the switching means can be controlled by the overflow signal of the timer circuit, so that the number of parts is small, and the cost is high and the clothes dryer or washing machine is highly reliable. A protection device can be realized. Further, when the microcomputer is reset, the signal to the output prohibition circuit is forcibly set to L, which eliminates the malfunction when the power switch is turned on.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a control circuit for a clothes dryer according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of a control circuit for a washing machine according to the present invention.

FIG. 3 is a block diagram showing an embodiment of a timer circuit with a microcomputer according to the present invention.

FIG. 4 is a flowchart illustrating the operation of the protection device according to the present invention.

5A is a circuit diagram showing a protection device for a conventional control circuit, FIG. 5B is the same input waveform diagram, and FIG. 5C is the same output waveform diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 3 Switching means 4 Motor (load) 5a, 5b Heater (load) 6 Microcomputer 7 System clock oscillation circuit 8 Drive circuit 9 Output prohibition circuit

Front Page Continuation (72) Inventor Yushi Suzuki, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. An AC power supply, a load such as a heater or a motor connected to the AC power supply, a switching means for controlling the load, a microcomputer for controlling the switching means, and a system clock oscillation of the microcomputer. A circuit, a drive circuit connected to the output terminal of the microcomputer to drive the switching means, and an output prohibition circuit connected in series with the drive circuit. Program control for counting the system clock of the microcomputer is possible. A protection device for a control circuit, wherein the output signal of the timer circuit is added to the output prohibition circuit, and the switching means is controlled by the output signal of the timer circuit. 2. A program controllable timer circuit counting a system clock of a microcomputer is applied to the output prohibiting circuit, and the timer circuit counts the output signal of the timer circuit.
The protection device for a control circuit according to claim 1, wherein the output prohibiting means is turned off to control the switching means to be off. 3. A program controllable timer circuit for counting a system clock of a microcomputer is built in the microcomputer, and an output exclusive means of the timer circuit turns off an output prohibiting means to turn off a switching means. The protection device for a control circuit according to claim 1, which is controlled.