KR940007637B1 - Microcomputer safety apparatus of microwave oven - Google Patents

Abstract

The safety apparatus detects clocks generated according to operation of micom and controls high frequency output according to detected clock signal. The apparatus includes a run-out detector (14) for discriminating abnormal operation of a microcomputer and an output on/off controller (15) for stopping operation of a switching power supply (9) according to control signal sent from the run-out detector. The run-out detector (14) includes a differentiator (14A) for differentiating clock signal, a limiter (14B) for limitng level of differentiated clock signal, an integrator (14C) for integrating output signal of the limiter (14B), and an inverter (14D) for generating high or low signal according to output signal of the integrator.

Description

Microcomputer runaway safety device

1 is a circuit diagram of a conventional microwave oven.

2 is a microwave circuit diagram of the present invention.

3 is a signal waveform diagram in normal operation in the present invention.

4 is a signal waveform diagram of abnormal operation in the present invention.

* Explanation of symbols for main parts of the drawings

4: microcomputer 9: switching power supply

14: runaway monitoring means 15: output cutoff control means

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device for a microwave oven, and in particular, detects a clock change that the control microcomputer outputs according to normal operation, and controls the high frequency output on / off based on the detection result, thereby damaging the equipment by the congestion of the microcomputer. It relates to a microwave oven to prevent the.

Referring to FIG. 1, a conventional microwave oven includes a bridge diode 1 for rectifying an input AC power supply, a normal input power supply 2 for supplying a DC power supply, and a reset circuit part for microcomputer reset control. (3), a microcomputer 4 for performing high frequency heating control suitable for cooking setting and set cooking, an output setting unit 5 for setting high frequency output under microcomputer control, and according to all detection signals and setting output signals. A high frequency output control unit 6 for controlling the high frequency output, a rectifying unit 7 for rectifying the input AC power supply for the high frequency output power supply, and a high frequency output unit for generating high frequency oscillation and output through switching operation of the rectified power source ( 8), a switching power supply unit 9 for switching the driving power of the high frequency output unit 8 under the control of the high frequency output control unit 6, and a synchronous circuit for supplying the high frequency output control timing information to the output control unit 6; 10, high spirits To the voltage detector 11 for detecting the output voltage and supplying it to the output controller 6, and the overcurrent detector 12 and the average current detector 13 for detecting the overcurrent and high frequency output current levels and supplying them to the output controller 6 7A is a bridge diode, 9A is a power transistor driving circuit, L0 to L5 is a coil, C1 to C3 is a capacitor, D1 to D3 is a diode, Q1 and Q2 are transistors, T1 is a high voltage transformer, PT is a pulse transformer, RO Is resistance, MGT is magnetron.

The high frequency cooking operation by this is as follows.

When the user selects a dish through the key operation, the high frequency output is set to the output setting unit 5 based on the result of the decoding by the microcomputer 4, and the high frequency output control unit 6 supplies the power switching signal based on the set output information. The switching signal controls switching of the transistor Q2 to switch the power supply transistor Q1 in the driving circuit 9A in accordance with the pulse signal induced on the secondary side of the pulse transformer PT. By the switching operation, the output power of the rectifier 7, that is, the primary side power supply of the high voltage transformer T1 is interrupted, and accordingly, the high voltage pulse induced on the secondary side is applied to the magnetron MTG to perform cooking by high frequency oscillation. .

On the other hand, the signal induced in the secondary detection coil L3 of the high voltage transformer T1 detects a zero cross in the synchronization circuit 10 and supplies it to the high frequency output control unit 6 to accurately control the high frequency output timing. In addition, the organic signal of the detection coil L3 is used as output level control information by detecting the voltage level in the voltage detector 11 and supplying it to the high frequency output control unit 6, and is induced in the detection coil L5. The signal is detected by the overcurrent detector 12 and the average current detector 13, and the current level is detected and supplied to the high frequency output controller 6 to be used as output current control information.

However, according to the conventional microwave oven operated as described above, since there is no means for coping with the microcomputer 4 malfunctioning due to external noise or internal circuit abnormality and congestion, in this case, circuit damage as well as cooking failure due to excessive high frequency output. There is a problem that causes safety accidents such as and fire.

The present invention monitors the state of the clock output by itself in accordance with the normal operation of the microcomputer to detect whether there is an abnormality, and in case of abnormal operation of the detection result, the high frequency output (high frequency oscillation power supply by power switching) is automatically shut off. The purpose of the present invention is to protect the circuit elements and to ensure safety and reliability in the use of a microwave oven, and to configure the microwave oven according to the present invention and cooking control and safety control operations according to the present invention with reference to the accompanying drawings. The explanation is as follows.

First, referring to FIG. 2, the microwave oven according to the present invention includes a bridge diode 1 for rectifying an input AC power supply, a DC input power supply 2 for supplying DC power, and a microcomputer reset control. A reset circuit section 3, a microcomputer 4 for performing high frequency heating control suitable for cooking setting and set cooking, an output setting section 5 for setting high frequency output under microcomputer control, various detection signals and setting outputs A high frequency output control unit 6 for controlling a high frequency output in accordance with a signal, a rectifier 7 for rectifying an input AC power supply for high frequency output power, and oscillating and outputting a high frequency through a switching operation of the rectified power. The high frequency output section 8, the switching power supply section 9 for switching the driving power of the high frequency output section 8 under the control of the high frequency output control section 6, and the high frequency output control timing information to the output control section 6; Motivation to supply A furnace 10, a voltage detector 11 for detecting a high frequency output voltage and supplying it to the output controller 6, an overcurrent detector 12 for detecting an overcurrent and a high frequency output current level and supplying it to the output controller 6; An average current detection unit 13, a congestion monitoring means 14 for monitoring the clock output from the microcomputer 4 to detect and determine whether abnormal operation of the microcomputer, and the abnormal operation results of the monitoring results of the congestion monitoring means 14 It is composed of an output cutoff control means 15 which stops the operation of the switching power supply unit 9 in response to a control signal output at the time and turns off the high frequency oscillation output.

The detection of abnormal operation by the apparatus of the present invention configured as described above and the blocking control operation of the high frequency output will be described with reference to FIGS. 2 to 4.

First, referring to the cooking control operation by the microwave oven in FIG. 2, when the user selects a dish through the key operation, the high frequency output is set in the output setting unit 5 based on the result of the decoding by the microcomputer 4, The high frequency output control unit 6 outputs a power switching signal in accordance with the set output information. The switching signal controls the transistor Q2 to switch the driving circuit 9A according to the pulse signal induced on the secondary side of the pulse transformer PT. The power supply transistor Q1 is switched on, and the output power of the rectifying unit 7, that is, the primary power supply of the high voltage transformer T1 is interrupted by the switching operation of the power supply transistor Q1, and accordingly, the high voltage pulse induced in the secondary side is interrupted. Is applied to the magnetron (MGT) to proceed cooking by high frequency oscillation.

On the other hand, the signal induced in the secondary detection coil L3 of the high voltage transformer T1 detects a zero cross in the synchronization circuit 10 and supplies it to the high frequency output control unit 6 to accurately control the high frequency output timing. In addition, the organic signal of the detection coil L3 is used as output level control information by detecting the voltage level in the voltage detector 11 and supplying it to the high frequency output control unit 6, and is induced in the detection coil L5. The signal is detected by the overcurrent detector 12 and the average current detector 13, and the current level is detected and supplied to the high frequency output controller 6 to be used as output current control information.

This series of cooking control operations is based on the premise when the microcomputer 4 operates normally, that is, when the transistor Q5 is turned on in the output cutoff control means 15.

That is, when the microcomputer 4 normally performs cooking control and cooking proceeds, a regular clock pulse of a predetermined cycle is outputted by the output terminal PORT1 as shown in a of FIG. 3, and this output pulse is a capacitor C4. And the derivative circuit 14A of the resistor R1 are differentiated and output in the waveform shown in b of FIG.

Since the differential signal is applied to the cathode of the diode D4 through the resistor R2, it is clipped to a predetermined level as shown in c of FIG. 3 according to the operation of the limiter 14B and then applied to the base of the transistor Q3.

Accordingly, the transistor Q3 is turned on and off, and at its collector stage, the integrated signal shown in d of FIG. 3 is output by charging and discharging of the capacitor C5.

That is, the integration operation by the capacitor C5 is performed together with the switching by the resistors R3, R4, R6 and the transistor Q3, and the transistor Q4 is output by the output of the integration circuit 14C. The high level signal shown in e of FIG. 3 is applied to the base of the voltage of the transistor C5 by selecting the capacitance value of the capacitor C5 and performing the integrated level at a level at which the transistor Q4 can be turned on. Turn on Q4).

Therefore, the high signal is output from the collector terminal of transistor Q4 as in f of FIG.

That is, resistors R5, R7 and transistors Q4 are operated as level detection and inverter 14D.

On the other hand, the high signal output from the collector of the transistor Q4 is applied to the base of the transistor Q5 of the output cutoff control means 15, thereby turning on the transistor Q5 (see g in FIG. 3). Q5) is turned on and its collector potential becomes low as shown in h of FIG. 3 so that the transistor Q2 can be switched according to the switching pulse of the high frequency output controller 6, that is, the normal cooking control state as described above. do.

In the output cutoff control means 15, the resistors R8 and R9 are for bias.

In other cases, when the microcomputer 4 moves due to a circuit abnormality or external noise, the output terminal PORT1 outputs a signal maintained in a high or low state as shown in a of FIG.

That is, the clock pulses in the normal operation are not output.

Therefore, in this case, since the output of the differential circuit 14A becomes 0 volts (low) as shown in b of FIG. 4, the output of the inverter 14B also becomes low, and the transistor Q3 of the integrating circuit 14C is turned off. As shown in d and e of Fig., The high signal is inverted in the level detection and inverter 14D and applied to the output interruption control means 15 as a low signal. (See f in Figure 4)

The transistor Q5 is turned off by the applied low signal (see g and h in FIG. 4) and the transistor Q2 is not operated.

Therefore, during the abnormal operation, the operation of the switching power supply unit 9 is stopped, and the operation of the high frequency output unit 8 is also stopped to prevent damage to circuit elements due to high voltage abnormality, cooking failure due to overheating, fire occurrence, etc. It is possible to secure reliability in the operation of the device.

As described above, according to the present invention, it is possible to cope with abnormal operation of the microwave oven, to improve safety and reliability, to prevent damage to circuit elements, and to prolong the life of the device.

Claims (2)

Congestion monitoring means 14 for monitoring and detecting the clock output from the microcomputer 4 in accordance with the normal or abnormal operation of the microcomputer 4 to perform cooking control of the microwave oven, and the runaway Microcomputer runaway of the microwave oven composed of output blocking control means 15 which stops the operation of the switching power supply unit 9 in response to a control signal output during the abnormal operation of the monitoring result of the monitoring means 14 to turn off the high frequency oscillation output. safety device. 2. The runaway monitoring unit (14) according to claim 1, wherein the runaway monitoring unit (14) includes a differential circuit (14A) for differentiating a clock, a limiter (14B) for limiting the level of the differential signal, an integrating circuit (14C) for integrating the level limited signal, And a microcomputer congestion safety device of a microwave oven comprising a level detection and an inverter 14D for supplying an inverted or non-inverted signal to the output cutoff control means 15 according to the integrated signal level.