JPH0997675A - Magnetron driving and controlling circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely use a magnetron by suppressing a rush current since even when a triac is turned off by opening a door to turn off a door switch in order to stop the operation of the magnetron, next when the triac is turned on, the polarity of a commercial power source becomes reverse to that when the triac is turned off. SOLUTION: When a door is opened, a malfunction preventive circuit 12 receives the OFF signal of a door switch 9, and a relay driving power source 11 is cut off, thereby turning off a relay driving circuit 6. A latch circuit 13 does not turn off the relay driving circuit 6 immediately when the door switch 9 is turned off and the off signal of the door switch 9 is not inputted to the malfunction preventive circuit 12 so as to wait until a triac 5 is turned off by a microcomputer 10. Next, when the triac 5 is turned on, the microcomputer 10 ascertains the polarity of a commercial power source and when the triac 5 is turned off, the polarity is inverted, thereby controlling a rush current into the triac 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron drive control circuit for a microwave oven, which suppresses a rush current flowing when a step-up transformer is ON and prevents malfunction.

[0002]

2. Description of the Related Art In a conventional magnetron drive control circuit for a microwave oven, a door is opened and a door switch is turned off.
Then, before the microcomputer outputs an OFF signal to the drive circuit, the circuit (hardware) instantly turns off the relay drive circuit to stop the relay (for example, Japanese Patent Laid-Open No. 59-12592).

[0003]

However, in the configuration described above, the microcomputer controls ON / OFF of the triac so as to suppress the inrush current flowing in the load when the triac is turned on. Nevertheless, when the door switch is turned off, this control cannot be performed, and the commercial power supply may have the same polarity when it is turned off and when it is turned on again. In that case, the inrush current becomes large. If I make a mistake, there was a risk that the TRIAC would break down.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and includes a magnetron, a high-voltage unit and a step-up transformer for driving the magnetron, and a relay for driving the magnetron. And triac are connected in series to the step-up transformer, and relay drive circuits and triac drive circuits connected to these relays and triacs respectively, and commercial power supply to suppress the inrush current flowing to each of these drive circuits when the triac is turned on. Checking the polarity, a microcomputer that outputs a drive signal so that the polarity is different when the triac is on and when it is off, a key input circuit that inputs the key pressed by the user to this microcomputer, and the opening and closing of the door And the door switch that inputs A malfunction prevention circuit that connects to the relay drive power supply so that the relay drive circuit operates only when the door is pressed and turns on the relay, and stops the relay drive circuit when the door switch turns off. , When the door switch is turned off, the relay drive circuit is not turned off immediately, and the microcomputer that controls so that the inrush current does not flow controls the door switch input so that it waits until the triac is turned off. A magnetron drive control circuit is configured with a latch circuit that outputs a signal to the prevention circuit.

[0005]

[Function] The microcomputer controls so that the polarities of the commercial power supply are reversed when the triac is turned on and off,
The malfunction prevention circuit operates so as to stop the relay drive circuit when the door switch is turned off, and the latch circuit does not immediately turn off the relay drive circuit when the door switch is turned off, and no inrush current flows. By controlling the input of the door switch so that it waits until the triac is turned off by the microcomputer that controls in this way, the door is opened by outputting a signal to the malfunction prevention circuit, and the triac is set to stop the magnetron when the door switch is turned off. Even when it is turned off, the polarity of the commercial power source is opposite to that when it is turned off when the triac is turned on next time, thereby suppressing the inrush current.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, 1 is a magnetron,
2 is a high voltage unit, and 3 is a step-up transformer. 4 turns ON / O the step-up transformer 3 that drives this magnetron 1.
Reference numeral 5 is a relay that is turned on / off to perform FF, and 5 is a triac connected in series to the relay 4. 6 is a relay drive circuit for driving this relay 4,
Reference numeral 7 is a triac drive circuit for driving the triac 5. Reference numeral 8 is a key input circuit for selecting a cooking method and setting a heating time, and 9 is a door switch.

When the user presses the start key from the key input circuit 8 while recognizing the output of the key input circuit 8 pressed by the user and confirming the state of the door switch 9, the current flows to the triac 5. In order to suppress the inrush current, the relay drive circuit 6 is used when driving the magnetron 1.
And outputs an ON signal to the triac drive circuit 7,
Check the polarity of the commercial power supply when it is OFF as shown in
It is a microcomputer that controls to turn off the triac 5 with a polarity opposite to that of time.

Reference numeral 11 is a relay driving power source necessary for driving the relay 4, and reference numeral 12 is a relay driving circuit 6 when the door switch 9 is ON and the start key is pressed. It is a malfunction prevention circuit that connects the power supply 11 for power supply, turns on the relay 4, and turns off the relay drive power supply 11 when the door switch 9 is turned off to turn off the relay drive circuit 6.

The microcomputer 10 determines the OFF signal of the door switch 9 input to the malfunction prevention circuit 12 by the microcomputer 10 to determine the OFF state of the door switch 9, and the aforementioned OFF control for suppressing the inrush current ends. Is not output until the OFF signal processing ends and the door O
The latch circuit outputs the FF signal to the malfunction prevention circuit 12.

The present invention is configured as described above, and its operation will be described below.

When the door is closed and the start key is input, the microcomputer 10 and the malfunction prevention circuit 12 receive the ON signal of the door switch 9 and the output of the key input circuit 8, and the relay drive circuit 6 is connected to the relay drive power source 11. The relay 4 is driven, the triac 5 is driven by the triac drive circuit 7, the step-up transformer 3 is turned on / off, and the magnetron 1 is driven.

When the door is opened, the malfunction prevention circuit 12 receives the OFF signal of the door switch 9 and tries to turn off the relay drive circuit 6 by cutting off the relay drive power supply 11. However, the latch circuit 13 causes the door switch 9 to operate. When turned off, the relay drive circuit 6 is not turned off immediately, but the triac 5 is turned off by the microcomputer 10.
Do not input the OFF signal of the door switch 9 to the malfunction prevention circuit so that it waits until the next time, and then turn on the triac 5
At this time, the microcomputer 10 checks the polarity of the commercial power supply and reverses the polarity when the triac 5 is off, thereby controlling the inrush current to the triac 5.

[0014]

EFFECT OF THE INVENTION A microcomputer controls a commercial power supply so that the polarities of the commercial power supply are reversed when the triac is turned on and off. When the door switch is turned off, the relay drive circuit is stopped. Do not wait for the malfunction prevention circuit and the microcomputer to control the rush current to flow without turning off the relay drive circuit immediately when the door switch is turned off. By configuring the magnetron drive control circuit with the latch circuit that controls the input of the switch and outputs the signal to the malfunction prevention circuit,
Even if the door opens and the triac is turned off to stop the magnetron by turning off the door switch,
Next time the triac turns on, the polarity of the commercial power supply will be O
By reversing the time of FF, inrush current can be suppressed and it can be used safely without reaching the triac failure mode.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a magnetron drive control circuit according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a commercial power supply voltage and a load current according to an embodiment of the present invention.

[Explanation of symbols]

 1 Magnetron 2 High-voltage unit 3 Boost transformer 4 Relay 5 Triac 6 Relay drive circuit 7 Triac drive circuit 8 Key input circuit 9 Door switch 10 Microcomputer 11 Relay drive power supply 12 Malfunction prevention circuit 13 Latch circuit

Claims (1)

[Claims] 1. A magnetron (1), a high voltage unit (2) and a step-up transformer (3) for driving the magnetron (1), a relay (4) and a triac (for driving the magnetron (1). 5) a relay drive circuit (6) or a triac drive circuit (7) connected in series to the step-up transformer (3) and connected to the relay (4) and the triac (5), and a triac for each drive circuit. In order to suppress the inrush current that flows when (5) is turned on, the polarity of the commercial power supply is checked to determine the triac (5).
A microcomputer (10) for outputting a drive signal so that the polarities are different between ON and OFF, and a key input circuit (8) for inputting a key pressed by a user to the microcomputer (10). , A door switch (9) for inputting the opening and closing of the door, and a relay so that the relay drive circuit (6) operates only when the door switch (9) is ON and the start is pressed from the key input circuit (8). Malfunction preventing circuit (12) which operates to connect the drive power source (11) to turn on the relay (4) and to stop the relay drive circuit (6) when the door switch (9) is turned off. When the door switch (9) is turned off, the relay drive circuit (6) is not turned off, and the microcomputer (1) is controlled so that the inrush current does not flow.
The latch circuit (13) controls the input of the door switch (9) so as to wait until the triac (5) is turned off by 0) and outputs a signal to the malfunction prevention circuit (12). Magnetron drive control circuit.