KR100265629B1 - Auto zero crossing device of microwave oven and its control method - Google Patents

Abstract

PURPOSE: An auto zero-crossing device of a microwave oven and a control method thereof are provided to automatically amend irregular errors of a relay to carry out precise zero-crossing, thereby protecting inner circuit parts from an inrush current and an overload. CONSTITUTION: An auto zero-crossing device of a microwave oven comprise a key input part(10) manipulated by a user for outputting an operation signal, a relay driving part(40) for turning on/off a relay(RY1), a voltage detection part(30) for detecting a voltage when the relay is turned on, and a microcomputer(20) for determining a voltage level of an input voltage detected by the voltage detection part by comparing the input voltage with a plurality of reference voltages having different levels when the relay is turned on according to the operation signal output from the key input part, computing a relay amendment value for amending a timing that the relay is turned on by a zero-crossing period with relation to the voltage level, and driving the relay driving part according to the relay amendment value.

Description

Auto zero crossing device of microwave oven and its control method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven, and more particularly, to an auto zero crossing apparatus of a microwave oven and a control method thereof, in which a precise zero crossing is automatically performed to block an inrush current of a microwave oven.

In general, microwave ovens supply high-voltage power to the magnetron to emit microwaves, and the microwaves vibrate moisture contained in food. Therefore, the food is cooked by the molecular frictional heat generated by the vibration of the water molecules.

In addition, the microwave oven uses a high-voltage transformer to obtain a high-voltage power source driving the magnetron by boosting a commercial AC voltage of 120/230 V. The circuit including the high-voltage transformer is induced when the initial power is turned on to start cooking. Due to the nature of the sexual load, instantaneous high inrush currents are generated.

Since the inrush current adversely affects the internal circuit components, and even more severely, the components may be damaged, and thus, a zero crossing relay (SSR: solid state relay) is applied to prevent the inrush current. .

Here, zero-crossing refers to the vicinity of an instantaneous value of zero (i.e., considering that a sinusoidal phase difference between voltage and current occurs by 90 ° when the AC power is turned on or off). As a method of performing the on / off operation at the maximum point of the voltage, an example of a representative relay for implementing this is the above-described zero crossing relay (SSR). Such a zeocrossing relay suppresses inrush current, transient voltage and switching noise by performing on / off operation in a phase period in which the maximum point of the voltage and the minimum point of the current intersect.

1 is a circuit diagram showing a conventional microwave oven.

Referring to FIG. 1, the circuit configuration of a conventional microwave oven is a relay RY1 when a door (not shown) of the microwave oven is closed, that is, in a state in which the first and second door switches SW1 and SW2 are turned on. As it is turned on, power is applied to the load circuit unit 1 and the high voltage transformer HV T.

The load circuit unit 1 includes various load circuits (not shown) necessary for driving the lamp L, the fan motor F / M, and the microwave oven. The high-voltage transformer (H.V.T) is provided with a high-voltage capacitor (H.V.C) and a high-voltage diode (H.V.D) for boosting the input voltage, and is provided with a magnetron (MGT) that is driven at a high pressure generated to generate microwaves.

In addition, a microcomputer 3 driven by receiving power from a low voltage transformer LVT of one end of the power source is provided, and the microcomputer 3 controls the operation of the relay driver 4 according to the operation of the key input unit 2. do. Therefore, by operating the relay driver 4, the relay RY1 is turned on or off.

In the conventional microwave oven configured as described above, food is first introduced into the microwave oven, and the food is cooked in a state where the door (not shown) is closed, that is, the first and second door switches SW1 and SW2 are turned on. Is performed.

In this state, when the user operates the key input unit 2 to start the operation of the microwave oven, the microcomputer 3 drives the relay driver 4 in accordance with the operation of the key input unit 2. Therefore, when the relay RY1 is turned on by driving the relay driver 4, predetermined power is applied to the load circuit unit 1 and the high voltage transformer H.V.T.

The power applied to the high voltage transformer (HVT) is stepped at a high voltage through a high voltage diode (HVD), a high voltage capacitor (HVC), etc., and this high voltage is supplied to the magnetron (MGT) to generate a microwave of 2450 MHz. Microwaves cook food in the microwave. In addition, the load circuit unit 1 operates the lamp L and the fan motor F / M, and also increases the cooking efficiency by driving a rotating plate, not shown, together.

As described above, when the initial power is supplied, that is, when the relay RY1 is turned on and the power is supplied to the load circuit unit 1 and the high voltage transformer HVT, the inrush current as described above is generated to supply the load circuit. It will adversely affect. Accordingly, in order to prevent such inrush current, the inrush current is designed to minimize the inrush current by implementing zero crossing in which the voltage and the current cross as described above through the relay RY1.

However, the relay (RY1) has an error in the mechanical contact, in particular, such a mechanical error depends on the material or manufacturing characteristics of the product has a non-uniform error for each product, due to this error does not make accurate zero crossing, In addition, there was a problem that can not automatically correct this error.

In addition, if the zero crossing is not accurate as described above, the inrush current adversely affects the internal circuit components, and in other cases, there is another problem that may cause component damage.

An object of the present invention was created to solve the problems of the prior art, it is possible to automatically correct the error of the relay without the use of expensive relays with excellent mechanical properties to achieve accurate zero crossing of the microwave oven It is to provide a crossing device.

Another object of the present invention is to provide an automatic zero crossing control method for a microwave oven to protect internal circuit components by automatically correcting an error of a relay to achieve accurate zero crossing.

1 is a circuit diagram showing a conventional microwave oven.

2 is a circuit diagram showing an auto zero crossing apparatus of a microwave oven according to the present invention.

3 is a flowchart illustrating a control method of the auto zero crossing device of the microwave oven according to the present invention.

4 is a diagram illustrating a zero crossing correction value according to an input voltage.

* Explanation of symbols for main parts of the drawings

1: load circuit 10: key input

20: microcomputer 30: voltage detector

40: relay drive unit 50: data storage unit

Dl: Diode H.V.T: High Voltage Transformer

MGT: Magnetron R1, R2: Resistance

RY1: Relay ZD: Zener Diode

In order to achieve the above object, the automatic zero crossing device of the microwave oven of the present invention is characterized in that, in a microwave oven which performs a cooking operation by driving a load circuit unit, a high voltage transformer and a magnetron through an on / off operation of a relay, A key input unit which is operated by and outputs an operation signal; A relay driver for turning on / off the relay and a voltage detector for detecting a voltage at a time when the relay is turned on; And when the relay is turned on according to an operation signal of the key input unit, the input voltage detected by the voltage detector is compared with a plurality of levels of reference voltages to determine a voltage level of the input voltage, and the relay is There is provided an automatic zero crossing apparatus for a microwave oven comprising a microcomputer for calculating a relay correction value for correcting an on timing at a zero crossing period and driving the relay driver by the relay correction value.

Preferably, the present invention further includes a data storage unit for storing the relay correction value obtained by the microcomputer under the control of the microcomputer.

In addition, the data storage unit is configured to electrically read or write data, but is composed of EEPROM (electrically erasable and programmable ROM) that does not erase the stored data even if the power is removed. The voltage detector inputs a voltage at the time when the relay is turned on through a diode and restricts the voltage to a predetermined level through a plurality of resistors and zener diodes and outputs the same to the input port of the microcomputer. Preferably, the constant level of the voltage limited through the plurality of resistors and zener diodes is set to a maximum of 5V.

In addition, a feature of the auto zero crossing control method of the microwave oven includes: a first process of turning on a relay according to a correction value previously stored in the data storage unit when a start key is input through the key input unit; A second step of detecting a voltage at a point in time at which the relay is turned on and inputting it to the microcomputer according to the first step; A third step of determining a voltage level of the detected input voltage by comparing the input voltage detected by the second process with a reference voltage preset to a plurality of levels, and for the voltage level of the determined input voltage; Comprising a fourth process of calculating a relay correction value for correcting the timing at which the relay is turned on with a zero crossing period, storing the correction value in the data storage unit, and adjusting the on time of the relay according to the relay correction value. A crossing control method is provided.

Therefore, by correcting the error of the relay automatically to achieve the correct zero crossing, it is possible to protect the internal circuit components from inrush current and overload, and to realize accurate zero crossing automatically without using expensive relays with excellent mechanical characteristics. .

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention, the same components as in the prior art will be described with the same reference numerals.

2 is a circuit diagram showing an auto zero crossing apparatus of a microwave oven according to the present invention, and FIG. 3 is a flowchart showing a control method of the auto zero crossing apparatus of a microwave oven according to the present invention, and FIG. 4 is a zero crossing according to an input voltage. It is a figure which shows the correction value.

According to FIG. 2, the circuit configuration of the microwave oven according to the present invention has a load circuit section when the door is closed, that is, the relay RY1 is turned on when the first and second door switches SW1 and SW2 are turned on. 1) and a high voltage transformer (HVT) is configured to apply power.

The load circuit unit 1 includes various load circuits (not shown) necessary for driving the lamp L, the fan motor F / M, and the microwave oven. The high-voltage transformer (H.V.T) is provided with a high-voltage capacitor (H.V.C) and a high-voltage diode (H.V.D) for boosting the input voltage, and is provided with a magnetron (MGT) that is driven by the generated high pressure to generate microwaves.

In addition, the key input unit 10 is operated by the user to output an operation signal, the relay driver 40 is turned on / off the relay (RY1), the voltage detector 30 is the relay (RY1) is turned on And to detect the voltage at the time point.

The voltage detector 30 inputs the voltage at the time when the relay RY1 is turned on through the diode D, and limits the voltage to a predetermined level through the plurality of resistors R1 and R2 and the zener diode ZD. Afterwards to output to the input port (PO1) of the microcomputer 20 to be described later. Preferably, the predetermined level of the voltage limited through the plurality of resistors R1 and R2 and the zener diode ZD is set to a maximum of 5V.

In addition, the microcomputer 20 controls the overall cooking operation of the microwave oven according to the operation signal of the key input unit 10, inputs the voltage of the voltage detector 30 to obtain a correction value of the relay RY1 obtained accordingly. Store the drive unit to drive the relay driver 40.

In addition, the data storage unit 50 stores the relay correction value obtained from the microcomputer 30. The data storage unit 50 may electrically read or write data, and is preferably configured as an EEPROM in which stored data is not erased even when power is removed.

The operation of the present invention configured as described above will be described in more detail with reference to FIGS. 3 and 4 as follows.

First, when a start key is input through the key input unit 10, a first process of turning on the relay RY1 according to a correction value previously stored in the data storage unit 50 is performed (S101 to S102).

That is, in the state where food is put into the microwave and the door (not shown) is closed, that is, the first and second door switches SW1 and SW2 are turned on, the user operates the key input unit 10 and the microwave oven. The microcomputer 20 drives the relay driver 40 in accordance with the operation of the key input unit 10. Accordingly, when the relay RY1 is turned on by the relay driver 40, a predetermined power is applied to the load circuit unit 1 and the high voltage transformer H.V T.

The power applied to the high voltage transformer (HVT) is boosted to a high voltage through a high voltage diode (HVD), a high voltage capacitor (HVC), etc., and this high voltage is supplied to the magnetron (MGT) to generate a microwave of 2450 MHz. Microwaves cook food in the microwave. In addition, the load circuit unit 1 operates the lamp L and the fan motor F / M, and also increases the cooking efficiency by driving a rotating plate, not shown, together.

As described above, when the initial power is supplied, that is, when the relay RY1 is turned on and the power is supplied to the load circuit unit 1 and the high voltage transformer HVT, the inrush current as described above is generated to supply the load circuit. It will adversely affect. Therefore, in order to prevent such inrush current, the voltage detector 30 performs a second process of detecting the voltage at the time when the relay RY1 is turned on and inputting it to the microcomputer 20 (S103).

Here, the voltage detector 20 inputs a voltage at the time when the relay RY1 is turned on through the diode D, and supplies a predetermined level (via a plurality of resistors Rl (R2) and a zener diode ZD). After limiting to 5V), it is output to the input port PO1 of the microcomputer 20 which will be described later.

In addition, when the voltage detected by the second process corresponds to a reference voltage preset to a plurality of levels as shown in FIG. 4, the data storage unit 50 may include first to fourth correction values according to the levels. In operation S104 to S112, a third process of driving the microwave oven is performed after the storage in the storage device.

In more detail, the voltage input from the voltage detector 30 to the microcomputer 20 is compared / determined with a plurality of reference voltages set in advance by the microcomputer 20. That is, as shown in FIG. 4, for example, the reference voltage is divided into five stages of 1.OV to 5.OV, and the input voltage is compared with the reference voltage. Therefore, when the input voltage is less than 1. OV, 0.83 ms is multiplied by 4 to obtain the first correction value (S104 to S105).

Here, 0.83ms is a delay time (ms) of the phase according to the reference voltage as shown in FIG. 4, and when the quarter period of the AC frequency is 4.15ms, it is a time value corresponding to five equal parts thereof. That is, as shown in FIG. 4, as the relay RY1 is actually turned on at the point E of the input voltage, the timing at which the relay RY1 is turned on at the position A of the zero crossing targeted in the present invention is set. In order to correct, the above calculation is performed to obtain the first correction value as described above.

Therefore, the corrected value is stored in the data storage unit 50, and when the microwave is driven later, this is referred to. However, since the voltage and the current have a phase difference of 90 ° C, the voltage is the maximum and the current is the minimum A. In other words, by correcting the timing so that the relay RY1 is correctly turned on at the zero crossing position, inrush current and other overload are prevented.

Here, the data storage unit 50 is an EEPROM, so that the correction value can be read or recorded electrically, but the stored data is not erased even if the power is removed. For reference.

In addition, as shown in FIG. 4, when the input voltage is less than 2.OV, 3.OV, and 4.OV, respectively, multiply values 3, 2, and 1 corresponding to 0.83 ms to obtain respective correction values. After storing the true correction value in the data storage unit 50, the microwave oven is driven (S106 to S112). Therefore, the timings respectively located at D, C, and B in FIG. 4 are moved to the zero crossing position A to correct the timing value.

As described above, according to the automatic zero crossing apparatus of the microwave oven and the control method thereof according to the present invention, the internal circuit components are protected from inrush current and overload by automatically correcting the irregular error of the relay to achieve accurate zero crossing. It is effective.

In addition, since it is possible to automatically implement accurate zero crossing without using expensive relays having excellent mechanical properties, there are other effects such as relative production cost reduction.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

Claims (6)

A microwave oven for driving a load circuit unit, a high voltage transformer and a magnetron through an on / off operation of a relay, the method comprising: a key input unit which is operated by a user and outputs an operation signal; A relay driver for turning on / off the relay; A voltage detector detecting a voltage at the time when the relay is turned on; And when the relay is turned on according to an operation signal of the key input unit, the input voltage detected by the voltage detector is compared with a plurality of levels of reference voltages to determine a voltage level of the input voltage, and the relay is And a microcomputer for calculating a relay correction value for correcting the timing to be turned on at a zero crossing period, and for driving the relay driver by the relay correction value. The apparatus of claim 1, further comprising a data storage unit for storing the relay correction value calculated by the microcomputer. 3. The auto-zero crossing apparatus of claim 2, wherein the data storage unit is an EEPROM capable of repeatedly writing and erasing data and in which the stored data is not erased even when the power is removed. The method of claim 1, wherein the voltage detector inputs a voltage at the time when the relay is turned on through a diode, and limits the output to a predetermined level through a plurality of resistors and zener diodes to output to the input port of the microcomputer. Auto zero crossing device in microwave oven. 5. The automatic zero crossing device of a microwave oven according to claim 4, wherein a predetermined level of the voltage limited by the plurality of resistors and zener diodes is set at a maximum of 5V. A first step of turning on a relay according to a correction value previously stored in the data storage unit when a start key is input through the key input unit; A second step of detecting a voltage at a point in time at which the relay is turned on and inputting it to the microcomputer according to the first step; A third step of determining a voltage level of the detected input voltage by comparing the input voltage detected by the second step with a reference voltage preset at a plurality of levels; Calculating a relay correction value for correcting the timing at which the relay is turned on with a zero crossing period with respect to the determined voltage level of the input voltage, and storing the relay correction value in a data storage unit, and adjusting the ON timing of the relay according to the relay correction value. Auto zero crossing control method of a microwave oven, characterized in that the fourth process.

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