KR19990017480A - Microwave uniform output control device and its control method - Google Patents

Abstract

The present invention relates to a uniform output control apparatus for a microwave oven and a control method thereof to obtain a uniform output from a magnetron by preventing a secondary output from being lowered by an overheating of a high voltage transformer through cooling fan control.

The configuration of the present invention, in the microwave oven, the cooling fan connected to the power supply terminal so that the power is not cut off by the safety switch and the switching means, the cooling fan connected in series with the cooling fan to cut off the power applied to the cooling fan from the power supply terminal When the temperature read from the switching means, transformer temperature, or temperature sensor is higher than the set temperature, the cooling fan is switched to close the cooling fan to drive the cooling fan to cool the transformer, and the temperature read from the temperature sensor is set. When the temperature is lower than the cooling fan switching means characterized in that it comprises a control unit for stopping the cooling fan.

According to the present invention, even if the cooking operation is stopped by placing the temperature sensing means in the high pressure transformer, the cooling fan is further driven until the temperature of the high pressure transformer is lowered to a predetermined temperature or less, thereby rapidly cooling the magnetron. Therefore, there is an excellent effect of maintaining the output of the magnetron uniformly during the cooking operation by preventing the secondary output decrease by the temperature rise of the high-voltage transformer during repeated cooking.

Description

Microwave uniform output control device and its control method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniform output control apparatus for a microwave oven and a control method thereof. In particular, a microwave oven uniformly obtains a uniform output in a magnetron by preventing a decrease in secondary output caused by overheating of a high voltage transformer through cooling fan control. An output control apparatus and a control method thereof.

In general, a microwave oven is a cooking appliance equipped with a magnet generator, which is a microwave generator, to irradiate foods with microwaves generated from the magnetrons to move food molecules to cook foods using heat generated at this time. This magnetron is a kind of vacuum tube, and a high current is applied to the anode and the cathode to generate microwaves. Therefore, a high voltage transformer for supplying such a high current is provided. The high voltage transformer is composed of a primary winding connected to a power supply and a secondary winding connected to a load. If the power supply is continuously performed, the resistance thereof increases due to the temperature rise of the coil. As a result, the magnetron also causes a decrease in output due to a decrease in output at the secondary side of the high voltage transformer. Therefore, cooling means, i.e., cooling fans, are provided for preventing such output reduction.

1 illustrates an electric circuit diagram of a conventional microwave oven, and will be described with reference to the driving of a cooling fan that is a cooling device of a magnetron.

First, when the user puts food to be cooked in the state of supplying power through the plug 1 and closes the door, the safety switches 2 and 3 composed of micro switches are interlocked by the door latch to close the circuit. In addition, the monitor switch 4 constituting the short circuit is interlocked to open the short circuit. When the cooking command is input, the main relay switch 5 and the power switch 6 close the circuit to supply power to each load. That is, the cooking lamp 7 is turned on, the drive motor 8 for rotating the turntable is driven, and the cooling fan 9 for air-cooling the high voltage transformer HVT and the magnetron 10 is driven. Microwave oscillation occurs in the magnetron 10 that is powered up through the high voltage transformer HVT to perform a cooking operation.

Thereafter, when the cooking operation is completed, the main relay switch 5 and the power switch 6 are opened to cut off the power supply to the magnetron 10, and at the same time, the driving of the drive motor 8 and the cooling fan 9 also stops. As a result, the cooling operation to the high voltage transformer (HVT) is stopped.

However, the cooling fan control circuit for maintaining a uniform output of the conventional microwave oven has the following problems.

That is, when the cooking is finished, the cooling fan and various loads are stopped, and thus the cooling operation of the high-voltage transformer (H.V.T) is also stopped. Therefore, in order to cool the high pressure transformer (HVT) below a certain temperature at room temperature, a lot of time is inconvenient, etc., and if the cooking operation is performed before the temperature of the high pressure transformer (HVT) is cooled to an appropriate temperature, The decrease in output on the secondary side is caused by the increase of the self-resistance value caused by the temperature rise of the high-voltage transformer. Accordingly, there is a problem that the initial output is reduced during cooking because the proper size power is not applied to the magnetron.

The present invention has been made to solve the above-mentioned problems, the object is to provide a high temperature transformer temperature sensing means, even if the cooking operation is finished, further drive the cooling fan until the temperature of the high voltage transformer is lowered below a certain temperature and repeated cooking It is to provide a uniform output control device of the microwave oven so that even the initial output is made uniform.

1 is an electric circuit diagram of a conventional microwave oven,

2 is an electric circuit diagram of a microwave oven according to the present invention;

3 is a partially cutaway perspective view of the microwave oven to which the present invention is applied;

4 is a control block diagram of a microwave oven according to the present invention;

5 is a flowchart illustrating an operation procedure executed by the controller of FIG. 4.

Explanation of symbols for main parts of the drawings

20: noise filter part 30: low pressure part 31: cooking chamber lamp

32: drive motor 33: fan motor 34, 35: safety switch

36: monitor switch 37: main relay switch 38: power switch

40: high voltage part 41: high pressure capacitor 42: high voltage diode

44: magnetron 45: temperature sensor H.V.T: high voltage transformer

In order to achieve the above technical problem, a configuration of the present invention includes a transformer for powering up to a predetermined size by receiving power from a power supply terminal, a magnetron for generating a microwave by receiving power supply boosted by the transformer, and the power supply from the power supply terminal to the transformer. A microwave oven provided with a safety switch for blocking the applied power when the door is opened and a switching means for controlling the power applied to the transformer during the cooking operation, so that the power is not blocked by the safety switch and the switching means. A cooling fan connected to a power supply terminal, a cooling fan switching means connected in series with the cooling fan to cut off power applied to the cooling fan from the power supply terminal, a temperature sensor unit for reading a temperature of the transformer, and the temperature sensor Read temperature is set A control unit for closing the cooling fan switching means to drive the cooling fan to cool the transformer, and opening the cooling fan switching means to stop the cooling fan when the temperature read from the temperature sensor is lower than the set temperature. It is characterized by including.

Hereinafter, one preferred embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

2 is an electric circuit diagram of a microwave oven according to the present invention, FIG. 3 is a partially cutaway perspective view of the microwave oven to which the present invention is applied, FIG. 4 is a control block diagram of the microwave oven according to the present invention, and FIG. A flowchart showing the operation procedure to execute.

First, the electrical circuit diagram of the present invention with reference to FIG. 2 as follows.

Noise filter unit 20 for removing the noise component included in the input AC power applied from the power supply terminal, Low voltage unit 30 including all the electrical components driven by the input AC power source, generating a high frequency electromagnetic wave The high voltage part 40 including the magnetron 44 and the components for driving the magnetron 44, and a control unit (not shown) for controlling the operation of the respective parts.

In the above-described configuration, the low pressure unit 30 includes a cooking lamp 31 for illuminating the inside of the cooking chamber, a drive motor 32 for rotating the food so that the microwave can be irradiated evenly, and a magnetron 44 and a high voltage transformer in the electrical equipment room. (HVT) and the cooling fan 33 for ventilating the smell in a cooking chamber are provided in parallel connection. In addition, the low pressure unit 30 is provided with various switches for controlling the power, the first and second safety switches 34 and 35 and the monitor switch 36 provided with a micro switch is interlocked according to the opening and closing of the door, When the door latch is retracted due to the opening of the door, the first and second safety switches 34 and 35 are configured to open the circuit and cut off the power supply to the drive motor 32 and the high voltage part 40. In addition, the monitor switch 36 constitutes a short circuit when the safety switch malfunctions, and is configured to cut off the fuse of the circuit stage to cut off the power applied to the high voltage unit 30. In addition, a relay switch operated according to a control procedure of a controller (not shown) is provided. First, the main relay switch 37 opens and closes a circuit only in a state in which a cooking operation is not performed. (31) is circuit-connected so that it lights up automatically. In addition, the power switch 38 controls the output of the magnetron 44 to control the output of the magnetron 44 according to the on / off pattern preset by the controller to vary the intensity of cooking according to each food characteristic. Control. In addition, a cooling fan relay switch 39 for controlling the driving of the cooling fan 33 is provided, and the cooling fan 33 is connected in parallel to the rear end of the noise filter unit 20 and is circuit-configured so that power is always applied. In addition, a cooling fan relay switch 39 is provided to control the power applied to the cooling fan 33 at all times. Therefore, the cooling fan 33 is driven according to the on / off control of the cooling fan relay switch 39 of the control unit.

The high voltage unit 30 is a magnetron 44, which is a kind of vacuum tube, a high voltage transformer (HVT) for boosting the input AC voltage to a predetermined size, and a back pressure and rectified AC power boosted by the high voltage transformer (HVT). It consists of a high pressure capacitor 41 and a high pressure diode 42 to be applied to. In other words, the magnetron, a kind of vacuum tube, emits electrons by applying a current of 3.3 volts (V) and 10 amps (A) to the cathode, and a current of 4.2 kilovolts (KV) and 300 milliamps (mA) is applied to the anode. The emitted electrons are resonated (2450 MHz) and then irradiated into the cooking chamber through the antenna. Therefore, a high voltage transformer (H.V.T) is provided as a means for supplying such a high current. This high voltage transformer (HVT) modulates the magnitude of AC voltage and current by using electromagnetic induction. It consists of the primary winding connected to the power supply terminal and the secondary winding connected to the magnetron, which is the load, and the thin silicon steel sheet. It is made of stacked iron cores. In general, when a current is applied to the coil to be wound, the temperature of the coil and the iron core is increased due to the influence of the magnetic field due to the flow of the current as well as the resistance of the coil itself. This increase in temperature increases the resistance of the coil itself, resulting in a decrease in the output voltage from the secondary winding. Therefore, in order to prevent such a decrease in output, cooling to maintain and maintain the temperature of the high voltage transformer (HVT) at an appropriate level. Means are provided. That is, when the temperature sensor 45 is attached to the position of the high voltage transformer HVT and the temperature value of the high voltage transformer HVT is read through the controller, the cooling fan relay switch 39 is turned on. The on / off control is performed to cool the high voltage transformer (HVT).

3 is a partially cutaway perspective view of the microwave oven to which the present invention is applied. Referring to the electrical equipment compartment 50, a magnetron 44 provided with a plurality of cooling fins 46 for oscillating microwaves is mounted on an upper portion thereof. The high voltage transformer (HVT) for applying the boost AC power to the magnetron 44 is located. In addition, a cooling fan 33 for cooling the magnetron 44 and the high-voltage transformer (H.V.T) is attached to the rear of the microwave oven to blow outside air into the electrical equipment compartment 50. In addition, the temperature sensor 45 is mounted in place of the high-voltage transformer (H.V.T) so that the control unit can read the current temperature of the high-voltage transformer (H.V.T) through it well.

Figure 4 is a control block diagram of a microwave oven according to the present invention, a large temperature sensing unit 60 for detecting the temperature of the high-voltage transformer (HVT) and the relay driver 70 for driving the cooling fan 33, temperature When the temperature of the high-voltage transformer (HVT) read through the detection unit 60 exceeds the appropriate temperature value, the control unit 100 for controlling the driving of the cooling fan 33 through the relay drive unit 70 is configured.

Among the above-described components, the temperature sensing unit 60 includes a resistance element 61, a temperature sensor 45, and a capacitor 62 connected in parallel with the temperature sensor 45.

In addition, the relay driver 70 includes a voltage divider resistor 71 and 72 for dividing the output signal of the controller 100 to a proper pressure, a transistor 73 connected to a base terminal at the voltage divider resistor stage, and a switching means. A relay 39 for controlling the supply power to the cooling fan 33 by the switching operation is provided in connection with the collector terminal of the transistor 73.

Hereinafter, an operation procedure in the controller 100 will be described with reference to FIG. 5.

First, when the user puts food to cook in the state of power supply and closes the door, the safety switches 34 and 35 composed of micro switches are interlocked by the door latch to close the circuit, and also constitute a short circuit. The monitor switch 36 is interlocked to open the short circuit. When the cooking command is input, the main relay switch 37 and the power switch 38 close the circuit to supply power to each load. That is, the cooking lamp 31 is turned on, the drive motor 32 for rotating the turntable is driven, and the oscillation of the microwaves in the magnetron 44, which is supplied with the boosted power through the high voltage transformer HVT, The cooking operation is performed.

At the same time, the temperature is sensed from the temperature sensor 45 attached to the iron core at the same time as the power supply to the microwave oven (H.V.T).

Subsequently, the controller 100 analyzes the signal input from the temperature sensor 45 to determine whether the temperature of the current high voltage transformer H.V.T is greater than or equal to a preset set temperature T (S2).

As a result of determination, the temperature of the high-voltage transformer (H.V.T) is continuously measured when the temperature is lower than the set temperature (T), and the cooling fan 33 is driven when the temperature is higher than the set temperature (T) (S3).

Therefore, in the high pressure transformer (H.V.T), air cooling is performed by the flow of air.

Thereafter, the control unit 100 continuously cools the cooling fan 33 when the signal input from the temperature sensor 45 attached to the iron core of the high-pressure transformer is not lower than or equal to a preset set temperature T even when cooking is finished. ). Therefore, the high pressure transformer (H.V.T) is cooled more rapidly than the natural cooling at conventional room temperature. Accordingly, it is possible to prevent the secondary output decrease due to the temperature rise of the high-voltage transformer (H.V.T) during the next cooking operation.

That is, the controller 100 analyzes the signal input from the temperature sensor 45 and determines whether the temperature of the current high voltage transformer H.V.T is less than or equal to a preset set temperature T (S4).

As a result of determination, the cooling fan 33 is continuously driven when the temperature is higher than the set temperature T, and the cooking fan is completed by stopping the cooling fan 33 when the temperature is lower than the set temperature T (S5).

And the above-described temperature sensor 45 is configured in various ways, for example, under a certain temperature to transmit the on-signal to the control unit 100, when the predetermined temperature or more by sending an off signal to control the temperature rise of the magnetron 44 ( 100). In addition, when the temperature is increased by using a dummyistor having a negative resistance coefficient, the resistance value decreases. On the contrary, when the temperature is low, the controller 100 uses an electric signal input from the temperature sensor 45 by using the property of increasing the resistance value. By analyzing the size of the temperature information of the magnetron 44 is obtained.

In addition, this invention is not limited to the said Example, It can change and implement variously in the range which does not deviate from the summary.

As described in detail above, according to the present invention, even if the cooking operation is stopped by placing the temperature sensing means in the high pressure transformer, the cooling fan may be further driven until the temperature of the high pressure transformer is lowered below a certain temperature to rapidly cool the magnetron. It has an effect. Therefore, there is an excellent effect of maintaining the output of the magnetron uniformly during the cooking operation by preventing the secondary output decrease by the temperature rise of the high-voltage transformer during repeated cooking.

Claims (3)

A transformer for boosting power to a certain size by receiving power from a power supply terminal, a magnetron for generating a microwave by receiving power boosted by the transformer, a safety switch for shutting off power applied to the transformer from the power supply terminal when the door is opened; In a microwave oven provided with a switching means for controlling the power applied to the transformer during the cooking operation, the cooling fan connected to the power supply end so that the power is not cut off by the safety switch and the switching means, the cooling from the power supply end Cooling fan switching means connected in series with the cooling fan to cut off the power applied to the fan, a temperature sensor unit for reading the temperature of the transformer, the cooling fan switching when the temperature read from the temperature sensor unit is higher than the set temperature Shut up the means And a controller for driving the cooling fan to cool the transformer and opening the cooling fan switching means to stop the cooling fan when the temperature read from the temperature sensor is lower than a predetermined temperature. Output control unit. The temperature sensor of claim 1, wherein the temperature sensor unit is attached to an iron core of the transformer and outputs a specific signal to the controller when a temperature of a predetermined temperature or more is sensed, a resistance element connected between the temperature sensor and the controller, and the resistor. A parallel output between the device and the temperature sensor is grounded, and a uniform output control device for a microwave oven, characterized in that it comprises a capacitor for removing noise components. A temperature sensing step of reading and sensing the temperature of the transformer every predetermined time when power is applied, a cooling step of driving a cooling fan when the temperature of the transformer is higher than a preset temperature, and continuously performing the temperature sensing step even while performing the cooling step. And a stop step of stopping the cooling fan when the temperature read in the temperature detection step is equal to or less than a predetermined temperature.