KR20010066583A - Power control method for inverter microwave oven - Google Patents

Abstract

PURPOSE: An output control method of an inverter microwave oven is provided to prevent the damage on electrical equipment and to improve the reliability of an inverter microwave oven by limiting continuous high output motion. CONSTITUTION: An output controlling method of an inverter microwave oven comprises the steps of: determining current values of both terminals of a magnetron and operating time in high output motion; deciding if the currents detected by the oscillation of the magnetron approach the predetermined current values; outputting time lag between the time for the detected currents to approach the predetermined current values and the predetermined operating time; and limiting the high output motion of the magnetron when the time lag is included in a specific range. Therefore, the damage on electrical equipment due to overheating is prevented. Moreover, the reliability of the inverter microwave oven is improved.

Description

Power control method for inverter microwave oven

The present invention relates to an output control method of an inverter microwave oven, and more particularly, to an output control method that can prevent the temperature rise and component damage of parts in the product due to the continuous high output.

The inverter microwave oven controls the magnetron which is a drive source by the inverter system. The inverter method can vary the amount of high frequency output of the magnetron as a driving source.

The magnetron oscillates a high frequency output until current flows to the anode of the magnetron only after the internal heater generates heat. The current generated at this time is called a positive current, and the product of the positive current and the positive voltage is the power P applied to the magnetron. When the power is multiplied by the efficiency of the magnetron, a high frequency output amount is generated according to the magnitude.

Therefore, the amount of current flowing through the magnetron corresponds to the output amount of the high frequency, and when the current flows a lot, the output increases, and when the current flows low, the high frequency output decreases.

By the way, in the conventional inverter microwave oven, when the user requests high power control, it is configured to always accept this and control the magnetron at high power. Will cause the magnetron to oscillate at high power again, regardless of whether high power is available.

Therefore, in the conventional inverter microwave oven, as the magnetron is controlled to operate continuously at a high output, a problem arises in that the electric components in the microwave are overheated, resulting in damage to the components. Such a problem lowers the reliability of the product and at the same time brings about a fire.

Accordingly, an object of the present invention is to provide an output control method of an inverter microwave oven capable of monitoring continuous operation by high output of the inverter microwave oven and limiting continuous high output operation.

1 is a configuration diagram of an inverter microwave oven according to the present invention;

2 is a cathode voltage, a current characteristics of the magnetron according to the present invention,

3 is an operation flowchart for detecting an anode voltage, an arrival time, and an anode current at high power in an inverter microwave oven according to the present invention;

4 is a flow chart for the continuous operation control of the inverter microwave oven according to the present invention.

Explanation of symbols on the main parts of the drawings

10: power supply unit 15, 50: rectifier circuit

20: inductor 25: transformer

30: switching unit 35: microcomputer

40: magnetron 45: current transformer

55: inverter drive unit

According to an aspect of the present invention, there is provided an output control method of an inverter microwave oven, the method comprising: detecting and presetting an amount of anode current and an operation time during a high output operation of a magnetron; Determining whether the anode current at which the magnetron is detected as oscillation has reached the set cathode current; Calculating a time difference between a time when the detection anode current reaches a setting anode current and a setting operation time; When the time difference is within a certain range, it comprises a step of limiting the high power operation of the magnetron.

Hereinafter, an output control method of an inverter microwave oven according to the present invention will be described with reference to the accompanying drawings.

1 is a block diagram of an inverter microwave oven according to the present invention.

Inverter microwave oven, the rectifier circuit 15 for rectifying the input AC power source 10, and the current rectified in the rectifier circuit 15 is applied to the primary side of the transformer 25 through the inductor 20. On the secondary side of the transformer 25, a magnetron 40 for generating microwaves is mounted. That is, the magnetron 40 is driven by the voltage induced on the secondary side of the transformer 25 to generate a microwave.

On the other hand, the primary side voltage of the transformer 25 is controlled by the power switching unit 30. The power switching unit 30 is controlled on / off by the PWM control signal output from the inverter driver 55 to control the high voltage applied to the transformer 25. The inverter driver 55 operates under the control of the microcomputer 35.

The current flowing through the magnetron 40 is detected by the current transformer 45, and the detected current is output through the rectifying circuit 50. The current amount signal flowing through the magnetron 40 detected by the current transformer 45 is applied to the microcomputer 35.

On the other hand, the magnetron 40 is in a state where only a high voltage is applied from the transformer 25 without current flowing to the anode of the magnetron until the heater inside is heated to release the hot electrons. The state at this time is called a non-oscillation region, and it takes about 2 seconds for the heater of the magnetron 40 to normally emit hot electrons to generate high frequency.

That is, the current flows to the anode of the magnetron 40 only after the normal oscillation of the magnetron 40 is performed by the heater. The current at this time is called an anode current, and as shown in FIG. 2, the product of the anode current and the anode voltage is the power P applied to the magnetron 40. When the power P is multiplied by the efficiency of the magnetron 40, high frequency is generated according to the magnitude.

Therefore, the current flowing in the magnetron 40 corresponds to the output of the high frequency, and when the current is operated to flow a lot, the output is high, and when operated to flow less, the high frequency output is lowered. That is, the amount of current detected by the current transformer 45 is applied to the microcomputer 35 to control the amount of current flowing through the magnetron 40 and used to control the generated high frequency output.

The following describes a process of controlling the output during the continuous operation by the high output in the inverter microwave oven according to the present invention having the above configuration.

3 is an operation flowchart for detecting the anode voltage, the arrival time, and the anode current at high power in the inverter microwave oven according to the present invention.

In the present invention, the high output state of the inverter microwave oven is described as an example of the initial operation state.

As mentioned above, the magnetron 40 of the inverter microwave oven does not flow current to the anode of the magnetron until the heater inside is heated to release the hot electrons, and only the high voltage is applied from the transformer 25. do. After the heater is heated, until the anode current flows in the magnetron, and before the first heating, the anode voltage reaches a predetermined size to allow a predetermined high output from the magnetron. Therefore, during this period, the magnetron must be supplied with a positive voltage above a certain size.

Accordingly, the microcomputer 35 controls the magnetron 40 to be continuously supplied with voltage until the high power of a predetermined size is generated from the magnetron 40 during the initial heating operation (step 100).

The control operation is as follows. The PWM control signal is applied to the inverter driver 55 from the microcomputer 35, and the inverter driver 55 generates a drive signal for on / off control of the switching unit 30 according to the PWM control signal. . The switching unit 30 adjusts the primary side voltage of the transformer 25 while the on time is controlled by the on / off driving signal of the inverter driver 55.

In this operation, the high voltage applied to the primary side of the transformer 25 is induced to the secondary side of the transformer to generate the operating voltage of the magnetron 40. Therefore, the microcomputer 35 controls the voltage applied to the magnetron 40 through the transformer 25 to continuously increase until the high frequency output generated from the magnetron 40 reaches a predetermined size or more. do.

Thereafter, when a high frequency output of a predetermined size or more is generated in the magnetron 40 (step 103), the microcomputer 35 detects the magnitude of the anode voltage V1 applied to the magnetron 40 at this time. The anode current I1 of the magnetron 40 detected from the current transformer 45 is input (step 106).

By performing the operation up to the 106th step, the anode voltage V1 and the anode current I1 when the magnetron 40 is oscillated with high output are detected. The microcomputer 35 detects the present time T1 at which the anode voltage V1 and the anode current I1 are detected (step 109), and the detected anode voltage V1 and the anode current I1. Then, the current time T1 is stored in the internal memory (step 112). The time T1 means a current time when the magnetron 40 operates at a high output.

That is, the performance from the 100th to the 112th step is performed when the high output of a predetermined size or more is generated from the magnetron 40, and the operating time T1, the anode voltage V1 and the anode current I1 at that time are generated. This is an operation for detecting. At this time, the positive voltage (V1) and the positive current (I1) detected according to the operation of the magnetron 40 is approximately the same or similar in magnitude as the output generated when the user requests cooking in a microwave oven. .

If the user requests a high output of the microwave oven even in the case of the non-initial heating operation, the operation time, anode voltage, and anode current when the magnetron 40 is controlled at high output are detected and stored. Therefore, the execution of the steps 100 through 112 is not limited to the initial heating operation, and the operation time, the anode voltage, and the anode current when the magnetron 40 is controlled at high output may be described as a detection operation.

The operation time T1, the anode voltage V1, and the anode current I1 thus detected are stored in the internal memory of the microcomputer 35.

Next, Figure 4 is a flow chart for the continuous operation control of the inverter microwave oven according to the present invention.

When the command according to the cooking start is input from the user, the microcomputer 35 determines whether the heating operation is continuous (step 200). The determination of the 200th step may be possible in various ways. First, the microcomputer 35 always stores the last operation time of the magnetron 40, and it is possible to determine whether the operation is continuous compared to the current operation start time. Secondly, the microcomputer 35 may detect the temperature in the cooking chamber and determine the continuous operation when the temperature in the cooking chamber is above a certain temperature.

When it is determined from the 200th step that the continuous heating operation is performed, the microcomputer 35 has the magnitude of the positive voltage V2 supplied to the magnetron 40 at the high output positive voltage V1 stored in the memory. It is determined whether the size is the same as or similar to the size (step 203).

When the two anode voltages V1 and V2 are substantially the same or similar in step 203, the anode current I2 flowing through the magnetron 40 is detected. The positive current I2 is detected by the current transformer 45. When the magnitude of the anode current I2 reaches the magnitude of the anode current I1 detected at the high output of the magnetron 40 (step 206), the microcomputer 35 displays the currently detected anode current ( The time T2 at which I2) reaches the predetermined anode current I1 is detected (step 209).

The microcomputer 35 calculates a time difference between the time T1 stored in the memory and the current time T2 (step 212).

When the time difference between the two times T1 and T2 calculated in step 212 is smaller than the predetermined time ΔT (step 215), the microcomputer 35 shows the magnetron 40 as shown in FIG. 2. The high power control of the control is limited, and the magnetron 40 is controlled to oscillate at the normal output (step 218). That is, in step 218, when the magnetron 40 oscillates continuously at a high output within a predetermined time, a fear of temperature increase and damage of components may occur.

Therefore, in this case, the microcomputer 35 controls by reducing the anode voltage supplied to the magnetron 40. That is, by controlling the primary side voltage applied to the transformer 25 through the switching unit 30, the high output operation of the magnetron 40 is limited. That is, as shown in Fig. 2, the output of the magnetron 40 is represented by the product of the anode voltage and the anode current, so that at the normal output, the anode voltage is reduced to control the high frequency output.

However, when the time difference between the two times T1 and T2 in step 215 is greater than a predetermined time ΔT (step 215), the microcomputer 35 performs the high power control of the magnetron 40 (step 221). . That is, step 221 is not a continuous high output control operation of the magnetron 40, the magnetron 40 is operated at a high output.

That is, if the same anode voltage is continuously maintained in the magnetron 40, since the anode current continuously increases due to the output characteristics of the magnetron, the output of the magnetron 40 increases. When the high power control of the magnetron 40 is continuously performed, the temperature of the electric component is increased, leading to component damage, thereby limiting the continuous high power control of the magnetron 40.

Therefore, the present invention stores the operation time when high power control of the magnetron 40 is performed, and determines whether the magnetron is continuous high power control by using the difference with the operation time of the next high power request, and when the continuous high power control is performed. It is trying to limit this.

As described above, in the output control method of the inverter microwave oven according to the present invention, when the high output operation of the magnetron is repeated, component damage occurs while the temperature of the electronic component is overheated, and thus the reliability of the product is lowered, resulting in a risk of fire. This can occur, preventing the high power operation of the magnetron from being performed continuously. Accordingly, the present invention determines the continuous high output operation of the magnetron 40 by using a current detection function of the magnetron 40 of the inverter microwave oven. And it limits the high output of magnetron in continuous operation. Therefore, the present invention prevents damage to parts of the product and obtains the effect of increasing the reliability of the product.

Claims (1)

Detecting and presetting an amount of anode current and an operation time during the high output operation of the magnetron; Determining whether the anode current at which the magnetron is detected as oscillation has reached the set cathode current; Calculating a time difference between a time when the detection anode current reaches a setting anode current and a setting operation time; Limiting the high output operation of the magnetron when the time difference is within a certain range, the output control method of the inverter microwave oven.