JPH0735352A - Microwave oven - Google Patents

Abstract

PURPOSE:To to supply a specific electrified power to food to achieve a very good finish in cooking not depending on working power voltages by a method wherein supply voltages to a microwave oven are detected and electric powers to a highfrequency generator and a heater are controlled. CONSTITUTION:A microwave oven is provided with a high-frequency generator 2 and a heater 3 which are connected to a commercial power source and used to heat food, a low voltage transformer 4 which reduces voltages to a specified voltage, a rectifying element 5 which rectifies secondary voltages of the low- voltage transformer 4, a capacitor 6 which smooths outputs of the rectifying element 5, a voltage detecting circuit 7 which detects smoothed voltages in parallel with the capacitor 6, and a control circuit 8 which controls the high-frequency generator 2 and the heater 3 according to voltages detected by the voltage detecting circuit 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven for correcting the control of a high frequency oscillator and a heater by a commercial power supply voltage supplied.

[0002]

2. Description of the Related Art FIG. 5 shows a circuit diagram of a conventional microwave oven. A high frequency oscillator 2 that heats food is connected from a commercial power source via an inverter 1 that controls power.
Similarly, from a commercial power source, a heater 3 for heating food and a low-voltage transformer 4 for supplying a predetermined voltage to a control circuit are connected. A control circuit 13 is connected to the secondary side of the low-voltage transformer, and a control signal to the inverter 1 and a relay 9 connected in series with the heater 3 are operated based on a predetermined sequence to provide food. It's supposed to be heated.

[0003]

However, in this configuration, if a commercial power source having a low power source impedance and a normal rated voltage is supplied to the inverter and the heater, a predetermined amount of power is supplied to the food and cooking is possible. Although there is no problem with the condition, in reality, the power supply impedance, the power supply voltage, etc. differ depending on the environment in which it is used, and the power supplied to the food from the inverter and heater also differs, causing a problem of poor cooking performance. .

Generally, the cooking sequence built into the control circuit is prepared by a standard power source. However,
The power consumption of high-frequency oscillators and heaters may exceed 1 kW, and their outputs are affected by the power source impedance. In addition, the influence of the voltage drop due to the line impedance may not be ignored.

Therefore, the present invention provides a power source impedance,
A first object of the present invention is to provide a microwave oven which is not affected by the line impedance and the power supply voltage and supplies a predetermined amount of electric power to food to improve the cooking performance.

A second object of the present invention is to provide a microwave oven in which the quality of cooking is further improved by improving the accuracy of the amount of power supplied to food.

[0007]

According to the structure of the present invention, in order to achieve the first object, a high-frequency oscillator for heating food, which is connected in parallel to a power source, and a heater and a power source voltage are set to a predetermined voltage. To a transformer, a rectifying element that rectifies the secondary side voltage of the transformer, a capacitor that smoothes the output of the rectifying element, a voltage detection circuit that detects a smoothed voltage in parallel with the capacitor, and the voltage detection circuit. A control circuit for controlling the high frequency oscillator and the heater depending on the voltage is used.

In order to achieve the second object, the present invention provides a high frequency oscillator for heating food, a transformer connected in parallel with a power source, a transformer for transforming a power source voltage into a predetermined voltage, and a secondary of the transformer. A rectifying element for rectifying the side voltage, a capacitor for smoothing the output of the rectifying element, a voltage detection circuit for detecting a smoothed voltage in parallel with the capacitor, and a waveform shaping circuit for shaping the secondary side voltage of the transformer. A control circuit that controls the high-frequency oscillator and the heater depending on the voltage of the voltage detection circuit and the waveform of the waveform shaping circuit, the control circuit depending on the waveform shaping circuit when the capacitor is charged. And a timing circuit for detecting the voltage of the voltage detection circuit.

[0009]

The microwave oven of the present invention is capable of supplying a predetermined amount of food as food without being affected by the power source impedance, the line impedance and the power source voltage due to the first configuration.

Further, the microwave oven of the second structure can ignore variations in circuit components and variations due to aging, so that the accuracy of the amount of power supplied to food can be improved and, as a result, the degree of cooking can be improved. It can be further improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The same parts and components as those of the conventional example are designated by the same reference numerals.

FIG. 1 is a circuit diagram of a microwave oven according to an embodiment of the present invention. A high frequency oscillator 2 that heats food is connected from a commercial power source via an inverter 1 that controls power. Similarly, from a commercial power source, a heater 3 for heating food and a low-voltage transformer 4 for supplying a predetermined voltage to the circuit are connected. A rectifying element 5 for rectifying the output and a capacitor 6 for smoothing the rectified waveform are connected to the secondary side of the low voltage transformer 4. A control circuit 8 is connected from a voltage detection circuit 7 that divides the voltage of the capacitor 6. The control circuit 8 controls the control signal to the inverter 1 and the relay 9 connected in series with the heater 3 according to the input voltage from the voltage detection circuit. FIG. 2 shows an example thereof. In FIG. 2, the horizontal axis shows the voltage detection circuit voltage, and the vertical axis shows the ON / OFF duty of the relay. The control circuit 8 controls the duty to be high when the voltage detection circuit voltage is low, and the duty to be low when the voltage detection circuit voltage is high so as to keep the power supplied to the food constant. This control circuit may be composed of a microcomputer or a discrete circuit.

That is, the microwave oven of the present invention detects the power source impedance, the line impedance, and the voltage supplied to the microwave oven due to fluctuations in the power source voltage, and acts to supply a predetermined amount of power to food, regardless of the operating environment. The cooking quality can be improved.

Next, another embodiment of the present invention will be described with reference to FIG. 3 is different from the above embodiment in that a waveform shaping circuit 10 for shaping the power supply waveform from the secondary side of the low voltage transformer and detecting the charge / discharge timing of the capacitor 6 is connected to the control circuit 11. It is connected.
The control circuit 11 has a timing circuit 12 that detects the value of the voltage detection circuit at a predetermined timing by the input of the waveform shaping circuit.

The operation of the timing circuit 12 is shown in FIG. The secondary side voltage of the low voltage transformer becomes as shown by the broken line by the rectifying element. The output voltage of the voltage detection circuit 7 is smoothed by the capacitor and becomes a voltage shown by a solid line. However, when the capacitor is discharged, the output voltage of the voltage detection circuit changes as indicated by the alternate long and short dash line A and B due to the capacitance of the capacitor. Therefore, the timing circuit 12
A configuration in which a delay of T0 time from the fall of the input voltage from the waveform shaping circuit 10 to at least the capacitor charging period is provided so that it is read during charging T of the capacitor in which the output voltage of the voltage detection circuit 7 does not change. According to this configuration, since variations in capacitors and variations in voltage detection voltage due to aging can be ignored,
The accuracy of the amount of power supplied to food can be improved, and the quality of cooking can be further improved.

[0016]

As described above, according to the microwave oven of the present invention, the following effects can be obtained.

(1) The power supply impedance, the line impedance, and the supply voltage to the microwave oven due to the fluctuation of the power supply voltage are detected, and the predetermined power is supplied to the food so that the food can be cooked regardless of the use environment. Can be very good.

(2) Since variations in voltage detection voltage due to variations in electronic parts and aging can be ignored, it is possible to improve the accuracy of the amount of electric power supplied to food and further improve the quality of cooking. it can.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a microwave oven according to an embodiment of the present invention.

FIG. 2 is a control characteristic diagram of the microwave oven according to the embodiment of the present invention.

FIG. 3 is a circuit diagram of a microwave oven according to a second embodiment of the present invention.

FIG. 4 is a control characteristic diagram of the microwave oven according to the embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional microwave oven.

[Explanation of symbols]

 2 high frequency oscillator 3 heater 4 transformer 5 rectifier 6 capacitor 7 voltage detection circuit 8 control circuit 10 waveform shaping circuit 11 control circuit 12 timing circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Fukutomi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A high frequency oscillator and a heater connected in parallel to a power source for heating food, a transformer for transforming a power source voltage to a predetermined voltage, a rectifying element for rectifying a secondary side voltage of the transformer, and the rectifying element. A microwave oven including a capacitor for smoothing the output of the device, a voltage detection circuit for detecting a smoothed voltage in parallel with the capacitor, and a control circuit for controlling the high-frequency oscillator and the heater according to the voltage of the voltage detection circuit. 2. A high frequency oscillator for heating food, a transformer connected in parallel to a power source, a transformer for transforming a power source voltage to a predetermined voltage, a rectifying element for rectifying a secondary side voltage of the low voltage transformer, and the rectifier. A capacitor that smoothes the output of the element, a voltage detection circuit that detects a smoothed voltage in parallel with the capacitor, a waveform shaping circuit that shapes the waveform of the secondary side voltage of the transformer, a voltage of the voltage detection circuit, and the waveform. A control circuit that controls the high-frequency oscillator and the heater according to the waveform of the shaping circuit, and the control circuit depends on the signal from the waveform shaping circuit to detect the voltage of the voltage detection circuit when the capacitor is charged. A microwave oven with a circuit.