JPS6269485A - Cooking device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a cooking appliance in which power is supplied to a magnetron by an inverter circuit.

[Technical background of the invention and its problems]

BACKGROUND ART Conventionally, cooking devices such as microwave ovens automatically end cooking when a preset cooking time elapses or when the temperature of the food reaches a preset 1H degree.

By the way, in such a cooking device having an automatic cooking function, the user may not be aware of the completion of cooking, and the food may remain in the heating chamber and cool down.

To address this problem, some devices have been designed to turn on and off electricity to the magnetron at the same time as cooking is completed, thereby moisturizing the food with a low output.

However, in such output control by turning on and off the power, the human power to the entire electric range changes on and off as the power is turned on and off, causing a surge current (rush current) to flow in the circuit and damage the electrical equipment. This has the disadvantage of having a negative impact on the lifespan of the

[of the invention]

This invention was made in view of the circumstances mentioned in item 1 above.The purpose of this invention is to be able to shift to low-output thermal cooking as soon as cooking is completed, and to reduce the input power consumption during thermal cooking. on.

An object of the present invention is to provide a highly reliable cooking device that can avoid adverse effects on the life of electrical equipment without causing off-state fluctuations.

[ll of invention! E required]

This invention focuses on the fact that continuous output control is possible in a cooker that supplies power to a magnetron using an inverter circuit. A means is provided to automatically set the .

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a commercial AC power supply, and an inverter circuit 2 is connected to this power supply 1. This inverter circuit 2
A primary winding 5a of a high voltage transformer 5 is connected to the output end of a rectifier circuit consisting of a diode bridge 3 and a smoothing capacitor 4.
A series resonant circuit consisting of a capacitor 6 and a capacitor 6 is connected to the capacitor 6, and to the capacitor 6 switching elements such as NPN type transistors between reflector and emitter and damper diodes 8 are connected in 11 columns. That is, the output voltage of the rectifier circuit is converted into alternating current power at a predetermined frequency (several tens of KIIZ) by exciting a series L-oscillator circuit by turning on and off the transistor 7. The anode and cathode of the magnetron 13 are connected to the secondary winding 5b of the high voltage transformer 5 via a half-wave voltage doubler rectifier circuit consisting of a high voltage capacitor 10 and high voltage diodes 11 and 12. Further, the anode of the magnetron 13 is grounded. Further, a predetermined heater voltage is applied to the heater (cathode) of the magnetron.

On the other hand, 20 is a microcomputer which is a main control section, and this microcomputer 20 includes an operation section 21.
, a timer counter 22 for counting cooking time, a temperature sensor 23 for detecting food temperature, an output setting circuit 24, and the like are connected. This output setting circuit 24 emits an output setting signal of a voltage level corresponding to an output setting command from the microcomputer 30. Further, 25 is a pulse width modulation (PWM) circuit that outputs a pulse signal of a predetermined width by comparing the "sawtooth wave" signal supplied from the oscillation circuit 26 and the output setting signal from the output setting circuit 24. . A base drive circuit 27 drives the transistor 7 on and off in accordance with the output pulse of the pulse width modulation circuit 24.

Next, the operation of the above configuration will be explained with reference to FIG.

The power source 1 is turned on, and the cooking time and heating output are set using the operation unit 21, and the cooking is started.

Then, the microcomputer 20 sends an output setting signal of a voltage level corresponding to the set heating output to the output setting circuit 24.
This turns on and off the transistor 7 with an on and off duty corresponding to the set heating output. Then, the series resonant circuit consisting of the primary winding 5a of the high-voltage transformer 5 and the capacitor 6 is excited (resonates), and the secondary winding 5b of the high-voltage transformer 5 receives a predetermined frequency (
AC power (and voltage) is generated. This AC power is subjected to half-wave voltage doubler rectification and applied to the magnetron 13. Therefore, the magnetron 13 is activated, and the food in the heating chamber is dielectrically heated by the high frequency radio waves emitted from the magnetron 13.

In this case, if the set heating output is high, the width of the pulse signal output from the pulse width modulation circuit 25 is long, and the transistor 7 is driven on and off with a large on and off duty. As a result, the effective value of the anode current flowing through the magnetron 13 increases, and the magnetron 1
3's oscillation output increases. Furthermore, if the set heating output is low, the width of the pulse signal output from the pulse width variation 17!1 circuit 25 is short, and the transistor 7 is turned on and off with small on and off duties. As a result, the effective value of the anode current flowing through the magnetron 13 becomes smaller, and the oscillation output of the magnetron 13 becomes lower.

During cooking, the microcomputer 20 counts the elapsed time from the start of cooking with a timer counter 22, and when the elapsed time reaches the set cooking time, it stops turning on and off the transistor according to the set heating output. urge In other words, cooking is essentially completed. Then, at the same time as this cooking is completed, a small on/off duty is set to drive the transistor 7 on and off to obtain a predetermined low output and cook one item of food in the heating chamber. During this heat-retaining cooking, the input power either decreases as shown in FIG. 2 or is maintained at a constant level without any on/off fluctuations.

In this way, as soon as cooking is finished, the low-output keep-warm cooking is automatically set, so even if the food is left in the heating chamber without the user noticing that cooking has finished, the food will not cool down. There is no need to put it away. In addition, since the low output during thermal cooking is obtained by the inverter circuit 2, the input power does not fluctuate between on and off unlike conventional energization on and off, thus preventing surge current (rush current). This makes it possible to avoid negative effects on the lifespan of electrical equipment.

In the above embodiment, when one preset cooking time has elapsed, the actual cooking ends and the mode of keeping warm cooking starts. However, when the temperature sensor 23 detects that the temperature of the food reaches the preset temperature, It is also possible to complete the actual cooking and move on to the heat-retaining cooking. In addition, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without changing the gist.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to shift to low-output heat-retaining cooking as soon as cooking is completed, and furthermore, during the heat-retaining cooking, the lifespan of electrical equipment can be extended without causing input power on/off fluctuations. It is possible to provide a highly reliable device that can avoid adverse effects on the environment.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a control circuit in an embodiment of the present invention, and FIG. 2 is a diagram for explaining the operation of the embodiment. 2... Inverter circuit, 7... NPN transistor (switching element), 13... Magnetron, 2
0...Microcomputer (main control unit).

Claims (1)

[Claims] Equipped with an inverter circuit that rectifies AC power supply voltage, converts it into AC power of a predetermined frequency, and applies it to the magnetron.
What is claimed is: 1. A cooking device capable of continuous output control, characterized in that the cooking device is provided with means for automatically setting heat-retaining cooking at low output when cooking is completed.