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High-frequency heater

A high-frequency heating and equipment technology, applied in microwave heating, electric/magnetic/electromagnetic heating, electric heating devices, etc., can solve problems such as unstable operation, and achieve the effect of reducing high-order harmonic distortion

Active Publication Date: 2010-10-06
PANASONIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0023] It should be noted that when the switching frequency is very close to the resonance frequency "f0", causing unstable operation such as abnormal resonance

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0077] figure 1 A circuit diagram of the magnetron drive power circuit of the high-frequency heating device according to the first embodiment of the present invention is shown. In the inverter circuit, by using the DC power supply 1, the leakage transformer 2, the first semiconductor switching element 3, the first capacitor (snubber capacitor) 5, the second capacitor (resonant capacitor) 6, the third capacitor (smoothing capacitor) 7. The second semiconductor switching element 4, the driving circuit 14, the full-wave power double rectifier circuit 11 and the magnetron 12 constitute its main circuit. Due to the arrangement of the above-mentioned main circuit other than the drive circuit 14 and Picture 11 Those are the same, so its explanation is omitted.

[0078] In the driving circuit 14 for driving the first and second semiconductor switching elements 3 and 4, first, the frequency modulation signal generating circuit 15 forms a frequency modulation waveform by using a waveform ...

Embodiment 2

[0088] Figure 5 It is indicated that the frequency modulation signal generating circuit adopted in the magnetron-driving inverter circuit of the second embodiment of the present invention is different from the above-mentioned first embodiment in that a resistor 155 is newly provided. According to this embodiment, by separating the frequency from V2 when the voltage is lower than or equal to the fixed voltage V2, the second limiting function can be realized by gradually increasing the sensitivity to limit the change of the frequency modulation waveform.

[0089] Image 6 The frequency modulation waveform of the second embodiment is shown. Similar to the first embodiment, the waveform change in the vicinity of the lowest frequency becomes smooth, making it possible to suppress sudden changes in frequency.

Embodiment 3

[0091] Figure 7 It is indicated that the frequency modulation signal generating circuit adopted in the third embodiment of the present invention is different from the above-mentioned first embodiment in that a transistor 159 is provided in the first limiting circuit.

[0092] According to this third embodiment, the resistance value change of the PN junction indicated by the voltage versus current characteristic is adopted by the resistor 159 as the first limiting function.

[0093] When the potential difference of the PN junction increases, the resistance value of the PN junction decreases. As a result, since the potential of the divided voltage waveform obtained by rectifying the commercial power supply voltage becomes lower than the voltage V1 and separated from the voltage B1, the sensitivity of the first limiting function increases, so that the voltage lower than or equal to V1 is smoothly changed Waveform.

[0094] In addition, although multiple sets of first restriction funct...

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Abstract

A high-frequency heating power supply for driving a magnetron such as a microwave oven and a frequency modulating method for reducing the power supply harmonic distortion of high orders caused at the phases of about 0 and 180 degrees at which the instantaneous voltage of the commercial power supply is the lowest are provided. When the high-frequency heating power supply gives a signal for drivingfirst and second semiconductor switching elements (3, 4),the high-frequency heating power supply suppresses the power supply harmonic distortion of high order by smoothly varying the switching frequency near the boundary between the period during which the lowest switching frequency is limited to f1 at the phases of about 0 and 180 degrees at which the instantaneous voltage of the commercial power supply is the lowest and the period during which the limitation is canceled, that is, by eliminating a sharp variation of the switching frequency.

Description

Technical field [0001] The present invention relates to a high-frequency heating device using a magnetron, such as a microwave oven. More specifically, the present invention relates to a control system for suppressing high-order harmonic distortion of a commercial power supply current supplied to a magnetron drive power supply. Background technique [0002] Since the conventional power supply installed on the high-frequency heating device is heavy and bulky, it is necessary to make the power supply compact and lightweight. For this reason, various active methods capable of constructing such a low-cost, compact, and light-weight switching power supply have been proposed in various fields. In a high-frequency heating apparatus for cooking food by using microwaves generated from a magnetron, a compact and light-weight power source for driving the magnetron, which can be realized by a switching-type inverter circuit, is required. [0003] More specifically, among these switching-type...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H05B6/68
CPCH05B6/685Y02B40/143Y02B40/00
Inventor 末永治雄守屋英明酒井伸一城川信夫木下学
Owner PANASONIC CORP
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