High Frequency Heating Apparatus

• US 20080047959A1
• Filed: 10/17/2005
• Published: 02/28/2008
• Est. Priority Date: 10/18/2004
• Status: Abandoned Application

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Moriya, Hideaki, Sakai, Shinichi, Suenaga, Haruo, Shirokawa, Nobuo, Kinoshita, Manabu
• Application Number:
  US11/577,341
• Publication Number:
  US 20080047959A1
• Time in Patent Office: Days
• US Class Current: 219/745
• CPC Class Codes: H05B 6/685 the measurements being made at the low voltage side of the circuit
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers

Abstract

The invention relates to a high frequency heating apparatus that drives a magnetron such as a microwave, and provides a frequency modulation method of preventing harmonic current occurring due to a high frequency switching operation.

When a driving signal is transmitted in order to drive a first semiconductor switching element (3) and a second semiconductor switching element (4), an inverter operating frequency in the every phase of a commercial power supply is provided as a frequency difference (inclination) of the phase range from 0° to 90° using a triangular wave-forming circuit in an oscillation circuit (16). A modulation waveform for a frequency modulation control is formed, configuring an upper limit clamp, a lower limit clamp, a lower limit value corresponding to the lowest frequency in a frequency modulation-forming circuit (15) on the basis of a commercial power rectifying voltage-dividing waveform after rectification. By combining these optimally, it is possible to prevent the harmonic current from occurring while forming the frequency modulation waveform handling several non-uniformities such as constants of major inverter circuit components or a power supply (Vcc) of a driving control IC unit (14).

Claims

1. A high frequency heating apparatus which drives a magnetron by allowing a semiconductor switching element to perform a high frequency switching operation using a commercial power supply,

wherein the frequency of the high frequency switching operation is variable so that the frequency ascends in the phase range of the power supply from 0°

to 90° and

from 180°

to 270° and

descends in the phase range of the power supply from 90°

to 180° and

from 270°

to 360°

; and

wherein the difference in the operating frequencies between the ascending and descending periods is large.

2. The high frequency heating apparatus according to claim 1, wherein the frequency of the high frequency switching operation is easily variable by varying a parallel combined resistance value of series resistors.

3. The high frequency heating apparatus according to claim 1, wherein the variation in the frequency of the high frequency switching operation can be represented as the shape pf a frequency modulation waveform;

and

wherein the frequency modulation waveform is formed on the basis of a rectification waveform of the commercial power supply and has an upper limit clamp.

4. The high frequency heating apparatus according to claim 1, wherein the variation in the frequency of the high frequency switching operation can be represented as the shape of the frequency modulation waveform;

and

wherein the frequency modulation waveform is formed on the basis of a rectification waveform of the commercial power supply and has a lower limit clamp.

5. The high frequency heating apparatus according to claim 1, wherein the variation in the frequency of the high frequency switching operation can be represented as the shape of the frequency modulation waveform;

and

wherein the frequency modulation waveform is formed on the basis of the rectification waveform of the commercial power supply and has a lower limit value corresponding to the restriction of the lowest frequency.

6. The high frequency heating apparatus according to claim 1, wherein the variation in the frequency of the high frequency switching operation can be represented as the shape of the frequency modulation waveform;

and

wherein the frequency modulation waveform is formed on the basis of the rectification waveform of the commercial power supply and has an upper limit clamp, a lower limit clamp, a lower limit value corresponding to the restriction of the lowest frequency.

7. The high frequency heating apparatus according to claim 6, wherein the difference between the upper limit clamp and the lower limit clamp is as small as possible and the shape of the frequency modulation waveform is nearly flat.

8. The high frequency heating apparatus according to claim 3, wherein the upper limit clamp is uniquely determined as a predetermined fixed value independent from a variation in voltage values of the commercial power supply.

9. The high frequency heating apparatus according to claim 3, wherein the upper limit clamp is uniquely determined as a value that undergoes a small variation through a resistor or a diode from a predetermined value independent from a variation in voltage values of the commercial power supply.

10. The high frequency heating apparatus according to claim 3, wherein the upper limit clamp is determined as a reference value that varies depending on a variation in voltage values of the commercial power supply.

11. The high frequency heating apparatus according to claim 3, wherein the upper limit clamp is determined as a value that undergoes a small variation through a resistor or a diode from a predetermined value that varies depending on a variation in voltage values of the commercial power supply.

12. The high frequency heating apparatus according to claim 4, wherein the lower limit clamp is uniquely determined as a fixed value independent from a variation in voltage values of the commercial power supply.

13. The high frequency heating apparatus according to claim 4, wherein the lower limit clamp is uniquely determined as a value that undergoes a small variation through a resistor or a diode from a predetermined value independent from a variation in voltage values of the commercial power supply.

14. The high frequency heating apparatus according to claim 4, wherein the lower limit clamp is determined as a reference value that varies depending on a variation in voltage values of the commercial power supply.

15. The high frequency heating apparatus according to claim 4, wherein the lower limit clamp is determined as a value that undergoes a small variation through a resistor or a diode from a predetermined value varied depending on a variation in voltage values of the commercial power supply.

16. The high frequency heating apparatus according to claim 5, wherein the lower limit value corresponding to the restriction of the lowest frequency is uniquely determined as a predetermined fixed value independent from a variation in voltage values of the commercial power supply.

17. The high frequency heating apparatus according to claim 5, wherein the lower limit value corresponding to the restriction of the lowest frequency is uniquely determined as a predetermined fixed value that varies depending on a variation in voltage values of the commercial power supply.