Variable-frequency inverter microwave oven and method for controlling the same

• US 6,884,977 B2
• Filed: 07/31/2003
• Issued: 04/26/2005
• Est. Priority Date: 01/27/2003
• Status: Expired due to Fees

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Shin, Dong Myung, Han, Sung Jin
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US10/630,659
• Publication Number:
  US 20040144776A1
• Time in Patent Office: 635 Days
• Field of Search: 219715-721, 219/702, 363/37, 363/41, 363/49, 363/97, 363/98, 363/74
• US Class Current: 219/715
• CPC Class Codes: H05B 6/66 Circuits
• 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

A variable-frequency inverter microwave oven and a method for controlling the same. The inverter microwave oven comprises a magnetron for generating electromagnetic waves, a direct current (DC) voltage generator for rectifying and smoothing a commercial alternating current (AC) voltage, which is an inverter drive voltage, to generate a DC voltage, and a switching device for performing a switching operation based on the DC voltage from the DC voltage generator to generate an AC voltage for the driving of the magnetron. The switching device includes a plurality of switches turned on/off in response to the DC voltage from the DC voltage generator. The microwave oven further comprises a variable-frequency controller for varying a switching frequency of the switching device according to the level of the DC voltage from the DC voltage generator to maintain the AC voltage from the switching device at a constant level, and a magnetron drive voltage generator for converting the AC voltage from the switching device into a high-power DC voltage and transferring the converted DC voltage to the magnetron to drive it. The inverter operation is improved compared with a conventional one and a magnetron drive duration is lengthened, thereby improving heating efficiency and operational reliability of the microwave oven.

Claims

1. A variable-frequency inverter microwave ovens comprising:

a magnetron that generates electromagnetic waves;

a direct current (DC) voltage generator that rectifies and smooths a commercial alternating current (AC) voltage to generate a DC voltage, the commercial AC voltage being an inverter drive voltage;

a switcher that performs a switching operation based on said DC voltage from said DC voltage generator to generate an AC voltage that drives said magnetron, said switcher including a plurality of switches that are turned on/off in response to said DC voltage from said DC voltage generator;

variable-frequency controller that controls a switching frequency of said switcher according to a level of said DC voltage from said DC voltage generator to maintain said AC voltage from said switcher at a constant level; and

magnetron drive voltage generator that converts said AC voltage from said switcher into a high-power DC voltage and transfers said converted DC voltage to said magnetron to drive said magnetron, said variable-frequency controller comprising;

a DC voltage input node that receives said generated DC voltage;

a current source that supplies a switching current for the switching operation of said switcher, based on said DC voltage inputted to said DC voltage input node; and

a frequency generator that generates a predetermined frequency in accordance with an amount of said switching current supplied from said current source and outputs said predetermined frequency to said switcher.

2. The variable-frequency inverter microwave oven of claim 1, further comprising a drive current sensor that senses a current amount of the commercial AC voltage.

3. The variable-frequency inverter microwave oven of claim 2, further comprising a microcomputer that controls an output power of the microwave oven in response to a user'"'"'s cooking command and a current amount sensed by said drive current sensor.

4. The variable-frequency inverter microwave oven of claim 1, further comprising a protector that turns off said switcher to prevent said switches from being damaged when a level of said DC voltage from said DC voltage generator is at least equal to a predetermined threshold voltage level.

5. The variable-frequency inverter microwave oven of claim 1, wherein said variable-frequency controller further includes a transistor having a base connected to said current source and a collector connected to said frequency generator.

6. The variable-frequency inverter microwave oven of claim 1, wherein said frequency generator is adapted to lower said switching frequency of said switcher when the amount of said switching current supplied from said current source is below a predetermined reference value, and raise said switching frequency of said switcher when said switching current amount is above said predetermined reference value.

7. The variable-frequency inverter microwave oven of claim 1, wherein said frequency generator comprises an integrated circuit.

8. A variable-frequency inverter microwave oven, comprising:

a switcher having a plurality of switches that are turned on/off to perform a switching operation to generate an AC voltage;

a variable-frequency controller that controls a switching frequency of the switcher to maintain the AC voltage from the switcher at a constant level; and

a magnetron drive voltage generator that converts said AC voltage from said switcher into a high-power DC voltage to drive a magnetron of the microwave oven, said variable-frequency controller comprising;

a DC voltage input node that receives a DC voltage;

a current source that supplies a switching current for the switching operation of said switcher, based on the DC voltage inputted to said DC voltage input node; and

a frequency generator that generates a predetermined frequency in accordance with an amount of said switching current supplied from said current source and outputs said predetermined frequency to said switcher.

9. The variable-frequency inverter microwave oven of claim 8, wherein said switcher performs the switching operation in accordance with a level of a generated DC voltage.

10. The variable-frequency inverter microwave oven of claim 8, further comprising a protector that turns off said switcher to protect said switches from damage when a DC voltage level is at least equal to a predetermined threshold voltage level.

11. The variable-frequency inverter microwave oven claim 8, wherein said frequency generator is adapted to lower said switching frequency of said switcher when the amount of said switching current supplied from said current source is below a predetermined reference value, and to raise said switching frequency of said switcher when said switching current amount is above said predetermined reference value.

12. The variable-frequency inverter microwave oven of claim 8, wherein said frequency generator comprises an integrated circuit.

13. A variable-frequency inverter for a microwave oven, comprising:

a switcher having a plurality of switches that are turned on/off to perform a switching operation to generate an AC voltage; and

a variable-frequency controller that controls a switching frequency of the switcher, said variable-frequency controller comprising;

a DC voltage input node that receives a DC voltage;

a current source that supplies a switching current for the switching operation of said switcher, based on the DC voltage inputted to said DC voltage input node; and

a frequency generator that generates a predetermined frequency in accordance with an amount of said switching current supplied from said current source and outputs said predetermined frequency to said switcher.

14. The variable-frequency inverter microwave oven claim 13, wherein said frequency generator is adapted to lower said switching frequency of said switcher when the amount of said switching current supplied from said current source is below a predetermined reference value, and to raise said switching frequency of said switcher when said switching current amount is above said predetermined reference value.

15. The variable-frequency inverter microwave oven of claim 13, further comprising a protector that turns off said switcher to protect said switches from damage when a DC voltage level is at least equal to a predetermined threshold voltage level.