Induction heating apparatus

Patent metadata

Field	Value
Publication number	US-9326329-B2
Application number	US-201113393483-A
Country	US
Kind code	B2
Filing date	Jan 19, 2011
Priority date	Jan 20, 2010
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

It is an object of the present invention to provide an induction heating apparatus that can enable a plurality of heating coil to perform heating by sharing a inverter having semiconductor switches in use, thereby adjusting a power without increasing losses of the semiconductor switches so much with respect to the respective heating coils, the present invention being configured such that the inverter alternately outputs drive signals respectively having each of two operating frequencies to the plurality of heating coils in every predetermined operation lapse of time and the plurality of heating coils are respectively connected to capacitance circuits in the inverter to have the different frequency characteristics.

First claim

The invention claimed is:

1. An induction heating apparatus comprising:
a smoothing circuit to which a rectified power from an AC power supply is input;
an inverter in which the smoothed power is input to a set of semiconductor switch circuits from the smoothing circuit, and which is configured to output a periodic drive signal having a first operating frequency during a first time period, and a second operating frequency during a second time period;
a plurality of heating coils which are supplied with the drive signals from the inverter, wherein each of the plurality of heating coils is connected to one of a plurality of capacitance circuits so that each heating coil has a resonant frequency that matches one of the two operating frequencies; and
a control portion for controlling the operating frequencies and the operation period of time to drive the semiconductor switch circuit, wherein the control portion is configured to select the first operating frequency and the second operating frequency to simultaneously set a first average power delivered to a first heating coil to a first power value, and a second average power delivered to a second heating coil to a second power value, to thereby heat a first load disposed on the first heating coil with the first average power and to heat a second load disposed on the second heating coil with the second average power.

2. The induction heating apparatus according to claim 1 , wherein the set of the semiconductor switch circuits is formed by a series circuit including two semiconductor switches, and by alternating turn-on and turn-off operations of the two semiconductor switches, the smoothed power from the smoothing circuit is supplied to the plurality of heating coils connected to a connecting point of the two semiconductor switches connected in series.

3. The induction heating apparatus according to claim 2 , wherein the plurality of heating coils are respectively connected in series with a plurality of capacitance circuits provided in the inverter, and a plurality of resonant circuits including the plurality of heating coils and the plurality of capacitance circuits have different resonant frequency values in frequency characteristics, respectively.

4. The induction heating apparatus according to claim 3 , wherein each of the series circuits that include the plurality of heating coils and the plurality of capacitance circuits is connected between the connecting point of the two semiconductor switches connected in series and one output terminal of the smoothing circuit.

5. The induction heating apparatus according to claim 3 , wherein each of the plurality of capacitance circuits includes a plurality of capacitance elements and connected in parallel with the smoothing circuit, and each of the plurality of heating coils is respectively connected between nodes between the capacitance elements of the capacitance circuits and the connecting point of the two semiconductor switches connected in series.

6. The induction heating apparatus according to claim 4 , further comprising a switching portion fitted to each of the series circuits that include the plurality of heating coils and the plurality of capacitance circuits for enabling each of the plurality of heating coils to be disconnected from or connected to the inverter.

7. The induction heating apparatus according to claim 5 , wherein a switching portion is fitted to each of the plurality of heating coils so as to enable each of the plurality of heating coils to be disconnected from or connected to the inverter.

8. The induction heating apparatus according to claim 3 , wherein the first operating frequency is higher than the resonant frequencies of the plurality of resonant circuits and the second operating frequency is set in a middle range of the resonant frequencies of the plurality of resonant circuits.

9. The induction heating apparatus according to claim 3 , wherein at least one of the at least one of the first and second operating frequencies is different than the resonant frequency at the time of no load where no to-be-heated object is placed.

10. The induction heating apparatus according to claim 3 , wherein at least one of the first and second operating frequencies is set in a range other than the frequency range that denotes at least ½ of a maximum input power in the frequency characteristic at the time of no load where no to-be-heated object is placed.

11. The induction heating apparatus according to claim 3 , wherein an antiparallel diode is connected with each of the two semiconductor switch, so that in alternate turn-on/-off operations of the two semiconductor switches, each of those semiconductor switches is turned on at timing when a current starts to flow through this diode.

12. The induction heating apparatus according to claim 3 , wherein there is at least 20 kHz between the respective resonant frequencies in the frequency characteristics of the plurality of resonant circuits.

13. The induction heating apparatus according to claim 3 , wherein the control portion is configured to control the operating frequencies and operation periods of time of the drive signals output from the inverter, based on an input current from the AC power supply and an input power to the heating coils.

14. The induction heating apparatus according to claim 3 , wherein the control portion is configured to determine the operation periods of time of the drive signals output from the inverter based on the input current from the AC power supply and the input power to the heating coils and then control a duty ratio of the semiconductor switches to thereby control powers to be supplied to the heating coils.

15. The induction heating apparatus according to claim 3 , wherein the plurality of heating coils have external shapes having different coil diameters, so that the resonant frequency of the resonant circuit including the heating coil having the smaller diameter is set higher than that of the resonant circuit including the heating coil having the larger diameter.

Assignees

• Kitaizumi Takeshi
• Kurose Yoichi
• Kataoka Akira
• Panasonic Ip Man Co Ltd

Inventors

• Kitaizumi Takeshi
• Kurose Yoichi
• Kataoka Akira

Classifications

• H05B6/065 Primary

  using coordinated control of multiple induction coils · CPC title