EP0269417A1 - Induktionsheizkreise für Kochgeräte - Google Patents

Induktionsheizkreise für Kochgeräte Download PDF

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Publication number
EP0269417A1
EP0269417A1 EP19870310361 EP87310361A EP0269417A1 EP 0269417 A1 EP0269417 A1 EP 0269417A1 EP 19870310361 EP19870310361 EP 19870310361 EP 87310361 A EP87310361 A EP 87310361A EP 0269417 A1 EP0269417 A1 EP 0269417A1
Authority
EP
European Patent Office
Prior art keywords
thyristor
circuit
switching device
induction heating
discharge
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19870310361
Other languages
English (en)
French (fr)
Inventor
Robert Ian Bullough
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Creda Ltd
Original Assignee
Creda Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Creda Ltd filed Critical Creda Ltd
Publication of EP0269417A1 publication Critical patent/EP0269417A1/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/06—Control, e.g. of temperature, of power

Definitions

  • This invention relates to induction heating circuits for cooking appliances.
  • Such circuits may comprise a rectifier for converting A.C. mains supply to direct current which is then converted by an inverter to an alternating supply at a suitable frequency usually in the range of from 20-35 kHz. That supply energises a pan heating coil which induces currents in a suitable utensil placed over the coil thereby heating the utensil and its contents.
  • the inverter is switched on and off at intervals determined by the heat output required from the pan heating coil. During off periods, the inverter resonates at a frequency deteramined by the inductance of the pan heating coil and other circuit parameters including a circuit capacitor.
  • the inverter may comprise a gate turn-off thyristor and when this is switched on, a current that increases in ramped fashion flows through the pan heating coil. When the current reaches a specified level, the thyristor is gated off and the circuit resonates. Ideally, the thyristor is switched on when the voltage across the capacitor is zero but that value is not reached under light load conditions, i.e. low power output from the pan heating coil. Consequently, the next time the thyristor is switched on, it will be forward biassed by the residual capacitor voltage and an uncontrolled, potentially destructive current flows momentarily through the thyristor.
  • an induction heating circuit for a cooking appliance includes an inverter for powering an induction heating coil and a resonating capacitor at values determined by a first semi-­conductor switching device and in which a further semi-­conductor switching device is provided to permit discharge of the resonating capacitor before the initiation of power input to the induction heating coil.
  • the discharge may be effected via a resistor in series connection with the first switching device, and in which the initiation of power input is delayed by the second switching device until discharge is complete.
  • the discharge may be effected by the second switching device and is completed before the initiation of power input to the heating coil.
  • the amplitude of the current flowing during discharge of the capacitor may be controlled by resistive means.
  • the first switching means may be a gate turn off thyristor which is in series connection with a parallel connection combination of a further thyristor and resistor.
  • the first switching device may be a gate turn off thyristor which is in parallel connection with a series connected combination of resistor and further gate turn off thyristor.
  • the pan heating coil is shown as inductance L2 and this is powered from source 1, 2 under the control of a gate turn off thyristor VT1.
  • the resonant capacitor for the heating coil L2 is capacitor CR.
  • diode D1 Connected in parallel across capacitor CR is diode D1 which provides a conductive path for resonant currents during non-conductive periods of thyristor VT1.
  • Figs. 2-6 illustate the operation of the circuit of Fig. 1.
  • Fig. 2 is a waveform of the turn-on pulse applied to the gate of thyristor VT1. At turn-on any residual voltage present on CR is discharged through RS which limits the current flow to a safe value until thyristor VTS is turned on after a delay of about 3 ⁇ sec following the initiation of the turn-on pulse. Turn-on of thyristor VTS allows current flow in ramped fashion through both VTS and VT1 as shown in the waveforms of Figs. 5 and 6.
  • thyristor VT1 At the end of the current ramp, thyristor VT1 is turned off. That deprives thyristor VTS of current hence commutating the thyristor.
  • Fig. 3 shows the waveform of the discharge current through resistor RS and thus current also flows through thyristor VT1 as shown by the waveform of Fig. 6.
  • thyristor VTS must be of a current rating similar to that of thyristor VT1 whilst the voltage rating depends upon the maximum initial capacitor voltage.
  • thyristor VTS must commutate within the minimum time for which thyristor VT1 is non-conducting.
  • Co-pending Patent Application No.86.28098 provides further detail of the induction heating system including means for controlling the conduction of thyristor VT1.
  • Control pulses for thyristor VTS can be derived from the drive circuit referred to in the co-pending Patent Application.
  • the snubber circuit described above with reference to Fig. 1 requires the use of a thyristor VTS with a fast recovery time and which operates at a relatively low power level. Such devices tend to be expensive.
  • FIG. 7 An alternative circuit not needing such a thyristor is shown in Fig. 7.
  • Thyristor VTS is turned on in advance of thyristor VT1 as can be seen from a comparison of waveforms of Figs. 8 and 9. Turning on thyristor VTS allows capacitor CR to discharge through resistor RS as is indicated by the waveform shown in Fig. 10. Discharge is subtantially completed before thyristor VT1 is turned on.
  • thyristor VTS As thyristor VT1 is turned on, thyristor VTS is turned off and the load current through the pan heating coil transfers to thyristor VT1.
  • thyristor VTS does not carry the main load current but it must support the peak resonant voltage at capacitor CR and thus is of the same voltage rating as thyristor VT1.
  • circuit arrangements described above with reference to Figs. 1 and 7 permit a substantial reduction in the dissipation of the thyristor VT1 and this allows the power output of the pan heating coil to be reduced to comparatively low levels by using the current sensing techniques described in Patent Application No. (Case 218) without recourse to the mark/space control also referred to in that Application.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Inverter Devices (AREA)
EP19870310361 1986-11-25 1987-11-24 Induktionsheizkreise für Kochgeräte Withdrawn EP0269417A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8628102A GB2198296B (en) 1986-11-25 1986-11-25 Improvements in or relating to induction heating circuits for cooking appliances
GB8628102 1986-11-25

Publications (1)

Publication Number Publication Date
EP0269417A1 true EP0269417A1 (de) 1988-06-01

Family

ID=10607867

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19870310361 Withdrawn EP0269417A1 (de) 1986-11-25 1987-11-24 Induktionsheizkreise für Kochgeräte

Country Status (2)

Country Link
EP (1) EP0269417A1 (de)
GB (1) GB2198296B (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007042318A1 (de) * 2005-10-14 2007-04-19 E.G.O. Elektro-Gerätebau GmbH Verfahren zum betrieb einer induktionsheizeinrichtung

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2684175B1 (es) * 2017-03-30 2019-07-12 Bsh Electrodomesticos Espana Sa Dispositivo de aparato domestico y procedimiento para la puesta en funcionamiento de un dispositivo de aparato domestico

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3781503A (en) * 1971-11-19 1973-12-25 Gen Electric Solid state induction cooking appliances and circuits
US4010342A (en) * 1974-10-29 1977-03-01 Roper Corporation Induction cooking appliance having improved protection circuits
DE2504827B2 (de) * 1974-02-05 1977-11-24 Matsushita Electric Industrial Co, Ltd, Kadoma, Osaka (Japan) Induktions-heizgeraet fuer kochzwecke
EP0054445A1 (de) * 1980-12-05 1982-06-23 Etablissements Eugene Scholtes Elektronische Induktionsheizvorrichtung

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3781503A (en) * 1971-11-19 1973-12-25 Gen Electric Solid state induction cooking appliances and circuits
DE2504827B2 (de) * 1974-02-05 1977-11-24 Matsushita Electric Industrial Co, Ltd, Kadoma, Osaka (Japan) Induktions-heizgeraet fuer kochzwecke
US4010342A (en) * 1974-10-29 1977-03-01 Roper Corporation Induction cooking appliance having improved protection circuits
EP0054445A1 (de) * 1980-12-05 1982-06-23 Etablissements Eugene Scholtes Elektronische Induktionsheizvorrichtung

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007042318A1 (de) * 2005-10-14 2007-04-19 E.G.O. Elektro-Gerätebau GmbH Verfahren zum betrieb einer induktionsheizeinrichtung
CN101326857B (zh) * 2005-10-14 2011-11-23 E.G.O.电气设备制造股份有限公司 用来操作感应加热设备的方法
US8415594B2 (en) 2005-10-14 2013-04-09 E.G.O. Elektro-Geraetebau Gmbh Method for operating an induction heating device

Also Published As

Publication number Publication date
GB2198296A (en) 1988-06-08
GB2198296B (en) 1990-08-08
GB8628102D0 (en) 1986-12-31

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Inventor name: BULLOUGH, ROBERT IAN