EP2190261A1 - Alimentation haute tension au magnétron dotée d'une reconnaissance de fréquence - Google Patents

Alimentation haute tension au magnétron dotée d'une reconnaissance de fréquence Download PDF

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Publication number
EP2190261A1
EP2190261A1 EP08291102A EP08291102A EP2190261A1 EP 2190261 A1 EP2190261 A1 EP 2190261A1 EP 08291102 A EP08291102 A EP 08291102A EP 08291102 A EP08291102 A EP 08291102A EP 2190261 A1 EP2190261 A1 EP 2190261A1
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EP
European Patent Office
Prior art keywords
capacitor
high voltage
voltage
frequency
power supply
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EP08291102A
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German (de)
English (en)
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EP2190261B1 (fr
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.)
Topinox SARL
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Topinox SARL
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Publication date
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Priority to EP20080291102 priority Critical patent/EP2190261B1/fr
Publication of EP2190261A1 publication Critical patent/EP2190261A1/fr
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Publication of EP2190261B1 publication Critical patent/EP2190261B1/fr
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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
    • H05B6/64—Heating using microwaves
    • H05B6/66—Circuits
    • H05B6/68—Circuits for monitoring or control

Definitions

  • the present invention relates to a high voltage power supply for a magnetron for producing microwaves in a cooking appliance and a cooking appliance with such a high voltage power supply. Furthermore, it comprises a method for generating a high voltage in a cooking appliance.
  • magnetrons are commonly used to generate microwaves.
  • Magnetrons typically consist of a vacuum tube, in the center of which a hot cathode is arranged, which is surrounded by an annular anode arrangement. Electrons emerge from the hot cathode and are accelerated radially outward toward the array of devices. At the same time, the electrons are deflected by a magnetic field, which is aligned parallel to the hot cathode, on helical paths. The circulating electrons induce in cavities, which are arranged radially outside the electron path, alternating fields in the microwave frequency range, of which a part can be removed via a waveguide and introduced into the cooking chamber of the cooking appliance.
  • a high voltage supply is needed, which is suitable to keep the hot cathode at a sufficiently negative potential.
  • the high voltage supply is formed by a switching power supply with active components.
  • switching power supplies are relatively expensive and complicated.
  • a cost-effective alternative is a traditional high-voltage power supply with a conventional primary, secondary and iron core transformer and a downstream rectifier.
  • a voltage doubling and rectifying circuit which comprises a diode and a capacitor and is suitable for rectifying and doubling the secondary voltage induced in the secondary winding.
  • Such a "classic" high voltage power supply without active components is relatively inexpensive to implement.
  • it is extremely robust and reliable, so that it rarely comes to failures and related maintenance operations.
  • the capacitance of the capacitor of the voltage doubler and rectification circuit must be matched to the frequency of the AC current in the transformer for efficient rectification and voltage doubling.
  • the AC frequency in the transformer usually corresponds to the line frequency.
  • the grid frequency is not the same in all countries. For example, while the grid in Europe has an AC frequency of 50 Hz, the grid frequency in North America is 60 Hz. If the secondary voltage in both grid frequency ranges is to be rectified and coupled with the same circuit with the simple structure described above, the results are not satisfactory , Therefore, a cooking appliance with such a simple rectification and doubling circuit is not readily usable globally.
  • the invention has for its object to provide a high voltage power supply for a magnetron for the production of microwaves in a cooking appliance, which is simple and robust and allows global use of the cooking appliance.
  • This object is achieved by a high voltage power supply according to claim 1 and a cooking appliance according to claim 11. Furthermore, it is achieved by a method for generating a high voltage in a cooking appliance according to claim 12.
  • the high voltage power supply of the invention comprises a voltage multiplying and rectifying circuit comprising a diode and a capacitor arrangement and capable of rectifying and multiplying, in particular doubling, the secondary voltage induced in the secondary winding.
  • capacitor arrangement indicates that the capacitance required for the multiplication and rectification circuit can be provided by one or more capacitors.
  • the high voltage power supply includes a frequency detection circuit capable of detecting the AC frequency of the transformer and means for adjusting the capacitance of the capacitor array in response to the detected frequency.
  • the frequency detection circuit may control the means for adjusting the capacitance of the capacitor arrangement as a function of the detected frequency, so that the capacity is set automatically.
  • the frequency detection circuit could also be connected to output means capable of indicating the detected frequency or related information or instruction.
  • the means for adjusting the capacity could be manually operable, for example by a simple user based on the displayed information or instruction.
  • the means for adjusting the capacitance of the capacitor arrangement can be optimally adapted to the AC frequency of the transformer, so in particular the mains frequency. This can be done during commissioning or even during operation, the capacity setting.
  • this has the advantage that he can use the same high voltage power supply for cooking appliances regardless of their future installation location or its associated mains voltage.
  • this has the advantage that he can use the cooking appliance after purchase at any location. For example, if the purchaser of the cooking appliance operates restaurants or canteens in countries with different network frequencies, he can easily replace the cooking appliance between these countries without the need for further modifications.
  • the frequency detection circuit always automatically detects the frequency of the transformer and either the means for adjusting the capacity itself controls or at least indicates in a suitable manner that the capacitance of the capacitor arrangement is set manually in dependence on the detected frequency.
  • the invention allows the high-voltage power supply to be used regardless of location regardless of the relatively simple, classical structure.
  • theistsvervielfachungs- and rectification circuit comprises at least two capacitors, of which at least one is selectively connectable to the circuit.
  • the means for adjusting the capacitance comprise a switch, with which it is possible to switch over between a first capacitor and a second capacitor, such that the voltage multiplier and rectification circuit, in a first switching state of the switch, involves the first capacitor and does not include the second capacitor, and in a second state, including the second capacitor and not including the first capacitor.
  • the two capacitors are effectively replaced by operating the switch.
  • the first capacitor can be optimized, for example, for operation at 50 Hz and the second capacitor for operation at 60 Hz.
  • the means for adjusting the capacitance may include a switch with which a second capacitor can be connected to a first capacitor, such that the voltage multiplier and rectification circuit in a first switching state of the switch involves the first capacitor and does not involve the second capacitor, and in a second switching state, incorporating the first and second capacitors.
  • the voltage multiplier and rectification circuit in the first switch position assumes a configuration in which only the first capacitor is provided, and in the second switch position takes a configuration in which both the first and the second capacitor are provided.
  • the first and the second capacitor in the second switching state of the switch could be connected in parallel, so that the effective capacitance of the capacitor arrangement in the second switching state of the switch corresponds to the sum of the capacitances of the individual capacitors.
  • the first capacitor and the second capacitor could also be connected in series in the second switching state of the switch. Then the effective capacitance of the capacitor arrangement corresponds to the sum of the reciprocal values of the capacitances of the individual capacitors, ie the capacitance of the capacitor arrangement decreases in the second Total switching state off. In this way too, the capacitance of the capacitor arrangement can therefore be changed, ie adjusted.
  • the frequency detection circuit comprises a frequency detector, in particular a digital frequency counter.
  • the frequency counter has an input stage which is connected to an inductance, which in turn is inductively coupled to the primary or secondary winding of the transformer and is suitable, the amplitude of the voltage of the primary or secondary winding to 24 V or less, preferably to transform 15 V or less, and more preferably 5 V or less. In this way, the frequency of the transformer can be easily tapped and simultaneously transformed into a low voltage, which can be evaluated with a simple digital frequency counter.
  • a high voltage power supply 10 for a magnetron 12 for generating microwaves in a cooking appliance is shown schematically.
  • the magnetron 12 comprises a high-voltage hot cathode 14, which in Fig. 1 is shown only schematically. It is understood that the reference numeral 12 only the circuit connection of the magnetron shown, but not its structure is reproduced.
  • the high voltage supply 10 comprises a transformer 16 having a primary winding 18, a secondary winding 20 and an iron core 22. It should be noted that the illustration of the primary and secondary windings 18, 20 in FIG Fig. 1 is only schematic and in particular no conclusions on the number of turns allows. In fact, the primary voltage is highly transformed by the transformer 16, so that a high voltage is induced in the secondary winding 20.
  • the secondary winding 20 is connected to a voltage doubler and rectification circuit 24 which includes a diode 26 and, depending on the position of a switch 28, includes a first capacitor 30 or a second capacitor 32.
  • the first and the second capacitor 30 and 32 have different capacities, which are designed for different mains frequencies, namely 50 and 60 Hz.
  • the voltage doubler and rectification circuit consists of the first capacitor 30 and the diode 26, and in the - in Fig. 1 shown second switching position consists of the second capacitor 32 and the diode 26th
  • the high-voltage supply 10 comprises a frequency detection circuit 34, which is also coupled via an inductance 36 to the secondary winding 20 and picks up the frequency of the transformer 16 in the form of a low voltage.
  • the frequency detection circuit 34 comprises an input stage (not shown) to which the low voltage tapped by the inductance 36 is applied, and a digital counter (not shown) with which the frequency of the tapped signal can be determined in a manner known per se.
  • the frequency detection circuit 34 is connected to the switch 28 via a control line 38, via which it can control the switch 28 such that it switches to the first or second circuit position.
  • a further secondary winding 40 is provided, in which a heating current for heating the hot cathode 14 is inducible.
  • the function of the high voltage power supply 10 will be explained below.
  • a high voltage is induced in the secondary winding 20.
  • the frequency of the high voltage is detected by the frequency detection circuit 34.
  • the frequency detection circuit 34 drives the switch 28 to switch to a first or a second switching position in which the first capacitor 30 and the second capacitor 32 are included in the voltage doubler and rectifier circuit 24, respectively.
  • the voltage doubler and rectification circuit the secondary voltage is rectified and doubled in known manner and applied to the thermionic cathode 14 of the magnetron 12.
  • the frequency detection circuit 24 detects the frequency in the transformer 16 and configures the voltage doubler and rectification circuit 24 by selecting the proper position of the switch 28 such that the appropriate capacitor 30 or 32 is included in the circuit 24.
  • one and the same high voltage supply 10 can be used independently of the present mains voltage frequency.
  • the cooking appliance which uses the shown high voltage power supply for the magnetron 12, can be used globally without having to be specially configured for the place of use.
  • the circuit 24 may comprise an ever-present capacitor, to which a further one can be connected depending on the mains frequency in order to adapt the effective capacitance of the capacitor arrangement to the line frequency accordingly.
  • a voltage multiplying circuit could be provided which increases the secondary voltage by more than a factor of 2 and has a corresponding number of diodes and capacitors arranged in a cascade.
  • a frequency detection circuit in a modified embodiment could indicate to the operator that he should manually operate a corresponding switch to suitably adjust the capacitance of the capacitor array.
  • Essential to the invention here is that the monitoring of the frequency is done automatically and that the adjustment of the capacity of the capacitor assembly without the involvement of technically trained maintenance personnel happens, namely either completely automatically or by a simple operation by the user instructed by the cooking appliance.
  • the low cost, robust and simple construction of the high voltage power supply 10 with conventional transformer, capacitor and diode can be modified so that it is independent of the grid frequency and thus globally applicable.
  • the low circuit complexity of complexity and cost is far below that of a switching power supply with active components, the use of which can be avoided in this way.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)
EP20080291102 2008-11-21 2008-11-21 Alimentation haute tension au magnétron dotée d'une reconnaissance de fréquence Ceased EP2190261B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP20080291102 EP2190261B1 (fr) 2008-11-21 2008-11-21 Alimentation haute tension au magnétron dotée d'une reconnaissance de fréquence

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP20080291102 EP2190261B1 (fr) 2008-11-21 2008-11-21 Alimentation haute tension au magnétron dotée d'une reconnaissance de fréquence

Publications (2)

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EP2190261A1 true EP2190261A1 (fr) 2010-05-26
EP2190261B1 EP2190261B1 (fr) 2012-01-11

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EP20080291102 Ceased EP2190261B1 (fr) 2008-11-21 2008-11-21 Alimentation haute tension au magnétron dotée d'une reconnaissance de fréquence

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0301805A1 (fr) * 1987-07-27 1989-02-01 Matsushita Electric Industrial Co., Ltd. Appareil de chauffage à hautes fréquences
DE4116871A1 (de) * 1990-05-25 1991-11-28 Sawafuji Electric Co Ltd Ac/dc-mikrowellenofen
WO2000030407A1 (fr) * 1998-11-13 2000-05-25 Samsung Electronics Co., Ltd. Four a micro-ondes du type a courant alternatif/courant continu (c.a./c.c.)

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0301805A1 (fr) * 1987-07-27 1989-02-01 Matsushita Electric Industrial Co., Ltd. Appareil de chauffage à hautes fréquences
DE4116871A1 (de) * 1990-05-25 1991-11-28 Sawafuji Electric Co Ltd Ac/dc-mikrowellenofen
WO2000030407A1 (fr) * 1998-11-13 2000-05-25 Samsung Electronics Co., Ltd. Four a micro-ondes du type a courant alternatif/courant continu (c.a./c.c.)

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Publication number Publication date
EP2190261B1 (fr) 2012-01-11

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