EP2582201B1 - Induction heating device - Google Patents

Description

The invention is based on an induction heating device according to the preamble of claim 1.

Induction heaters are known which include an inductor powered by an inverter operated by a rectifier.

The document EP1978786 discloses an induction heater of the prior art.

The object of the invention is in particular to provide a generic device with improved properties in terms of increased efficiency. The object is achieved by the features of claim 1, while advantageous embodiments and modifications of the invention can be taken from the dependent claims.

The invention is based on an induction heating device, in particular an induction hob device, with at least one induction heating element and at least one heating frequency unit which is provided, at least in one operating state, to supply at least one induction heating element with high-frequency alternating current.

It is proposed that the induction heating device has at least one boost unit, which is intended to convert an input voltage into an output voltage which is at least 1%, in particular at least 30%, advantageously at least 60%, preferably at least 90% greater as the input voltage. An "induction heating element" is to be understood, in particular, as a wound electrical conductor, preferably in the form of a circular disk or an oval with an elongate shape, through which high-frequency alternating current flows in at least one operating state. The induction heating element is preferably provided to convert electrical energy into an alternating magnetic field, which is provided in a metallic, preferably at least partially ferromagnetic, heating means, in particular cooking utensils, eddy currents and / or remagnetization effects cause heat to be generated. In particular, in at least one operating state, in particular an operating state without a near heating medium, the induction heating element has an inductance value between 0.1 μH and 10 mH, in particular between 0.5 μH and 5 mH, preferably between 1 μH and 1 mH. A "heating frequency unit" should in particular be understood to mean an electrical unit which generates an oscillating electrical signal, preferably with a frequency of at least 1 kHz, in particular of at least 10 kHz, advantageously of at least 20 kHz, and in particular of not more than 100 kHz for an induction heating element , In particular, the heating frequency unit is provided to provide a, required by the induction heating, maximum electrical power of at least 1000 W, in particular at least 2000 W, advantageously at least 3000 W and preferably at least 3500 W. The heating frequency unit preferably has at least one switching element which is connected in series with it at least during a heating operation of the induction heating element. The heating frequency unit preferably has at least one diode which is connected in parallel with the at least one switching element. By "intended" is intended to be understood in particular specially designed and / or equipped. A "boost unit" should in particular be understood to mean an electronic unit which has at least one boost inductance and at least one switching element, the boost inductance and the switching element being connected in series between input contacts of the input voltage and an output voltage being able to be removed across the switching element. Preferably, the switching element is connected in parallel with at least one smoothing capacitor, advantageously in series with a backflow preventer, in order to smooth the output voltage which can be taken off across the smoothing capacitor. Alternatively, the boost unit can also be designed as a cascade circuit. A "switching element" is to be understood in particular to mean an electronic element which is intended to produce and / or to separate an electrically conductive connection between two points. Preferably, the switching element has at least one control contact, via which it can be switched. In particular, the switching element is advantageously designed as a semiconductor switching element, in particular as a transistor, as a bipolar transistor with preferably insulated gate electrode (IGBT). A "boost inductance" is intended in particular to mean an electrical inductance, advantageously at least one electrical coil, with an inductance value of at least 10 μH, in particular at least 50 μH, preferably at least 80 μH, preferably at least 100 μH, and / or at most 10 H, in particular at most 1 H, advantageously at most 300 mH, preferably at most 100 mH. The boost inductance is preferably provided to store electrical energy in a closed state of the switching element of the boost unit and to discharge it again in an open state of the switching element. In particular, a boost inductance is different from a filter inductance intended to filter electrical noise. A "smoothing capacity" is to be understood in particular as meaning an electrical capacitance, in particular at least one electrical capacitor, which has a capacitance value of at least 100 nF, in particular at least 200 nF, advantageously at least 500 nF, preferably at least 1 μF, and / or at most 100 μF. in particular at most 500 μf, advantageously at most 300 μF, preferably at most 10 μF. A "backflow preventer" should in particular be understood to mean an electronic element, in particular a diode, and / or a switching element which is preferably precisely controlled and which is intended to suppress a current flow at specific times and / or in certain directions. In particular, the Rückflussvermeider the boost unit is provided to prevent discharge of the smoothing capacitor via the switching element of the boost unit in at least one operating state. An "input voltage" is understood in particular to mean a voltage of an energy source, preferably a DC voltage, in particular a pulsating DC voltage and / or a rectified voltage of a phase of a domestic power connection. An "output voltage" should preferably be understood to mean a DC voltage, in particular a pulsating DC voltage, which is preferably provided to supply the heating frequency unit. Under that an output voltage is "greater" than an input voltage, should be understood in particular that a time average of the output voltage is greater than a time average of the input voltage. Due to an increased voltage, a current flow can advantageously be reduced, in particular with the same power, whereby a power loss can be reduced and thus an efficiency can be increased. In particular, a high heating power can be made available to an operator for a longer time before throttling of the heating power is carried out due to excessive heat development and / or insufficient cooling. Further consequential effects can be cost reduction, lifetime extension, performance improvement and so on.

Furthermore, it is proposed that the heating frequency unit and the at least one boost unit are formed at least partially in one piece. By the fact that two units are formed "partially in one piece" should be understood in particular that the units have at least one, in particular at least two, advantageously at least three common elements which are part, especially functionally important component of both units. In particular, at least one switching element of the heating frequency unit is part of the boost unit. In particular, at least one Rückflussvermeider the boost unit is part of the heating frequency unit. In particular, the inductance value of the boost inductance is tuned to optimally boost at a frequency between 20 kHz and 100 kHz. In particular, components can be saved, which in turn electrical losses can be reduced.

It is also proposed that the induction heating device has at least one rectifier unit, which is in particular provided to rectify an AC voltage, in particular an AC line voltage, and to provide the boost unit as an input voltage. A "rectifier unit" should be understood to mean, in particular, a unit which has at least two, in particular at least four, backflow preventer, which are preferably designed as diodes. Preferably, the Rückflussvermeider are arranged in a bridge circuit. In particular, the rectifier unit has at least one smoothing capacitor, which is provided to at least partially store a rectified voltage. In particular, at least one of the reflux eliminators is arranged electrically between the boost coil and the switching element of the boost unit. In particular, the switching element of the boost unit is connected in parallel with at least part of the rectifier unit. In particular, high efficiency can be achieved.

It is advantageously proposed that the rectifier unit and the boost unit are at least partially formed in one piece. In particular, at least one smoothing capacitor of the boost unit is part of the rectifier unit. In particular, at least one Rückflussvermeider the rectifier unit is part of the boost unit. In particular, components can be saved, which in turn electrical losses can be reduced.

Furthermore, it is proposed that the rectifier unit and the heating frequency unit are formed at least partially in one piece. In particular, at least one Rückflussvermeider the rectifier unit is part of the heating frequency unit. In particular, components can be saved, which in turn electrical losses can be reduced.

Furthermore, it is proposed that the heating frequency unit has at least one switching element which is connected in parallel with at least part of the rectifier unit, in particular a reflux preventer. In particular, an efficiency can be increased.

It is also proposed that the heating frequency unit is designed as a bridge inverter with at least two switching elements. The two switching elements are preferably series-connected, bidirectional unipolar switches, which are formed in particular by a transistor and a parallel-connected diode. As a result, a high-frequency power supply of the induction heating unit can be provided. A voltage tap of the heating frequency unit is arranged in particular at a common contact point, a contact of the bridge branch, two bidirectional unipolar switch. Preferably, the bridge inverter is designed as a half-bridge. In particular, the induction heating element is arranged in a bridge branch between the series-connected switching elements and two resonant capacitors connected in series. Alternatively, an embodiment is conceivable as a full bridge, wherein the induction heating is arranged together with a resonant capacitance in a bridge branch between the two series-connected switching elements and another two series-connected switching elements. In particular, a resonance capacitance has a capacitance value between 50 nF and 100 μF, in particular between 150 nF and 60 μF, advantageously between 0.3 μF and 30 μF, and preferably between 0.5 μF and 10 μF. In particular, a capacitance value of the resonance capacitance is dependent on an inductance value of the induction heating element. In particular, an efficient and / or easily controllable heating frequency unit can be provided.

It is further proposed that a bridge branch of the bridge inverter directly with a contact of a power supply, in particular a phase of a AC power supply is connected. A "direct contact" is to be understood in particular as an electrically conductive, in particular metallic, connection which can be traversed by direct current irrespective of the direction. In particular, an increased effectiveness can be achieved.

It is advantageously proposed that at least one, in particular exactly one, of the switching elements of the heating frequency unit, a damping capacity is connected in parallel. A "damping capacity" is to be understood in particular as meaning a capacitor, in particular at least one capacitor, which is provided to avoid voltage peaks when the switching element is switched on and / or switched off. In particular, a damping capacity differs from an intrinsic capacitance of a diode. In particular, the damping capacity has a capacitance value between 1 nF and 1000 nF, in particular between 3 nF and 600 nF, advantageously between 6 nF and 300 nF, preferably between 10 nF and 100 nF. In particular, at least one switching element of the heating frequency unit differs from a switching element with a parallel-connected damping capacity. In particular, an increased effectiveness can be achieved. In particular, it can be achieved that a voltage change across the switching elements of the heating frequency unit is reduced and thus a voltage-free switching, that is a switching under ZVS condition, is facilitated, whereby switching losses can be avoided.

Further advantages emerge from the following description of the drawing. In the drawings, embodiments of the invention are shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

• Fig. 1 ein erfindungsgemäßes Kochfeld in einer schematischen Ansicht,
• Fig. 2 ein Schaltbild einer Induktionsheizvorrichtung die kein Teil der Erfindung ist und
• Fig. 3 ein Schaltbild einer erfindungsgemäßen Induktionsheizvorrichtung mit weniger benötigten Bauteilen.

Show it:

• Fig. 1 an inventive hob in a schematic view,
• Fig. 2 a circuit diagram of an induction heater which is not part of the invention and
• Fig. 3 a diagram of an induction heater according to the invention with less required components.

FIG. 1 shows a cooking appliance designed as a domestic appliance 10 with four formed as induction hob devices induction heaters 12, 14, 16, 18. The induction heaters 12, 14, 16, 18 are formed as cooking zones.

FIG. 2 shows a simple embodiment of the induction heating 12 which is not part of the invention. The induction heating device 12 has an induction heating element 20 and a heating frequency unit 22. Furthermore, the induction heating device 12 has a boost unit 24, which is intended to convert an input voltage into an output voltage that is greater than the input voltage. Furthermore, the induction heating device 12 has a rectifier unit 26. The rectifier unit 26 has four reflux inhibitors 40, 42, 44, 46 in the form of diodes, which are connected as bridge rectifiers. The rectifier unit 26 is intended to rectify a mains AC voltage which is applied to contacts of a voltage supply 28 and to store them partially in a smoothing capacitor 48. The AC voltage source is designed as a phase of a multi-phase house connection. The boost unit 24 receives as input voltage the pulsating DC voltage which is generated by the rectifier unit 26 and applied across the smoothing capacitor 48. The boost unit 24 has a boost inductance 50 and a switching element 52. By periodically opening and closing the switching element 52 at a high frequency, the boost inductance 50 generates an increased voltage, which is conducted via a backflow preventer 54 of the boost unit 24 into a smoothing capacitor 56. About the smoothing capacitor 56, an output voltage can be tapped, which is twice as large as the input voltage. The induction heating element 20 is designed as a circular inductor. The Heizfrequenzeinheit 22 is formed as a bridge inverter with two switching elements 30, 32, each having a parallel-connected Rückflussvermeider 34, 36, which is designed as a diode. The heating frequency unit 22 is designed as a half-bridge circuit. The heating frequency unit 22 is provided to receive a pulsating DC voltage, which is applied across the smoothing capacitor 56 of the boost unit 24, and to convert it into a high-frequency AC voltage. Furthermore, the Half-bridge circuit two resonance capacitances 38, 39 on. One of the switching elements 32, a damping capacitor 33 is connected in parallel.

Furthermore, embodiments are conceivable in which more than one heating frequency unit 22 are connected to the smoothing capacitor 56 of the boost unit 24. For example, all four induction heaters 12, 14, 16, 18 may share a rectifier unit 26 and / or a boost unit 24, and / or the induction heaters 14, 16, 18 may be analogous to the induction heater 12. Furthermore, embodiments are conceivable in which a heating frequency unit is designed as a single switching element, which is connected in series with a parallel circuit of an induction heating element and a resonance capacitor. Furthermore, the smoothing capacitance 48 of the rectifier unit 26 can be dispensed with. Embodiments are also conceivable in which the rectifier unit 26 is dispensed with and a DC voltage source is used directly for an input voltage of the boost unit 24.

In the FIG. 3 a further embodiment of the invention is shown. The following descriptions are essentially limited to the differences between the embodiments, with respect to the same components, features and functions on the description of the other embodiment, in particular the FIGS. 1 and 2 , can be referenced. To distinguish the embodiments of the FIG. 3 the letter a is added to the reference signs. With respect to identically designated components, in particular with regard to components with the same reference numerals, can in principle also to the drawings and / or the description of the embodiment of FIGS. 1 and 2 to get expelled.

In FIG. 3 a specialized embodiment of an induction heating device 12a according to the invention is shown. Induction heater 12a includes an induction heating element 20a, a heating frequency unit 22a, and a boost unit 24a arranged to convert an input voltage to an output voltage that is greater than the input voltage. The heating frequency unit 22a is designed as a bridge inverter with two switching elements 30a, 32a. Each of the switching elements 30a, 32a is connected in parallel with a reflux eliminator 34a, 36a designed as a diode. The heating frequency unit 22a is designed as a half-bridge circuit. The boost unit 24a has two switching elements 52a, 52a 'and a boost inductance 50a. Furthermore, the boost inductance 50a has a Smoothing capacity 56a and two Rückflussvermeider 54a, 54a 'on. The Rückflussvermeider 54a, 54a 'are formed as diodes, each of which one of the switching elements 30a, 32a is connected in parallel. The Heizfrequenzeinheit 22 a and the boost unit 24 a are partially formed in one piece. The Rückflussvermeider 54a, 54a 'of the boost unit 24a are as switching elements 30a, 32a and Rückflussvermeider 34a, 36a components of the heating frequency unit 22a. Furthermore, the switching elements 30a, 32a of the heating frequency unit 22a as switching elements 52a, 52a 'are components of the boost unit 24a. Furthermore, the induction heating device 12a has a rectifier unit 26a. The rectifier unit 26a is formed by four reflux mixers 40a, 42a, 44a, 46a and a smoothing capacitor 48a. The Rückflussvermeider 40a, 42a, 44a, 46a are arranged substantially in bridge circuit. The return flow removers 40a, 42a are in this case arranged electrically between the switching elements 52a and the boost inductance 50a of the boost unit 24a. The rectifier unit 26a and the boost unit 24a are partially formed in one piece. The Rückflussvermeider 54a, 54a 'of the boost unit 24a are as Rückflussvermeider 44a, 46a components of the rectifier unit 26a. Furthermore, the smoothing capacity 48a of the rectifier unit 26a is part of the boost unit 24a. The rectifier unit 26a and the heating frequency unit 22a are formed partially in one piece. The return flow removers 34a, 36a of the heating frequency unit 22a are, as backflow preventer 44a, 46a, components of the rectifier unit 26a. The switching elements 30a, 32a of the heating frequency unit 22a are connected in parallel with reflux mixers 44a, 46a of the rectifier unit 26a. A bridge branch of the heating frequency unit 22a designed as a bridge inverter is connected directly to a contact of a voltage supply 28a. A single one of the switching elements 32a of the heating frequency unit 22a is connected in parallel with a damping capacitance 33a. If damping capacitances 33a were connected in parallel to both switching elements 30a, 32a, an interference voltage would build up, which led to a lower efficiency.

In an operating state in which the switching elements 30a, 32a, 52a, 52a 'are opened, the backflow preventer 40a, 42a, 44a, 46a, 54a, 54a', 34a, 36a behave like a regular rectifier, wherein an AC voltage of the voltage supply 28a is rectified and buffered in the smoothing capacitance 48a, 56a, which is arranged in a bridge branch of the rectifier. A connection via the induction heating element 20a and a resonance capacitance 38a or 39a is irrelevant, since these resonant circuits have a resonant frequency in the kHz range between 10 kHz and 50 kHz, which is far greater than a mains frequency of the power supply In operation of the heating frequency unit 22a, the switching elements 30a, 32a, 52a, 52a 'are periodically opened and closed at a high frequency between 20 kHz and 100 kHz to generate a high-frequency alternating current for the induction heating element 20a , In this case, a maximum of one of the switching elements 30a, 32a, 52a, 52a 'is opened simultaneously in order to avoid a short circuit of the smoothing capacitor 48a, 56a and to ensure correct operation of the induction heating element 20a. In the case of a positive half cycle of the AC voltage from the voltage supply 28a, a short circuit is generated periodically via the switching element 30a, 52a and the return flow suppressor 40a, which leads to an energy build-up in the boost inductance 50a. When the switching element 30a, 52a is opened, the boost inductance 50a generates an induction voltage which, via the backflow preventer 40a and the backflow preventer 46a or the later opened switching element 32a, charges the smoothing capacitor 48a, 56a with a voltage that is greater than a current amount of the input voltage , Further, in a closed state of the switching element 30a, 52a ', the resonance capacitance 38a across the induction heating element 20a is discharged and the resonance capacitance 39a is charged via the induction heating element 20a by the smoothing capacitance 48a, 56a. When the resonance capacitance 38a is discharged, the switching element 30a, 52a 'is opened without voltage. An inductance of the induction heating element 20a maintains a current flow through the induction heating element 20a by further charging the resonance capacity 39a via the reflux preventer 36a, 46a, 54a '. If current flows via the reflux preventer 36a, 46a, 54a ', the switching element 32a can be closed. The flow direction of a current through the induction heating element 20a reverses and the resonance capacity 39a is discharged via the induction heating element 20a, while the resonance capacity 38a is charged via the induction heating element 20a by the smoothing capacity 48a, 56a. This process continues periodically. In the case of a negative half cycle of the AC voltage from the voltage supply 28a, a short circuit is periodically generated via the switching element 32a and the return flow observer 42a, which leads to an energy build-up in the boost inductance 50a. When the switching element 32a, 52a 'is opened, the boost inductance 50a generates an induction voltage which charges the smoothing capacitor 48a, 56a with a voltage via the reflux preventer 42a and the reflux preventer 34a, 44a, 54a or the later opened switching element 30a, 52a' is greater than a current amount of input voltage.

10

Hausgerät

12

Induktionsheizvorrichtung

14

Induktionsheizvorrichtung

16

Induktionsheizvorrichtung

18

Induktionsheizvorrichtung

20

Induktionsheizelement

22

Heizfrequenzeinheit

24

Boosteinheit

26

Gleichrichtereinheit

28

Spannungsversorgung

30

Schaltelement

32

Schaltelement

33

Dämpfungskapazität

34

Rückflussvermeider

36

Rückflussvermeider

38

Resonanzkapazität

39

Resonanzkapazität

40

Rückflussvermeider

42

Rückflussvermeider

44

Rückflussvermeider

46

Rückflussvermeider

48

Glättungskapazität

50

Boostinduktivität

52

Schaltelement

54

Rückflussvermeider

56

Glättungskapazität

reference numeral

10

household appliance

12

induction heating

14

induction heating

16

induction heating

18

induction heating

20

induction heating

22

Heizfrequenzeinheit

24

boost unit

26

Rectifier unit

28

power supply

30

switching element

32

switching element

33

damping capacity

34

Rückflussvermeider

36

Rückflussvermeider

38

resonant capacitance

39

resonant capacitance

40

Rückflussvermeider

42

Rückflussvermeider

44

Rückflussvermeider

46

Rückflussvermeider

48

smoothing capacitor

50

Boostinduktivität

52

switching element

54

Rückflussvermeider

56

smoothing capacitor

Claims (8)

1. Induction heating apparatus, in particular induction hob apparatus, with at least one induction heating element (20a), with at least one heat frequency unit (22a), with at least one rectifier unit (26a) and with at least one boost unit (24a), which is provided to convert an input voltage into an output voltage, which is larger than the input voltage, characterised in that the rectifier unit (26a) and the heat frequency unit (22a) are at least partially embodied in one piece, wherein the rectifier unit (26a) and the heat frequency unit (22a) have at least one common element, which is a component part of both units.
2. Induction heating apparatus according to claim 1, characterised in that the heat frequency unit (22a) and the boost unit (24a) are at least partially embodied in one piece.
3. Induction heating apparatus according to one of the preceding claims, characterised in that the rectifier unit (26a) and the boost unit (24a) are at least partially embodied in one piece.
4. Induction heating apparatus according to one of the preceding claims, characterised in that the heat frequency unit (22a) has at least one switch element (30a, 32a), which is connected in parallel to at least one part of the rectifier unit (26a).
5. Induction heating apparatus according to one of the preceding claims, characterised in that the heat frequency unit (22a) is embodied as a bridge inverter with at least two switch elements (30a, 32a).
6. Induction heating apparatus according to claim 5, characterised in that a bridge branch of the bridge inverter is directly connected to a contact of a power supply (28a).
7. Induction heating apparatus at least according to claim 5, characterised in that an attenuating capacitor (33a) is connected in parallel to at least one of the switch elements (32a).
8. Domestic appliance with at least one induction heating apparatus (12, 14, 16, 18, 12a) according to one of the preceding claims.

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