WO2013084115A1

WO2013084115A1 - Induction heating device

Info

Publication number: WO2013084115A1
Application number: PCT/IB2012/056816
Authority: WO
Inventors: Daniel Anton Falcon; Carlos CALVO MESTRE; Sergio Llorente Gil; Daniel Palacios Tomas; Diego Puyal Puente; Hector Sarnago Andia
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH
Priority date: 2011-12-07
Filing date: 2012-11-29
Publication date: 2013-06-13
Also published as: EP2789208B1; EP2789208A1

Abstract

The invention relates to an induction heating device (12), in particular an induction cooking hob device, comprising at least two switching elements (42, 44, 46, 48) which are connected in parallel in at least one operating mode and which are provided for generating a high-frequency alternating current for powering an induction heating element (20, 22, 24, 26) and comprising at least one control unit (14). The aim of the invention is an improved heating behavior. This is achieved in that the control unit (14) is provided in order to control at least two of the at least two switching elements (42, 44, 46, 48) with different activity parameters in at least the first operating mode.

Description

induction heating

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

Induction hob devices are known having inverters connected in parallel to an inductor. The object of the invention is in particular to provide a generic device with improved heating properties. 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 a

Induction hob device, with at least two switching elements, which are connected in parallel and provided in at least one operating mode, a

To generate high-frequency alternating current for supplying an induction heating, and with at least one control unit.

It is proposed that the control unit be provided to actuate at least two of the at least two switching elements with different activity parameters, at least in the operating mode. A "switching element" is to be understood as meaning, in particular, an electrical component which is intended to produce and / or to separate at least one electrical connection between at least two power contacts of the switching element

Semiconductor switching element, preferably as a transistor, in particular as an IGBT formed. Preferably, the switching element has at least one control contact, which is provided only to an adjustment of a switching state of

Switching element, in particular by a control unit to allow. It is to be understood in particular from the fact that two switching elements are "connected in parallel" that poles of the same name, in particular at least identical power contacts, of the switching elements are directly connected to one another In particular, an electrical connection can be understood which, at least in an operating state with a current flow of alternating current via the connection with a frequency between 1 kHz and 100 kHz has an impedance which is smaller in magnitude than 10 V / A, in particular smaller than 1 V / A, preferably less than 0, 1 V / A, and whose amount, in particular over a frequency range of 1 kHz to 100 kHz by a maximum of 100%, in particular a maximum of 40%, preferably at most 10%, preferably at most 3%, fluctuates ,

An "induction heating element" is to be understood in particular as meaning a heating element having at least one induction heating line, which is intended to pass through

Induction effects, in particular induction of electric current and / or

Magnetization effects, in a, preferably ferromagnetic, in particular metallic, heating means, in particular in a cooking utensil, in an oven wall and / or in a radiator, which is arranged in an oven to cause heating of the heating means. In particular, the induction heating element is provided to transmit in at least one operating mode in which the induction heating is connected to a supply electronics, a power of at least 100 W, in particular at least 500 W, advantageously at least 1000 W, preferably at least 2000 W, in particular electrical energy in electromagnetic

To convert field energy, which is finally converted into heat in a suitable heating medium. An "induction heating line" is to be understood as meaning, in particular, an electrical line which is intended to carry an electric current which is intended to induce induction effects in a suitable heating means , Preferably at least substantially in the form of a circular disc, alternatively in the form of an oval or a rectangle formed.

In particular, the induction heating, in particular with a coupled heating means, an inductance of at least 0, 1 μΤ, in particular at least 0.3 μΤ, advantageously at least 1 μΤ, on. In particular, the induction heating line,

in particular without a coupled heating means, an inductance of not more than 100 mT, in particular not more than 10 mT, advantageously not more than 1 mT. Preferably, the induction heating is intended, at least in an operating state of high-frequency alternating current, in particular an alternating current having a frequency of at least 1 kHz, in particular at least 3 kHz, advantageously at least 10 kHz, preferably at least 20 kHz, in particular at most 100 kHz, in particular with a current intensity of at least 0.5 A, in particular at least 1 A, advantageously at least 3 A, preferably at least 10 A, to flow through. A "control unit" is to be understood as meaning, in particular, an electronic unit which preferably has, in a control and / or regulating unit, an induction heating device

Household appliance is at least partially integrated. Preferably, the control unit is at least provided to control and / or regulate the switching elements.

The control unit preferably comprises a computing unit and, in particular in addition to the computing unit, a memory unit with a control and / or regulating program stored therein, which is intended to be executed by the computing unit.

In particular, at least one switch-on time, one duration and / or one switch-off time of a control, in particular a phase and / or a duty cycle of a regular, preferably at least substantially periodic, control, be understood. In particular, the induction heating device has at least one

Sensor arrangement, which is intended to provide operating values, in whose

Dependence the control unit determines the activity parameters.

Due to the configuration according to the invention, in particular a heating behavior adapted to operating values can be achieved. In particular, a duration that can be heated with maximum heating power before an emergency regulation due to overheating of the switching elements takes place can be extended.

Furthermore, it is proposed that the at least two switching elements are connected in parallel independently of the operating state. Alternatively, it is conceivable that the

Switching elements are provided, for example, to a boost mode, to be connected in parallel via a further, in particular electromechanical, switching element, in particular a relay. By constantly parallel switching elements can in particular an increased efficiency due to reduced line losses in the

Switching elements, even at low power levels, are made possible. It is also proposed that the control unit is provided, at least in the operating mode at least two of the switching elements with different

To operate duty cycles. Under a duty cycle is intended in particular the

Ratio of on-time to total time to be understood. A duty cycle of 100% corresponds to a constantly established connection, while a duty cycle of 0% corresponds to a constantly disconnected connection. It can in particular a

RMS value can be adjusted by flowing through the different switching elements currents, which in particular line losses of different

Switching elements can be changed.

Furthermore, it is proposed that the control unit be provided to activate the at least two switching elements at least substantially simultaneously, at least in the operating mode. Activate under "essentially simultaneously"

in particular, be understood that a distance of switch-on of the

Control currents for the different switching elements at most 1 s, preferably at most 0, 1 s, preferably at most 10 ns, is. Preferably, in this case, a sampling rate for the correspondingly switched off switching element is selected in such a way that a current through the switching element is zero before the correspondingly different one

Switching element is turned off. In particular, high efficiency can be achieved. In particular, a power loss due to switching losses on the

Switching element, which is turned off earlier, be avoided. Alternatively, it is conceivable that the control unit is provided to switch off the switching elements at least substantially simultaneously, whereby an allocation of the switching losses is achieved, but line losses are redistributed.

It is also proposed that the induction heater be at least one

Current sensor arrangement which is intended to determine by the at least two switching elements flowing currents. In particular, it is conceivable that each of the switching elements, in particular exactly one, current sensor is connected in series. A "current sensor" is intended in particular to mean a sensor, in particular a

Ammeter understood, which measures at least the AC component, in particular by inductive means. Alternatively, it is conceivable that at least one current sensor is provided which measures the total current flowing through all the switching elements. In particular, it may be an accurate determination of a performance in the Induction heating element is implemented to be performed. In particular, a loss performance determination of the line losses can be carried out for each of the switching elements. In particular, the control unit is provided to determine the activity parameters of the at least two switching elements as a function of values of the current sensor arrangement. In particular, the control unit is provided to equalize rms values of the currents through different ones of the at least two switching elements, by adjusting the sampling rate of a switching element with a high rms value

Low effective value switching element lowers. In particular, the control unit is provided to adjust the activity parameters when a minimum effective value of the at least two switching elements is less than 100%, in particular less than 80%, advantageously none is 60%, preferably less than 40% of a maximum

RMS value of the at least two switching elements. In particular, the control unit is provided to adjust the activity parameters when a minimum effective value of the at least two switching elements is at most 20%; in particular at most 40%, advantageously at most 60%, preferably at most 80%, of a maximum effective value of the at least two switching elements. In particular, it is possible to achieve a distribution of occurring power losses of the switching elements which arise as a result of line losses.

Furthermore, it is proposed that the induction heater at least one

Temperature sensor arrangement which is intended to determine temperatures of the at least two switching elements. In particular, the

Temperature sensor arrangement on at least two temperature sensors, which are arranged on at least one, in particular divided by the switching elements, the heat sink, wherein the control unit is provided, based on measured values of these

Temperature sensors to determine temperatures of the switching elements. Alternatively, it is conceivable that at least one, in particular a plurality, preferably each, of the switching elements has an integrated temperature sensor. In particular, a temperature monitoring of the switching elements can be achieved.

In particular, the control unit is provided to adjust the activity parameters of the at least two switching elements as a function of values of the To determine temperature sensor arrangement. In particular, the control unit is provided to adjust the activity parameters when a temperature of at least one of the switching elements exceeds a temperature of 160 ° C, in particular of 150 ° C, advantageously of 140 ° C. In particular, the control unit is provided to the

Adjusting activity parameters when a minimum of the temperatures of the at least two switching elements by at least 5 K, in particular by at least 10 K, advantageously by at least 15 K, deviates from a maximum of the temperatures of the at least two switching elements. In particular, regulation of the activity parameters as a function of values of the temperature sensor arrangement takes precedence over regulation of the activity parameters as a function of values of the current sensor arrangement.

Further advantages emerge from the following description of the drawing. In the drawing, an embodiment of the invention is 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.

1 shows a hob according to the invention in a schematic view

from above,

2 shows an induction heating device according to the invention in one

schematic diagram,

3 shows a first operating state of a first output operating mode, FIG. 4 shows a first operating mode according to the invention in response to

the first operating state,

5 shows a second operating state of the first output operating mode, FIG. 6 shows a second operating mode according to the invention in response to

the second operating state and

Fig. 7 shows a temperature and power curve of an inventive

Induction heater at high power operation. FIG. 1 shows a domestic appliance 10 designed as an induction hob, with a domestic appliance 10

Induction hob device trained induction heater 12. The

Induction heater 12 has four induction heating elements 20, 22, 24, 26. The induction heating elements 20, 22, 24, 26 are arranged under a hob plate 18.

FIG. 2 shows an embodiment of the induction heating device 12 in an exemplary circuit of the induction heating element 20. The induction heating device 12 has a voltage source 30. Furthermore, the induction heater 12 has four

Switching elements 42, 44, 46, 48 on. The switching elements 42, 44, and 46, 48 are connected in parallel to each other in pairs, independently of an operating mode. The

Switching elements 42, 44, 46, 48 are part of an inverter 40. The switching elements 42, 44, 46, 48 are designed as IGBTs. The inverter 40 and the switching elements 42, 44, 46, 48 are provided to generate a high-frequency alternating current for supplying the induction heating element 20. The inverter 40 is connected to the

Voltage source 30 is connected and draws over this energy to the

Induction heater 20 to supply. The voltage source 30 includes, but is not limited to, a rectifier, filter electronics, and buffering capacity, and further, the induction heating device 12 includes a control unit 14, which is provided to drive the switching elements 42, 44, 46, 48. The control unit 14 is provided to the switching elements 42, 44, 46, 48 for generating the

To control periodically high-frequency alternating current. The control unit 14 is provided, in operating modes in which operating parameters of the parallel-connected switching elements 42, 44, and 46, 48 differ from each other, the parallel-connected switching elements 42, 44, and 46, 48 with different activity parameters

head for. The control unit 14 is intended to be in such a

Operating mode, the switching elements 42, 44, and 46, 48 with different

To operate duty cycles. Furthermore, the control unit 14 is provided to activate the parallel-connected switching elements 42, 44, and 46, 48 at the same time in such an operating mode. The control unit 14 is provided to the

Turn on switching elements 42, 44, 46, 48 under zero voltage conditions (ZVS). The induction heating element 20 is connected in a half-bridge circuit with resonance. The induction heating element 20 is schematically represented here by a series connection of an inductance and a resistance corresponding to a load. Alternatively, it is conceivable that an induction heating element is connected in full bridge circuit or in one-switch topology.

The induction heater 12 further includes a heat sink 16 which is arranged to dissipate heat generated by the switching elements 42, 44, 46, 48 during operation.

Furthermore, the induction heating device 12 has a temperature sensor arrangement 50. The temperature sensor arrangement 50 has four temperature sensors 52, 54, 56, 58, which are provided to measure temperatures of the heat sink 16 at different positions. The control unit 14 is intended to be made of values of

Temperature sensor assembly 50 temperatures θ ₄₂ , θ ₄₄ , θ ₄₆ , θ _{48 of} the switching elements 42, 44, 46, 48 to calculate. Further, the induction heater 12 has a

Current sensor array 60 on. The current sensor arrangement 60 has four current sensors 62, 64, 66, 68. The current sensors 62, 64, 66, 68 are each connected in series in a parallel branch of the switching elements 42, 44, 46, 48 to the respective switching element 42, 44, 46, 48. The current sensor arrangement 60 is provided for measuring currents l ₄ 2, l ₄₄ , l ₄ 6i Ue flowing through the switching elements 42, 44, 46, 48. In FIG. 3, illustrated by way of example on the switching elements 42, 44, schematic profiles of different operating variables over an activity period during a switching period of a first initial operating mode of the switching elements 42, 44 as a function of time t are shown. In the first operating mode, the

Switching elements 42, 44 simultaneously and with the same frequency turned on and off again later. They have the same phase and the same duty cycle. The upper two graphs show a profile of a voltage U ₂ o and a current l _{20 of} the induction heating element 20. The third and fourth graph or the seventh and eighth graph show curves of voltages U ₄₂ , U ₄₄ and of currents l ₄₂ , l _{44 of} the

Switching elements 42, 44. The fifth and ninth graph from above show switching states S ₄₂ , S _{44 of} the switching elements 42, 44, wherein a value not equal to zero is turned on

State corresponds. The switching elements 42, 44 are switched on at a time t-ι simultaneously and switched off at a time t ₂ simultaneously. The sixth and tenth graphs each show a course of a power loss P ₄₂ , P ₄₄ through

Switching losses when switching off the switching elements 42, 44 is formed. In the lowermost graph, a temperature θ _{44 of} the switching element 44 is shown. The corresponding ones Graphs of the switching elements 42, 44 have a substantially same course. The temperature θ _{44 of} the switching element 44 increases, for example because of a defect, more than a temperature θ _{42 of} the parallel-connected switching element 42. The control unit 14 is provided to the activity parameters of the switching elements 42, 44, 46, 48 as a function of values the temperature sensor assembly 50 to determine. The control unit 14 is intended to adjust the activity parameters of a switching element 42, 44 whose temperature θ ₄₂ , θ ₄₄ exceeds a limit temperature. The limit temperature is 135 ° C. The control unit 14 is provided, for example, to adjust the activity parameters of the switching element 44 when its temperature θ ₄₄ exceeds the limit temperature in order to avoid switching losses in the switching element 44 having an elevated temperature θ ₄₄ . Furthermore, thereby an effective value l _{eff44 of} the current I _{44 of} the switching element 44 and thus line losses are reduced. The control unit 14 is provided to reduce a duty cycle of the switching element 44 and thus turn off earlier than the parallel switching element 42.

FIG. 4 shows by way of example schematic profiles of the various operating variables over an activity period during a switching period of an operating mode which is used in response to the overheating of the switching element 44. In this mode of operation, the switching elements 42, 44 are turned on simultaneously and at the same frequency. The switching elements 42, 44 are turned on at a time t-ι simultaneously. At a time t ₂ ', the switching element 44 is switched off prematurely. The control unit 14 controls the time t ₂ 'of the shutdown so that a current I _{44 of} the switching element 44 reaches zero before the parallel-connected switching element 42 is turned off at a regular time t ₂ . After switching off the

Switching element 44, the current l _{42 of} the parallel-connected switching element 42 increases to compensate for the premature shutdown. The switching element 42 carries at

Switch off only a power loss P ₄₂ . The temperature θ _{44 of} the switching element 44 decreases due to the reduced power loss. If the temperature θ _{44 of} the

Switching element 44 on, the time t ₂ 'of switching off by lowering the clock ratio can be further preferred.

FIG. 5 again shows graphs of the first operating mode in an alternative case. In this alternative case, there is an effective value l _{eff42 of} the current I ₄₂ , for example, by an increased resistance of the switching element 42, lower than an effective value l _{eff44 of} the current l _44th This results for the switching element 44 connected in parallel, a higher power loss P ₄₄ by switching losses and increased line losses.

The control unit 14 is provided to determine the activity parameters of the switching elements 42, 44, 46, 48 in dependence on values of the current sensor arrangement 60. The control unit 14 is provided to adjust the activity _parameters when the rms values _leff42 , _{ff44 of} the switching elements 42, 44 differ by more than 50%. The control unit 14 is provided to shorten the duty cycle of the switching element 44 with the higher effective value l _{eff44 of} the current I ₄₄ .

FIG. 6 shows the graphs achieved by the adaptation of the activity parameters. The switching element 44 with the formerly higher rms value _leff44 is prematurely switched off at the time t ₂ ". The switching element 42 connected in parallel with the formerly low rms value l _eff42 has an increased current l ₄₂ from the _instant t ₂ " onwards in order to switch off the premature switch off other switching element 44 to compensate. The control unit 14 is provided to select the time t ₂ "of the shutdown so that an effective value l _eff42 'and an effective value l _eff44 ' less than 20%

differ from each other, alternatively they are the same.

FIG. 7 shows a time profile of a power P _{20 of} the induction heating _element 20, of rms values l _eff42 , l _eff44 of currents l ₄₂ , l ₄₄ through the switching elements 42, 44 and of temperatures θ ₄₂ , θ _{44 of} the switching elements 42, 44 , from the beginning of one

Heating with high power P ₂₀ on until after reducing the power P ₂₀ due to overheating. Beginning at room temperature, the temperatures θ ₄₂ , θ _{44 of} the switching elements 42, 44 continue to increase, until a time t _10, a first of the

Switching elements 42 reaches the limit temperature. Rather than now reducing the power P ₂₀ to reduce power dissipation of the switching elements 42, 44 and prevent further increase in temperature, the inventive method is used to reduce the power dissipation across the first of the switching elements 42 and to keep the power P ₂₀ constant , The control unit 14 is intended to be the same between the different operating modes, the operating mode

Activity parameters and the operating mode with different activity parameters, to switch, whenever the temperatures require θ ₄₂ , θ ₄₄ to a high To achieve overall efficiency. The temperature θ ₄₂ fluctuates minimally around the

Maximum temperature. If, at a time t _20, the temperature θ _{44 of} the second switching element 44 reaches the limit temperature, the power P _{20 is} reduced to the

To reduce power losses via the switching elements 42, 44 and to avoid further heating. Compared to a classic mode of operation in which the switching elements are operated with the same activity parameters, so a longer time with high power is heated.

If temperatures θ ₄₆ , θ ₄₈ or currents ℓ ₄₆ , ℓ ₄ e of the switching elements 46, 48 have increased values, the procedure is as described for the example of the switching elements 42, 44, corresponding to FIGS. 4 and 6.

Furthermore, any numbers of parallel switching elements are conceivable. Furthermore, it is conceivable that a control unit is provided to a

Delay switch-on of a switching element and prefer a switch-off of a parallel switching element, which effectively creates a different-phase operating mode. Furthermore, a combination of the operating mode with different phases with the operating mode with different

Duty ratios conceivable to achieve a fine-tuning of the power losses.

reference numeral

10 household appliance I42 electricity

12 induction heater I44 power

14 Control unit I46 Power

16 heat sinks I48 electricity

18 hob plate ff42 rms value

20 Induction heating element ff42 'rms value

22 Induction heating element ff44 rms value

24 Induction heating element ff44 'rms value

26 Induction heater P20 power

30 Voltage source P ₄₂ Power loss

40 inverters P44 power dissipation

42 Switching element S42 Switching state

44 Switching element S44 Switching state

46 switching element U ₂₀ voltage

48 switching element U ₄₂ voltage

50 Temperature sensor arrangement U44 Voltage

52 Temperature sensor ti time

54 Temperature sensor tio time

56 Temperature sensor t ₂ Time

58 Temperature sensor t20 time

60 current sensor arrangement t ₂ 'time

62 current sensor t ₂ "time

64 current sensor $ 42 temperature

66 current sensor $ 44 temperature

68 current sensor $ 46 temperature

I20 power $ 48 temperature

Claims

claims

1. induction heating device, in particular induction hob device, with at least two switching elements (42, 44, 46, 48), which are connected in parallel and provided in at least one operating mode, a

high-frequency alternating current for supplying an induction heating element (20, 22, 24, 26) to produce, and with at least one control unit (14), characterized in that the control unit (14) is provided to at least two of the at least two in at least the first operating mode To control switching elements (42, 44, 46, 48) with different activity parameters.

2. induction heating device according to claim 1, characterized in that the at least two switching elements (42, 44, 46, 48) regardless of the

Operating state are connected in parallel.

3. Induction heater according to one of the preceding claims, characterized in that the control unit (14) is provided to operate at least in the operating mode at least two of the switching elements (42, 44, 46, 48) with different duty cycles.

4. Induction heater according to claim 3, characterized in that the

Control unit (14) is provided, at least in the operating mode to activate the at least two switching elements (42, 44, 46, 48) at least substantially simultaneously.

5. Induction heater according to one of the preceding claims,

characterized by a current sensor arrangement (60) which is provided to determine currents flowing through the at least two switching elements (42, 44, 46, 48) (I42, I44, I ₄ 6, Ue). Induction heater according to claim 5, characterized in that the

Control unit (14) is provided, the activity parameters of the at least two switching elements (42, 44, 46, 48) as a function of values of

To determine current sensor arrangement (60).

Induction heater according to one of the preceding claims,

characterized by a temperature sensor assembly (50) arranged to provide temperatures (θ ₄₂ , θ ₄₄ , θ ₄₆ , θ ₄₈ ) of the at least two

Switching elements (42, 44, 46, 48) to determine.

Induction heater according to claim 7, characterized in that the

Temperature sensor assembly (50) to determine.

Domestic appliance, in particular hob, with an induction heating device (12) according to one of the preceding claims.

10. A method of operating an induction heating device (12) according to any one of claims 1 to 8