EP2928265B1 - Induction heating device and induction hob - Google Patents

Description

Field of application and state of the art

The invention relates to an induction heating device, in particular for an induction hob, with a number of resonant circuits, each resonant circuit having a first pole and a second pole and an induction coil for heating. The invention further relates to an induction hob with such induction heating device.

Generic induction heaters, for example, are used to heat hotplates of an induction hob. For example, a respective induction coil is then arranged below a hob plate of an induction hob and can electromagnetically transmit energy to a cookware, which is on the hob plate by swinging in a known manner.

A generic induction heating device is in the document DE 10017176 A1 shown. In this case, a respective resonant circuit is operated by two respective supply transistors, which apply a pole of the resonant circuit to alternating potentials. The resonant circuit is thus excited to oscillate, and the induction coil can transmit energy in the manner described above. In such induction heaters, however, a high component demand arises on supply transistors, in particular when many resonant circuits are used. This is particularly the case when the induction heating is used for surface cooking, so can supply cookware at any point on a cooktop plate with energy. In addition, a high component requirement arises for driver stages for driving the supply transistors.

The US 4,241,250 shows a similar induction heating device with a plurality of resonant circuits, wherein in each resonant circuit, an induction coil is provided for heating an induction hob. In this case, an AC voltage source is provided, and the entire induction heater has the structure of a bridge rectifier, as is known for induction heaters.

Task and solution

The invention has for its object to provide an induction heater, which has a lower component requirements, especially in a high number of resonant circuits, as well as to provide an induction hob with such an improved induction heating.

This is inventively achieved by an induction heating with the features of claim 1 and an induction hob with the features of claim 11. advantageous as well as preferred embodiments of the invention are the subject matter of the further claims and are explained in more detail below. In this case, some of the features are called and described only for the induction heater or only for the induction hob. However, they should be able to apply independently for both the induction heater and the induction hob independently. The wording of the claims is incorporated herein by express reference.

The invention relates to an induction heating device with a number of resonant circuits, each having a first pole and a second pole, each resonant circuit having an induction coil for heating or induction heating coil. Furthermore, it has a supply line, with which the respective first poles of the oscillating circuits are connected, as well as a first supply transistor and a second supply transistor, each having a first pole and a second pole. The first pole of the first supply transistor is connected to a source of an intermediate circuit voltage, and the second pole of the first supply transistor and the first pole of the second supply transistor are connected to the supply line. The second pole of the second supply transistor is connected to a reference terminal. There is provided a number of switching transistors each having a first pole and a second pole, wherein each resonant circuit is associated with a switching transistor and wherein the first pole of the switching transistor is connected to the second pole of the resonant circuit and the second pole of the switching transistor is connected to the reference terminal , It is advantageous to provide a number of diodes or freewheeling diodes, each having a first pole and a second pole, wherein each oscillating circuit is associated with a freewheeling diode. The first pole of the freewheeling diode is connected to the source and the second pole of the freewheeling diode is connected to the second pole of the respective resonant circuit.

In the case of the induction heating device according to the invention, only one switching transistor is required per resonant circuit, whereas the two supply transistors act simultaneously for all oscillatory circuits. Already from a number of four resonant circuits thus results in a savings in the total number of transistors required. Especially with higher numbers of resonant circuits, the number of required transistors is reduced considerably. It should also be mentioned that cheaper driver components can be used for the supply transistors since, in contrast to the prior art, the respective resonant circuit instead of an active transistor has a passive freewheeling diode which does not require a driver stage.

The supply line and other connections in the induction heating device can be realized, for example, by conductive coatings of a circuit board, by wires, lines or other current-carrying elements. The reference terminal is preferably a ground terminal, which can for example produce a ground, preferably a common ground.

The supply transistors serve to provide an alternating voltage for all resonant circuits simultaneously. This not only saves the number of components, it also ensures that all resonant circuits are excited identically. This can be avoided unwanted noise. The supply transistors are typically designed with sufficient capacity to supply them accordingly when operating all oscillating circuits. For example, they can each have a power of a few kW.

The switching transistors serve to switch the respective resonant circuit to which the switching transistor is connected on and off. When the respective switching transistor is turned on, the respective resonant circuit is in operation. If the respective switching transistor is switched non-conductive, the resonant circuit is not in operation. This allows a separate control of all resonant circuits of the induction heater.

• Zustand 1: Der erste Versorgungstransistor ist leitend und der zweite Versorgungstransistor ist nichtleitend.
• Zustand 2: Der erste Versorgungstransistor ist nichtleitend und der zweite Versorgungstransistor ist leitend.

Preferably, the supply transistors are driven by a supply driver circuit, which is designed to switch the supply transistors alternately gegentaktend conductive and non-conductive. This may mean, for example, that the two following states alternate continuously:

• State 1: The first supply transistor is conductive and the second supply transistor is nonconductive.
• State 2: The first supply transistor is non-conducting and the second supply transistor is conducting.

This advantageously achieves an alternating potential at the supply line with which the oscillating circuits can be operated.

The switching transistors are preferably controlled by a respective switching driver circuit, which is designed to switch the respective switching transistor for activating the resonant circuit to turn on and switch to disable the resonant circuit non-conductive. Thus, a single activation and deactivation of the resonant circuits can be achieved.

Preferably, a respective driver circuit is adapted to switch the switching transistor pulsed conductive, wherein a duty cycle is set in response to a desired power output of the resonant circuit. This makes it possible to individually regulate the power output of the respective oscillating circuits by using different duty cycles. To set a reduced power output, a pulsed drive as described can be used with a certain duty cycle, allowing virtually infinite adjustability.

The driver circuits are preferably connected to a control device which is designed to generate an alternating voltage on the supply line by means of the supply transistors and / or to activate and deactivate oscillating circuits by means of the switching transistors and / or to adjust their power output. Such a control device can be embodied, for example, as a computer, as a microprocessor, as a microcontroller, as a programmable logic controller (PLC) or in another manner. It may comprise, for example, processor means and memory means, wherein instructions are stored in the memory means, in the execution of which the processor behaves in a defined manner. The control device enables overall control of the system and the execution of the functions already described above by means of only one device. It should be understood, however, that the controller may also be split, for example, into a part that controls the supply transistors and another part that controls the switching transistors.

According to the invention, a respective resonant circuit has exactly one induction coil and one capacitor connected thereto. This corresponds to a simple embodiment of a resonant circuit.

The induction coil and the capacitor are connected according to the invention in series. As a result, a series resonant circuit is formed.

Preferably, the induction coil is connected to the supply line and the capacitor is connected to the first pole of the resonant circuit associated switching transistor. This arrangement has proven to be advantageous.

More preferably, a diode or the aforementioned freewheeling diode is looped between the second pole of a respective resonant circuit and the source of the intermediate circuit voltage, whose anode is connected to the second pole of the resonant circuit. By such a freewheeling diode voltage spikes, which can occur for example when deactivating the resonant circuit by means of the associated switching transistor due to the demagnetization of the coil, are derived and made harmless. Damage to respective components can thus be counteracted.

Preferably, the first supply transistor and the second supply transistor together form a half-bridge. This corresponds to a proven design for generating an alternating potential.

The source of the intermediate circuit voltage preferably has a pulsed voltage source and a DC link capacitor. Such a pulsed voltage source may, for example, comprise means for rectifying a mains voltage. The DC link capacitor ensures that the voltage is smoothed.

Preferably, the supply transistors and / or the switching transistors are formed as IGBT transistors. These have proven to be advantageous for the present application.

More preferably, the induction heating on at least four resonant circuits. From this number of resonant circuits is mathematically an advantage in the number of required components to record.

Even more preferably, it has more, particularly preferably clearly more than four oscillating circuits, for example at least ten oscillating circuits. The more oscillating circuits it has, the greater the advantage achieved by the embodiment according to the invention.

The invention further relates to an induction hob with a hob plate, preferably made of glass ceramic, and arranged under the cooktop plate according to the invention induction heating device, as described above.

By means of the induction hob according to the invention, the advantages for an induction hob described with reference to the hob plate according to the invention can be utilized. there can be used on all described with reference to the induction heater and variants variants. Illustrated benefits apply accordingly.

More preferably, the induction hob is designed as Flächeninduktionskochfeld. Such Flächeninduktionskochfelder usually require a very large number of resonant circuits, which results in a particularly high saving of components by the embodiment of the invention just in this case.

These and other features will become apparent from the claims but also from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous and protectable Can represent versions. The subdivision of the application into intermediate headings and individual sections does not limit the general validity of the statements made thereunder.

Brief description of the drawings

Fig. 1:

eine Induktionsheizvorrichtung und

Fig. 2:

ein Induktionskochfeld.

An embodiment of the invention is shown schematically in the drawings and will be explained in more detail below. In the drawings show:

Fig. 1:

an induction heater and

Fig. 2:

an induction hob.

Detailed description of the embodiments

• Ein erster Schwingkreis 21 mit einer ersten Induktionsspule L1 und einem ersten Kondensator C1, welche zwischen einem ersten Pol 211 und einem zweiten Pol 212 des ersten Schwingkreises 21 verbunden sind. Des Weiteren ist an dem zweiten Pol 212 des ersten Schwingkreises 21 eine erste Diode D1 mit ihrer Anode angeschlossen, auf deren Bedeutung nachfolgend noch eingegangen wird. Der zweite Pol 212 ist ferner mit einem ersten Schalttransistor T1 verbunden, welcher wiederum an seinem gegenüberliegenden Pol mit einem Masseanschluss verbunden ist. Der erste Schalttransistor ist weiterhin mit einer ersten Schalttreiberschaltung TR1 verbunden, welche den ersten Schalttransistor T1 leitend oder nichtleitend schalten kann.
• Ein zweiter Schwingkreis 22 mit einer zweiten Induktionsspule L2 und einem zweiten Kondensator C2, welche zwischen einem ersten Pol 221 und einem zweiten Pol 222 des zweiten Schwingkreises 22 verbunden sind. Des Weiteren ist an dem zweiten Pol 222 des zweiten Schwingkreises 22 eine zweite Diode D2 mit ihrer Anode angeschlossen, auf deren Bedeutung nachfolgend noch eingegangen wird. Der zweite Pol 222 ist ferner mit einem zweiten Schalttransistor T2 verbunden, welcher wiederum an seinem gegenüberliegenden Pol mit dem Masseanschluss verbunden ist. Der zweite Schalttransistor ist weiterhin mit einer zweiten Schalttreiberschaltung TR2 verbunden, welche den zweiten Schalttransistor T2 leitend oder nichtleitend schalten kann.
• Ein dritter Schwingkreis 23 mit einer dritten Induktionsspule L3 und einem dritten Kondensator C3, welche zwischen einem ersten Pol 231 und einem zweiten Pol 232 des dritten Schwingkreises 23 verbunden sind. Des Weiteren ist an dem zweiten Pol 232 des dritten Schwingkreises 23 eine dritte Diode D3 mit ihrer Anode angeschlossen, auf deren Bedeutung nachfolgend noch eingegangen wird. Der zweite Pol 232 ist ferner mit einem dritten Schalttransistor T3 verbunden, welcher wiederum an seinem gegenüberliegenden Pol mit dem Masseanschluss verbunden ist. Der dritte Schalttransistor ist weiterhin mit einer dritten Schalttreiberschaltung TR3 verbunden, welche den dritten Schalttransistor T3 leitend oder nichtleitend schalten kann.
• Ein vierter Schwingkreis 24 mit einer vierten Induktionsspule L4 und einem vierten Kondensator C4, welche zwischen einem ersten Pol 241 und einem zweiten Pol 242 des vierten Schwingkreises 24 verbunden sind. Des Weiteren ist an dem zweiten Pol 242 des vierten Schwingkreises 24 eine vierte Diode D4 mit ihrer Anode angeschlossen, auf deren Bedeutung nachfolgend noch eingegangen wird. Der zweite Pol 242 ist ferner mit einem vierten Schalttransistor T4 verbunden, welcher wiederum an seinem gegenüberliegenden Pol mit dem Masseanschluss verbunden ist. Der vierte Schalttransistor ist weiterhin mit einer vierten Schalttreiberschaltung TR4 verbunden, welche den vierten Schalttransistor T4 leitend oder nichtleitend schalten kann.
• Ein fünfter Schwingkreis 25 mit einer fünften Induktionsspule Ln und einem fünften Kondensator Cn, welche zwischen einem ersten Pol 251 und einem zweiten Pol 252 des fünften Schwingkreises 25 verbunden sind. Des Weiteren ist an dem zweiten Pol 252 des fünften Schwingkreises 25 eine fünfte Diode Dn mit ihrer Anode angeschlossen, auf deren Bedeutung nachfolgend noch eingegangen wird. Der zweite Pol 252 ist ferner mit einem fünften Schalttransistor Tn verbunden, welcher wiederum an seinem gegenüberliegenden Pol mit dem Masseanschluss verbunden ist. Der fünfte Schalttransistor ist weiterhin mit einer fünften Schalttreiberschaltung TR_n verbunden, welche den fünften Schalttransistor Tn leitend oder nichtleitend schalten kann.

Fig. 1 shows an induction heating device 10. The induction heating device 10 comprises a number of oscillating circuits, wherein in Fig. 1 only five of these resonant circuits are shown. The following resonant circuits are shown in detail:

• A first oscillatory circuit 21 having a first inductor L1 and a first capacitor C1, which are connected between a first pole 211 and a second pole 212 of the first resonant circuit 21. Furthermore, a first diode D1 with its anode is connected to the second pole 212 of the first resonant circuit 21, the significance of which will be discussed below. The second pole 212 is further connected to a first switching transistor T1, which in turn is at its opposite Pol is connected to a ground terminal. The first switching transistor is further connected to a first switching driver circuit TR1, which can switch the first switching transistor T1 conductive or non-conductive.
• A second oscillation circuit 22 having a second induction coil L2 and a second capacitor C2, which are connected between a first pole 221 and a second pole 222 of the second resonant circuit 22. Furthermore, a second diode D2 with its anode is connected to the second pole 222 of the second resonant circuit 22, the significance of which will be discussed below. The second pole 222 is further connected to a second switching transistor T2, which in turn is connected at its opposite pole to the ground terminal. The second switching transistor is further connected to a second switching driver circuit TR2, which can switch the second switching transistor T2 conductive or non-conductive.
• A third oscillating circuit 23 having a third inductor L3 and a third capacitor C3, which are connected between a first pole 231 and a second pole 232 of the third resonant circuit 23. Furthermore, a third diode D3 with its anode is connected to the second pole 232 of the third resonant circuit 23, the significance of which will be discussed below. The second pole 232 is further connected to a third switching transistor T3, which in turn is connected at its opposite pole to the ground terminal. The third switching transistor is further connected to a third switching driver circuit TR3, which can switch the third switching transistor T3 conductive or non-conductive.
• A fourth oscillation circuit 24 having a fourth induction coil L4 and a fourth capacitor C4, which are connected between a first pole 241 and a second pole 242 of the fourth oscillation circuit 24. Furthermore, a fourth diode D4 with its anode is connected to the second pole 242 of the fourth resonant circuit 24, the significance of which will be discussed below. The second pole 242 is further connected to a fourth switching transistor T4, which in turn is connected at its opposite pole to the ground terminal. The fourth switching transistor is further connected to a fourth switching drive circuit TR4, which can switch the fourth switching transistor T4 conductive or non-conductive.
• A fifth oscillation circuit 25 having a fifth inductor Ln and a fifth capacitor Cn connected between a first pole 251 and a second pole 252 of the first pole 251 fifth resonant circuit 25 are connected. Furthermore, a fifth diode Dn with its anode is connected to the second pole 252 of the fifth resonant circuit 25, the significance of which will be discussed below. The second pole 252 is further connected to a fifth switching transistor Tn, which in turn is connected at its opposite pole to the ground terminal. The fifth switching transistor is further connected to a fifth switching driver circuit TR_n, which can switch the fifth switching transistor Tn to be conductive or non-conductive.

It should be understood that between the illustrated fourth resonant circuit 24 and the fifth resonant circuit 25 shown any number of further resonant circuits, which in Fig. 1 not shown, can be connected. Even after the fifth resonant circuit 25 further resonant circuits can be connected.

The respective first poles 211, 221, 231, 241, 251 of the oscillating circuits 21, 22, 23, 24, 25 are all connected to a common supply line 30. This provides a common, alternating supply voltage for all resonant circuits 21, 22, 23, 24, 25 ready.

For this purpose, the supply line 30 is connected to a first supply transistor TV1 and a second supply transistor TV2. In this case, the first supply transistor TV1 is connected at its pole 30 opposite the supply line to a source 40 of an intermediate circuit voltage which provides a rectified and smoothed voltage. The second supply transistor TV2 is connected to the supply line 30 opposite pole to the ground terminal. The two supply transistors TV1, TV2 are connected to a supply driver circuit TR_V, which alternately turns them on and off in an alternating manner. This means that always one of two supply transistors TV1, TV2 is conductive and the other is non-conductive. This generates a continuously changing potential at the supply line 30, which is suitable for the operation of the oscillating circuits 21, 22, 23, 24, 25, ie for their excitation. For example, the supply transistors TV1, TV2 are driven with a frequency which corresponds to the resonant frequency of the oscillating circuits 21, 22, 23, 24, 25. This resonance frequency is advantageously identical in all oscillating circuits 21, 22, 23, 24, 25.

The source 40 of the intermediate circuit voltage has a pulsed voltage source U1 and a DC link capacitor CZ. The pulsed voltage source U1 supplies a rectified, but not yet smoothed pulsating voltage. The DC link capacitor CZ smoothes this voltage, so that applied to the connected pole of the first supply transistor TV1 a smoothed voltage.

The already mentioned diodes or freewheeling diodes D1, D2, D3, D4, Dn are also connected with their respective cathode to the source 40 of the intermediate circuit voltage. This voltage spikes, which can occur in particular when switching off a respective switching transistor T1, T2, T3, T4, Tn due to the demagnetization of the coil can be derived and recycled in an advantageous manner. They are thus available again for operation of the induction heating device 10 and do not damage a component.

The supply driver circuit TR_V and the switch driver circuits TR1, TR2, TR3, TR4, TR_n are connected to an electronic controller 50 which receives instructions for operating the induction heater 10 from a user in a manner not shown but known in the art. Accordingly, the supply driver circuit TR_V and the switch drive circuits TR1, TR2, TR3, TR4, TR_n are driven such that the transistors TV1, TV2, T1, T2, T3, T4, Tn are switched to provide the desired power output to the inductors L1, Generate L2, L3, L4, Ln. In particular, for this purpose, the switching driver circuits TR1, TR2, TR3, TR4, TR_n are driven such that they switch the switching transistors T1, T2, T3, T4, Tn pulsed conductive. The desired power output can be adjusted by the duty cycle.

Fig. 2 shows an induction hob 100 with a hob plate 110 made of glass ceramic and an induction heater 10. The induction heater 10 is designed as that which in Fig. 1 is shown and described in connection with this figure. At individual components are in Fig. 2 however, only the inductors L1, L2, L3, L4, Ln are shown, while the other components are not explicitly shown. The induction coils L1, L2, L3, L4, Ln are arranged directly below the hob plate 110 and thus can be used for heating a set up on the hob plate 110 cookware. The induction hob 100 can be advantageously equipped with means not shown for detecting a pot position on the hob plate 110, so that only those induction coils L1, L2, L3, L4, Ln are operated, which is actually a pot or other cookware. This energy can be saved and the cooking comfort can be increased because a cookware can be placed anywhere.

Claims (12)

1. Induction heating device (10), comprising:

   - a number of oscillator circuits (21, 22, 23, 24, 25), each having a first pole (211, 221, 231, 241, 251) and a second pole (212, 222, 232, 242, 252), wherein each oscillator circuit includes an inductor coil (L1, L2, L3, L4, Ln) for heating,

   - a supply line (30) to which the respective first poles (211, 221, 231, 241, 251) of the oscillator circuits (21, 22, 23, 24, 25) are connected,

   - a number of switching transistors (T1, T2, T3, T4, Tn) each having a first pole and a second pole, wherein each oscillator circuit (21, 22, 23, 24, 25) is associated with a switching transistor (T1, T2, T3, T4, Tn), and wherein the first pole of the switching transistor (T1, T2, T3, T4, Tn) is connected to the second pole (212, 222, 232, 242, 252) of the oscillator circuit (21, 22, 23, 24, 25) and the second pole of the switching transistor (T1, T2, T3, T4, Tn) is connected to a reference terminal, and

   - a number of freewheeling diodes (D1, D2, D3, D4, Dn) each having a first pole and a second pole, wherein each oscillator circuit (21, 22, 23, 24, 25) is associated with a freewheeling diode (D1, D2, D3, D4, Dn), and wherein the first pole of each freewheeling diode (D1, D2, D3, D4, Dn) is connected to a source (40) of an intermediate circuit voltage and the second pole of the freewheeling diode (D1, D2, D3, D4, Dn) is connected to the second pole (212, 222, 232, 242, 252) of the respective oscillator circuit (21, 22, 23, 24, 25),

   characterized by

   - a first supply transistor (TV1) and a second supply transistor (TV2) each having a first pole and a second pole, wherein

   - the first pole of the first supply transistor (TV1) is connected to the source (40),

   - the second pole of the first supply transistor (TV1) and the first pole of the second supply transistor (TV2) are connected to the supply line (30),

   - the second pole of the second supply transistor (TV2) is connected to the reference terminal, wherein

   - a respective oscillator circuit (21, 22, 23, 24, 25) includes exactly one inductor coil (L1, L2, L3, L4, Ln) and a capacitor (C1, C2, C3, C4, Cn) connected thereto, and wherein

   - the inductor coil (L1, L2, L3, L4, Ln) and the capacitor (C1, C2, C3, C4, Cn) are connected in series.
2. Induction heating device according to claim 1, characterized in that the induction heating device comprises a supply driver circuit (TR_V) and the supply transistors (TV1, TV2) are controlled by the supply driver circuit (TR_V), which circuit is configured to connect the supply transistors (TV1, TV2) alternatingly in push-pull connection to be conductive and non-conductive.
3. Induction heating device according to claim 1 or 2, characterized in that the induction heating device comprises switching driver circuits (TR1, TR2, TR3, TR4, TR_n) and the switching transistors (T1, T2, T3, T4, Tn) are controlled by a respective switching driver circuit (TR1, TR2, TR3, TR4, TR_n), which circuit is configured to connect the respective switching transistor (T1, T2, T3, T4, Tn) to be conductive for activating the oscillator circuit (21, 22, 23, 24, 25) and to be non-conductive for deactivating the oscillator circuit (21, 22, 23, 24, 25).
4. Induction heating device according to claim 3, characterized in that a respective switching driver circuit (TR1, TR2, TR3, TR4, TR_n) is configured to connect the switching transistor (T1, T2, T3, T4, Tn) to be pulsed conductive, wherein a duty cycle is adjusted as a function of a desired power output of the oscillator circuit (21, 22, 23, 24, 25).
5. Induction heating device according to any of claims 2 to 4, characterized in that the induction heating device comprises a controller device (50) and the driver circuits (TR_V, TR1, TR2, TR3, TR4, TR_n) are connected to the controller device (50) which is configured to generate an alternating voltage on the supply line (30) by means of the supply transistors (TV1, TV2) and/or by means of the switching transistors (T1, T2, T3, T4, Tn) to activate and to deactivate oscillator circuits (21, 22, 23, 24, 25) and/or to adjust a power output thereof.
6. Induction heating device according to any of the preceding claims, characterized in that the inductor coil (L1, L2, L3, L4, Ln) is connected to the supply line (30) and the capacitor (C1, C2, C3, C4, Cn) is connected to the first pole (211, 221, 231, 241, 251) of the switching transistor (T1, T2, T3, T4, Tn) associated with the oscillator circuit (21, 22, 23, 24, 25).
7. Induction heating device according to any of the preceding claims, characterized in that the first supply transistor (TV1) and the second supply transistor (TV2) together form a half-bridge.
8. Induction heating device according to any of the preceding claims, characterized in that the source (40) of the intermediate circuit voltage includes a pulsed voltage source (U1) and an intermediate circuit capacitor (CZ).
9. Induction heating device according to any of the preceding claims, characterized in that the supply transistors (TV1, TV2) and/or the switching transistors (T1, T2, T3, T4, Tn) are IGBT transistors.
10. Induction heating device according to any of the preceding claims, characterized in that at least four oscillator circuits (21, 22, 23, 24, 25) are provided.
11. Induction hob, comprising:

    - a cooktop plate (110), preferably made of glass ceramics, and

    - an induction heating device (10) according to any of the preceding claims arranged below the cooktop plate (110).
12. Induction hob according to claim 11, characterized in that it is provided as a planar induction hob.

Images