EP3481143A1 - Heating system for operating a heating element - Google Patents

Abstract

The invention relates to a heating system (200) for operating a heating element (210), in particular in a food processor (1), comprising: - A load circuit (201) which comprises at least two electronic switching elements (250) each having a control terminal (250.2) and one input terminal (250.3), wherein the switching elements (250) are connected in antiseries to an alternating current (I) to the heating element ( 210), a drive circuit (202) for initiating an electrical drive signal (A) for driving the switching elements (250), - An electrical isolation device (270) to generate the drive signal (A) at the control terminals (250.2), so that an electrical potential at the input terminals (250.3) is a common reference potential (S) of the switching elements (250) for the drive signal (A) ,

Description

The present invention relates to a heating system for operating a heating element. Furthermore, the invention relates to a method for operating a heating element and a food processor with a heating system.

Heating systems can be used in electrical appliances for various applications, such as in a food processor for heating a medium in a mixing vessel. In this case, the heating system carries out a control of a heater, for example in the mixing vessel of the food processor, in such a way that the medium to be heated is heated to preselectable nominal values.

So z. B. heating systems in which a thick-film heating is used triacgesteuert to heat the medium to be heated to the desired values. In this case, serve as a controlled variable for a controller of the heating system, the media temperature, which is calculated, for example, by algorithms and based on the detection of a temperature sensor.

Frequently, a heating element for reasons of safety and life with alternating current flows through. Often, however, such heating systems can, for example, be operated with a triac control only with large switching intervals. In particular, the necessity of reducing flicker noise has a limiting effect.

At a large switching interval, such as. 4 s in conventional heating systems, a regulation of the performance of the heating element to comply with the setpoints is often technically complicated. In particular, an unfavorable for some applications control deviation is to be accepted. Thus, known heating systems are often expensive to produce and / or costly and / or too unreliable for certain applications, especially for use in a food processor for at least partially automated preparation of food.

It is therefore an object of the present invention to at least partially overcome the disadvantages mentioned above. In particular, it is an object to provide an improved heating system in which reduces the technical complexity and / or reliability is improved. In particular, the control deviation should be reduced, so that a nearly constant heating power can be achieved. Another object may be a reduction of the power loss during operation of the heating element, in particular a thick-film heating of a food processor.

The above object is achieved by a heating system with the features of claim 1, a method having the features of claim 13 and by a food processor having the features of claim 15. Further features and details of the invention will become apparent from the respective dependent claims, the description and the drawings. In this case, features and details that are described in connection with the heating system according to the invention, of course, also in connection with the inventive method and the food processor according to the invention, and in each case vice versa, so with respect to the disclosure of the individual aspects of the invention always reciprocal reference is or may be ,

In particular, unless expressly stated otherwise, below an electrical connection both a direct and an indirect connection, ie also understood by other electrical components, but in particular only if the connection in the same circuit or exclusively electrically (ie without galvanic isolation).

• einen Lastkreis, welcher zumindest zwei elektronische Schaltelemente, insbesondere Halbleiter-Schaltelemente, mit jeweils einem Steuerungsanschluss und jeweils einem Eingangsanschluss umfasst, wobei vorzugsweise die Schaltelemente antiseriell (im Lastkreis) geschaltet sind, um einen Wechselstrom (des Lastkreises) zum Heizelement zu beeinflussen,
• einen Ansteuerungskreis, um ein elektrisches Ansteuerungssignal zur Ansteuerung der Schaltelemente (insbesondere am jeweiligen Steuerungsanschluss) zu initiieren, wobei vorzugsweise die Schaltelemente auch mit dem Ansteuerungskreis verbunden sind,
• eine Potentialtrennvorrichtung, um den Lastkreis mit dem Ansteuerungskreis zu verbinden und/oder um das Ansteuerungssignal an den Steuerungsanschlüssen (und insbesondere auch an den Eingangsanschlüssen) derart bereitzustellen, insbesondere potentialfrei zu erzeugen, dass ein elektrisches Potential an den Eingangsanschlüssen ein gemeinsames Bezugspotential der Schaltelemente für das Ansteuerungssignal bildet. Hierzu kann die Potentialtrennvorrichtung bspw. sowohl mit den Steuerungsanschlüssen als auch mit den Eingangsanschlüssen elektrisch verbunden sein, um vorzugsweise das Ansteuerungssignal als eine elektrische Spannung zwischen diesen Anschlüssen zu erzeugen.

The above object is achieved in particular by a heating system, in particular a control and / or regulating system, for operating a heating element, in particular in a food processor, comprising:

• a load circuit, which comprises at least two electronic switching elements, in particular semiconductor switching elements, each having a control connection and an input terminal, wherein preferably the switching elements are antiserially (in the load circuit) connected to influence an alternating current (of the load circuit) to the heating element,
• a drive circuit to initiate an electrical drive signal for driving the switching elements (in particular at the respective control terminal), wherein preferably the switching elements are also connected to the drive circuit,
• a potential disconnecting device for connecting the load circuit to the drive circuit and / or for providing the drive signal to the control terminals (and in particular also to the input terminals) in such a way as to generate, in particular, potential-free, that an electrical potential at the input terminals has a common reference potential of the switching elements for the Driving signal forms. For this purpose, the potential separation device may, for example, be electrically connected both to the control terminals and to the input terminals in order to preferably generate the drive signal as an electrical voltage between these terminals.

In other words, the input terminals can be electrically connected directly and are therefore at a common electrical potential, which can preferably be used as a reference potential of the gate-source voltage. In particular, the common reference potential can thus be a common (and therefore the same) electrical potential of the input terminals (source terminals) of the switching elements. This has the advantage of a simple and reliable circuit construction and possibly that cost-saving only requires a voltage source for switching the switching elements becomes. In particular, in this case, the load and control circuit relates to separate switching arrangements, which may optionally be electrically connected to one another and / or may also have separate current paths and / or circuits.

In particular, it may be provided that a switching frequency of the switching elements for triggering (ie also regulating) the heating element is used greater than 1 kHz or greater than 2 kHz or greater than 5 kHz or greater than 10 kHz or greater than 20 kHz. Alternatively or additionally, a power of at least 0.5 kW or at least 1 kW can be switched by the switching elements. Furthermore, it can be provided that the switching elements are designed as (for example N-channel) MOSFETs (ie metal-oxide-semiconductor field-effect transistor), which, for example, a high turn-on speed (slew rate) and / or a low capacitance at the gate Terminal so as to reduce the circuit losses. For example. For example, the MOSFETs may have low on-resistance electrical resistance between the drain and source terminals to reduce the on-state losses.

In particular, it may be necessary for the voltage at the control connection or gate connection to always be or stand in relation to the voltage at the input connection or source connection (due to the changing potential at the switching elements). In other words, then the voltage difference between the input and control terminal in the switched and in the off state of the switching element must be kept constant, and thus in particular be independent of the voltage between the output terminals of the switching elements. This voltage between the output terminals varies, for example, in operation between + 330 V and - 330 V. For example. For this purpose, the control terminals of the switching elements electrically independent of a mains voltage of the heating system (ie potential-free) can be controlled, in particular so that the drive circuit can be controlled by a control circuit and / or a control device, which / which at the same (or alternatively to another) ground potential can lie like the load circuit. In other words, the control of the switching elements can be potential-free. In addition, a high-frequency control of the heating element by the switching elements can offer the possibility to reduce the control deviation of the heating control and thus set a nearly constant heat output.

Therefore, it can preferably be provided that a potential-free and / or high-frequency (that is to say over 2 kHz) activation of the switching elements, in particular MOSFETs, takes place. In this way, the advantage can be achieved that a desired heat output can be set very accurately, and this heating power also remains constant.

For example. For example, the input terminals of the switching elements may be directly electrically connected to each other and / or a second ground potential and thus at a common electrical potential (the common reference potential). Thus, this common potential as the common reference potential for the drive signal, d. H. For example, to form a gate-source voltage or as a reference point for a potential at the control terminal serve. Thus, the advantage can be achieved that a particularly simple and inexpensive construction is made possible, and in particular only a voltage source for switching the switching elements is needed.

In particular, conventionally, due to the operation with the alternating current, there may be the problem that the common reference potential varies. Such a non-constant common reference potential can make the control of the switching elements significantly more difficult. Therefore, it can be provided according to the invention that the drive signal is generated as a potential difference, in particular is generated floating, preferably so that a control voltage between the control terminals and the input terminals (i.e., in particular a gate-source voltage for the switching elements) remains at least almost constant. The control voltage or gate-source voltage can have the same height for both control elements, and, for example, have a different height in the switched-on state of the control elements than in the switched-off state of the switching elements, but are preferably kept at least almost constant in both cases. For example. In this case, the controls always have the same state in normal operation for heating control, so that the alternating current can always be locked for both current directions.

According to a further advantage, the heating element can be operated with an electrical power in the range from 200 W to 5 kW, in particular 500 W to 3 kW, preferably 800 W to 2 kW, preferably 1 kW to 1.5 kW, and / or the switching elements in each case be designed to switch an electric power in these areas. The power supply of the heating element is effected in particular by an electrical voltage, in particular a (possibly high-frequency) AC voltage, preferably a mains voltage, in a range of 100 V to 400 V, preferably 200 V to 300 V, preferably 230 V to 250 V. Preferred the switching elements in opposite directions (antiserial) connected to block both the positive and the negative half wave of the voltage to the power supply (mains voltage) in the off state of the switching elements. In this context, "lock" refers in particular to a state in which the current flow to the heating element is predominantly or completely blocked by the switching elements. Preferably, for this purpose, the switching elements are connected in series with the heating element and integrated into the load circuit (load circuit). Preferably, the drive circuit (drive circuit) and the load circuit are formed separately from each other, so that in particular a flow of current from the heating element to the drive circuit or of one of the switching elements is prevented from the drive circuit.

The different orientation of the switching elements with respect to the current direction is therefore particularly useful to block each current direction through the switching elements (from and to the heating element). In particular, a single switching element, which can be embodied, for example, as a MOSFET, block only one current direction. This is related to the structure of the switching elements, which can cause a behavior of the switching elements, which is similar to a parallel connection of a diode in the respective switching elements. This property of the structure is hereinafter also referred to as a parasitic diode, and may, for. B. between a substrate of a switching element and an output terminal (drain terminal) of this switching element form. Usually (especially in MOSFETs), the carrier material (bulk) is directly connected to an input terminal (source terminal) of the switching element, so that the current flow can be prevented only in one direction. For example. (at a positive voltage), a current flow from source to drain is possible (whereas the current flow is blocked from drain to source in the off state and released in the on state of the switching element). By using at least two switching elements, this problem can be solved reliably and inexpensively.

Possibly. can for certain applications, especially when switching an AC voltage and / or in a high-frequency switching, the control of the switching elements not readily, z. B. by a connected to the control terminal transistor. In particular, this may possibly only cause the sufficient blocking of one of the current directions, since with such a control, a potential difference at the switching elements can fluctuate too much. Thus, when supplying the heating element with a mains voltage, the problem arises that the potential at the input connection (source) may not be constant. In particular, when an alternating voltage at the output terminals (drain terminals) of the switching elements is applied (changing drain potential), a nearly constant potential at the control terminal (gate terminal) or a nearly constant voltage between the control terminal and input terminal of the respective Switching elements are ensured. In other words, it may be provided that a drive voltage of the switching elements (or a potential at the control terminal) is always in relation to the input terminal of a respective switching element. In particular, it is provided for this purpose that a voltage between the input terminal (source) and the control terminal (gate) for the on state and / or the off state is kept at least almost constant and thus at least substantially independent of a voltage between the output terminals the switching elements is. The voltage between the output terminals varies, for example, between +330 V and - 330 V. (in heating mode).

Preferably, an average switching frequency of the switching elements, which is used in a heating operation for controlling a heating power of the heating element, at least 500 Hz or at least 1 kHz or at least 2kHz. This has the advantage that a control deviation of the heating control can be significantly reduced by the high-frequency control.

Furthermore, it is optionally possible in the context of the invention that the load circuit and the control circuit are electrically connected to different masses (in particular, this means that the load circuit is connected to a first ground, and the drive circuit is connected to a second ground, with which the load circuit is not directly or galvanically connected), wherein preferably a first ground potential (first Ground) is connected to the load circuit, and a second ground potential (second ground) is connected to the drive circuit, preferably electrically connected to the input terminals of the switching elements and / or the potential separation device, and particularly preferably forms the common reference potential. In other words, in particular the switching elements (in particular the respective control terminals) can be driven potential-free, ie preferably (at least almost) independent of the power supply or mains voltage for the heating element. This allows a particularly accurate and reliable control of the switching elements, in particular since an at least nearly constant drive signal can be ensured. In particular, the potential-free control makes it possible for the control circuit (ie the control circuit for the switching elements) to be operated in particular with the same ground potential after a potential separation with the same supply voltage (for example the food processor, in particular mains voltage) as the load circuit with the switching elements. For example. For this purpose, a further power supply can be provided for the drive circuit, for example an AC / DC converter for electrical isolation, in order to supply power to the drive circuit. In this case, the further energy supply, for example, can provide a further ground (second ground potential) which differs from the ground of the load circuit (first ground potential) and is provided in particular for the drive circuit. Thus, a simpler and cheaper construction can be achieved.

In this case, the drive signal is preferably designed as a voltage between the control connection (gate) and the input connection (source), ie a gate-source voltage or as an (electrical) potential of the control connection (gate potential). In particular, by using the potential separation device, ie the potential-free control of the switching elements, the drive signal is kept at least almost constant in each case at a first level (for the switched-on state of the switching elements) and / or at a second level (for the switched-off state of the switching elements). The switching between the first and the second level can take place in that the potential separation device is controlled by a control device, for example. By different voltages on the input side of the potential separation device.

Another advantage may be that the switching elements are each designed as a transistor, preferably as a field effect transistor, preferably as a MOSFET, so preferably by switching the respective switching elements based on the drive signal, a current flow between the input terminal and an output terminal of the respective switching element in each one Direction is influenced, preferably for this purpose the control terminal of the respective switching elements is electrically connected to the potential separation device. This has the particular advantage that such switching elements, in particular MOSFETs, have a high turn-on speed (slew rate) and a low capacitance at the gate terminal, so that the switching losses can be significantly reduced. For example. the switching elements are designed as N-channel MOSFETs. In particular, an electrical connection of the control connections with the potential separation device can also be implemented indirectly via further components.

In addition, it is advantageous if the potential separation device comprises a first terminal which is electrically (eg indirectly, possibly via at least one control element, such as a transistor) connected to the control terminals of the switching elements, and a second terminal which electrically ( in particular directly and / or via a second ground) is connected to the input terminals of the switching elements, preferably to generate a potential difference between the first and second terminals for the drive signal. This allows in particular the generation of a corresponding (source-drain) voltage of the switching elements for fast and reliable switching.

It may optionally be possible for the switching elements to be integrated into the load circuit in such a way that they have a different current blocking direction in the load circuit, in particular by a correspondingly different orientation of the switching elements or a parasitic diode (between a carrier material and an output terminal ) of the switching elements, so that preferably different half-waves of a supply voltage of the load circuit can be blocked. This can reliably control an alternating voltage for operating the heating element.

Advantageously, it can be provided in the invention that a control device is provided for heating control, preferably to perform an electrical activation of the potential separation device for generating the drive signal, so preferably the switching elements are driven by high frequency by the drive signal, in particular with a switching frequency (in the high frequency range) via 2 kHz or over 10 kHz or over 20 kHz. For example. In this case, the control device (in the load or a control circuit) may be connected to a first ground, preferably with which the load circuit is also connected. In particular, the first ground may differ from a second ground to which the drive circuit is connected, the potential separation device preferably carrying out the potential separation between load (or control circuit) and drive circuit, and / or galvanically connecting a potential of the load circuit or control circuit to one Potential of the control circuit separates.

It may be advantageous if, in the context of the invention, the load circuit comprises the heating element or is electrically (detachably) connectable to the heating element, wherein the heating element is preferably designed as thick film heating, and is preferably integrated in a mixing vessel of a food processor and / or can be integrated , For example. For example, the heating element may be part of the heating system according to the invention or may be designed separately therefrom. Accordingly, the load circuit can be designed as an open circuit, which is closed by the connection to the heating element. In particular, the heating system and heating element can be detachably connected to one another. Preferably, the heating element may be connected to (electrical) connecting elements which enable a detachable (electrical) connection to (electrical) counter-connecting elements of the heating system. In particular, the heating element can be integrated in a mixing vessel of a food processor, wherein the mixing vessel, for example, releasably in the food processor attachable and / or designed to be integrated. Furthermore, the heating system can be integrated in a stationary part of the food processor, which, for example, can accommodate the mixing vessel. This allows flexible handling of the heating element and the food processor.

A further advantage may be provided that the load circuit comprises a voltage source, in particular an AC voltage source, for providing the alternating current of the load circuit, which preferably via the switching elements electrically (serially) with is connected to the heating element and / or is connectable, in particular to transmit an electrical power to the heating element, so that the power transmission controllable by the switching elements in response to the control signal, in particular switchable, is. Thus, the performance of the heating element can be reliably and quickly controlled.

Optionally, it may be provided that the potential separation device is electrically connected to the switching elements in such a way that an at least almost constant voltage between the respective control connection, in particular a gate connection, and the respective input connection, in particular by the potential separation device upon provision of a drive signal a source terminal, is generated, preferably at least almost independent of a polarity of the alternating current and / or a voltage between output terminals of the switching elements in normal operation. This can ensure that even with the negative half-wave, the heating power is switched reliably.

It may optionally be possible for the drive circuit to comprise an energy transmitter, preferably a separate energy source and / or a switching power supply and / or an AC / DC converter (ie rectifier), in order to preferably provide the power supply of the drive circuit, and preferably the potential separation device for generating to energize the drive signal. For example. In this case, the energy transmitter can be connected to a first ground, with which the load circuit is also connected. In particular, the energy transmitter can provide a different second mass for the control circuit, in particular by performing a potential separation. This has the advantage that the control of the switching elements can be done very reliable. Preferred are AC / DC converters (sometimes referred to as AC / DC converters) rectifiers that convert alternating current into direct current.

Furthermore, it is optionally provided that the potential separation device is designed as an optocoupler. This includes, for example, a transmitter, such as a light-emitting diode, and / or a receiver, such as a photodiode. This has the advantage that reliably a drive signal can be generated floating.

According to a further possibility can be provided in the heating system according to the invention that the potential separation device comprises a first separation unit, in particular a first winding in the drive circuit and a second separation unit, in particular a second winding in the load circuit, preferably by the second separation unit, in particular second winding in that a potential difference as a function of a voltage signal at the first separation unit, preferably the first winding, can be generated for the activation signal. This represents another possibility for the reliable generation of the drive signal.

In this case, it is particularly conceivable for the input terminals to be at a common source potential, and preferably to be connected to the control terminals via the potential isolation device, in particular so that switching off of the switching elements can be effected by the activation signal in order to produce a negative as well as a positive one Half-wave of a power supply in the load circuit to block the flow of current. This enables reliable operation of the heating element.

• die Potentialtrennvorrichtung und eine Spannungsquelle des Lastkreises sind jeweils direkt mit einem gemeinsamen Massepotential verbunden,
• die Potentialtrennvorrichtung, insbesondere ein (ausgangsseitiger) erster Anschluss der Potentialtrennvorrichtung, ist über wenigstens einen ersten Widerstand und/oder wenigstens einem Kontrollelement mit dem ersten Schaltelement und über wenigstens einen zweiten Widerstand und/oder wenigstens einem (ggf. weiteren) Kontrollelement mit dem zweiten Schaltelement verbunden,
• die Potentialtrennvorrichtung, insbesondere (ausgangsseitig) ein erster Anschluss der Potentialtrennvorrichtung, ist über wenigstens einen dritten Widerstand mit einem Source-Potential der Schaltelemente verbunden, wobei vorzugsweise der dritte Widerstand sehr viel größer als der erste und zweite Widerstand ist.

A further advantage can be achieved in the context of the invention if at least one of the following arrangements are provided:

• the potential separation device and a voltage source of the load circuit are each connected directly to a common ground potential,
• the potential separation device, in particular a (output side) first terminal of the potential separation device is at least a first resistor and / or at least one control element with the first switching element and at least one second resistor and / or at least one (possibly further) control element with the second switching element connected,
• the potential separation device, in particular (on the output side) a first terminal of the potential separation device, is connected via at least one third resistor to a source potential of the switching elements, wherein preferably the third resistance is much larger than the first and second resistance.

The invention also generally includes a household appliance, such. As a food processor, with the heating system according to the invention for operating a heating element.

• Ansteuern einer mit dem Ansteuerungskreis verbundenen Potentialtrennvorrichtung durch eine Kontrollvorrichtung in Abhängigkeit von einer Ansteuerungsvorgabe, sodass vorzugsweise bei einer ersten Ansteuerungsvorgabe ein erstes Ansteuerungssignal (insbesondere potentialfrei) erzeugt wird, und bei einer zweiten Ansteuerungsvorgabe ein zweites Ansteuerungssignal (insbesondere potentialfrei) erzeugt wird,
• Anlegen des erzeugten Ansteuerungssignals an wenigstens zwei Schaltelemente, sodass vorzugsweise ein Wechselstrom im Lastkreis zum Heizelement für beide Stromrichtungen gesperrt wird, wenn das erzeugte Ansteuerungssignal das erste Ansteuerungssignal ist, und für beide Stromrichtungen freigegeben wird, wenn das erzeugte Ansteuerungssignal das zweite Ansteuerungssignal ist.

Likewise provided by the invention is a method for operating a heating element, in particular in a food processor. In this case, it is preferably provided that a load circuit with the heating element and a control circuit (in particular separately executed by the load circuit) are provided. In particular, the following steps may be carried out, preferably one after the other or in any desired sequence, it also being possible for individual steps to be carried out repeatedly if necessary:

• Triggering a potential separation device connected to the control circuit by a control device as a function of a control input, so that a first activation signal (in particular potential-free) is preferably generated at a first activation specification, and a second activation signal (in particular potential-free) is generated at a second activation specification,
• Applying the generated drive signal to at least two switching elements, so that preferably an alternating current in the load circuit to the heating element for both current directions is disabled when the generated drive signal is the first drive signal, and is released for both current directions, when the generated drive signal is the second drive signal.

Thus, the inventive method brings the same advantages as have been described in detail with respect to a heating system according to the invention. In addition, the method may be suitable for operating a heating system according to the invention.

For example. the potential separation device can be electrically connected on the input side to a control circuit and / or load circuit, and in particular to a control device, and on the output side to the control circuit, and in particular to the switching elements. The connection to the respective switching element can serve to carry out the application of the generated drive signal by the drive signal is transmitted via the connection to the switching elements.

It may be provided that at least one of the drive signals, a (at least almost constant) voltage is generated as a respective drive signal, for example. A source-gate voltage for the switching elements. For example. can do the Control default digital (intermediate) stored to be evaluated by the control device. The activation specification is, for example, specific to a desired temperature of a medium which is to be heated by the heating element. It is also conceivable that the control input is designed as control information, which, for example, determines a switching frequency with which the heating element is to be controlled. Furthermore, it may be possible for the drive specification to be determined as a function of a detection of a temperature sensor. For example. For example, a first drive command may be first control information (indicating, for example, blocking the AC power) and the second drive command may be second control information (indicating, for example, enabling the AC power).

• wenigstens einem Rührgefäß, welches zumindest ein Heizelement aufweist,
• wenigstens einen Temperatursensor zur Erfassung einer Temperatur am Rührgefäß.

Likewise provided by the invention is a food processor for at least partially automatic food preparation, comprising:

• at least one stirring vessel, which has at least one heating element,
• at least one temperature sensor for detecting a temperature at the mixing vessel.

In this case, it is particularly conceivable that a heating system according to the invention is provided in order to carry out a heating control of the heating element on the basis of the detected temperature, in particular so as to determine a control input. Thus, the food processor according to the invention brings with it the same advantages as have been described in detail with reference to a heating system according to the invention and / or a method according to the invention. In addition, the food processor may be suitable to be operated according to a method according to the invention.

It may also be possible in the food processor according to the invention that a balance is provided which can weigh the medium, in particular at least one food present in the mixing vessel. A thereby determined weight information of the food can be displayed, for example, via a display device, such as a display or a touch screen, a user of the food processor. Further, it may be conceivable that the detected temperature of the temperature sensor and / or a set heating power is displayed on the display device. It may be possible for a heating control of the heating system by the user at a Input device of the food processor, such as the touch screen, influenced or activated. This allows a very comfortable operation of the food processor.

Figur 1

eine Darstellung von Teilen eines erfindungsgemäßen Heizsystems,

Figur 2

eine weitere Darstellung von Teilen eines erfindungsgemäßen Heizsystems,

Figur 3

eine schematische Darstellung von Teilen einer erfindungsgemäßen Küchenmaschine.

Further advantages, features and details of the invention will become apparent from the following description in which, with reference to the drawings, embodiments of the invention are described in detail. The features mentioned in the claims and in the description may each be essential to the invention individually or in any desired combination. They show schematically:

FIG. 1

an illustration of parts of a heating system according to the invention,

FIG. 2

a further illustration of parts of a heating system according to the invention,

FIG. 3

a schematic representation of parts of a food processor according to the invention.

In the following figures, the identical reference numerals are used for the same technical features of different embodiments.

In Fig. 1 Shown schematically are parts of a heating system 200 according to the invention. Next serves Fig. 1 to illustrate a method 100 according to the invention. A load circuit 201 and a drive circuit 202 are identified, which are preferably circuits with separate masses and / or (at least approximately) separate galvanic circuits 201, 202. In addition to the control circuit 202 may optionally be provided a control circuit which, for example, the control device 220 includes and is electrically connected to a potential separation device 270. Alternatively, the control device 220 may also be integrated directly into the load circuit 201. The potential separation device 270 (on the input side, eg in the control circuit) and / or the control device 220 and / or the load circuit 201 may be connected to a first ground potential GND (first ground) (as in FIG Fig. 1 exemplified). A different second ground potential SGND (second ground, which is at least not directly connected to GND) can optionally be connected to a second terminal 270.2 of the potential separation device 270 and / or to an input terminal 250.3 of two switching elements 250 be electrically connected (as well as in Fig. 2 is shown in more detail). In order to provide a power supply for the drive circuit 202, for example, an energy transmitter 280 may be provided which, for example, can provide the second ground potential SGND (this is also closer in FIG Fig. 2 shown).

The switching elements 250, d. H. a first switching element 250a and a differently aligned second switching element 250b, z. B. be designed as a transistor or MOSFETs. Due to a respective parasitic diode 250.1, it is necessary to provide both switching elements 250 in an anti-serial connection in order to completely block (i.e., in both current directions) an alternating voltage U or alternating current I of a voltage source 260, in particular an alternating voltage source 260.

The individual switching elements 250 may have an input terminal 250.3 with a source potential S and an output terminal 250.4 with a drain potential D and a control terminal 250.2 with a drive potential G, in particular gate potential G. On the output side (at the drive circuit 202), the potential separation device 270 can have at least one first (output) port 270.1 and the second (output) port 270.2, which are each connected to the drive circuit 202. Also, on the input side, further (input) connections can be provided which, for example, are connected to the control device side or control circuit side. By way of example, a first separation unit 270.3 (eg, first winding 270.3) and, on the output side, a second separation unit 270.4 (eg, second winding 270.4) of the potential separation device 270, which illustrate the galvanic separation, are shown on the input side may also be an optocoupler or the like, which thus does not have to have windings.

The first terminal 270.1 of the potential separation device 270 is z. B. via a first resistor R1 and / or at least one control element 230 with the control port 250.2 of the first switching element 250a and a second resistor R2 and / or at least one (possibly further) control element 230 to the control port 250.2 of the second switching element 250b electrically connected. Optionally, a third resistor R3 may be provided which z. B. with a high Resistance value is performed to increase the stability of the circuit. The second connection 270.2 of the potential separation device 270 is, for example, electrically connected (eg, directly and / or via a second ground potential) to the input connections 250.3 of the switching elements 250, ie, to the source potential S. In this way, a common reference potential S for the drive signal A can be created and / or the drive signal A can be applied to the switching elements 250 according to a method 100 according to the invention. In particular, the drive signal A (for example, as a gate-source voltage) for driving the switching elements 250, ie, for transferring the switching elements 250 from an open state, in which the current flow of a current I in the load circuit 201 is inhibited, is used in a closed state in which the flow of current is allowed, and / or vice versa. In this way, the heating power of a heating element 210, in particular a thick film heater 210, can be reliably controlled and / or regulated in the load circuit 201.

In Fig. 2 is the in Fig. 1 or a similar circuit configuration of a heating system 200 shown schematically. Here, a power supply device 290 is shown for the drive circuit 202, which has, for example, a voltage source X1, the z. B. supplies a mains voltage and / or the voltage source 260 in Fig. 1 equivalent. This may, for example, be connected to an energy transmitter 280, which z. B. as a rectifier provides the power supply for the drive circuit 202. As a result, it is also possible to provide a second ground potential SGND, which differs from a first ground potential GND of the load circuit 201, that is to say in particular is implemented galvanically separated from it. Furthermore, a first voltage V1 can be provided thereby or through the energy transmitter 280, which z. B. is used to operate at least one control element 230. The one or more control elements 230 are, for example, as a semiconductor switch, for example. As a transistor or MOSFETs, designed to generate the drive signal A, in particular at a drive potential G of the switching elements 250. The potential-free generation of the drive signal A takes place, for example, that at least a control element 230 is driven by the potential separation device 270 and / or the first voltage is generated galvanically isolated and / or the switching elements 250 are each connected to the second ground potential SGND. The potential separation device 270 is, for example, by operated a second voltage V2, which can be provided by the energy exchanger 280.

An initiation of the potential-free generated activation signal A takes place, for example, by a control device 220, which in particular drives the potential separation device 270. For this purpose, the control device 220 provides, for example, a voltage supply U270 for the potential separation device 270 and / or a control signal KS at an input of the potential separation device 270.

In Fig. 3 schematically a mixing vessel 2 of a food processor 1 is shown. In this case, a medium 20 is shown in the mixing vessel 2 with a stirrer 3, wherein the medium 20 can be heated by a heating element 210. The heating element 210 is, for example, integrated into a mixing-vessel bottom 2.1, wherein the heating element 210 can then optionally also be designed separately from the food processor 1. For example. For example, the mixing vessel 2 can be detachably connected to the heating system 200 of the food processor 1, wherein electrical contacts for integrating the heating element 210 into the load circuit 201 can also be provided. The activation of the heating element 210 is then controlled, for example, by a control device 220 which, for example, is likewise connected to the load circuit 201 and / or is integrated in an electronics system of the food processor 1. For controlling the activation of the heating element 210, for example, temperature values can be evaluated by the detection of a temperature sensor 4 by the control device 220, the temperature sensor 4 being integrated into the mixing vessel, for example.

The above explanation of the embodiments describes the present invention solely by way of example. Of course, individual features of the embodiments, if technically feasible, can be combined freely with one another, without departing from the scope of the present invention.

LIST OF REFERENCE NUMBERS

1

food processor

2

mixing vessel

2.1

Mixing vessel bottom

3

agitator

4

temperature sensor

20

medium

100

method

200

heating system

201

load circuit

202

driving circuit

210

Heating element, thick film heating

220

control device

230

control element

250

switching element

250.1

parasitic diode

250.2

control connection

250.3

input port

250.4

output port

250a

first switching element

250b

second switching element

260

Voltage source, AC source

270

Potential separation device

270.1

first connection

270.2

second connection

270.3

first winding

270.4

second winding

280

Energy transformer, energy source, switching power supply

290

Power supply device

A

control signal

D

Drain potential

G

Drive potential, gate potential

I

electric current, alternating current

KS

control signal

GND

first ground potential

SGND

second ground potential

R1

first resistance

R2

second resistance

R3

third resistance

S

Source potential, common reference potential

U

tension

U270

Power supply for 270

X1

Voltage supply, corresponds to 260 if necessary

Claims (15)

Heating system (200) for operating a heating element (210), in particular in a food processor (1), comprising: - A load circuit (201) which comprises at least two electronic switching elements (250) each having a control terminal (250.2) and one input terminal (250.3), wherein the switching elements (250) are connected in antiseries to an alternating current (I) to the heating element ( 210), a drive circuit (202) for initiating an electrical drive signal (A) for driving the switching elements (250), - A potential separation device (270) for providing the drive signal (A) to the control terminals (250.2) such that an electrical potential at the input terminals (250.3) forms a common reference potential (S) of the switching elements (250) for the drive signal (A) , Heating system (200) according to claim 1,
characterized,
in that the load circuit (201) and the drive circuit (202) are electrically connected to different masses, wherein a first ground potential (GND) is connected to the load circuit (201), and a second ground potential (SGND) is connected to the drive circuit (202) , Preferably, with the input terminals (250.3) is electrically connected, and particularly preferably forms the common reference potential (S). Heating system (200) according to claim 1 or 2,
characterized,
in that the switching elements (250) are each designed as a transistor, preferably as a field-effect transistor, preferably as a MOSFET, so that a current flow between the input terminal (250.3) and an output terminal (250.4 ) of the respective switching element (250) is influenced in each case in one direction, wherein for switching the control connection (250.2) of the respective switching elements (250) is electrically connected to the potential separation device (270). Heating system (200) according to one of the preceding claims,
characterized,
in that the potential separation device (270) comprises a first terminal (270.1) which is electrically connected to the control terminals (250.2) of the switching elements (250) and a second terminal (270.2) which is electrically connected to the input terminals (250.3) of the switching elements (250.3). 250) is connected to generate a potential difference between the first and second terminals (270.1, 270.2) for the drive signal (A). Heating system (200) according to one of the preceding claims,
characterized,
in that the switching elements (250) are integrated into the load circuit (201) such that they have a different current blocking direction in the load circuit (201), in particular by a corresponding alignment of a parasitic diode (250.1) between a carrier material and an output terminal (250.4) Switching elements (250), so that different half-waves of a supply voltage of the load circuit (201) can be blocked. Heating system (200) according to one of the preceding claims,
characterized,
that a control device (220) is provided for heating control in order to perform an electrical activation of the potential separation device (270) for the potential-free generation of the drive signal (A) so that the switching elements (250) at high frequency by the drive signal (A) can be controlled, in particular with a switching frequency over 2 kHz. Heating system (200) according to one of the preceding claims,
characterized,
in that the load circuit (201) comprises the heating element (210) or can be connected to the heating element (210), which is designed as thick-film heating, and can preferably be integrated in a mixing vessel (2) of a food processor (1). Heating system (200) according to one of the preceding claims,
characterized,
that the load circuit (201) comprises a voltage source (260), in particular an AC voltage source (260) for providing the alternating current (I) of the load circuit (201) which is connectable via the switching elements (250) electrically connected to the heating element (210), in order to transmit an electrical power to the heating element (210) so that the power transmission is controllable, in particular switchable, by the switching elements (250) as a function of the control signal (A). Heating system (200) according to one of the preceding claims,
characterized,
in that the potential separation device (270) is connected to the switching elements (250) in such a way that an at least almost constant voltage between the respective control connection (250.2), in particular a gate connection, is generated directly by the potential separation device (270) when the drive signal (A) is provided. and the respective input terminal (250.3), in particular a source terminal, can be generated, preferably at least almost independently of a polarity of the alternating current (I) and / or a voltage between output terminals (250.4) of the switching elements (250) during normal operation. Heating system (200) according to one of the preceding claims,
characterized,
in that the drive circuit (202) comprises an energy transmitter (280), preferably a dedicated power source (280) and / or a switching power supply (280) and / or an AC / DC converter (280) to provide the power supply to the drive circuit (202) , and preferably, energizing the potential divider (270) to generate the drive signal (A). Heating system (200) according to one of the preceding claims,
characterized,
in that the potential separation device (270) is designed as an optocoupler. Heating system (200) according to one of the preceding claims,
characterized,
that at least one of the following arrangements are provided: - The potential separation device (270) and a voltage source (260) of the load circuit (201) are each directly connected to a common ground potential (GND), - The potential separation device (270), in particular a first terminal (270.1) of the potential separation device (270), via at least one first resistor (R1) to the first switching element (250a) and at least one second resistor (R2) to the second switching element ( 250b), - The potential separation device (270), in particular a first terminal (270.1) of the potential separation device (270) is connected via at least one third resistor to a source potential (S) of the switching elements (250), wherein the third resistor (R3) very much greater than the first and second resistances (R1, R2). Method for operating a heating element (210), in particular in a food processor (1), wherein a load circuit (201) with the heating element (210) and a control circuit (202) are provided,
wherein the following steps are performed: Driving a potential separation device (270) connected to the drive circuit (202) by a control device (220) as a function of a control input such that a first drive signal (A) is generated floating in a first drive input, and a second drive signal (2) is generated in a second drive input ( A) is generated potential-free, - Applying the generated drive signal (A) to at least two switching elements (250), so that an alternating current (I) in the load circuit (201) to the heating element (210) is blocked for both current directions when the generated drive signal (A), the first drive signal (A ), and is enabled for both current directions when the generated drive signal (A) is the second drive signal (A). Method according to one of the preceding claims,
characterized,
in that a heating system (200) is operated according to one of the preceding claims. Food processor (1) for at least partially automatic food preparation, comprising: at least one stirring vessel (2), which has at least one heating element (210), at least one temperature sensor (4) for detecting a temperature at the mixing vessel (2), characterized,
in that a heating system (200) according to one of the preceding claims is provided in order to carry out a heating control of the heating element (210) on the basis of the detected temperature.

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