EP4349134A1

EP4349134A1 - Domestic appliance device and method for operating a domestic appliance device

Info

Publication number: EP4349134A1
Application number: EP22727139.2A
Authority: EP
Inventors: Arturo Acevedo Simon; Carlos CALVO MESTRE; David Cros Querol; Cristina Diez Esteban; Manuel Fernandez Martinez; Guillermo Lazaro Amatriain; Jorge Pascual Aza; Diego Puyal Puente
Original assignee: BSH Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2021-05-26
Filing date: 2022-05-04
Publication date: 2024-04-10
Also published as: WO2022248174A1

Abstract

The invention relates to a domestic appliance device (10), in particular an induction cooking appliance device, comprising at least one switch unit (12, 30) and at least one driver circuit (14) which is designed to set a control voltage for the switch unit (12, 30) and which has a bootstrap unit (16) comprising an adaptation unit (18) that is designed to change at least one parameter of the bootstrap unit (16). In order to increase the operational reliability, the bootstrap unit (16) has a voltage limiting unit (20) for limiting a bootstrap voltage (VBS) dropping across the adaptation unit (18).

Description

Household appliance device and method for operating a

household appliance device

The invention relates to a household appliance device according to the preamble of claim 1 and a method for operating a household appliance device according to the preamble of claim 11.

Induction cooktops are known from the prior art, which include an inverter with two switching units and a driver circuit with a bootstrap unit, a control voltage of at least one of the switching units being set via the bootstrap unit. In some known induction cooktops, a parameter of the bootstrap unit, for example a capacity and/or resistance, can also be changed in order to enable dynamic adaptation to different operating states.

In practice, however, previously known induction hobs with bootstrap technology have reached their limits, especially when stray inductances and fast current transients occur in the inverter layout due to conductor paths. High-frequency noise is generated by the resonance between the inverter's leakage inductors and snubber capacitors. The faster a switching element of the inverter switches off and the larger the leakage inductances and switch-off currents are, the greater the noise generated. The trend today is to use faster components to increase performance and switching currents. In addition, reduction of leakage inductances is limited by the use of through-hole-mount inverter packages and mechanical limitations in PCB layout. Leakage voltages generated due to leakage inductances are thus superimposed with the supply voltage and then rectified by the bootstrap circuit. As a result, two maximum values can be exceeded, namely the maximum permissible supply voltage of the driver and the maximum permissible gate voltage of the inverter switching elements. In both cases, the result is damage or malfunction of the inverter. In addition, the driver can overheat, the electrical power loss of which is directly proportional to the square value of the bootstrap voltage. With previously known inductors For this reason, clamp circuits are used in cooktops to limit the bootstrap voltage. All previously known techniques are based on deriving excess energy. However, driver circuits are mostly located near the hottest part of the circuit board, where the ambient temperature can reach 100°C, making it difficult to dissipate a certain amount of energy, which until now has led to overdesign of clamping or dissipation devices.

The object of the invention is in particular, but not limited to, to provide a generic device with improved properties in terms of operational reliability. The object is achieved according to the invention by the features of claims 1 and 11, while advantageous refinements and further developments of the invention can be found in the dependent claims.

The invention is based on a household appliance device, in particular an induction cooking appliance device, with at least one switching unit and with at least one driver circuit which is intended to set a control voltage for the switching unit and which has a bootstrap unit which includes an adaptation unit which is provided for this purpose is to change at least one parameter of the bootstrap unit.

It is proposed that the bootstrap unit has a voltage limiting unit for limiting a bootstrap voltage drop across the matching unit.

With such a configuration, a generic household appliance device with improved properties in terms of operational reliability can be provided. Advantageously, the driver and/or the switching unit can be protected against damage caused by overvoltages. Operating reliability and/or an operating time of the household appliance device can also be advantageously increased by effectively reducing, preferably minimizing, negative influences from stray impedances, in particular on the driver and/or the switching unit. Furthermore, costs can advantageously be kept low. In addition, a household appliance device with improved properties in terms of switching behavior can advantageously be made available. In particular, a fast response time of the switching unit can be achieved, as a result of which control and/or efficiency of the household appliance device can be improved in particular. A "household appliance device", in particular an "induction cooking appliance device", advantageously an "induction hob appliance" should be understood to mean at least a part, in particular a subassembly, of a household appliance, in particular an induction cooking appliance, advantageously an induction hob. A household appliance having the household appliance device is advantageously a cooking appliance, in particular an induction cooking appliance. A household appliance configured as a cooking appliance could be, for example, an oven, in particular an induction oven and/or a microwave and/or a grill, in particular an induction grill and/or a steamer. A household appliance designed as a cooking appliance is advantageously a hob and preferably an induction hob.

The domestic appliance device preferably comprises a control unit, at least one inverter and at least one heating element, in particular at least one inductor. The inverter is preferably provided to provide and/or generate an oscillating electric current, preferably with a frequency of at least 1 kHz, in particular at least 10 kHz and advantageously at least 20 kHz, in particular for operating the at least one heating element. The inverter advantageously includes the switching unit. In this context, a “switching unit” should be understood to mean a preferably electronic unit which comprises a switching element and is intended to interrupt a conduction path, in particular one comprising at least part of the switching unit. The switching element is preferably designed as a circuit breaker and is intended to switch a current of at least 0.5 A, preferably at least 4 A and particularly preferably at least 10 A, in particular periodically. The switching unit is advantageously designed as a bidirectional unipolar switching unit and includes in particular a control input and a reference voltage connection, a switching state of the switching unit being controllable by a control voltage between the control connection and the reference voltage connection. The reference voltage connection can be at a floating potential. The switching element of the switching unit can be in the form of any switching element that a person skilled in the art considers sensible, preferably a semiconductor switching element, such as a transistor, preferably an FET, a MOSFET and/or an IGBT. In particular, a switching unit can also include a number of control inputs, reference voltage connections and/or switching elements. In this context, a "conduction path" should be understood as an element which at least temporarily produces an electrically conductive connection between at least two points and/or at least two components. A “floating potential” is to be understood in particular as a potential which changes its potential value, preferably periodically, by at least 10 V, advantageously by at least 50 V, preferably by at least 75 V and particularly preferably by at least 100 V. The driver circuit preferably has at least one driver. In this context, a "driver" is to be understood as an electronic unit which comprises a driver input, a driver output and/or preferably two supply voltage connections and is intended to be in at least one operating state, in particular in an operating state in which one of the two supply voltage connections applied voltage exceeds a limit value, in particular at least 8 V, preferably at least 10 V, to amplify a voltage signal and/or potential applied to the driver input, in particular of the control unit, and in particular to feed it to the control terminal of the switching unit. The driver unit can also have a number of driver inputs, driver outputs and/or more than two supply voltage connections.

The bootstrap unit is preferably provided to generate and/or provide a bootstrap voltage and in particular to feed it to the two supply voltage connections, as a result of which a switching state of the switching unit can preferably be controlled. In this case, the bootstrap voltage corresponds at least essentially to the supply voltage of the driver, which is in particular present at the two supply voltage connections. Preferably, the bootstrap unit also includes at least one bootstrap resistor and/or at least one bootstrap diode. In this context, a “bootstrap capacitance” is to be understood in particular as a unit which comprises at least one capacitor and advantageously at least two capacitors and is intended in particular to provide energy, in particular the bootstrap voltage, in particular to supply the driver. The bootstrap resistor comprises at least one resistance component and advantageously at least two resistance components, and is intended to limit a current flowing into the bootstrap capacitance and/or through the at least one bootstrap diode. The bootstrap unit includes the adjustment unit, which is provided for changing and/or preferably adjusting at least one, preferably electronic, parameter of the bootstrap unit, in particular dynamically. The term “adapt” is intended to mean to optimize and/or adjust to beneficial operation. The adaptation unit preferably comprises the bootstrap capacity. However, it would also be conceivable for the adaptation unit to be designed separately from the bootstrap capacitance. The bootstrap voltage corresponds to the voltage dropped across the matching unit. The voltage limiting unit is intended to limit the bootstrap voltage drop across the adaptation unit, in particular to a maximum value which does not exceed a maximum permissible supply voltage of the driver and/or a maximum gate voltage of the switching element of the switching unit.

The voltage limiting unit is preferably arranged electrically upstream of the adjustment unit and in particular arranged electrically parallel to the adjustment unit, specifically preferably between a connection of the adjustment unit to a secondary energy source for supplying energy to the driver. The voltage limiting unit could be embodied as an integrated circuit (IC). The voltage-limiting unit is preferably made up of discrete electrical and/or electronic components, which advantageously makes it possible to provide a particularly simple, cost-effective voltage-limiting unit that is individually adapted to the respective needs of the drivers and/or switching elements used in the switching unit.

The household appliance device can also include a number of switching units, driver circuits and/or inverters. Furthermore, the driver circuit can include multiple drivers and/or multiple bootstrap units. The household appliance device can in particular also form the entire household appliance.

In the present application, numerals, such as "first" and "second", which precede certain terms, serve only to distinguish objects and/or to associate objects with one another and do not imply an existing one Total number and/or ranking of objects. In particular, a "second object" does not necessarily imply the existence of a "first object". “Provided” is to be understood to mean specially programmed, designed and/or equipped. The fact that an object is provided for a specific function should be understood to mean that the object fulfills and/or executes this specific function in at least one application and/or operating state.

In addition, it is proposed that the adjustment unit is provided to change the at least one parameter of the bootstrap unit as a function of the bootstrap voltage drop across the adjustment unit. In this way, an advantageously simple control can be achieved.

It is also proposed that the at least one parameter corresponds to a loading time constant of the bootstrap unit. In this context, a “charging time constant” should be understood to mean a charging time of the bootstrap capacity and/or a period of time after which the bootstrap capacity has a voltage value and/or an effective voltage value which is in particular at least 63%, advantageously at least 75%, particularly advantageously at least 80%, preferably at least 90% and particularly preferably at least 95%, of a maximum voltage value and/or maximum effective voltage value of the bootstrap capacitance. As a result, an advantageously simple and, in particular, cost-effective adaptation of the bootstrap unit to different operating states can be achieved.

The at least one parameter preferably has a value between 10 ⁹ s and 10 ⁵ s and preferably between 10 ⁸ s and 10 ⁶ s, at least in a starting operating state. A "starting operating state" is to be understood in this context as an operating state which starts, in particular immediately, after the domestic appliance device has been started and/or an operating program has been selected and/or an operating program has been changed. In particular, the bootstrap capacity is completely discharged at the beginning of the starting operating state, in particular over a longer period of in particular at least 1 ms, advantageously at least 0.5 s, preferably at least 1 s and particularly preferably at least 5 s. In particular, it changes and/or increases a maximum voltage value stored in the bootstrap capacity and/or effective voltage value and/or a maximum bootstrap voltage in the starting operating state at least between two switching operations of the switching unit and preferably between all switching operations of the switching unit. Through this In particular, a fast response behavior of the household appliance device can be achieved.

Furthermore, it is proposed that the at least one parameter has a value between 10 ⁷ s and 10 ³ s and preferably between 10 ⁶ s and 10 ⁴ s, at least in a continuous operating state. In this context, a “continuous operating state” should be understood to mean an operating state which, preferably immediately, follows the starting operating state. In particular, a maximum voltage value and/or effective voltage value and/or a maximum bootstrap voltage stored in the bootstrap capacitance is at least substantially constant in the continuous operating state at least between two switching operations of the switching unit and preferably between all switching operations of the switching unit. In this context, “at least essentially constant” is to be understood as meaning a change by a maximum of 5%, preferably by a maximum of 2% and particularly preferably by a maximum of 1%. In this way, an advantageous filter effect, in particular filtering of a supply voltage and/or the bootstrap voltage, can be achieved, as a result of which possible leakage currents and/or leakage voltages, which are caused in particular by stray impedances, can be effectively minimized.

The at least one parameter could be given by an inductance value of the bootstrap unit, for example. However, the at least one parameter preferably corresponds to a capacitance value and/or an effective capacitance value of the bootstrap unit. As a result, an advantageously simple and uncomplicated adaptation of the bootstrap unit can take place.

Alternatively and/or additionally, it is proposed that the at least one parameter corresponds to a resistance value and/or an effective resistance value of the bootstrap unit. This can in particular increase the flexibility of the household appliance device.

In addition, it is proposed that the matching unit comprises at least two capacitors or at least two resistance components which are connected in parallel in at least one operating state, in particular in the starting operating state and/or the continuous operating state. In this way, in particular, a simple construction can be achieved. It is also proposed that the matching unit comprises at least two capacitors or at least two resistance components which are connected in series in at least one operating state, in particular in the starting operating state and/or the continuous operating state. As a result, the domestic appliance device can be adapted in particular flexibly to different requirements.

If the matching unit includes a bridging switching element, which is provided for bridging and/or at least one component, in particular at least one capacitor and/or at least one resistor component, of the bootstrap unit in at least one operating state, in particular in the starting operating state and/or the continuous operating state To avoid this, the at least one parameter can advantageously be adjusted easily and in particular during operation of the household appliances device. The bridging switching element can be configured as any switching element that a person skilled in the art considers sensible, preferably a semiconductor switching element, such as a transistor, preferably a FET, a MOSFET and/or an IGBT. In particular, the matching unit can also have a plurality of preferably identically designed bridging switching elements.

The matching unit and/or the bridging switching element could, for example, be controlled by a control signal from the control unit. However, the adjustment unit and/or the bridging switching element is preferably designed to be self-controlling. The fact that the adjustment unit is "self-controlling" is to be understood as meaning that the adjustment unit, in at least one operating state, automatically and/or independently controls its state, in particular the switching state, in particular as a function of a, in particular instantaneous, voltage value and/or current value of the Driver circuit and / or the bootstrap unit changes. Preferably, the adjustment unit and/or the bridging switching element is not connected, in particular directly, to the control unit. In this way, an advantageously simple, cost-effective and reliable control can be achieved.

In addition, it is proposed that the voltage limiting unit has at least one energy store, which is arranged electrically in parallel with the adjustment unit. With such a configuration, the driver circuit can advantageously be protected against high-frequency voltage peaks using particularly simple technical means. In addition, a particularly fast and advantageous through the energy storage efficient charging of the matching unit capacitors can be achieved. At the same time, a voltage rise rate and/or an inrush current can advantageously be limited by means of the energy store.

Furthermore, it is proposed that the energy store has at least one storage capacitor unit. As a result, an energy store can advantageously be realized with particularly simple technical means. The storage capacitor unit has at least one storage capacitor. The storage capacitor unit could have a plurality of storage capacitors. A plurality of at least two storage capacitors of the storage capacitor unit could be connected in parallel with one another. Alternatively or additionally, it would also be conceivable for a plurality of at least two storage capacitors of the storage capacitor unit to be arranged in series with one another. The storage capacitor unit preferably has precisely one storage capacitor, as a result of which a particularly cost-effective storage capacitor unit that is technically simple to implement can advantageously be implemented. In addition, it is proposed that the storage capacitor unit has a capacitance of between 10 nF and 1 pF. In particular, the storage capacitor unit has a capacitance between 20 nF and 900 nF, advantageously between 30 nF and 850 nF, advantageously between 40 nF and 750 nF, preferably between 50 nF and 650 nF and particularly preferably between 60 nF and 550 nF. As a result, a high degree of flexibility can advantageously be achieved. The capacitance of the storage capacitor unit refers to the effective total capacitance of all storage capacitors of the storage capacitor unit.

The voltage limiting unit could be connected to the control unit and be controllable by it with the aid of control signals. In an advantageous embodiment, however, it is proposed that the voltage-limiting unit be designed to be self-controlling. Such an embodiment advantageously makes it possible to provide a particularly compact household appliance device with reduced production and/or material costs. Advantageously, additional connecting lines between the voltage limiting unit and the control unit can be dispensed with. Since the voltage limiting unit is designed to be "self-controlling", it should be understood that the voltage limiting unit was in at least one operating state, its state, in particular the switching state, automatically and/or automatically, in particular particular depending on a particular instantaneous voltage value and / or current value of the driver circuit and / or the bootstrap unit changes. The voltage limiting unit is preferably free of a connection, in particular a direct connection, to the control unit. In this way, an advantageously simple, cost-effective and reliable control can be achieved.

It is also proposed that the voltage limiting unit has at least one semiconductor switching element, which is provided to establish or disconnect an electrically conductive connection between the matching unit and the energy store depending on a threshold value of the bootstrap voltage drop across the matching unit. Such a configuration can advantageously achieve effective protection of the driver and the switching element against overvoltages. In particular, the semiconductor switching element is designed as a transistor, for example as an IGBT, preferably as a MOSFET and particularly preferably as an n-channel MOSFET. The semiconductor switching element of the voltage limiting unit is preferably provided to establish or disconnect the electrically conductive connection between the adjustment unit and the energy store and between the adjustment unit and the secondary energy source depending on the threshold value of the bootstrap voltage dropping across the adjustment unit. The semiconductor switching element is preferably provided to disconnect the connection between the adjustment unit and the energy store and between the adjustment unit and the secondary energy source, in particular automatically, when the threshold value is reached and/or exceeded. The semiconductor switching element is preferably provided to establish the connection between the matching unit and the energy store and between the matching unit and the secondary energy source when the threshold value is undershot, in particular automatically. The semiconductor switching element of the voltage limiting unit could be connected to the control unit and be controllable by it for the purpose of establishing and/or separating the connection. However, the semiconductor switching element of the voltage-limiting unit is preferably designed to be self-controlling, based on the threshold value of the bootstrap voltage drop across the matching unit.

In addition, it is proposed that the voltage limiting unit has at least one Z diode, which is electrically connected to a control electrode of the semiconductor switching element is conductively connected. With such a configuration, self-control of the voltage-limiting unit can advantageously be achieved with particularly simple technical means and in a particularly cost-effective manner. Furthermore, it is proposed that the threshold value of the bootstrap voltage drop across the matching unit is characterized by a breakdown voltage of the Z diode. As a result, the threshold value of the bootstrap voltage dropping across the matching unit can advantageously be adjusted in a particularly simple manner. The Z diode preferably has a breakdown voltage between 5 V and 20 V. Depending on the required breakdown voltage, the Zener diode can be designed either as a Zener diode or as an avalanche diode. Depending on the required threshold value, the use of conventional Z diodes based on silicon or silicon carbide semiconductors with breakdown voltages of 10 V to 20 V and/or based on gallium nitride semiconductors with breakdown voltages between 5 V and 10 V is particularly recommended. conceivable. The voltage limiting unit preferably has a control capacitor which is arranged in parallel with the zener diode, in particular in order to standardize a leakage inductance of the zener diode, which can vary depending on the manufacturer and/or type of zener diode used. In addition, the voltage-limiting unit preferably has at least one variable resistor, which is provided to limit currents flowing through the Z-diode and thus, in particular, to prevent damage to the Z-diode.

The invention also relates to a household appliance, in particular an induction cooking appliance, with at least one household appliance device according to one of the configurations described above. Such a household appliance is characterized in particular by its advantageous properties with regard to operational reliability and ease of use, which can be provided by the household appliance device.

The invention is also based on a method for operating a household appliance device, in particular according to one of the configurations described above, with a switching unit and with a driver circuit which is intended to set a control voltage for the switching unit and which has a bootstrap unit which has an adaptation unit comprises, which is intended to change at least one parameter of the bootstrap unit.

It is proposed that a bootstrap voltage dropped across the matching unit is automatically limited. Such a method can advantageously Particularly reliable and safer operation of the household appliance device is achieved, which means that the longevity of the household appliance device can also be improved in particular.

The domestic appliance device should not be limited to the application and embodiment described above. In particular, the domestic appliance device can have a number of individual elements, components and units that differs from a number specified here in order to fulfill a function described herein.

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

Show it:

1 shows a household appliance with a household appliance device in a schematic plan view,

Fig. 2 shows a simplified electrical schematic diagram of the household appliance device with two switching units and a driver circuit having a bootstrap unit,

3 shows a schematic diagram of various signals for controlling the household appliance device,

4 shows a schematic electrical circuit diagram of the bootstrap unit with an adjustment unit and a simplified voltage limiting unit,

5 shows a schematic electrical circuit diagram of the bootstrap unit with the matching unit and the voltage limiting unit and

6 shows a schematic process flow diagram to illustrate a process for operating the household appliance device.

Figure 1 shows a household appliance 32 in a schematic plan view. In the present case, the household appliance 32 is designed as an induction cooking appliance, specifically as an induction hob. In the present case, the household appliance 32 has a hob plate 106 four heating zones 34 on. Each heating zone 34 is intended to heat exactly one cookware element (not shown). In addition, the household appliance 32 includes a household appliance device 10. To control operation of the household appliance 32, the household appliance device 10 includes a control unit 36. The control unit 36 has a computing unit, a memory unit and an operating program stored in the memory unit, which is intended to be Arithmetic unit to be executed.

FIG. 2 shows a simplified basic circuit diagram of the household appliance device 10. A specific embodiment of the household appliance device 10 is shown in FIGS. The household appliance device 10 has a heating unit 38 . The heating unit 38 comprises at least one inductor (not shown) and can in particular comprise a plurality of inductors. In addition, the heating unit 38 can include a switching arrangement (not shown) in order to operate the inductors alternately and/or together, for example in a time-division multiplex process. To supply the heating unit 38, the household appliance device 10 includes a main energy source 40, which provides a pulsating rectified mains voltage in an operating state. Furthermore, the household appliance device 10 includes an inverter 42. The inverter 42 includes two switching units 12, 30. The switching units 12, 30 are essentially identical to one another. The switching units 12, 30 each include a control input. In addition, the switching units 12, 30 each include a switching element. The switching elements are designed as IGBTs. Furthermore, the switching units 12, 30 each include a freewheeling diode and a snubber capacitance, which are connected in particular in parallel with the switching elements. Alternatively, it is also conceivable for a household appliance device to have a number of inverters. In addition, it is conceivable that at least one inverter has different switching units.

A first connection of the main energy source 40 is electrically conductively connected to a collector connection of a first switching unit 12 of the switching units 12, 30 and/or the switching element of the first switching unit 12. In addition, a second connection of the main energy source 40 is electrically conductively connected to an emitter connection of a second switching unit 30 of the switching units 12, 30 and/or the switching element of the second switching unit 30. The inverter 42 is provided to convert the pulsating rectified mains voltage of the main energy source 40 into a high-frequency To convert alternating current and in particular to supply the heating unit 38 . The heating unit 38 is arranged in a bridge branch between a center tap 44 of the inverter 42 and a resonance unit 46 .

In addition, the household appliance device 10 includes a driver circuit 14. The driver circuit 14 is provided to generate a control voltage for the switching units 12,

30 to set. For this purpose, the driver circuit 14 includes a secondary energy source 48. The secondary energy source 48 has a voltage between 10V and 25V. In the present case, a first connection of the secondary energy source 48 is electrically conductively connected to the second connection of the main energy source 40 via a first conduction path 54 . Furthermore, the driver circuit 14 includes two drivers 50, 52. The drivers 50, 52 are identical to each other. Alternatively, it is also conceivable to use different drivers. Drivers 50, 52 are in the form of high-voltage ICs (high-voltage integrated circuits). Each of the drivers 50, 52 has a driver input and a driver output. In addition, each of the drivers 50, 52 has two supply voltage connections. A first driver 50 of the drivers 50, 52 is provided to operate the first switching unit 12. A second driver 52 of the drivers 50, 52 is provided to operate the second switching unit 30. For this purpose, the driver inputs of the drivers 50, 52 are each connected to the control unit 36 in an electrically conductive manner. The driver outputs of the drivers 50, 52 are each connected to the control inputs of the switching units 12, 30 in an electrically conductive manner. In addition, the driver circuit 14 has a bulk capacitor 56 . The bulk capacitor 56 is designed as an energy buffer. The bulk capacitor 56 has a capacitance between 10 nF and 330 nF. The bulk capacitor 56 is intended to provide a largely constant supply voltage for the second driver 52 . For this purpose, a first connection of the bulk capacitor 56, in particular via the first conduction path 54, is electrically conductively connected to the first connection of the secondary energy source 48. The first connection of the bulk capacitor 56 is electrically conductively connected, in particular via the first conduction path 54, to a first supply voltage connection of the second driver 52. In addition, the first terminal of the bulk capacitor 56 is electrically conductively connected to the emitter terminal of the second switching unit 30, in particular via the first conductive path 54. The first conduction path 54 thus serves as a reference voltage connection for the second switching unit 30. The first conduction path 54 is at a fixed potential. A second terminal of the bulk capacitor 56 is connected to a second Connection of the secondary energy source 48 electrically connected. The second connection to the bulk capacitor 56 is electrically conductively connected to a second supply voltage connection of the second driver 52 .

Furthermore, the driver circuit 14 includes a bootstrap unit 16, which is initially shown in greatly simplified form in FIG. 2 and is to be explained in detail below with reference to FIGS. The bootstrap unit 16 includes a bootstrap diode 58. The bootstrap unit 16 includes a bootstrap capacitor 60. The bootstrap capacitor 60 is designed as an energy buffer. The bootstrap capacitor 60 has an effective capacitance value between 33 nF and 3.3 pF. The bootstrap capacitance 60 has a voltage-dependent capacitance value. In addition, the bootstrap unit 16 includes a bootstrap resistor 62. The bootstrap resistor 62 is provided to limit a current flowing into the bootstrap capacitance 60 and through the bootstrap diode 58. The bootstrap resistor 62 has an effective resistance of between 0.5W and 50W.

The bootstrap diode 58 is electrically conductively connected with an anode connection to the second connection of the secondary energy source 48 . The bootstrap diode 58 is electrically conductively connected with a cathode connection to a first connection of the bootstrap resistor 62 . A second connection of the bootstrap resistor 62 is electrically conductively connected to a first connection of the bootstrap capacitance 60 . Furthermore, the second connection of the bootstrap resistor 62 is electrically conductively connected to a first supply voltage connection of the first driver 50 . A second connection of the bootstrap capacitor 60 is electrically conductively connected to the center tap 44 via a second conduction path 64 . Accordingly, the bootstrap capacitance 60 is electrically conductively connected to a collector connection of the second switching unit 30 and/or the switching element of the second switching unit 30 and an emitter connection of the first switching unit 12 and/or the switching element of the first switching unit 12 . Furthermore, the bootstrap capacitance 60 is electrically conductively connected to a second supply voltage connection of the first driver 50, in particular via the second conduction path 64. The second conduction path 64 serves as a reference voltage connection for the first switching unit 12. The second conduction path 64 is at a floating potential. In an operating state in which the switching units 12, 30 are switched alternately, the second conduction path 64 is alternately at a reference potential of the first Conduction path 54 and a mains voltage potential Vo. The bootstrap capacitance 60 is intended to provide a bootstrap voltage _VBS . In this case, the bootstrap voltage _VBS corresponds to a supply voltage of the first driver 50 and is present at the supply voltage connections of the first driver 50 in particular in at least one operating state.

In the present case, the drivers 50, 52 are also equipped with undervoltage lockout (UVLO) protection. Accordingly, the drivers 50, 52 have no function when the supply voltage is below a limit value, in particular when it is present at the supply voltage terminals. In the present case, the limit value is between 9 V and 16 V. Drivers 50, 52 are therefore provided to amplify a voltage signal of control unit 36 present at the driver input in an operating state in which a voltage present at the supply voltage connections exceeds the limit value .

FIG. 3 shows a schematic diagram of various signals for controlling the household appliance device 10 in a starting operating state and a continuous operating state, in particular following the starting operating state. An ordinate axis 68 is shown as a magnitude axis. The time is shown on an abscissa axis 66 . The abscissa axis 66 has two periods of time with an interruption, where a first period of time represents a starting operating state and a second, in particular later, period of time represents a continuous operating state. A curve 70 illustrates the switching states of the switching element of the second switching unit 30. A curve 72 illustrates the switching states of the switching element of the first switching unit 12. A "0" level defines a non-conductive state. A curve 74 shows the mains voltage potential V ₀ of the main energy source 40. In the present case, the mains voltage potential V ₀ has a creeping voltage V _L EAK superimposed on it. The creep voltage VLEAK shows a curve 76. The creep voltage V _L EAK can occur due to leakage inductances of connecting lines, in particular of connecting cables and/or conductor tracks, in particular after the switching unit 12 has been closed. Furthermore, a curve 78 shows an input voltage of the Bootstrap unit 16, while a curve 80 represents the bootstrap voltage _VBS . The input voltage of the bootstrap unit 16 corresponds to a superimposition of the mains voltage potential Vo and the voltage potential of the secondary energy source 48. The bootstrap voltage VB _S corresponds at least essentially to an envelope of the input voltage and in particular to a supply voltage of the first driver 50. An optimal supply voltage of the first driver 50, in particular specified by a manufacturer specification, defines a curve 82. As a result, the bootstrap voltage VBS is compared to the optimal supply voltage of the first driver 50 increases at least in the starting operating state, which can lead to the destruction and/or malfunction of the first driver 50 in particular. According to the invention, the bootstrap voltage V _B s in the continuous operating state corresponds at least essentially to the optimal supply voltage of the first driver 50, as a result of which a destruction and/or a malfunction of the first driver 50 can advantageously be counteracted.

In an operating state, the switching units 12, 30 are switched alternately. Thus, at least at a first point in time, the second switching unit 30 is open and the first switching unit 12 is closed, and at at least a second point in time, in particular different from the first point in time, the second switching unit 30 is closed and the first switching unit 12 is open. In this case, the bulk capacitor 56 and the bootstrap capacitor 60 are alternately charged and discharged. The bulk capacitor 56 is discharged during an activation of the second switching unit 30 . The bulk capacitor 56 is charged during activation of the first switching unit 12 . Bootstrap capacitance 60 is discharged during activation of first switching unit 12 . Bootstrap capacitance 60 is charged via bootstrap diode 58 and bootstrap resistor 62 during activation of second switching unit 30 .

In the present case, the bootstrap unit 16 also includes an adjustment unit 18. The adjustment unit 18 is intended to change at least one parameter of the bootstrap unit 16. In the present case, the adaptation unit 18 is provided for changing the at least one parameter of the bootstrap unit 16 as a function of a voltage drop across the adaptation unit 18, which voltage corresponds to the bootstrap voltage V _B s .

The parameter is given by a charging time constant T, in particular the bootstrap capacity 60 . The charging time constant t results from:

T — RBoot ^' CBoot A variable R _ßoot corresponds to the resistance value of bootstrap resistor 62, while a variable C _ßoot corresponds to the capacitance value of bootstrap capacitor 60.

In the present case, the adjustment unit 18 is provided to dynamically adjust the capacitance value of the bootstrap capacitance 60 and in particular during operation of the household appliance device 10 . Alternatively, it is also conceivable to dynamically adapt a resistance value of a bootstrap resistor or a capacitance value of a bootstrap capacitance.

In the present case, the parameter has a value between 1 10 ⁸ s and 1 10 ⁶ s in the starting operating state. If the bootstrap voltage V _B s exceeds a limit value of approximately 12 V, the adjustment unit 18 is provided to change a value of the parameter, for example by switching between at least two capacitors of the bootstrap capacitance 60. In a continuous operating state, the parameter has a higher value than in the startup mode. In the continuous operating state, the parameter has a value between 10 ⁶ s and 10 ^-4 s. As a result, a rapid response behavior of first switching unit 12 can be achieved in the starting operating state, since bootstrap capacitance 60 already reaches a required voltage limit value for a first switching pulse, which is required for operating first driver 50 . In the continuous operating state, on the other hand, an advantageous filter effect can be achieved by increasing the charging time constant t. In particular, the bootstrap capacitance 60 and the bootstrap resistance 62 correspond to a low-pass filter. In the continuous operating state, voltage peaks in the supply voltage of the first driver 50, in particular due to the creepage voltage VLEAK, can be filtered, in particular by adapting the charging time constant T of the bootstrap unit 16 by the adapting unit 18. As a result, destruction and/or a reduction in the operating time of the first driver 50 as a result of an excessive operating voltage can be prevented. Alternatively, however, it is also conceivable to provide an additional filter unit in a household appliance device, for example between a secondary energy source and a bootstrap unit, which is and/or is bridged in particular in a starting operating state.

Concrete exemplary embodiments of the bootstrap unit 16 are shown in FIGS. In the present case, the bootstrap resistor 62 consists of a single resistor component. The bootstrap resistor 62 has an, in particular fixed, resistance value of 15 W. The bootstrap capacitance 60 includes two capacitors 90, 92. A first capacitor 90 of the capacitors 90, 92 has a capacitance value of 2.2 pF. A second capacitor 92 of the capacitors 90, 92 has a capacitance value of 68 nF. The matching unit 18 has a bypass switching element 94 with a diode 84 connected in parallel. The bypass switching element 94 is in the form of an n-channel MOSFET. Furthermore, the matching unit 18 includes a zener diode 86. The zener diode 86 is designed as a blocking element. Zener diode 86 is provided to block bypass switching element 94 below a voltage limit of approximately 12V. In addition, the adjustment unit 18 includes a resistor 88 which defines an operating point of the bypass switching element 94 .

A first connection of the first capacitor 90 is electrically conductively connected to a first supply voltage connection of the first driver 50 . The first connection of the first capacitor 90 is electrically conductively connected to a cathode connection of the Zener diode 86 . Furthermore, the first connection of the first capacitor 90 is connected to the bootstrap resistor 62 . A second terminal of the first capacitor 90 is electrically conductively connected to a drain terminal of the bypass switching element 94 . Furthermore, the second connection of the first capacitor 90 is connected to a first connection of the second capacitor 92 . Accordingly, the capacitors 90, 92 are connected in series. The first connection of the second capacitor 92 is thus also electrically conductively connected to the drain connection of the bypass switching element 94 . Furthermore, a second connection of the second capacitor 92 is electrically conductively connected to a second supply voltage connection of the first driver 50 . The second connection of the second capacitor 92 is electrically conductively connected to a source connection of the bypass switching element 94 . In addition, the second connection of the second capacitor 92 is electrically conductively connected to a second connection of the resistor 88 .

An anode connection of the Zener diode 86 is also electrically conductively connected to a base connection of the bridging switching element 94 . The anode connection of the Zener diode 84 is also electrically conductively connected to a first connection of the resistor 88 . In a starting operating state, a capacitance value of the bootstrap capacitance 60 is given by an effective capacitance value from the capacitances of the two capacitors 90, 92. In the present case, the effective capacitance value in the starting operating state is approximately 66 nF. In the starting operating state, a charging time constant t of the bootstrap unit 16 is approximately 1 ps. Above the voltage limit value, the Zener diode 86 reaches its forward range, so that the bypass switching element 94 switches on. Accordingly, the adjustment unit 18 is designed to be self-controlling and, in particular, is not connected to the control unit 36. Alternatively, however, it is also conceivable to control an adjustment unit by means of a signal from a control unit. In the continuous operating state, the bypass switching element 94 is provided to bypass the second capacitor 92 . The effective capacitance value in the continuous operating state is therefore 2.2 pF. In the steady state, a charging time constant T of the bootstrap unit 16 is about 33 ps.

FIG. 5 shows a schematic electrical circuit diagram of bootstrap unit 16 with matching unit 18 and a voltage limiting unit 20. Voltage limiting unit 20 is provided for limiting a voltage drop across matching unit 18, which voltage corresponds to bootstrap voltage VBS in the present case. The voltage limiting unit 20 is arranged electrically in parallel with the matching unit 18 .

The voltage limiting unit 20 has at least one energy store 22 . The energy store 22 is arranged electrically in parallel with the adjustment unit 18 . The energy store 20 has at least one storage capacitor unit 24 . The storage capacitor unit 24 has a capacitance between 10 nF and 1 pF. In the present case, the storage capacitor unit 24 has precisely one storage capacitor 96, the capacitance of which is between 10 nF and 1 pF.

The voltage limiting unit 20 has at least one semiconductor switching element 26 . The semiconductor switching element 26 is provided for the purpose of producing or separating an electrically conductive connection between the matching unit 18 and the energy store 22 as a function of a threshold value of the voltage VBS dropping across the matching unit 18 . In the present case, the semiconductor switching element 26 is provided to ensure that the electrically conductive connection between the adjustment unit 18 and the energy store 22 is below the threshold value of the adjustment unit 18 produce falling voltage VBS and above the threshold value of the voltage dropping across the adjustment unit 18 VBS ZU disconnect. The threshold value of the voltage VBS dropping across the matching unit 18 is preferably slightly above the optimal supply voltage of the first driver 50. It can therefore be ensured by means of the semiconductor switching element 26 of the voltage limiting unit 20 that the optimal supply voltage of the first driver 50 is not exceeded.

A collector connection of the semiconductor switching element 26 is electrically conductively connected to the bootstrap resistor 62 . In addition, the collector connection of the semiconductor switching element 26 is electrically conductively connected to a first connection of the storage capacitor 96 of the storage capacitor unit 24 of the energy store 22 . An emitter connection of the semiconductor switching element 26 is electrically conductively connected to the first supply voltage connection of the first driver 50 . Furthermore, the emitter connection of the semiconductor switching element 26 is connected to the first connection of the capacitor 90 and to the cathode connection of the zener diode 86 .

The voltage limiting unit 20 has at least one Zener diode 28 . The Zener diode 28 is electrically conductively connected to a control electrode, that is to say a base connection, of the semiconductor switching element 26 . In the present case, a cathode connection of the Zener diode 28 is electrically conductively connected to the control electrode of the semiconductor switching element 26 . An anode connection of the Zener diode 28 is electrically conductively connected to a second connection of the storage capacitor 96 of the storage capacitor unit 24 of the energy store 22 . The voltage limiting unit 20 has a variable capacitor 98 and a variable resistor 100 which are connected in series with one another. The variable capacitor 98 and the variable resistor 100 are arranged electrically in parallel with the storage capacitor 96 of the storage capacitor unit 24 of the energy store 22 . The control capacitor 98 is arranged electrically in parallel with the zener diode 28 . The control capacitor 98 is intended to achieve a uniform stray capacitance of the zener diode 28, which can vary depending on the manufacturer of the zener diode 28. The Regelkonden capacitor 98 has a capacity between 10 pF and 100 nF, depending on the Zener diode 28 used. In principle, it is conceivable that the control capacitor 98 can be dispensed with if the stray capacitance of the Zener diode 28 used is already at a desired level has value. The variable resistor 100 is provided to limit a current flow through the Zener diode 28 .

The threshold value of the voltage VBS dropping across the matching unit 18 is characterized by a breakdown voltage of the Zener diode 28 . The electrically conductive connection between the matching unit 18 and the energy store 22 via the collector connection and the emitter connection of the semiconductor switching element 26 only exists if the voltage V _B s, which drops between the emitter connection of the semiconductor switching element 26 and the center tap 44, is lower than the sum from the breakdown voltage of the Zener diode 28 and the base-emitter voltage of the semiconductor switching element 26. In the present case, the Zener diode 28 has a breakdown voltage of 20V. The semiconductor switching element 26 requires a base-emitter voltage of approximately 0.6 V so that it becomes conductive and a current can flow between the collector connection and the emitter connection. If the voltage VBS exceeds the breakdown voltage of the Zener diode 28, it becomes conductive in the reverse direction, so that there is no longer sufficient base-emitter voltage at the semiconductor switching element 26 and the semiconductor switching element 26 separates the electrically conductive connection between the matching unit 18 and the energy store 22. The threshold value of the voltage VBS dropping across the matching unit 18 is therefore characterized by the breakdown voltage of the Zener diode 28 .

Thus, the voltage limiting unit 20 is designed to be self-controlling. A connec tion of the voltage limiting unit 20 with the control unit 26 and a control of the voltage limiting unit 20 by the control unit 36 is therefore not required Lich.

FIG. 6 shows a schematic process flow diagram of a process for operating the household appliance device 10. In the process, the voltage V _B s dropping across the matching unit 18 is automatically limited. The method comprises at least two method steps. In a first method step 102 of the method, the household appliance device 10 is switched on and supplied with energy via the main energy source 40 . In the first method step 102, the household appliance device 10 is operated in the starting operating state and the switching units 12, 30 are switched alternately by the control unit 36. For this purpose, the drivers 50, 52 are controlled alternately by the control unit. In the starting operating state are the capacitor 90 and the capacitor 92 are connected in series, so that an effective capacitance value of the bootstrap unit 16 is low and is approximately 66 nF in the present case. In the starting operating state, a low charging time constant t of the bootstrap unit 16 of approximately 1 ps in the present case is thus also achieved. As soon as the bootstrap voltage V _B s dropping across the matching unit 18 exceeds the breakdown voltage of the Zener diode 84, which is 12 V in the present case, it becomes conductive in the reverse direction, so that the capacitor 90 is bypassed by the bypass switching element 94. This point in time represents both a transition from the starting operating state to the continuous operating state of the household appliance device 10 and a transition from the first method step 102 to a second method step 104 of the method. In the second method step 104, the household appliance device 10 is operated in the continuous operating state. where the capacitor 92 of the matching unit 18 is bridged, so that the effective capacitance value of the bootstrap unit 16 is set to 2.2 pF and the charging time constant t of the bootstrap unit 16 is approximately 33 ps. As soon as the bootstrap voltage VBS dropping across the matching unit 18, for example due to superimposition by the leakage voltage VLEAK, reaches or exceeds the breakdown voltage of the Zener diode 28 of 20 V, the connection between the matching unit 18 and the energy store 22 and the secondary energy source 48 is broken the semiconductor switching element 26 separately. As a result, the bootstrap voltage VBS dropping across the matching unit 18 is automatically limited.

Reference sign

10 home appliance device

12 switching unit

14 driver circuit

16 bootstrap unit

18 adjustment unit

20 Voltage Limiting Unit

22 energy storage

24 storage capacitor unit

26 semiconductor switching element

28 zener diode

30 switching unit

32 household appliance

34 heating zone

36 control unit

38 heating unit

40 main energy source

42 inverters

44 funds tap

46 resonance unit

48 secondary energy source

50 drivers

52 drivers

54 conduction path

56 bulk capacitor

58 bootstrap diode

60 bootstrap capacity

62 bootstrap resistance

64 conduction path 66 abscissa axis

68 ordinate axis

70 curve

72 curve

74 curve

76 curve

78 curve

80 curve

82 curve

84 diodes

86 zener diode

88 resistance

90 condenser

92 condenser

94 bypass switching element

96 storage capacitor

98 control capacitor

100 rheostat

102 first process step

104 second process step

106 hob plate

CB _OOI variable

reoot variable

T charging time constant

VBS bootstrap voltage

Vo mains voltage potential

Vi_ _eak creep voltage

Claims

Expectations

1. Household appliance device (10), in particular induction cooking device device, with at least one switching unit (12, 30) and with at least one driver circuit (14), which is intended to set a control voltage for the switching unit (12, 30) and which has a bootstrap unit ( 16) which comprises an adjustment unit (18) which is intended to change at least one parameter of the bootstrap unit (16), characterized in that the bootstrap unit (16) has a voltage limiting unit (20) for limiting a voltage across the adjustment unit (18) falling bootstrap voltage (VBS).

2. Household appliance device (10) according to claim 1, characterized in that the voltage limiting unit (20) has at least one energy store (22) which is arranged electrically in parallel with the adjustment unit (18).

3. Household appliance device (10) according to claim 2, characterized in that the energy store (22) has at least one storage capacitor unit (24).

4. Household appliance device (10) according to claim 3, characterized in that the storage capacitor unit (24) has a capacitance between 10 nF and 1 pF.

5. Household appliance device (10) according to any one of the preceding claims, characterized in that the voltage limiting unit (20) is designed to be self-controlling.

6. Household appliance device (10) according to one of the preceding claims, characterized in that the voltage limiting unit (20) has at least one semiconductor switching element (26) which is intended to establish an electrically conductive connection between the adaptation unit (18) and the energy store (22 ) depending on a threshold value of the bootstrap voltage (V _B s) dropping across the adjustment unit (18) or to be separated.

7. Household appliance device (10) according to claim 6, characterized in that the voltage limiting unit (20) has at least one Zener diode (28) which is electrically conductively connected to a control electrode of the semiconductor switching element (26).

8. Household appliance device (10) according to claim 7, characterized in that the threshold value of the voltage drop across the matching unit (18) (VBS) is characterized by a breakdown voltage of the Zener diode (28).

9. Household appliance device (10) according to one of the preceding claims, characterized in that the adjustment unit (18) is provided to change the at least one parameter of the bootstrap unit (16) as a function of the bootstrap voltage (VBS) dropping across the adjustment unit (18). other

10. Household appliance (32), in particular induction cooking appliance, with at least one

Household appliance device (10) according to one of the preceding claims.

11. Method for operating a household appliance device (10), in particular according to one of Claims 1 to 9, having at least one switching unit (12, 30) and having at least one driver circuit (14) which is intended to generate a control voltage for the switching unit (12 , 30) and which has a bootstrap unit (16) which comprises an adjustment unit (18) which is intended to change at least one parameter of the bootstrap unit (16), characterized in that a bootstrap voltage dropping across the adjustment unit (18). (V _B s) is automatically limited.