EP2101543B1 - Device and method for controlling induction heaters of an induction hob - Google Patents

Description

The invention relates to a device and a method for controlling or supplying power to induction heating devices of an induction hob, so-called induction coils. The power supply of these induction heaters via the mains or a mains phase thereof, wherein a filter unit and the filter unit is provided on a rectifier unit with at least one inverter and a DC link. In this case, a rectifier unit with two inverters in the rectifier unit are advantageously connected to a filter unit so that one induction heater is driven or supplied with power per inverter.

Conventional induction generators or devices for cooktops are optimized for two or four induction coils or hobs. Devices with one or three hotplates are realized by omitting an inverter or by operating a two-circuit cooking zone by means of two-speed converters. Systems with four cooking zones are realized by parallel construction of two two-unit units. Five or six systems respectively use three two-unit units or a four-unit unit in combination with a two-unit unit.

A generator basically includes the inverters that generate the high frequency and a filter. Filter and inverter can be constructed on a printed circuit board or separately, but always a converter unit with one or more induction coils, typically two induction coils, permanently associated with a filter unit. Each filter unit can be connected separately to a mains phase. If fewer phases of the network are available than filter units, the filter units are always connected together on the network side.

It is also known that a single converter is switched alternately by means of relay switching to a plurality of induction coils or a plurality of heating circuits of an induction coil. It is also known that two or more inverters, which may also be located in different converter units, can be permanently connected to different partial coils of a multi-circuited induction coil.

In case of alternating use of a converter for two induction coils, a converter can be saved. However, only one induction coil can be supplied with power at the same time.

If the inverter is switched alternately in short time intervals on both induction coils, as it is from the DE 3712242 A1 is known, so there are disadvantages in cooking picture such as swells and swells when boiling water. In addition, caused by the mechanical switching of the relay regular annoying clacking noises. The resulting flicker when switching is a disadvantage.

On the other hand, if the converter is assigned stationarily via a relay to an induction coil, as is known from US Pat EP 1 194 008 A2 and the WO 2004/014 106 A1 is known, so that a further induction coil is stationary without inverter connection, the induction coil can not be supplied with power and the corresponding hotplate remains cold. An advantage of this solution is that no regularly occurring clack noise arises and the working noise is quieter, provided that the two converters of the multi-circuit induction heater are frequency synchronized with each other.

The JP 2003-282226 A describes a generic device for controlling induction heating of an induction cooktop with a filter unit, a rectifier unit, a plurality of converters and a DC link. In this case, the structure of the drive for each induction coil of the induction heaters is the same.

Task and solution

The invention has for its object to provide an aforementioned device and a method for power supply or control of induction heating, with which problems of the prior art can be avoided and in particular advantageously an additional induction heater can be controlled with the least possible Effort.

This object is achieved by a device having the features of claim 1 and a method having the features of claim 8. Advantageous and preferred embodiments of the invention are the subject of further claims and are explained in more detail below. Here are some of the listed below Features described only for the device or only for the procedure. However, they should apply independently to both the device and the method. The wording of the claims is incorporated herein by express reference. Furthermore, the text of the German priority application DE 102008015036.3 of March 14, 2008, the same assignee by expressly referring to the content of the present description.

According to the invention, provision is made for an additional induction heater which is connected behind one of the existing filter units to be provided for a further induction heating device which is to be controlled by the device or the method and to be supplied with power. Thus, it is thus provided in the invention that no additional filter unit is provided for an additional inverter of a further induction heater even when already fully occupied filter units, but this additional inverter is connected behind it. In an advantageous embodiment of the invention, a total of two filter units are provided, each of them supply a rectifier unit, each with two inverters. To each of these inverters an existing induction heater is connected.

In a first basic embodiment of the invention, the additional converter can be connected without a rectifier to an intermediate circuit of an existing, connected to the filter unit rectifier unit, in particular directly connected. Furthermore, this connection can again be made via switching means similar to the above. In yet another embodiment of the invention, the additional converter without rectifier can be connected via switching means to a plurality of intermediate circuits of a plurality of rectifier units. An alternating power supply of the additional converter via the connection of different intermediate circuits can be carried out according to the same principles as described above for the connection of the additional converter to a filter unit.

Furthermore, it is also possible in the aforementioned embodiment of the invention that not only an additional inverter for an additional induction heating, but a plurality of additional inverter for each additional induction heating to the DC link be connected by existing rectifier units. This can advantageously be done via switching means, as this allows an advantageous possibility for power supply from a plurality of rectifier units or multiple filter units.

In another basic embodiment of the invention can be provided that the additional converter for the additional induction heater is connected together with a rectifier unit for it between a filter unit and an existing rectifier unit with the inverters. In particular, the additional converter can be connected directly to a connection between the filter unit and rectifier unit. In this case, it is advantageously possible to connect the additional converter via a switching means, for example a relay, to such a connection between filter unit and rectifier unit. Particularly advantageously, it is possible to connect the additional converter via the switching means not only to a connection of a filter unit with a rectifier unit, but to the connections of several filter units, each with their dedicated rectifier units. Thus, it is possible, as will be explained in more detail below, that the additional converter is connected, as it were, to one or another filter unit via the switching means, depending on the still available power reserve of the filter unit. In particular, the additional converter for the additional induction heating device can in each case be connected to that filter unit which at this moment has a lower power output for its existing induction heating devices, that is to say even a larger power reserve.

In this case, it is still possible, even with insufficient residual power even of this less loaded filter unit to operate the additional induction heater with reduced power, so that a maximum allowable power, especially a short-term maximum allowable performance of the filter unit is maintained. In again According to a further embodiment of the invention, such power reduction may be made predominantly in the additional induction heater, but also in one of the existing induction heating of the filter unit. Thus, the quasi-necessarily necessary power reduction can be distributed to several induction heaters, so that they do not particularly strong or negative noticeable in any of them. Possible methods for such a power reduction are those skilled in the DE 10 2005 045 875 A1 the contents of which are hereby incorporated by express reference into the content of the present description.

In a further embodiment of the invention, it is possible to apply additional power to additional heating devices, each having two or more associated induction coils as so-called two-circuit heaters or multi-circuit heaters so that the power comes from an existing first rectifier unit for a first induction coil , For a second or further induction coil, which is advantageously a switchable to the first induction coil heater, the power can come from a pre-described additional converter, which is connected to switching means with one of the intermediate circuits of the existing rectifier units. Alternatively, the power supply of the second induction coil can come via an additional converter with rectifier unit, which is connected to an existing filter unit.

In yet another embodiment of the invention can be advantageously provided that the inverter operated frequency synchronized. Thus, interference noise between the induction heaters can be avoided.

These and other features are apparent from the claims and from the description and drawings, wherein the individual Characteristics may be implemented on their own or in combination in the form of sub-combinations in one embodiment of the invention and in other fields and may represent advantageous and protectable embodiments for which protection is claimed here. The subdivision of the application into individual sections as well as intermediate headings does not restrict the general validity of the statements made thereunder.

Brief description of the drawings

Fig. 1

eine Darstellung eines Anschlusses einer zusätzlichen Gleich- richtereinheit für eine zusätzliche Induktionsheizeinrichtung über Schaltmittel an beide bestehenden Filtereinheiten,

Fig. 2

eine Abwandlung der Darstellung aus Fig. 1 mit dem Anschluss über die Schaltmittel an die Zwischenkreise zweier vorhandener Gleichrichtereinheiten,

Fig. 3

den Anschluss einer zusätzlichen Induktionsheizeinrichtung als Zweikreis-Spule mit einer Induktionsspule an eine bestehende Gleichrichtereinheit und der anderen Induktionsspule an einen zusätzlichen Umrichter,

Fig. 4

eine weitere Abwandlung, bei der eine zweifache zusätzliche Umrichtereinheit über Schaltmittel an Zwischenkreise zweier be- stehender Gleichrichtereinheiten angeschlossen wird für zwei zusätzliche Induktionsheizeinrichtungen und

Fig. 5

eine Abwandlung der Darstellung aus Fig. 4, bei der zwei sepa- rate zusätzliche Umrichter für jeweils eine zusätzliche Indukti- onsheizeinrichtung über jeweils ein eigenes Schaltmittel an bei- de Zwischenkreise beider bestehender Gleichrichtereinheiten angeschlossen sind.

Embodiments of the invention are shown schematically in the drawings and will be explained in more detail below. In the drawings show:

Fig. 1

a representation of a connection of an additional rectifier unit for an additional induction heating device via switching means to both existing filter units,

Fig. 2

a modification of the presentation Fig. 1 with the connection via the switching means to the intermediate circuits of two existing rectifier units,

Fig. 3

the connection of an additional induction heating device as a two-circuit coil with an induction coil to an existing rectifier unit and the other induction coil to an additional converter,

Fig. 4

a further modification in which a two-fold additional converter unit is connected via switching means to intermediate circuits of two existing rectifier units for two additional induction heating devices and

Fig. 5

a modification of the presentation Fig. 4 , in which two separate additional converters for each additional induction heating device are connected via respective switching means to both intermediate circuits of both existing rectifier units.

Detailed description of the embodiments

In Fig. 1 a device 11a is shown for driving induction heating devices 14a to 17a. These induction heating devices 14a to 17a are part of an induction hob 12a shown in dashed lines, as for example from the above-mentioned WO 2004/014106 A1 is basically known. The induction heating devices 14a to 17a each have induction coils 14'a to 17a, which are shown schematically, or are formed by these. This realization is no problem for the skilled person.

The device 11a has two filter units 23a and 24a, which are connected to a power grid 21, in particular a two-phase power grid. Although the filter units 23a and 24a are shown together, they may be separate components. Advantageously and usually they are arranged on the same circuit board or in the same housing. On the left filter unit 23a, a first rectifier unit 26a is connected. This has a rectifier 27a, which feeds two converters 28a and 29a, via an intermediate circuit, not shown, but this is usually done and also emerges from the aforementioned prior art. In this case, the inverter 28a feeds the induction heater 14a and the inverter 29a feeds the induction heater 15a, and the inverters are respectively responsible for the power supply of the induction heaters.

The right filter unit 24a accordingly feeds a second rectifier unit 31a having a rectifier 32a and two inverters 33a and 34a which in turn power the induction heaters 16a and 17a. In that regard, the device described corresponds to the state of the art for driving the four induction heating devices 14a to 17a via four inverters 28a, 29a, 33a and 34a.

If, however, an additional induction heater 18a with corresponding induction coil 18'a is to be supplied with power in the induction hob 12a, this is difficult in itself. Although it could be connected via a switching means to an output of one of the inverter, but then the other, usually supplied by this inverter induction heater could not be supplied with power.

Therefore, according to the invention, a switching means 36a is connected to the connections of both rectifier units 26a and 31a with their respective filter unit 23a and 24a, ie behind the filter units. The switching means 36a can connect to the supply of one of the filter units, depending on the current power requirement situation. The switching means 36a feeds an additional converter 38a. This in turn ensures the power supply for the additional induction heater 18a. Im in Fig. 1 In the illustrated case, the switching means 36a is connected to the right filter unit 24a. This means that the total power required by the induction heaters 16a, 17a and 18a may not exceed the total power that the filter unit 24a can provide to a maximum, for example even in the short term. In this case, the above-described power sharing methods are applied between the three induction heaters set by the inverters 33a, 34a and 38a, respectively. Alternatively, if the filter unit 24a is overloaded, it is possible to switch to the possibly still left-hand filter unit 23a.

An additional converter thus basically switches over the switching means to the filter unit or rectifier unit which is more suitable at this moment. Through frequency or phase control, the desired power of each induction heater can be adjusted by the inverter.

In Fig. 2 is a modification of the device Fig. 1 shown as a device 11 b. The difference here is that the additional switching means 36b is no longer connected directly to the filter units 23b and 24b, but to the intermediate circuits, not shown, of the first rectifier unit 26b and the second rectifier unit 31b. This means that then also the additional rectifier according to Fig. 1 is no longer necessary because the connection is just made directly to the DC link of the existing rectifier units. Otherwise, the same applies here as before for the function and use of the switching means 36. In addition, however, the maximum available total power of the rectifier units or the associated DC link must also be taken into account.

In Fig. 3 is a further modification of a device 11 c shown, which again essentially that of Fig. 2 corresponds, ie with the additional switching means 36 c connected to the intermediate circuits of the first rectifier unit 26 c and second rectifier unit 31 c. Furthermore, in Fig. 3 the existing induction heater 17c and the corresponding induction coil, the inner part of a two-circuit heater. The outer part surrounding the inner part is formed by the additional induction heater 18c with the corresponding induction coil. This additional induction heater 18c is powered by an additional inverter 38c. Thus, although the two induction heaters 17c and 18c form the same hotplate for an induction hob, they are fed from different inverters and, if the additional inverter 38c is connected to the left rectifier unit 26c via the switching means 36c, even across different filter units and different rectifier units. The distribution of the power can be advantageous in this case, however, since in a two-circuit operation of the two-circuit heater large power is needed and then belonging to the same rectifier unit 31 c induction heater 16c probably not or only with very low power could be operated. Otherwise, the same rules for a power distribution apply as described above.

In the further device 11 d according to Fig. 4 two additional inverters 38d and 39d are connected to a switching means 36d. In this case, the additional inverter 38d feeds the additional induction heater 18d and the additional converter 39d feeds the additional induction heater 19d. Thus, an induction hob with six induction heating 14d to 19d and thus also six cooking zones can be constructed here. Both additional induction heaters 18d and 19d can thus be connected via additional inverters 38d and 39d and the switching means 36d to one of the intermediate circuits of the existing rectifier units 26d and 31d. In this respect, performance management is of great importance.

In Fig. 5 Finally, a device 11 e is shown. In a modification of the device Fig. 4 Here, two additional switching means 36e and 40e are provided, which are respectively connected to both intermediate circuits of the existing rectifier units 26e and 31 e. The switching means 36e is connected to an additional converter 38e, which feeds an additional induction heater 18e from the intermediate circuit of one of the rectifier units. The additional switching means 40e connects the additional inverter 39e to one of the intermediate circuits of the existing rectifier units for supplying power to the additional induction heater 19e.

With the device 11 e according to Fig. 5 can therefore be more advantageous than with the device 11 d in Fig. 4 each of the inverters 38e and 39e for the induction heaters 18e and 19e are connected as needed via the switching means 36e and 40e to one of the intermediate circuits of the existing rectifier units 26e and 31e. In this respect, it is also possible that both converters 38e and 39e are connected to the same DC link if this is the set power as well as the power reserves of the relevant rectifier unit.

Claims (15)

1. A device (11a-e) for driving induction heating means (14a-e through 17a-e) of an induction hob (12a), power being supplied to the induction heating means via the electric power grid (21) or a grid phase thereof, a filter unit (23a-e, 24a-e) and a rectifier unit (27a-e, 32a-e) with at least one converter (28a-e, 29a-e, 33a-e, 34a-e) and intermediate circuit, for two induction heating means (14a-e through 17a-e) one rectifier unit and at least one converter, in particular two converters, being connected to one filter unit, characterized in that for a further induction heating means (18a-e, 19d-e) an additional converter (38a-e, 39d-e) is coupled downstream of one of the existing filter units (23a-e, 24a-e).
2. The device as claimed in claim 1, characterized in that a total of two filter units (23a-e, 24a-e) are provided, preferably each having one rectifier unit (27a-e, 32a-e) with in each case two converters (28a-e, 29a-e, 33a-e, 34a-e) for in each case one induction heating means (14a-e through 17a-e) per converter.
3. The device as claimed in claim 1 or 2, characterized in that the additional converter (38a-e, 39d-e) is connected without a rectifier, in particular directly to an intermediate circuit of an existing rectifier unit (27a-e, 32a-e) with converter, preferably via switching means (36a-e) to a plurality of intermediate circuits of rectifier units (27a-e, 32a-e).
4. The device as claimed in claim 3, characterized in that a plurality of additional converters (38a-e, 39d-e) are connected to intermediate circuits of a plurality of rectifier units (27a-e, 32a-e), preferably each additional converter being connected via switching means (36a-e) to the intermediate circuits of all the rectifier units.
5. The device as claimed in claim 1 or 2, characterized in that the additional converter (38a-e, 39d-e) is connected, together with a rectifier unit (27a-e, 32a-e), in particular directly to a connection between a filter unit (23a-e, 24a-e) and existing rectifier units with converters (28a-e, 29a-e, 33a-e, 34a-e), preferably via switching means (36a) to connections of a plurality of filter units (23a, 24a) with in each case one rectifier unit (27a, 32a).
6. The device as claimed in any of the preceding claims, characterized in that power is applied to additional induction heating means with two associated induction coils in such a way that for a first induction coil the power comes from an existing rectifier unit and for a second induction coil, which is preferably an additional induction coil to the first induction coil, the power comes from an additional converter with switching means, the switching means being connected to one of the intermediate circuits of the existing rectifier units.
7. The device as claimed in any of the preceding claims, characterized in that an additional converter (38a) is designed so as to connect the additional induction heating means (18a) to that filter unit (23a, 24a) which is producing relatively low power at that moment, preferably if the residual power of this filter unit is insufficient for the additional induction heating means, this additional induction heating means (18a) is operated with reduced power while complying with the maximum power of the filter unit (23a, 24a).
8. A method of driving the induction heating means (14a-e through 17a-e) of an induction hob (12a), wherein power is supplied to the induction heating means via the electric power grid (21) or a grid phase thereof, a filter unit (23a-e, 24a-e) and a rectifier unit (27a-e, 32a-e) with at least one converter (28a-e, 29a-e, 33a-e, 34a-e) and intermediate circuit, for two induction heating means one rectifier unit and at least one converter, in particular two converters, being connected to one filter unit, characterized in that for a further induction heating means (18a-e, 19d-e) of the induction hob an additional converter (38a-e, 39d-e) is coupled downstream of one of the existing filter units (23a-e, 24a-e).
9. The method as claimed in claim 8, characterized in that a total of two filter units (23a-e, 24a-e) are provided, preferably each having one rectifier unit (27a-e, 32a-e) with in each case two converters (28a-e, 29a-e, 33a-e, 34a-e) for in each case one induction heating means (14a-e through 17a-e) per converter.
10. The method as claimed in claim 8 or 9, characterized in that the additional converter (38a-e, 39d-e) is connected without a rectifier, in particular directly to an intermediate circuit of an existing rectifier unit (27a-e, 32a-e) with converter (28a-e, 29a-e, 33a-e, 34a-e), preferably via switching means (36a-e) to a plurality of intermediate circuits of rectifier units (28a-e, 32a-e).
11. The method as claimed in claim 10, characterized in that a plurality of additional converters (38a-e, 39d-e) are connected to intermediate circuits of a plurality of rectifier units (27a-e, 32a-e), wherein preferably each additional converter is connected via switching means (36a-e) to the intermediate circuits of all the rectifier units.
12. The method as claimed in claim 8 or 9, characterized in that the additional converter (38a-e, 39d-e) is connected, together with a rectifier unit (27a-e, 32a-e), to a connection between a filter unit (23a-e, 24a-e) and existing rectifier units with converters (28a-e, 29a-e, 33a-e, 34a-e), preferably via switching means (36a) to connections of a plurality of filter units (23a, 24a) with in each case one rectifier unit (27a, 32a).
13. The method as claimed in any of claims 8 through 12, characterized in that power is applied to additional induction heating means with two induction coils in such a way that for one induction coil the power comes from an existing rectifier unit and for the other induction coil, which is preferably an additional induction coil, the power comes via an additional converter with switching means connected to one of the intermediate circuits of the existing rectifier units.
14. The method as claimed in any of claims 8 through 13, characterized in that an additional converter (38a) connects the additional induction heating means (18a) to that filter unit (23a, 24a) which at that moment is producing relatively low power, preferably this additional induction heating means (18a) being operated with reduced power while complying with the maximum power of the filter unit (23a, 24a), if the residual power of this filter unit is insufficient for the additional induction heating means.
15. The method as claimed in any of claims 8 through 14, characterized in that all the converters (28a-e, 29a-e, 33a-e, 34a-e, 38a-e, 39a-e) are frequency-synchronized so as to avoid interference noise between the induction heating means (14a-e through 17a-e, 18a-e, 19d-e).

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