DE8817041U1 - Circuit arrangement for electric stoves - Google Patents

Description

BOSCH-SIEMENS HOUSEHOLD APPLIANCES (&Idigr;&Mgr;&Bgr;&EEgr; 8000 Munich 80, 03.12.1991

Hochstrasse 17

TZP91P629
Thi/si

Circuit arrangement for electric stoves

The invention relates to a circuit arrangement for electric cookers with electrically operated heating elements for
Heating power control, whereby the heating power for a
Continuous heating phase by means of a control device to a
by pulsing the heating current to a predetermined value
maximum value for a boiling phase can be set.

For controlling electrically operated hotplates and
Other electrically operated heating systems are known to use a unit called an energy regulator. For example, DE-OS 32 04 599 discloses that
To provide a constant heating output during the start-up phase of the energy-controlled heating points.

The known control devices for energy regulation
on the one hand and for the pre-cooking power on the other hand work in parallel.

The object of the invention is to provide an electronic circuit arrangement which, as additional electronics to the energy regulator, implements a time-controlled automatic boil-up function and at the same time minimizes the necessary control power. The solution to this problem is characterized by the fact that an electronic automatic boil-up function equipped with minimized energy consumption is used as additional electronics

&ogr;

TZP91P629

technology of an energy regulator is arranged, which provides the maximum heating power during the boiling phase for a programmable duration, based on a preselected heating level, whereby an electronic component equipped with customer-specific degrees of freedom controls the electronic automatic boiling. Further advantageous embodiments of the invention are contained in the subclaims.

An embodiment of the invention is described in more detail below with reference to the drawing. It shows:

Fig. la a circuit arrangement for a heating power control,

Fig. Ib an embodiment of an adjustable series resistor RN,

Fig. 2a an embodiment of a rotary coding switch block,

Fig. 2b a schematic diagram for an automatic boil-up system,

Fig. 3 is a schematic diagram of an electronic component for automatic boiling.

According to the circuit arrangement in Fig. la, the mains supply voltage is applied via the lines Ll and L2. The mains switch combination Sl, S2 is closed when the heating point is started up. The associated bimetal switch SE is closed with the mains switch combination Sl, S2 via the energy regulator ER. The heating resistor RS belonging to SE switches the switch after a sufficiently long heating period.

TZP91P629

ter SE and thus cycles the heating current through the hob heater RH in the known manner, provided that the bimetal switch SZ is closed.

However, this timing is prevented during the boiling phase. In this phase, the bimetal switch SZ is open and the cooking zone heating RH is continuously supplied with maximum power. The current flowing through RV, RZ and RT heats the bimetal switch SZ via RZ. RV, RZ and RT are dimensioned so that SZ is closed after the boiling phase. The heating current now flowing via RS leads to SE opening, whereby the consumer current via RH and the heating current via RS are set to zero. As a result, RS cools down, SE closes and the currents via RH and RS flow again. SZ remains closed during this phase. In this way, the consumer current via RH is clocked as determined by RS. Since the series connection RV, RZ and RT determines the duration of the boiling phase, the power loss occurring after this phase during the cooking time is also determined by RV, RZ and RT.

According to Fig. 1b, the switching level for the adjustable series resistor RV is visible. In the present case, the sub-areas RVl, RV2 and RV3, which are contacted in a known manner via sliding contacts, are shown.

According to Fig. 2a, the switching levels of four rotary coding switches 2, which are combined in a structural unit as a rotary coding switch block, are shown. According to Fig. 2b, a basic circuit diagram for an electronic automatic boil-start system is shown.

TZP91P629

An electronic module 1 is connected on the input side to four rotary coding switches 2, which are operated by four cooking zone setting controls 3. Furthermore, a series-stabilized power supply 4, a clock generator 5 derived from the mains frequency and a programmable cable bundle 6, which is led to a prescaler of the electronic module 1, are connected on the input side to the electronic module 1. On the output side, the electronic module 1 is led to four triacs of the triac stages 7, corresponding to the cooking zone display of the usual blocks of four, which are connected to the block of four 8. The electronic automatic heating is assigned to the existing energy regulators of the blocks of four as additional electronics. The electronic automatic heating can be used to control the maximum power for a certain preselectable period, based on a set heating level.

The electronic automatic boiling function is set by turning the position 9 on the hotplate setting control 3 to position A (boiling) and then turning it back to the desired power level. The selected position on the respective hotplate setting control 3 is checked using the rotary coding switch 2, which works in grey code. The electronic module 1 receives the signals multiplexed from the rotary coding switch 2 and processes them internally. The total number of input lines is not shown in Fig. 2b to maintain clarity, the input paths are therefore generally to be interpreted as a line bundle (BUS). The four output lines of the electronic module 1 to the triac stage 7 correspond to the conditions of the usual four-block system with four hotplates. For the hotplates that are subject to a boiling time, the corresponding triac is

TZP91P629

the triac stage 7 is blocked by the electronic module 1, which in terms of circuitry means that the hotplate heating is supplied with maximum power. After the boiling time has elapsed, the system switches to continued boiling, the blocked triacs are controlled, i.e. the controlled hotplate power corresponds to the setpoint of the control characteristic of the energy regulator.

Fig. 3 shows the basic structure of the electronic module 1. The input signals originating from the rotary coding switches 2 and applied by a multiplexer M of the electronic module 1 are fed to a code converter (Ko). The code converter decodes the grey code into the dual code and relates the converted input signals to specific boiling times in minutes, as they correspond to the position of the setting controls on the cooking area. At the same time, the multiplexer M has activated a buffer L and the current value of the code converter is adopted. The buffer content is entered into an evaluator A. The evaluator A provides a signal QN for N=0, 1, 2, 3 at the respective output. The signal QN blocks the corresponding triac of the triac stage 7 for the duration of the boiling time of the cooking area used. The evaluator A finds the end of the boiling time using a comparator signal. A comparator Vg compares the input values of the encoder Ko with enumerated time values that a divider Te, which is clocked by a programmed prescaler P, generates in a four-bit counter Z. If the two time values are identical, the comparator Vg passes an end signal to the evaluator A and the triac stage is enabled. A Schmitt trigger ST supplies the clock frequency, which is provided by the clock generator 5 on the input side, to the multiplexer M and the programmable prescaler P. Via the programmed

TZP91P629

In line bundle 6, the internal clock signal for the dividers Te can be varied by the prescaler P in seven steps between 2.88 and 4.80 seconds cycle time. For testing purposes, a fast run with 0.32 seconds cycle time is provided.

Claims (8)

TZP91P629 Claims 1. Circuit arrangement for electric stoves with electrically operated heating points for heating power control, wherein the heating power for a continuous heating phase can be set by means of a control device to a value predetermined by timing the heating current and for a pre-boiling phase to a maximum value, characterized in that an electronic automatic pre-boiling system equipped with minimized energy consumption is arranged as additional electronics of an energy regulator, which provides the maximum heating power during the pre-boiling phase for a programmable duration, based on a preselected heating level, wherein an electronic module (1) equipped with customer-specific degrees of freedom controls the electronic automatic pre-boiling system. 2. Circuit arrangement according to claim 1, characterized in that the electronic module (1) is connected on the input side to a rotary coding switch (2) for each cooking point. 3. Circuit arrangement according to claim 1, 2, characterized in that the rotary coding switch (2) queries mechanically preselected switch knob positions. 4. Circuit arrangement according to claim 1, characterized in that the electronic component (1) is variably clocked by programming inputs (6). 5. Circuit arrangement according to claim 1, characterized in that the electronic component (1) is connected on the input side to a clock generator (5). TZP91P629 6. Circuit arrangement according to claim 1, 5, characterized in that the clock generator (5) uses the mains frequency. 7. Circuit arrangement according to claim 1, characterized in that the electronic component (1) is connected on the output side to a triac stage (7). 8. Circuit arrangement according to claim 1, characterized in that the triac stage (7) separates the energy regulator from the cooking zone heating for the duration of the pre-cooking phase in a cooking zone-specific manner.