A converter circuit for an induction hob

Abstract

The invention relates to an induction hob comprising a cooktop (1); a first induction coil (2) provided on the cooktop (1) and at least one second induction coil (3); a main control board (10) connected to the first and at least second induction coils (2, 3); and a user interface (4) connected to the main control board (10) for signal transmission. The induction hob further comprises, on the main control board (10), a converter circuit (20) which contains, on the main control board, an electronic filter circuit (30) and a first impedance converter (22) and at least one second impedance converter (24) configured to provide a joint dynamic response to short-term and instantaneous current-voltage variations and frequency variations.

Description

[0001] A CONVERTER CIRCUIT FOR AN INDUCTION HOB

[0002] TECHNICAL FIELD

[0003] The present invention relates to a hob equipped with multiple heaters whose power consumption is regulated by an electronic control unit, and more particularly to induction hob.

[0004] BACKGROUND OF THE INVENTION

[0005] Frequency-selective filters used in the electronic circuits of induction hob pass signals that lie within permitted frequency bands and attenuate signals outside those bands. Consequently, noise signals and signals with a disturbing influence are suppressed while the circuit is operating. In circuits that employ dynamic-switching techniques, a fixed pass-band frequency or amplitude of the filter circuit can cause problems. In order to accommodate the behaviour of such dynamic circuits, filters whose response characteristics can change instantaneously have to be designed instead of fixed filters.

[0006] CN112886812B discloses a dynamic adjustment method and device of a DC-DC converter. The method comprises the steps of: S1 , acquiring electrical parameters of the DC-DC converter; S2, judging whether the electrical parameters are the same as the reference value or not, if so, returning to the S1 , and if not, acquiring a control signal according to the electrical parameters and the reference value; S3, inputting the control signal to a controlled source to enable the controlled source to generate a corresponding control current; and S4, increasing the magnetic induction intensity of a magnetic core in a control winding of the output end of the controlled source through the control current so as to increase the saturation degree of the magnetic core and influence the effective magnetic conductivity of the magnetic core, thus changing the inductance value of an inductor wound on the magnetic core, further changing the impedance of the DC-DC converter, adjusting the electrical parameters through the adjusted impedance, and returning to S1.

[0007] BRIEF SUMMARY OF THE INVENTION

[0008] The object of the invention is to provide a converter circuit for an induction hob that produces a dynamic response without the need for external passive components. In order to achieve this object, the invention concerns an induction hob that comprises a cooktop; a first induction coil provided on the cooktop; at least one second induction coil; a main control board connected to the first and the at least one second induction coils; and a user interface connected to the main control board for signal transmission. The induction hob further comprises, on the main control board, a converter circuit that contains a first impedance converter and at least one second impedance converter arranged so that, together with an electronic filter circuit, they provide a joint dynamic response to short-term and instantaneous current-voltage variations and frequency variations. In this way the filters are able to react dynamically to changes within the circuit. Dispensing with external passive components also yields a cost advantage.

[0009] In a preferred embodiment the filter circuit contains a resistor, a capacitor and an inductor that are interconnected for electrical-signal transmission. Accordingly, the values of the resistor, capacitor and inductor can be varied — without altering their connections — by electrical signals determined externally by the user.

[0010] In another preferred embodiment the converter circuit is configured to furnish the same dynamic response for the resistor, capacitor and inductor, thereby blocking noise signals and signals with a disturbing influence during operation.

[0011] In a further preferred embodiment the converter circuit includes a third impedance converter that eliminates the need for an additional earth connection.

[0012] In still another preferred embodiment the induction hob comprises a power supply to which the converter circuit is connected, thereby providing the energy required for the circuit. Preferably the voltage supplied lies in the range 110 V - 240 V and the frequency in the range 55 Hz - 65 Hz, making the appliance compatible with mains standards.

[0013] The converter circuit preferably has a floating, two-terminal structure so that it can also be employed in circuits connected in series.

[0014] In a preferred application the method involves detecting the frequency values and variations of the electronic filter circuit and, in accordance with the detected variation, dynamically responding by means of the first impedance converter and the at least one second impedance converter within the converter circuit. Hence the required conversions for the induction hob are performed without additional converter equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 top view of the induction-hob arrangement according to the invention.

[0016] Figure 2 schematic representation of the converter-circuit arrangements inside the induction hob.

[0017] Figure 3 schematic representation of the filter-circuit arrangements inside the induction hob.

[0018] DETAILED DESCRIPTION OF THE INVENTION

[0019] The improvement of the invention is explained below solely by way of example, without any limiting effect, and with reference to the drawings.

[0020] Figure 1 shows the induction-hob arrangement in a top view. A first induction coil (2) is provided on the cooktop (1 ). Spaced apart from the first induction coil (2) there is a second induction coil (3); spaced apart from the second induction coil (3) there is a third induction coil (5); and spaced apart from the third induction coil (5) there is a fourth induction coil (6). A main control board (10) that activates and deactivates the first (2) and second (3) induction coils is provided. A converter circuit (20) is mounted on the main control board (10). A filter circuit (30) is connected to the converter circuit (20) so as to provide signal transmission. The main control board (10) also carries a power supply (40) that furnishes the mains input voltage.

[0021] Figure 2 schematically illustrates the converter circuit (20). The converter circuit comprises a first impedance converter (22), a second impedance converter (24) connected to the first, and a third impedance converter (26). Owing to the impedance converters (22, 24, 26) the resistor, inductor and capacitor can each be utilised individually within a single circuit. By changing a few connections, negative operations (multiplication, division) can be carried out, and thanks to the floating two-terminal structure the circuit can be used in series-connected arrangements.

[0022] Figure 3 schematically illustrates the filter circuit (30), which consists of a passive resistor (32), a capacitor (34) and an inductor (36). Frequency-selective filters pass signals at permitted frequencies and attenuate undesired signals, thereby suppressing noise and unwanted interference while the circuit is operating. The impedance of the resistor (32) is generally constant, being only slightly affected by temperature. The equation given below shows how the resistance of the resistor (32) varies with temperature. The impedance of the capacitor (34) and the inductor (36), on the other hand, changes with the operating frequency according to the formula below.

[0023] Z_R=R_0 (1+at) (1)

[0024] Z_C=1 / jWC (2)

[0025] Z_L=jWL (3)

[0026] When the temperature and the signal frequency remain constant, these impedances likewise remain constant. In circuits that employ dynamic-switching techniques, a fixed pass-band frequency or pass-band magnitude of the filter circuits (30) can create problems. To accommodate the behaviour of such dynamic circuits, filters whose response characteristics can change instantaneously must be designed instead of a fixed filter circuit (30).

[0027] Here, impedance conversion is carried out by using Operational Transconductance Amplifier (OTA) elements with transconductances grrii, gm2and gm3, together with a single base impedance. = 4 (4)

[0028] If Z is chosen as a resistor (R)

[0029] If Z is chosen as a coil (L) gm!

[0030] If Z is chosen as a capacitor (C) c‘“= c^ 5m3(10)

[0031] REFERENCE NUMBERS

[0032] 1 Cooktop

[0033] 2 First induction coil

[0034] 3 Second induction coil

[0035] 4 User interface

[0036] 5 Third induction coil

[0037] 6 Fourth induction coil

[0038] 10 Main control board

[0039] 20 Converter circuit

[0040] 22 First impedance converter

[0041] 24 Second impedance converter

[0042] 26 Third impedance converter

[0043] 30 Filter circuit

[0044] 32 Resistor

[0045] 34 Capacitor

[0046] 36 Inductor

[0047] 40 Power supply

Claims

CLAIMS1. An induction hob comprising a cooktop (1); a first induction coil (2) provided on the cooktop (1) and at least one second induction coil (3); a main control board (10) connected to the first and the at least one second induction coils (2, 3); and a user interface (4) connected to the main control board (10) for signal transmission characterized in that the main control board (10) carries a converter circuit (20) which comprises, on the main control board, an electronic filter circuit (30) and a first impedance converter (22) and at least one second impedance converter (24) configured to provide a joint dynamic response to short-term and instantaneous current-voltage variations and frequency variations.

2. The induction hob according to claim 1 , wherein the filter circuit (30) comprises a resistor (32), a capacitor (34) and an inductor (36) interconnected for electrical-signal transmission.

3. The induction hob according to claim 2, wherein the converter circuit (20) is configured so that the resistor (32), capacitor (34) and inductor (36) exhibit the same dynamic response.

4. The induction hob according to any one of the preceding claims, wherein the converter circuit (20) comprises a third impedance converter (26) arranged to eliminate an additional earth connection.

5. The induction hob according to any one of the preceding claims, wherein it comprises a power supply (40) to which the converter circuit (20) is connected.

6. The induction hob according to claim 5, wherein the voltage supplied by the power supply (40) lies in the range 110 V - 240 V.

7. The induction hob according to any one of claims 5-6, wherein the frequency supplied by the power supply (40) lies in the range 55 Hz - 65 Hz.

8. The induction hob according to any one of the preceding claims, wherein the converter circuit (20) possesses a floating, two-terminal structure.

9. A control method for an induction hob according to any one of the preceding claims, wherein it comprises the steps of detecting the frequency values and variations of the electronic filter circuit (30); and dynamically responding, in accordance with the detected frequency variation, by means of the first impedance converter (22) and theat least one second impedance converter (24) within the converter circuit (20) of the filter circuit (30).

Images