FR2634615A1 - INDUCTION COOKTOP COMPRISING A DEVICE FOR VISUALIZATION OF THE POWER ACTUALLY TRANSMITTED TO THE UTENSIL - Google Patents

Abstract

The invention relates to an induction hob comprising at least: - a control member 40, - an assembly of electronic components 50 forming a supply circuit 51, a control circuit 52, a power circuit 53 for supplying power. , - an induction coil 61 for heating a utensil 62, characterized in that it further comprises a display device of the power effectively transmitted to the utensil and optionally a control device 70 of the power effectively transmitted to the utensil, to the instruction of the control unit 40. Application: induction heating equipment.

Description

The present invention relates to a visualization device

  power supply for induction hob.

  The application of induction heating to the cooking of food contained in a kitchen utensil, such as saucepan, is known. In general, an induction cooking appliance is constructed according to the schematic diagram of FIG. 1 and mainly comprises, in a box (a), a support (b) in the form of a non-metallic plate, preferably in vitro-ceramic material a heating induction coil (c) mounted in the immediate vicinity of the support plate (b) and creating an alternating magnetic field closing in a utensil (h) placed on the support plate (b), and a set of electrical components and electronic components a power supply circuit (d), a circuit

  control (e), a power circuit (f) for the power supply

the coil (c).

  In addition, as on all cooking appliances, plates or enclosures, the user has at his disposal a control member (g), for example a slider or a

  adjustment knob, to vary the power.

  Devices of the type described above are already described in patent applications FR 72 27 277 and

FR 76 20 285.

  In all known devices to date the adjustment knob acts on the current absorbed by the circuit of

power (f).

  Unfortunately, in an induction hob, the power effectively transmitted to the utensil is not directly related to the position of the adjustment knob (g). For the same position of the control knob the power transmitted to the utensil varies a lot according to: - the diameter of the utensil, - the eccentricity of the utensil with respect to the center of the inductive coil,

  - the nature of the material of the utensil.

  By way of illustration of this phenomenon, the same position 7 of the control member (g) (see FIG. 1) can correspond to 1500 watt actually transmitted to a cast iron pan and to 800 w transmitted to a stainless steel saucepan. The user of an induction hob can not therefore, as he would with another hob, rely on the indication of the controller for

  know the power actually transmitted to the user.

if the.

  The user must learn by trial and error to correct the indication of the control device for each of his personal utensils, there is neither method nor

  adapted display device.

  To overcome this drawback, the induction hob according to the invention --comporte a display device of the power effectively transmitted

to the charge.

  According to the preferred embodiment described below, the display device is composed of at least: a current acquisition block whose input signal is the AC current consumed on the sector and whose continuous output signal is a direct image of the input signal, - a shaping device attacked by the signal

  of the previous block and transforming the value

  logic of this signal into a signal usable by a display, - a display receiving the signals of the device

formatting.

  More specifically, the acquisition block comprises an intensity transformer whose primary is a current loop placed immediately before the input of the rectifier

of the supply circuit.

  In addition to the display device, the cooking plate may comprise a servo block receiving the output signals of the acquisition block, to provide

  to the control electronics a signal allowing

  kill with the utensil a power corresponding to the instruction

control.

  The invention will be better understood with the aid of

  Hereinafter and the following appended figures: FIG. 1: schematic diagram of an apparatus for

known type.

  FIG. 2: block diagram of an electronic circuit comprising a display device according to the invention.

  - figure 3: electronic diagram showing the principal

  main components of the visualization device of the

figure 2.

  We first refer to Figure 2 which shows in the form of a block diagram, the main functions

  of an electronic circuit for an induction hob comprising

  both a display device according to the invention.

  Firstly, we find the conventional arrangement of FIG. 1 with: a set of electronic components (50) comprising a power supply circuit (51), a control circuit (52), a power circuit (53) - a heating device (60) comprising at least one induction coil (61) immediately under a non-metallic support (63), - a utensil (62) placed on the support (63),

a control member (40).

  The originality of the circuit lies in the addition of a display device (10, 20, 30) composed of an acquisition block (10), a shaping block (20), - 4 - a display (30); the display device has the function of indicating on the display (30) a quantity directly related to the power absorbed by the utensil (62). By way of non-limiting example, the applicant proposes a preferred embodiment of the invention in

Figure 3 and described below.

  The input of the acquisition block (10) is constituted

  by a current loop forming the primary of a trans-

  intensity trainer (11) (see Figures 2 and 3). The input signal of the acquisition block (10) is therefore the

current consumed on the sector.

  The secondary of the intensity transformer (11) is followed by a calibration assembly (12) and a detection assembly (13) consisting mainly of a bridge

  divider (14), a diode (15) and a capacitor (16).

  The output signal (V) of the transformer is calibrated then detected to provide a continuous output signal (Vi)

the acquisition block (10).

  The output signal (Vi) of the block (10) drives a

  block (20) for formatting whose function is to trans-

  - form the analog value of the current into a value

exploitable for display (30).

  In the case of a seven-segment display, not shown, the block (20) may comprise mainly a digital-to-digital converter

  associated with a converter-seven segments.

  In the case of a ramp display as on the

  FIG. 3, the block (20) may comprise an associated dividing bridge

  a network of comparators and LED drivers

(light emitting diode).

  Preferably the integrated circuit providing the formatting is of logarithmic type (LM 3915 manufacturer's reference for example) so that the number of points lit is a logarithmic function of the signal (Vi), because it is more useful to have a more large number of points

  display in the low power range.

- 5 -

  In all cases, the components dis-

  crets performing the formatting function can be

replaced by a microprocessor.

  In addition, the circuit may comprise an assertion block

  vissement (70) whose function is to provide the control electronics with a signal (Va) enabling the utensil to be restored to a power corresponding to the setpoint supplied by the control element, independently of the position, the diameter and the nature of the O10 material the utensil and this, within the characteristic limits of the power components. When the control does not manage to adjust the power in the utensil to the setpoint (for example diameter too small), the power components being at their limits, the power returned to the utensil is reduced. In this case, the presence of the display device (10, 20, 30), to display the power actually supplied to the utensil takes all

its meaning.

  According to the preferred non-limiting embodiment shown in FIG. 3, the block (70) is composed of a comparator (71) whose two inputs are respectively attacked on the one hand by the continuous signal (Vi) output of the block of acquisition (10), image of the power in the utensil, and secondly by a reference signal (c)

of the control member (40).

  The output signal (Va) of the comparator (71)

  the input signal of the control electronics (52) whose detail has not been shown because it does not

  no construction feature.

  The electronic power supply (51) and power (53) circuits are of conventional types, and the variations of the power can be obtained in a known manner by wattage power modulation and / or by modulation.

conduction time.

  Of course, alternative embodiments exist,

  they may relate, for example, to the choice of

  sants, the realization of the circuits of the various functional blocks (10, 20, ...), the place where the image of the power supplied to the utensil is measured. According to the applicant, the best choice for the detection of this current in the load is to place the input of the intensity transformer where the current is the most faithful image of the power actually supplied to the utensil, therefore immediately upstream. of the power supply (51), and downstream of an input filter (81)

  and the low voltage supply (82) of the apparatus.

  A direct detection of the current in the device (60) would be more difficult to achieve because of the high values of the intensities and the frequencies in this part of the circuit, and would not give the image of the power

supplied to the utensil.

  In addition, according to the preferred embodiment of FIG. 3, the output signal (Vi) of the acquisition block (10), intended to drive the shaping signal (20), is also used to realize the enslavement, the acquisition block in this case plays two roles: in the

  realization of the display and in the realization of the

  servissement. In a variant, the input signal of the servo

  could be detected by a separate block of the block (10).

  Another variant would still be to perform the functions of one or more of the functional blocks

  (10, 20, 70, 52, ...) by a microprocessor.

  Similarly the protection is not limited to the LED display mode (light emitting diode), any other display mode, for example LCD (liquid crystal display) or VFD (fluorescent display) can be used, and is not limited to induction hobs

having a single focus.

-7.

RE V E N D I C AT I 0 NS

  Induction hob with at least: a control member (40),

  - a set of electronic components (50)

  a power circuit (51), a control circuit (52), a power circuit (53) for powering, - an inductor coil (61) for heating a utensil (62), characterized in that it furthermore comprises a device for visualizing the power actually transmitted

to the utensil.

  2. Induction hob according to the claim

  preceding specification, characterized in that the device

  of visualization is composed of at least one block of acqui-

  sition (10), a shaping device (20), a display (30) in series; the acquisition block (10) comprising an intensity transformer whose primary is a current loop traversed by the current (i) of the sector and placed immediately before the input of the rectifier of the supply circuit (51), and whose secondary is

  followed by a set of calibration and trans-

  the output signal (V) of the transformer to a continuous signal (Vi) driving the input of the

formatting (20).

  3. An induction hob according to claim

  preceding cation, characterized in that the calibration and detection assembly consists mainly of a divider bridge (14), a diode (15) and a capacitor (16).

  4. Induction hob according to one

  conque of the preceding claims, characterized in that

  it further comprises a device for controlling (70) the power effectively transmitted to the utensil,

  to the setpoint of the control member (40).

- 8 -

  5. Induction hob according to the

  2,3,4, characterized in that the servo device (70) is directly attacked by the

  signal (Vi) supplied at the output of the acquisition block

sition (10'l).

  Induction hob according to claim

  preceding cation, characterized in that the servocontrol device (70) is composed of a comparator whose inputs are respectively attacked by the signal (Vi) and by the reference signal (c) of the control device, and whose output signal (Va) is sent to

the control electronics.

  7. Induction hob according to one

  of the preceding claims, characterized in that

  that the display (30) is an LED-type display (electro-light diodes) and that the shaping device (20) comprises a driver converter of the logarithmic type.

  8. Induction hob according to one

  conque of claims 1 to 6, characterized in that

  the display (30) is a display of the LCD type (liquid crystal) and in that the shaping device (20)

  has a logarithmic driver converter.

  9. Induction hob according to one

  shell of claims 1 to 6, characterized in that

  that the display (30) is a display of the VFD type (fluorescent

  rescent) and in that the shaping device

  (20) has a logarithmic driver converter.

  10. Induction hob according to one

  conque of the preceding claims, characterized in that

  what the function of at least one of the functional blocks

  (10, 20, 70, 52, ...) is performed by a microprocessor.