Heating circuits and cooking appliances

Abstract

To provide a heating circuit and a cooking apparatus that are capable of accurately measuring the real-time temperature of an object to be heated.SOLUTION: A heating circuit (100) includes: a heating unit (110) including a heating coil (L1) for performing resonance heating on an object (200) to be heated; and a measurement coil (120) part of which is in mutual induction with the heating coil (L1), the other part of which is in mutual induction with each of the heating coil (L1) and the object (200) to be heated, and which outputs a corresponding measurement signal. The measurement signal is used for cooperating with a measured and collected resonance electric parameter of the heating coil (L1) so as to determine the temperature of the object (200) to be heated. By means of the foregoing mode, the temperature of the object (200) to be heated is determined according to the measurement signal, thereby achieving highly accurate temperature control and allowing accurate measurement of the real-time temperature of the object (200) to be heated.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This application claims priority to the following Chinese patent application filed on May 12, 2020, with application number 2020103989957 and titled "Heating Circuit and Cooking Apparatus", filed on May 12, 2020, with the China Patent Office, with application number 2020207808640 and titled "Temperature Measuring Circuit and Cooking Apparatus", and the following Chinese patent application filed on May 12, 2020, with application number 2020207838542 and titled "Signal Processing Circuit, Resonant Heating Temperature Measuring Circuit and Cooking Apparatus", the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the field of heating technology, in particular to a heating circuit and a cooking appliance. [Background technology]

[0003] Electromagnetic heating cookers, such as induction stoves, electric rice cookers, and electric pressure cookers, are new cooking appliances that use the principle of electromagnetic induction heating to heat the pot with eddy currents. They have advantages such as high thermal efficiency, ease of use, no pollution caused by gas combustion, and are safe and hygienic, making them very suitable for use in modern households.

[0004] Conventional temperature measuring devices for electromagnetic cooking appliances indirectly measure the temperature of the pot using the N·TC (Negative Temperature Coefficient, a thermal resistor) on the coil disk, but have problems such as inaccurate temperature measurement or delayed temperature measurement. In addition, the temperature measurement error makes it difficult to accurately control the temperature, cook at a low temperature, and detect the boiling of water when performing smart cooking. Summary of the Invention [Problem to be solved by the invention]

[0005] The main technical problem to be solved by the present application is to provide a heating circuit and a cooking utensil that can solve the problems of inaccurate and delayed temperature measurement in an electromagnetic cooking appliance in the prior art. [Means for solving the problem]

[0006] In order to solve the above technical problem, the technical solution adopted in the present application is to provide a heating circuit, which includes a heating unit including a heating coil for resonantly heating an object to be heated, and a measuring coil, a part of which is mutually inductive with the heating coil and another part of which is mutually inductive with the heating coil and the object to be heated, and outputs a corresponding measuring signal, where the measuring signal is used to determine the temperature of the object to be heated together with the resonant electrical parameters of the heating coil collected by the measurement. In order to solve the above technical problem, another technical solution adopted in the present application is to provide a cooking utensil including the above heating circuit. Effect of the Invention

[0007] The beneficial effects of the present application are as follows: The heating circuit of the present application includes a heating unit including a heating coil for resonantly heating an object to be heated, and a measuring coil, a part of which is mutually inductive with the heating coil and another part of which is mutually inductive with the heating coil and the object to be heated, and outputs a corresponding measuring signal, where the measuring signal is used to determine the temperature of the object to be heated together with the resonant electrical parameters of the heating coil collected by measurement. The above method can obtain the temperature of the object to be heated, and the temperature of the object to be heated can be accurately detected in real time, thereby realizing high-precision temperature control. [Brief description of the drawings]

[0008] In order to more clearly describe the technical means of the embodiments of the present application, the drawings necessary for describing the embodiments will be briefly described below. However, the drawings in the following description are only some embodiments of the present application, and it is obvious that a person skilled in the art can obtain other accompanying drawings based on these drawings without any creative efforts.

[0009] [Figure 1] FIG. 2 is a structural schematic diagram of an embodiment of a heating circuit of the present application. [Diagram 2] FIG. 2 is an equivalent circuit model diagram of the heating circuit and the object to be heated in FIG. [Diagram 3] FIG. 2 is a waveform diagram of the measurement voltage and resonant collection voltage of the present application. [Figure 4] FIG. 2 is an equivalent model circuit diagram of an embodiment of a heating circuit of the present application. [Diagram 5] FIG. 4 is an equivalent model circuit diagram of another embodiment of the heating circuit of the present application. [Figure 6] 6 is a schematic diagram of sampling the voltage of DC electric energy stored in the energy storage capacitor C1 in FIG. 4 or FIG. 5. [Figure 7] 6 is a schematic diagram showing sampling of a resonant voltage applied to a resonant loop of the heating unit in FIG. 4 or FIG. 5. [Figure 8] FIG. 2 is a structural schematic diagram of another embodiment of the heating circuit of the present application. [Figure 9] FIG. 4 is a structural schematic diagram of a temperature measuring circuit in yet another embodiment of the heating circuit of the present application. [Figure 10] 10 is a schematic diagram showing the relationship between a power supply signal and an excitation signal of a temperature measuring circuit in yet another embodiment of the heating circuit shown in FIG. 9. FIG. [Figure 11] FIG. 4 is a structural schematic diagram of a temperature measuring circuit in yet another embodiment of the heating circuit of the present application. [Figure 12] 12 is a schematic diagram showing the relationship between the power supply signal and the zero cross signal of the temperature measuring circuit in still another embodiment of the heating circuit shown in FIG. 11. FIG. [Figure 13] 13 is a schematic diagram of a part of the structure of a temperature measuring circuit in yet another embodiment of the heating circuit of the present application. FIG. [Figure 14] 14 is a schematic diagram of a comparison signal of a temperature measuring circuit in still another embodiment of the heating circuit shown in FIG. 13. [Figure 15] 13 is a schematic diagram of a part of the structure of a temperature measuring circuit in yet another embodiment of the heating circuit of the present application. FIG. [Figure 16] 16 is a schematic diagram of a trigger signal of a temperature measuring circuit in still another embodiment of the heating circuit shown in FIG. 15. FIG. [Figure 17]FIG. 2 is a structural schematic diagram of yet another embodiment of the heating circuit of the present application. [Figure 18] FIG. 2 is a structural schematic diagram of yet another embodiment of the heating circuit of the present application. [Figure 19] FIG. 19 is an equivalent circuit model diagram of the heating circuit in FIG. 18. [Figure 20] FIG. 2 is a waveform diagram of the measurement voltage and resonant collection voltage of the present application. [Figure 21] FIG. 13 is a structural schematic diagram of yet another embodiment of a signal processing circuit in a heating circuit of the present application. [Figure 22] FIG. 13 is a structural schematic diagram of yet another embodiment of a signal processing circuit in a heating circuit of the present application. [Diagram 23] FIG. 20 is a schematic diagram of a circuit corresponding to the signal processing circuit of FIG. 19. [Figure 24] 1 is a structural schematic diagram of one embodiment of a cooking utensil according to the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the technical means in the embodiments of the present application will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present application, but the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. It is clear that any other embodiments obtained by those skilled in the art based on the embodiments of the present application without any creative work fall within the scope of protection of the present application.

[0011] First, although the heating circuit of the present application can be used in any heating appliance, for convenience of explanation, the following description will be given on the case where the heating circuit is used in a cooking appliance.

[0012] 1, which is a structural schematic diagram of an embodiment of the heating circuit of the present application. The heating circuit 100 of this embodiment may include a heating unit 110 and a measuring coil 120.

[0013] The heating unit 110 may include a heating coil L1 for resonantly heating the heated object 200. Here, the heated object 200 may be various pans that can be placed on the heating unit 110 and resonantly heated by the heating coil L1.

[0014] A portion of the measurement coil 120 can be mutually inductive with the heating coil L1, and another portion can be mutually inductive with each of the heating coil L1 and the heated object 200, and output a corresponding measurement signal, where the measurement signal is used to determine the temperature of the heated object 200 in combination with the resonant electrical parameters of the heating coil L1 collected by measurement.

[0015] Optionally, the measurement signal can be related to the resonant electrical parameters of the heating coil L1 and the thermal resistance parameters of the heated object 200, and the thermal resistance parameters of the heated object 200 are determined by the measurement signal and the resonant electrical parameters of the heating coil L1 collected by measurement, thereby determining the temperature of the heated object 200 based on the thermal resistance parameters.

[0016] In this embodiment, the temperature of the heated object 200 can be measured by measuring the change in thermal resistance of the heated object 200 at different temperatures; specifically, the change in thermal resistance of the heated object 200 can be detected by sampling the measurement signal of the measurement coil 120, and the temperature of the heated object 200 is indirectly derived through the functional relationship between the change in thermal resistance and the temperature of the heated object 200, thereby realizing non-contact coupling temperature measurement.

[0017] In the prior art, the temperature change of the heating environment is detected using the thermal resistance of the heating unit, but this does not take into account the relationship between the properties of the heated object itself and the heating temperature. Compared with the prior art, the present embodiment accurately obtains the thermal resistance parameters of the heated object 200 by detecting the mutual induction between the measuring coil 120, the heated object 200, and the heating coil L1, so that the heating circuit 100 of the present embodiment can accurately measure the real-time temperature of the heated object 200 while heating. When applied to a cookware, the heating circuit 100 of the present embodiment can realize smart cooking operations such as cooking with accurately controlled temperature, cooking at a low temperature, and accurately sensing the boiling of water in the cookware.

[0018] Specifically, the measurement coil 120 may include a first measurement sub-coil L2 and a second measurement sub-coil L3. Here, the first measurement sub-coil L2 may be placed close to the heating coil L1 so as to mutually induct with each of the heating coil L1 and the heated object 200, and the second measurement sub-coil L3 mutually inducts with the heating coil L1. In some embodiments, the second measurement sub-coil L3 is wound around a conductive material, and the resonant loop in which the heating coil L1 is located passes through the conductive material, so that the second measurement sub-coil L3 mutually inducts with the heating coil L1.

[0019] Here, a pair of ends with the same name of the first measurement subcoil L2 and the second measurement subcoil L3 are connected, and another pair of ends with the same name of the first measurement subcoil L2 and the second measurement subcoil L3 output a measurement signal as an output end of the measurement coil 120.

[0020] The first measurement sub-coil L2 and the second measurement sub-coil L3 constitute a differential coil, and one pair of the same-named ends (marked with * in Figure 1) are connected to each other, and the induced voltages of the heating coil L1 in the first measurement sub-coil L2 and the second measurement sub-coil L3 are canceled out, i.e., the second measurement sub-coil L3 can be used to cancel the interference of the heating coil L1 with the first measurement sub-coil L2, and it is required that the second measurement sub-coil L3 is not affected by the heated object 200, i.e., is away from the magnetic field interference of the heated object 200.

[0021] The first measuring sub-coil L2 can be regarded as a sampling coil for the thermal resistance of the heated object 200. The heating coil L1 can convert the electric energy in the form of a magnetic field into electrical energy, and then convert it into thermal energy to resonantly heat the heated object 200. When performing resonant heating, the heated object 200, such as various pans, may be equivalent to a circuit consisting of an inductive inductance and a thermal resistance.

[0022] Optionally, the first measurement sub-coil L2 may be placed on the disk surface of the heating coil L1 at a predetermined angle, where the predetermined angle may be located within a range of 0 to 45 degrees. Preferably, the predetermined angle is 0 degrees, and the first measurement sub-coil L2 may be placed parallel to the disk surface of the heating coil L1, and the first measurement sub-coil L2 may further be placed at the center position of the disk surface of the heating coil L1 where the magnetic field is weak, so that the measurement result is more accurate.

[0023] The heating circuit 100 may further include a collecting unit 130. In this embodiment, the collecting unit 130 may be a collecting coil L4, and in some embodiments, the collecting coil L4 is wound around a magnetic conductive body, and the resonant loop of the heating coil L1 passes through the magnetic conductive body, so that the collecting coil L4 and the heating coil L1 mutually induce each other, thereby collecting the resonant electric parameter of the heating coil L1. Here, the resonant electric parameter may be a resonant current flowing through the heating unit 110.

[0024] The sampling coil L4 may be a high frequency signal transformer of the heating coil L1, inducing a resonant current through the heating coil L1 in the form of high frequency mutual induction to generate a corresponding resonant collection voltage which is fed back to the processing circuit 140.

[0025] 1, the heating circuit 100 may further include a processing circuit 140. The processing circuit 140 may be connected to the output of the measurement coil 120 and the output of the collection unit 130 to collect the measurement signal and the resonant electrical parameter, thereby determining a thermal resistance parameter of the heated object 200 based on the measurement signal and the resonant electrical parameter, and determining a temperature of the heated object 200 based on the thermal resistance parameter.

[0026] The measurement signal output by the measurement coil 120 may include a measurement voltage. The resonant electrical parameter output by the collection unit 130 may include a resonant collected voltage corresponding to a resonant current flowing through the heating coil L1. The processing circuitry 140 can determine a thermal resistance parameter of the heated object 200 by comparing the measurement voltage and the resonant collected voltage, for example, by comparing the phase difference between the two.

[0027] Specifically, the processing circuit 140 may include a main control chip and a processing module. When the processing circuit 140 obtains information of the measuring coil 120 and the collecting unit 130, such as the measuring voltage and the resonant collecting voltage, the information is processed by the processing module, and then the analog signal in the circuit is converted into a digital signal and sent to the main control chip, and the main control chip analyzes the digital signal to obtain the temperature of the heated object 200.

[0028] Here, the processing module may include at least a follower circuit, an amplifier circuit, a follower circuit, etc. The main control chip can also simultaneously realize other functions, such as controlling the power transistor in the control circuit.

[0029] 1 and 2, Fig. 2 is an equivalent circuit model diagram of the heating circuit and the object to be heated in Fig. 1. In this embodiment, the object to be heated 200 includes an induction inductance Lr and an equivalent thermal resistance Rz.

[0030] 2, when the heating coil L1 of the heating unit 110 performs resonant heating, a resonant current I1 flows through the resonant loop in which the heating coil L1 is located, and the sampling coil L4 is induced in the resonant circuit I1 through the heating coil L1 to generate a corresponding resonant collected voltage U1. The measurement voltage output by the measurement coil 120 (including the measurement voltages of the first measurement sub-coil L2 and the second measurement sub-coil L3) is denoted as U2.

[0031] When the object to be heated 200 is placed on the heating coil L1 of the heating unit 110, the heating coil L1 undergoes mutual induction with the induced inductance Lr of the object to be heated 200, thereby generating a corresponding induced current Ir, where the induced current Ir flows through the induced inductance Lr and equivalent thermal resistance Rz of the object to be heated 200.

[0032] When the heating coil L1 generates a mutual induction M1r with the induction inductance Lr of the object to be heated 200, the following formula is satisfied.

[0033]

number

[0034] In the present application, the second measurement sub-coil L3 of the measurement coil 120 mutually induces with the heating coil L1, and the first measurement sub-coil L2 mutually induces with both the heating coil L1 and the heated object 200. Therefore, as shown in Fig. 2, the induction inductance Lr of the heated object 200 generates a mutual induction Mr2 with the first measurement sub-coil L2, but does not generate a mutual induction with the second measurement sub-coil L3. The heating coil L1 generates a mutual induction M13 with the second measurement sub-coil L3, and generates a mutual induction M12 with the first measurement sub-coil L2.

[0035] For the convenience of subsequent calculations, the measurement coil 120 may be corrected in advance. When the heated object 200 is not placed on the heating unit 110, the measurement coil 120 sets the voltage difference between the two output ends to a predetermined value, thereby completing the correction. Optionally, the predetermined value may be 0, thereby completing the zeroing correction, and the measurement voltage U2 output by the measurement coil 120 is only due to the mutual induction Mr2 between the first measurement sub-coil L2 and the induction inductance Lr of the heated object 200. In the following, a case where the voltage difference between the two output ends after correction is 0 is taken as an example.

[0036] Specifically, when the heated object 200 is placed, the induction inductance Lr generates a mutual induction Mr2 with respect to the first measurement sub-coil L2, and when the heated object 200 is not placed, the induction inductance Lr does not generate a mutual induction Mr2 with respect to the first measurement sub-coil L2, so that when the heated object 200 is not placed on the heating unit 110, the voltage difference between the two output ends of the measurement coil 120 is set to 0, thereby performing zeroing correction on the measurement coil 120. At this time, the voltage difference between the different ends of the first measurement sub-coil L2 and the second measurement sub-coil L3 is close to 0, that is, jωM13=jωM12, and zeroing correction is performed on the first measurement sub-coil L2 and the second measurement sub-coil L3, that is, the initial U2=0 is obtained.

[0037] When the target 200 is placed on the heating unit 110, the induced inductance Lr of the target 200 generates a mutual induction Mr2 with respect to the first measurement sub-coil L2, but does not generate a mutual induction with respect to the second measurement sub-coil L3, and satisfies jωM13=jωM12 after performing zero correction on the mutual induction M12 of the heating coil L1 with respect to the first measurement sub-coil L2 and the mutual induction M13 of the heating coil L1 with respect to the second measurement sub-coil L3. Therefore, the measurement voltage U2 output by the measurement coil 120 is generated only by the induced inductance Lr of the target 200 generating a mutual induction Mr2 with respect to the first measurement sub-coil L2, that is, as follows:

[0038]

number

[0039] In other words, after the zeroing correction of the measurement coil 120, a mutual induction M13 is generated between the second measurement sub-coil L3 and the heating coil L1, and the mutual induction M12 of the heating coil L1 with respect to the first measurement sub-coil L2 is canceled out, so that the measurement voltage subsequently output by the measurement coil 120 is generated only by the induced inductance Lr of the heated object 200 generating a mutual induction Mr2 with respect to the first measurement sub-coil L2.

[0040] Therefore, by substituting the above equation (1) into equation (2), we obtain the following.

[0041]

number

[0042] In formula (3), the resonant current I1 may be measured by the sampling coil L4, specifically, U1 is the mapping voltage of I1, so that the resonant current I1 can be obtained by the resonant collection voltage U1 output by the sampling coil L4. U2 is the measurement voltage output by the measurement coil 120. When the inductance values ​​of the heating coil L1, the first measurement sub-coil L2, the second measurement sub-coil L3, the sampling coil L4, and the inductance Lr are specified, and their relative positions are specified, M1r and Mr2 can also be specified. Therefore, the magnitude of the thermal resistance Rz of the heated object 200 can be calculated by the above formula (3).

[0043] Lr is the induction inductance of the heated object 200, and the heated object 200 is generally a cooking pot, so the temperature coefficient of the induction inductance Lr is small, but the equivalent thermal resistance Rz has a large temperature coefficient, and the temperature coefficient of most stainless steel or iron materials is between 0.001 and 0.007 (20°C). Therefore, when U2 and I1 are measured, the thermal resistance Rz of the heated object 200 can be derived, and then the temperature of the heated object 200 can be obtained based on the preset thermal resistance-temperature function T=f(Rz).

[0044] Therefore, in this embodiment, the thermal resistance parameters of the heated object 200 are accurately obtained by detecting the mutual induction between the measuring coil 120, the heated object 200, and the heating coil L1, so that the heating circuit 100 of this embodiment can accurately measure the real-time temperature of the heated object 200 while heating. When the heating circuit 100 of this embodiment is applied to a cookware, smart cooking operations such as cooking by accurately controlling the temperature, cooking at a low temperature, and accurately sensing the boiling of water in the cookware can be realized.

[0045] In addition, the processing circuit 140 can perform data processing in the heating circuit 100, and as can be seen in combination with equation (3), the processing circuit 140 can determine the equivalent thermal resistance Rz of the heated object 200 based on the measurement voltage U2 and the resonant collection voltage U1, and can determine the temperature of the heated object 200 based on the equivalent thermal resistance Rz.

[0046] Processing circuit 140 samples the waveforms of resonant collection voltage U1 and measurement voltage U2 by high-speed AD, stores them in memory, and then performs data processing. Since resonant collection voltage U1 and measurement voltage U2 are AC, and it can be seen from equation (3) that measurement voltage U2 is a non-standard function, the values ​​of resonant collection voltage U1 and measurement voltage U2 cannot be obtained directly. Processing circuit 140 must further perform digital signal processing on the waveforms, such as DFT (Discrete Fourier Transform) processing, which involves selecting a finite discrete frequency sequence of length M (1 to 10) and deriving the Nth trigonometric function U 2N =C V2N *cos(ω Nt +Φ V2N ) and similarly, for U1, select a finite discrete frequency sequence of length M and calculate the Nth trigonometric function U 1N =C V1N *sin(ω Nt +Φ V1N This involves parsing

[0047] U 2N and U 1NSince the excitation source of is the same, the point of selecting the discrete frequency is also the same, so the frequency of both is also the same, i.e., ω Nt and C V2N and C V1N is U 2N and U 1N Therefore, U 1N and U 2N By only obtaining the phase difference ΔΦ between the measured voltage U2 and the resonant collection voltage U1, Rz can be indirectly related, and there is no need to compare the specific values ​​of the measured voltage U2 and the resonant collection voltage U1. In addition, in order to reduce interference factors, the fundamental waves of U1 and U2 can preferably be selected as the comparison object.

[0048] Specifically, the processing circuit 140 can obtain the phase difference ΔΦ in the following manner.

[0049] 1) Obtain the ratio of the measured voltage U2 to the resonant collection voltage U1, and process the ratio, for example by performing an arctangent function operation, to obtain the phase difference between the measured voltage U2 and the resonant collection voltage U1. Formula: tan(Φ V2N -Φ V1N )=C V2N *cos(ω Nt +Φ V2N ) / C V1N *sin(ω Nt +Φ V1N ), tan(Φ V1N -Φ V2N ) The arctangent function arctan is ΔΦ=Φ V1N -Φ V2N can be obtained.

[0050] 2) Compare the waveforms of the measurement voltage U2 and the resonant collection voltage U1 to obtain the phase difference between the measurement voltage U2 and the resonant collection voltage U1. As shown in FIG. 3, FIG. 3 is a waveform diagram of the measurement voltage and the resonant collection voltage of the present application. U 1N Starting from point a of the voltage waveform, U 2N The time it takes for the voltage to reach point b is recorded, and ΔΦ is the phase difference, where points a and b are the same voltage value.

[0051] 3) A comparator compares the measured voltage U2 with the resonant collection voltage U1 to obtain the phase difference between the measured voltage U2 and the resonant collection voltage U1. For example, U 1N and U 2N is output through the I / O interface of U1, 1N and U 2N are accessed as the positive and negative inputs of the comparator, thereby obtaining the phase difference ΔΦ.

[0052] Also, those skilled in the art may obtain the phase difference ΔΦ by other methods, and detailed description will be omitted here. After obtaining the phase difference ΔΦ, ΔΦ corresponding to the thermal resistance Rz at a temperature (-50° to 400°) is measured, and then the relational equation T=f(ΔΦ) between the two is established. When actually using, the temperature of the heating target 200 can be obtained from the table or the relational equation between the two.

[0053] Further, referring to Fig. 4 and Fig. 5, Fig. 4 is an equivalent model circuit diagram of one embodiment of the heating circuit of the present application, and Fig. 5 is an equivalent model circuit diagram of another embodiment of the heating circuit of the present application. The heating circuit 100 further includes a rectifier unit 150, an energy storage capacitor C1, a resonant capacitor C2, a DC supplement unit 160 and an inverter unit 170. Here, the heating unit 110 of Fig. 4 includes a heating coil L1 and a resonant capacitor C2 connected in series, that is, the heating coil L1 and the resonant capacitor C2 form an LC series resonant loop. The heating circuit 110 of Fig. 5 includes a heating coil L1 and a resonant capacitor C2 connected in parallel, that is, the heating coil L1 and the resonant capacitor C2 form an LC parallel resonant loop.

[0054] Here, the rectifier unit 150 may be a rectifier bridge D1, which can rectify AC power into DC power. The commonly used commercial power source is AC power, and the commercial power source ranges from 100 to 280V. The rectifier bridge D1 can rectify the commercial power source to provide a DC bus voltage.

[0055] The energy storage capacitor C1 can be connected to the rectifier unit 150 and used to store DC electric energy. The resonant capacitor C2 can be connected in series or parallel with the heating coil L1 to configure the heating unit 110, thereby forming an LC series resonant heating circuit (shown in FIG. 4) or an LC parallel resonant heating circuit (shown in FIG. 5). The heating coil L1 and the resonant capacitor C2 can generate high-frequency vibration of 15KHz to 60KHz through inverse transformation, radiate a magnetic field, and an eddy current is formed at the bottom of the heated object 200 to perform electromagnetic induction heating.

[0056] The DC supplement unit 160 is connected to the energy storage capacitor C1 to introduce DC supplementary electric energy. The DC supplement unit 160 may be a diode D2, one end of which is connected to a DC power source to introduce DC electric energy, where the voltage range of the introduced DC electric energy may be 10-400V, and preferably 10-50V, 140-160V, and 282-367V.

[0057] The inverter unit 170 is connected to the resonant loop of the heating unit 100 to receive the oscillation frequency signal, and is driven by the stored DC electric energy and the introduced DC supplementary electric energy to make the heating unit 110 perform resonant heating in the resonant unit. Specifically, the inverter unit may include a half-bridge resonant module 171 or a single-tube resonant module 172.

[0058] The inverter unit 170 in Fig. 4 adopts a half-bridge resonant module, which may include two switch power transistors Q2 and Q3, which are connected to each other in a totem pole shape, connected to both ends of an energy storage capacitor C1, and connected to the resonant loop of the heating unit 110 with the midpoint as an output. The control ends of the switch power transistors Q2 and Q3 respectively receive an oscillation frequency signal.

[0059] The inverter unit 170 in FIG. 5 adopts a single-tube resonant module which may include a power transistor Q4, which is connected across the energy storage capacitor C1 and connected to the resonant loop of the heating unit 110, and the control end of the power transistor Q4 receives an oscillation frequency signal.

[0060] Here, the power transistors Q2, Q3, and Q4 may receive an oscillation excitation source for the resonant loop of the corresponding heating unit 110, and may receive a driving signal from the processing circuit 140 so as to be turned on or off according to the driving signal.

[0061] It should be noted that the "LC series resonance + half-bridge resonance module" in the heating circuit of Fig. 4 or the "LC parallel resonance + single tube resonance module" in the heating circuit of Fig. 5 are merely examples of the present application, and do not mean that the LC series resonance circuit can only be combined with the half-bridge resonance module, or that the LC parallel resonance circuit can only be combined with the single tube resonance module. In some other heating circuits, those skilled in the art can also combine the heating circuit of "LC series resonance + single tube resonance module" or "LC parallel resonance + half-bridge resonance module" according to the actual situation, and detailed description is omitted here.

[0062] As can be seen from the above, DC supplementary electric energy may be introduced into the DC supplementary unit 160. Specifically, referring to Fig. 6 and Fig. 7, Fig. 6 is a schematic diagram of sampling the voltage of the DC electric energy stored in the energy storage capacitor C1 in Fig. 4 or Fig. 5, and Fig. 7 is a schematic diagram of sampling the resonant voltage applied to the resonant loop of the heating unit 110 in Fig. 4 or Fig. 5.

[0063] As shown in Figure 6, Z1 is the peak window of the voltage of the energy storage capacitor C1, and Z2 is the bottom window of the voltage of the energy storage capacitor C1. As shown in Figure 7, Z11 is the peak window of the resonant voltage applied to the resonant loop of the heating unit 110, and Z22 is the bottom window of the resonant voltage applied to the resonant loop of the heating unit 110.

[0064] Here, the duration of Z1 and Z2 may be 10 microseconds to 3 milliseconds, and the duration of Z11 and Z22 may be 10 microseconds to 3 milliseconds, where the durations of Z1 and Z2 and Z11 and Z22 can be controlled by adjusting the magnitude of the DC replenishment electric energy introduced into the DC replenishment unit 160.

[0065] Furthermore, the multiple modules / units in the above embodiments may be combined with each other if not contradictory, and there is no restriction unless otherwise stated in the present application.

[0066] In addition, in some embodiments, the collecting unit 130 may be a resistive sampling circuit 131. Specifically, as shown in FIG. 8, FIG. 8 is a structural schematic diagram of another embodiment of the heating circuit of the present application. In this embodiment, instead of adopting the sampling coil L4 as the collecting unit 130 as in the above embodiment, the collecting unit 130 is adopted as the resistive sampling circuit 131. For example, one end of the resistive sampling circuit 131 may be coupled to the resonant loop of the heating unit 110, and the other end may be grounded, so that the resistive sampling circuit 131 collects the resonant electrical parameters of the heating coil L1.

[0067] Specifically, the resistive sampling circuit 131 may include a sampling resistor R1 and a power transistor Q1, the control end of the power transistor Q1 may receive a resonant frequency, one path end of the power transistor Q1 may access the resonant loop as an input end of the resistive sampling circuit 131, and the other path end may be connected to the sampling resistor R1, and the connection node may output the collected electrical signal as the output end of the resistive sampling circuit 131.

[0068] Referring to Figures 9 and 10, Figure 9 is a structural schematic diagram of a temperature measuring circuit of yet another embodiment of the heating circuit of the present application, and Figure 10 is a schematic diagram of the relationship between the power supply signal and the excitation signal of the temperature measuring circuit of yet another embodiment of the heating circuit shown in Figure 9.

[0069] Yet another embodiment of the present application provides a heating circuit, which further includes a temperature measuring circuit 300 , where the temperature measuring circuit 300 includes a temperature measuring unit 31 , a trigger unit 32 and a processing unit 33 .

[0070] A power supply power source and an excitation power source are connected to the input end of the temperature measuring unit 31, and a power supply signal VAC and an excitation signal VSS are input to be excited by the excitation signal VSS to generate a temperature measuring signal VAB when the excitation signal VSS is less than the excitation threshold VSS1, and when the excitation signal VSS is less than the excitation threshold VSS1, the power supply signal VAC is within a zero-crossing range W, and the zero-crossing range W is centered on the zero-crossing point Z.

[0071] The power supply signal VAC realizes the power supply for the whole circuit, and in this embodiment, the power supply signal VAC is a 220V commercial AC power supply, and the temperature measurement circuit 300 may include operation periods such as a heating period and a temperature measurement period. In order to avoid affecting normal operation, the temperature measurement period is selected from the zero-crossing range W of the power supply signal VAC, and the zero-crossing range W is centered on the zero-crossing point Z. That is, when the power supply signal is small and has no effect on the operation effect, the temperature measurement is performed, for example, when the power supply signal is small and has little effect on the heating effect, the temperature measurement is performed, and the corresponding temperature measurement unit 31 also generates a temperature measurement signal VAB within the temperature measurement period.

[0072] In this embodiment, the temperature measurement period is controlled by utilizing the excitation signal VSS corresponding to the power supply signal VAC. Specifically, the temperature measurement unit 31 in this embodiment is excited to generate the temperature measurement signal VAB only when the excitation signal VSS is less than the excitation threshold VSS1, and the range in which the excitation signal VSS is less than the excitation threshold VSS1 corresponds to the zero cross range W. Here, the period of the excitation signal VSS is half the period of the power supply signal VAC, and in this embodiment, the excitation signal VSS is set to 5V to 50V, and the excitation signal VSS less than 50V does not affect the function of the power supply signal VAC.

[0073] The purpose of this embodiment is to obtain the accurate start time of collecting the temperature measurement signal, so as to measure the temperature more accurately. As can be seen from the above description of the temperature measurement unit 31, the generation of the temperature measurement signal VAB corresponds to the zero crossing range of the power supply signal VAC, and also corresponds to the excitation signal VSS being less than the excitation threshold VSS1, so that the start time of collecting the temperature measurement signal VAB can be obtained by detecting the power supply signal VAC or the excitation signal VSS.

[0074] Because it is not easy to directly detect the power supply signal VAC or the excitation signal VSS, this embodiment introduces a trigger unit 32, whose input end is connected to the power supply source and / or the excitation source for inputting the power supply signal VAC and / or the excitation signal VSS, and generates a trigger signal according to the power supply signal VAC and / or the excitation signal VSS. The function of the trigger unit 32 is to convert the power supply signal VAC or the excitation signal VSS so as to make it easier to measure.

[0075] The processing unit 33 of this embodiment is connected to the trigger unit 32 to acquire a trigger signal and determine the start time TA for collecting the temperature signal VAB in response to the trigger signal. The start time TAB corresponds to the zero crossing point Z.

[0076] In this embodiment, the trigger unit 32 is installed, so that the acquisition time of the temperature measurement signal VAB becomes more accurate, and the temperature measurement result becomes more accurate.

[0077] The processing unit 33 further determines the end time TB for collecting the temperature signal VAB to be a time obtained by delaying the start time TA by a third time T3. The third time T3 is determined by the frequency of the power supply signal VAC, and in this embodiment, the power supply signal VAC is 50 Hz, and 10 us to 2 ms is selected as T3.

[0078] As can be seen from the above description, the key point of this embodiment is that the trigger unit 32 converts the power supply signal VAC and / or the excitation signal VSS into a trigger signal to facilitate measurement, and in this embodiment, the trigger signal can be converted into a square wave signal, and accurate time detection is realized by detecting edge interrupts in the square wave signal. The detailed circuit structure of the trigger unit 32 will be described in the following embodiment, but it is obvious that it is not limited to the following embodiment, and any other circuit structure that can realize accurate time detection can be applied to the present application.

[0079] 11 and 12, Fig. 11 is a structural schematic diagram of a temperature measuring circuit of yet another embodiment of the heating circuit of the present application, and Fig. 12 is a schematic diagram of the relationship between the power supply signal and the zero cross signal of the temperature measuring circuit of yet another embodiment of the heating circuit shown in Fig. 11. The structure of the temperature measuring circuit 400 of the heating circuit of yet another embodiment of the present application is almost the same as that of the temperature measuring circuit 300 of the heating circuit of the previous embodiment, and similarly includes a temperature measuring unit 41, a trigger unit 42 and a processing unit 43. The trigger unit 42 and the processing unit 43 are the main differences.

[0080] In this embodiment, the trigger unit 42 includes a zero-cross circuit, to which the power supply signal VAC is input, and which outputs a zero-cross signal ZERO as a trigger signal. The zero-cross signal ZERO is a square wave signal.

[0081] Since the comparator in the zero-crossing circuit is a double-edge interrupt comparator and can generate a double-edge interrupt signal, the processing unit 43 can collect the interrupt time A of the falling edge of the previous square wave in the zero-crossing signal ZERO and the interrupt time B of the rising edge of the next square wave, and determine the start time TA based on the interrupt time A of the falling edge and the interrupt time B of the rising edge. Specifically, the midpoint between the interrupt time A of the falling edge and the interrupt time B of the rising edge is set as the time of the zero-crossing point Z, and the time obtained by delaying the time of the zero-crossing point Z by the first time T1 is set as the start time TA.

[0082] Specifically, the trigger unit 42 includes a first comparator CMP1, a first diode D2 and a second diode D3, where the first comparator CMP1 is a double-edge interrupt comparator.

[0083] The positive input terminal of the first comparator CMP1 is connected to the output terminal of the first diode D2 and the output terminal of the second diode D3, the input terminal of the first diode D2 is connected to the first electrode L of the signal source of the power supply signal VAC, and the input terminal of the second diode D3 is connected to the second electrode N of the signal source of the power supply signal VAC, so that the power supply signals VAC input to the positive input terminal of the first comparator CMP1 are all positive signals.

[0084] The first comparator CMP1 receives the reference signal Vref from the negative input terminal and outputs the zero-cross signal ZERO from the output terminal. The square wave of the zero-cross signal ZERO indicates that the power supply signal VAC is greater than the reference signal Vref. Therefore, the period between the interrupt time A of the falling edge and the interrupt time B of the rising edge corresponds to the zero-cross range W, and the midpoint between the interrupt time A of the falling edge and the interrupt time B of the rising edge represents the time of the zero-cross point Z.

[0085] In the present embodiment, the trigger unit 42 generates a square wave in the trigger signal in a range other than the zero-crossing range in response to a trigger signal generated by the power supply signal VAC, detects edge interruptions of the square wave, and determines the zero-crossing point Z in response to the edge interruption, thereby determining the start time TA of collection.

[0086] 13 and 14, Fig. 13 is a schematic diagram of a part of the structure of a temperature measuring circuit of yet another embodiment of the heating circuit of the present application, and Fig. 14 is a schematic diagram of a comparison signal of the temperature measuring circuit of yet another embodiment of the heating circuit shown in Fig. 13. The temperature measuring circuit of yet another embodiment of the heating circuit of the present application includes a temperature measuring unit, a trigger unit 52 and a processing unit.

[0087] The trigger unit 52 includes a second comparator CMP2, the positive input end of which is connected to a threshold power supply to input the excitation threshold VSS1, the negative input end of which inputs the excitation signal VSS, and the output end of which outputs a comparison signal VSS_INT, which is a square wave signal, as a trigger signal. The square wave here represents that the excitation signal is less than the excitation threshold. Other comparators opposite to the second comparator CMP2 can be set according to the same principle.

[0088] The processing unit determines the interrupt time of the rising edge of the square wave in the comparison signal VSS_INT as the start time TA.

[0089] The trigger unit 52 in this embodiment generates a trigger signal in response to the excitation signal VSS, generates a square wave when the excitation signal VSS is less than the excitation threshold VSS1, and determines the start time TA of acquisition by detecting the edge interruption of the square wave.

[0090] 15 and 16, Fig. 15 is a schematic diagram of a part of the structure of a temperature measuring circuit of yet another embodiment of the heating circuit of the present application, and Fig. 16 is a schematic diagram of a trigger signal of the temperature measuring circuit of yet another embodiment of the heating circuit shown in Fig. 15. The temperature measuring circuit of yet another embodiment of the heating circuit of the present application includes a temperature measuring unit, a trigger unit 62 and a processing unit.

[0091] The trigger unit 62 includes a transistor Q1, which receives the power supply signal VAC from its base electrode, is connected to the second electrode N of the signal source of the power supply signal VAC, receives the excitation signal VSS from its emitter electrode, and outputs a trigger signal VSS_INT, which is a square wave signal, from its collector. The square wave indicates that the power supply signal VAC is less than the excitation signal VSS.

[0092] The processing unit determines the interrupt time of the rising edge of the square wave in the trigger signal as the start time TA. Since the base electrode of the transistor Q1 is connected to only one electrode of the VAC signal source, a square wave is generated when the power supply signal VAC crosses the zero point from positive to negative, and a new square wave is not generated when the power supply signal VAC crosses the zero point from negative to positive, so the start time within the zero crossing range from negative to positive is obtained by delay calculation. That is, the processing unit further determines the start time TA1 as the time obtained by delaying the interrupt time of the rising edge by a second time T2.

[0093] This embodiment is a half-wave trigger, and there is a half-cycle interval between TA1 and TA. For example, if the frequency of the power supply signal VAC is 50 Hz, then TA1-TA=10 ms, and by the same principle, T2+T3=10 ms.

[0094] The trigger unit of this embodiment generates a trigger signal according to the relationship between the power supply signal VAC and the excitation signal VSS, generates a square wave when the power supply signal VAC is less than the excitation signal VSS, and determines the start time TA of acquisition by detecting the edge interrupt of the square wave.

[0095] The above embodiments generate a trigger signal that can be more easily detected, so that the acquisition time of the temperature measurement signal is determined, and the acquisition time is more accurate, and the temperature measurement result is correspondingly more accurate. In addition, in the above two embodiments, the circuit structure of the trigger unit can be connected to the circuit structure of the temperature measurement circuit in FIG.

[0096] Please refer to FIG. 17, which is a structural schematic diagram of yet another embodiment of the heating circuit of the present application.

[0097] Yet another embodiment of the present application provides a heating circuit further including a signal processing circuit 700, which is connected to an output end of the measurement coil or sampling coil of the heating circuit 70 to process a processed signal output by the measurement coil or sampling coil. Specifically, the heating circuit 70 of the present application may include a heating coil L1, a measurement coil 720, a sampling coil 730 and a signal processing circuit 700.

[0098] The heating coil L1 is used to resonantly heat the object to be heated, where the object to be heated can be various pans. The measurement coil 720 can mutually induce with the heating coil L1 and the object to be heated, respectively, and thereby output a measurement signal.

[0099] In one embodiment, the sampling coil 730 may be wound around a magnetic conductive material, and the resonant loop of the heating coil L1 passes through the magnetic conductive material to collect the resonant electrical parameters of the heating coil L1 to obtain a collected signal, where the sampling coil 730 may be a current transformer of the heating coil L1 to sample the resonant current flowing through the heating coil L1 in a mutually inductive manner.

[0100] The signal processing circuit 700 may be connected to the output end of the measurement coil 720 or the sampling coil 730 of the heating circuit 70 and used to process the processed signal output by the measurement coil 720 or the sampling coil 730.

[0101] When the signal processing circuit 700 is connected to the output end of the measurement coil 720, the processed signal is the measurement signal output by the measurement coil 720, and when the signal processing circuit 700 is connected to the output end of the sampling coil 730, the processed signal is the sampling signal output by the sampling coil 730.

[0102] 18 and 19, Fig. 18 is a structural schematic diagram of yet another embodiment of the heating circuit of the present application, and Fig. 19 is an equivalent circuit model diagram of the heating circuit of Fig. 18. The heating circuit 70 of this embodiment may include a heating coil L1, a measurement coil 720, a sampling coil L4, and a signal processing circuit 700. Here, the measurement coil 720 may include a first measurement sub-coil L2 and a second measurement sub-coil L3.

[0103] The first measurement sub-coil L2 may be placed close to the heating coil L1 so as to mutually induce with each of the heating coil L1 and the heated object 200, and the second measurement sub-coil L3 mutually induces with the heating coil L1. In one embodiment, the second measurement sub-coil L3 is wound around a conductive material and passes through a resonant loop in which the heating coil L1 is located.

[0104] The first measurement sub-coil L2 and the second measurement sub-coil L3 constitute a differential coil, and one pair of ends having the same name (marked with * in FIG. 18) are connected to each other, and another pair of ends having the same name outputs a measurement signal as an output end of the measurement coil 720. In this way, the thermal resistance parameter of the heated object 200 is determined by the measurement signal and the collected resonant electrical parameters of the heating coil, and the temperature of the heated object is determined based on the thermal resistance parameter.

[0105] The second measurement sub-coil L3 is used to generate mutual induction with the heating coil L1 to cancel out the mutual induction generated by the first measurement sub-coil L2 and the heating coil L1, and therefore it is required that the second measurement sub-coil L3 does not generate mutual induction with the heated object 200 and is away from the magnetic field interference of the heated object 200.

[0106] The first measuring sub-coil L2 can be regarded as a sampling coil for the thermal resistance of the heated object 200. The heating coil L1 converts the electric energy in the form of a magnetic field into electric energy, and then converts it into thermal energy to resonantly heat the heated object 200. When performing resonant heating, the heated object 200, such as various pans, may be equivalent to a circuit consisting of an inductive inductance and a thermal resistance.

[0107] In this embodiment, the measurement signal output by the measurement coil 720 may be a measurement voltage, and the sampling signal output by the sampling coil L4 may be a resonant current, and after processing, the resonant current output by the sampling coil L4 can be converted into a resonant collected voltage.

[0108] As shown in Fig. 11, when the heating coil L1 performs resonant heating, a resonant current I1 flows through the resonant loop in which the heating coil L1 is located. The sampling coil L4 is wound around a magnetic conductive body, and the resonant loop of the heating coil L1 passes through the magnetic conductive body, which is induced by the resonant current I1 flowing through the heating coil L1, generating a corresponding resonant sampling voltage U1. The measurement voltage output by the measurement coils (including the measurement voltages of the first measurement sub-coil L2 and the second measurement sub-coil L3) is denoted as U2.

[0109] When the object to be heated 200 is placed on the heating coil L1, the heating coil L1 induces mutual induction with the inductance Lr of the object to be heated 200, thereby generating a corresponding induced current Ir, where the induced current Ir flows through the inductance Lr and the equivalent thermal resistance Rz.

[0110] When the heating coil L1 generates a mutual induction M1r with the induction inductance Lr of the object to be heated 200, the following formula is satisfied.

[0111]

number

[0112] In the present application, the second measurement sub-coil L3 of the measurement coil mutually induces with the heating coil L1, and the first measurement sub-coil L2 mutually induces with both the heating coil L1 and the heated object 200. Therefore, the induction inductance Lr of the heated object 200 generates a mutual induction Mr2 with the first measurement sub-coil L2, but does not generate a mutual induction with L3. The heating coil L1 generates a mutual induction M13 with the second measurement sub-coil L3, and generates a mutual induction M12 with the first measurement sub-coil L2.

[0113] For the convenience of subsequent calculations, the measurement coil 720 may be corrected in advance. When the heated object 200 is not placed on the heating unit 710, the measurement coil 720 sets the voltage difference between the two output ends to a predetermined value, thereby completing the correction. Optionally, the predetermined value may be 0, thereby completing the zeroing correction, and the measurement voltage U2 output by the measurement coil 720 is only due to the mutual induction Mr2 between the first measurement sub-coil L2 and the induction inductance Lr of the heated object 200. In the following, a case where the voltage difference between the two output ends after correction is 0 will be described as an example.

[0114] Specifically, when the heated object 200 is placed, the induction inductance Lr generates a mutual induction Mr2 with respect to the first measurement sub-coil L2, and when the heated object 200 is not placed, the induction inductance Lr does not generate a mutual induction Mr2 with respect to the first measurement sub-coil L2, so that when the heated object 200 is not placed on the heating coil L1, the voltage difference between the two output ends of the measurement coil 720 is set to 0, thereby performing zero correction on the measurement coil 720. At this time, the voltage difference between the different ends of the first measurement sub-coil L2 and the second measurement sub-coil L3 is close to 0, that is, jωM13=jωM12, and zero correction is performed on the first measurement sub-coil L2 and the second measurement sub-coil L3, that is, the initial U2=0 is obtained.

[0115] When the target 200 is placed on the heating coil L1, the induced inductance Lr of the target 200 generates a mutual induction Mr2 with respect to the first measurement sub-coil L2, but does not generate a mutual induction with respect to the second measurement sub-coil L3, and satisfies jωM13=jωM12 after performing zero correction on the mutual induction M12 of the heating coil L1 with respect to the first measurement sub-coil L2 and the mutual induction M13 of the heating coil L1 with respect to the second measurement sub-coil L3. Therefore, the measurement voltage U2 output by the measurement coil 720 is generated only by the induced inductance Lr of the target 200 generating a mutual induction Mr2 with respect to the first measurement sub-coil L2, that is, as follows:

[0116]

number

[0117] In other words, after the zeroing correction of the measurement coil 720, a mutual induction M13 is generated between the second measurement sub-coil L3 and the heating coil L1, and the mutual induction M12 of the heating coil L1 with respect to the first measurement sub-coil L2 is canceled out, so that the measurement voltage subsequently output by the measurement coil 720 is generated only by the induced inductance Lr of the heated object 200 generating a mutual induction Mr2 with respect to the first measurement sub-coil L2.

[0118] Therefore, by substituting the above equation (1) into equation (2), we obtain the following.

[0119]

number

[0120] In formula (3), the resonant current I1 is also measured by the sampling coil L4. Specifically, U1 is the mapping voltage of I1, so the resonant current I1 can be obtained by the resonant collection voltage U1 output by the sampling coil L4. U2 is the measurement voltage output by the measurement coil 720. When the inductance values ​​of the heating coil L1, the first measurement sub-coil L2, the second measurement sub-coil L3, the sampling coil L4, and the inductance Lr are specified, and their relative positions are specified, M1r and Mr2 can also be specified. Therefore, the magnitude of the thermal resistance Rz of the heated object 200 can be calculated by the above formula (3).

[0121] Lr is the induction inductance of the heated object 200, and the heated object 200 is generally a cooking pot, so the temperature coefficient of the induction inductance Lr is small, but the equivalent thermal resistance Rz has a large temperature coefficient, and the temperature coefficient of most stainless steel or iron materials is between 0.001 and 0.007 (20°C). Therefore, when U2 and I1 are measured, the thermal resistance Rz of the heated object 200 can be derived, and then the temperature of the heated object 200 can be obtained according to the preset thermal resistance-temperature function T=f(Rz).

[0122] Furthermore, regarding data processing in the heating circuit 100, as can be seen in combination with equation (3), the equivalent thermal resistance Rz of the heated object 200 can be determined based on the measurement voltage U2 and the resonant collection voltage U1, and the temperature of the heated object 200 can be determined based on the equivalent thermal resistance Rz.

[0123] For example, samples of the waveforms of the resonant collection voltage U1 and the measurement voltage U2 are taken by a high-speed AD and stored in memory, and then data processing is performed. Since the resonant collection voltage U1 and the measurement voltage U2 are AC, and it can be seen from equation (3) that the measurement voltage U2 is a non-standard function, the values ​​of the resonant collection voltage U1 and the measurement voltage U2 cannot be obtained directly. Furthermore, it is necessary to perform digital signal processing on the waveforms, such as DFT (Discrete Fourier Transform) processing, which involves selecting a finite discrete frequency sequence of length M (1 to 10) and converting the N-th trigonometric function U 2N =C V2N *cos(ω Nt +Φ V2N ) and similarly, for U1, select a finite discrete frequency sequence of length M and calculate the Nth trigonometric function U 1N =C V1N *sin(ω Nt +Φ V1N This involves parsing

[0124] U 2N and U 1NSince the excitation source of is the same, the point of selecting the discrete frequency is also the same, so the frequency of both is also the same, i.e., ω Nt and C V2N and C V1N is U 2N and U 1N Therefore, U 1N and U 2N By only obtaining the phase difference ΔΦ between the measured voltage U2 and the resonant collection voltage U1, Rz can be indirectly related, and there is no need to compare the specific values ​​of the measured voltage U2 and the resonant collection voltage U1. In addition, in order to reduce interference factors, the fundamental waves of U1 and U2 can preferably be selected as the comparison object.

[0125] Specifically, the phase difference ΔΦ can be obtained by the following method.

[0126] 1) Obtain the ratio of the measured voltage U2 to the resonant collection voltage U1 and perform an arctangent function operation on the ratio to obtain the phase difference between the measured voltage U2 and the resonant collection voltage U1. Formula: tan(Φ V2N -Φ V1N )=C V2N *cos(ω Nt +Φ V2N ) / C V1N *sin(ω Nt +Φ V1N ), tan(Φ V1N -Φ V2N ) The arctangent function arctan is ΔΦ=Φ V1N -Φ V2N can be obtained.

[0127] 2) Compare the waveforms of the measured voltage U2 and the resonant collection voltage U1 to obtain the phase difference between the measured voltage U2 and the resonant collection voltage U1. As shown in FIG. 20, FIG. 20 is a waveform diagram of the measured voltage and the resonant collection voltage of the present application. U 1N Starting from point a of the voltage waveform, U 2N The time it takes for the voltage to reach point b is recorded, and ΔΦ is the phase difference, where points a and b are the same voltage value.

[0128] 3) A comparator compares the measured voltage U2 with the resonant collection voltage U1 to obtain the phase difference between the measured voltage U2 and the resonant collection voltage U1. For example, U 1N and U 2N is output through the I / O interface of U1, 1N and U 2N are accessed as the positive and negative inputs of the comparator, thereby obtaining the phase difference ΔΦ.

[0129] Also, those skilled in the art may obtain the phase difference ΔΦ by other methods, and detailed description will be omitted here. After obtaining the phase difference ΔΦ, ΔΦ corresponding to the thermal resistance Rz at a temperature (-50° to 400°) is measured, and then the relational equation T=f(ΔΦ) between the two is established. When actually using, the temperature of the heating target 200 can be obtained from the table or the relational equation between the two.

[0130] The above introduces the principle of the resonant heating temperature measuring circuit of the present application. By simply collecting the measurement signal and the sampling signal in the resonant heating temperature measuring circuit 70, the temperature of the heated object can be obtained by data processing. However, if the collected electrical parameters in the resonant heating temperature measuring circuit are directly processed, the temperature measuring system is likely to burn out. Therefore, it is also necessary to process the electrical parameters in the signal processing circuit to prevent the temperature measuring system from burning out. Referring to FIG. 21, FIG. 21 is a structural schematic diagram of yet another embodiment of the signal processing circuit in the heating circuit of the present application.

[0131] The signal processing circuit 700 may include a bias circuit F, a clamp circuit G, and an amplifier circuit J. The bias circuit F is connected to the output terminal of the measuring coil 720 or the sampling coil 730, and biases the negative voltage of the processed signal in the forward direction to obtain a bias signal having a complete waveform with a positive amplitude value. Here, the amplitude value range may be 0 to a reference voltage VCC.

[0132] The clamp circuit G is connected to the bias circuit F and can clamp the high voltage portion of the bias signal, thereby obtaining a clamp signal to prevent the bias signal from flowing directly to the downstream circuit and causing excessive energy to burn out the circuit. The amplifier circuit J is connected to the clamp circuit G and can amplify and output the clamp signal, thereby obtaining a processed output signal.

[0133] With the above method, after the processed signal is processed by the signal processing circuit, all voltage signals that originally have positive and negative directions are converted into positive voltages of complete amplitude, and the high voltage parts of the original voltage signals can be clamped, and only the low voltage parts are sent to the subsequent circuit for processing, thereby avoiding burning out of the temperature measuring system and facilitating subsequent data processing.

[0134] 22, which is a structural schematic diagram of yet another embodiment of the signal processing circuit in the heating circuit of the present application. The signal processing circuit 700 in this embodiment may include a voltage follower circuit H and / or a filter circuit I in addition to a bias circuit F, a clamp circuit G and an amplifier circuit J.

[0135] The voltage follower circuit H is connected between the clamp circuit G and the subsequent circuit, and can form a high impedance state between the clamp circuit and the subsequent circuit, thereby preventing the subsequent circuit from affecting the clamp signal output by the clamp circuit G. The filter circuit I is connected between the amplifier circuit J and the previous circuit, and may perform filtering on the clamp signal before it is input to the amplifier circuit J to remove DC components in the signal.

[0136] Here, when the signal processing circuit 700 includes a voltage follower circuit H and a filter circuit I, the latter circuit of the voltage follower circuit H includes an amplifier circuit J and a filter circuit I (as shown in FIG. 22), and the former circuit of the filter circuit I includes a clamp circuit G and a voltage follower circuit H (as shown in FIG. 22). When the signal processing circuit 700 includes the voltage follower circuit H but does not include the filter circuit I, the latter circuit of the voltage follower circuit H is the amplifier circuit J, and when the signal processing circuit 700 includes the filter circuit I but does not include the voltage follower circuit H, the former circuit of the filter circuit I is the clamp circuit G.

[0137] Also, in some embodiments, for example, when the processed signal is a sampling signal output by the sampling coil 730, since it is a resonant current output by the sampling coil 730, the signal processing circuit 700 may further include a load resistor E to convert the collected resonant current into a resonant sampling voltage. The load resistor E may be connected to a first node between the output end of the sampling coil 730 and the bias circuit F, so that the resonant current output by the sampling coil 730 can be converted into a resonant sampling voltage at the first node as the processed signal to be processed by the bias circuit F.

[0138] When the processed signal is a measurement signal output by the measurement coil 720, the signal processing circuit 700 does not need to include a load resistor E because the measurement signal output after the measurement coil 720 is compensated is a measurement voltage.

[0139] Referring to Fig. 23, Fig. 23 is a schematic diagram of a circuit corresponding to the signal processing circuit of Fig. 22. The signal processing circuit 700 includes an input terminal a and an output terminal b, the input terminal a is connected to the measuring coil 720 or the sampling coil 730 and used to acquire the processed signal, and the output terminal b is used to output the voltage signal after the signal processing is completed. Here, the voltage signal after the signal processing is sent to the main control chip for data processing, and further acquires the temperature of the heated object 200.

[0140] When the signal to be processed is a sampling signal, the signal processing circuit 700 may include a load resistor E, that is, resistor R0 in FIG. 20. The resistance value of R0 may be 0 to 100 KΩ. When the signal to be processed is a measurement signal, the signal processing circuit 700 does not need to include resistor R0.

[0141] The bias circuit F may include a first resistor R1 and a second resistor R2. One end of the first resistor R1 may be connected to an output end of the measurement coil 720 or the sampling coil 730, and the other end of the first resistor R1 may be connected to one end of the second resistor R2, and the other end of the second resistor R2 is connected to a reference voltage VCC, where a second node between the first resistor R1 and the second resistor R2 is the output end of the bias circuit F. Here, the resistance values ​​of the first resistor R1 and the second resistor R2 may be 1KΩ to 100KΩ.

[0142] The clamp circuit G may include a diode D1 having an anode connected to the output terminal of the bias circuit F and a cathode connected to a reference voltage VCC. Here, a third node between the anode of the diode D1 and the output terminal of the bias circuit F is defined as the output terminal of the clamp circuit G.

[0143] The voltage follower circuit H includes a first amplifier N1, the first input terminal of which is connected to the output terminal of the clamp circuit G, and the second input terminal of which is connected to the output terminal of the clamp circuit G. Here, the first input terminal may be the in-phase input terminal of the first amplifier N1, and the second input terminal may be the inverted phase input terminal of the first amplifier N1, as shown in FIG.

[0144] The filter circuit I may include a filter capacitor C1. One end of the filter capacitor C1 may be connected to the output end of the voltage follower circuit H, i.e., the node between the second input end and the output end of the first amplifier N1, and the other end of the filter capacitor C1 may be connected to the input end of the amplifier circuit J. The filter capacitor C1 may be selected to have a capacitance of 100 pF to 10 μF.

[0145] The amplifier circuit J may include a third resistor R3, a fourth resistor R4, and a second amplifier N2. A first input terminal of the second amplifier N2 may be connected to an output terminal b via a fourth resistor R4, and a second input terminal of the second amplifier N2 may be connected to a previous stage circuit via a third resistor R3. This allows a processed output signal to be output from the output terminal b.

[0146] Here, the first input terminal of the second amplifier N2 may be an in-phase input terminal, and the second input terminal of the second amplifier N2 may be an inverted-phase input terminal. The third resistor R3 and the fourth resistor R4 are proportional resistors of the operational amplifier, and may have a resistance value of 10Ω to 100KΩ.

[0147] The process in which the signal processing circuit 700 performs signal processing on the processed signal (taking the measurement signal as an example) is as follows: The measurement coil 720 induces the resonant periodic voltage signal (wherein the voltage signal has a forward direction and a reverse direction) radiated by the heated object to form a measurement signal. The measurement signal passes through the first resistor and the second resistor to raise the bias voltage division, and raise the negative voltage above the zero point to form a bias signal. When the bias signal passes through the clamp of the diode D1, the high-voltage part of the bias signal is clamped, and the low-voltage signal is selected and sent to the first amplifier N1 as an emitter follower, and the first amplifier N1 is used to output the clamp signal, and the first amplifier N1 is used to form a high impedance state between the subsequent circuit and the clamp circuit, to prevent the subsequent circuit from affecting the clamp signal output by the clamp circuit. After that, the signal passes through the filter capacitor C1 for filtering, and then sent to the second amplifier N2 as an amplifier circuit for signal amplification, and then output a processed signal.

[0148] Referring to Fig. 24, Fig. 24 is a structural schematic diagram of one embodiment of the cooking utensil of the present application. The cooking utensil 900 includes a heating circuit 800, where the heating circuit 800 has the same heating circuit structure as that in any one of the above embodiments, and the specific structure can be referred to the above embodiments, and detailed description is omitted here.

[0149] Here, the cooking utensil 900 may be an appliance such as an electromagnetic stove, an electric rice cooker, or an electric pressure cooker, and detailed description thereof will be omitted here.

[0150] The above is merely an embodiment of the present application, and does not limit the scope of the patent of the present application. For the same reason, any equivalent structure or equivalent process transformation made by utilizing the contents of the specification and drawings of the present application, and any direct or indirect application to other related technical fields, are all included in the patent protection scope of the present application.

Claims

1. A heating unit including a heating coil for resonantly heating an object to be heated; a measurement coil including a first measurement subcoil that mutually induces with the heating coil and the object to be heated, and a second measurement subcoil that mutually induces with the heating coil, wherein a pair of ends of the first measurement subcoil and the second measurement subcoil having the same name are connected to each other, and another pair of ends of the first measurement subcoil and the second measurement subcoil having the same name output a measurement signal as an output end of the measurement coil, and wherein mutual induction of the heating coil with respect to the first measurement subcoil is cancelled out by mutual induction generated between the second measurement subcoil and the heating coil; the measurement signal output by the measurement coil includes a measurement voltage, the measurement voltage being generated only by an inductive inductance of the heated object generating a mutual induction with the first measurement sub-coil; wherein the measurement signal is used in combination with resonant electrical parameters of the heating coil collected by measurement to determine the temperature of the heated object; A heating circuit comprising:

2. When the object to be heated is not placed on the heating unit, the voltage difference between the two output terminals of the measurement coil is set to a predetermined value, thereby completing the correction.

2. The heating circuit according to claim 1 .

3. the first measurement sub-coil is placed on the disk surface of the heating coil such that a plane of the first measurement sub-coil and a plane of the heating coil form a predetermined angle, the predetermined angle being within a range of 0 to 45 degrees; 3. The heating circuit according to claim 2 .

4. The predetermined angle is 0 degrees, and the first measurement sub-coil is placed parallel to and above the disk surface of the heating coil.

4. The heating circuit according to claim 3.

5. a collection unit for collecting the resonant electrical parameters of the heating coil; wherein the collection unit is a collection coil for collecting the resonant electrical parameters of the heating coil; or a resistive sampling circuit having one end coupled to the resonant loop of the heating unit and another end grounded to collect the resonant electrical parameters of the heating coil; 3. The heating circuit according to claim 2 .

6. a processing circuit connected to the output of the measurement coil and the output of the collection unit to collect the measurement signal and the resonant electrical parameter, to determine a thermal resistance parameter of the heated object based on the measurement signal and the resonant electrical parameter, and to determine a temperature of the heated object based on the thermal resistance parameter.

6. A heating circuit as claimed in claim 5.

7. The resonant electrical parameters collected and output by the collection unit include a resonant collected voltage corresponding to a resonant current flowing through the heating coil; the processing circuitry compares the measured voltage with the resonant collected voltage to obtain a phase difference therebetween to identify the thermal resistance parameter of the heated object; 7. A heating circuit as claimed in claim 6.

8. The manner in which the processing circuitry obtains the phase difference between the measurement voltage and the resonant collection voltage is obtaining a ratio of the measured voltage and the resonant collection voltage and processing the ratio to obtain a phase difference between the measured voltage and the resonant collection voltage; or comparing waveforms of the measured voltage and the resonant collection voltage to obtain a phase difference between the measured voltage and the resonant collection voltage; or comparing the measured voltage with the resonant collection voltage with a comparator to obtain a phase difference between the measured voltage and the resonant collection voltage; 8. A heating circuit as claimed in claim 7.

9. The heating unit further includes a resonant capacitor connected in series or parallel to the heating coil to form a resonant loop of the heating unit, The heating circuit further comprises: a rectification unit for rectifying AC power into DC power; an energy storage capacitor connected to the rectifier unit for storing DC electrical energy; a DC supplement unit connected to the energy storage capacitor for introducing DC supplemental electric energy; an inverter unit connected to the resonant loop of the heating unit, receiving an oscillating frequency signal to be driven by the stored DC electric energy and the DC supplemental electric energy to cause the heating unit to perform resonant heating at a resonant frequency; Wherein, the inverter unit includes a half-bridge resonant module or a single tube resonant module; 2. The heating circuit according to claim 1 .

10. The temperature measuring circuit further includes a temperature measuring unit, a trigger unit, and a processing unit; The temperature measuring unit has an input end connected to a power supply power source and an excitation power source, and is used for inputting a power supply signal and an excitation signal. When the excitation signal is smaller than an excitation threshold, the temperature measuring signal is excited by the excitation signal to generate a temperature measuring signal, where when the excitation signal is smaller than the excitation threshold, the power supply signal is within a zero-crossing range, and the zero-crossing range is centered on a zero-crossing point; the trigger unit has an input end connected to the power supply power source and / or the excitation power source for inputting the power supply signal and / or the excitation signal, and generates a trigger signal based on the power supply signal and / or the excitation signal; The processing unit has an input connected to an output of the trigger unit, and is configured to determine a start time of collecting the temperature signal according to the trigger signal, the start time corresponding to the zero crossing point.

2. The heating circuit according to claim 1 .

11. the trigger unit includes a zero-cross circuit connected between the power supply and the processing unit for inputting the power supply signal, the zero-cross circuit including a double-edge interrupt comparator, the zero-cross signal output by the double-edge interrupt comparator being the trigger signal, the zero-cross signal being a square wave signal; an input end of the processing unit is connected to an output end of the double edge interrupt comparator, and collects an interrupt time of a falling edge of a previous square wave and an interrupt time of a rising edge of a next square wave from the zero cross signal, and determines the start time according to the interrupt time of the rising edge and the interrupt time of the falling edge; 11. A heating circuit as claimed in claim 10.

12. the processing unit determines a zero-crossing point time as an intermediate time between an interrupt time of a rising edge and an interrupt time of a falling edge, and determines a start time as a time obtained by delaying the zero-crossing point time by a first time; 12. A heating circuit as claimed in claim 11.

13. The trigger unit includes a comparator, a first input end of the comparator is connected to an excitation power source and used for inputting an excitation signal, a second input end of the comparator is connected to a threshold power source and used for inputting the excitation threshold, and an output end of the comparator is connected to an input end of the processing unit and outputs a comparison signal as the trigger signal, the comparison signal being a square wave signal, where the square wave indicates that the excitation signal is smaller than the excitation threshold; The processing unit sets an interrupt time of a rising edge of a square wave in the comparison signal as a start time.

11. A heating circuit as claimed in claim 10.

14. The trigger unit includes a transistor, a base electrode of the transistor is connected to the power supply to input the power supply signal, an emitter electrode of the transistor is connected to the excitation power supply to input the excitation signal, and a collector electrode of the transistor is connected to an input end of the processing unit to output the trigger signal, the trigger signal being a square wave signal, where the square wave indicates that the power supply signal is smaller than the excitation signal; The processing unit sets an interrupt time of a rising edge of a square wave in the trigger signal as a start time.

11. A heating circuit as claimed in claim 10.

15. The processing unit further determines, as the start time, a time obtained by delaying the interrupt time of the rising edge by a second time.

15. A heating circuit as claimed in claim 14.

16. The processing unit determines an end time of the collection of the temperature measurement signal to be a time obtained by delaying the start time by a third time.

11. A heating circuit as claimed in claim 10.

17. The third time is 10 us to 2 ms; 17. A heating circuit as claimed in claim 16.

18. the excitation signal is between 5V and 50V; 11. A heating circuit as claimed in claim 10.

19. The heating circuit further includes a signal processing circuit connected to an output end of the measuring coil or sampling coil of the heating circuit for processing a processed signal output by the measuring coil or sampling coil, wherein the signal processing circuit includes: a bias circuit connected to an output terminal of the measuring coil or the sampling coil, for forward biasing the negative voltage of the processed signal to obtain a bias signal having a complete waveform with a positive amplitude value; a clamp circuit connected to the bias circuit and configured to clamp a high-voltage portion of the bias signal to obtain a clamp signal; an amplifier circuit connected to the clamp circuit and configured to amplify and then output the clamp signal to obtain a processed output signal; 2. The heating circuit according to claim 1 .

20. a voltage follower circuit connected between the clamp circuit and a subsequent circuit, forming a high impedance state between the clamp circuit and the subsequent circuit, thereby preventing the subsequent circuit from affecting the clamp signal output by the clamp circuit; 20. A heating circuit as claimed in claim 19.

21. a filter circuit connected between the amplifier circuit and a previous stage circuit, for filtering the clamp signal before it is input to the amplifier circuit; 20. A heating circuit as claimed in claim 19.

22. When the processed signal is a sampling signal output by the sampling coil, the signal processing circuit further a load resistor connected to a first node between an output end of the sampling coil and the bias circuit, for converting a resonant current output by the sampling coil into a resonant sampling voltage at the first node, which is the processed signal to be processed by the bias circuit; 20. A heating circuit as claimed in claim 19.

23. the bias circuit includes a first resistor and a second resistor; One end of the first resistor is connected to an output end of the measurement coil or the sampling coil, the other end of the first resistor is connected to one end of the second resistor, and the other end of the second resistor is connected to a reference voltage, and a second node between the first resistor and the second resistor is an output end of the bias circuit.

20. A heating circuit as claimed in claim 19.

24. the clamp circuit includes a diode having an anode connected to the output terminal of the bias circuit and a cathode connected to a reference voltage, and a third node between the anode of the diode and the output terminal of the bias circuit is defined as an output terminal of the clamp circuit.

20. A heating circuit as claimed in claim 19.

25. the voltage follower circuit includes a first amplifier having a first input terminal connected to the output terminal of the clamp circuit and a second input terminal connected to the output terminal; 21. A heating circuit as claimed in claim 20.

26. the amplifier circuit includes a third resistor, a fourth resistor, and a second amplifier; wherein the first input terminal of the second amplifier is connected to the output terminal via the fourth resistor, the second input terminal of the second amplifier is connected to a previous stage circuit via the third resistor, and the output terminal outputs the processed output signal.

20. A heating circuit as claimed in claim 19.

27. A heating circuit comprising the heating circuit according to any one of claims 1 to 26. A cooking utensil characterized by

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