CN113654676A

CN113654676A - Heating temperature measurement circuit, temperature measurement circuit and cooking device

Info

Publication number: CN113654676A
Application number: CN202010399011.7A
Authority: CN
Inventors: 江德勇; 苏畅; 郑量; 马志海; 江太阳; 黄庶锋; 雷俊
Original assignee: Foshan Shunde Midea Electrical Heating Appliances Manufacturing Co Ltd
Current assignee: Foshan Shunde Midea Electrical Heating Appliances Manufacturing Co Ltd
Priority date: 2020-05-12
Filing date: 2020-05-12
Publication date: 2021-11-16
Anticipated expiration: 2040-05-12
Also published as: CN113654676B

Abstract

The application discloses heating temperature measurement circuit, temperature measurement circuit and culinary art device should heat the temperature measurement circuit and include: a heating coil for heating the metal object when energized; the device comprises an excitation coil and a receiving coil, wherein the excitation coil generates an alternating magnetic field when being electrified, so that a metal object generates an eddy current, and the receiving coil generates a receiving signal under the action of the eddy current; and a switching circuit connected to the heating coil for energizing the exciting coil and cutting off the conduction path of the heating coil when measuring the temperature. By the mode, the heating coil can be prevented from interfering with temperature measurement signals, and the temperature measurement precision is improved.

Description

Heating temperature measurement circuit, temperature measurement circuit and cooking device

Technical Field

The application relates to the technical field of temperature detection, in particular to a heating temperature measuring circuit, a temperature measuring circuit and a cooking device.

Background

Generally, when a metal object is heated, it is necessary to detect and control the temperature of the metal object, and in order to control the cooking device well, taking a cooking device as an example, it is necessary to measure the temperature of the metal object so that the cooking device heats the metal object. For example, when the metal object is heated by using a set heating curve, it is necessary to detect whether the temperature of the metal object satisfies the set heating curve, and for example, when the temperature of the metal object is abnormal, the cooking device may suspend heating.

One existing method is to detect the temperature of a metal object through a thermistor, but due to the position arrangement problem of the thermistor, the temperature detection is inaccurate, and the detection of the temperature jump of the local position of the metal object is not sensitive enough.

Disclosure of Invention

For solving above-mentioned problem, this application provides a heating temperature measurement circuit, temperature measurement circuit and culinary art device, can prevent heating coil to the interference of temperature measurement signal, improves the precision of temperature measurement.

The technical scheme adopted by the application is as follows: provided is a heating temperature measuring circuit, including: a heating coil for heating the metal object when energized; the device comprises an excitation coil and a receiving coil, wherein the excitation coil generates an alternating magnetic field when being electrified, so that a metal object generates an eddy current, and the receiving coil generates a receiving signal under the action of the eddy current; and a switching circuit connected to the heating coil for energizing the exciting coil and cutting off the conduction path of the heating coil when measuring the temperature.

The switching circuit is also used for electrifying the heating coil and the exciting coil when the temperature is not measured.

The heating coil and the exciting coil are arranged in series, two ends of the switching circuit are respectively connected with two ends of the heating coil, and the switching circuit is conducted during temperature measurement so as to cut off a conducting path of the heating coil.

The switching circuit is also used for electrifying the heating coil and cutting off the conductive path of the exciting coil when the temperature is not measured.

The heating coil and the exciting coil are arranged in parallel, the switching circuit comprises a selection switch, the selection switch is respectively connected with one end of the heating coil and one end of the exciting coil, the other end of the heating coil is connected with the other end of the exciting coil, and the selection switch is used for selectively conducting a conducting path of the exciting coil when temperature measurement is carried out and selectively conducting a conducting path of the heating coil when temperature measurement is not carried out.

Wherein the heating coil and the exciting coil are two sections of the same coil.

The receiving coil comprises a first differential coil and a second differential coil, one homonymous end of the first differential coil is connected with one homonymous end of the second differential coil, and the other homonymous end of the first differential coil and the other homonymous end of the second differential coil generate a receiving signal, wherein the first differential coil or the second differential coil is arranged coaxially with the heating coil.

Wherein, the driving frequency of the temperature measuring interval is 15KHz-60 KHz.

Another technical scheme adopted by the application is as follows: the temperature measuring circuit is provided, the temperature measuring circuit and the heating circuit are respectively and independently arranged and are used for heating and measuring the temperature of a metal object, and the temperature measuring circuit comprises a sampling circuit, an exciting coil and a receiving coil which are connected in series; the sampling circuit samples the excitation signal when being electrified; the exciting coil generates an alternating magnetic field when being electrified, so that the metal object generates an eddy current; the receiving coil generates a receiving signal under the action of the eddy current; wherein the excitation signal and the received signal are used to determine the temperature of the metal object.

The temperature measuring circuit further comprises a resonant capacitor, and the resonant capacitor is connected with the exciting coil in parallel.

The temperature measuring circuit further comprises a resonant capacitor, and the resonant capacitor is connected with the exciting coil in series.

Wherein, temperature measurement circuit still includes: an excitation source; the sampling circuit, the exciting coil and the receiving coil are connected in series on a conductive path between the exciting source and the driving circuit; the driving circuit is controlled by the driving signal to realize conduction and closing.

Another technical scheme adopted by the application is as follows: a cooking device is provided, which comprises the heating temperature measuring circuit or the temperature measuring circuit.

The application provides a heating temperature measurement circuit includes: a heating coil for heating the metal object when energized; the device comprises an excitation coil and a receiving coil, wherein the excitation coil generates an alternating magnetic field when being electrified, so that a metal object generates an eddy current, and the receiving coil generates a receiving signal under the action of the eddy current; and a switching circuit connected to the heating coil for energizing the exciting coil and cutting off the conduction path of the heating coil when measuring the temperature. By the mode, the heating coil is powered off when temperature measurement is carried out, signals of the exciting coil and the receiving coil cannot be influenced, and temperature measurement is further more accurate.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts. Wherein:

FIG. 1 is a schematic structural diagram of an embodiment of a cooking device provided in the present application;

FIG. 2 is a schematic circuit diagram of a first embodiment of a heating temperature measurement circuit provided herein;

FIG. 3 is a schematic circuit diagram of a second embodiment of a heating temperature measurement circuit provided herein;

FIG. 4 is an equivalent circuit diagram of the excitation coil, the receiving coil, and the metal object of the present application;

FIG. 5 is a schematic circuit diagram of a third embodiment of a heating temperature measuring circuit according to the application;

FIG. 6 is a waveform schematic diagram of the circuit of FIG. 5 in operation;

FIG. 7 is a schematic circuit diagram of a fourth embodiment of a heating temperature measuring circuit according to the application;

FIG. 8 is a schematic electrical circuit diagram of a heating circuit provided herein;

FIG. 9 is a schematic circuit diagram of a first embodiment of a thermometry circuit provided herein;

FIG. 10 is a schematic waveform diagram of the heating circuit and thermometry circuit of FIGS. 8 and 9;

FIG. 11 is a schematic circuit diagram of a second embodiment of a thermometry circuit provided herein;

fig. 12 is a schematic structural diagram of an embodiment of a coil disk provided in the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting of the application. It should be further noted that, for the convenience of description, only some of the structures related to the present application are shown in the drawings, not all of the structures. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The terms "first", "second", etc. in this application are used to distinguish between different objects and not to describe a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of a cooking device 10 provided in the present application, which includes a panel 11, a heating coil 12, an exciting coil (not shown in fig. 1), and a receiving coil 13.

Wherein the panel 11 comprises a first side which is a heating surface for placing the metal object 20 and a second side on which the heating coil 12, the exciting coil (not shown in fig. 1) and the receiving coil 13 are arranged. Alternatively, the panel 11 is made of a non-metallic material.

Wherein, the heating coil 12 generates an alternating magnetic field when being electrified, and the metal object generates an eddy current under the action of the alternating magnetic field, so as to realize the heating of the heating coil 12 to the metal object 20 (cookware).

When the temperature of the metal object is measured, an excitation signal is provided for the excitation coil, so that the excitation coil generates an alternating magnetic field, the metal object generates an electric eddy current under the action of the alternating magnetic field, the electric eddy current further enables the receiving coil to generate a receiving signal through electromagnetic induction, and the measured temperature of the metal object is determined according to the excitation signal and the receiving signal.

With reference to fig. 2, fig. 2 is a schematic circuit diagram of a first embodiment of the heating and temperature measuring circuit provided by the present application, where the heating and temperature measuring circuit includes a power input terminal L/N, a fuse F1, a rectifier bridge D1, a choke coil L1, a filter capacitor C1, a resonant capacitor C2, a sampling coil L3 (for acquiring an excitation signal Ui), a heating coil LX1, a power tube IGBT, an excitation power supply VSS, a diode D4, and an excitation coil LX 2.

In an alternative embodiment, the receiving coil 13 includes a first differential coil Ls1 and a second differential coil Ls2, wherein Ls1 and Ls2 are connected at the same name end, so as to eliminate the influence of the heating coil LX1 and obtain a differential signal. In an alternative embodiment, the first differential coil Ls1 and the heating coil 12 are arranged coaxially. In one embodiment, the first differential coil Ls1 may be disposed directly above the heating coil 12, in another embodiment, the first differential coil Ls1 and the heating coil 12 are disposed on the same plane, and the first differential coil Ls1 is disposed inside the heating coil 12. Of course, in other embodiments, the first differential coil Ls1 and the heating coil 12 may be arranged in other ways, which are not listed here.

With reference to fig. 3, fig. 3 is a schematic circuit diagram of a second embodiment of the heating and temperature measuring circuit provided by the present application, where the heating and temperature measuring circuit includes a power input terminal L/N, a fuse F1, a rectifier bridge D1, a choke coil L1, a filter capacitor C1, a resonant capacitor C2, a sampling coil L3 (for acquiring an excitation signal Ui), a heating coil LX1, a power tube IGBT, an excitation power supply VSS, a diode D4, and an excitation coil LX 2.

In addition, the heating temperature measurement circuit further comprises a zero-cross circuit (composed of diodes D2 and D3, resistors R1, R2 and R3 and a comparator CMP 1), an IGBT driving module DR1 and a main control chip IC 1. The zero-crossing circuit is used for detecting whether the power supply voltage is close to 0 or not, so that the active chip IC1 outputs a corresponding driving control signal according to the power supply voltage.

The following explains the principle of temperature detection:

when the exciting coil is close to the metal object (metal), the surface of the metal object is subjected to the action of the alternating magnetic field to generate an eddy current, and at this time, the exciting coil generates an equivalent circuit of the eddy current, as shown in fig. 4, fig. 4 is an equivalent circuit diagram of the exciting coil, the receiving coil and the metal object in the present application, where Rz is the equivalent resistance of the metal object, Lz is the equivalent inductance of the metal object, and the eddy current can be expressed as: iz ═ I3 · j ω M/(Rz + j ω Lz); where M is the mutual inductance between the excitation coil and the metal object.

As temperature changes, Lz remains substantially constant while Rz ═ f (t) changes with temperature, so the phase difference between Iz and I3 is as follows, and the phase difference changes with temperature.

Δφ＝∠Iz-∠I3＝π/2-arctan(ωLz/Rz)＝arctan(Rz/ωLz)

To accurately measure the eddy current Iz, a pair of differential coils is used to receive the signal in one embodiment, wherein Ls1, Ls2 are the self-inductances of the first differential coil and the second differential coil, respectively; ms1, Ms2 are the mutual inductances between the first and second differential coils and the excitation coil, respectively, after the metal object is removed; mz1, Mz2 are the mutual inductances between the first and second differential coils and the metal object, respectively. In this embodiment, Ms1 ═ Ms2, Mz1 ≠ Mz2, and since the induced voltages of the excitation coil at the first differential coil and the second differential coil cancel each other out, the signal induced to the differential receiving coil by the eddy current on the metal object is not affected, and the open circuit output voltage of the differential receiving coil (i.e., the received signal Usr) is:

Usr＝Iz·jω(Mz1-Mz2)＝I3·jωM·jω(Mz1-Mz2)/(Rz+jωLz)

therefore, the temperature value of the metal object can be calculated by only measuring the phase difference between Usr and I3; therefore, the measurement process of this embodiment is: (1) outputting sine waves or square waves with fixed frequency on the exciting coil; (2) measuring the phase difference between a received signal Usr and the fundamental current of the exciting coil; (3) and calculating the temperature of the measured conductor according to the phase difference.

Practice shows that the temperature detection of the above embodiment is not accurate enough, and the above embodiment is further improved by an embodiment.

It is to be understood that since the heating coil LX1 and the exciting coil LX2 are connected in series, although temperature measurement is generally performed when the input power is close to 0 point, the heating coil affects the exciting coil and the receiving coil, and therefore, in one embodiment, a switching circuit may be provided to energize the exciting coil and cut off the conduction path of the heating coil when temperature measurement is performed. Thus, the heating coil does not act on the external circuit at the time of temperature measurement. This is further illustrated by the following examples.

Referring to fig. 5, fig. 5 is a schematic circuit diagram of a third embodiment of the heating and temperature measuring circuit provided by the application, where the heating and temperature measuring circuit includes a power input terminal L/N, a fuse F1, a rectifier bridge D1, a choke coil L1, a filter capacitor C1, a resonant capacitor C2, a sampling coil L3, a heating coil LX1, a power tube IGBT, an excitation power supply VSS, a diode D4, and an excitation coil LX 2.

In the embodiment, the heating coil LX1 and the exciting coil LX2 are connected in series, the heating temperature measuring circuit further comprises a switch K1, two ends of the switch K1 are respectively connected with two ends of the heating coil LX1, and the switch K1 is turned on during temperature measurement to cut off the conducting path of the heating coil LX 1.

It is to be understood that, in the present embodiment, at the time of heating, the switch K1 is turned off, and the heating coil LX1 and the excitation coil LX2 are simultaneously used as heating.

Alternatively, the switch K1 in this embodiment may be a transistor with a switching function, such as a triode or a MOS transistor, and the switching on and off of the transistor may be controlled by the main control chip.

Referring now to fig. 6, fig. 6 is a schematic diagram of waveforms for the operation of the circuit of fig. 5.

And entering a measurement interval in the vicinity of the zero point of the power supply voltage, wherein the interval range is 0.01 ms-2 ms. At this time, K1 is closed, and the switch LX2 works alone. During normal heating, K1 is switched off, and LX1 and LX2 jointly participate in resonance.

Referring to the PPG waveform, in the heating interval, fx is the normal power maintaining frequency, the driving frequency of the measuring interval is f0, and the range width of f0 is 15KHz-60 KHz. In an alternative embodiment, f0 is 15-45 KHz. Wherein f0 can be set to a fixed value, so that signal consistency is good. In this embodiment, the frequency value is lower than the free resonance frequency of the system.

In the present embodiment, a switch is connected in parallel to the heating coil LX1, and the heating coil LX1 can be short-circuited by the switch, and when heating, the switch is turned off, and the heating coil LX1 and the excitation coil LX2 are connected in series, and when measuring temperature, the switch is turned off, and the heating coil LX1 is short-circuited, and only the excitation coil LX2 is in a conduction path. In this way, the excitation coil LX2 can be used as heating during heating, and the heating area can be increased to improve the heating efficiency.

Referring to fig. 7, fig. 7 is a schematic circuit diagram of a fourth embodiment of the heating and temperature measuring circuit provided by the application, where the heating and temperature measuring circuit includes a power input terminal L/N, a fuse F1, a rectifier bridge D1, a choke coil L1, a filter capacitor C1, a resonant capacitor C2, a sampling coil L3, a heating coil LX1, a power tube IGBT, an excitation power supply VSS, a diode D4, and an excitation coil LX 2.

In the embodiment, the heating coil LX1 and the excitation coil LX2 are connected in parallel, the heating temperature measuring circuit further comprises a selection switch K2, the selection switch K2 is respectively connected with one end of the heating coil LX1 and one end of the excitation coil LX2, the heating coil LX1 is connected with the other end of the excitation coil LX2, the selection switch K2 is used for selectively conducting a conducting path of the excitation coil K2 when temperature measurement is carried out, and the conducting path of the heating coil K1 is selectively conducted when temperature measurement is not carried out.

It is to be understood that, in the present embodiment, only the heating coil LX1 is used as heating at the time of heating.

Alternatively, the selection switch K2 in this embodiment may be a single-pole double-throw switch, and the conduction direction of the switch may be controlled by the main control chip.

The working principle of this embodiment is similar to that of fig. 6 described above, and will not be described again here.

In the embodiment, a single-pole double-throw switch is used for switching between the heating coil LX1 and the exciting coil LX2, so that only one coil is connected into a conductive path at the same time, and mutual interference of signals between the two coils is avoided.

Different from the prior art, the heating temperature measurement circuit that this embodiment provided includes: a heating coil for heating the metal object when energized; the device comprises an excitation coil and a receiving coil, wherein the excitation coil generates an alternating magnetic field when being electrified, so that a metal object generates an eddy current, and the receiving coil generates a receiving signal under the action of the eddy current; and a switching circuit connected to the heating coil for energizing the exciting coil and cutting off the conduction path of the heating coil when measuring the temperature. By the mode, the heating coil is powered off when temperature measurement is carried out, signals of the exciting coil and the receiving coil cannot be influenced, and temperature measurement is further more accurate.

It is understood that the heating circuit and the temperature measuring circuit may be separately provided in order to prevent the heating coil from interfering with the exciting coil.

Referring to fig. 8, fig. 8 is a schematic circuit diagram of a heating circuit provided by the present application, where the heating circuit includes a rectifier bridge D1, a choke coil L1, a filter capacitor C1, a resonant capacitor C2, a heating coil LX1, and a power tube IGBT. In addition, with reference to fig. 2, the heating circuit may further include a power input terminal L/N, a fuse F1, and the like, and with reference to fig. 3, the heating circuit may further include a zero-crossing circuit, a main control chip, a driving circuit, and the like, which are not described herein again.

Referring to fig. 9, fig. 9 is a circuit schematic diagram of a first embodiment of the temperature measuring circuit provided by the present application, where the temperature measuring circuit includes an excitation power supply VSS, a sampling coil L3, a receiving coil (including Ls1 and Ls2), an excitation coil LX2, a resonant capacitor CX2, a power tube Q1, and a diode D2.

The exciting coil LX2 and the resonant capacitor CX2 are connected in parallel.

Referring to fig. 10, fig. 10 is a schematic diagram of waveforms of the heating circuit and the temperature measuring circuit in fig. 8 and 9. During heating, the high-speed on-off of the IGBT is controlled through a PPG waveform, and during measurement, the high-speed on-off of Q1 is controlled through PWM. The working frequency range is 15KHz-60 KHz. In one embodiment, 15-45 KHz can be selected.

In the above embodiments, the PPG waveform and the PWM waveform may be generated by the master control chip.

Referring to fig. 11, fig. 11 is a circuit schematic diagram of a second embodiment of the temperature measuring circuit provided by the present application, where the temperature measuring circuit includes an excitation power supply VSS, a sampling coil L3, a receiving coil (including Ls1 and Ls2), an excitation coil LX2, a resonant capacitor CX2, a power tube Q1, and a diode D2.

The exciting coil LX2 and the resonant capacitor CX2 are connected in series.

This embodiment is similar in principle to the embodiment of fig. 9 described above, and will not be described herein again.

Different from the prior art, the temperature measuring circuit provided by the embodiment comprises a sampling circuit, an exciting coil and a receiving coil which are connected in series; the sampling circuit samples the excitation signal when being electrified; the exciting coil generates an alternating magnetic field when being electrified, so that the metal object generates an eddy current; the receiving coil generates a receiving signal under the action of the eddy current; wherein the temperature of the metal object is determined by the excitation signal and the reception signal. Through the mode, the heating circuit and the temperature measuring circuit are separately arranged, and the heating circuit can not be driven during temperature measurement, so that the heating coil is powered off, signals of the exciting coil and the receiving coil cannot be influenced, and the temperature measurement is further more accurate.

Referring to fig. 12, fig. 12 is a schematic structural diagram of an embodiment of the coil disk provided by the present application, where the coil disk 120 includes a first coil 121 and a second coil 122, and the first coil 121 and the second coil 122 are connected end to form an integral coil disk 120.

Further, the coil panel 120 further includes a first connection end a, a second connection end b, and a third connection end c, where the first connection end a and the third connection end c are external connection ends, and the second connection end is a connection point of the first coil 121 and the second coil 122.

In combination with the circuits in the above embodiments, the first coil 121 and the second coil 122 may be implemented in series or in parallel as a heating coil and an exciting coil. For example, by connecting the first connection terminal a and the third connection terminal c, the parallel connection of the heating coil and the exciting coil can be realized.

It will be appreciated that the above-described method may be embodied in the form of program data stored on a storage medium and may be implemented by the master chip IC1 provided in the embodiment of fig. 3. In one embodiment, the master control chip IC1 may be a master control chip in a cooking appliance, which may be an induction cooker.

The coil panel provided in this embodiment, because all be provided with the link in the middle of both ends and the coil, can be nimble connect in order to form different connected mode to the different extreme points of coil, include the series connection and the parallelly connected of two coil sections promptly at least. By the mode, multiple connection modes can be realized under the condition that the structure of the coil is not changed, the circuit is convenient to change, space can be saved, and the portability of an electronic device is facilitated.

In the several embodiments provided in the present application, it should be understood that the disclosed method and apparatus may be implemented in other manners. For example, the above-described device embodiments are merely illustrative, and for example, the division of the modules or units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units may be integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The above description is only for the purpose of illustrating embodiments of the present application and is not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made according to the content of the present specification and the accompanying drawings, or which are directly or indirectly applied to other related technical fields, are also included in the scope of the present application.

Claims

1. A heating temperature measurement circuit, characterized in that, heating temperature measurement circuit includes:

a heating coil for heating the metal object when energized;

the device comprises an excitation coil and a receiving coil, wherein the excitation coil generates an alternating magnetic field when being electrified so as to enable the metal object to generate an electric eddy current, and the receiving coil generates a receiving signal under the action of the electric eddy current;

and the switching circuit is connected with the heating coil and used for electrifying the exciting coil and cutting off a conductive path of the heating coil when the temperature is measured.

2. The heating temperature measuring circuit according to claim 1,

3. The heating temperature measuring circuit according to claim 2,

4. The heating temperature measuring circuit according to claim 1,

5. The heating temperature measurement circuit according to claim 4,

6. The heating temperature measuring circuit according to any one of claims 1 to 5,

the heating coil and the exciting coil are two sections of the same coil.

7. The heating temperature measuring circuit according to claim 1,

the receiving coil includes a first differential coil and a second differential coil, one of the homonymous ends of the first differential coil and the second differential coil is connected, and the other of the homonymous ends of the first differential coil and the second differential coil generates the receiving signal, wherein the first differential coil or the second differential coil is coaxially disposed with the heating coil.

8. The heating temperature measuring circuit according to claim 1,

the driving frequency of the temperature measuring interval is 15KHz-60 KHz.

9. A temperature measuring circuit is characterized in that the temperature measuring circuit and a heating circuit are respectively and independently arranged and used for heating and measuring the temperature of a metal object, and the temperature measuring circuit comprises a sampling circuit, an exciting coil and a receiving coil which are connected in series;

the sampling circuit samples the excitation signal when being electrified;

the exciting coil generates an alternating magnetic field when being electrified, so that the metal object generates an eddy current;

the receiving coil generates a receiving signal under the action of the eddy current;

wherein the excitation signal and the received signal are used to determine a temperature of the metal object.

10. The heating temperature measuring circuit according to claim 9,

the receiving coil includes a first differential coil and a second differential coil, a pair of homonymous terminals of the first differential coil and the second differential coil are connected, and the other pair of homonymous terminals of the first differential coil and the second differential coil generates the receiving signal.

11. The heating temperature measuring circuit according to claim 9,

12. The heating temperature measuring circuit according to claim 9,

13. The heating temperature measuring circuit according to claim 9,

the temperature measuring circuit further comprises:

an excitation source;

a drive circuit, said sampling circuit, said drive coil and said receive coil being connected in series in a conductive path between said drive source and said drive circuit;

the driving circuit is controlled by a driving signal to realize conduction and closing.

14. A cooking device comprising a heating thermometry circuit according to any one of claims 1-8, or a thermometry circuit according to any one of claims 9-13.