Heating and temperature measuring circuit and cooking device

Abstract

The present application discloses a heating and temperature measuring circuit and a cooking device. The heating and temperature measuring circuit includes: an exciting coil for generating an alternating magnetic field when energized to cause eddy currents in a metal object; a first differential coil group for inducing eddy currents to generate a first electrical signal; a second differential coil group for inducing eddy currents to generate a second electrical signal; wherein the second differential coil group is different from the first differential coil group; a sampling coil for sampling a third electrical signal of the exciting coil; and a control circuit connected to the first differential coil group, the second differential coil group and the sampling coil for determining the temperature of the metal object according to the first electrical signal, the second electrical signal and the third electrical signal. By the above method, the accuracy of temperature measurement of the metal object is improved.

Description

Technical Field

[0001] The present application relates to the technical field of temperature detection, and particularly to a heating temperature measurement circuit and a cooking device. Background Art

[0002] Generally, when heating a metal object, it is necessary to detect and control the temperature of the metal object. Taking a cooking device as an example, in order to achieve good control of the cooking device and make the cooking device heat the metal object, it is necessary to measure the temperature of the metal object. For example, when heating the metal object with a set heating curve, it is necessary to detect whether the temperature of the metal object meets the set heating curve. For another example, when the temperature of the metal object is abnormal, the cooking device can be made to pause heating.

[0003] One existing method is to detect the temperature of the metal object through a thermistor. However, due to the problem of the position setting of the thermistor, the temperature detection is inaccurate. Summary of the Invention

[0004] To solve the above problems, the present application provides a heating temperature measurement circuit and a cooking device, which can improve the accuracy of temperature measurement of a metal object.

[0005] One technical solution adopted by the present application is: to provide a heating temperature measurement circuit, which includes: an excitation coil for generating an alternating magnetic field when energized to cause an eddy current in a metal object; a first differential coil group for inducing the eddy current to generate a first electrical signal; a second differential coil group for inducing the eddy current to generate a second electrical signal; wherein, the second differential coil group is different from the first differential coil group; a sampling coil for sampling a third electrical signal of the excitation coil; a control circuit connected to the first differential coil group, the second differential coil group and the sampling coil for determining the temperature of the metal object according to the first electrical signal, the second electrical signal and the third electrical signal.

[0006] Wherein, the first differential coil group includes: a first coil arranged corresponding to the excitation coil; a second coil, the same-name ends of the first coil and the second coil are connected, and the second coil is sleeved on the connection line of the excitation coil; the second differential coil group includes: a third coil arranged corresponding to the excitation coil; wherein, the electrical parameters of the third coil and the first coil are different; a fourth coil, the same-name ends of the third coil and the fourth coil are connected, and the fourth coil is sleeved on the connection line of the excitation coil.

[0007] Wherein, the excitation coil is arranged as a coil disc, and the first coil and the third coil are arranged corresponding to the center of the coil disc.

[0008] Wherein, the first coil and the excitation coil are coaxially arranged, and the third coil and the excitation coil are coaxially arranged.

[0009] Among them, the coil plane corresponding to the first coil and the coil plane corresponding to the second coil are located in the same plane, and the same plane is parallel to the coil plane corresponding to the excitation coil.

[0010] Among them, the second coil and the fourth coil are arranged in an area far from the metal object.

[0011] Among them, the sampling coil is sleeved on the connection line of the excitation coil.

[0012] Among them, the control circuit is used for: determining a first phase difference between the first electrical signal and the third electrical signal; correcting the first phase difference according to the difference between the first electrical signal and the second electrical signal to obtain a second phase difference; determining the temperature of the metal object according to the second phase difference.

[0013] Among them, the control circuit is used for: determining the ratio of the first electrical signal to the second electrical signal as a compensation value; determining the sum of the first phase difference and the compensation value as the second phase difference.

[0014] Another technical solution adopted in this application is: to provide a cooking device, and this cooking device includes the above-mentioned heating and temperature measuring circuit.

[0015] The heating and temperature measuring circuit provided in this application includes: an excitation coil, which is used to generate an alternating magnetic field when powered on to cause an eddy current in the metal object; a first differential coil group, which is used to sense the eddy current to generate a first electrical signal; a second differential coil group, which is used to sense the eddy current to generate a second electrical signal; among them, the second differential coil group is different from the first differential coil group; a sampling coil, which is used to sample a third electrical signal of the excitation coil; a control circuit, which is connected to the first differential coil group, the second differential coil group and the sampling coil, and is used to determine the temperature of the metal object according to the first electrical signal, the second electrical signal and the third electrical signal. In the above manner, the first differential coil group, the second differential coil group and the sampling coil are used to respectively collect corresponding electrical signals, and then the temperature of the metal object is determined according to the first electrical signal, the second electrical signal and the third electrical signal. Compared with the method of determining the temperature by using a group of differential coils and a sampling coil in the related art, in this embodiment, two groups of differential coils and a sampling coil are used to determine the temperature, which can solve the problem of large temperature deviation caused by a moving metal object, and further improve the accuracy of temperature measurement of the metal object. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings. Among them:

[0017] Figure 1It is a schematic structural diagram of an embodiment of the heating and temperature measurement circuit provided by the present application;

[0018] Figure 2 It is a schematic structural diagram of an embodiment of the exciting coil, the first coil, the third coil, and the metal object provided by the present application;

[0019] Figure 3 It is a schematic structural diagram of an embodiment of the exciting coil, the first coil, and the third coil provided by the present application;

[0020] Figure 4 It is an equivalent circuit diagram of the exciting coil, the first coil, the second coil, the third coil, the fourth coil, the sampling coil, and the metal object provided by the present application;

[0021] Figure 5 It is a schematic curve diagram of the phase difference when the third coil and the fourth coil are absent in the heating and temperature measurement circuit provided by the present application;

[0022] Figure 6 It is a schematic curve diagram of the compensation value in the heating and temperature measurement circuit provided by the present application;

[0023] Figure 7 It is a schematic curve diagram of the phase difference when the third coil and the fourth coil are present in the heating and temperature measurement circuit provided by the present application;

[0024] Figure 8 It is a schematic structural diagram of the first embodiment of the cooking device provided by the present application;

[0025] Figure 9 It is a schematic structural diagram of the second embodiment of the cooking device provided by the present application;

[0026] Figure 10 It is a schematic structural diagram of the third embodiment of the cooking device provided by the present application. Detailed implementation manners

[0027] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. It can be understood that the specific embodiments described herein are only used to explain the present application, rather than limiting the present application. Additionally, it should be noted that for the sake of description, only the parts related to the present application rather than all the structures are shown in the accompanying drawings. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0028] The terms "first", "second", etc. in this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally further include steps or units not listed, or may optionally further include other steps or units inherent to these processes, methods, products, or devices.

[0029] Referring to "embodiment" herein means that a specific feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of this application. The phrase appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.

[0030] The inventors have long-term research and found that in related non-contact temperature measurement, problems such as large temperature deviations will occur when there are moving metal objects. Based on this, the present application proposes the following solutions to solve the problem of large temperature deviation in the measurement of moving metal objects.

[0031] Referring to Figure 1 , Figure 1 is a schematic structural diagram of an embodiment of the heating and temperature measurement circuit provided by this application. The heating and temperature measurement circuit includes an excitation coil L1, a first differential coil group 11, a second differential coil group 12, a sampling coil L5, and a control circuit 13.

[0032] Among them, the excitation coil L1 is used to generate an alternating magnetic field when energized, so as to generate eddy currents in the metal object. In some embodiments, the metal object may be a metal cookware, and the metal cookware is coupled with the alternating magnetic field to generate eddy currents, and then generate heat.

[0033] Among them, the first differential coil group 11 is used to sense the eddy current to generate a first electrical signal.

[0034] Among them, some coils in the first differential coil group 11 may be arranged within the electromagnetic coupling range where the excitation coil L1 generates an alternating magnetic field when energized.

[0035] Among them, the second differential coil group 12 is used to sense the eddy current to generate a second electrical signal; among them, the second differential coil group 12 is different from the first differential coil group 11.

[0036] Among them, some coils in the second differential coil group 12 may be arranged within the electromagnetic coupling range where the excitation coil L1 generates an alternating magnetic field when energized.

[0037] Among them, the sampling coil L5 is used to sample the third electrical signal of the excitation coil L1.

[0038] Among them, the control circuit 13 is connected to the first differential coil group 11, the second differential coil group 12, and the sampling coil L5, and is used to determine the temperature of the metal object according to the first electrical signal, the second electrical signal, and the third electrical signal.

[0039] Specifically, the ratio between the first electrical signal and the second electrical signal can be used as a correction value to compensate the original calculation method, so as to determine the temperature of the metal object.

[0040] Among them, the excitation coil L1 is used to perform resonant heating on the metal object. Some coils in the first differential coil group 11 can have mutual inductance with the excitation coil L1 and the metal object respectively. The remaining coils in the first differential coil group 11 can have mutual inductance with the excitation coil L1. Some coils in the second differential coil group 12 can have mutual inductance with the excitation coil L1 and the metal object respectively. The remaining coils in the second differential coil group 12 can have mutual inductance with the excitation coil L1.

[0041] In some embodiments, the strength of the electromagnetic induction phenomenon between coils is not only related to the mutual inductance coefficient between them, but also related to their respective self-inductance coefficients, and depends on the tightness of the magnetic flux coupling between the two coils. For example, the tightness of the magnetic flux coupling between the two coils is represented by the coupling coefficient "k". Generally, the magnetic flux generated by one coil cannot all pass through the other coil, so generally the coupling coefficient k < 1. If the leakage magnetic flux is very small and can be ignored, k = 1. In addition, the mutual inductance coefficient M between the two coils is an inherent parameter of the coil, which depends on the number of turns, geometric dimensions, relative positions, and magnetic medium of the two coils. The value of M reflects the ability of one coil to generate magnetic flux in the other coil.

[0042] In this embodiment, the first differential coil group 11, the second differential coil group 12, and the sampling coil L5 are used to collect the corresponding electrical signals respectively, and then the temperature of the metal object is determined according to the first electrical signal, the second electrical signal, and the third electrical signal. Compared with the method of determining the temperature using a group of differential coils and the sampling coil L5 in the related art, in this embodiment, two groups of differential coils and the sampling coil L5 are used to determine the temperature, which can solve the problem of large temperature deviation caused by the movement of the metal object, and further improve the accuracy of temperature measurement of the metal object.

[0043] Further, continue to refer to Figure 1 for illustration:

[0044] The first differential coil group 11 includes: the first coil L2 and the second coil L3. The second differential coil group 12 includes: the third coil L4 and the fourth coil L6.

[0045] Among them, the first coil L2 is arranged corresponding to the excitation coil L1; for example, it is arranged within the electromagnetic coupling range of the excitation coil L1. The second coil L3 is sleeved on the connection line of the excitation coil L1. It can be understood that in addition to the loop-shaped area, the coil also includes the connection line. The loop-shaped area is used to generate an alternating magnetic field when energized, and the connection line is responsible for connecting the power supply to access the electrical signal.

[0046] Among them, the first end of the first coil L2 is connected to the first end of the second coil L3, and the second end of the first coil L2 and the second end of the second coil L3 are both connected to the control circuit 13. Among them, the first end of the first coil L2 and the first end of the second coil L3 are the same-named ends, that is, the same-named ends of the first coil L2 and the second coil L3 are connected, and the second coil L3 is sleeved on the connection line of the excitation coil L1.

[0047] It can be understood that the physical phenomenon that current-carrying coils are interconnected through each other's magnetic fields is called magnetic coupling. According to the winding directions of the two coils, the reference directions of the magnetic induction currents, and the relative positions of the two coils, the direction of the magnetic flux generated by the exciting current and the situation of mutual linking are determined according to the right-hand screw rule. If the directions of the first coil L2 and the second coil L3 are the same, then the starting ends of the windings of the two coils are the same-named ends, and the terminating ends of the windings of the two coils are also the same-named ends.

[0048] Since the same-named ends of the first coil L2 and the second coil L3 are connected, the mutual inductance between the second coil L3 and the excitation coil L1 can cancel the mutual inductance between the first coil L2 and the excitation coil L1, so that the first electrical signal received by the control circuit 13 is only the mutual inductance between the first coil L2 and the eddy current reflected by the metal object.

[0049] In some embodiments, the electrical parameters of the first coil L2 and the second coil L3 are the same. For example, each turn of the coil in the first coil L2 is thicker than each turn of the coil in the second coil L3, but the number of turns of the second coil L3 is more than the number of turns of the first coil L2.

[0050] It can be understood that in this way, under the condition that the electrical parameters are the same, the mutual inductances formed by the first coil L2 and the second coil L3 with the excitation coil L1 respectively are the same in value. Since the same-named ends of the first coil L2 and the second coil L3 are connected, they can cancel each other out.

[0051] Among them, the third coil L4 is arranged corresponding to the excitation coil L1; for example, it is arranged within the electromagnetic coupling range of the excitation coil L1. The fourth coil L6 is sleeved on the connection line of the excitation coil L1.

[0052] Among them, the first end of the third coil L4 is connected to the first end of the fourth coil L6, and the second end of the third coil L4 and the second end of the fourth coil L6 are both connected to the control circuit 13. Among them, the first ends of the third coil L4 and the fourth coil L6 are the same-named ends, that is, the same-named ends of the third coil L4 and the fourth coil L6 are connected, and the fourth coil L6 is sleeved on the connection line of the excitation coil L1.

[0053] Since the same-named ends of the third coil L4 and the fourth coil L6 are connected, the mutual inductance between the fourth coil L6 and the excitation coil L1 can cancel the mutual inductance between the third coil L4 and the excitation coil L1, so that the second electrical signal received by the control circuit 13 is only the mutual inductance between the third coil L4 and the eddy current reflected by the metal object.

[0054] In some embodiments, the electrical parameters of the third coil L4 and the fourth coil L6 are the same. For example, each turn of the coil in the third coil L4 is thicker than each turn of the coil in the fourth coil L6, but the number of turns of the coil in the third coil L4 is more than the number of turns of the coil in the fourth coil L6.

[0055] It can be understood that in this way, under the condition that the electrical parameters are the same, the mutual inductances formed by the third coil L4 and the fourth coil L6 and the excitation coil L1 respectively are the same in value. Since the same-named ends of the third coil L4 and the fourth coil L6 are connected, they can cancel each other out.

[0056] Among them, the electrical parameters of the third coil L4 and the first coil L2 are different. For example, the number of turns or windings of the coils of the third coil L4 and the first coil L2 are different, the wire diameters of the coils are different, or the materials of the coils are different.

[0057] In some embodiments, the connection line of the excitation coil L1 includes a first connection line and a second connection line. The first connection line is the input end, and the second connection line is the output end. The second coil L3 can be sleeved on the first connection line of the excitation coil L1, and the fourth coil L6 can be sleeved on the second connection line of the excitation coil L1.

[0058] The control circuit 13 collects the first electrical signal by connecting the first coil L2 and the second coil L3, and the control circuit 13 collects the second electrical signal by connecting the third coil L4 and the fourth coil L6. The control circuit 13 collects the second electrical signal by connecting the sampling coil L5. Then the control circuit 13 determines the temperature of the metal object according to the first electrical signal, the second electrical signal and the third electrical signal.

[0059] After the metal object moves, the electromagnetic coupling with the excitation coil L1 changes, and thus the mutual inductance with the first coil L2 and the third coil L4 changes. If the second electrical signal collected by the sampling coil L5 does not change, then the potential difference between the second electrical signal and the first electrical signal changes. Then, the second electrical signal and the third electrical signal are used for compensation to obtain the actual temperature of the moving metal object.

[0060] In this embodiment, using two sets of differential coils and the sampling coil L5 to determine the temperature can solve the problem of large temperature deviation caused by the moving metal object, and thus improve the accuracy of temperature measurement of the metal object.

[0061] In some embodiments, as Figure 2 shown, the excitation coil L1 is set as a coil disc, and the first coil L2 and the third coil L4 are arranged corresponding to the center of the coil disc. Among them, the first coil L2 and the excitation coil L1 are coaxially arranged, and the third coil L4 and the excitation coil L1 are coaxially arranged. Among them, the first coil L2 can be arranged above the third coil L4 or below the third coil L4. In other embodiments, the first coil L2 and the third coil L4 can be coaxially arranged on one side of the excitation coil L1, for example, arranged on the side of the excitation coil L1 close to the metal object or on the side of the excitation coil L1 far from the metal object.

[0062] In other embodiments, the first coil L2 and the third coil L4 can be respectively coaxially arranged on both sides of the excitation coil L1. For example, the first coil L2 is arranged on the side of the excitation coil L1 close to the metal object, and the third coil L4 is arranged on the side of the excitation coil L1 far from the metal object; or the third coil L4 is arranged on the side of the excitation coil L1 close to the metal object, and the first coil L2 is arranged on the side of the excitation coil L1 far from the metal object.

[0063] In other embodiments, the first coil L2 and the third coil L4 are in a three-dimensional spiral shape, the first coil L2 is sleeved on the third coil L4, and is coaxially arranged with the excitation coil L1. Or the third coil L4 is sleeved on the first coil L2, and is coaxially arranged with the excitation coil L1.

[0064] By arranging the first coil L2 and the third coil L4 corresponding to the center of the coil disc, when measuring the temperature, the first coil L2 and the third coil L4 can perform electromagnetic coupling with the metal object to obtain a relatively large mutual inductance, and thus can improve the accuracy of the measured temperature.

[0065] In some embodiments, as Figure 3As shown, the excitation coil L1 is set as a coil disk, and the first coil L2 and the third coil L4 are arranged corresponding to the center of the coil disk. Among them, the coil plane corresponding to the first coil L2 and the coil plane corresponding to the third coil L4 are in the same plane, and the same plane is parallel to the coil plane corresponding to the excitation coil L1. For example, the first coil L2 and the third coil L4 are arranged on the side of the excitation coil L1 close to the metal object, or the first coil L2 and the third coil L4 are arranged on the side of the excitation coil L1 far from the metal object. The coil plane corresponding to the first coil L2 and the coil plane corresponding to the third coil L4 are parallel to the coil plane corresponding to the excitation coil L1.

[0066] For example, the first coil L2 and the third coil L4 are symmetrically arranged along the center point of the excitation coil L1 within the electromagnetic coupling range of the excitation coil L1. The excitation coil L1 is in a planar spiral shape, its center point is O, its electromagnetic coupling range is A, and the distance from the center point of the first coil L2 to O is equal to the distance from the center point of the third coil L4 to O. The distance BO from the center point B of the first coil L2 to O is equal to the distance CO from the center point C of the third coil L4 to O. Among them, ∠BOC can be 180 degrees or any angle.

[0067] In some embodiments, the second coil L3 and the fourth coil L6 are arranged in the placement area far from the metal object, so that the second coil L3 and the fourth coil L6 have no mutual inductance with the metal object.

[0068] Since the second coil L3 and the fourth coil L6 have no mutual inductance with the metal object, the second coil L3 and the fourth coil L6 only have mutual inductance with the excitation coil L1, and the mutual inductance between the fourth coil L6 and the excitation coil L1 can cancel the mutual inductance between the third coil L4 and the excitation coil L1.

[0069] The same-named ends of the third coil L4 and the fourth coil L6 are connected, so that the mutual inductance between the fourth coil L6 and the excitation coil L1 can cancel the mutual inductance between the third coil L4 and the excitation coil L1, and the mutual inductance between the second coil L3 and the excitation coil L1 can cancel the mutual inductance between the first coil L2 and the excitation coil L1, so that the second electrical signal received by the control circuit 13 is only the mutual inductance of the eddy current reflected by the third coil L4 and the metal object, and the first electrical signal received by the control circuit 13 is only the mutual inductance of the eddy current reflected by the first coil L2 and the metal object.

[0070] Among them, the sampling coil L5 is sleeved on the connection line of the excitation coil L1.

[0071] Among them, the control circuit 13 is used for: determining the first phase difference between the first electrical signal and the third electrical signal; correcting the first phase difference according to the difference between the first electrical signal and the second electrical signal to obtain the second phase difference; and determining the temperature of the metal object according to the second phase difference.

[0072] Among them, the control circuit 13 is used to: determine the ratio of the first electrical signal to the second electrical signal as a compensation value; determine the sum of the first phase difference and the compensation value as the second phase difference.

[0073] Among them, the process of the control circuit 13 determining the temperature of the metal object can be expressed by the following formula:

[0074] T = K * (△φ + ε) + C.

[0075] Among them, T represents the measured temperature of the metal object, △φ represents the first phase difference, ε represents the compensation value, and K and C represent constants, where K and C are obtained by fitting in advance according to the relationship between the phase and the temperature.

[0076] In this embodiment, the ratio of the first electrical signal and the second electrical signal collected by the first differential coil group 11 and the second differential coil group 12 is used as the compensation value for temperature compensation to determine the temperature of the metal object. Compared with the method of using a set of differential coils and the sampling coil L5 to determine the temperature in the related art, this embodiment uses two sets of differential coils and the sampling coil L5 to determine the temperature, which can solve the problem of large temperature deviation caused by moving metal objects, and thus improve the accuracy of temperature measurement of metal objects.

[0077] In an application scenario, the sampling coil L5 has no mutual inductance with the metal object and can be set away from the placement area of the metal object. The electrical parameters of the sampling coil L5 can be the same as or different from those of the first coil L2.

[0078] Refer to Figure 4 , when the excitation coil L1 performs resonant heating, the resonant current i1 flows through the resonant circuit where the excitation coil L1 is located. The sampling coil L5 is wound around the magnetic conductor, and the resonant circuit of the excitation coil L1 passes through the magnetic conductor, so that it induces the resonant current i1 flowing through the excitation coil L1 and generates a corresponding resonant acquisition voltage u5. The measurement voltages output by the first coil L2 and the third coil L4 are labeled as u23. The measurement voltages output by the third coil L4 and the fourth coil L6 are labeled as u46.

[0079] Specifically, when the metal object is placed on the excitation coil L1, the excitation coil L1 has a mutual inductance with the inductance Lr of the metal object 30 to obtain a mutual inductance M1r, thereby generating a corresponding induced current ir, where the induced current ir flows through the inductance Lr and the equivalent thermal resistance Rz.

[0080] The first coil L2 has mutual inductances with the excitation coil L1 and the metal object respectively, and the second coil L3 has a mutual inductance with the excitation coil L1. Therefore, the inductance Lr of the metal object has a mutual inductance Mr2 with the first coil L2, but has no mutual inductance with the second coil L3; the excitation coil L1 has a mutual inductance M12 with the first coil L2, but has a mutual inductance M13 with the second coil L3.

[0081] The third coil L4 has mutual inductance with the excitation coil L1 and the metal object respectively, and the fourth coil L6 has mutual inductance with the excitation coil L1. Therefore, the induced inductance Lr of the metal object has mutual inductance Mr4 with the third coil L4, but does not have mutual inductance with the fourth coil L6; the excitation coil L1 has mutual inductance M14 with the third coil L4, but has mutual inductance M16 with the fourth coil L6.

[0082] The resonant current i1 can be measured by the sampling coil L5. Specifically, Uin is the mapped voltage of i1. Therefore, the resonant current i1 can be obtained through the resonant acquisition voltage u5 output by the sampling coil L5; u23 is the measurement voltage output by the first coil L2 and the second coil L3. Then, after the inductance values of the excitation coil L1, the first coil L2, the second coil L3, the sampling coil L5, and the inductance Lr are determined and their relative positions are determined, Mr2 can also be determined. Therefore, the electrical parameter LR of the metal object can be calculated, where the electrical parameter LR can be the magnetic permeability or the conductivity or the equivalent thermal resistance Rz. In some embodiments, the sampling coil L5 can be a current transformer of the excitation coil L1 to sample the resonant current flowing through the excitation coil L1 in the form of mutual inductance.

[0083] Since Lr is the induced inductance of the metal object 30, the temperature coefficient of the induced inductance Lr is small; while the equivalent thermal resistance Rz has a large temperature coefficient, and the temperature coefficients of most stainless steels or iron materials are between 0.001 and 0.007 (at 20 °C). Therefore, when u46, u23, u5, and i1 are measured, the thermal resistance Rz of the metal object can be deduced, and then the temperature of the metal object can be obtained according to the pre-established thermal resistance-temperature function T = f(Rz).

[0084] In an application scenario, the metal object is a metal cookware, the excitation coil L1 can be a coil disc, and the sampling coil L5 samples the current of the excitation coil L1; the first coil L2 and the third coil L4 sample the electrical signals of the metal cookware and the excitation coil L1 respectively, the second coil L3 and the fourth coil L6 are sleeved on the excitation coil L1 to sample the electrical signal of the excitation coil L1, and the like-named ends of the first coil L2 and the second coil L3 are connected together to form a pair of differential coils, obtaining the first differential coil group 11; the like-named ends of the third coil L4 and the fourth coil L6 are connected together to form another pair of differential coils, obtaining the second differential coil group 12.

[0085] The first differential coil group 11 and the second differential coil group 12 can eliminate the electrical signals of the excitation coil L1 on them and only retain the electrical signals (phase and amplitude) of the metal cookware on them. The phase difference is calculated between the electrical signal sampled by the sampling coil L5 and the electrical signal of the first differential coil group 11, that is, △φ = ΦL5 - ΦL2_L3. ΦL2_L3 represents the phase of the first differential coil group 11, that is, the phase of the first electrical signal, and ΦL5 represents the phase of the sampling coil L5, that is, the phase of the third electrical signal. Thus, the electrical parameters (permeability and conductivity) of the metal cookware can be indirectly obtained. The electrical parameters of the metal cookware change regularly with temperature. Therefore, a function between the temperature of the metal cookware and △φ can be established. However, when the metal cookware is at different positions of the excitation coil L1, although the electrical parameters of the cookware itself remain unchanged, the △φ measured by the sampling coil L5 and the first differential coil group 11 will change. Therefore, the electrical signal of the second differential coil group 12 is introduced for compensation. Specifically, ε = A(L2_L3) / A(L4_L6), where A(L2_L3) represents the amplitude of the first differential coil group 11, that is, the amplitude of the first electrical signal, and A(L4_L6) represents the amplitude of the second differential coil group 12, that is, the amplitude of the second electrical signal. ε represents the compensation value. Use ε to compensate for △φ.

[0086] The metal object 30 has a mutual inductance Mr2 with the first coil L2 and no mutual inductance with the second coil L3; the excitation coil L1 has a mutual inductance M13 with the second coil L3 and also has a mutual inductance M12 with the first coil L2. Let M13 = -M12. Therefore, the mutual inductance between the first coil L2 and the second coil L3 is only Mr2. The first electrical signal u23 is obtained by converting Mr2 into an electrical signal. At the same time, the sampling coil L5 also measures the third electrical signal u5 of the excitation coil L1. The phase difference △φ = ΦL5 - ΦL2_L3 is calculated for the two groups of signals u23 and u5; the amplitudes of the first coil L2 and the second coil L3 are obtained as A(L2_L3), and the amplitudes of the third coil L4 and the fourth coil L6 are obtained as A(L4_L6) in the same way. ε = A(L2_L3) / A(L4_L6) is introduced.

[0087] When the position of the metal cookware relative to the excitation coil L1 is fixed, the amplitudes A(L2_L3) and A(L4_L6) are fixed, that is, the coefficient ε is fixed. Then the temperature of the metal cookware can be expressed as T = K * △φ + C (K and C are constants obtained by fitting in advance according to the relationship between phase and temperature). When the position of the metal object 30 relative to the excitation coil L1 changes, △φ changes, and A(L2_L3) and A(L4_L6) also change asymmetrically because the first coil L2 and the third coil L4 are different, that is, the coefficient ε also changes accordingly. It can be understood that △φ changes with the position of the metal cookware. Thus, the formula T = K * (△φ + ε) + C can be obtained.

[0088] Combined with Figure 5 、Figure 6 and Figure 7 A comparison and explanation are as follows:

[0089] Figure 5 is the curve of △φ when no compensation is performed. As shown in Figure 5 shown, under a unified temperature difference (from 90°C to 30°C), the metal cookware has different △φ curves at different positions. And the farther the position is from the center, the smaller △φ is.

[0090] Refer to Figure 6 , the metal cookware has different ε curves at different positions, and the farther the position is from the center, the larger ε is.

[0091] Therefore, by using ε to compensate for △φ, under a unified temperature difference, the metal cookware has the same △φ curve at different positions, as shown in Figure 7 shown.

[0092] Thus, the problem of large temperature deviation caused by moving metal objects is solved, and further the accuracy of temperature measurement for metal objects is improved.

[0093] Refer to Figure 8 , Figure 8 is a schematic structural diagram of an embodiment of a cooking device provided by the present application. The cooking device 100 includes a heating and temperature measuring circuit 10.

[0094] The heating and temperature measuring circuit 10 can be the heating and temperature measuring circuit 10 in any of the above embodiments. Specifically, refer to any of the above embodiments, and details are not described here.

[0095] In other embodiments, refer to Figure 9 , the cooking device 100 includes a panel 20 and a heat and temperature measuring circuit 10.

[0096] Among them, the panel 20 includes a first side and a second side. The first side is a heating surface for placing a metal object 30, and the heating and temperature measuring circuit 10 is arranged on the second side. Optionally, the panel 20 is made of a non-metallic heat-resistant material.

[0097] Among them, the exciting coil L1 in the heating and temperature measuring circuit 10 generates an alternating magnetic field when energized, and an eddy current is generated in the metal object under the action of the alternating magnetic field, so as to realize the heating of the metal object 30 (cookware) by the exciting coil L1.

[0098] When measuring the temperature of the metal object 30, an excitation signal is provided to the excitation coil L1 to cause the excitation coil L1 to generate an alternating magnetic field. The metal object 30 generates eddy currents under the action of the alternating magnetic field, and the eddy currents further induce the first differential coil group 11 to generate a first electrical signal through electromagnetic induction; and the second differential coil group 12 induces eddy currents to generate a second electrical signal; the sampling coil L5 samples the third electrical signal of the excitation coil L1; the control circuit 13 determines the temperature of the metal object according to the first electrical signal, the second electrical signal and the third electrical signal.

[0099] Refer to Figure 10 , the cooking device 100 includes an excitation coil L1, a first coil L2, a second coil L3, a third coil L4, a fourth coil L6, a sampling coil L5, a control circuit 13 and an inverter circuit. Among them, the control circuit 13 includes a processor 131 and a signal processing circuit 132.

[0100] Among them, the signal processing circuit 132 is connected to the first coil L2, the second coil L3, the third coil L4, the fourth coil L6, the sampling coil L5 and the processor 131, and is used to receive the first electrical signal generated by the first coil L2 and the second coil L3 inducing eddy currents; and receive the second electrical signal generated by the third coil L4 and the fourth coil L6 inducing eddy currents; and receive the third electrical signal sampled by the sampling coil L5 of the excitation coil L1, and perform signal processing, and send the processed first electrical signal, second electrical signal and third electrical signal to the processor 131. Among them, the signal processing circuit 132 includes circuits such as operational amplifiers and filters. After processing the first electrical signal, the second electrical signal and the third electrical signal, they are input into the processor 131 to enable the processor 131 to complete temperature calculation. At the same time, the processor 131 also controls the operation of the inverter circuit.

[0101] The processor 131 is connected to the inverter circuit, and further controls the inverter circuit to invert the input voltage into an AC resonance signal through LC resonance, and then provide it to the excitation coil L1.

[0102] The DC power supply DC provides a DC temperature measurement voltage.

[0103] In summary, the heating and temperature measuring circuit of the present application includes: an excitation coil L1 for generating an alternating magnetic field when energized to cause eddy currents in a metal object; a first differential coil group 11 for inducing eddy currents to generate a first electrical signal; a second differential coil group 12 for inducing eddy currents to generate a second electrical signal; wherein, the second differential coil group 12 is different from the first differential coil group 11; a sampling coil L5 for sampling a third electrical signal of the excitation coil; a control circuit 13 connected to the first differential coil group, the second differential coil group 12 and the sampling coil L5 for determining the temperature of the metal object according to the first electrical signal, the second electrical signal and the third electrical signal. In the above manner, the first differential coil group, the second differential coil group 12 and the sampling coil L5 are used to collect corresponding electrical signals respectively, and then the temperature of the metal object is determined according to the first electrical signal, the second electrical signal and the third electrical signal. Compared with the method of using a group of differential coils and the sampling coil L5 to determine the temperature in the related art, in this embodiment, two groups of differential coils and the sampling coil L5 are used to determine the temperature, which can solve the problem of large temperature deviation caused by moving metal objects, and thus improve the accuracy of temperature measurement of metal objects.

[0104] In several embodiments provided by the present application, it should be understood that the disclosed methods and devices can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0105] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0106] In addition, the functional units in various embodiments of the present application can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated units can be implemented in the form of hardware or in the form of software functional units.

[0107] The above are only the embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made according to the description of the present application specification and the content of the drawings, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A heating and temperature measuring circuit, characterized in that, The heating and temperature measuring circuit includes: An exciting coil for generating an alternating magnetic field when energized to cause eddy currents in a metal object; A first differential coil group for inducing the eddy currents to generate a first electrical signal; A second differential coil group for inducing the eddy currents to generate a second electrical signal; wherein, the second differential coil group is different from the first differential coil group; A sampling coil for sampling a third electrical signal of the exciting coil; A control circuit connected to the first differential coil group, the second differential coil group and the sampling coil for determining the temperature of the metal object according to the first electrical signal, the second electrical signal and the third electrical signal.

2. The heating and temperature measuring circuit according to claim 1, characterized in that The first differential coil group includes: A first coil arranged corresponding to the exciting coil; A second coil, the same-name ends of the first coil and the second coil are connected, and the second coil is sleeved on the connecting wire of the exciting coil; The second differential coil group includes: A third coil arranged corresponding to the exciting coil; wherein, the electrical parameters of the third coil and the first coil are different; A fourth coil, the same-name ends of the third coil and the fourth coil are connected, and the fourth coil is sleeved on the connecting wire of the exciting coil.

3. The heating and temperature measuring circuit according to claim 2, characterized in that The exciting coil is arranged as a coil disc, and the first coil and the third coil are arranged corresponding to the center of the coil disc.

4. The heating and temperature measuring circuit according to claim 3, characterized in that The first coil and the exciting coil are coaxially arranged, and the third coil and the exciting coil are coaxially arranged.

5. The heating and temperature measuring circuit according to claim 3, characterized in that The coil plane corresponding to the first coil and the coil plane corresponding to the third coil are in the same plane, and the same plane is parallel to the coil plane corresponding to the exciting coil.

6. The heating and temperature measuring circuit according to claim 2, characterized in that The second coil and the fourth coil are arranged in a region far from the metal object.

7. The heating and temperature measuring circuit according to claim 1, characterized in that The sampling coil is sleeved on the connecting wire of the exciting coil.

8. The heating and temperature measuring circuit according to claim 1, characterized in that The control circuit is used for: Determining a first phase difference between the first electrical signal and the third electrical signal; Correcting the first phase difference according to the difference between the first electrical signal and the second electrical signal to obtain a second phase difference; Determining the temperature of the metal object according to the second phase difference.

9. The heating and temperature measuring circuit according to claim 8, characterized in that The control circuit is used for: Determining the ratio of the first electrical signal and the second electrical signal as a compensation value; Determining the sum of the first phase difference and the compensation value as the second phase difference.

10. A cooking device, characterized in that, The cooking device includes the heating and temperature measuring circuit according to any one of claims 1-9.

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