TW202326036A - Heating device and detecting method using the same - Google Patents

Abstract

A heating device is disclosed. The heating device comprises a resonant circuit, a detecting unit and a control unit. The resonant circuit comprises an inverting circuit, and a resonant tank. The inverting circuit provides resonant tank current and resonant tank voltage. The resonant tank comprises a heating coil, a resonant tank capacitor, a resonant tank equivalent inductor and a resonant tank equivalent impedance. The detecting unit detects the resonant tank current and the resonant tank voltage to obtain a reference current value, a first zero-crossing time point, a second zero-crossing time point, a time variation amount, a resonance period and a negative peak current value. The detecting unit calculates an inductance value of the resonance tank equivalent inductance according to a capacitance value of the resonance tank capacitor, the resonance period and a first calculation formula, and calculates an impedance value of the resonance tank equivalent impedance according to the resonance tank equivalent inductance, the time variation amount, the resonance period, the reference current value, the negative peak current value and a second calculation formula.

Description

Heating device and its applicable detection method

This case is a heating device, especially a heating device that utilizes the natural response characteristics of the resonant tank in the negative half-cycle discharge path, and calculates the equivalent inductance and impedance of the resonant tank based on the current and voltage information of the resonant tank and its application The detection method.

In recent years, with the advancement of science and technology, there is no longer a single choice of heating devices for people's cooking. In addition to heating devices using gas fuel, there are also microwave ovens driven by electric energy, infrared ovens, and electric heating furnaces. Choice, these various heating devices each have their own advantages and disadvantages, and can be respectively applied to the cooking and cooking occasions of various ingredients, so as to satisfy users with different needs.

A general heating device, such as an induction cooker, uses a heating coil to heat the food container, and then controls the amount of heating to the food container by adjusting the power supplied to the heating coil. When the heating device is heating, the position of the food container and the material of the food container not only affect the heating amount of the food container by the induction coil, but also affect the operation status and current value of the induction coil. Since the material of the food container of different materials or the position of the material of the food container will have different equivalent parameters induced by the equivalent inductance of the resonant tank, the conventional heating device will use the resonant tank voltage, resonant tank current and resonance The phase between the tank voltage and the resonant tank current is calculated by calculating the equivalent impedance of the resonant tank and the equivalent inductance of the resonant tank, and then using the operating results of the equivalent impedance of the resonant tank and the equivalent inductance of the resonant tank to adjust the electric energy on the heating coil. The method requires an additional voltage detection circuit and a current detection circuit, resulting in disadvantages of conventional heating devices such as complex wiring and high cost.

Therefore, how to develop a heating device that can improve the above-mentioned deficiencies in the prior art and an applicable detection method is an urgent problem that those in the relevant technical field need to solve at present.

This case is a heating device and its applicable detection method, wherein the heating device has a resonant tank, and the heating device uses the natural response characteristics of the resonant tank in the negative half cycle discharge path, and then uses the current and voltage information of the resonant tank to calculate the resonant tank Equivalent inductance and equivalent impedance of the resonant tank, so that the heating device does not need to install too many detection circuits, so the effect of simple circuit and low cost can be achieved.

In order to achieve the above-mentioned purpose, one of the preferred embodiments of this case is a heating device, comprising: a resonant circuit, including: an inverter circuit, providing a resonant tank current and a resonant tank voltage; and a resonant tank, including a heating coil, a resonant tank capacitor, The equivalent inductance of the resonance tank and the equivalent impedance of the resonance tank; the detection unit is electrically coupled to the resonance circuit, and detects the current and voltage of the resonance tank to obtain the reference current value, the first zero crossing time point, and the second zero crossing Over time point, time variation, resonance period and negative peak current value, the reference current value is the current value of the resonance tank current corresponding to the resonance tank voltage being zero, and the time variation is from the time point when the resonance tank voltage is zero to the first zero The time interval of the crossing time point, the resonance period is defined by the first zero crossing time point and the second zero crossing time point; and the control unit controls the inverter circuit to output the resonance tank current and the resonance tank voltage to heat the coil Heating power control; wherein, the detection unit calculates the inductance value of the equivalent inductance of the resonance tank according to the capacitance value of the resonance tank capacitance, the resonance period and the first calculation formula; the detection unit calculates the inductance value of the equivalent inductance of the resonance tank according to the equivalent inductance of the resonance tank, the time change The impedance value of the equivalent impedance of the resonance tank is calculated by the resonance period, the reference current value and the negative peak current value and the second calculation formula; the control unit performs heating according to the inductance value of the equivalent inductance of the resonance tank and the impedance value of the equivalent impedance Coil heating power control; where the first formula is , is the inductance value of the equivalent inductance of the resonant tank, is the capacitance value of the resonant tank capacitor, is the resonance period; the second formula is , is the impedance value of the equivalent impedance of the resonant tank, is the reference current value, is the amount of time change, is the negative peak current value.

In order to achieve the above-mentioned purpose, another preferred embodiment of this case is a detection method, which is applied to the detection unit of the heating device, wherein the heating device further includes a resonant circuit, and the resonant circuit includes an inverter circuit and a resonant tank. The circuit provides a resonant tank current and a resonant tank voltage. The resonant tank includes a heating coil, a resonant tank capacitor, a resonant tank equivalent inductance, and a resonant tank equivalent impedance. The detection method includes: (a) detecting the resonant tank current and the resonant tank voltage Obtain the reference current value, the first zero-crossing time point, the second zero-crossing time point, the time change, the resonance period and the negative peak current value, where the reference current value is the current corresponding to the resonance tank current whose voltage of the resonance tank is zero value, the amount of time change is the time interval from the time point when the resonance tank voltage is zero to the first zero crossing time point, and the resonance period is defined by the first zero crossing time point and the second zero crossing time point; (b) The inductance value of the equivalent inductance of the resonant tank is calculated according to the resonant tank capacitance, the resonant period and the first formula, wherein the first formula is , is the inductance value of the equivalent inductance of the resonant tank, is the capacitance value of the resonant tank capacitor, is the resonance period; (c) calculate the impedance value of the equivalent impedance according to the equivalent inductance of the resonance tank, the amount of time change, the resonance period, the reference current value and the negative peak current value and a second calculation formula, wherein the second calculation formula for , is the impedance value of the equivalent impedance of the resonant tank, is the reference current value, is the amount of time change, is a negative peak current value; and (d) control the heating power of the heating coil according to the inductance value of the equivalent inductance of the resonance tank and the impedance value of the equivalent impedance of the resonance tank.

Some typical embodiments embodying the features and advantages of the present application will be described in detail in the description in the following paragraphs. It should be understood that this case can have various changes in different aspects without departing from the scope of this case, and the descriptions and drawings therein are used as illustrations in nature rather than limiting this case.

Please refer to Figure 1A, Figure 1B and Figure 2, wherein Figure 1A is a schematic diagram of the system of the heating device in a preferred embodiment of this case, Figure 1B is a schematic diagram of the circuit structure of the heating device shown in Figure 1A, and Figure 2 The figure is a schematic diagram of the waveforms of the control voltage of the upper switching element of the heating device shown in Figure 1B and the current of the resonant tank. In this case, the heating device 1 can be but not limited to an induction cooker, and includes a power supply circuit 2 , a detection unit 3 and a control unit 4 . The power supply circuit 2 includes a resonant circuit 22 , and the resonant circuit 22 includes an inverter circuit 20 and a resonant tank 21 . The inverter circuit 20 receives the input voltage V _in and includes at least one switching element. For example, as shown in FIG. 1B , the inverter circuit 20 includes an upper switching element Q _h and a lower switching element Q _l , an upper switching element Q _h and a lower switching element Q _l is electrically connected in series, so that the inverter circuit 20 forms an inverter circuit in the form of a half bridge, and the upper switching element Q _h and the lower switching element Q _l are alternately switched on and off, and the inverter circuit 20 will input The voltage V _in is converted to output the resonant tank current I _r and the resonant tank voltage V _r . In addition, the upper switch element _Qh and the lower switch element _Ql respectively include a control terminal, a first current conduction terminal and a second current conduction terminal.

The resonance tank 21 includes a first terminal T ₁ , a second terminal T ₂ , a heating coil 210 , a resonance tank capacitance C _r , and a resonance tank equivalent inductance And the equivalent impedance _Req of the resonant tank. The first end _T1 and the second end _T2 are respectively electrically coupled to the two current conducting ends of one of the switching elements of the inverter circuit 20, for example, as shown in FIG. 1B, the first end T1 of the resonant tank 21 _is electrically Coupled to the first current conducting end of the lower switching element _Q1 , the second end _T2 of the resonant tank 21 is electrically coupled to the second current conducting end of the lower switching element _Q1 . Resonant tank capacitance C _r , equivalent inductance of resonant tank and the equivalent impedance R _eq of the resonant tank are electrically connected in series between the first end T ₁ and the second end T ₂ , and the capacitance C _r of the resonant tank and the equivalent inductance of the resonant tank The series connection order of the equivalent impedance R _eq of the resonant tank between the first terminal _T1 and the second terminal _T2 is not limited to that shown in FIG. 1B , and can be changed according to actual needs. The heating coil 210 can inductively heat a food container (not shown) placed on the heating device 1 according to the resonant tank current I _r and the resonant tank voltage V _r provided by the inverter circuit 20 . In addition, the resonant tank 21, the heating coil 210 and the food container equivalently form the equivalent inductance of the resonant tank on the circuit. , and the resonant tank 21 , the heating coil 210 and the food container also equivalently constitute the equivalent impedance _Req of the resonant tank on the circuit. In addition, the capacitance value of the capacitor C _r of the resonant tank is a known value.

It can be seen from the above that the equivalent inductance of the resonant tank There is a corresponding relationship between the inductance value of the heating coil 210, the material of the food container and the position of the food container on the heating device 1. In other words, the inductance of the heating coil 210, the material of the food container, and the food container are heated Any change in the position of the device 1 will make the equivalent inductance of the resonant tank The inductance value changes. The impedance value of the equivalent impedance R _eq of the resonant tank has a corresponding relationship with the impedance value of the resonant tank 21, the material of the food container and the position of the food container on the heating device 1, that is, the impedance value of the resonant circuit 1, the material of the food container And any change of the position of the food container on the heating device 1 will cause the impedance value of the equivalent impedance R _eq of the resonance tank to change.

The control unit 4 is electrically coupled with the inverter circuit 20 for controlling the inverter circuit 20 to output the resonant tank current I _r and the resonant tank voltage V _r to control the heating power of the heating coil 210 .

The detection unit 3 is electrically coupled to the resonant circuit 22, for example, electrically coupled between the first terminal T1 of the resonant tank ₂₁ and the capacitor C _r of the resonant tank, and detects the resonant tank current I _r and the resonant tank voltage V _r , To obtain the reference current value I ₀ , the time variation Δt, the first zero-crossing time point, the second zero-crossing time point, the resonance period T and the negative peak current value . The reference current value _I0 is the current value of the resonance tank current _Ir corresponding to the resonance tank voltage _Vr being zero. For example, the switching element _Qh on the inverter circuit 20 is in a negative half cycle and switched from conduction to shutdown, so that the resonance When the tank voltage V _r is zero, the instantaneous current value of the resonant tank current I _r constitutes the reference current value I ₀ (as illustrated in Figure 2 at time t=0). The first zero-crossing time point is the time point when the resonant tank current I _r is zero for the first time after the resonant tank voltage V _r is zero (time t1 as exemplified in FIG. 2 ). The second zero-crossing time point is the time point when the resonant tank current I _r is zero for the second time after the resonant tank voltage V _r is zero (such as the time t3 illustrated in FIG. 2 ). The time variation Δt is the time interval from the time point when the resonant tank voltage V _r is zero to the first zero-crossing time point (for example, the time length from time t0 to time t1 shown in FIG. 2 ). The resonance period T is defined by the first zero-crossing time point and the second zero-crossing time point. Negative peak current value It is the maximum value of the resonant tank current I _r in the case of negative current (for example, occurs at time t2 shown in Figure 2).

In addition, in this case, the detection unit 3 calculates the equivalent inductance of the resonance tank according to the capacitance value of the resonance tank capacitance _Cr , the resonance period T and the first calculation formula The inductance value, the first calculation formula is as follows: ---(1); Among them, L _eq is the equivalent inductance of the resonance tank The inductance value, C _r is the capacitance value of the resonance tank capacitor C _r , and T is the resonance period.

What's more, the detection unit 3 is also based on the inductance value of the resonance tank equivalent inductance L _eq , the time variation Δt, the resonance period T, the reference current value I ₀ , and the negative peak current value Calculate the impedance value of the equivalent resonance tank equivalent impedance R _eq with the second calculation formula, wherein the second calculation formula is as follows: ---(2); where is the impedance value of the equivalent impedance R _eq of the resonance tank, is the reference current value, is the amount of time change, is the negative peak current value.

Please refer to Figure 3, Figure 4 and Figure 5, and cooperate with Figure 1A, Figure 1B and Figure 2, where Figure 3 is the zero crossing of the parameter acquisition unit of the detection unit shown in Figure 1B Schematic diagram of the circuit structure of the detection circuit. Figure 4 is a schematic diagram of the waveform of the pulse width signal output by the zero-crossing detection circuit shown in Figure 3 under the structure of Figure 2, and Figure 5 is Figure 1B The schematic diagram of the circuit structure of the negative peak detection circuit of the parameter acquisition unit of the detection unit is shown. The detection unit 3 further includes a parameter acquisition unit 30 and a microprocessor 31 . The parameter acquisition unit 30 is electrically coupled to the resonant circuit 22, for example, electrically coupled between the first terminal T1 of the resonant tank ₂₁ and the capacitor C _r of the resonant tank, and detects the resonant tank current I _r and the resonant tank voltage V _r , And when the resonant tank voltage V _r is zero because the inverter circuit 20 is in the negative half cycle, for example, when the switching element Q _h on the inverter circuit 20 is in the negative half cycle and switches from conduction to off and is zero, according to the resonance The tank current I _r and the resonant tank voltage V _r obtain the negative peak current value of the resonant period T and the resonant tank current I _r of the resonant tank 21 Parameter information for .

In this case, the parameter acquisition unit 30 can be implemented by circuit hardware or software, wherein when the parameter acquisition unit 30 is implemented by circuit hardware, as shown in Figure 1B, the parameter acquisition unit 30 includes a zero-crossing detection circuit 300 and Negative peak detection circuit 301. The zero-cross detection circuit 300 is electrically coupled to the resonant tank 21, for example, electrically coupled between the first terminal _T1 and the capacitor C _r of the resonant tank, and detects the resonant tank current I _r and the resonant tank voltage V _r for The parameter information of the resonance period T obtained according to the resonance tank current I _r and the resonance tank voltage V _r , wherein the zero-crossing detection circuit 300 includes a first current comparator CT ₁ , a first resistor R ₁ , a comparator COM, and a second resistor R ₂ , the first capacitor C ₁ and the Zener diode D _z . The input terminal of the first current comparator CT ₁ is electrically coupled to the resonant tank 21 , for example, electrically coupled between the first terminal T ₁ and the resonant tank capacitor C _r to receive the resonant tank current I _r . The first terminal and the second terminal of the first resistor _R1 are respectively electrically coupled to the output terminal of the first current comparator _CT1 , and the second terminal of the first resistor _R1 is further electrically coupled to the ground terminal G. The positive input terminal of the comparator COM is electrically coupled to the first terminal of the first resistor _R1 and the output terminal of the first current comparator _CT1 , and the negative input terminal of the comparator COM is connected to the second terminal of the first resistor _R1 and The ground terminal G is electrically coupled. The second resistor _R2 is electrically coupled between the voltage source _V1 and the output terminal of the comparator COM. The anode of the Zener diode D _z is electrically coupled to the ground terminal G, and the cathode of the Zener diode D _z is electrically coupled to the output end of the comparator COM. The first capacitor _C1 is electrically coupled between the output terminal of the comparator COM and the ground terminal G, and is electrically coupled in parallel with the Zener diode _Dz . By the hardware structure of the _above -mentioned zero-crossing detection circuit 300, the comparator COM can output a pulse width signal at the output terminal, wherein the pulse width The signal corresponds to the level switching between the high level and the low level at the zero crossing point of the resonant tank current _Ir . In addition, when the upper switching element _Qh is switched from on to off and the resonant tank voltage _Vr is After zero, the time from the first level switching (corresponding to the first zero crossing time point) of the pulse width signal output by the comparator COM to the second level switching (corresponding to the second zero crossing time point) The length is actually equal to 1/2 of the resonance period T, and the resonance period T can be obtained by multiplying 1/2 of the resonance period T twice, so the resonance period T is actually defined by the resonance tank current I _r and the resonance tank voltage V _r , and the zero-crossing detection circuit 300 obtains information about the resonant period T according to the resonant tank current I _r and the resonant tank voltage V _r .

The negative peak detection circuit 301 is electrically coupled to the resonant tank 21, for example, electrically coupled between the first terminal _T1 and the capacitor C _r of the resonant tank, and detects the resonant tank current I _r and the resonant tank voltage V _r , for use in accordance with The resonant tank current I _r takes on the negative peak current value with respect to the resonant tank current I _r parameter information, wherein the negative peak detection circuit 301 includes a second current comparator CT ₂ , a third resistor R ₃ , a fourth resistor R ₄ , a negative feedback amplifier C _amp , a diode D and a second capacitor C ₂ . The input terminal of the second current comparator CT ₂ is electrically coupled to the resonant tank 21 , for example, electrically coupled between the first terminal T ₁ and the resonant tank capacitor C _r to receive the resonant tank current I _r . The first terminal and the second terminal of the third resistor _R3 are respectively electrically coupled to the output terminal of the second current comparator _CT2 , and the second terminal of the third resistor _R3 is further electrically coupled to the ground terminal G. The non-inverting input terminal of the negative feedback amplifier C _amp is electrically coupled to the first terminal of the third resistor R ₃ and the output terminal of the second current comparator CT ₂ , and the inverting input terminal of the negative feedback amplifier C _amp is connected to the negative The output end of the feedback amplifier C _amp is electrically coupled. The cathode of the diode D is electrically coupled to the output end of the negative feedback amplifier C _amp . The fourth resistor _R4 is electrically coupled between the anode of the diode D and the ground terminal G. The second capacitor _C2 is electrically coupled between the anode of the diode D and the ground terminal G, and is electrically coupled in parallel with the fourth resistor _R4 . With the above-mentioned circuit structure of the negative peak detection circuit 301, the negative peak detection circuit 301 can obtain the negative peak current value of _the resonant tank current _Ir according to the resonant tank current _Ir and the resonant tank voltage Vr information.

When the parameter acquisition unit 30 is implemented by software, then the algorithm, calculation formula and/or parameter relationship table, etc. can be preset in the parameter acquisition unit 30, so as to cooperate with the preset through the resonance tank current I _r and the resonance tank voltage V _r Algorithms, calculation formulas and/or parameter relationships, etc. to obtain the negative peak current value of the resonant period T and the resonant tank current I _r Parameter information for .

The microprocessor 31 may be composed of a digital signal processor (Digital Signal Processor; DSP) or a microcontroller (microcontroller unit; MCU), and is electrically coupled with the parameter acquisition unit 30, and includes a first calculation unit 310 and a second calculation unit 311. The first calculation unit 310 is preset with a first calculation formula, and receives parameter information about the resonance period T from the parameter acquisition unit 30, and the first calculation unit 310 is based on the capacitance value of the resonance tank capacitor Cr, the first calculation formula and the received Calculate the equivalent inductance of the resonant tank from the resonant period T The inductance value, and output about the equivalent inductance of the resonant tank The first calculation result of the inductance value

The second calculation unit 311 is preset with a second calculation formula, and receives the equivalent inductance of the resonant tank from the first calculation unit 310 The first calculation result of the inductance value, and obtain the reference current value I ₀ , the time variation Δt and the negative peak current value of the resonance tank current I _r according to the resonance tank current I _r and the resonance tank voltage V _r , and according to the equivalent inductance of the resonant tank Inductance value, reference current value I ₀ , time variation Δt, negative peak current value of resonant tank current I _r and the second calculation formula calculates the impedance value of the equivalent impedance _Req of the resonance tank to output a second calculation result about the impedance value of the equivalent impedance _Req of the resonance tank.

In some embodiments, the control unit 4 of the heating device 1 can further obtain the equivalent inductance of the resonant tank according to the first calculation result and the second calculation result output by the microprocessor 31 and the equivalent resistance of the resonant tank R _eq , and then according to the equivalent inductance of the resonant tank and the equivalent resistance R _eq of the resonance tank carry out various controls on the resonance circuit 22, for example, the control unit 4 can be based on the equivalent inductance of the resonance tank and the parameter value of the equivalent resistance R _eq of the resonance tank to determine whether the heating coil 210 is started or closed and whether the food container is still on the heating device 1, and the control unit 4 can be based on the equivalent inductance of the resonance tank and the parameter value of the equivalent resistance R _eq of the resonance tank to determine the burden ratio of the heating power of the heating coil 210, the control unit 4 can also be based on the change of the parameter value of the equivalent inductance L _eq of the resonance tank and the equivalent resistance R _eq of the resonance tank. The output power of the heating device 1 is corrected, and the control unit 4 can judge the material of the food container according to the parameter values of the equivalent inductance L _eq of the resonance tank and the equivalent resistance R _eq of the resonance tank.

The above-mentioned first calculation formula (1) and second calculation formula (2) will be roughly deduced below, please refer to FIG. 1A to FIG. 3 . First of all, the main working principle of this case is based on the natural response characteristics of the resonance tank 21. When the time t≧0, the resonance tank 21 enters into a natural response, so the general formula of the resonance tank current _Ir can be expressed as: ---(3); where is the time function of the resonant tank current _Ir , is the attenuation coefficient, is the damped resonance frequency, and are arbitrary constants, determined by the boundary conditions. Because heating device 1 is the application of induction cooker, so , so that the resonant tank 21 operates in the underdamped region (underdamped), and can simplify ,in is the natural resonant frequency. Through the sum angle formula and rearranging formula (3), we can get: ---(4); where is the current peak value of the resonant tank 21 at natural resonance, is the angle.

In addition, in formula (4), some parameters have the following general formula: ---(5); ---(6); Therefore, formula (1) can be deduced from formula (5), and the resonant frequency The relationship between W and the resonance period T is as follows: ---(7);

Since the discharge waveform of the resonant tank 21 in the negative half cycle is relatively complete when the duty cycle of the upper switching element Q _h is relatively small, the zero-crossing detection circuit 300 can be used to obtain half of the resonant cycle T/2 at this time, so that the first The calculation unit 310 brings half of the resonant period T/2 into the formula (1) according to the formula (7), so as to obtain the inductance value of the equivalent inductance L _eq of the resonant tank.

Additionally, due to the and When the current I _r of the resonance tank is always zero, so in this case, the zero-crossing point of the current I _r of the resonance tank is used as a reference point, and the calculation is performed in the form of a relative angle. As shown in Figure 2, when the upper switching element Q _h is switched from on to off and becomes zero, the instantaneous current value of the resonant tank current I _r constitutes the reference current value I ₀ , so it is assumed that the upper switching element Q _h is off and The conduction moment of the lower switching element _Ql occurs at t=t0, and assuming that the upper switching element _Qh switches from conduction to off and becomes zero, the resonant tank current _Ir passes through the zero-crossing point for the first time (the first zero-crossing time point) occurs at an angle of π, and assumes a negative peak current value of the resonant tank current I _r Occurs when t=t2 (usually occurs at t=3π/2), then t=0 and t=t2 can be obtained through formula (4) to obtain the following formulas respectively: ---(8); ---(9); It can be seen from Figure 3 that after the upper switch element Q _h is switched from on to off and the time point of the first zero-crossing point of the resonant tank current I _r can be obtained by subtracting the time change Δt The sampling time point of the reference current value I ₀ , and the negative peak current value of the resonant tank current I _r Occurs when t=3π/2, so the following formula can be obtained: ---(10); ---(11); ---(12);

Finally, after dividing formula (8) by formula (9) and matching formulas (10)~(12), formula (2) can be deduced.

In some embodiments, the detection unit 3 may be, but not limited to, constituted by a controller.

In some embodiments, the inverter circuit 20 is not limited to include the upper switching element Q _h and the lower switching element Q _l as shown in FIG. 1B , in other embodiments, the inverter circuit 20 may also include a single switching element or More than four switch elements, wherein when the inverter circuit 20 includes a single switch element, the first end _T1 and the second end _T2 of the resonant tank 21 are respectively connected to the first current conduction end and the second current conduction end of the single switch element Electrically coupled, when the inverter circuit 20 includes, for example, four switching elements and is a full-bridge inverter circuit, the first end _T1 and the second end _T2 of the resonant tank 21 are respectively connected to the lower switching element in any bridge arm The first current conduction end and the second current conduction end are electrically coupled. In addition, in the embodiment where the inverter circuit 20 includes a single switch element or more than four switch elements, the operation of the heating device 1 in this application is similar to the above-mentioned content, so it is not repeated here.

Please refer to Figure 6, which is a schematic flow chart of the steps of the detection method in a preferred embodiment of the present case. The detection method of this embodiment can be applied to the detection unit 3 of the heating device 1 shown in FIG. 1B, and includes the following steps.

Step S1, the detection unit 3 obtains the reference current value I ₀ , the time variation Δt, the first zero-crossing time point, and the second zero-crossing time point according to the resonant tank current _Ir and the resonant tank voltage _Vr of the resonant tank 21 , resonance period T and negative peak current value .

Step S2, the detection unit 3 calculates the equivalent inductance of the resonance tank according to the capacitance value of the resonance tank capacitor Cr, the resonance period T, and the first calculation formula inductance value.

Step S3, the detection unit 3 is based on the inductance value of the resonance tank equivalent inductance L _eq , the time variation Δt, the resonance period T, the reference current value I ₀ , and the negative peak current value The impedance value of the equivalent impedance R _eq of the resonance tank is calculated by using the second calculation formula.

Step S4 , the control unit 4 controls the heating power of the heating coil 210 according to the inductance value of the resonance tank equivalent inductance _Leq and the resistance value of the resonance tank equivalent impedance _Req .

In some embodiments, in step S4, it may further include determining whether a food container is placed on the heating device 1 according to the equivalent inductance L _eq of the resonance tank and the equivalent resistance R _eq of the resonance tank. In step S4, it may further include determining the heating power burden ratio of the heating coil 1 according to the equivalent inductance L _eq of the resonance tank and the equivalent resistance R _eq of the resonance tank. What's more, in step S4, it may further include judging the material of the food container on the heating device 1 according to the equivalent inductance L _eq of the resonance tank and the equivalent resistance R _eq of the resonance tank.

In summary, this case is a heating device and its applicable detection method. The heating device has a resonant tank, and based on the natural response characteristics of the resonant tank in the negative half-cycle discharge path, the heating device in this case uses the current of the resonant tank information and cooperate with the aforementioned first formula (1) and second formula (2) to calculate the inductance value of the equivalent inductance of the resonance tank and the inductance value of the equivalent impedance of the resonance tank, so compared with the traditional heating device, the The heating device only needs to be equipped with fewer detection circuits, thereby achieving the effect of simple circuit and low cost.

1: heating device 2: power supply circuit 3: detection unit 4: control unit 20: inverter circuit 21: resonance tank 22: resonance circuit V _in : input voltage Q _h : upper switching element Q _l : lower switching element T ₁ : first terminal T ₂ : second terminal C _r : resonant tank capacitance : Resonance tank equivalent inductance R _eq : Resonance tank equivalent impedance I _r : Resonance tank current I ₀ : Reference current value Δt: Time variation V _r : Resonance tank voltage I _N : Negative peak current value 30: Parameter acquisition unit 31 : microprocessor 300: zero crossing detection circuit 301: negative peak detection circuit CT ₁ : first current comparator R ₁ : first resistor COM: comparator R ₂ : second resistor C ₁ : first capacitor D _z : Zener diode G: ground terminal CT ₂ : second current comparator R ₃ : third resistor R ₄ : fourth resistor C _amp : negative feedback amplifier D: diode C ₂ : second capacitor 310: first One calculation unit 311: second calculation unit t0, t1, t2, t3: time T: resonance period 210: heating coil

Fig. 1A is a system schematic diagram of the heating device of the preferred embodiment of the present case; Fig. 1B is a schematic diagram of the circuit structure of the heating device shown in Fig. 1A; Fig. 2 is a schematic diagram of the waveforms of the control voltage of the upper switching element of the heating device shown in Fig. 1B and the resonance tank current; Fig. 3 is a schematic diagram of the circuit structure of the zero-cross detection circuit of the parameter acquisition unit of the detection unit shown in Fig. 1B; Figure 4 is a schematic diagram of the waveform of the pulse width signal output by the zero-crossing detection circuit shown in Figure 3 under the framework of Figure 2; Fig. 5 is a schematic circuit structure diagram of the negative peak detection circuit of the parameter acquisition unit of the detection unit shown in Fig. 1B; Fig. 6 is a schematic flow chart of the steps of the detection method of the preferred embodiment of the present case.

1: Heating device

2: Power supply circuit

3: Detection unit

4: Control unit

20: Inverter circuit

21: Resonance tank

22: Resonant circuit

V _in : input voltage

Q _h : Upper switching element

Q _l : Lower switching element

T ₁ : first end

T ₂ : the second terminal

C _r : capacitance of resonant tank

L _eq : Equivalent inductance of resonant tank

R _eq : Equivalent impedance of resonance tank

I _r : resonant tank current

I ₀ : Reference current value

△t: time change

V _r : Resonant tank voltage

30: Parameter acquisition unit

31: Microprocessor

300: Zero crossing detection circuit

301: Negative peak detection circuit

310: The first computing unit

311: Second computing unit

Claims (13)

A heating device, comprising: a resonant circuit, including: an inverter circuit, providing a resonant tank current and a resonant tank voltage; and a resonant tank, including a heating coil, a resonant tank capacitor, a resonant tank equivalent inductance and A resonance tank equivalent impedance; a detection unit, electrically coupled to the resonance circuit, and detecting the resonance tank current and the resonance tank voltage to obtain a reference current value, a first zero-crossing time point, a second Zero crossing time point, a time variation, a resonance period and a negative peak current value, the reference current value is the current value corresponding to the resonance tank current whose voltage of the resonance tank is zero, and the time variation is the resonance tank current value the time distance from the time point when the voltage is zero to the first zero-crossing time point, the resonance period is defined by the first zero-crossing time point and the second zero-crossing time point; and a control unit that controls the The inverter circuit outputs the resonance tank current and the resonance tank voltage to control the heating power of the heating coil; wherein, the detection unit calculates according to the capacitance value of the resonance tank capacitor, the resonance period and a first calculation formula The inductance value of the equivalent inductance of the resonance tank; the detection unit calculates based on the equivalent inductance of the resonance tank, the time variation, the resonance period, the reference current value and the negative peak current value and a second calculation formula The impedance value of the equivalent impedance of the resonance tank; the control unit controls the heating power of the heating coil according to the inductance value of the equivalent inductance of the resonance tank and the impedance value of the equivalent impedance of the resonance tank; wherein the first calculation formula for , is the inductance value of the equivalent inductance of the resonant tank, is the capacitance value of the resonant tank capacitor, is the resonance period; the second formula is , is the impedance value of the equivalent impedance of the resonant tank, For this reference current value, For the time variation, is the negative peak current value. The heating device as described in claim 1, wherein the detection unit includes a parameter acquisition unit, which is electrically coupled to the resonance tank and detects the current of the resonance tank and the voltage of the resonance tank, and when the voltage of the resonance tank is zero and obtaining the negative peak current value with respect to the resonant cycle and the resonant tank current according to the resonant tank current and the resonant tank voltage. The heating device as described in claim 2, wherein the parameter acquisition unit includes: a zero-cross detection circuit electrically coupled to the resonance tank, and detecting the resonance tank current and the resonance tank voltage, and obtaining the resonance period according to the resonance tank current and the resonance tank voltage; and A negative peak detection circuit is electrically coupled with the resonant tank, and detects the resonant tank current and the resonant tank voltage, and obtains the negative peak current value according to the resonant tank current and the resonant tank voltage. The heating device as described in claim 3, wherein the zero-crossing detection circuit includes: a first current comparator, an input end of the first current comparator is electrically coupled to the resonant tank to receive current from the resonant tank; A first resistor, a first end and a second end of the first resistor are respectively electrically coupled to an output end of the first current comparator, and the second end of the first resistor is further connected to a ground end electrical coupling; A comparator, a positive input terminal of the comparator is electrically coupled to the first terminal of the first resistor and the output terminal of the first current comparator, a negative input terminal of the comparator is electrically coupled to the first resistor The second terminal of and the ground terminal are electrically coupled; a second resistor electrically coupled between a voltage source and an output terminal of the comparator; a zener diode, an anode of the zener diode is electrically coupled to the ground terminal, a cathode of the zener diode is electrically coupled to the output terminal of the comparator; and A first capacitor is electrically coupled between the output terminal of the comparator and the ground terminal, and is electrically coupled in parallel with the Zener diode. The heating device as described in claim 3, wherein the negative peak detection circuit includes: a second current comparator, an input end of the second current comparator is electrically coupled to the resonant tank to receive current from the resonant tank; A third resistance, a first end and a second end of the third resistance are respectively electrically coupled to an output end of the second current comparator, and the second end of the third resistance is further connected to a ground end electrical coupling; A negative feedback amplifier, a non-inverting input terminal of the negative feedback amplifier is electrically coupled with a first terminal of the third resistor and the output terminal of the second current comparator, a negative feedback amplifier The inverting input terminal is electrically coupled to an output terminal of the negative feedback amplifier; a diode, one cathode of the diode is electrically coupled to an output end of the negative feedback amplifier; A fourth resistor electrically coupled between an anode of the diode and the ground terminal; A second capacitor, the second capacitor is electrically coupled between the anode of the diode and the ground terminal, and is electrically coupled in parallel with the fourth resistor. The heating device as described in claim 4, wherein the detection unit also includes a microprocessor, and the microprocessor includes: A first calculation unit, preset the first calculation formula, and calculate the equivalent inductance of the resonance tank according to the capacitance value of the resonance tank capacitance, the resonance period provided by the zero-crossing detection circuit and the first calculation formula the inductance value, and output a first calculation result to the control unit; and A second calculation unit, preset the second calculation formula, receive the first calculation result provided by the first calculation unit, and obtain the reference current value and the time variation according to the resonance tank current and the vibration tank voltage And the negative peak current value of the resonant tank current is further based on the inductance value of the equivalent inductance of the resonant tank, the reference current value, the time variation, the negative peak current value of the resonant tank current and the second calculation formula Calculate the impedance value of the equivalent impedance of the resonance tank, and output a second calculation result to the control unit. The heating device as described in claim 6, wherein the microprocessor is constituted by a digital signal processor or a microcontroller. The heating device as claimed in claim 1, wherein the heating device is an induction cooker. The heating device as described in claim 1, wherein the inverter circuit includes an upper switching element and a lower switching element electrically connected in series, the upper switching element and the lower switching element are alternately switched on and off, and the The resonant slot includes a first end and a second end, and the first end and the second end are respectively electrically coupled to the two current conducting ends of the lower switching element. A detection method applied in a detection unit of a heating device, wherein the heating device further includes a resonant circuit, the resonant circuit includes an inverter circuit and a resonant tank, the inverter circuit provides a resonant tank current and A resonance tank voltage, the resonance tank includes a heating coil, a resonance tank capacitance, a resonance tank equivalent inductance and a resonance tank equivalent impedance, the detection method includes: (a) detecting the resonance tank current and the A reference current value, a first zero-crossing time point, a second zero-crossing time point, a time variation, a resonance period and a negative peak current value are obtained by using the resonance tank voltage, wherein the reference current value is for The current value of the resonant tank current should the resonant tank voltage be zero, the time variation is the time interval from the time point when the resonant tank voltage is zero to the first zero crossing time point, and the resonance period is the first zero crossing time point. defined by the crossing time point and the second zero crossing time point; (b) calculate the inductance value of the equivalent inductance of the resonance tank according to the resonance tank capacitance, the resonance period and a first calculation formula, wherein the first One expression is , is the inductance value of the equivalent inductance of the resonant tank, is the capacitance value of the resonant tank capacitor, (c) Calculate the impedance of the equivalent impedance according to the equivalent inductance of the resonance tank, the time variation, the resonance period, the reference current value, the negative peak current value and a second calculation formula value, where the second expression is , is the impedance value of the equivalent impedance of the resonant tank, For this reference current value, For the time variation, is the negative peak current value; and (d) controlling the heating power of the heating coil according to the inductance value of the equivalent inductance of the resonance tank and the impedance value of the equivalent impedance of the resonance tank. The detection method as described in claim 10, wherein the heating device is an induction cooker; and in the step (d), further comprising judging whether the heating device is Place a food container. The detection method as described in claim 10, wherein the heating device is an induction cooker; and in the step (d), further comprising judging the heating of the heating coil according to the equivalent inductance of the resonance tank and the equivalent resistance of the resonance tank Power Burden Ratio. The detection method as described in claim 10, wherein the heating device is an induction cooker; and in the step (d), further comprising judging the heating device on the heating device according to the equivalent inductance of the resonance tank and the equivalent resistance of the resonance tank 1. The material of the food container.

Images