Heating device and detection method therefor

Abstract

The present disclosure relates to a heating device and a detection method thereof. The heating device comprises: a resonance circuit comprising an inverter circuit and a resonance tank; the inverter circuit provides a resonance tank current and a resonance tank voltage; the resonance tank comprises a heating coil, a resonance tank capacitance, a resonance tank equivalent inductance and a resonance tank equivalent resistance; a detection unit detects a capacitance voltage of the resonance tank capacitance to obtain a reference voltage value, a first zero-crossing time point, a second zero-crossing time point, a time variation, a resonance period and a negative peak voltage value of the capacitance voltage; and a control unit; wherein the detection unit calculates an inductance value of the resonance tank equivalent inductance according to the capacitance voltage of the resonance tank capacitance, the resonance period and a first calculation formula; and calculates a resistance value of the resonance tank equivalent resistance according to the resonance tank equivalent inductance, the time variation, the resonance period, the reference voltage value and the negative peak voltage value and a second calculation formula.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a heating device and a detection method thereof, and particularly relates to a heating device using the natural response characteristics of a resonance tank in a negative half-cycle discharge path to calculate the equivalent inductance and the equivalent resistance of the resonance tank according to the voltage information of the resonance tank. BACKGROUND

[0002] With the progress of science and technology in recent years, people have more choices for cooking heating devices. In addition to gas fuel heating devices, there are also microwave ovens, infrared ovens, and electric heating ovens, etc. These various heating devices have their own advantages and disadvantages and can be used for cooking different food materials and in different cooking situations to meet the needs of different users.

[0003] Generally, a heating device, such as an induction cooker, uses a heating coil to heat a food container, and the amount of heat applied to the food container is controlled by adjusting the amount of 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 amount of heat applied to the food container by the induction coil, but also affect the operating condition and current value of the induction coil. Because the material of the food container or the position of the material of the food container will induce different equivalent parameters by the equivalent inductance of the resonance tank, the existing heating device uses the resonance tank voltage, the resonance tank current, and the phase between the resonance tank voltage and the resonance tank current to calculate the equivalent resistance and the equivalent inductance of the resonance tank, and then uses the operating results of the equivalent resistance and the equivalent inductance of the resonance tank to adjust the power on the heating coil. However, this method requires additional voltage detection circuit and current detection circuit, resulting in a complex circuit and high cost of the existing heating device.

[0004] Therefore, how to develop a heating device and a detection method thereof that can improve the above-mentioned technical deficiencies of the prior art is a problem that needs to be solved urgently by those skilled in the art. SUMMARY

[0005] The present disclosure relates to a heating device and a detection method thereof, and particularly relates to a heating device using the natural response characteristics of a resonance tank in a negative half-cycle discharge path to calculate the equivalent inductance and the equivalent resistance of the resonance tank according to the voltage information of the resonance tank.

[0006] To achieve the above-mentioned purpose, a preferred embodiment of the present disclosure is a heating device, comprising: a resonant circuit, the resonant circuit comprising: an inverter circuit, providing a resonant tank current and a resonant tank voltage; and a resonant tank, comprising a heating coil, a resonant tank capacitor, a resonant tank equivalent inductance and a resonant tank equivalent resistance; a detection unit, electrically coupled to the resonant circuit, and detecting the capacitor voltage of the resonant tank capacitor to obtain a reference voltage value, a first zero-crossing time point, a second zero-crossing time point, a time variation, a resonant period and a negative peak voltage value, wherein the reference voltage value is the voltage value of the capacitor voltage when the resonant tank voltage is zero, and 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. , the resonant period is defined by the first zero-crossing time point and the second zero-crossing time point; and a control unit controls the inverter circuit to output the resonant tank current and the resonant tank voltage to control the heating power of the heating coil; wherein the detection unit calculates the inductance value of the resonant tank equivalent inductance based on the capacitance value of the resonant tank capacitor, the resonant period and the first calculation formula; the detection unit calculates the resistance value of the resonant tank equivalent resistor based on the resonant tank equivalent inductance, time variation, resonant period, reference voltage value and negative peak voltage value and the second calculation formula; the control unit controls the heating power of the heating coil based on the inductance value of the resonant tank equivalent inductance and the resistance value of the resonant tank equivalent resistor; wherein the first calculation formula is L est is the inductance value of the equivalent inductance of the resonant tank, C r is the capacitance of the resonant tank capacitor, T is the resonant period; the second equation is R est is the resistance value of the equivalent resistance of the resonant tank, V1 is the reference voltage value, Δt is the time change, V np is the negative peak voltage value.

[0007] To achieve the above-mentioned purpose, another preferred embodiment of the present disclosure is a detection method, which is applied to 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 resonant tank voltage, the resonant tank includes a heating coil, a resonant tank capacitor, a resonant tank equivalent inductor and a resonant tank equivalent resistance, and the detection method includes the steps of: (a) detecting the capacitor voltage of the resonant tank capacitor to obtain a reference voltage value, a first zero crossing time point, a second zero crossing time point, a time variation, a resonant period, a negative peak voltage value and a positive and negative peak voltage value, wherein the reference voltage value is the voltage value of the capacitor voltage when the resonant tank voltage is 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 resonant period is defined by the first zero crossing time point and the second zero crossing time point; (b) calculating the inductance value of the resonant tank equivalent inductor based on the capacitance value of the resonant tank capacitor, the resonant period and a first calculation formula, wherein the first calculation formula is Lest is the inductance value of the equivalent inductance of the resonant tank, C r is the capacitance of the resonant tank capacitor, and T is the resonant period; (c) calculating the resistance of the equivalent resistor based on the resonant tank equivalent inductance, time variation, resonant period, reference voltage, negative peak voltage, and positive peak voltage, in conjunction with the second, third, or fourth equations, where the second equation is The third operation is The fourth equation is And R est is the resistance value of the equivalent resistance of the resonant tank, V1 is the reference voltage value, Δt is the time change, V np is the negative peak voltage value, V pk is a positive peak voltage value; and (d) according to the inductance value of the resonant tank equivalent inductance and the resistance value of the resonant tank equivalent resistance, the heating power of the heating coil is controlled.

[0008] To achieve the above-mentioned purpose, another preferred embodiment of the present disclosure is a heating device, comprising:

[0009] A resonant circuit, the resonant circuit comprising: an inverter circuit, providing a resonant tank current and a resonant tank voltage; and a resonant tank, comprising a heating coil, a resonant tank capacitor, a resonant tank equivalent inductance, and a resonant tank equivalent resistance; a detection unit, electrically coupled to the resonant circuit, and detecting the capacitor voltage of the resonant tank capacitor to obtain a reference voltage value, a first zero crossing time point, a second zero crossing time point, a time variation, a resonant period, and a peak voltage value, wherein the peak voltage value is a negative peak voltage value, a positive peak voltage value, or includes a negative peak voltage value and a positive peak voltage value, the reference voltage value is the voltage value of the capacitor voltage when the resonant tank voltage is 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 resonant period is The first zero-crossing time point and the second zero-crossing time point are defined; and a control unit controls the inverter circuit to output the resonant tank current and the resonant tank voltage to control the heating power of the heating coil; wherein the detection unit calculates the inductance value of the resonant tank equivalent inductance based on the capacitance value of the resonant tank capacitor, the resonant period and the first calculation formula; the detection unit calculates the resistance value of the resonant tank equivalent resistor based on the resonant tank equivalent inductance, time variation, resonant period, reference voltage value and peak voltage value, and in conjunction with a second calculation formula, a third calculation formula or a fourth calculation formula; the control unit controls the heating power of the heating coil based on the inductance value of the resonant tank equivalent inductance and the resistance value of the resonant tank equivalent resistor; wherein the first calculation formula is L est is the inductance value of the equivalent inductance of the resonant tank, C r is the capacitance value of the resonant tank capacitor, and T is the resonant period; when the peak voltage value is a negative peak voltage value, the resistance value of the resonant tank equivalent resistance is calculated using the second calculation formula, and the second calculation formula is R est is the resistance value of the equivalent resistance of the resonant tank, V1 is the reference voltage value, Δt is the time change, V np is a negative peak voltage value; when the peak voltage value is a positive peak voltage value, the resistance value of the equivalent resistance of the resonant tank is calculated using the third formula, which is: V pk is a positive peak voltage value; wherein when the peak voltage value includes a negative peak voltage value and a positive peak voltage value, the resistance value of the equivalent resistance of the resonant tank is calculated using the fourth calculation formula, and the fourth calculation formula is BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A This is a system schematic diagram of a heating device according to a preferred embodiment of the present disclosure;

[0011] Figure 1B for Figure 1A The circuit structure diagram of the heating device shown;

[0012] Figure 2 for Figure 1B Schematic diagram of the waveforms of the resonant tank voltage and capacitor voltage of the heating device shown;

[0013] Figure 3 for Figure 1B A schematic diagram of the circuit structure of a zero-crossing detection circuit of a parameter acquisition unit of the detection unit shown;

[0014] Figure 4 For Figure 2 Under the architecture, it shows Figure 3 Schematic diagram of the waveform of the pulse width signal output by the zero-crossing detection circuit shown;

[0015] Figure 5 for Figure 1B A schematic diagram of the circuit structure of the peak detection circuit of the parameter acquisition unit of the detection unit shown;

[0016] Figure 6 Schematic diagram of the steps of the detection method of the preferred embodiment of the present invention.

[0017] Explanation of symbols

[0018] 1: Heating device

[0019] 2: Power supply circuit

[0020] 3: Detection unit

[0021] 4: Control unit

[0022] 20: Inverter circuit

[0023] 21: resonance tank

[0024] 22: resonance circuit

[0025] V in : input voltage

[0026] Q h : upper switching element

[0027] Q l : lower switching element

[0028] T1: first terminal

[0029] T2: second terminal

[0030] C r : resonance tank capacitance

[0031] L est : resonance tank equivalent inductance

[0032] R est : resonance tank equivalent resistance

[0033] I r : resonance tank current

[0034] V1: reference voltage value

[0035] Δt: time variation amount

[0036] V r : resonance tank voltage

[0037] V np : negative peak voltage value

[0038] V pk : positive peak voltage value

[0039] 30: parameter acquisition unit

[0040] 31: microprocessor

[0041] 300: zero-crossing detection circuit

[0042] 301: peak detection circuit

[0043] R1: first resistance

[0044] COM: comparator

[0045] R2: second resistance

[0046] R3: third resistance

[0047] C1: first capacitance

[0048] D z : Zener diode

[0049] G: Ground terminal

[0050] V2: voltage source

[0051] R4: the fourth resistor

[0052] R5: fifth resistor

[0053] R6: sixth resistor

[0054] C amp : Negative Feedback Amplifier

[0055] D: diode

[0056] C2: Second capacitor

[0057] 310: First computing unit

[0058] 311: Second computing unit

[0059] t0, t1, t2, t3, t4: time

[0060] T: Resonance period

[0061] 210: Heating coil

[0062] S1, S2, S3, S4: Steps

[0063] V cr : Capacitor voltage DETAILED DESCRIPTION

[0064] Some typical embodiments that embody the features and advantages of the present disclosure will be described in detail in the following description. It should be understood that the present disclosure is capable of various variations in different implementations without departing from the scope of the present disclosure, and the descriptions and drawings are intended to be illustrative rather than limiting of the present disclosure.

[0065] See also Figure 1A 、 Figure 1B and Figure 2 ,in Figure 1A This is a system schematic diagram of a heating device according to a preferred embodiment of the present disclosure. Figure 1B for Figure 1A The circuit structure diagram of the heating device shown in FIG. Figure 2 for Figure 1B The waveform diagram of the resonant tank voltage and capacitor voltage of the heating device shown in FIG. In the present disclosure, the heating device 1 may be, but is 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, which includes an inverter circuit 20 and a resonant tank 21. The inverter circuit 20 receives an input voltage V in, and includes at least one switching element, such as Figure 1B As shown, the inverter circuit 20 includes an upper switching element Q h And the lower switching element Q l , the upper switching element Q h And the lower switching element Q l The inverter circuit 20 is connected in series to form a half-bridge inverter circuit, and the upper switching element Q h And the lower switching element Q l The inverter circuit 20 switches the input voltage V in Converted to output resonant tank current I r and the resonant tank voltage V r In addition, the upper switching element Q h And the lower switching element Q l They respectively include a control end, a first current conducting end and a second current conducting end.

[0066] The resonant tank 21 includes a first end T1, a second end T2, a heating coil 210, a resonant tank capacitor C r , resonant tank equivalent inductance L est And the equivalent resistance of the resonant tank R est The first terminal T1 and the second terminal T2 are respectively electrically coupled to two current conducting terminals of a switch element of the inverter circuit 20 , for example Figure 1B As shown, the first terminal T1 of the resonant tank 21 is electrically coupled to the lower switching element Q l The second end T2 of the resonant tank 21 is electrically coupled to the lower switching element Q l The second current conducting end of the resonant tank is L. est , resonant tank equivalent resistance R est and the resonant tank capacitance C r The first terminal T1 and the second terminal T2 are connected in series in sequence, and the resonant tank capacitor C r , resonant tank equivalent inductance L est And the equivalent resistance of the resonant tank R est The series connection sequence between the first terminal T1 and the second terminal T2 is not limited to the following. Figure 1B The heating coil 210 can be changed according to the resonant tank current I provided by the inverter circuit 20. r and the resonant tank voltage V r The food container (not shown) placed on the heating device 1 is inductively heated. In addition, the resonant tank 21, the heating coil 210 and the food container constitute the equivalent inductance L of the resonant tank in the circuit. est , and the resonant tank 21, the heating coil 210 and the food container also constitute the resonant tank equivalent resistance R in the circuit. est In addition, the resonant tank capacitor Cr The capacitance value is a known value.

[0067] From the above, we can see that the equivalent inductance L of the resonant tank is esy The inductance value of the resonant tank is related to 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, any change in 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 will cause the equivalent inductance L of the resonant tank to be changed. est The inductance value of the resonant tank changes. est The resistance value of the resonant tank 21 corresponds to the resistance 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, any change in the resistance value of the resonant circuit 22, the material of the food container and the position of the food container on the heating device 1 will make the equivalent resistance R of the resonant tank est The resistance value changes.

[0068] The control unit 4 is electrically coupled to the inverter circuit 20 to control the inverter circuit 20 to output the resonant tank current I r and the resonant tank voltage V r , and control the heating power of the heating coil 210.

[0069] The detection unit 3 is electrically coupled to the resonant circuit 22, for example, electrically coupled to the resonant tank capacitor C r One end is used to detect the resonant tank capacitance C r Capacitor voltage V cr , to obtain the reference voltage value V1, the time variation Δt, the first zero crossing time point, the second zero crossing time point, the resonant period T and the capacitor voltage V cr The peak voltage value of the capacitor voltage V cr The maximum value at positive voltage, that is, the positive peak voltage value V pk (For example, Figure 2 The time t2 shown in FIG. 1 ) and / or the capacitor voltage V cr The maximum value at negative voltage, that is, the negative peak voltage value V np (For example, Figure 2 The time t4 shown in the figure is as follows, and the resonance tank capacitance C is detected by the detection unit 3 first. r Capacitor voltage V cr , to obtain the capacitor voltage V cr The negative peak voltage value V np The reference voltage V1 corresponds to the resonant tank voltage V r The capacitor voltage V at the moment of zero cr The voltage value of the inverter circuit 20 is, for example, the lower switching element Q lIn the negative half cycle, it switches from off to on, making the resonant tank voltage V r When the capacitor voltage V Cr The instantaneous voltage value constitutes the reference voltage value V1 (such as Figure 2 The first zero-crossing time point is the resonant tank voltage V r for r Zero capacitor voltage V cr The time point at which the first time is zero (e.g. Figure 2 The second zero crossing time point is the time when the resonant tank voltage V r After the capacitor voltage V is zero cr The second time point is zero (such as Figure 2 The time variation Δt is the resonant tank voltage V r The time interval from the time point of zero to the first zero crossing time point (eg Figure 2 The resonant period T is defined by the first zero crossing time point and the second zero crossing time point. np is the capacitor voltage V cr The maximum value at negative voltage (such as occurs at Figure 2 time t4 shown).

[0070] In addition, in the present disclosure, the detection unit 3 is based on the resonant tank capacitance C r The equivalent inductance L of the resonant tank is calculated by using the capacitance value, resonant period T and the first formula. est The first calculation formula is as follows:

[0071]

[0072] Among them, L est is the equivalent inductance L of the resonant tank est The inductance value, C r is the resonant tank capacitance C r The capacitance value, T is the resonant period.

[0073] Furthermore, the detection unit 3 also detects the equivalent inductance L of the resonant tank. est Inductance value, time variation Δt, resonance period T, reference voltage value V1, negative peak voltage value V np Calculate the equivalent resistance R of the resonant tank using the second equation est The resistance value of the resistor is as follows:

[0074]

[0075] where R est is the equivalent resistance of the resonant tank R estThe resistance value, V1 is the reference voltage value, Δt is the time change, V np is the negative peak voltage value.

[0076] See also Figure 3 、 Figure 4 and Figure 5 , and cooperate with Figure 1A 、 Figure 1B and Figure 2 ,in Figure 3 for Figure 1B The circuit structure diagram of the zero crossing detection circuit of the parameter acquisition unit of the detection unit shown in FIG. Figure 4 For Figure 2 Under the architecture, it shows Figure 3 The waveform diagram of the pulse width signal output by the zero-crossing detection circuit shown in FIG. Figure 5 for Figure 1B The circuit structure diagram of the 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 to the resonant tank capacitor C r One end is used to detect the resonant tank capacitance C r Capacitor voltage V cr , and the resonant tank voltage V r Since the inverter circuit 20 is in the negative half cycle, it is zero. For example, since the lower switching element Q h When it is in the negative half cycle and switches from off to on and is zero, according to the capacitor voltage V cr Obtain the resonance period T and capacitor voltage V of the resonance tank 21 cr The negative peak voltage value V np parameter information.

[0077] In the present disclosure, the parameter acquisition unit 30 can be implemented by circuit hardware or software. When the parameter acquisition unit 30 is implemented by circuit hardware, Figure 1B As shown, the parameter acquisition unit 30 includes a zero-crossing detection circuit 300 and a peak detection circuit 301. The zero-crossing detection circuit 300 is electrically coupled to the resonant circuit 22, for example, electrically coupled to the resonant tank capacitor C r One end of the resonant tank capacitance C r Capacitor voltage V cr , used to determine the capacitor voltage V cr The obtained parameter information of the resonance period T, wherein the zero crossing detection circuit 300 includes a first resistor R1, a second resistor R2, a comparator COM, a third resistor R3, a first capacitor C1 and a Zener diode D z The first end of the first resistor R1 is electrically coupled to the resonant tank capacitor C rThe first end of the second resistor R2 is electrically connected to the second end of the first resistor R1, and the voltage between the first end of the first resistor R1 and the second end of the second resistor R2 is equal to the capacitor voltage V cr The positive input terminal of the comparator COM is electrically coupled to the second terminal of the first resistor R1 and the first terminal of the second resistor R2. The negative input terminal of the comparator COM is electrically coupled to the second terminal of the second resistor R2 and the ground terminal G. The third resistor R3 is electrically coupled between the voltage source V2 and the output terminal of the comparator COM. The Zener diode D z The anode of the Zener diode D is electrically coupled to the ground terminal G. z The cathode of the first capacitor C1 is electrically coupled to the output terminal of the comparator COM and the ground terminal G, and is electrically coupled to the Zener diode D z Through the hardware structure of the zero-crossing detection circuit 300, the comparator COM can output a pulse width signal at the output terminal, wherein the capacitor voltage V cr Each time it passes through zero (i.e., through the zero crossing point), the pulse width signal corresponds to the capacitor voltage V cr The zero crossing point of the switch is switched between high level and low level. In addition, when the current switching element Q h Switching from off to on causes the resonant tank voltage V r After the voltage V is zero, the time length of the pulse width signal output by the comparator COM from the first level switching (corresponding to the first zero-crossing time point) to the second level switching (corresponding to the second zero-crossing time point) is actually equal to half of the resonant period T. The resonant period T can be obtained by multiplying half of the resonant period T by two. Therefore, the resonant period T is actually determined by the capacitor voltage V cr As defined, the zero-crossing detection circuit 300 is based on the capacitor voltage V cr Get information about the resonance period T.

[0078] The peak detection circuit 301 is electrically coupled to the resonant tank 21, for example, electrically coupled to the resonant tank capacitor C r One end of the capacitor and detect the voltage V cr , used to determine the capacitor voltage V cr Get the capacitor voltage V cr The peak voltage value V np Parameter information, such as the positive peak voltage value V pk and / or negative peak voltage V np , wherein the peak detection circuit 301 includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a negative feedback amplifier C amp , diode D and second capacitor C2. The first end of the fourth resistor R4 is electrically coupled to the resonant tank capacitor C rThe first end of the fifth resistor R2 is electrically connected to the second end of the fourth resistor R4, and the voltage between the first end of the fourth resistor R4 and the second end of the fifth resistor R2 is equal to the capacitor voltage V cr . Negative feedback amplifier C amp The non-inverting input terminal of the negative feedback amplifier C is electrically coupled to the second terminal of the fourth resistor R4 and the first terminal of the fifth resistor R5. amp The inverting input of the negative feedback amplifier C amp The anode of diode D is electrically coupled to the output terminal of negative feedback amplifier C. amp The sixth resistor R6 is electrically coupled between the cathode of the diode D and the ground terminal G. The second capacitor C2 is electrically coupled between the cathode of the diode D and the ground terminal G, and is electrically coupled in parallel with the sixth resistor R6. Through the circuit structure of the peak detection circuit 301, the peak detection circuit 301 can detect the peak voltage V according to the capacitor voltage V. cr Get the capacitor voltage V cr The positive peak voltage value V pk and / or negative peak voltage V np Information about the parameters.

[0079] When the parameter acquisition unit 30 is implemented by software, an algorithm, a calculation formula and / or a parameter relationship table can be preset in the parameter acquisition unit 30 to obtain the value of the capacitor voltage V cr And with the preset algorithm, calculation formula and / or parameter relationship, etc. to obtain the resonant period T and capacitor voltage V cr The positive peak voltage value V pk and / or negative peak voltage V np parameter information.

[0080] The microprocessor 31 may be formed by a digital signal processor (DSP) or a microcontroller unit (MCU), and is electrically coupled to 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 resonant period T from the parameter acquisition unit 30. The first calculation unit 310 calculates the resonant tank equivalent inductance L based on the capacitance value of the resonant tank capacitor Cr, the first calculation formula, and the received resonant period T. est The inductance value of the resonant tank is output as est The first calculation result of the inductance value

[0081] The second calculation unit 311 is preset with a second calculation formula and receives the equivalent inductance L of the resonant tank from the first calculation unit 310. est The first calculation result of the inductance value, and according to the capacitor voltage Vcr Get the reference voltage value V1, time change Δt and capacitor voltage V cr The negative peak voltage value V np , and based on the equivalent inductance L of the resonant tank est The inductance value, reference voltage value V1, time change Δt, capacitor voltage V cr The negative peak voltage value V np And the second calculation formula calculates the equivalent resistance R of the resonant tank est The resistance value of the resonant tank is used to output the equivalent resistance R est The second calculation result of the resistance value.

[0082] In some embodiments, the detection unit 3 may be configured to detect the equivalent inductance L of the resonant tank. est Inductance value, time variation Δt, resonance period T, reference voltage value V1, positive peak voltage value V pk Calculate the equivalent resistance R of the resonant tank using the third equation est The resistance value of the resistor is as follows:

[0083]

[0084] Where V pk is the positive peak voltage value. In addition, the second calculation unit 311 is preset with a third calculation formula and receives the equivalent inductance L of the resonant tank from the first calculation unit 310. est The first calculation result of the inductance value, and according to the capacitor voltage V cr Get the reference voltage value V1, time change Δt and capacitor voltage V cr The positive peak voltage value V pk , and based on the equivalent inductance L of the resonant tank est The inductance value, reference voltage value V1, time change Δt, capacitor voltage V cr The positive peak voltage value V pk And the third formula calculates the equivalent resistance R of the resonant tank est The resistance value of the resonant tank is used to output the equivalent resistance R est The second calculation result of the resistance value.

[0085] In some embodiments, the detection unit 3 may be configured to detect the equivalent inductance L of the resonant tank. est Inductance value, time variation Δt, resonance period T, reference voltage value V1, negative peak voltage value V np , positive peak voltage value V pk Calculate the equivalent resistance R of the resonant tank using the fourth equation est The resistance value of the resistor is as follows:

[0086]

[0087] In addition, the second calculation unit 311 is preset with a fourth calculation formula and receives the equivalent inductance L of the resonant tank from the first calculation unit 310. est The first calculation result of the inductance value, and according to the capacitor voltage V cr Get the reference voltage value V1, time change Δt and capacitor voltage V cr The negative peak voltage value V np With the positive peak voltage value V pk , and based on the equivalent inductance L of the resonant tank est The inductance value, reference voltage value V1, time change Δt, capacitor voltage V cr The negative peak voltage value V np With the positive peak voltage value V pk And the fourth formula calculates the equivalent resistance R of the resonant tank est The resistance value of the resonant tank is used to output the equivalent resistance R est The second calculation result of the resistance value.

[0088] In some embodiments, the control unit 4 of the heating device 1 may further obtain the equivalent inductance L of the resonant tank according to the first calculation result and the second calculation result output by the microprocessor 31. est And the equivalent resistance of the resonant tank R est , and then according to the equivalent inductance L of the resonant tank est And the equivalent resistance of the resonant tank R est Various controls are performed on the resonant circuit 22. For example, the control unit 4 can control the resonant tank equivalent inductance L according to the resonant tank equivalent inductance L. est And the equivalent resistance of the resonant tank R est The control unit 4 can determine whether the heating coil 210 is turned on or off and whether the food container is still on the heating device 1 according to the parameter value of the resonant tank equivalent inductance L. est And the equivalent resistance of the resonant tank R est The control unit 4 can also determine the load ratio of the heating power of the heating coil 210 according to the parameter value of the resonant tank equivalent inductance L est And the equivalent resistance of the resonant tank R est The output power of the heating device 1 is modified in real time by the change of the parameter value, and the control unit 4 can be adjusted according to the equivalent inductance L of the resonant tank. est And the equivalent resistance of the resonant tank R est The parameter value determines the material of the food container.

[0089] The following will roughly deduce the above-mentioned first equation (1), second equation (2), third equation (3) and fourth equation (4). Please cooperate with Figures 1A to 3 First, the main working principle of the present disclosure is based on the natural response characteristics of the resonant tank 21. When time t≧0, the resonant tank 21 enters the natural response, so the capacitor voltage Vcr The general formula can be expressed as:

[0090] v cr (t) = e -αt (B1 cosω d t+B2 sinω d t)---(5);

[0091] where v cr (t) is the capacitor voltage V cr is a time function, α is the attenuation coefficient, ω d is the damping resonance frequency, B1 and B2 are arbitrary constants determined by the boundary conditions. Since the heating device 1 is an induction cooker, ω o 2 >>α 2 , so that the resonant tank 21 operates in the underdamped region (underdamped), and can simplify where ω o is the natural resonant frequency. By using the sum angle formula and rearranging formula (5), we can obtain:

[0092] v cr (t) = V p e -αt (sinω d t+θ)---(6);

[0093] Where V p is the voltage peak value of the resonance tank 21 during natural resonance, and θ is the angle.

[0094] In addition, in formula (6), some parameters have the following general formula:

[0095]

[0096]

[0097] Therefore, equation (1) can be derived from equation (7), and the resonant frequency f o The relationship between the resonant period T is as follows:

[0098]

[0099] Since the upper switching element Q h When the working cycle is small, the discharge waveform of the resonant tank 21 in the negative half cycle is relatively complete. At this time, the zero-crossing detection circuit 300 can be used to obtain half of the resonant cycle T / 2, and then the first calculation unit 310 can be used to combine the half of the resonant cycle T / 2 with the formula (9) and substitute it into the formula (1) to obtain the equivalent inductance L of the resonant tank. est inductance value.

[0100] In addition, since the capacitor voltage V cr is always zero, so the present disclosure uses the capacitor voltage V cr The zero crossing point is used as the reference point and the calculation is performed in the form of relative angles. Figure 2 As shown, due to the lower switching element Q h When the capacitor voltage V cr The instantaneous voltage value of the reference voltage V1 is formed, so it is assumed that the upper switching element Q h Turn off the next switching element Q l The turn-on moment occurs at t=t0, and assuming that the switching element Q l After switching from off to on and becoming zero, the capacitor voltage V cr The first time the capacitor passes through the zero crossing point (the first zero crossing time point) occurs at an angle of π, and assuming that the capacitor voltage V cr The positive peak voltage value V pk Occurs at t = t2 (usually occurs at t = π / 2), and assuming that the capacitor voltage V cr The negative peak voltage value V np If it occurs at t = t4 (usually occurs at t = 3π / 2), then t = 0, t = t2 and t = t4 can be obtained by equation (6) as follows:

[0101] V cr =V P sin(θ);t=t0---(10);

[0102]

[0103]

[0104] Among them Figure 2 It can be seen that the lower switching element Q h After switching from off to on, the capacitor voltage V Cr The sampling time point of the reference voltage value V1 can be obtained by subtracting the time change Δt from the time point of the first zero crossing, and the capacitor voltage V cr The positive peak voltage value V pk Occurs at t = π / 2, and the capacitor voltage V cr The negative peak voltage value V np It occurs at t = 3π / 2, so we can get the following formula:

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] Finally, by dividing equations (10) and (11), we can get the equivalent resistance of the resonant tank R est The third equation of the equation. After dividing equation (10) and (12), the equivalent resistance of the resonant tank R est The second operation of .

[0111] After dividing equations (11) and (12), the equivalent resistance of the resonant tank R can be obtained. est The fourth equation of .

[0112] From the above, it can be seen that when the detection unit 3 detects the resonant tank capacitance C r Capacitor voltage V cr , to obtain the capacitor voltage V cr The negative peak voltage value V np When the equivalent resistance of the resonant tank is R est The general formula is the second operational formula (2). When the detection unit 3 detects the resonance tank capacitance C r Capacitor voltage V cr , to obtain the capacitor voltage V cr The positive peak voltage value V pk When the equivalent resistance of the resonant tank is R est The general formula is the third operational formula (3). When the detection unit 3 detects the resonant tank capacitance C r Capacitor voltage V cr , to obtain the capacitor voltage V cr The positive peak voltage value V pk And the negative peak voltage value V np When the equivalent resistance of the resonant tank is R est The general formula is the fourth equation (4).

[0113] In some embodiments, the detection unit 3 may be, but is not limited to, composed of a controller.

[0114] In some embodiments, the inverter circuit 20 is not limited to Figure 1B The upper switching element Q h And the lower switching element Q lIn other embodiments, the inverter circuit 20 may include a single switching element or four or more switching elements. When the inverter circuit 20 includes a single switching element, the first end T1 and the second end T2 of the resonant tank 21 are electrically coupled to the first current conducting end and the second current conducting end of the single switching element, respectively. 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 electrically coupled to the first current conducting end and the second current conducting end of the lower switching element in any bridge arm, respectively. Furthermore, in embodiments where the inverter circuit 20 includes a single switching element or four or more switching elements, the operation of the heating device 1 of the present disclosure is similar to that described above and will not be further described here.

[0115] See also Figure 6 , which is a schematic diagram of the steps of the detection method of the preferred embodiment of the present disclosure. The detection method of this embodiment can be applied to Figure 1B The detection unit 3 of the heating device 1 shown includes the following steps.

[0116] Step S1: The detection unit 3 detects the capacitance C of the resonant tank. r Capacitor voltage V cr Get the reference voltage value V1, time variation Δt, first zero crossing time point, second zero crossing time point, resonance period T, negative peak voltage value V np And the positive peak voltage value V pk .

[0117] Step S2: The detection unit 3 calculates the equivalent inductance L of the resonant tank according to the capacitance value of the resonant tank capacitor Cr, the resonant period T, and the first calculation formula. est inductance value.

[0118] Step S3: The detection unit 3 detects the equivalent inductance L of the resonant tank. est Inductance value, time variation Δt, resonance period T, reference voltage value V1, negative peak voltage value V np , positive peak voltage value V pk And use the second, third or fourth formula to calculate the equivalent resistance R of the resonant tank. est resistance value.

[0119] Step S4, the control unit 4 calculates the equivalent inductance L of the resonant tank. est The inductance value and the equivalent resistance R of the resonant tank est The resistance value is used to control the heating power of the heating coil 210.

[0120] In some embodiments, step S4 may further include calculating the equivalent inductance L of the resonant tank. est And the equivalent resistance of the resonant tank R estDetermine whether a food container is placed on the heating device 1. In step S4, it may further include determining the equivalent inductance L of the resonant tank. est And the equivalent resistance of the resonant tank R est Determine the heating power burden ratio of the heating coil 210. Furthermore, in step S4, it may further include determining the equivalent inductance L of the resonant tank. est And the equivalent resistance of the resonant tank R est Determine the material of the food container on the heating device 1.

[0121] In summary, the present disclosure is a heating device and a detection method applicable thereto, wherein the heating device has a resonant tank, and based on the natural response characteristics of the resonant tank's discharge path in the negative half-cycle, the heating device of the present disclosure utilizes the information of the capacitance voltage of the resonant tank capacitor and cooperates with the aforementioned first equation (1) to calculate the inductance value of the resonant tank's equivalent inductance, and cooperates with the second equation (2), the third equation (3) or the fourth equation (4) to calculate the inductance value of the resonant tank's equivalent resistance. Therefore, compared with traditional heating devices, the heating device of the present disclosure only needs to set up fewer detection circuits, thereby achieving the technical effect of simple circuits and low cost. In fact, the heating device of the present disclosure does not need to detect the current information of the resonant tank, that is, it does not need to use a current sensing element, so it can also achieve a technical effect of low cost.

Claims

1. A heating device comprising: A resonant circuit comprising: an inverter circuit providing a resonant tank current and a resonant tank voltage; and A resonant tank comprising a heating coil, a resonant tank capacitor, a resonant tank equivalent inductor, and a resonant tank equivalent resistor; a detection unit electrically coupled to the resonant circuit and detecting a capacitor voltage of the resonant tank capacitor to obtain a reference voltage value, a first zero-crossing time point, a second zero-crossing time point, a time variation, a resonant period, and a negative peak voltage value, wherein the reference voltage value is the voltage value of the capacitor voltage when the resonant tank voltage is 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 resonant period is defined by the first zero-crossing time point and the second zero-crossing time point; and a control unit for controlling the inverter circuit to output the resonant tank current and the resonant tank voltage to control the heating power of the heating coil; in, The detection unit calculates the inductance of the resonant tank equivalent inductor based on the capacitance of the resonant tank capacitor, the resonant period, and a first calculation formula; the detection unit calculates the resistance of the resonant tank equivalent resistor based on the resonant tank equivalent inductor, the time variation, the resonant period, the reference voltage, the negative peak voltage, and a second calculation formula; the control unit controls the heating power of the heating coil based on the inductance of the resonant tank equivalent inductor and the resistance of the resonant tank equivalent resistor; The first operational formula is L est is the inductance value of the equivalent inductance of the resonant tank, C r is the capacitance of the resonant tank capacitor, and T is the resonant period; The second operational formula is R est is the resistance value of the equivalent resistance of the resonant tank, V1 is the reference voltage value, Δt is the time change, V np is the negative peak voltage value.

2. The heating device as described in claim 1, wherein the detection unit includes a parameter acquisition unit, which is electrically coupled to the resonant tank and detects the capacitor voltage, and when the resonant tank voltage is zero, obtains the resonant period according to the capacitor voltage, and obtains the negative peak voltage value or the positive peak voltage value of the capacitor voltage according to the capacitor voltage.

3. The heating device according to claim 2, wherein the parameter acquisition unit comprises: a zero-crossing detection circuit electrically coupled to the resonant tank, detecting the capacitor voltage and obtaining the resonant period according to the capacitor voltage; and A peak detection circuit is electrically coupled to the resonant tank and detects the capacitor voltage, and obtains the negative peak voltage value or the positive peak voltage value according to the capacitor voltage.

4. The heating device as claimed in claim 3, wherein the zero-crossing detection circuit comprises: a first resistor, a first end of the first resistor being electrically coupled to one end of the resonant tank capacitor; a second resistor, wherein a first end of the second resistor is electrically connected to a second end of the first resistor, and a voltage between the first end of the first resistor and a second end of the second resistor is equal to the capacitor voltage; a comparator, wherein a positive input terminal of the comparator is electrically coupled to the second terminal of the first resistor and the first terminal of the second resistor, and a negative input terminal of the comparator is electrically coupled to the second terminal of the second resistor and ground; a third resistor electrically coupled between a voltage source and an output terminal of the comparator; a Zener diode, an anode of the Zener diode being electrically coupled to the ground terminal, and a cathode of the Zener diode being 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 to the Zener diode in parallel.

5. The heating device as claimed in claim 3 , wherein the peak detection circuit comprises: a fourth resistor, a first end of the fourth resistor being electrically coupled to one end of the resonant tank capacitor; a fifth resistor, wherein a first end of the fifth resistor is electrically connected to a second end of the fourth resistor, and a voltage between the first end of the fourth resistor and a second end of the fifth resistor is equal to the capacitor voltage; a negative feedback amplifier, wherein a non-inverting input terminal of the negative feedback amplifier is electrically coupled to the second terminal of the fourth resistor and the first terminal of the fifth resistor, and an inverting input terminal of the negative feedback amplifier is electrically coupled to an output terminal of the negative feedback amplifier; a diode, an anode of the diode being electrically coupled to an output terminal of the negative feedback amplifier; a sixth resistor electrically coupled between a cathode of the diode and the ground; A second capacitor is electrically coupled between the cathode of the diode and the ground terminal, and is electrically coupled to the sixth resistor in parallel.

6. The heating device according to claim 4, wherein the detection unit further comprises a microprocessor, and the microprocessor comprises: a first calculation unit that presets the first calculation formula, calculates the inductance of the resonant tank equivalent inductor according to the capacitance of the resonant tank capacitor, the resonant period provided by the zero-crossing detection circuit, and the first calculation formula, and outputs a first calculation result to the control unit; and A second calculation unit presets the second calculation formula and receives the first calculation result provided by the first calculation unit, and obtains the reference voltage value, the time variation and the negative peak voltage value of the capacitor voltage according to the capacitor voltage, and further calculates the resistance value of the equivalent resistor of the resonant tank according to the inductance value of the equivalent inductor of the resonant tank, the reference voltage value, the time variation, the negative peak voltage value of the capacitor voltage and the second calculation formula, and outputs a second calculation result to the control unit.

7. The heating device as claimed in claim 6, wherein the microprocessor is composed of a digital signal processor or a microcontroller. The heating device as claimed in claim 1 , wherein the heating device is an induction cooker.

9. The heating device as claimed in claim 1, wherein the inverter circuit includes an upper switching element and a lower switching element connected in series, the upper switching element and the lower switching element are switched on and off alternately, and the resonant tank includes a first end and a second end, the first end and the second end are respectively electrically coupled to two current conduction ends of the lower switching element.

10. A detection method, applied to a detection unit of a heating device, wherein the heating device further comprises a resonant circuit, the resonant circuit comprising an inverter circuit and a resonant tank, the inverter circuit providing a resonant tank current and a resonant tank voltage, the resonant tank comprising a heating coil, a resonant tank capacitor, a resonant tank equivalent inductance, and a resonant tank equivalent resistance, the detection method comprising: Step (a) detecting a capacitor voltage of the resonant tank capacitor to obtain a reference voltage value, a first zero-crossing time point, a second zero-crossing time point, a time variation, a resonant period, a negative peak voltage value, and a positive and negative peak voltage value, wherein the reference voltage value is the voltage value of the capacitor voltage corresponding to when the resonant tank voltage is 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 resonant period is defined by the first zero-crossing time point and the second zero-crossing time point; Step (b) calculates the inductance of the resonant tank equivalent inductor according to the capacitance of the resonant tank capacitor, the resonant period and a first calculation formula, wherein the first calculation formula is L est is the inductance value of the equivalent inductance of the resonant tank, C r is the capacitance of the resonant tank capacitor, and T is the resonant period; Step (c) calculates the resistance value of the resonant tank equivalent resistor based on the resonant tank equivalent inductance, the time variation, the resonant period, the reference voltage value, the negative peak voltage value, and the positive and negative peak voltage values ​​in conjunction with a second calculation formula, a third calculation formula, or a fourth calculation formula, wherein the second calculation formula is The third operational formula is The fourth equation is And R est is the resistance value of the equivalent resistance of the resonant tank, V1 is the reference voltage value, Δt is the time change, V np is the negative peak voltage value; as well as Step (d) controls the heating power of the heating coil according to the inductance value of the equivalent inductance of the resonant tank and the resistance value of the equivalent resistance of the resonant tank.

11. The detection method of claim 10, wherein the heating device is an induction cooker; and in step (d), further comprising determining whether a food container is placed on the heating device based on the equivalent inductance and the equivalent resistance of the resonant tank.

12. The detection method as described in claim 10, wherein the heating device is an induction cooker; and in the step (d), further comprising determining the heating power burden ratio of the heating coil based on the equivalent inductance of the resonant tank and the equivalent resistance of the resonant tank.

13. The detection method of claim 10, wherein the heating device is an induction cooker; and in step (d), further comprising determining the material of a food container on the heating device based on the equivalent inductance and the equivalent resistance of the resonant tank.

14. A heating device comprising: A resonant circuit comprising: an inverter circuit providing a resonant tank current and a resonant tank voltage; and A resonant tank comprising a heating coil, a resonant tank capacitor, a resonant tank equivalent inductor, and a resonant tank equivalent resistor; a detection unit electrically coupled to the resonant circuit and detecting a capacitor voltage of the resonant tank capacitor to obtain a reference voltage value, a first zero-crossing time point, a second zero-crossing time point, a time variation, a resonant period, and a peak voltage value, wherein the peak voltage value is a negative peak voltage value, a positive peak voltage value, or includes the negative peak voltage value and the positive peak voltage value; the reference voltage value is a voltage value of the capacitor voltage when the resonant tank voltage is zero; the time variation is a time interval from the time point when the resonant tank voltage is zero to the first zero-crossing time point; and the resonant period is defined by the first zero-crossing time point and the second zero-crossing time point; as well as a control unit for controlling the inverter circuit to output the resonant tank current and the resonant tank voltage to control the heating power of the heating coil; The detection unit calculates the inductance of the resonant tank equivalent inductor based on the capacitance of the resonant tank capacitor, the resonant period, and a first calculation formula; the detection unit calculates the resistance of the resonant tank equivalent resistor based on the resonant tank equivalent inductor, the time variation, the resonant period, the reference voltage, and the peak voltage, in conjunction with a second calculation formula, a third calculation formula, or a fourth calculation formula; and the control unit controls the heating power of the heating coil based on the inductance of the resonant tank equivalent inductor and the resistance of the resonant tank equivalent resistor. The first operational formula is L est is the inductance value of the equivalent inductance of the resonant tank, C r is the capacitance of the resonant tank capacitor, and T is the resonant period; When the peak voltage value is the negative peak voltage value, the resistance value of the equivalent resistance of the resonant tank is calculated using the second calculation formula, and the second calculation formula is R est is the resistance value of the equivalent resistance of the resonant tank, V1 is the reference voltage value, Δt is the time change, V np is the negative peak voltage value; When the peak voltage value is the positive peak voltage value, the resistance value of the equivalent resistance of the resonant tank is calculated using the third calculation formula, and the third calculation formula is: V pk is the positive peak voltage value; When the peak voltage value includes the negative peak voltage value and the positive peak voltage value, the resistance value of the equivalent resistance of the resonant tank is calculated using the fourth calculation formula. The fourth calculation formula is:

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