JP4364082B2 - Electromagnetic induction heating cooker - Google Patents

Description

  The present invention relates to an electromagnetic induction heating cooker that uses an inverter circuit to supply a high-frequency current to an induction heating coil and heat the pan by electromagnetic induction, and in particular, discriminates between matching and mismatching of the inverter circuit and the induction heating coil. It is related to the technology.

  FIG. 7 is an electrical connection diagram of a conventional electromagnetic induction heating apparatus. The rectifier circuit DR1 rectifies the three-phase AC commercial power supply AC and converts it into a DC voltage, and the smoothing capacitor C1 smoothes the voltage converted into DC by the rectifier circuit DR1.

  The first switching element TR1 and the second switching element TR2 are switching elements that form a half-bridge type inverter circuit, and for example, MOSFETs or IGBTs are used. The induction heating coil L forms a series resonance circuit with the resonance capacitor C2 and the resonance capacitor C3, and a pan (not shown) is placed on the induction heating coil L and the pan is heated by electromagnetic induction.

  The power calculation circuit PO receives a signal from the input voltage detection circuit PT1 that detects the voltage of the smoothing capacitor C1 (input voltage of the inverter) and a signal from the input current detection circuit CT1 that detects the current at the input terminal of the inverter. Calculate the input power of the inverter. The drive circuit DC drives the switching element TR1 and the switching element TR2.

  In the power control differential amplifier DA1, an input power calculation signal Po from the power calculation circuit PO is input to a non-inverting input terminal of an amplifier circuit (not shown), and a predetermined power setting signal Wa is input to the inverting input terminal from the power setting circuit WA. Each is entered. Therefore, when the input power calculation signal Po is smaller than the power setting signal Wa, the power control differential amplifier circuit DA1 outputs a negative signal obtained by amplifying the knitting difference between the two, and the input power calculation signal Po is the power setting signal. When larger than Wa, a positive signal obtained by amplifying the knitting difference between the two is output.

  The phase difference detection circuit PF detects the phase difference between the second switching element drive signal Tr2 and the output current detection signal Ct2, converts this phase difference into a voltage, and outputs it as a phase difference detection signal Pf. When the value is large, the output voltage is low, and when it is small, the output voltage is high.

  The control circuit is formed by a V / F converter VF, a diode DR1, and a resistor (not shown). The control circuit is connected to the power control differential amplifier circuit DA1 via the diode DR1, and the power control differential amplifier signal Da1. The frequency command signal Vf is controlled according to the value of.

  The input terminal of the V / F converter VF is grounded via a resistor (not shown). Therefore, unless the output signal Da1 of the power control differential amplifier DA1 is a positive value, the voltage at the input terminal of the V / F converter VF is kept at a zero potential, and the input potential of the V / F converter VF is zero. At this time, a frequency command signal Vf for controlling the inverter at the lowest frequency is output. Here, the minimum frequency of the inverter circuit is set to a value slightly higher than the resonance frequency of the series resonance circuit including the heating coil L including the cooking pot to be placed and the resonance capacitors C2 and C3.

  The phase discrimination circuit CP compares the phase difference reference value Fr whose phase difference is slightly higher than zero with the phase difference detection signal Pf, and when the phase difference detection signal Pf is larger than the phase reference value Fr, the phase discrimination signal Set Cp to Hihg level.

  The power discriminating circuit PP compares a predetermined maximum power setting value Wg (not shown) with the power calculation signal Po. When the power calculation signal P0 is larger than the maximum power setting value Wg, the power discrimination signal Pp is set to High. To level.

  The logic circuit OR turns on the display circuit LD4 when the phase determination signal Cp is at the High level or the power determination signal is at the High level, indicating that the induction heating coil L is inconsistent with the inverter circuit. To do.

  Further, when the output of the logic circuit OR is at a high level, the operation of the electromagnetic induction heating cooker is stopped. As a prior document disclosing the above technique, for example, there is Patent Document 1.

Japanese Patent Laid-Open No. 11-54249

  In the above-described electromagnetic induction heating cooker of the prior art, a user may newly create and use an induction heating coil depending on the shape, material, or kitchen equipment of the pan. At this time, it is important to determine whether or not the inductance value of the induction heating coil matches the inverter circuit. If an induction heating coil whose inductance value does not match is installed and used in the electromagnetic induction heating cooker, in the worst case, the inverter circuit or the like may be destroyed.

  In the above-mentioned prior art document 1, if the maximum power value is not obtained even when the inverter circuit reaches a predetermined frequency, or when the inverter circuit is close to the resonance frequency, the induction heating coil must be matched with the inverter circuit. It was determined. From the above, although it is possible to determine whether or not the newly produced induction heating coil is matched to the inverter circuit in the prior art document 1, it is impossible to grasp whether the inductance value of the induction heating coil is too large or too small. The inductance value of the induction heating coil is very difficult to adjust. Then, this invention is providing the electromagnetic induction heating cooking appliance which can solve the subject mentioned above.

  In order to solve the above-described problems, a first invention includes a resonance capacitor, an induction heating coil that forms a series resonance circuit together with the resonance capacitor, an inverter circuit that supplies a high-frequency current to the induction heating coil, and the inverter A power calculation circuit for calculating an input power value of the circuit; a power setting circuit for setting a power setting value to a predetermined value; and controlling an output frequency of the inverter circuit so that the input power value becomes the power setting value A power discriminating circuit that sets the power set value to a maximum power set value and outputs a power discriminating signal when the input power value reaches the maximum power set value. And an overcurrent determination circuit for determining an overcurrent when the output current of the inverter circuit is larger than a predetermined current limit value and outputting an overcurrent determination signal; A phase discrimination circuit that detects a phase difference between an output voltage and an output current of the inverter circuit and outputs a phase discrimination signal when the phase difference is close to zero and approaches a resonance frequency; and the induction heating coil includes the inverter circuit When the inverter circuit is started by setting the power setting value to the maximum power setting value in order to confirm that the power determination value is matched, the power determination signal regardless of the overcurrent determination signal and the phase determination signal Is output and the power determination signal is not output and the overcurrent determination signal is output, it is determined that the inductance value of the induction heating coil is too small, and the power determination If no signal is output and the phase determination signal is output, it is determined that the inductance value of the induction heating coil is too large, and the matching / incompatibility is determined. A matching and non-matching determination circuit for outputting a discrimination signal of cases, an electromagnetic induction cooker, characterized in that a display circuit for displaying the contents of the discrimination signal of the matched-mismatched.

A second aspect of the present invention is the electromagnetic induction heating cooker according to claim 1 , further comprising a display circuit that displays the input power value .

  According to the first invention, when the induction heating coil is newly produced and used according to the difference in the shape, material or kitchen equipment of the pan, it is automatically determined whether or not the induction heating coil matches the inverter circuit. In the case of mismatch, since it is displayed that the inductance value of the induction heating coil is too large or too small, adjustment of the inductance value of the induction heating coil is facilitated. Furthermore, if the mismatched induction heating coil is used for a long time, the inverter circuit or the like may be destroyed in the worst case. However, the present invention prevents the inverter circuit and the like from being damaged by providing a limiting circuit.

  In the second aspect of the present invention, the matching / cooking mode switch is easily provided by providing the matching / cooking mode switch.

  In the third invention, by displaying the input power value, it is possible to predict how much the inductance value of the induction heating coil is too large or too small, and fine adjustment of the inductance value of the induction heating coil is possible. It becomes very easy.

[Embodiment 1]
FIG. 1 is an electrical connection diagram of an electromagnetic induction heating cooker according to the present invention. In FIG. 1, the same reference numerals as those in the electrical connection diagram of the electromagnetic induction heating cooker of the prior art shown in FIG.

  As shown in FIG. 2, in the output current limit circuit DA2, the output current detection signal Ct2 from the output current detection circuit CT2 is input to the non-inverting input terminal, and the current limit setting signal Ic is input to the inverting input terminal from the current limit setting circuit IC. Is done. Therefore, when the output current detection signal Ct2 is smaller than the current limit setting signal Ic, the output current limit circuit DA2 outputs a negative signal obtained by amplifying the deviation between the two, and the output current detection signal Ct2 is When it is larger than the current limit setting signal Ic, a positive signal obtained by amplifying the deviation between the two is output.

  As shown in FIG. 2, in the phase limit circuit DA3, the phase difference detection signal Pf from the phase difference detection circuit PF is input to the non-inverting input terminal, and the phase limit setting signal Fs from the phase limit setting circuit FS is input to the inverting input terminal. The Accordingly, when the phase difference detection signal Pf is smaller than the phase limit setting signal Fs, the phase limit circuit DA3 outputs a negative signal obtained by amplifying the difference between the two, and the phase difference detection signal Pf is the phase difference detection signal Pf. When it is larger than the limit setting signal Fs, a positive signal obtained by amplifying the deviation between the two is output.

The V / F converter VF is connected to the power control differential amplifier circuit DA1 via the diode DR1, and is connected to the output current limit circuit DA2 and the phase limit circuit DA3 via the diode DR3. And the frequency command signal Vf according to the maximum values of the power control differential amplification signal Da1, the output current limit signal Da2, and the phase limit signal Da3.
To control.

  The overcurrent determination circuit IP compares the output current detection signal Ct2 from the output current detection circuit CT2 with the current limit setting signal Ic from the current limit setting circuit IC, and the output current detection signal Ct2 is compared with the current limit setting signal Ic. When it is larger, it is determined as an overcurrent, and the overcurrent determination signal Ip is set to High level and output.

  The phase discrimination circuit CP compares the phase difference detection signal Pf from the phase difference detection circuit PF with the phase limit setting signal Fs from the phase limit setting circuit FS, and the phase difference detection signal Pf is compared with the phase limit setting signal Fs. When the frequency is larger, it is determined that the frequency has approached the vicinity of the resonance frequency, and the phase determination signal Cp is set to High level and output.

  The matching / mismatch determining circuit KD determines that the inductance value of the induction heating coil L is too small when the power determining signal Pp is at the low level and the overcurrent determining signal Ip is at the high level, and displays the determined content on the display circuit LD1. indicate. Further, when the power determination signal Pp is at the low level and the phase determination signal Cp is at the high level, it is determined that the inductance value of the induction heating coil L is too large, and the determined content is displayed on the display circuit LD2. Further, when the power determination signal becomes High level, the determination is made by determining that the induction heating coil is matched with the inverter circuit regardless of the level of the overcurrent determination signal Ip or the phase determination signal Cp. Is displayed on the display circuit LD3.

  The drive circuit DC performs PFM control that modulates the pulse frequency with a constant pulse width ratio according to the value of the output signal Vf from the V / F converter VF shown below, and performs the first switching element TR1 and the second switching element TR1. A first switching element drive signal Tr1 and a second switching element drive signal Tr2 that alternately drive the switching element TR2 are output.

  When the power is set to the maximum power set value Wg by the power setting circuit WA and the cooker starts the cooker, an excessive current flows. The soft start circuit SS is provided in consideration of such a situation. At the start of startup, even if a high power is set, the power is gently increased from a small power by the operation of the soft start circuit SS.

  FIG. 3 is a waveform diagram when the inductance value of the induction heating coil L is too small to obtain the maximum rated power and the output current of the inverter circuit becomes an overcurrent. 3A shows the soft start signal Ss, FIG. 3B shows the output current detection signal Ct2, FIG. 3C shows the input power calculation signal Po, and FIG. 3D shows the phase difference detection signal Pf, FIG. 3E shows the output current limit signal Da2, FIG. 3F shows the input signal Vi of the V / F converter VF, and FIG. ) Indicates an overcurrent determination signal Ip.

  When a start signal (not shown) is input at time t = t0 shown in FIG. 3, the soft start signal Ss shown in FIG. 3A gradually decreases, and conversely, the output current detection signal Ct2 and the input power calculation The signal Po and the phase difference detection signal Pf increase gently.

  The input signal Vi of the V / F converter VF shown in FIG. 3F forms an OR logic by the diodes DR1 to DR4 and the resistor R1 of the input terminal, and the power control differential amplification signal Da1 and the output current limit signal Da2 Of the phase limit signal Da3 and the soft start signal Ss, the signal having the largest value is the input signal Vi.

  When the input signal Vi of the V / F converter VF shown in FIG. 3F decreases, the value of the output current detection signal Ct2 increases conversely.

  When the output current detection signal Ct2 keeps increasing at time t = t1 and reaches the current limit setting signal Ic shown in FIG. 3B, the overcurrent determination circuit IP determines that it is an overcurrent, and FIG. The overcurrent determination signal Ip shown in FIG. At this time, since the phase difference detection signal Pf shown in FIG. 3D is smaller than the phase limit setting signal Fs, the phase determination circuit CP sets the phase determination signal Cp to the low level. Furthermore, since the input power calculation signal Po shown in FIG. 3C is also smaller than the maximum power setting signal Wg, the power determination circuit PP sets the power determination signal Pp to the low level.

  The matching / mismatch determining circuit KD determines that the inductance value of the induction heating coil L is too small when the overcurrent determination signal Ip is at the high level, the phase determination signal Cp is at the low level, and the power determination signal Pp is at the low level. Then, it is determined that the inverter circuit does not match, and the determined content is displayed on the display circuit LD1.

  After the time t = t2, the output current limiting signal Da2 having the largest value among the power control differential amplification signal Da1, the output current limiting signal Da2, the phase limiting signal Da3, or the soft start signal Ss becomes the input signal Vi. The output current is limited.

  FIG. 4 is a waveform diagram when the inductance value of the induction heating coil L is too large to obtain the maximum rated power, and the leading phase of the output voltage of the inverter circuit is close to zero and approaches the resonance frequency. 4A shows the soft start signal Ss, FIG. 4B shows the output current detection signal Ct2, FIG. 4C shows the input power calculation signal Po, and FIG. 4D shows the phase difference detection signal Pf, FIG. 4E shows the phase limit signal Da3, FIG. 4F shows the input signal Vi of the V / F converter VF, and FIG. Indicates the phase discrimination signal Cp.

  When a start signal (not shown) is input at time t = t0 shown in FIG. 4, the value of the soft start signal Ss shown in FIG. 4 (A) gradually decreases, and conversely, the output current detection signal Ct2 The power calculation signal Po and the phase difference detection signal Pf increase gently.

  The input signal Vi of the V / F converter VF shown in FIG. 4 (F) has the largest value among the power control differential amplification signal Da1, the output current limit signal Da2, the phase limit signal Da3, or the soft start signal Ss. The signal becomes the input signal Vi.

  As the input signal Vi of the V / F converter VF decreases, the value of the phase difference detection signal Pf of the inverter circuit shown in FIG.

  At time t = t1, when the phase difference detection signal Pf keeps increasing and reaches the phase limit setting signal Fs shown in FIG. 4D, the phase discrimination circuit CP makes the advance phase of the output voltage of the inverter circuit near zero. It is determined that the resonance frequency is approached, and the phase determination signal Cp shown in FIG. 4G is set to the high level. At this time, since the output current detection signal Ct2 shown in FIG. 4B is smaller than the current limit setting signal Ic, the overcurrent determination circuit IP sets the overcurrent determination signal Cp to the low level. Furthermore, since the input power calculation signal Po shown in FIG. 4C is also smaller than the maximum power setting signal Wg, the power determination circuit PP sets the power determination signal Pp to the low level.

  The matching / mismatch determining circuit KD determines that the inductance value of the induction heating coil L is too large when the phase determining signal Cp is High level, the overcurrent determining signal Ip is Low level, and the power determining signal Pp is Low level, It is determined that there is no matching with the inverter circuit, and the determined content is displayed on the display circuit LD2.

  After the time t = t2, the phase limit signal Da3 having the largest value among the power control differential amplification signal Da1, the output current limit signal Da2, the phase limit signal Da3, or the soft start signal Ss becomes the input signal Vi, and the output Current is limited.

  FIG. 5 is a waveform diagram when the inductance value of the induction heating coil L is a predetermined value, the maximum rated power is obtained, and the induction heating coil is matched with the inverter circuit. 5A shows the soft start signal Ss, FIG. 5B shows the output current detection signal Ct2, FIG. 5C shows the input power calculation signal Po, and FIG. D) shows the phase difference detection signal Pf, FIG. 5 (E) shows the current control differential amplification signal Da1, and FIG. 5 (F) shows the input signal Vi of the V / F converter VF. 5 (G) indicates the power discrimination signal Pp.

  When a start signal (not shown) is input at time t = t0 shown in FIG. 5, the value of the soft start signal Ss shown in FIG. 5A gradually decreases, and conversely, the output current detection signal Ct2 is input. The power calculation signal Po and the phase difference detection signal Pf increase gently.

  As the input signal Vi of the V / F converter VF decreases, the value of the input power calculation signal Po shown in FIG.

  At time t = t1, when the input power calculation signal Po keeps increasing and reaches the maximum power set value Wg shown in FIG. 4C, the power discriminating circuit PP sets the power phase discrimination signal Ip shown in FIG. 4G to High. To level.

  When the power discrimination signal Pp becomes High level, the matching / mismatch discrimination circuit KD discriminates that the inductance value of the induction heating coil L is a predetermined value regardless of the overcurrent discrimination signal Ip and the power discrimination signal Pp, and the inverter It is determined that the circuit is matched, and the determined content is displayed on the display circuit LD3.

[Embodiment 2]
FIG. 6 is an electrical connection diagram of the electromagnetic induction heating device according to the second embodiment. In the figure, the same reference numerals as those in the electrical connection diagram of the electromagnetic induction heating cooker of the present invention shown in FIG.

  The maximum power setting circuit WG sets a maximum power setting signal Wg.

  The matching / cooking changeover switch SW selects the maximum power setting signal Wg when the matching mode is selected and inputs it to the power control differential amplifier circuit DA1, and selects the power setting signal Wa when the cooking mode is selected. To the differential amplifier circuit DA1.

[Embodiment 3]
FIG. 6 is an electrical connection diagram of the electromagnetic induction heating device according to the third embodiment. In the figure, the same reference numerals as those in the electrical connection diagram of the electromagnetic induction heating cooker of the present invention shown in FIG.

  The matching / mismatch determining circuit KD digitizes the value of the input power calculation signal Po and displays it on the display circuit LD4. It is possible to predict how large or small the inductance value of the induction heating coil L is based on the displayed input power value.

[Embodiment 4]
The operating frequency of the inverter circuit is limited, and a predetermined lower limit value and upper limit value are set. If the matching of the induction heating coil having a very large inductance value is determined under these conditions, the operating frequency of the inverter circuit before the phase difference between the output voltage and output current of the inverter circuit approaches zero and approaches the resonance frequency. In this case, the phase determination signal Cp becomes the Low level. When the power discrimination signal Pp and the phase discrimination signal Cp are at the low level, the matching / mismatch discrimination circuit KD discriminates that the inductance value of the induction heating coil L is a very large value and outputs a mismatch signal. Further, a display circuit (not shown) for displaying the contents of the discriminated mismatch signal may be provided separately.

It is an electrical connection figure of the electromagnetic induction heating cooking appliance of this invention. It is a detailed electrical connection diagram of a current / phase limiting circuit. It is a waveform diagram when the inductance value of the induction heating coil L is too small to obtain the maximum rated electric power, and the output current of the inverter circuit becomes an overcurrent. FIG. 5 is a waveform diagram when the inductance value of the induction heating coil L is too large to obtain the maximum rated electric power, and the leading phase of the output voltage of the inverter circuit is close to zero and close to the resonance frequency. It is a waveform diagram when the inductance value of the induction heating coil L is at a predetermined value, the maximum rated power is obtained, and the induction heating coil is matched with the inverter circuit. It is an electrical connection figure of the electromagnetic induction heating cooking appliance of Embodiment 2 and 3. It is an electrical connection figure of the electromagnetic induction heating cooking appliance of a prior art.

Explanation of symbols

C1 smoothing capacitor C2 resonance capacitor C3 resonance capacitor CP phase discrimination circuit CT1 input current detection circuit CT2 output current detection circuit DC drive circuit DA1 power control differential amplifier circuit DA2 output current limit circuit DA3 phase limit circuit DR1 rectifier circuit FS phase limit setting Circuit IC Current limit setting circuit IP Overcurrent discrimination circuit KD Matching / mismatch discrimination circuit L Induction heating coil LD1 Display circuit LD2 Display circuit LD3 Display circuit LD4 Display circuit LD5 Input power display circuit PF Phase difference detection circuit PP Power discrimination circuit PO Power Arithmetic circuit PT1 input voltage detection circuit SS soft start circuit SW matching / cooking changeover switch TR1 first switching element TR2 second switching element VF V / F converter WA power setting circuit WG maximum power setting circuit Cp phase determination Signal Ct1 Input current detection signal Ct2 Output current detection signal Da1 Power control differential amplification signal Da2 Output current limit signal Da3 Phase limit signal Fs Phase limit setting signal Ic Current limit setting signal Ip Overcurrent determination signal Po Input power calculation signal Pp Power Discrimination signal Pf Phase difference detection signal Pt1 Input voltage detection signal Tr1 First switching element drive signal Tr2 Second switching element drive signal Vf Frequency command signal Wa Power setting signal Wg Maximum power setting signal

Claims (2)

  A resonance capacitor; an induction heating coil that forms a series resonance circuit with the resonance capacitor; an inverter circuit that supplies a high-frequency current to the induction heating coil; a power calculation circuit that calculates an input power value of the inverter circuit; and power setting In an electromagnetic induction heating cooker comprising: a power setting circuit that sets a value to a predetermined value; and a control circuit that controls an output frequency of the inverter circuit so that the input power value becomes the power setting value. A power discriminating circuit that sets a power setting value to a maximum power setting value and outputs a power discriminating signal when the input power value reaches the maximum power setting value, and a current limit value in which the output current of the inverter circuit is predetermined An overcurrent discriminating circuit that discriminates an overcurrent when it is larger and outputs an overcurrent discrimination signal; and an output voltage and an output current of the inverter circuit A phase discrimination circuit that detects a phase difference and outputs a phase discrimination signal when the phase difference is close to zero and approaches a resonance frequency, and the induction heating coil to confirm that it is matched with the inverter circuit When the power setting value is set to the maximum power setting value and the inverter circuit is started, it is determined that the power determination signal is consistent regardless of the overcurrent determination signal and the phase determination signal. When the power determination signal is not output and the overcurrent determination signal is output, it is determined that there is a mismatch due to the inductance value of the induction heating coil being too small, and when the power determination signal is not output and the phase determination signal is output A matching / mismatch determining circuit that outputs a matching / mismatch determining signal by determining that the inductance value of the induction heating coil is too large. , Electromagnetic induction heating cooker is characterized in that a display circuit for displaying the contents of the discrimination signal of the matched-mismatched. The electromagnetic induction heating cooker according to claim 1, further comprising a display circuit for displaying the input power value .

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