JP2003151750A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem wherein food during the cooking is spoiled and should be disposed of when heating during the cooking is often stopped since heating is stopped when a surrounding temperature of an induction heating cooker is too high or when an internal temperature rapidly increases due to clogging by dust and oiling at a cooling wind intake port. SOLUTION: This induction heating cooker supplies to a heating coil L after changing into a high frequency alternating current pulse voltage by an inverter circuit connected by a half bridge. A control process calculation circuit SC for controlling the inverter circuit such that a multiplication process signal Sa value is identical with a value set by a power set circuit PC and a first thermostat TH1 are installed in the vicinity of the heating coil L and when the value reaches a predetermined second temperature increase value T2, power of the inverter circuit is lowered by a variable attenuation circuit OA for restraining the temperature increase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker having a function of determining whether or not the cooker is properly heated.

[0002]

2. Description of the Related Art FIG. 2 is an electrical connection diagram of a conventional induction heating cooker. In FIG. 2, a DC power supply circuit section DCP is formed from a rectifier circuit DR1 that rectifies the output of the commercial AC power supply 1 and converts it into DC power, and a smoothing capacitor C1 that smoothes the power converted into DC by the rectification circuit DR1. There is.

The input current detection circuit ID detects the input current value and outputs the input current detection signal Id, and the input voltage detection circuit IV detects the input voltage value and the input voltage detection signal Iv.
Is output.

The switching element TRA and the switching element TRB form a half-bridge type inverter circuit, and the heating coil L and the resonance capacitor C2 and the resonance capacitor C3 are connected to each other to form a resonance type inverter circuit section INV.
Forming F.

The switching element drive circuit SD modulates the pulse frequency with a constant pulse width ratio in accordance with the value of the control processing operation signal Sc from the control processing operation circuit SC.
ulse Frequency Modulation
Control (hereinafter, PFM control) is performed to alternately supply the switching element drive signal TRa and the switching element drive signal TRb to the half bridge type switching element TRA and switching element TRB.

The multiplication processing circuit SA has an input current detection signal I
d and the input voltage detection signal Iv are multiplied to obtain a multiplication processing signal S
a, the power setting circuit PC outputs the power setting signal Pc, and inputs the power command signal Pa amplified to a predetermined value by the amplifier circuit OP and the second amplifier circuit OP2 to the comparison operation circuit CO. .

The comparison operation circuit CO compares the electric power command signal Pa and the multiplication processing signal Sa and calculates a comparison operation signal ΔI.
The value of is output. The control processing operation circuit SC starts operation by the heating switch TS, performs an operation according to the value of the comparison operation signal ΔI, and reduces the value of the control operation operation signal Sc when the value of the comparison operation signal ΔI is large. Conversely, when the value of the comparison calculation signal ΔI is small, the control processing calculation signal Sc
Increase the value of.

When the value of the control processing operation signal Sc input from the control processing operation circuit SC is small, the switching element drive circuit SD raises the frequency of PFM control to increase the resonance of the heating coil L and the resonance capacitors C2 and C3. The impedance value of the tank is increased to reduce the current flowing through the heating coil L. On the contrary, when the value of the control processing calculation signal Sc is large, the frequency of the PFM control is lowered to reduce the impedance value of the resonance tank and the current flowing to the heating coil L is increased to control the current flowing to the heating coil L. I do.

The first thermostat TH1 and the second thermostat TH2 are connected in series, and the first thermostat TH1 is installed at a predetermined position near the heating coil L to detect the temperature of the heating coil L. The second thermostat TH2 is installed at a predetermined position in the vicinity of the switching element TRB to detect the temperature of the switching element TRB, and one or both of the thermostats have a temperature rise limit value T5 of a predetermined value. When it reaches, the abnormal temperature signal Th is output.

When the abnormal temperature signal Th is input, the temperature protection circuit TP determines that the temperature is abnormal, and outputs the temperature protection signal Tp. When the temperature protection signal Tp is input, the control processing arithmetic circuit SC prohibits the output of the control processing arithmetic signal Sc and stops the output of the inverter circuit.

In the prior art induction heating cooker, the cooling air intake port is clogged with dust, oil stains, etc. (hereinafter referred to as "clogging") to lower the cooling effect. When the temperature in the vicinity of the heating coil rises rapidly and reaches the temperature rise limit value T5 as in the example, the temperature protection circuit TP operates to prohibit the output of the control processing operation signal Sc and also stop the inverter circuit. The temperature rise limit value T5 was prevented from being exceeded.

[0012] To return the induction heating cooker,
The first thermostat TH installed near the heating coil L
After the temperature of 1 and the like was lowered and the temperature protection signal Tp was released, the control circuit arithmetic circuit SC became operable by activating the reset circuit RS, and the induction heating cooker could be restored.

[0013]

Since the induction heating cooker is installed in the kitchen, there are often devices that generate high temperatures in the surroundings, and the ambient temperature of the induction heating cooker becomes very high. As a result, the internal temperature rises sharply, or the cooling air intake port is clogged, which reduces the cooling effect and raises the internal temperature to reach a dangerous temperature, leading to damage. At this time, the temperature protection circuit operates to stop heating and avoid damage to the induction heating cooker. However, if the induction heating cooker suddenly stopped during cooking, the food being cooked was ruined and the food had to be discarded.

[0014]

The invention of the device of claim 1 at the time of filing is, as shown in Embodiment 1 of FIG. 3, a resonance tank formed by an inverter circuit, resonance capacitors C2, C3 and a heating coil L. In the device for controlling the output current by increasing / decreasing the impedance value of the resonance tank by changing the output frequency of the inverter circuit, the inverter circuit is configured so as to have a predetermined value set by the power setting circuit PC. Control processing arithmetic circuit SC for controlling, temperature of heating coil L and switching element TRB
First thermostat TH that indirectly detects the temperature of
The first to fourth thermostats TH4 and the first thermostat TH1 and the second thermostat TH2 are connected in series, and the first thermostat TH1 is installed at a predetermined position in the vicinity of the heating coil L, and the first thermostat TH1 is installed. A thermostat TH2 of No. 2 is installed at a predetermined position near the switching element TRB, and a temperature protection circuit TP that stops the output of the inverter circuit when one or both of the above reaches the temperature increase limit value T5 of a predetermined value. , The third thermostat TH3 and the fourth thermostat TH4
Are connected in series, the third thermostat TH3 is installed at a predetermined position near the heating coil L, the fourth thermostat TH4 is installed at a predetermined position of the switching element TRB, and the third thermostat is installed. TH3
When one or both of the fourth thermostat TH4 and the second temperature increase value T2 reach a predetermined value, the frequency of the inverter circuit is increased to increase the impedance value of the resonance tank and the current flowing through the heating coil L. And a variable attenuation circuit OA for reducing the output of the induction heating cooker.

In the invention of the device as claimed in claim 2 at the time of filing, the variable attenuation circuit OA includes a resistor R1, a resistor R2 and a resistor R.
3, the first analog switch AS1 and the operational amplifier, and the third thermostat TH3 and the fourth
When one or both of the thermostats TH4 of FIG. 3 operate, a second power command signal Pb is output which is obtained by attenuating the value of the power setting signal Pc set by the power setting circuit PC to a predetermined value. It is the induction heating cooker of 1.

The invention of the apparatus of claim 3 at the time of filing has a display lamp LED which lights up and displays when one or both of the third thermostat TH3 and the fourth thermostat TH4 are operated. It is an induction heating cooker.

The invention of the apparatus of claim 4 at the time of application is an apparatus capable of reducing the output in two stages by providing a fifth thermostat TH5 and a sixth thermostat TH6 as shown in the second embodiment of FIG. Therefore, a resonance tank formed of an inverter circuit, resonance capacitors C2 and C3, and a heating coil L is provided, and by changing the output frequency of the inverter circuit, the impedance value of the resonance tank is increased or decreased to control the output current. In the device, a control processing arithmetic circuit SC that controls the inverter circuit so as to have a predetermined value set by the power setting circuit PC, and a temperature that indirectly detects the temperatures of the heating coil L and the switching element TRB. The first thermostat TH1 to the sixth thermostat TH6, and the first thermostat T
H1 and the second thermostat TH2 are connected in series,
The first thermostat TH1 is installed at a predetermined position in the vicinity of the heating coil L, and the second thermostat T1 is installed.
H2 is installed at a predetermined position near the switching element TRB, and a temperature protection circuit TP that stops the output of the inverter circuit when one or both of the above reach the temperature increase limit value T5 of a predetermined value; The third thermostat TH3 and the fourth thermostat TH4 are connected in series, and the fifth thermostat TH5 and the sixth thermostat TH6 are also connected in series to connect the third thermostat TH3 and the fifth thermostat TH5. It is installed at a predetermined position near the heating coil L, and the fourth thermostat TH4 and the sixth thermostat TH6 are installed at predetermined positions of the switching element TRB,
When one or both of the third thermostat TH3 and the fourth thermostat TH4 reach the second temperature rise value T2 which is a predetermined value, the frequency of the inverter circuit is increased to increase the impedance value of the resonance tank. The current flowing through the heating coil L is reduced, and then the temperature rises to increase the temperature of the fifth thermostat TH5 and the sixth thermostat TH.
When one or both of 6 and 6 reach the third temperature rise value T3 which is a predetermined value, the frequency of the inverter circuit is further increased to increase the impedance value of the resonance tank to further reduce the current flowing through the heating coil L. And a two-step variable attenuation circuit OA2 that reduces the output.

In the invention of the device of claim 5 at the time of application, the two-stage variable attenuation circuit OA2 includes a resistor R1, a resistor R2, a resistor R3 and a resistor R4, a first analog switch AS1 and a second analog switch. When one or both of the third thermostat TH3 and the fourth thermostat TH4, which are formed by the switch AS2 and the operational amplifier, operate, the value of the power setting signal Pc set by the power setting circuit PC is set to 1 / When the fifth thermostat TH5 and the sixth thermostat TH6 operate, or both of them are output after being attenuated to 2, the value of the power setting signal Pc having a predetermined value is further attenuated to 1/3. The induction heating cooker according to claim 4, wherein the third electric power command signal Pd is output.

According to the invention of claim 6 at the time of filing, as shown in Example 3 of FIG. 6, the thermostat of the device of claim 4 at the time of filing is replaced with a thermistor, and at the same time, an apparatus capable of reducing the output in three stages is provided. A resonant tank formed by an inverter circuit, resonant capacitors C2, C3, and a heating coil L is provided, and by changing the output frequency of the inverter circuit, the impedance value of the resonant tank is increased or decreased to control the output current. In the device
A control processing arithmetic circuit SC for controlling the inverter circuit so as to have a predetermined value set by the power setting circuit PC;
A first thermistor PCT1 to a third thermistor PCT3 that indirectly detect the temperature of the heating coil L, the temperature of the resonance capacitor C3, and the temperature of the switching element TRB;
The first thermistor PCT1 is installed at a predetermined position near the heating coil L, and the second thermistor PCT2 is installed.
Is installed at a predetermined position near the resonance capacitor C3,
The third thermistor PCT3 is a switching element TR.
A maximum temperature detection protection circuit PTA which is installed at a predetermined position near B and stops the output of the inverter circuit when one or all of the three thermistors reach a predetermined temperature rise limit value T5; The first thermistor PC
T1, second thermistor PCT2 and third thermistor P
When even one of CT3 reaches the second temperature rise value T2 which is a predetermined value, the first analog switch drive signal Ta1
And outputs the second analog switch drive signal Ta2 when the third temperature rise value T3 is reached, and further outputs the third analog switch drive signal Ta3 when the temperature rises to the fourth temperature rise value T4. A temperature detection determination circuit TA for output,
In response to the output signal of the temperature detection / discrimination circuit TA, the frequency of the inverter circuit is increased to increase the impedance value of the resonance tank to reduce the current flowing through the heating coil L,
Three-stage variable attenuation circuit O that reduces the output in three stages
It is an induction heating cooker provided with A3.

In the invention of the device of claim 7 at the time of filing, the three-stage variable attenuation circuit OA3 includes a resistor R1, a resistor R2, a resistor R3 and a resistor R4, a first analog switch AS1 and a second analog switch. The power setting signal Pc formed by the switch AS2, the third analog switch AS3, and the operational amplifier and having a predetermined value set by the power setting circuit PC in accordance with the output signal of the temperature detection determination circuit TA.
7. The induction heating cooker according to claim 6, wherein the fourth electric power command signal Pe is output by attenuating the value of 1/2 to 1/3 or 1/4 in three steps.

The invention of the apparatus of claim 8 at the time of application is an apparatus in which the third thermostat TH3 of the apparatus of claim 1 at the time of application is replaced with a thermistor, as shown in the embodiment 4 of FIG. A resonance tank formed by the resonance capacitors C2 and C3 and the heating coil L, and changing the output frequency of the inverter circuit to increase or decrease the impedance value of the resonance tank to control the output current. A control processing arithmetic circuit SC that controls the inverter circuit so as to have a predetermined value set by the circuit PC, a first thermostat TH1 that indirectly detects the temperature of the heating coil L and the temperature of the switching element TRB, and Second thermostat T
H2, the first thermostat TH1 and the second thermostat TH2 are connected in series, the first thermostat TH1 is installed at a predetermined position near the heating coil L, and the second thermostat TH2 is a switching element. Installed at a predetermined position near the TRB,
Thermostat TH1 and second thermostat TH
A temperature protection circuit TP that stops the output of the inverter circuit when one or both of the two reach a predetermined temperature rise limit value T5, and a first thermistor PCT1 that indirectly detects the temperature of the heating coil L. , The first thermistor PCT1 is installed at a predetermined position near the heating coil L to detect the temperature, and when the detected temperature reaches the second temperature increase value T2, the heating coil temperature detection determination signal Tk is output. When the heating coil temperature detection determination circuit TK that outputs and the heating coil temperature detection determination signal Tk are input, the value of the power setting signal Pc is attenuated to a predetermined value and the second power command signal Pb is output. It is an induction heating cooker provided with the variable attenuation circuit OA which outputs.

The invention of the device of claim 9 at the time of filing is, as shown in the fifth embodiment of FIG. 11, the device of claim 1 at the time of filing, in addition to the fourth thermistor PCT4, the fourth resistance-voltage conversion circuit TC4 and the changeover switch. A device with an additional SW, comprising a resonance tank formed by an inverter circuit, resonance capacitors C2, C3, and a heating coil L, and increasing or decreasing the impedance value of the resonance tank by changing the output frequency of the inverter circuit. In the device for controlling the output current by setting the fourth thermistor PCT4 at a predetermined position inside the pot 2, the temperature change of the pot 2 is converted into a resistance value and detected, and the resistance value is converted into a voltage signal. A fourth resistance-voltage conversion circuit TC4 that converts and outputs the fourth resistance-voltage conversion signal Tc4, the multiplication processing signal Sa, and the fourth resistance-voltage conversion signal Tc4. When the changeover switch SW for changing over and the changeover switch are set to the side a, the inverter circuit is controlled so that the value of the multiplication processing signal Sa becomes a predetermined value set by the power setting circuit PC, and the changeover switch is set to the side b. Then, the control processing arithmetic circuit SC for controlling the inverter circuit so that the value of the fourth resistance voltage conversion signal Tc4 becomes a predetermined value set by the power setting circuit PC, and the heating coil L.
First thermostat TH1 to fourth thermostat TH4 that indirectly detect the temperature of the switching element TRB and the temperature of the switching element TRB, the first thermostat TH1 and the second thermostat TH2 are connected in series, and the first thermostat TH1 and the second thermostat TH2 are connected.
Of the thermostat TH1 is installed at a predetermined position near the heating coil L, and the second thermostat TH2 is installed at a predetermined position near the switching element TRB.
A temperature protection circuit TP that stops the output of the inverter circuit when one or both of the first thermostat TH1 and the second thermostat TH2 reach a temperature increase limit value T5 of a predetermined value, and the third thermostat T2.
H3 and the fourth thermostat TH4 are connected in series,
The third thermostat TH3 is installed at a predetermined position in the vicinity of the heating coil L, and the fourth thermostat T3 is installed.
H4 is installed at a predetermined position of the switching element TRB, and when one or both of the third thermostat TH3 and the fourth thermostat TH4 reaches the predetermined second temperature increase value T2, the power setting is performed. The induction heating cooker includes a variable attenuation circuit OA that attenuates the value of the signal Pc to a predetermined value and outputs the second power command signal Pb.

At the time of filing, the invention of the apparatus of claim 10 is shown in FIG.
As shown in the sixth embodiment of the present invention, a resonance tank formed by an inverter circuit, resonance capacitors C2 and C3, and a heating coil L is provided, and the impedance value of the resonance tank is increased or decreased by changing the output frequency of the inverter circuit. In an apparatus for controlling output current by a power setting circuit PC, a power setting circuit PC that outputs a power setting signal Pc having a predetermined value by a power setting circuit PC, and a power command by amplifying the value of the power setting signal Pc to a predetermined value. Amplification circuits OP and OP2 that output a signal Pa, a comparison calculation circuit CO that performs a comparison calculation of the multiplication processing signal Sa and the power command signal Pa and outputs a comparison calculation signal ΔI, and a value of the comparison calculation signal ΔI. Control processing arithmetic circuit SC for controlling the inverter circuit by means of temperature, heating coil L temperature and switching element TRB
First thermistor PCT1 that indirectly detects the temperature of the
And a third thermistor PCT3 and the first thermistor PCT1 are installed at a predetermined position near the heating coil L, and the third thermistor PCT3 is installed at a predetermined position near the switching element TRB. A second maximum temperature detection protection circuit PTA2 that stops the output of the inverter circuit when one or both of the two thermistors reaches a predetermined temperature rise limit value T5 and a resistance value of the first thermistor signal PCt1 are set. First converted to voltage signal
Of the first resistance-voltage conversion circuit TC1 that outputs the resistance-voltage conversion signal Tc1 and the resistance value of the third thermistor signal PCt3 are converted into voltage signals to generate the third resistance-voltage conversion signal Tc3.
Of the third resistance-voltage conversion circuit TC3, which outputs the first temperature reference value setting signal Pt1 and the first resistance-voltage conversion signal Tc.
The second comparison calculation circuit CO2 which compares and calculates 1 and outputs the second comparison calculation signal ΔI2 when Pt1 <Tc1.
And a second temperature reference value setting signal Pt2 and a third resistance voltage conversion signal Tc3 are compared and calculated, and when Pt2 <Tc3, a third comparison calculation circuit CO3 that outputs a third comparison calculation signal ΔI3. And a signal whose comparison operation signal ΔI1 to comparison operation signal ΔI3 has a large value is selected, and the control processing operation circuit S
Diode D formed in the OR circuit for input to C
The induction heating cooker reduces the output of the inverter circuit when 1 to D3 and the comparison calculation signal ΔI2 or the comparison calculation signal ΔI3 are selected.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram best representing the features of the invention according to the application. Since it is the same as FIG. 3 described later, the description will be described later with reference to FIG.

The embodiment of the present invention is the invention of the device of claim 1 at the time of filing as shown in the first embodiment of FIG. 3, which is formed by an inverter circuit, resonant capacitors C2, C3 and a heating coil L. In a device that includes a resonance tank and changes the output frequency of the inverter circuit to increase or decrease the impedance value of the resonance tank to control the output current, a predetermined value set by the power setting circuit PC is set. A control processing arithmetic circuit SC for controlling the inverter circuit, first to fourth thermostats TH1 to TH4 for indirectly detecting the temperature of the heating coil L and the temperature of the switching element TRB, and the first thermostat TH1 and Second thermostat T
By connecting H2 in series, the first thermostat TH
1 is installed at a predetermined position near the heating coil L, and the second thermostat TH2 is connected to the switching element TRB.
A temperature protection circuit TP that is installed in a predetermined position in the vicinity and that stops the output of the inverter circuit when one or both of the above reach the temperature increase limit value T5 of a predetermined value, and the third thermostat TH3 and The fourth thermostat TH4 is connected in series, and the third thermostat T
H3 is installed at a predetermined position near the heating coil L, and the fourth thermostat TH4 is connected to the switching element TR.
It is installed at a predetermined position of B, and when one or both of the above reach a second temperature rise value T2 of a predetermined value, the frequency of the inverter circuit is increased to increase the impedance value of the resonance tank and heat it. The induction heating cooker includes a variable attenuation circuit OA that reduces the output by reducing the current flowing through the coil L.

[0026]

FIG. 3 is an electric connection diagram of an induction heating cooker showing a first embodiment of the present invention. In FIG. 3, the same reference numerals as those in the electrical connection diagram of the conventional induction heating cooker shown in FIG. 2 perform the same operations, and therefore the description thereof will be omitted and different operations will be described.

The third thermostat TH3 and the fourth thermostat TH4 are connected in series, and those which operate at a predetermined lower temperature than the first thermostat TH1 and the second thermostat TH2 are selected, and the third thermostat TH3 and the third thermostat TH2 are selected.
The thermostat TH3 is installed at a predetermined position near the heating coil L to detect the temperature of the heating coil L, and the fourth thermostat TH4 is a switching element TR.
The switching element TRB installed at a predetermined position of B
Temperature of the third thermostat TH3 and the fourth
When one or both of the thermostats TH4 reach the predetermined second temperature increase value T2, the temperature detection signal Ta is output. Further, when the third thermostat TH3 and the fourth thermostat TH4 become lower than the second temperature rise value T2 and reach a temperature of a predetermined value, the temperature detection signal Ta
It operates with the hysteresis characteristic of releasing.

The third thermostat TH3 and the fourth thermostat
Of the thermostat TH4 is lower than the second temperature rise value T2 of a predetermined value, the temperature detection signal Ta is High.
It becomes level, and conversely, when one or both are high, L
It becomes ow level. The first inversion circuit IN1 inverts the temperature detection signal Ta and inputs it to the first analog switch AS1. In the indicator LED, the temperature detection signal Ta is Low.
Lights at level.

The variable attenuator circuit OA is formed of a resistor R1, a resistor R2, a resistor R3, a first analog switch AS1 and an operational amplifier. The variable attenuator circuit OA operates as an inverting attenuator circuit, and the analog switch A
When S1 becomes conductive, the resistor R3 and the resistor R1 are connected in parallel and attenuated to half the normal amplification factor. OP2
Is a second amplifier circuit for inverting and amplifying a gain of 1 and outputs a second power command signal Pb.

FIG. 4 is a diagram showing temperature characteristics at a predetermined position near the heating coil. First, referring to FIG.
The operation of this embodiment will be described.

When the heating switch TS is activated, the induction heating cooker starts heating according to the value of the power setting signal Pc of the power setting circuit PC. When the heating is normal, the temperature in the vicinity of the heating coil is as shown in FIG. As shown, the temperature is controlled within the normal temperature range.

When the temperature around the induction heating cooker rises or an abnormality such as clogging occurs in the cooling air inlet and the cooling effect decreases, for example, the heating coil of the induction heating cooker shown in FIG. The temperature near the position where the thermostat is installed near L sharply rises.

When the temperature near the heating coil L rises and becomes higher than the second temperature rise value T2, the third thermostat TH3 determines that the temperature is higher than the second temperature rise value T2, Temperature detection signal Ta at time t = t1
Is changed from High level to Low level. The first inversion circuit IN1 inverts the signal Ta to make the first analog switch AS1 conductive. Further, the indicator lamp LED is turned on to indicate that the lamp is being used within the temperature limit range.

When the first analog switch AS1 is turned on, the variable attenuator circuit OA outputs a second power command signal Pb whose amplification factor is attenuated to 1/2 of that in normal use. The comparison operation circuit CO uses the second power command signal Pb and the multiplication processing signal S.
The value of the comparison operation signal ΔI is output by performing a comparison operation with a. At this time, the value of the comparison calculation signal ΔI increases and the value of the control processing calculation signal Sc decreases.

In the switching element drive circuit SD, when the value of the control processing operation signal Sc becomes smaller, the frequency of PFM control is increased to increase the impedance value of the resonance tank and the current value flowing in the heating coil L is decreased, as shown in FIG. The temperature rise after time t = t1 shown in is suppressed. As described above, when the temperature in the vicinity of the heating coil L further rises and becomes higher than the temperature rise limit value T5, the temperature protection circuit TP operates and sets the temperature protection signal Tp to the High level. When the temperature protection signal Tp becomes High level, the control processing operation circuit SC determines that the temperature is dangerous and stops the operation. Further, in order to return the induction heating cooker, the first thermostat TH1 and the switching element TR installed near the heating coil L are used.
When the temperature of both the second thermostat TH2 installed at a predetermined position near B becomes lower than the temperature rise limit value T5 and becomes lower than the predetermined protection release temperature T6, the temperature protection signal Tp is released and the reset circuit RS By activating, the control processing arithmetic circuit SC becomes operable and the induction heating cooker is restored.

FIG. 5 is an electrical connection diagram of an induction heating cooker showing a second embodiment of the present invention. In FIG. 5, the same symbols as those in the electrical connection diagram of the conventional induction heating cooker shown in FIG. 2 perform the same operation, so the description thereof will be omitted and a different operation will be described.

Third thermostat TH3, fourth thermostat TH4, and fifth thermostat TH5
And a sixth thermostat TH6 are connected in series, and the fifth thermostat TH5 and the sixth thermostat TH6 are selected to operate at a predetermined lower temperature than the first thermostat TH1 and the second thermostat TH2. In addition, the third thermostat TH
As the third and fourth thermostats TH4, those which operate at a predetermined lower temperature than those of the fifth thermostat TH5 and the sixth thermostat TH6 are selected and used.
The third thermostat TH3 and the fifth thermostat TH5 are installed at predetermined positions near the heating coil L to detect the temperature of the heating coil L, and the fourth thermostat TH4 and the sixth thermostat TH6 are The switching element TRB is installed at a predetermined position to detect the temperature of the switching element TRB, and one or both of the third thermostat TH3 and the fourth thermostat TH4 reaches a predetermined second temperature rise value T2. Then, the temperature detection signal Ta is output, and when the third thermostat TH3 and the fourth thermostat TH4 fall below the second temperature increase value T2 and reach a temperature of a predetermined value, the temperature detection signal Ta is released. However, one or both of the fifth thermostat TH5 and the sixth thermostat TH6 has a predetermined number. Reaching the temperature rise value T3 when the second
When the fifth thermostat TH5 and the sixth thermostat TH6 have become lower than the third temperature increase value T3 and reach a temperature of a predetermined value, the second temperature detection signal Tb It operates with a hysteresis characteristic that releases Tb.

In the third thermostat TH3 and the fourth thermostat TH4, the temperature detection signal Ta becomes the High level when it is lower than the second temperature rise value T2 which is a predetermined value, and vice versa. Sometimes it becomes Low level. The first inversion circuit IN1 has a temperature detection signal Ta.
Is inverted and input to the first analog switch AS1.
Further, the fifth thermostat TH5 and the sixth thermostat TH6 have the third temperature increase value T of a predetermined value.
When it is lower than 3, the temperature detection signal Ta becomes High level, and conversely, when one or both are high, it becomes Low level. The second inverting circuit IN2 receives the second temperature detection signal T
b is inverted and input to the second analog switch AS2. The indicator light LED lights up when the temperature detection signal Tb is at the low level.

The two-stage variable attenuation circuit OA2 includes a resistor R
1, a resistor R2, resistors R3 and R4, a first analog switch AS1, a second analog switch AS2, and an operational amplifier. The two-stage variable attenuator OA2 operates as an inverting amplifier circuit, and when the analog switch AS1 is turned on, the resistor R3 and the resistor R1 are connected in parallel and attenuated to half the normal amplification factor. Further, when the analog switch AS1 and the analog switch AS2 are simultaneously turned on, the resistors R3 and R4 are connected.
And the resistor R1 are connected in parallel, and have a normal amplification factor of 1
Decays to / 3.

FIG. 4 is a diagram showing temperature characteristics at a predetermined position in the vicinity of the same heating coil as that of [0031] as described above. The operation of the second embodiment will be described with reference to FIG. When the heating switch TS is activated, the induction heating cooker starts heating according to the value of the power setting signal Pc of the power setting circuit PC, and when the heating is normal, the temperature near the heating coil is as shown in FIG. , The temperature is controlled within the normal temperature range.

If an abnormality such as clogging occurs at the cooling air inlet of the induction heating cooker and the cooling effect decreases, for example, as shown in FIG.
The temperature at the position where the thermostat is installed near the heating coil L of the induction heating cooker shown in FIG.

As the temperature in the vicinity of the heating coil L rises, as shown in FIG.
As shown in, when the temperature rises above the second temperature rise value T2, the third thermostat TH3 determines that the temperature is higher than the second temperature rise value T2, and at time t = t1, the temperature detection signal is detected. Ta changes from the High level to the Low level, the first inversion circuit IN1 shown in FIG. 5 inverts the temperature detection signal Ta, and the first analog switch A
Conduct S1. Further, at time t = t2, when it becomes higher than the third temperature rise value T3, the fifth thermostat TH5 determines that the temperature is higher than the third temperature rise value T3, and the second analog switch As shown in FIG. 4, the indicator light LED is lit while AS2 is conducted.
Indicates that the product is being used within the operating temperature limit range.

The two-stage variable attenuator circuit OA2 has an amplification factor of 1 when the first analog switch AS1 is turned on.
/ 2 and the value of the third power command signal Pd also becomes 1/2. Further, when the second analog switch AS2 also conducts, the value of the third power command signal Pd further decreases and becomes 1/3.
become. The comparison operation circuit CO uses the third power command signal Pd.
And the multiplication processing signal Sa are compared and calculated, and a comparison calculation signal Δ
Output the value of I. At this time, the value of the comparison calculation signal ΔI increases as the value of the third power command signal Pd decreases, and the value of the control processing calculation signal Sc decreases.

In the switching element drive circuit SD, when the value of the control processing operation signal Sc from the control processing operation circuit SC is small, the PFM control frequency is increased to increase the impedance value of the resonance tank and the current flowing through the heating coil L. By decreasing the value, the temperature rise after time t = t1 shown in FIG. 4 is suppressed, and after time t = t2, the current value flowing through the heating coil L is further reduced to suppress the temperature rise. Even when the temperature rise cannot be suppressed and the temperature in the vicinity of the heating coil L rises above the temperature rise limit value T5, the temperature protection circuit TP operates to set the temperature protection signal Tp to H.
Output at high level. When the temperature protection signal Tp becomes High level, the control processing operation circuit SC determines that the temperature is dangerous and stops the output of the inverter circuit. Moreover, in order to return the induction heating cooker, the temperature of both the first thermostat TH1 installed near the heating coil L and the second thermostat TH2 installed at a predetermined position near the switching element TRB is the temperature rise limit value. When it becomes lower than T5 and becomes lower than the predetermined protection release temperature T6, the temperature protection signal Tp is released, and by activating the reset circuit RS, the control processing operation circuit SC becomes operable and the induction heating cooker is restored.

FIG. 6 is an electrical connection diagram of an induction heating cooker showing a third embodiment of the present invention. In FIG. 6, the same symbols as those in the electrical connection diagram of the conventional induction heating cooker shown in FIG. 2 perform the same operation, so the description thereof will be omitted and a different operation will be described.

The first thermistor PCT1 is installed at a predetermined position near the heating coil L, detects the temperature of the heating coil L, converts the detected temperature into a resistance value, and outputs the first thermistor signal PCt1. Output the second thermistor P
The CT2 is installed at a predetermined position near the resonance capacitor C3, detects the temperature of the resonance capacitor C3, converts the detected temperature into a resistance value, and outputs the second thermistor signal PC.
The third thermistor PCT3 outputs t2, is installed at a predetermined position near the switching element TRB, detects the temperature of the switching element TRB, converts the detected temperature into a resistance value, and outputs the third thermistor signal PCt3. Is output.

The first resistance-voltage conversion circuit TC1 converts the resistance value of the first thermistor signal PCt1 into a voltage signal and outputs the first resistance-voltage conversion signal Tc1. The second resistance-voltage conversion circuit TC2 outputs the first resistance-voltage conversion circuit TC2. , The second resistance-voltage conversion signal T by converting the resistance value of the second thermistor signal PCt2 into a voltage signal.
c2 is output, and the third resistance voltage conversion circuit TC3 outputs the third voltage
The resistance value of the thermistor signal PCt3 is converted into a voltage signal and the third resistance-voltage conversion signal Tc3 is output.

The maximum temperature detection protection circuit PTA includes a first comparison circuit CP1, a second comparison circuit CP2, a third comparison circuit CP3, and a first temperature reference circuit, as shown in the detailed electrical connection diagram of FIG. It is formed by TR1, the second temperature reference circuit TR2, the third temperature reference circuit TR3, and the first OR circuit OR1.

As shown in the detailed electrical connection diagram of FIG. 8, the temperature detection determination circuit TA includes a fourth comparison circuit CP4, a fifth comparison circuit CP5, a sixth comparison circuit CP6 and a fourth temperature reference circuit TR4. , Fifth temperature reference circuit TR5, sixth temperature reference circuit TR6, second OR circuit OR2 and seventh comparison circuit CP7, eighth comparison circuit CP8, ninth comparison circuit CP9, seventh temperature reference The circuit TR7, the eighth temperature reference circuit TR8, the ninth temperature reference circuit TR9, the third OR circuit OR3, the tenth comparison circuit CP10, the eleventh comparison circuit CP11, the twelfth comparison circuit CP12, and the tenth comparison circuit CP12. Temperature reference circuit TR10, eleventh temperature reference circuit TR1
It is formed by the first and twelfth temperature reference circuits TR12 and the fourth OR circuit OR4. The fourth to twelfth comparison circuits CP4 to CP12 have hysteresis characteristics of a predetermined value.

The third variable attenuation circuit OA3 shown in FIG.
Resistors R1 to R5, first analog switch A
It is formed by S1, the second analog switch AS2, the third analog switch AS3 and the operational amplifier. The third variable attenuator circuit OA3 operates as an inverting amplifier circuit, and when the analog switch AS1 is turned on, the resistor R3 and the resistor R1 are connected in parallel and attenuated to half the normal amplification factor. In addition, analog switch AS
1, analog switch AS2 and analog switch AS
When 3 sequentially conducts simultaneously at the same time, the resistor R3, the resistor R4, the resistor R5 and the resistor R1 are sequentially connected in parallel and attenuated to 1/3 and 1/4 of the normal amplification factor.

FIG. 9 is a diagram showing temperature characteristics at predetermined positions near the heating coil. Using FIG. 9 above, FIG.
The operation of the third embodiment will be described. When the heating switch TS of the induction heating cooker is activated, heating is started according to the value of the power setting signal Pc of the power setting circuit PC, and when the heating is normal, the temperature at a predetermined position near the heating coil is shown. 9
The temperature is controlled within the normal temperature range shown in. However, if an abnormality such as clogging occurs in the cooling air intake port of the induction heating cooker, the cooling effect decreases and the temperature of the first thermistor PCT1 installed near the heating coil L rises sharply. Further, the temperatures of the second thermistor PCT2 near the resonance capacitor C3 (not shown) and the temperature of the third thermistor PCT3 near the switching element TRB also increase rapidly.

The temperature in the vicinity of the heating coil L, which has risen sharply, is measured by the first thermistor PCT1 and the measured value is converted into a voltage signal.
1 is output, the temperature in the vicinity of the resonance capacitor C is measured by the second thermistor PCT2, the second resistance-voltage conversion signal Tc2 obtained by converting the measured value into a voltage signal is output, and the temperature in the vicinity of the switching element TRB is output. The third resistance thermistor PCT3 is used for measurement, and the third resistance-voltage conversion signal Tc3 obtained by converting the measured value into a voltage signal is output. The output signals are input to the temperature detection determination circuit TA and the maximum temperature detection protection circuit PTA.

To explain the operation of the temperature detection / discrimination circuit TA,
The temperature rise near the heating coil L is selected, and the above-mentioned actual example will be described as a representative example. Further, regarding the temperature rise in the vicinity of the resonance capacitor C3 and the temperature rise in the vicinity of the switching element TRB, the same operations as those in the above-described representative example are performed, and thus the description thereof is omitted. As shown in FIG. 8 described above, the sixth comparison circuit CP
6, ninth comparison circuit CP9 and twelfth comparison circuit CP1
When the first resistance voltage conversion signal Tc1 is input to 2, each comparison circuit compares it with each preset reference value, and when the value of the first resistance voltage conversion signal Tc1 is smaller than each reference value, All of the first analog switch drive signal Ta1 to the third analog switch drive signal Ta3 become Low level. Furthermore, the temperature near the heating coil L rises,
When it becomes higher than the second temperature rise value T2 shown in FIG. 9,
The value of the first resistance-voltage conversion signal Tc1 becomes larger than that of the twelfth temperature reference signal Tr12 having the predetermined value set by the twelfth temperature reference circuit TR12, and the temperature detection determination circuit TA has the above-mentioned second value. When it is determined that the temperature is higher than the temperature increase value T2, at time t = t1, the first analog switch drive signal Ta1 is set to the High level to make the first analog switch AS1 conductive. Further, when the temperature in the vicinity of the heating coil L rises and becomes higher than the third temperature rise value T3 at the time t = t2, the temperature of the predetermined value set by the ninth temperature reference circuit TR9 in FIG. The value of the first resistance voltage conversion signal Tc1 becomes larger than that of the temperature reference signal Tr9 of No. 9, and the second analog switch drive signal Ta2 is changed to High at time t = t2.
The second analog switch AS2 is made conductive by setting it to the level. As described above, when the temperature in the vicinity of the heating coil L further rises and becomes higher than the fourth rise temperature T4 at time t = t3, the third analog switch drive signal Ta3 is set to H.
The third analog switch AS3 is made conductive by setting it to the high level.

The third variable attenuation circuit OA3 shown in FIG.
When the first analog switch AS1 is turned on, the amplification factor becomes 1/2 of the normal state and the value of the fourth power command signal Pe is also 1.
/ 2. In addition, when the second analog switch AS2 and the third analog switch AS3 are sequentially turned on, the fourth analog switch AS2 is turned on.
The value of the power command signal Pe is further reduced to 1/3 and 1
It becomes / 4. The comparison operation circuit CO compares the fourth power command signal Pe and the multiplication processing signal Sa, and outputs the value of the comparison operation signal ΔI. At this time, the value of the comparison calculation signal ΔI increases as the value of the fourth power command signal Pe decreases, and the value of the control processing calculation signal Sc decreases.

In the switching element drive circuit SD, when the value of the control processing operation signal Sc from the control processing operation circuit SC is small, the PFM control frequency is increased to increase the impedance value of the resonance tank and the current flowing through the heating coil L. The value is reduced to suppress the temperature rise after time t = t1 shown in FIG. 9, and further, the current value flowing through the heating coil L is reduced in three stages in the order of time t = t2 and time t = t3. Suppress the temperature rise.

Even if the temperature rise cannot be suppressed even above, and the temperature in the vicinity of the heating coil L further rises and becomes higher than the temperature rise limit value T5 as shown in FIG. 9, the maximum temperature detection protection circuit PTA is activated. Maximum temperature detection protection signal P operating
Set Ta to high level. When the maximum temperature detection protection signal PTa becomes High level, the control processing arithmetic circuit SC determines that the temperature is abnormal and stops the output of the inverter circuit.
Also, in order to return the induction heating cooker, the heating coil L
The temperature of the first thermistor PCT1 installed in the vicinity falls below the temperature increase limit value T5 and the predetermined protection release temperature T
When it becomes lower than 6, the temperature protection signal Tp is released, and by activating the reset circuit RS, the control processing operation circuit SC becomes operable and the induction heating cooker is restored.

FIG. 10 is an electrical connection diagram of an induction heating cooker showing a fourth embodiment of the present invention. In FIG. 10, the same symbols as those in the electrical connection diagram of the induction heating cooker of the first embodiment shown in FIG. 3 perform the same operation, so the description thereof will be omitted and different operation will be described.

The fourth embodiment of the present invention is an apparatus in which the third thermostat TH3 and the fourth thermostat TH4 of the above-mentioned first embodiment are replaced with the first thermistor PCT1.

The first thermistor PCT1 is installed at a predetermined position near the heating coil L, detects a temperature change of the heating coil L, converts the temperature change of the heating coil L into a resistance value, and converts the temperature change into a resistance value. The thermistor signal PCt1 is output. The first resistance-voltage conversion circuit TC1 converts the resistance value of the first thermistor signal PCt1 into a voltage signal and outputs the first resistance-voltage conversion signal Tc1.

The heating coil temperature detection determination circuit TK compares the first resistance voltage conversion signal Tc1 with a predetermined temperature reference value (not shown) and compares the first resistance voltage conversion signal Tc.
When the value of 1 becomes larger than the predetermined temperature reference value, it is determined that the temperature is higher than the second temperature increase value T2, and the heating coil temperature detection determination signal Tk is set to High level,
The first analog switch AS1 is turned on. Further, when the temperature becomes lower than the second temperature increase value T2 and reaches a temperature of a predetermined value, the heating coil temperature detection determination signal T
k is set to the Low level and the first analog switch AS1
It has a hysteresis characteristic that shuts off.

In the variable attenuator circuit OA, when the first analog switch AS1 is turned on, the amplification factor becomes 1/2 of the normal state and the value of the second power command signal Pb also becomes 1/2 of the normal state to raise the temperature. Suppress. Even if the temperature rise cannot be suppressed even above, and the temperature in the vicinity of the heating coil L rises and becomes higher than the temperature rise limit value T5, the temperature protection circuit TP operates to set the temperature protection signal Tp to the high level. . When the temperature protection signal Tp becomes High level, the control processing operation circuit SC determines that the temperature is dangerous and stops the operation. Also,
In order to return the induction heating cooker, the temperatures of both the first thermostat TH1 installed near the heating coil L and the second thermostat TH2 installed at a predetermined position near the switching element TRB are higher than the temperature increase limit value T5. When the temperature is lowered and becomes lower than the predetermined protection release temperature T6, the temperature protection signal Tp is released, and the reset processing circuit RS is activated, so that the control processing operation circuit SC becomes operable and the induction heating cooker is restored.

FIG. 11 is an electrical connection diagram of an induction heating cooker showing a fifth embodiment of the present invention. 11, the same symbols as those in the electrical connection diagram of the induction heating cooker of the first embodiment shown in FIG. 3 perform the same operation, and therefore the description thereof will be omitted and different operation will be described.

The fifth embodiment of the present invention is an apparatus in which a fourth thermistor PCT4, a fourth resistance voltage conversion circuit TC4 and a changeover switch SW are added to the above-mentioned first embodiment. When the changeover switch SW is on the side a, the operation is the same as that of the first embodiment, so the description thereof is omitted and the operation when the switch SW is on the side b will be described.

The fourth thermistor PCT4 is installed at a predetermined position inside the pot 2 to detect a temperature change of the internal temperature of the pot 2 and converts the temperature change into a resistance value to generate a fourth thermistor signal. Output PCt4. The fourth resistance-voltage conversion circuit TC4 converts the resistance value of the fourth thermistor signal PCt4 into a voltage signal to generate a fourth resistance-voltage conversion signal Tc4.
Is output.

The comparison operation circuit CO compares the second power command signal Pb and the fourth resistance voltage conversion signal Tc4 and outputs the value of the comparison operation signal ΔI. At this time, the value of the comparison calculation signal ΔI changes according to the temperature change of the pan 2.
Since the output of the inverter circuit of the control processing operation circuit SC is controlled according to the value of the comparison operation signal ΔI, the internal temperature of the pan 2 can be set to a temperature of a predetermined value set by the power setting circuit PC. It will be possible. If the temperature rise cannot be suppressed for some reason and the temperature in the vicinity of the heating coil L rises and becomes higher than the temperature rise limit value T5, the temperature protection circuit TP operates and sets the temperature protection signal Tp to the high level. In the control processing arithmetic circuit SC, the temperature protection signal Tp is Hi.
When it reaches the gh level, it is judged to be a dangerous temperature and the operation is stopped. Moreover, in order to return the induction heating cooker, the temperature of both the first thermostat TH1 installed near the heating coil L and the second thermostat TH2 installed at a predetermined position near the switching element TRB is the temperature rise limit value. When it becomes lower than T5 and becomes lower than the predetermined protection release temperature T6, the temperature protection signal Tp is released, and by activating the reset circuit RS, the control processing operation circuit SC becomes operable and the induction heating cooker is restored.

FIG. 12 is an electrical connection diagram of an induction heating cooker showing a sixth embodiment of the present invention. In FIG. 12, the same symbols as those in the electrical connection diagram of the conventional induction heating cooker shown in FIG. 2 perform the same operation, so the description thereof will be omitted and different operation will be described.

The first thermistor PCT1 is a heating coil L
The temperature change of the heating coil L is detected by being installed at a predetermined position in the vicinity, the temperature change is converted into a resistance value, and a first thermistor signal PCt1 is output to output a third thermistor PC.
T3 is installed at a predetermined position near the switching element TRB to detect the temperature change of the switching element TRB,
The temperature change is converted into a resistance value and the third thermistor signal PCt3 is output.

The first resistance-voltage conversion circuit TC1 converts the resistance value of the first thermistor signal PCt1 into a voltage signal and outputs the first resistance-voltage conversion signal Tc1, and the third resistance-voltage conversion circuit TC3. , A third resistance-voltage conversion signal T by converting the resistance value of the third thermistor signal PCt3 into a voltage signal.
Output c3.

The second maximum temperature detection protection circuit PTA2 is
First comparison circuit CP1 and third comparison circuit CP not shown
3, first temperature reference circuit TR1, third temperature reference circuit T
It is formed by R3 and the first OR circuit OR1.

The first temperature reference value setting circuit PT1 outputs the first temperature reference value setting signal Pt1 having a predetermined value for suppressing the temperature rise of the heating coil L, and the second temperature reference value setting circuit PT1. The circuit PT2 outputs the second temperature reference value setting signal Pt2 having a predetermined value for suppressing the temperature rise of the switching element TRB.

The second comparison operation circuit CO2 has a first temperature reference value setting signal Pt1 and a first resistance voltage conversion signal Tc1.
Is compared and the second comparison calculation signal ΔI2 is output when Pt1 <Tc1. Also, the third comparison operation circuit C
O3 compares and calculates the second temperature reference value setting signal Pt2 and the third resistance voltage conversion signal Tc3, and Pt2 <Tc3
At this time, the third comparison operation signal ΔI3 is output.

An OR circuit is formed by the diodes D1 to D3, and the signal having the largest value is selected from the comparison operation signals ΔI1 to ΔI3 and input to the control processing operation circuit SC.

When an abnormality such as clogging occurs in the cooling air intake port of the induction heating cooker, the cooling effect decreases and the temperature of the first thermistor PCT1 installed near the heating coil L rises sharply. Further, the temperature of the third thermistor PCT3 near the switching element TRB also sharply rises.

The temperature near the heating coil L, which has risen sharply, is measured by the first thermistor PCT1, and the measured temperature is converted into a voltage signal to convert the first resistance-voltage conversion signal T.
c1 is output, the temperature near the switching element TRB is measured by the third thermistor PCT3, the measured temperature is converted into a voltage signal, and the third resistance-voltage conversion signal Tc is output.
3 is output.

From the above, the first resistance voltage conversion signal Tc1
Becomes larger than the first temperature reference value setting signal Pt1, the second comparison operation circuit CO2 causes the second comparison operation signal ΔI.
2 and outputs the control processing arithmetic circuit S through the diode D2.
Input to C. Further, the comparison calculation signal ΔI is the diode D
It is input to the control processing arithmetic circuit SC through 1
When the value of the comparison calculation signal ΔI2 is larger than the second
The value of the comparison calculation signal ΔI2 is selected and input to the control processing calculation circuit SC.

The control processing operation circuit SC has a large second value.
When the comparison calculation signal ΔI2 is input, the value of the control processing calculation signal Sc decreases, the frequency of PFM control increases according to the value of the control processing calculation signal Sc, and the impedance value of the resonance tank also increases due to the high frequency. It becomes larger and the current flowing through the heating coil L becomes smaller. By reducing the current of the heating coil L, it is possible to prevent the temperature of the heating coil L from rising.

[0077]

According to the present invention, the temperature around the induction heating cooker rises, or the cooling air inlet has dust.
The cooling effect decreases due to clogging due to oil stains,
When the internal temperature rises abruptly, it is possible to reduce the output by suppressing the output before an abnormal stop occurs.The induction heating cooker suddenly stops during cooking and the pot temperature changes. It can prevent you from falling and ruining the food you are cooking.

[Brief description of drawings]

FIG. 1 is a diagram best representing the features of the invention according to the application.

FIG. 2 is an electrical connection diagram of a conventional induction heating cooker.

FIG. 3 is an electrical connection diagram of the induction heating cooker showing the first embodiment of the present invention.

FIG. 4 is a temperature characteristic diagram during operation at a predetermined position near the heating coil.

FIG. 5 is an electrical connection diagram of an induction heating cooker showing a second embodiment of the present invention.

FIG. 6 is an electrical connection diagram of an induction heating cooker showing a third embodiment of the present invention.

FIG. 7 is a detailed electrical connection diagram of the maximum temperature detection protection circuit PTA shown in FIG.

FIG. 8 is a detailed electrical connection diagram of the temperature detection determination circuit TA shown in FIG.

FIG. 9 is a temperature characteristic diagram of a predetermined position near the heating coil according to the third embodiment of the present invention.

FIG. 10 is an electrical connection diagram of an induction heating cooker showing a fourth embodiment of the present invention.

FIG. 11 is an electrical connection diagram of an induction heating cooker showing a fifth embodiment of the present invention.

FIG. 12 is an electrical connection diagram of an induction heating cooker showing a sixth embodiment of the present invention.

[Explanation of symbols]

1 Commercial AC power supply 2 pots 3 top plate AS1 first analog switch AS2 second analog switch AS3 Third analog switch CO comparison operation circuit CO2 second comparison operation circuit CO3 Third comparison operation circuit C1 smoothing capacitor C2 resonance capacitor CP1 First comparison circuit CP2 Second comparison circuit CP3 Third comparison circuit CP4 Fourth comparison circuit CP5 Fifth comparison circuit CP6 Sixth comparison circuit CP7 Seventh comparison circuit CP8 Eighth comparison circuit CP9 Ninth comparison circuit CP10 Tenth Comparison Circuit CP11 Eleventh comparison circuit CP12 Twelfth comparison circuit D1 diode D2 diode D3 diode DCP DC power supply circuit DR1 rectifier circuit ID input current detection circuit IV input voltage detection circuit IN1 First inversion circuit IN2 Second inversion circuit INVF resonance type inverter circuit L heating coil LED indicator light OA variable attenuation circuit OA2 two-stage variable attenuation circuit OA3 three-stage variable attenuation circuit OP amplifier circuit OP2 Second amplifier circuit OR1 First OR circuit OR2 Second OR circuit OR3 Third OR circuit OR4 Fourth OR circuit PC power setting circuit PT1 First temperature reference value setting circuit PT2 Second temperature reference value setting circuit PCT1 first thermistor PCT2 second thermistor PCT3 Third Thermistor PCT4 Fourth Thermistor PTA maximum temperature detection protection circuit PTA2 Second maximum temperature detection protection circuit R1 resistor R2 resistor R3 resistor R4 resistor R5 resistor SA multiplication processing circuit SC control processing arithmetic circuit SD switching element drive circuit SW selector switch TA temperature detection discrimination circuit TK Heating coil temperature detection discrimination circuit TP temperature protection circuit TS heating switch TC1 first resistance voltage conversion circuit TC2 Second resistance voltage conversion circuit TC3 Third resistance voltage conversion circuit TC4 Fourth resistance-voltage conversion circuit TH1 first thermostat TH2 second thermostat TH3 Third Thermostat TH4 Fourth Thermostat TH5 Fifth Thermostat TH6 6th Thermostat TRA switching element TRB switching element TR1 First temperature reference circuit TR2 Second temperature reference circuit TR3 Third temperature reference circuit TR4 Fourth temperature reference circuit TR5 Fifth temperature reference circuit TR6 Sixth temperature reference circuit TR7 Seventh temperature reference circuit TR8 Eighth temperature reference circuit TR9 9th temperature setting circuit TR10 Tenth temperature reference circuit TR11 Eleventh temperature reference circuit TR12 Twelfth temperature reference circuit Id input current detection signal Iv input voltage detection signal ΔI comparison operation signal ΔI2 Second comparison operation signal ΔI3 Third comparison operation signal Pa power command signal Pb second power command signal Pd Third power command signal Pe Fourth power command signal Pc power setting signal PTa maximum temperature detection protection signal Pt1 First temperature reference value setting signal Pt2 Second temperature reference value setting signal PCt1 First thermistor signal PCt2 Second thermistor signal PCt3 Third thermistor signal PCt4 4th thermistor signal Sa multiplication processing signal Sc control processing operation signal Ta temperature detection signal Tb second temperature detection signal Th abnormal temperature signal Temperature detection signal for Tk heating coil Tp temperature protection signal T2 Second temperature rise value T3 Third temperature rise value T4 Fourth temperature rise value T5 temperature rise limit value T6 protection release temperature Ta1 first analog switch drive signal Ta2 second analog switch drive signal Ta3 Third analog switch drive signal Tc1 first resistance voltage conversion signal Tc2 Second resistance voltage conversion signal Tc3 Third resistance voltage conversion signal Tc4 Fourth resistance-voltage conversion signal

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H02M 7/5387 H02M 7/5387 AF term (reference) 3K051 AA03 AA08 AB14 AC07 AC33 AC58 AD14 AD24 AD39 BD24 CD14 CD15 CD33 5H007 AA17 BB04 CA02 CB09 CB12 DB01 DC02 DC05 DC08

Claims (12)

[Claims] 1. An apparatus comprising a resonance tank formed by an inverter circuit, a resonance capacitor and a heating coil, wherein the output frequency of the inverter circuit is changed to increase or decrease the impedance value of the resonance tank to control the output current. A control processing arithmetic circuit for controlling the inverter circuit so as to have a predetermined value set by the power setting circuit, and a first thermostat to a fourth thermostat for indirectly detecting the temperature of the heating coil and the temperature of the switching element. And the first thermostat and the second thermostat are connected in series, the first thermostat is installed at a predetermined position near the heating coil, and the second thermostat is set in advance near the switching element. Installed at a specified position, one or both of the above is the temperature of a predetermined value A temperature protection circuit that stops the output of the inverter circuit when the rising limit value is reached, and the third thermostat and the fourth thermostat are connected in series,
The third thermostat is installed at a predetermined position near the heating coil, the fourth thermostat is installed at a predetermined position of the switching element, and one or both of the third thermostat and the fourth thermostat are installed. Reaches a second temperature rise value of a predetermined value, the frequency of the inverter circuit is increased to increase the impedance value of the resonance tank and the current flowing through the heating coil L is decreased to decrease the output, and the variable attenuation circuit is decreased. An induction heating cooker equipped with and. 2. A variable attenuation circuit is formed by a resistor, a first analog switch and an operational amplifier, and
2. The induction device according to claim 1, wherein when one or both of the thermostat and the fourth thermostat are operated, the value of the power setting signal set by the power setting circuit is attenuated to a predetermined value and the second power command signal is output. Heating cooker. 3. The induction heating cooker according to claim 1, further comprising a display lamp that lights up and displays when one or both of the third thermostat and the fourth thermostat are operated. 4. A device having a fifth thermostat and a sixth thermostat for enabling a two-step output reduction, comprising a resonant tank formed by an inverter circuit, a resonant capacitor, and a heating coil, wherein: In a device that controls the output current by increasing / decreasing the impedance value of the resonance tank by changing the output frequency of the inverter circuit, a control processing operation for controlling the inverter circuit to a predetermined value set by the power setting circuit. A circuit, a first thermostat to a sixth thermostat for indirectly detecting the temperature of the heating coil and the temperature of the switching element, the first thermostat and the second thermostat are connected in series, and the first thermostat and the sixth thermostat are connected in series. The thermostat is installed at a predetermined position near the heating coil, and the second thermostat is installed. A temperature protection circuit that installs a switch at a predetermined position near the switching element and stops the output of the inverter circuit when one or both of the above reaches a predetermined temperature increase limit value; and the third thermostat. And a fourth thermostat are connected in series, and a fifth thermostat and a sixth thermostat are also connected in series so that the third thermostat and the fifth thermostat are placed in a predetermined position near the heating coil. Installed, the fourth thermostat 4 and the sixth thermostat are installed at predetermined positions of the switching element,
When one or both of the third thermostat and the fourth thermostat reach the second temperature rise value of a predetermined value, the frequency of the inverter circuit is increased to increase the impedance value of the resonance tank to increase the heating coil L. When the current flowing in the inverter circuit is reduced and then the temperature rises and one or both of the fifth thermostat and the sixth thermostat reaches the third temperature rise value of a predetermined value, the frequency of the inverter circuit is reduced. An induction heating cooker provided with a two-stage variable attenuation circuit for further increasing the impedance value of the resonance tank to further reduce the current flowing through the heating coil L to reduce the output. 5. A two-stage variable attenuation circuit is formed by a resistor, a first analog switch, a second analog switch and an operational amplifier, and when one or both of the third thermostat and the fourth thermostat operate. A predetermined value of the power setting signal set by the power setting circuit is output after being attenuated to 1/2, and one or both of the fifth thermostat and the sixth thermostat operates. The induction heating cooker according to claim 4, which further attenuates the value of the value power setting signal to 1/3 to output a third power command signal. 6. An apparatus for controlling an output current, comprising: a resonance tank formed by an inverter circuit, a resonance capacitor and a heating coil, and changing the output frequency of the inverter circuit to increase or decrease the impedance value of the resonance tank. A control processing arithmetic circuit for controlling the inverter circuit so as to have a predetermined value set by the power setting circuit; and a first for indirectly detecting the temperature of the heating coil, the temperature of the resonant capacitor, and the temperature of the switching element.
The thermistor to the third thermistor and the first thermistor are installed at predetermined positions in the vicinity of the heating coil, and the second thermistor is installed in predetermined positions near the resonance capacitor. Is installed at a predetermined position near the switching element, and a maximum temperature detection protection circuit that stops the output of the inverter circuit when one or all of the three thermistors reach a temperature increase limit value of a predetermined value, When at least one of the first thermistor, the second thermistor, and the third thermistor reaches the second temperature rise value of a predetermined value, the first analog switch drive signal is output and the third temperature rise is generated. When the temperature reaches the value, the second analog switch drive signal is output, and when the temperature further rises to reach the fourth temperature rise value, the third analog switch drive signal is output. In accordance with the output signals of the detection / discrimination circuit and the temperature detection / discrimination circuit, the frequency of the inverter circuit is increased to increase the impedance value of the resonance tank to reduce the current flowing through the heating coil L, and the output is divided into three stages. Induction cooker with a three-stage variable attenuation circuit that lowers the temperature. 7. A three-stage variable attenuator circuit is formed by a resistor, a first analog switch, a second analog switch, a third analog switch and an operational amplifier, and the three-stage variable attenuator circuit generates power depending on an output signal of the temperature detection discrimination circuit. The induction cooking according to claim 6, wherein the value of the power setting signal having a predetermined value set by the setting circuit is attenuated in three steps to 1/2 or 1/3 or 1/4 and the fourth power command signal is output. vessel. 8. An apparatus for controlling an output current, comprising: a resonance tank formed by an inverter circuit, a resonance capacitor, and a heating coil, and changing the output frequency of the inverter circuit to increase or decrease the impedance value of the resonance tank. A control processing arithmetic circuit for controlling the inverter circuit so as to have a predetermined value set by the power setting circuit; a first thermostat and a second thermostat for indirectly detecting the temperature of the heating coil and the temperature of the switching element; Thermostat, the first thermostat and the second thermostat are connected in series, the first thermostat is installed at a predetermined position near the heating coil, and the second thermostat is predetermined near the switching element. The first thermostat and the second thermostat. A temperature protection circuit that stops the output of the inverter circuit when one or both of the temperature reaches a predetermined temperature rise limit value, a first thermistor that indirectly detects the temperature of the heating coil, and The thermistor No. 1 is installed at a predetermined position in the vicinity of the heating coil to detect the temperature, and when the detected temperature reaches the second temperature rise value, the temperature detection for heating coil detection signal for heating coil is output. Induction heating including a determination circuit and a variable attenuation circuit that attenuates the value of the power setting signal to a predetermined value and outputs the second power command signal when the temperature detection determination signal for the heating coil is input. Cooking device. 9. An apparatus for controlling an output current, comprising: a resonance tank formed by an inverter circuit, a resonance capacitor and a heating coil, and changing an output frequency of the inverter circuit to increase or decrease an impedance value of the resonance tank. , A fourth thermistor is installed at a predetermined position inside the pan to detect the temperature change of the pan by converting it into a resistance value and detecting it, and converting the resistance value into a voltage signal to obtain a fourth resistance-voltage conversion signal. A fourth resistance voltage conversion circuit for outputting,
A changeover switch for changing over the multiplication processing signal and the fourth resistance-voltage conversion signal, and an inverter circuit so that the value of the multiplication processing signal becomes a predetermined value set by the power setting circuit when the changeover switch is set to the a side. And a control processing arithmetic circuit that controls the inverter circuit so that the value of the fourth resistance-voltage conversion signal becomes a predetermined value set by the power setting circuit when the changeover switch is set to the b side, and a heating coil. First to fourth thermostats that indirectly detect the temperature of the switching element and the temperature of the switching element, and the first thermostat and the second thermostat are connected in series, and the first thermostat is in the vicinity of the heating coil. Is installed at a predetermined position, the second thermostat is installed at a predetermined position near the switching element, and the first thermos is installed. Of the third thermostat and the fourth thermostat in series with a temperature protection circuit that stops the output of the inverter circuit when one or both of the first thermostat and the second thermostat reach a temperature increase limit value of a predetermined value. The third thermostat is installed at a predetermined position near the heating coil, the fourth thermostat is installed at a predetermined position of the switching element, and the third thermostat and the fourth thermostat are connected. When one or both reach a second temperature rise value of a predetermined value, a variable attenuation circuit that attenuates the value of the power setting signal to a predetermined value and outputs a second power command signal. Heating cooker. 10. An apparatus for controlling an output current, comprising: a resonance tank formed by an inverter circuit, a resonance capacitor, and a heating coil, and changing an output frequency of the inverter circuit to increase or decrease an impedance value of the resonance tank to control an output current. A power setting circuit that outputs a power setting signal having a predetermined value by the power setting circuit; an amplifier circuit that amplifies the value of the power setting signal to a predetermined value and outputs a power command signal; And a power command signal to perform a comparison operation to output a comparison operation signal, a control processing operation circuit to control the inverter circuit according to the value of the comparison operation signal, a heating coil temperature and a switching element temperature. A first thermistor and a third thermistor for indirectly detecting the Installed in a predetermined position, and the third
Second thermistor is installed at a predetermined position near the switching element, and when one or both of the two thermistors reaches a predetermined temperature rise limit value, the second maximum temperature at which the output of the inverter circuit is stopped A detection protection circuit, a first resistance-voltage conversion circuit that converts the resistance value of the first thermistor signal into a voltage signal and outputs a first resistance-voltage conversion signal, and a resistance value of the third thermistor signal as a voltage signal. A third resistance-voltage conversion circuit for converting into a first resistance-voltage conversion signal and a third resistance-voltage conversion signal that outputs a third resistance-voltage conversion signal are compared with the first temperature-reference-value setting signal and the first resistance-voltage conversion signal. A second comparison calculation circuit that outputs a second comparison calculation signal when the value of the first resistance-voltage conversion signal is larger than the value of the reference value setting signal, the second temperature reference value setting signal, and the third resistance Comparing the voltage converted signal When the value of the third resistance-voltage conversion signal is larger than the value of the second temperature reference value setting signal, the third comparison operation circuit that outputs the third comparison operation signal, and the comparison operation signals to the third comparison operation When the diode formed in the OR circuit for selecting a signal having a large signal value and inputting it to the control processing operation circuit and the second comparison operation signal or the third comparison operation signal are selected, the inverter circuit An induction heating cooker that reduces the output. 11. A temperature protection circuit outputs a temperature protection signal when a temperature rise limit value of a predetermined value is reached, and outputs a temperature protection signal when the temperature drops and reaches a protection release temperature of a predetermined value. The hysteresis characteristic for releasing is provided.
Alternatively, the induction heating cooker according to claim 4 or claim 8 or claim 9. 12. A maximum temperature detection protection circuit outputs a maximum temperature detection protection signal when the temperature rise limit value of a predetermined value is reached, and when the temperature drops and reaches a protection release temperature of a predetermined value. The induction heating cooker according to claim 6, further comprising a hysteresis characteristic for releasing the maximum temperature detection protection signal.