JPH09293585A - Ih rice cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease input power of a rice cooker by a specified value and prevent overflowing by detecting input current, converting it into voltage, dividing voltage with resistors, and controlling the drive circuit. SOLUTION: In the circuit of an IH rice cooker, a rectifier circuit 2 is connected to a commercial power source 1, A.C. current is converted into D.C. current, a high frequency magnetic field is generated in a heater coil, and a pot 3 is heated. Signal current outputted from a current detecting means 10 connected to between the power source 1 and the rectifier circuit 2 is converted into voltage with a voltage conversion circuit 14. Output voltage VO of the voltage conversion circuit 14 is divided with first, second, third resistors RB15, RC16, RD17 connected to the output terminal of the voltage conversion circuit 14. Each voltage at both ends of the resistor RC16 is inputted into a comparison circuit 18 of a microcomputer 9. Reference voltage of the comparison circuit 18 is set in resistors RE19, RF20. The microcomputer 9 inputs the voltage across the resistor RC16 when an inverter circuit 7 is oscillated, and outputs a signal into a drive circuit 8 so as to become equal to the reference voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating type rice cooker.

[0002]

2. Description of the Related Art In recent years, needs for diversification and sophistication of consumers' tastes have become stronger, and in order to cook delicious rice, rice cookers using an induction heating system have become popular.

Conventionally, in a rice cooker adopting this type of induction heating system, a rectifier circuit 102 for converting an alternating current into a direct current is connected to a commercial power source 101 as shown in FIG. 12, and an output side of the rectifier circuit 102 is connected. An inverter equipped with a heating coil 104 for generating a high-frequency magnetic field to heat the pan 103, a resonance capacitor 105 which forms a resonance circuit together with the heating coil 104, and a switching element 106 which is connected to the resonance circuit and generates a resonance current. The circuit 107 is connected. A drive circuit 108 is connected to the switching element 106, and a drive signal is supplied to the switching element 106 by a signal from the microcomputer 109. A current detecting means 110 for detecting an input current from the commercial power source 101 is connected between the commercial power source 101 and the rectifier circuit 102, and a variable resistor RY111 and a rectifier are provided on the output side of the current detecting means 110. 112 is connected in parallel, and the smoothing capacitor 11 is connected to the output side of the rectifier 112.
3 is connected in parallel with the resistor 114 to connect the voltage conversion circuit 115, which converts the signal current I1 output from the current detection means 110 into the voltage V0. The output voltage VO of the voltage conversion circuit 115 is the microcomputer 109.
It is input to the internal comparison circuit 116. Also resistor 11
7 and the resistor 118 set the reference voltage VA of the comparison circuit 116, and the microcomputer 109 inputs the output voltage VO of the voltage conversion circuit 115 when the inverter circuit 107 oscillates and is always equal to the predetermined reference voltage VA. So that a signal is output to the drive circuit 108.

In the above structure, the current detecting means 109
Outputs a current having a transfer coefficient A times when the effective value of the input current from the commercial power source 101 is Iin. That is, the output signal current I1 is expressed as (Equation 1). Considering that most of the output signal current I1 flows through the variable resistor RY111, the voltage V1 applied to both ends of the rectifier 112 is expressed as (Equation 2). The output voltage V of the voltage conversion circuit 115
O becomes (Equation 3) when the voltage drop due to the rectifier 112 is V2. The microcomputer 109 uses the comparison circuit 116 to output the output voltage VO of the voltage conversion circuit 115 and the reference voltage VA set by the resistors 117 and 118.
Are compared with each other, and a signal is output to the drive circuit 108 so that VO and VA are always equal to each other.

[0005]

[Equation 1]

[0006]

[Equation 2]

[0007]

(Equation 3)

Then, the actual input current Iin is set to a prescribed value (1200 W ÷ 100 V = when the power consumption is 1200 W).
12A), the resistance value of the variable resistor RY111 may be adjusted so that VO = VA when Iin = 12A.

As shown in FIG. 13, a rice cooker using another conventional induction heating system is connected to a rectifier circuit 102 for converting alternating current into direct current as shown in FIG. 13, and the rectifier circuit 102 has an output side. Generates a high frequency magnetic field and pan 103
An inverter circuit 107 including a heating coil 104 that heats the capacitor, a resonance capacitor 105 that forms a resonance circuit together with the heating coil 104, and a switching element 106 that is connected to the resonance circuit and that generates a resonance current is connected. A drive circuit 108 is connected to the switching element 106, and a drive signal is supplied to the switching element 106 by a signal from the microcomputer 109. A series circuit of a resistor RA119 and a variable resistor RY111 for dividing the voltage V1 across the switching element 106 is connected to both ends of the switching element 106. Further, at the connection point between the resistor RA119 and the variable resistor RY111, a smoothing circuit including a transistor 120, a limiting resistor 121 connected to the collector of the transistor 120, a smoothing capacitor 122 connected to the emitter of the transistor 120, and a discharge resistor 123 is provided. The circuit 124 is connected to the variable resistor RY111.
The voltage V2 at both ends is converted into the smoothed voltage V0. The output voltage V0 of the smoothing circuit 124 is the microcomputer 1
It is input to the comparison circuit 116 in 09. The resistors 117 and 118 are the reference voltage VA of the comparison circuit 116.
The microcomputer 109 inputs the output voltage V0 of the smoothing circuit 124 when the inverter circuit 107 oscillates and outputs a signal to the drive circuit 108 so as to always become equal to a predetermined reference voltage VA. In the IH rice cooker thus configured, the voltage V applied across the switching element 106 of the inverter circuit 107
As for the relationship between 1 and the input power Pi input from the commercial power supply 101, as the voltage V1 at both ends is higher, the input power Pi is higher, as shown in FIG.

In the above structure, when the voltage input to the smoothing circuit 124 is V2, the following equation 4 is obtained, and the voltage dividing ratio is changed by changing the resistance value of the variable resistor RY111.
The voltage V2 input to the smoothing circuit 124 can be changed. The voltage V0 output from the smoothing circuit 124 and input to the comparison circuit 116 in the microcomputer 109 is the voltage drop between the base and emitter of the transistor 120, which is V0.
Let BE be expressed as (Equation 5).

[0011]

(Equation 4)

[0012]

(Equation 5)

On the other hand, the microcomputer 109 uses the comparison circuit 116 to output the output voltage VO of the smoothing circuit 124 and the reference voltage VA set by the resistors 117 and 118.
Are compared with each other, and a signal is output to the drive circuit 108 so that VO and VA are always equal to each other. Then, to set the actual input power Pi to a specified value (when the input power is 1200 W),
Adjust the resistance value of the variable resistor RY111 to set Pi = 120.
It should be adjusted so that VO = VA at 0 W.

[0014]

[Problems to be Solved by the Invention] By the way, when a user actually cooks rice using a rice cooker, the water content of the rice used, the amount of water to be put together with the rice, and the power state of the rice cooker are used. This may cause spilling of the rice cake when cooking rice. In such a case, it is necessary to adjust the rice cooker according to the user's request so as not to spill. The adjusting method is generally to reduce the input power of the rice cooker, and in the case of an IH rice cooker, the variable resistor RY11 is used.
It was common to readjust 1 to reduce the input power.

However, as described above, the variable resistor RY
In order to readjust the 111 and reduce the input power, a measuring instrument such as a power meter or an ammeter for measuring the input power is required, and there is a problem that the adjustment cannot be performed on the spot.

The present invention solves the above-mentioned conventional problems, and when the spillage is eliminated by the request of the user, the input power of the IH rice cooker can be used on the spot without using equipment such as a measuring instrument. It is an object of the present invention to provide a rice cooker that can reduce spillage by reducing the amount of water by a certain value.

[0017]

To achieve the above object, the present invention provides a commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, and a high frequency magnetic field connected to the rectifier circuit. And an inverter circuit including a heating coil for heating the pot, a resonance capacitor that forms a resonance circuit together with the heating coil, and a switching element connected to the resonance circuit to generate a resonance current, and the switching element. Drive circuit, current detection means for detecting an input current from the commercial power source, a voltage conversion circuit for converting a signal current output from the current detection means into a voltage, and a voltage output from the voltage conversion circuit. A first resistor and a second resistor connected in series for voltage division, a third resistor connected in parallel with the second resistor, and when the inverter circuit oscillates Serial voltage across the second resistor type is always provided with a control circuit for controlling the drive circuit to a predetermined voltage.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first aspect of the invention, the current detection means detects the input current from the commercial power source and serially outputs the voltage output from the voltage conversion circuit for converting the output signal current into the voltage. A first resistor and a second resistor connected,
The voltage is divided by the second resistor and the third resistor connected in parallel, and the control circuit inputs the voltage across the second resistor, which is divided at the time of oscillation of the inverter circuit, and always outputs a predetermined voltage. Since the drive circuit is controlled so that
By removing the third resistor, the voltage division ratio changes and the voltage across the second resistor input to the control circuit changes, but the voltage across the second resistor input to the control circuit changes. The input current can be changed in order to control the drive circuit so that the voltage becomes equal to the voltage before the third resistor is abolished.

According to a second aspect of the present invention, the current detection means detects the input current from the commercial power source, and the voltage output from the voltage conversion circuit for converting the output signal current into a voltage is connected in series. The first resistor, the second resistor, and the third resistor connected in parallel with the second resistor divide the voltage, and the control circuit divides the second resistor into two voltages when the inverter circuit oscillates. Since the drive circuit is controlled so that the voltage across the resistor is input so that the voltage always becomes a predetermined voltage, the first switch is opened / closed by the input current changing switch and is connected in parallel to the second resistor. By switching the third resistor between short and open, the voltage division ratio changes and the voltage across the second resistor input to the control circuit changes, but the second resistor input to the control circuit changes. Show the voltage across the resistor through the third resistor / It is possible to change the input current to control the drive circuit to be equal to the previous voltage switching open.

According to the third aspect of the present invention, the signal current output from the current detecting means for detecting the input current from the commercial power source is shunted by the voltage conversion circuit and the third resistor, and the control circuit performs this voltage conversion. Since the drive circuit is controlled so that the voltage output from the circuit is input and the voltage is always the predetermined voltage, the signal current input to the voltage conversion circuit is changed by removing the third resistor. Although the voltage output from the voltage conversion circuit will change, the drive circuit is set so that the voltage from the voltage conversion circuit input to the control circuit becomes equal to the voltage before the third resistor is abolished. The input current can be changed for control.

According to a fourth aspect of the present invention, the signal current output from the current detection means for detecting the input current from the commercial power supply is shunted by the voltage conversion circuit and the third resistor, and the control circuit performs this voltage conversion. Since the drive circuit is controlled so that the voltage output from the circuit is input and the voltage always becomes a predetermined voltage, the first switch is opened / closed by the input current change switch and is connected in parallel to the input side of the voltage conversion circuit. By switching the third resistor, which is set to short / open, the signal current input to the voltage conversion circuit changes, and the voltage output from the voltage conversion circuit changes, but the control circuit is input. The input current can be changed in order to control the drive circuit so that the voltage from the voltage conversion circuit to be equal to the voltage before switching the third resistor between short circuit and open circuit. .

According to a fifth aspect of the present invention, the voltage converting circuit converts the signal current output from the current detecting means for detecting the input current from the commercial power source into the voltage, and the control circuit outputs the voltage converting circuit. Since the drive circuit is controlled so that the voltage is input and the reference voltage is always the predetermined reference voltage, the input current can be changed by changing the reference voltage by the input from the input current change switch. Of.

According to a sixth aspect of the invention, the voltage across the switching element of the inverter circuit is divided by a fourth resistor and a fifth resistor connected in series, and the divided voltage is applied to the first resistor. The voltage across the resistor 5 is converted into a smoothed voltage by a smoothing circuit, and the output voltage output from this smoothing circuit is connected in series to a sixth resistor and a seventh resistor,
The voltage is divided by the seventh resistor and a third resistor connected in parallel, and the control circuit inputs the voltage across the seventh resistor divided at the time of oscillation of the inverter circuit, and always inputs a predetermined voltage. Since the drive circuit is controlled so that the seventh resistor is removed, the seventh resistor is input to the control circuit by removing the third resistor to change the voltage division ratio of the voltage across the seventh resistor. Although the voltage across will change, the drive circuit is controlled so that the voltage across the seventh resistor to which the control circuit is input becomes equal to the voltage before the third resistor is abolished, and switching is performed. The input power can be changed to change the voltage across the element.

According to a seventh aspect of the present invention, the voltage across the switching element of the inverter circuit is divided by a fourth resistor and a fifth resistor connected in series, and the divided voltage is applied to the first resistor. The voltage across the resistor 5 is converted into a smoothed voltage by a smoothing circuit, and the output voltage output from this smoothing circuit is connected in series to a sixth resistor and a seventh resistor,
The voltage is divided by the seventh resistor and a third resistor connected in parallel, and the control circuit inputs the voltage across the seventh resistor divided at the time of oscillation of the inverter circuit, and always inputs a predetermined voltage. Since the drive circuit is controlled so that the input current changing switch opens and closes the first switch, the third resistor connected in parallel with the seventh resistor is switched between short circuit and open circuit. As a result, the voltage division ratio of the voltage across the seventh resistor changes and the voltage across the seventh resistor input to the control circuit changes, but the voltage across the seventh resistor input to the control circuit changes. The input power can be changed by controlling the drive circuit so that the voltage between both ends becomes equal to the voltage before the third resistor is switched between short circuit and open circuit, and the voltage applied to both ends of the switching element is changed.

According to an eighth aspect of the present invention, the voltage across the switching element of the inverter circuit is connected in parallel to the fourth resistor, the fifth resistor and the fifth resistor which are connected in series. The voltage is divided by the third resistor, the divided voltage of the fifth resistor is converted into the smoothed voltage by the smoothing circuit, and the control circuit inputs the output voltage of the smoothing circuit when the inverter circuit oscillates. However, since the drive circuit is controlled so that the voltage always becomes the predetermined voltage, the division ratio of the voltage across the fifth resistor is changed by inputting the third resistor to the control circuit. Although the output voltage of the smoothing circuit will change, the drive circuit is controlled so that the output voltage of the smoothing circuit to which the control circuit is input becomes equal to the voltage before the third resistor is abolished, and the switching element is switched. Change the voltage across It is possible to change the input power to.

According to a ninth aspect of the present invention, the voltage across the switching element of the inverter circuit is connected in series to the fourth resistor, the fifth resistor and the fifth resistor which are connected in series. The voltage is divided by the third resistor, the divided voltage of the fifth resistor is converted into the smoothed voltage by the smoothing circuit, and the control circuit inputs the output voltage of the smoothing circuit when the inverter circuit oscillates. However, since the drive circuit is controlled so that the voltage always becomes a predetermined voltage, the first switch is opened / closed by the input current changing switch to open the third resistor connected in parallel with the fifth resistor. Switching between short circuit and open circuit changes the voltage division ratio of the voltage across the fifth resistor and changes the output voltage of the smoothing circuit that is input to the control circuit. However, the output of the smoothing circuit that is input to the control circuit Voltage to third Resistor controls the driving circuit to be equal to the voltage before switching the short / open,
The input power can be changed to change the voltage across the switching element.

According to a tenth aspect of the present invention, in the first means, the third resistor has a higher resistance value than the second resistor connected in parallel with the third resistor. , The fluctuation of the divided voltage applied to the second resistor due to the presence or absence of the third resistor is reduced, and the change range of the input current can be reduced.

According to the eleventh aspect of the present invention, in the first, third, sixth and eighth means, the third resistor is a lead terminal type resistor, so only a nipper for cutting the lead is used. The third resistor can be eliminated.

According to a twelfth aspect of the present invention, the voltage across the switching element of the inverter circuit is divided by a fourth resistor and a fifth resistor connected in series, and the divided voltage is divided into the first resistor and the fifth resistor. The voltage across the resistor 5 is converted into a smoothed voltage by a smoothing circuit, and the control circuit inputs the output voltage of the smoothing circuit when the inverter circuit oscillates, and controls the drive circuit so that it always becomes a predetermined reference voltage. Therefore, the input power can be changed because the voltage applied to both ends of the switching element is changed by changing the reference voltage according to the signal from the input current changing switch.

[0030]

【Example】

Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of an IH rice cooker according to an embodiment of the present invention, in which a commercial power source 1 is connected to a rectifier circuit 2 for converting alternating current into direct current, and the output side of the rectifier circuit 2 has high An inverter circuit provided with a heating coil 4 for generating a magnetic field to heat the pan 3, a resonance capacitor 5 for forming a resonance circuit together with the heating coil 4, and a switching element 6 connected to the resonance circuit for generating a resonance current. 7 is connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from a microcomputer 9 which is a control circuit. Further, a current detecting means 10 for detecting an input current from the commercial power source 1 is connected between the commercial power source 1 and the rectifying circuit 2, and the current detecting means 1 is connected.
The variable resistor RY11 and the rectifier 12 are connected in parallel on the output side of 0, and the smoothing capacitor 13 is connected on the output side of the rectifier 12.
Is connected to convert the signal current I1 output from the current detecting means 10 into a voltage V0. A resistor RB15, which is a first resistor, and a resistor RC16, which is a second resistor, are connected in series to the output terminal of the voltage conversion circuit 14, and the resistor RC16 has a third resistor. Is connected in parallel and divides the output voltage VO of the voltage conversion circuit 14.
The divided voltage VB across the resistor RC16 is input to the comparison circuit 18 in the microcomputer 9.
The resistor RE19 and the resistor RF20 set the reference voltage VA of the comparison circuit 18, and the microcomputer 9
Is the resistor RC16 when the inverter circuit 7 oscillates.
The voltage VB at both ends is input and a signal is output to the drive circuit 8 so as to be always equal to the predetermined reference voltage VA.

In the above structure, the current detecting means 10 outputs a current having a transfer coefficient A times when the effective value of the input current from the commercial power source 1 is Iin. That is, the output signal current I1 is expressed as (Equation 6). The output signal current I1
Considering that most of the voltage flows through the variable resistor RY11, the voltage V1 applied to both ends of the rectifier 12 is expressed as (Equation 7). Then, the output voltage VO of the voltage conversion circuit 14 becomes (Equation 8) when the voltage drop by the rectifier 12 is V2.
Then, the voltage VB across the resistor RC16 obtained by dividing the output voltage V0 is (Equation 9) when the combined resistance value (parallel resistance value) of the resistor RC16 and the resistor RD17 is RZ1, and is represented by (Equation 10). To be done. Then, the microcomputer 9 outputs a signal to the drive circuit 8 by the comparison circuit 18 so as to be (Equation 11).

[0032]

(Equation 6)

[0033]

(Equation 7)

[0034]

(Equation 8)

[0035]

[Equation 9]

[0036]

(Equation 10)

[0037]

[Equation 11]

When it is desired to adjust the input power of the main body to 1200 W in the IH rice cooker which controls by such an operation,
The input current Iin is (Equation 12), and the variable resistor RY1
The resistance value of 1 should be adjusted so that Iin = 12A and VB = VA.

In the main body in which the variable resistor RY11 has been adjusted in such a state, if the resistor RD17 is abolished, it means that the combined resistance value RZ2 has changed to RZ2 = RC. At this time, RZ1 <RZ2 holds. This means that the voltage dividing ratio of the voltage dividing resistor input to the comparison circuit 18 is increased (Equation 13). Therefore, in order to always satisfy VB = VA, it is necessary to reduce the output voltage of the voltage conversion circuit 14. The output voltage of the voltage conversion circuit 14 at this time is represented by (Equation 14) when V01 is set. Here, since the resistance value of the variable resistor RY11 does not change and the voltage drop V2 by the rectifier 12 is almost constant, the input current when the resistor RD17 is abolished is Iin.
When set to 1, Iin1 <Iin.

[0040]

(Equation 12)

[0041]

(Equation 13)

[0042]

[Equation 14]

As described above, according to the present embodiment, by removing the resistor RD17 while the variable resistor RY11 is fixed, the voltage division ratio is changed and the resistor RC16 of the resistor RC16 input to the comparison circuit 18 of the microcomputer 9 is changed. Although the both-end voltage VB changes, the microcomputer 9 controls the drive circuit 8 so that the inputted both-end voltage VB of the resistor RC16 becomes equal to the voltage before the resistor RD17 is abolished. Can be lowered from Iin to Iin1.

(Second Embodiment) Next, a second embodiment of the present invention will be described. FIG. 2 shows a circuit diagram of an IH rice cooker according to an embodiment of the present invention, in which a commercial power source 1 is connected to a rectifier circuit 2 for converting alternating current into direct current, and the output side of the rectifier circuit 2 has a high frequency. An inverter circuit provided with a heating coil 4 for generating a magnetic field to heat the pan 3, a resonance capacitor 5 for forming a resonance circuit together with the heating coil 4, and a switching element 6 connected to the resonance circuit for generating a resonance current. 7 is connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from the microcomputer 9. A current detecting means 10 for detecting an input current from the commercial power source 1 is connected between the commercial power source 1 and the rectifying circuit 2, and a variable resistor RY11 and a rectifier are provided on the output side of the current detecting means 10. 12 connected in parallel, this rectifier 12
A voltage conversion circuit 14 to which a smoothing capacitor 13 is connected is connected to the output side of, and converts the signal current I1 output from the current detection means 10 into a voltage V0. A resistor RB15 and a resistor RC16 are connected in series to the output terminal of the voltage conversion circuit 14, and a resistor RD17 and a switch A2 which is the first switch are connected in series to the resistor RC16.
1 is connected in parallel, and in the normal state, the switch A21 is set to the ON state, and the voltage conversion circuit 14
The output voltage VO is divided. The divided voltage VB across the resistor RC16 is input to the comparison circuit 18 in the microcomputer 9. Further, the resistors RE19 and RF20 set the reference voltage VA of the comparison circuit 18, and the microcomputer 9 inputs the voltage VB across the resistor RC16 when the inverter circuit 7 oscillates, and always inputs a predetermined reference voltage VA. The signal is output to the drive circuit 8 so as to be equal to. Reference numeral 22 is an input current changing switch for changing the input current from the commercial power supply 1. The microcomputer 9 turns on / off the switch A21 by a signal from the input current changing switch 22.

In the above construction, the description of the same parts as those in the first embodiment will be omitted, and only the different parts will be explained. When the input power of the main body is adjusted to 1200 W using the variable resistor RY11, the switch A21 is The resistor RC16 and the resistor RD17 are set in the ON state and are connected in parallel.

In the main body after adjusting the variable resistor RY11 in such a state, when the LOW signal is input to the microcomputer 9 by pressing the input current changing switch 22, the microcomputer 9 switches the switch A21.
Is turned off, the resistor RD17 becomes unconnected.

As described above, according to the present embodiment, the resistor RD17 can be opened by pressing the input current changing switch 22, and the microcomputer 9 resistances the input voltage VB of the resistor RC16. Bowl RD17
Since the drive circuit 8 is controlled so that the voltage becomes equal to the voltage before the open state, the input current can be reduced from Iin to Iin1 even with the variable resistor RY11 fixed.

(Embodiment 3) Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a circuit diagram of an IH rice cooker according to an embodiment of the present invention, in which a commercial power source 1 is connected to a rectifier circuit 2 for converting an alternating current into a direct current, and an output side of the rectifier circuit 2 has a high frequency magnetic field. An inverter circuit 7 including a heating coil 4 for generating a heat to heat the pot 3, a resonance capacitor 5 that forms a resonance circuit together with the heating coil 4, and a switching element 6 connected to the resonance circuit for generating a resonance current. Are connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from the microcomputer 9. A current detecting means 10 for detecting an input current from the commercial power source 1 is connected between the commercial power source 1 and the rectifying circuit 2, and a variable resistor RY11 and a rectifier are provided on the output side of the current detecting means 10. 12 is connected in parallel, and a voltage conversion circuit 14 in which a smoothing capacitor 13 and a resistor RG23 are connected in parallel is connected to the output side of the rectifier 12, and the signal current output from the current detection means 10 is converted into a voltage V.
Converted to 0. A resistor RH24, which is a third resistor, is connected in parallel to the input side of the voltage conversion circuit 14, and the signal current I output from the current detecting means 10 is connected.
1 is divided into a signal current I2 flowing into the voltage conversion circuit 14 and a signal current I3 flowing into the resistor RH24. The output voltage VO of the voltage conversion circuit 14 is input to the comparison circuit 18 in the microcomputer 9. Further, the resistor RE19 and the resistor RF20 set the reference voltage VA of the comparison circuit 18, and the microcomputer 9 inputs the output voltage VO of the voltage conversion circuit 14 when the inverter circuit 7 oscillates and always receives a predetermined reference voltage. A signal is output to the drive circuit 8 so as to be equal to VA.

In the above structure, the current detecting means 10 outputs a current having a transfer coefficient A times when the effective value of the input current from the commercial power source 1 is Iin. That is, the output signal current I1 is expressed as (Equation 15). Its output signal current I
1 is divided into a signal current I2 flowing into the voltage conversion circuit 14 and a signal current I3 flowing into the resistor RH24, and I1 =
It becomes I2 + I3. Considering that most of the shunted signal current I2 flows through the variable resistor RY11, the input impedance of the voltage conversion circuit 14 becomes substantially equal to RY, and the voltage V1 applied to both ends of the rectifier 12 is expressed as (Equation 16). It Then, the output voltage VO of the voltage conversion circuit 10
VO =, where V2 is the voltage drop across the rectifier 12.
It becomes V1-V2. And the microcomputer 9
The comparison circuit 18 outputs a signal to the drive circuit 8 so that V0 = VA.

[0050]

(Equation 15)

[0051]

(Equation 16)

In the IH rice cooker which controls by such an operation, when it is desired to adjust the input power of the main body to 1200 W,
The input current Iin is (Equation 17), and the variable resistor RY1
The resistance value of 1 should be adjusted so that V0 = VA when Iin = 12A. In the main body after adjusting the variable resistor RY11 in such a state, if the resistor RH24 is abolished, I3 = 0, and the signal current I2A flowing into the voltage conversion circuit 14 changes to I1 = I2A. become. At this time, I2A> I2 holds. This means that the input current to the voltage conversion circuit 14 has increased, and assuming that the output voltage of the voltage conversion circuit 14 when the resistor RH24 is abolished is V01, the variable resistor R
Since the resistance value of Y11 does not change, (Equation 18) is obtained.

[0053]

[Equation 17]

[0054]

(Equation 18)

Therefore, in order to always satisfy V01 = V0 = VA, it is necessary to reduce the input current I2 to the voltage conversion circuit 14. That is, assuming that the input current when the resistor RH24 is abolished is Iin1, Iin1 <Iin.

As described above, according to the present embodiment, by removing the resistor RH24 with the variable resistor RY11 fixed, the input current to the voltage conversion circuit 14 changes from I2 to I2A.
And the output voltage of the voltage conversion circuit 14 input to the comparison circuit 18 of the microcomputer 9 changes from V0 to V01, the microcomputer 9 changes the input output voltage of the voltage conversion circuit 14 to a resistor. The input current can be reduced from Iin to Iin1 in order to control the drive circuit 8 so that it becomes equal to the voltage before the RH24 is abolished.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. FIG. 4 is a circuit diagram of an IH rice cooker according to an embodiment of the present invention, in which a commercial power source 1 is connected to a rectifier circuit 2 for converting alternating current into direct current, and an output side of the rectifier circuit 2 has a high frequency magnetic field. Heating coil 4 that generates heat to heat the pan 3
An inverter circuit 7 including a resonance capacitor 5 which forms a resonance circuit together with the heating coil 4 and a switching element 6 which is connected to the resonance circuit and generates a resonance current is connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from the microcomputer 9.
A current detecting means 10 for detecting an input current from the commercial power source 1 is connected between the commercial power source 1 and the rectifying circuit 2, and a variable resistor RY11 and a rectifier are provided on the output side of the current detecting means 10. A voltage conversion circuit 14 in which 12 is connected in parallel and a smoothing capacitor 13 and a resistor RG 23 are connected in parallel is connected to the output side of the rectifier 12, and the signal current output from the current detection means 10 is converted into a voltage V0. A series circuit of a resistor RH24 and a relay 25 is connected in parallel to the input side of the voltage conversion circuit 14, and in the normal state the relay 25 is set to the ON state and the signal output from the current detection means 10 is output. The current I1 is divided into a signal current I2 flowing into the voltage conversion circuit 14 and a signal current I3 flowing into the resistor RH24. A relay drive circuit 26 that drives the relay 25 is connected to the input side of the relay 25. The output voltage VO of the voltage conversion circuit 14 is input to the comparison circuit 18 in the microcomputer 9. Further, the resistor RE19 and the resistor RF20 are the comparison circuit 1
8 is set as a reference voltage VA, and the microcomputer 9 inputs the output voltage VO of the voltage conversion circuit 14 when the inverter circuit 7 oscillates and always outputs a predetermined reference voltage VA.
The signal is output to the drive circuit 8 so as to be equal to.
Reference numeral 22 is an input current change switch for changing the input current from the commercial power supply 1. The microcomputer 9 outputs a signal to the relay drive circuit 26 by the signal from the input current change switch 22 to turn on / off the relay 25.

In the above construction, the description of the same parts as those of the third embodiment will be omitted, and only the different parts will be explained. When the input power of the main body is adjusted to 1200 W using the variable resistor RY11, the relay 25 is It is set to the ON state, and the resistor R is provided on the input side of the voltage conversion circuit 14.
H24 is connected in parallel, and the signal current I1 output from the current detecting means 10 is divided into a signal current I2 flowing into the voltage conversion circuit 14 and a signal current I3 flowing into the resistor RH24.

In the main body after adjusting the variable resistor RY11 in such a state, when the LOW signal is input to the microcomputer 9 by pressing the input current changing switch 22, the microcomputer 9 outputs a signal to the relay drive circuit 26. Since the output is made and the relay 25 is changed to the off state, the resistor RH24 becomes unconnected.

As described above, according to this embodiment, the resistor RH24 can be opened by pressing the input current changing switch 22, and the microcomputer 9 changes the input output voltage of the voltage conversion circuit 14 to the resistance. Since the drive circuit 8 is controlled so as to be equal to the voltage before the device RH24 is opened, the input current can be reduced from Iin to Iin1 even with the variable resistor RY11 fixed.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described. FIG. 5 shows a circuit diagram of an IH rice cooker according to an embodiment of the present invention, in which a commercial power source 1 is connected to a rectifier circuit 2 for converting alternating current into direct current, and an output side of the rectifier circuit 2 has a high frequency magnetic field. Heating coil 4 that generates heat to heat the pan 3
An inverter circuit 7 including a resonance capacitor 5 which forms a resonance circuit together with the heating coil 4 and a switching element 6 which is connected to the resonance circuit and generates a resonance current is connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from the microcomputer 9.
A current detecting means 10 for detecting an input current from the commercial power source 1 is connected between the commercial power source 1 and the rectifying circuit 2, and a variable resistor RY11 and a rectifier are provided on the output side of the current detecting means 10. A voltage conversion circuit 14 in which 12 is connected in parallel and a smoothing capacitor 13 and a resistor RG 23 are connected in parallel is connected to the output side of the rectifier 12, and the signal current I1 output from the current detection means 10 is converted into a voltage V0. .
The output voltage VO of the voltage conversion circuit 14 is input to the comparison circuit 18 in the microcomputer 9. Further, the resistor RE19 and the resistor RF20 are connected in series, and the voltage across the resistor RF20 is used as the reference voltage VA of the comparison circuit 18. The resistor RF20 has a resistor RI27 as a third resistor and a switch B2 as a first switch.
8 series circuits are connected in parallel, and in the normal state, the switch B28 is set to the off state. Reference numeral 22 is an input current change switch for changing the input current from the commercial power supply 1, and the microcomputer 9 turns on / off the switch B28 by a signal from the input current change switch 22.

In the above structure, the current detecting means 10 outputs a current having a transfer coefficient A times when the effective value of the input current from the commercial power source 1 is Iin. That is, the output signal current I1 is expressed as (Equation 19). Its output signal current I
Considering that most of 1 flows in the variable resistor RY11, the voltage V1 applied to both ends of the rectifier 12 is expressed as (Equation 20). The output voltage VO of the voltage conversion circuit 14 is VO = V1−, where V2 is the voltage drop across the rectifier 12.
It becomes V2. On the other hand, in the initial and normal states, switch B28
Is in the off state, the reference voltage VA is (Equation 21). Then, the microcomputer 9 outputs a signal to the drive circuit 8 by the comparison circuit 18 so that V0 = VA.

[0063]

[Equation 19]

[0064]

(Equation 20)

[0065]

(Equation 21)

When it is desired to adjust the input power of the main body to 1200 W in the IH rice cooker controlled by such an operation,
The input current Iin is (Equation 22), and the variable resistor RY1 is
The resistance value of 1 should be adjusted so that V0 = VA when Iin = 12A.

[0067]

(Equation 22)

In the main body in which the variable resistor RY11 has been adjusted in such a state, when the LOW signal is input to the microcomputer 9 by pressing the input current change switch 22, the microcomputer 9 switches the switch B28.
Is turned on, the resistor RI27 becomes connected.

In this state, the resistor RF20 and the resistor RI are
Since 27 is connected in parallel, the reference voltage VA1 at this time is
Is smaller than when the resistor RI27 is not connected, and V
It is expressed as A1 <VA. When the output voltage of the voltage conversion circuit 14 in the connected state of the resistor RI27 is V01, the microcomputer 9 controls the drive circuit 8 so that V01 = VA1 is always satisfied. Therefore, the voltage conversion in the connected state of the resistor RI27 is performed. The output voltage V01 of the circuit 14 is V01 <V0
The input current is reduced from Iin to Iin1 so as to satisfy the condition.

As described above, according to this embodiment, the resistor RI27 can be short-circuited by pressing the input current change switch 22, and the microcomputer 9 changes the input output voltage of the voltage conversion circuit 14 to the resistance value. Since the drive circuit 8 is controlled so that the device RI27 becomes equal to the reference voltage VA1 in the short-circuited state, the input current can be reduced from Iin to Iin1 even with the variable resistor RY11 fixed.

(Embodiment 6) Next, a sixth embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a circuit diagram of an IH rice cooker according to an embodiment of the present invention, in which a commercial power source 1 is connected to a rectifier circuit 2 for converting alternating current into direct current,
A high-frequency magnetic field is generated on the output side of the rectifier circuit 2 to generate a pan 3
An inverter circuit 7 including a heating coil 4 for heating the same, a resonance capacitor 5 that forms a resonance circuit together with the heating coil 4 and a switching element 6 that is connected to this resonance circuit and generates a resonance current is connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from the microcomputer 9. A series circuit of a resistor RJ29 and a variable resistor RY11 for dividing the voltage V1 across the switching element 6 is connected to both ends of the switching element 6. At the connection point between the resistor RJ29 and the variable resistor RY11, a transistor 30, a limiting resistor 31 connected to the collector of the transistor 30, a smoothing capacitor 32 connected to the emitter of the transistor 30, and a discharge resistor 33. Is connected to the variable resistor RY11 to convert the voltage V2 across the variable resistor RY11 into the smoothed voltage V0. The output voltage V0 of the smoothing circuit 34 includes a resistor RK35 which is a sixth resistor connected in series, a resistor RL36 which is a seventh resistor, and a resistor RM37 which is connected in parallel with the resistor RL36. This resistor RL36 is divided by
The voltage VC across is input to the comparison circuit 18 in the microcomputer 9. In addition, resistor RE19 and resistor R
F20 sets the reference voltage VA of the comparison circuit 18,
The microcomputer 9 inputs the voltage VC across the resistor RL36 when the inverter circuit 7 oscillates, and outputs a signal to the drive circuit 8 so that the voltage VC is always equal to a predetermined reference voltage VA. In the IH rice cooker configured as described above, the relationship between the voltage V1 applied to both ends of the switching element 6 of the inverter circuit 7 and the input power Pi input from the commercial power supply 1 is shown in FIG. As shown, the higher the voltage V1 at both ends, the higher the input power Pi.

In the above configuration, if the voltage input to the smoothing circuit 34 is V2 (Equation 23), the voltage dividing ratio is changed by changing the resistance value of the variable resistor RY11, and the voltage is input to the smoothing circuit 34. The voltage V2 can be changed. Further, the output voltage V0 output from the smoothing circuit 34 is expressed as (Equation 24) when the voltage drop between the base and the emitter of the transistor 30 is VBE. The voltage VC across the resistor RL36 obtained by dividing the output voltage V0 is the resistor RL3.
When the combined resistance value (parallel resistance value) RZ of 6 and the resistor RM37 is RZ3, (Equation 25) is obtained and is represented by (Equation 26).

[0073]

(Equation 23)

[0074]

(Equation 24)

[0075]

(Equation 25)

[0076]

(Equation 26)

On the other hand, the microcomputer 9 causes the comparison circuit 18 to detect the voltage VC across the resistor RL36 and the resistor RE.
19 is compared with the reference voltage VA set by the resistor RF20, and the drive circuit 8 is set so that VC and VA are always equal.
Output the signal.

To set the actual input power Pi to a specified value (when the input power is 1200 W), the variable resistor R
Adjust the resistance value of Y11 and set Pi = 1200W and VC = V
It should be adjusted so that it becomes A. Then, in this state, the voltage applied across the switching element 6 is V1.
Set to 1.

In the main body in which the variable resistor RY11 has been adjusted in such a state, if the resistor RM37 is eliminated, the combined resistance value RZ is RZ4 and RZ4.
= RL. And at this time RZ3 <
RZ4 is established. This means that the voltage division ratio of the voltage VC across the resistor RL36 input to the comparison circuit 18 is increased (Equation 27). Therefore, in order to always satisfy VC = VA, it is necessary to reduce the output voltage V0 output from the smoothing circuit 34. The output voltage of the smoothing circuit 34 at this time is represented by (Equation 28) when V01 is set. Here, the resistance value of the variable resistor RY11 does not fluctuate, and the voltage drop VBE between the base and the emitter of the transistor 30 is almost constant. Therefore, the voltage applied to both ends of the switching element 6 when the resistor RM37 is abolished. V12 is V
12 <V11, and when the input power at this time is Pi1, (Equation 29) is obtained.

[0080]

[Equation 27]

[0081]

[Equation 28]

[0082]

(Equation 29)

As described above, according to the present embodiment, by removing the resistor RM37 with the variable resistor RY11 fixed, the voltage division ratio of the voltage VC across the resistor RL36 changes, and the comparison circuit 18 of the microcomputer 9 is changed. The voltage VC across the resistor RL36 input to
Since the microcomputer 9 controls the drive circuit 8 so that the input voltage VC across the resistor RL36 becomes equal to the voltage before the resistor RM37 is abolished, the input power can be reduced from Pi to Pi1.

(Embodiment 7) Next, a seventh embodiment of the present invention will be described. FIG. 7 is a circuit diagram of an IH rice cooker according to an embodiment of the present invention, in which a rectifier circuit 2 for converting alternating current to direct current is connected to a commercial power source 1, and a high frequency wave is provided on the output side of the rectifier circuit 2. An inverter circuit provided with a heating coil 4 for generating a magnetic field to heat the pan 3, a resonance capacitor 5 for forming a resonance circuit together with the heating coil 4, and a switching element 6 connected to the resonance circuit for generating a resonance current. 7 is connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from the microcomputer 9. A resistor RJ29 for dividing the voltage V1 across the switching element 6 and a variable resistor RY11 are provided across the switching element 6.
Are connected in series. At the connection point between the resistor RJ29 and the variable resistor RY11, a transistor 30, a limiting resistor 31 connected to the collector of the transistor 30, a smoothing capacitor 32 connected to the emitter of the transistor 30, and a discharge resistor 33. Is connected to the smoothing circuit 34, and the voltage V across the variable resistor RY11 is
2 is converted into the smoothed voltage V0. A resistor RK35 and a resistor RL36 are connected in series to an output terminal of the smoothing circuit 34, and a circuit of a resistor RM37 connected in series and a circuit of a switch C38 which is a first switch is connected in parallel to the resistor RL36. The switch C3 is in the normal state.
8 is set to the ON state and the output voltage VO of the smoothing circuit 34 is divided. The voltage VC across the resistor RL36 is input to the comparison circuit 18 in the microcomputer 9. In addition, resistor RE19 and resistor RF20
Sets the reference voltage VA of the comparison circuit 18, and the microcomputer 9 inputs the voltage VC across the resistor RL36 when the inverter circuit 7 oscillates so that the drive circuit is always equal to the predetermined reference voltage VA. The signal is output to 8. Further, 39 is an input power changing switch for changing the input power from the commercial power source 1, and the microcomputer 9 turns on / off the switch C38 by a signal from the input power changing switch 39.

In the above structure, the description of the operation of the same parts as those of the sixth embodiment will be omitted, and only the different parts will be described. When the input power of the main body is adjusted to 1200 W by using the variable resistor RY11, the switch C38 is The resistor RL36 and the resistor RM37 are set to be in an on state and are connected in parallel.

In the main body after adjusting the variable resistor RY11 in such a state, when the LOW signal is input to the microcomputer 9 by pressing the input power change switch 39, the microcomputer 9 switches the switch C38.
Is turned off, the resistor RM37 becomes unconnected.

As described above, according to this embodiment, the resistor RM37 can be opened by pressing the input power change switch 39, and the voltage VC across the resistor RL36 can be increased.
The voltage dividing ratio of the signal changes and the comparison circuit 1 of the microcomputer 9
Although the voltage VC across the resistor RL36 input to 8 is changed, the microcomputer 9 makes the voltage VC across the resistor RL36 input equal to the voltage before the resistor RM37 is opened. Since the drive circuit 8 is controlled in accordance with the above, the input power can be reduced from Pi to Pi1 even with the variable resistor RY11 fixed.

(Embodiment 8) Next, an eighth embodiment of the present invention will be described with reference to the drawings. FIG. 8 shows a circuit diagram of an IH rice cooker according to an embodiment of the present invention. A rectifier circuit 2 for converting alternating current into direct current is connected to a commercial power source 1, and a high frequency magnetic field is provided on the output side of the rectifier circuit 2. An inverter circuit 7 including a heating coil 4 for generating a heat to heat the pot 3, a resonance capacitor 5 that forms a resonance circuit together with the heating coil 4, and a switching element 6 connected to the resonance circuit for generating a resonance current. Are connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from the microcomputer 9. Further, a resistor RJ29 and a variable resistor RY11 are connected in series at both ends of the switching element 6, and a resistor RN40 which is a third resistor is connected in parallel to the variable resistor RY11. The voltage V1 across the element 6 is divided. At the connection point between the resistor RJ29 and the variable resistor RY11, a transistor 30, a limiting resistor 31 connected to the collector of the transistor 30, a smoothing capacitor 32 connected to the emitter of the transistor 30, and a discharge resistor 33. Is connected to a smoothing circuit 34 composed of a variable resistor RY11.
The voltage V2 at both ends is converted into the smoothed voltage V0. The output voltage V0 of the smoothing circuit 34 is input to the comparison circuit 18 in the microcomputer 9. Also resistor R
E19 and the resistor RF20 are the reference voltage VA of the comparison circuit 18.
The microcomputer 9 sets the output voltage V0 of the smoothing circuit 34 when the inverter circuit 7 oscillates.
Is input and a signal is output to the drive circuit 8 so that it is always equal to a predetermined reference voltage VA. In the IH rice cooker configured as described above, the voltage V1 applied across the switching element 6 of the inverter circuit 7 as described in the conventional example.
14, the relationship between the input power Pi input from the commercial power source 1 is as shown in FIG.
Is high.

In the above configuration, the variable resistor RY11
When the combined resistance value RX of the resistor RN40 and the resistor RN40 is RX1, (Equation 30) is obtained, and the voltage V2 input to the smoothing circuit 34 is obtained.
Is expressed by (Equation 31), and the voltage division ratio can be changed by changing the resistance value of the variable resistor RY11 to change the voltage V2 input to the smoothing circuit 34. Further, the output voltage V0 output from the smoothing circuit 34 is V0 = V2-VBE, where VBE is the voltage drop between the base and emitter of the transistor 30.
It is expressed as

[0090]

[Equation 30]

[0091]

(Equation 31)

On the other hand, the microcomputer 9 compares the output voltage V0 output from the smoothing circuit 34 by the comparison circuit 18 with the reference voltage VA set by the resistor RE19 and the resistor RF20, and V0 and VA are always equal to each other. To output a signal to the drive circuit 8.

In order to set the actual input power Pi to a specified value (when the input power is 1200 W), the variable resistor R
Adjusting the resistance value of Y11, Pi = 1200W and V0 = V
It should be adjusted so that it becomes A. Then, in this state, the voltage applied across the switching element 6 is V1.
Set to 1.

In the main body in which the variable resistor RY11 has been adjusted in such a state, if the resistor RN40 is eliminated, the combined resistance value RX is RX2 and RX2.
= RY. And at this time RX1 <
RX2 is established. This means that the voltage division ratio of the voltage across the variable resistor RY11 input to the smoothing circuit 34 is increased (Equation 32). When the voltage V2 input to the smoothing circuit 34 at this time is V21, it is expressed as (Equation 33). Therefore, the resistance value of the variable resistor RY11 does not change, and the voltage drop VB between the base and the emitter of the transistor 30 is expressed.
In order to always satisfy V0 = VA while E remains almost constant, it is necessary to reduce the voltage V1 applied to both ends of the switching element 6. That is, the voltage applied to both ends of the switching element 6 when the resistor RN40 is abolished is V12.
Then, it is expressed as (Equation 34). Therefore, if the input power at this time is Pi1, then (Equation 35) is obtained.

[0095]

(Equation 32)

[0096]

[Equation 33]

[0097]

(Equation 34)

[0098]

(Equation 35)

As described above, according to the present embodiment, by removing the resistor RN40 with the variable resistor RY11 fixed, the division ratio of the voltage V2 across the variable resistor RY11 input to the smoothing circuit 34 changes. Microcomputer 9
Although the output voltage V0 output from the smoothing circuit 34 input to the comparator circuit 18 of FIG. 2 changes, the microcomputer 9 eliminates the output voltage V0 output from the smoothing circuit 34 input by the resistor RN40. In order to control the drive circuit 8 to be equal to the voltage before
It can be lowered from i to Pi1.

(Ninth Embodiment) Next, a ninth embodiment of the present invention will be described. FIG. 9 is a circuit diagram of an IH rice cooker according to an embodiment of the present invention, in which a commercial power source 1 is connected to a rectifier circuit 2 for converting alternating current into direct current, and an output side of the rectifier circuit 2 has a high frequency magnetic field. Heating coil 4 that generates heat to heat the pan 3
An inverter circuit 7 including a resonance capacitor 5 which forms a resonance circuit together with the heating coil 4 and a switching element 6 which is connected to the resonance circuit and generates a resonance current is connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from the microcomputer 14. A resistor RJ is provided at both ends of the switching element 6.
29 and a variable resistor RY11 are connected in series, and a circuit of a resistor RN40 and a switch C38 connected in series is connected in parallel to the variable resistor RY11. In a normal state, the switch C38 is set to an ON state. Then, the voltage V1 across the switching element 6 is divided. At the connection point between the resistor RJ29 and the variable resistor RY11, a transistor 30, a limiting resistor 31 connected to the collector of the transistor 30, a smoothing capacitor 32 connected to the emitter of the transistor 30, and a discharge resistor 33. Is connected to a smoothing circuit 34 composed of a variable resistor RY11.
The voltage V2 at both ends is converted into the smoothed voltage V0. The output voltage V0 of the smoothing circuit 34 is input to the comparison circuit 18 in the microcomputer 9. Also resistor R
E19 and the resistor RF20 are the reference voltage VA of the comparison circuit 18.
The microcomputer 9 sets the output voltage V0 of the smoothing circuit 34 when the inverter circuit 7 oscillates.
Is input and a signal is output to the drive circuit 8 so that it is always equal to a predetermined reference voltage VA. 39 is a commercial power source 1
The input power changing switch changes the input power from the input power changing switch 39, and the microcomputer 9 turns on / off the switch C38 by a signal from the input power changing switch 39.

In the above structure, the description of the same parts as those of the eighth embodiment will be omitted, and only the different parts will be described. When the input power of the main body is adjusted to 1200 W by using the variable resistor RY11, the switch C38 is The variable resistor RY11 and the resistor RN4 are set to the ON state.
0 is set in a state of being connected in parallel.

In the main body after adjusting the variable resistor RY11 in such a state, when the LOW signal is input to the microcomputer 9 by pressing the input power changing switch 39, the microcomputer 9 switches the switch C38.
Is turned off so that the resistor RN40 becomes unconnected.

As described above, according to the present embodiment, the resistor RN40 can be opened by pressing the input power change switch 39, the voltage division ratio of the voltage V2 across the variable resistor RY11 changes, and the microcomputer Although the output voltage V0 output from the smoothing circuit 34 input to the comparator circuit 18 of 9 is changed, the microcomputer 9 opens the output voltage V0 output from the smoothing circuit 34 into the resistor RN40. Since the drive circuit 8 is controlled so as to be equal to the voltage before the state, the input power is changed from Pi to Pi even when the variable resistor RY11 is fixed.
Can be lowered to 1.

(Embodiment 10) Next, a tenth embodiment of the present invention will be described. Here, the configuration of this embodiment is the same as the first embodiment.
Since it is the same as the first embodiment, the description of the circuit and the operation will be omitted, and only different points will be described with reference to FIG. In this embodiment, the relationship between the resistance values of the resistors RC16 and RD17 is set to RC <RD = B × RC (however, B> 1). At this time, the combined resistance value (parallel resistance value) RZ1 of the resistor RC16 and the resistor RD17 is represented by (Equation 36),
The relationship of (Equation 37) is established. Meanwhile, the resistor RD17
The combined resistance value RZ2 when the resistor is abolished is RZ2 = RC, and the change in the combined resistance value before and after the resistor RD17 is abolished is 1/2 or less of the resistance value of the resistor RC16. The larger the above-mentioned B value, the smaller the change in the combined resistance value, and as a result, the fluctuation range of the input current becomes smaller.

[0105]

[Equation 36]

[0106]

(37)

As described above, according to this embodiment, by removing the resistor RD17 having a large resistance value out of the resistors connected in parallel while the variable resistor RY11 is fixed, the voltage division ratio is slightly changed and the microcomputer is changed. 9 comparison circuit 1
The voltage across the resistor RC16 input to 8 changes, but the microcomputer 9 drives the input circuit so that the voltage across the resistor RC16 becomes equal to the voltage before the resistor RD17 is abolished. 8 is controlled, the input current can be reduced from Iin to Iin1 and the amount of change can be reduced.

(Embodiment 11) Next, an eleventh embodiment of the present invention will be described. Here, the configuration of this embodiment is the same as the first embodiment.
Since it is the same as the embodiment described above, the description of the circuit and the operation will be omitted, and only different points will be described.

FIG. 10 is a sectional view of a printed wiring board on which the circuit of the IH rice cooker of the embodiment of the present invention is mounted, 41 is a printed wiring board on which the circuit of the IH rice cooker is mounted, and 17 is a lead terminal type. In the resistor RD shown in FIG. 1, the lead terminal is inserted into the component insertion hole of the printed wiring board 41. 42 is a solder, which is a lead portion of the resistor RD17,
The pattern part (not shown) of the printed wiring board 41 is soldered.

In the above structure, when the fixed resistor RD17 is removed from the printed wiring board 41, the lead terminal of the resistor RD17 need only be cut with a tool such as a nipper.

As described above, according to this embodiment, the resistor RD is
Since 17 is a lead terminal type resistor, the resistor RD17 can be removed from the printed wiring board 41 only with a tool such as a nipper that does not require electricity like a soldering iron, and the microcomputer 9 can change the input voltage to a resistance. Since the drive circuit 8 is controlled so as to be equal to the voltage before the device RD17 is removed, the input power can be reduced from Pi to Pi1 even with the variable resistor RY11 fixed.

(Embodiment 12) Next, a twelfth embodiment of the present invention will be described. FIG. 11 shows I of an embodiment of the present invention.
In the circuit diagram of the H rice cooker, a rectifier circuit 2 for converting an alternating current into a direct current is connected to a commercial power source 1.
On the output side of the heating coil 4, a heating coil 4 for generating a high-frequency magnetic field to heat the pan 3, a resonance capacitor 5 that forms a resonance circuit together with the heating coil 4, and a switching element 6 connected to this resonance circuit for generating a resonance current are provided. An inverter circuit 7 including a and is connected. A drive circuit 8 is connected to the switching element 6, and a drive signal is supplied to the switching element 6 by a signal from the microcomputer 9. A resistor RJ29 for dividing the voltage V1 across the switching element 6 and a variable resistor RY are provided across the switching element 6.
11 series circuits are connected. Also, the resistor RJ2
9 is connected to the variable resistor RY11 at the connection point of the transistor 3
0, a limiting resistor 31 connected to the collector of the transistor 30, a smoothing circuit 34 including a smoothing capacitor 32 and a discharge resistor 33 connected to the emitter of the transistor 30, and a voltage across the variable resistor RY11. V2 is converted to the smoothed voltage V0. The output voltage V0 of the smoothing circuit 34 is input to the comparison circuit 18 in the microcomputer 9. Further, the resistor RE19 and the resistor RF20 set the reference voltage VA of the comparison circuit 18, and this resistor RF20 has the resistor RP43 and the first resistor RP43.
The series circuit of the switch D44, which is the switch of the above, is connected in parallel, and in the normal state, the switch D44 is set to the off state. In this state, the microcomputer 9 inputs the output voltage V0 of the smoothing circuit 34 when the inverter circuit 7 oscillates, and outputs a signal to the drive circuit 8 so that it is always equal to a predetermined reference voltage VA. Further, 39 is an input power change switch for changing the input power from the commercial power supply 1, and the microcomputer 9 turns on / off the switch D44 by a signal from the input power change switch 39. In the IH rice cooker configured as described above, the relationship between the voltage V1 applied to both ends of the switching element 6 of the inverter circuit 7 and the input power Pi input from the commercial power supply 1 is shown in FIG. As shown, the higher the voltage V1 at both ends, the higher the input power Pi.

In the above configuration, when the voltage input to the smoothing circuit 34 is V2 (Equation 38), the voltage dividing ratio is changed by changing the resistance value of the variable resistor RY11, and the voltage is input to the smoothing circuit 34. The voltage V2 can be changed. The output voltage V0 output from the smoothing circuit 34 is expressed as V0 = V2-VBE when the voltage drop between the base and emitter of the transistor 30 is VBE. On the other hand, since the switch D44 is in the off state in the initial and normal states, the reference voltage VA is (Equation 39). Then, the microcomputer 9 outputs a signal to the drive circuit 8 by the comparison circuit 18 so that V0 = VA. Then, in order to set the actual input power Pi to a specified value (when the input power is 1200 W), the resistance value of the variable resistor RY11 is adjusted and Pi = 1.
It should be adjusted so that V0 = VA at 200 W. The voltage applied across the switching element 6 in this state is V11.

[0114]

(38)

[0115]

[Equation 39]

In the main body after adjusting the variable resistor RY11 in such a state, when the LOW signal is input to the microcomputer 9 by pressing the input power changing switch 39, the microcomputer 9 switches the switch D44.
Is turned on so that the resistor RP43 is connected.

In this state, the resistor RF20 and the resistor RP are
Since 43 is connected in parallel, assuming that the reference voltage VA at this time is VA1, the value of the resistor RP43 becomes smaller than that when it is not connected, and VA1 <VA is expressed.

On the other hand, when the output voltage output from the smoothing circuit 34 in the connected state of the resistor RP43 is V01, the microcomputer 9 always controls the drive circuit 8 so as to satisfy V01 = VA1. In the connected state, the output voltage V01 output from the smoothing circuit 34 satisfies V01 <V0. Here, since the resistance value of the variable resistor RY11 does not change and the voltage drop VBE between the base and the emitter of the transistor 30 is almost constant, the voltage applied to both ends of the switching element 6 when the resistor RP43 is connected is changed. If V12, V12 <V11,
If the input power at this time is Pi1, Pi1 <Pi = 1
It becomes 200W.

As described above, according to the present embodiment, the resistor RP43 can be short-circuited by pressing the input power changing switch 39, and the microcomputer 9 outputs the output voltage output from the smoothing circuit 34. In order to control the drive circuit 8 so that V0 becomes equal to the reference voltage VA1 when the resistor RP43 is short-circuited, the variable resistor RY
The input power can be reduced from Pi to Pi1 even when 11 is fixed.

[0120]

As described above, according to the first aspect of the invention, the current detecting means detects the input current from the commercial power source, and outputs the output signal current from the voltage converting circuit for converting the voltage into the voltage. The voltage is applied to a first resistor and a second resistor connected in series, and a third resistor connected in parallel to the second resistor.
, And the control circuit inputs the voltage across the second resistor, which is divided at the time of oscillation of the inverter circuit, and controls the drive circuit so that the voltage always becomes a predetermined voltage. Therefore, by removing the third resistor, the voltage across the second resistor changes, but before the control circuit changes the voltage across the second resistor to the voltage before the third resistor is abolished. Since the drive circuit is controlled so as to be equal to the voltage, the input power of the IH rice cooker can be reduced by a constant value and spillage can be eliminated without using equipment such as a measuring instrument.

According to the second aspect of the present invention, the current detecting means detects the input current from the commercial power source and serially outputs the voltage output from the voltage conversion circuit for converting the output signal current into voltage. The voltage is divided by the first resistor and the second resistor that are connected, and the third resistor that is connected in parallel with the second resistor, and the control circuit divides the voltage by the first resistor and the third resistor that are connected in parallel with the second resistor. The voltage across the resistor of No. 2 is input, the drive circuit is controlled so that it always becomes a predetermined voltage, and the first switch is turned off by the input from the input current change switch. The third resistor can be opened by simply pressing the current change switch, and the control circuit changes the input voltage across the second resistor to the voltage before the third resistor is opened. Control the drive circuit to be equal to Because, the input power of the IH rice cooker without using equipment and tools of the instrument such as lowered by a predetermined value,
A rice cooker that can eliminate spillage can be provided.

According to the third aspect of the invention, the signal current output from the current detecting means for detecting the input current from the commercial power source is shunted by the voltage conversion circuit and the third resistor, and the control circuit is obtained. Since the voltage output from this voltage conversion circuit is input and the drive circuit is controlled so that the voltage always becomes a predetermined voltage, the equipment such as a measuring instrument can be installed by removing the third resistor. It is possible to provide a rice cooker that can reduce the spillage by reducing the input power of the IH rice cooker by a certain value without using.

According to the invention described in claim 4, the signal current output from the current detecting means for detecting the input current from the commercial power source is shunted by the voltage conversion circuit and the third resistor, and the control circuit is Receives the voltage output from the voltage conversion circuit, controls the drive circuit so that the voltage always becomes a predetermined voltage, and receives the first current from the input current change switch.
Since the switch is turned off, the third resistor can be opened by simply pressing the input current change switch, and the IH rice cooker can be used without using equipment such as measuring instruments or tools. It is possible to provide a rice cooker that can reduce the spillage by reducing the input power of the battery by a certain value.

According to the invention of claim 5, the reference voltage is changed by the input from the input current changing switch, so that the IH rice cooker can be used without using equipment such as a measuring instrument or tools. It is possible to provide a rice cooker that can reduce the spillage by reducing the input power of the battery by a certain value.

According to the sixth aspect of the invention, the voltage V1 across the switching element of the inverter circuit is applied.
Is divided by a fourth resistor and a fifth resistor connected in series, the voltage across the divided fifth resistor is smoothed, and the smoothed voltage is further connected in series. The voltage is divided by the sixth resistor and the seventh resistor connected to the third resistor and the third resistor connected in parallel with the seventh resistor, and the control circuit divides the voltage when the inverter circuit oscillates. The voltage across the 7th resistor is input and the control is performed so that the voltage is always the predetermined voltage. Therefore, by removing the 3rd resistor, IH can be used without using equipment such as a measuring instrument. A rice cooker that can reduce spillage by reducing the input power of the rice cooker by a certain value can be provided.

According to the invention described in claim 7, the third resistor according to claim 6 can be brought into an open state only by turning off the first switch. Therefore, it is possible to provide a rice cooker that can extremely easily reduce the input power of the IH rice cooker by a certain value and eliminate spillage.

According to the eighth aspect of the invention, the voltage across the switching element of the inverter circuit is applied to the fourth resistor, the fifth resistor and the fifth resistor which are connected in series. Voltage is divided by a third resistor connected in parallel with, the voltage across the divided fifth resistor is smoothed, and the output voltage is controlled to be always a predetermined voltage. By removing the third resistor, it is possible to provide a rice cooker that can reduce the spillage by reducing the input power of the IH rice cooker by a certain value without using equipment such as a measuring instrument.

According to the invention described in claim 9, the third resistor according to claim 8 can be easily electrically disconnected by turning off the first switch. It is possible to provide a rice cooker that can reduce spillage by reducing the input power of the IH rice cooker by a certain value without using such equipment.

According to the tenth aspect of the invention, by eliminating the third resistor having a large resistance value out of the resistors connected in parallel while fixing the fifth resistor, the voltage division ratio can be improved. The second that changes a little and is input to the comparison circuit of the control circuit
However, the control circuit controls the drive circuit so that the input voltage across the second resistor becomes equal to the voltage before the third resistor is abolished. Therefore, it is possible to provide a rice cooker that can reduce the spillage by reducing the input power of the IH rice cooker by a certain value without using equipment such as a measuring instrument.

According to the eleventh aspect of the present invention, the third resistor is a lead terminal type resistor. Therefore, unlike the soldering iron, a tool such as a nipper that does not require electricity can be used for the third resistor. Can be removed and the control circuit controls the drive circuit so that the input voltage becomes equal to the voltage before the third resistor was abolished. Provide a rice cooker that can reduce spillage only by lowering it.

According to the twelfth aspect of the invention, the voltage across the switching element of the inverter circuit is
The voltage is divided by the fourth resistor and the fifth resistor connected in series, the divided voltage V2 of the fifth resistor is smoothed by the smoothing circuit, and the control circuit oscillates the inverter circuit. Sometimes, the smoothed voltage is input, the drive circuit is controlled so that it always becomes a predetermined reference voltage, and the first switch is turned on by the input from the input power change switch. By pressing the power change switch, the third resistor can be short-circuited and the reference voltage can be lowered, so the input power of the IH rice cooker can be reduced by a certain value without using equipment such as measuring instruments. A rice cooker that can eliminate spillage can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an IH rice cooker according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of an IH rice cooker according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of an IH rice cooker according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of an IH rice cooker according to a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram of an IH rice cooker according to a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram of an IH rice cooker according to a sixth embodiment of the present invention.

FIG. 7 is a circuit diagram of an IH rice cooker according to a seventh embodiment of the present invention.

FIG. 8 is a circuit diagram of an IH rice cooker according to an eighth embodiment of the present invention.

FIG. 9 is a circuit diagram of an IH rice cooker according to a ninth embodiment of the present invention.

FIG. 10 is a cross-sectional view of a printed wiring board mounting a circuit of an IH rice cooker according to an eleventh embodiment of the present invention.

FIG. 11 is a circuit diagram of an IH rice cooker according to a twelfth embodiment of the present invention.

FIG. 12 is a circuit diagram of a conventional IH rice cooker.

FIG. 13 is a circuit diagram of the IH rice cooker.

FIG. 14 is a diagram showing the relationship between the input voltage and the voltage across the switching element of the IH rice cooker.

[Explanation of symbols]

 1 Commercial Power Supply 2 Rectifier Circuit 3 Pan 4 Heating Coil 5 Resonance Capacitor 6 Switching Element 7 Inverter Circuit 8 Drive Circuit 9 Control Circuit 10 Current Detecting Means 11 Variable Resistor RY (Fifth Resistor) 14 Voltage Conversion Circuit 15 Resistor RB (First resistor) 16 Resistor RC (Second resistor) 17 Resistor RD (Third resistor) 18 Comparison circuit 21 Switch A (First switch) 22 Input current change switch 24 Resistor RH (Third resistor) 25 Relay (first switch) 29 Resistor RJ (fourth resistor) 34 Smoothing circuit 35 Resistor RK (sixth resistor) 36 Resistor RL (seventh resistor) ) 37 resistor RM (third resistor) 38 switch C (first switch) 39 input power change switch 40 resistor RN (third resistor) 41 printed wiring board 42 Solder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Shibata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Seiichi Takagura 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Hiroshi Fukuda 1006 Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd.

Claims (12)

[Claims] 1. A commercial power source, a rectifying circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifying circuit for heating a pan by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a current detection unit that detects an input current from the commercial power supply. And a voltage conversion circuit for converting the signal current output from the current detection means into a voltage,
A series connection of a first resistor and a second resistor for dividing the voltage output from the voltage conversion circuit; a disconnectable third resistor connected in parallel with the second resistor; And a control circuit for controlling the drive circuit, wherein the control circuit controls the drive circuit such that the voltage across the second resistor is always a predetermined voltage when the inverter circuit oscillates. vessel. 2. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifier circuit for heating a pot by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a current detection unit that detects an input current from the commercial power supply. And a voltage conversion circuit for converting the signal current output from the current detection means into a voltage,
A series connection of a first resistor and a second resistor for dividing the voltage output from the voltage conversion circuit, a third resistor and a first switch connected in parallel with the second resistor. Serial connection, an input current change switch for changing the input current from the commercial power supply, and a control circuit for controlling the drive circuit, the control circuit, in accordance with the input from the input current change switch An IH rice cooker configured to open and close the first switch and control the drive circuit such that the voltage across the second resistor is always a predetermined voltage when the inverter circuit oscillates. 3. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifier circuit for heating a pan by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a current detection unit that detects an input current from the commercial power supply. And a voltage conversion circuit for converting the signal current output from the current detection means into a voltage,
A disconnectable third resistor connected in parallel to the signal input side of the voltage conversion circuit and a control circuit for controlling the drive circuit are provided, and the control circuit performs the voltage conversion when the inverter circuit oscillates. An IH rice cooker in which the drive circuit is controlled so that the voltage output from the circuit is always a predetermined voltage. 4. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifier circuit for heating a pan by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a current detection unit that detects an input current from the commercial power supply. And a voltage conversion circuit for converting the signal current output from the current detection means into a voltage,
The third connected in parallel to the signal input side of this voltage conversion circuit
Connected in series with a resistor and a first switch, an input current change switch for changing an input current from the commercial power supply, and a control circuit for controlling the drive circuit, wherein the control circuit changes the input current. The IH is configured so that the first switch is opened and closed according to an input from the switch, and the drive circuit is controlled so that the voltage output from the voltage conversion circuit is always a predetermined voltage when the inverter circuit oscillates. rice cooker. 5. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifier circuit for heating a pot by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a current detection unit that detects an input current from the commercial power supply. And a voltage conversion circuit for converting the signal current output from the current detection means into a voltage,
An input current change switch for changing the input current from the commercial power supply, and a control circuit for controlling the drive circuit,
The control circuit controls the drive circuit such that the voltage output from the voltage conversion circuit during oscillation of the inverter circuit is always a predetermined reference voltage, and the reference voltage is input by the input current change switch. IH rice cooker which changes. 6. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifier circuit for heating a pot by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a fourth circuit that divides a voltage across the switching element. A series connection of a resistor and a fifth resistor, a smoothing circuit for converting the voltage across the fifth resistor into a smoothed voltage, and a sixth resistor for dividing the output voltage output from the smoothing circuit. A series connection of a seventh resistor and a disconnectable third connected in parallel with the seventh resistor.
And a control circuit for controlling the drive circuit. The control circuit controls the drive circuit so that the voltage across the seventh resistor is always a predetermined voltage when the inverter circuit oscillates. Controlled IH rice cooker. 7. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifier circuit for heating a pot by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a fourth circuit that divides a voltage across the switching element. A series connection of a resistor and a fifth resistor, a smoothing circuit for converting the voltage across the fifth resistor into a smoothed voltage, and a sixth resistor for dividing the output voltage output from the smoothing circuit. A series connection of a seventh resistor, a series connection of a third resistor and a first switch connected in parallel with the seventh resistor, and an input for changing an input current from the commercial power supply. A current change switch and a control circuit for controlling the drive circuit are provided, and the control circuit opens and closes the first switch by an input from the input current change switch, and the seventh circuit when the inverter circuit oscillates. IH rice cooker in which the drive circuit is controlled so that the voltage across the resistor is always a predetermined voltage. 8. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifier circuit for heating a pot by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a fourth circuit that divides a voltage across the switching element. A series connection of a resistor and a fifth resistor, a disconnectable third resistor connected in parallel to the fifth resistor, and a smoothing for converting a voltage across the fifth resistor into a smoothed voltage. A circuit and a control circuit for controlling the drive circuit, and the control circuit is configured so that the output voltage of the smoothing circuit is always a predetermined voltage when the inverter circuit oscillates. An IH rice cooker that controls the drive circuit. 9. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifier circuit for heating a pan by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a fourth circuit that divides a voltage across the switching element. The connection between the resistor and the fifth resistor, the third resistor and the first switch connected in series connected in parallel with the fifth resistor, and the voltage across the fifth resistor are smoothed. A smoothing circuit for converting into a voltage; an input current changing switch for changing an input current from the commercial power source; and a control circuit for controlling the drive circuit, wherein the control circuit is the An IH that opens and closes the first switch by an input from an input current change switch and controls the drive circuit so that the output voltage of the smoothing circuit is always a predetermined voltage when the inverter circuit oscillates.
rice cooker. 10. The impedance of the third resistor is higher than the impedance of the circuit connected in parallel with the third resistor, as claimed in any one of claims 1 to 4 and 6 to 9.
IH rice cooker according to the item. 11. The IH rice cooker according to any one of claims 1, 3, 6, and 8, wherein the third resistor is a lead terminal type resistor. 12. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a heating coil connected to the rectifier circuit for heating a pan by generating a high frequency magnetic field, and a resonance circuit together with the heating coil. An inverter circuit having a resonant capacitor and a switching element that is connected to the resonant circuit to generate a resonant current, a drive circuit that drives the switching element, and a fourth circuit that divides a voltage across the switching element. A resistor and a fifth resistor connected in series; a smoothing circuit that converts the voltage across the fifth resistor into a smoothed voltage; an input current change switch that changes the input current from the commercial power supply; A control circuit for controlling the circuit, wherein the control circuit ensures that the output voltage of the smoothing circuit is always a predetermined reference voltage when the inverter circuit oscillates. As described above, the IH rice cooker is configured to control the drive circuit and change the reference voltage by an input from the input current change switch.