JP3265912B2 - IH rice cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IH rice cooker having a switching element of an inverter circuit.

[0002]

2. Description of the Related Art In recent years, rice cookers controlled by microcomputers have become the mainstream in the market. At first, rice cookers such as chorochoro middle pappers are controlled so as to be able to cook ideal rice which has been said for a long time. In addition, a rice cooker that can cook rice more deliciously with higher power than a conventional sheathed heater system by using an IH heater system that applies the principle of induction heating as a heating source has attracted attention in the market.

[0003] However, the IH heater includes a heating coil, an inverter circuit for supplying a high-frequency current to the heating coil, and a switching element for switching the inverter circuit. There is a drawback that it is destroyed when it becomes. The technological progress of the current switching element has been improved to a level that can be achieved with ordinary rice cooking without using cooling means such as a fan motor under remarkably constant conditions, but the price is high, Under various conceivable conditions, self-heating may not be compensated for, and the temperature is reduced by a cooling means such as a fan motor. In addition, in order to protect the switching element when the fan motor does not rotate due to dust or the like and cannot cool down, a fan lock detecting function and a temperature detecting means using an NTC thermistor are provided. It is shown in FIG.

In FIG. 9, reference numeral 101 denotes a pot for accommodating rice or the like. A heating coil 102 is provided at the bottom of the pot 101. A high frequency current is supplied to the heating coil from an inverter circuit 104 including a switching element 103. The pan 101 is induction heated. An inverter driving circuit 105 drives the switching element 103 by a signal from the control unit 106. A fan motor 107 cools the switching element 103. Reference numeral 108 denotes a fan motor drive circuit, which receives a signal from the
7 is driven. An NTC thermistor 109 for detecting the temperature of the switching element 103 is connected to the control means 106 via an A / D converter 110. A power supply circuit 111 includes an inverter drive circuit 105 and a control unit 10.
6 and a fan motor drive circuit 108. An AC power supply 112 supplies power to the inverter circuit 104, the power supply circuit 111, and the fan motor 107. Reference numeral 113 denotes a diode bridge for performing full-wave rectification on the AC power supply 112 and supplying power to the inverter circuit 104. Reference numerals 114a and 114b denote the AC power supply 112.
And first and second diodes that perform full-wave rectification and supply power to the power supply circuit 111.

In the above-described IH rice cooker, when dust or the like adheres to the fan motor 107 and the number of revolutions drops or the cooling air intake port is blocked and sufficient cooling cannot be performed, the temperature of the switching element 103 rises. Leading to destruction,
When the temperature is detected by the NTC thermistor 109 and the control means 106 determines via the A / D converter 110 that the temperature is abnormal, the drive signal to the inverter drive circuit 105 is stopped, the switching of the switching element 103 is stopped, and self-heating occurs. Was stopped.

[0008] In FIG. 10, only parts different from FIG. 9 will be described. Reference numeral 115 denotes a fan motor having a fan lock detection function, and outputs a fan lock detection signal to the control means 106. The power supply circuit 111 supplies a DC voltage to the inverter drive circuit 105, the control means 106, the fan motor drive circuit 108b, and the fan motor 115. An AC power supply 112 supplies power to the inverter circuit 104 and the power supply circuit 111.

In the case of this configuration, the NTC thermistor 10
9 and fan motor 11 without A / D converter 110
When the fan lock signal is input to the control means 106 from step 5, the drive signal to the inverter drive circuit 105 is stopped, the switching of the switching element 103 is stopped, and self-heating is stopped.

[0008]

However, the conventional configuration of I
The H rice cooker requires a circuit of an NTC thermistor 109 and an A / D converter 110 for detecting the temperature of the switching element 103, and the cost is increased by providing a lock detection function to the fan motor 115, and the detection is also performed. An input means (input terminal) for inputting a signal to the control means 106 is required, which has a problem that not only the circuit becomes complicated, but also the input / output terminals of the control means are restricted and the cost is increased.

Another problem is that when the fan motor is constantly operating during rice cooking, wind noise and rotation noise of the motor are likely to be generated.

[0010] The present invention solves the above-mentioned conventional problems, and uses a simple configuration when an abnormality occurs in the cooling means.
When an abnormality is detected, the operation of the inverter circuit stops,
It is important to properly prevent the destruction of parts such as
It is the purpose of 1.

A second object of the present invention is to notify a user of an abnormality of a rice cooker so that the user can take appropriate measures.

A third object of the present invention is to control the switching state of the switching element by the state of the PTC thermistor element without depending on the state of the AC power supply depending on the state of the power supply circuit, and to prevent the destruction of the element. It is to prevent it effectively.

A fourth object of the present invention is to provide a means for preventing a heat-generating component from being broken under any condition.

A fifth object of the present invention is to stop the rotation of the fan motor irrespective of the state of the AC power supply depending on the state of the power supply circuit to eliminate noise and wasteful power consumption.

A sixth object of the present invention is to stop the operation of the inverter drive circuit before the switching element exceeds the guaranteed temperature, especially for the components mounted on the printed wiring board, and to effectively prevent the switching element from being destroyed. And

[0016]

Means for Solving the Problems A first means for solving problems of the present invention for achieving the above first object, a pot inner housing the rice or the like, a heating coil for heating the inner pot, wherein An inverter circuit for supplying a high-frequency current to the heating coil, a switching element for switching the inverter circuit, a drive circuit for driving the switching element, control means for controlling the drive circuit to control rice cooking, and at least the control means a power supply circuit for supplying a DC voltage, the small
At least a power supply for supplying power to the inverter circuit and the power supply circuit, a PTC thermistor element whose resistance value rapidly increases when the temperature of the element rises above a certain level, and a switch.
Cooling means for cooling heat-generating components such as
And a cooling means driving circuit for driving the cooling means.
The C thermistor element is located between the AC power supply and the power supply circuit.
Are connected, previous said cooling means outside the normal cooling range Symbol
When the ambient temperature of the PTC thermistor element becomes high,
The power supply from the C power supply to the power supply circuit is stopped.

Further, a second object of the present invention for achieving the second object is to provide an inner pot containing rice or the like,
A heating coil for heating the inner pan, and a high
Inverter circuit for supplying frequency current and this inverter
A switching element for switching a circuit and this switch
A driving circuit for driving the switching element;
Control means for controlling rice cooking by controlling
A power supply circuit for supplying a DC voltage to
AC for supplying power to the inverter circuit and the power supply circuit
When the temperature of the power supply and the element rises above a certain level, the resistance value sharply increases.
PTC thermistor element and switching element
Display means for displaying an abnormal state of the heat generating components etc., and the zero volt pulse generating circuit for generating a pulse in the vicinity zero volt AC power, a low voltage detection circuit voltage of the power supply circuit detects that the decreased , The PTC thermistor element is
An AC power supply connected to the power supply circuit;
-When the ambient temperature of the
Stops power supply to al the power supply circuit, the control means according to a combination of the detection signal of the detection signal and the low-voltage detection circuit of the zero-volt pulse generating circuit, displaying the abnormal state on the display means Through the drive circuit
It is obtained so as to stop switching of the switching element Te.

The third object of the present invention for achieving the third object is to provide a display device for notifying a state of a rice cooker in the second object device and the drive circuit. Control means for performing rice cooking control and operating the display element; a zero volt pulse generating circuit for generating a pulse near zero volt of the AC power supply and supplying the pulse signal to the control means; A low-voltage detection circuit for detecting a decrease in the voltage; and when the voltage of the power supply circuit decreases , generation of a pulse signal supplied from the zero-volt pulse generation circuit to the control means is stopped.
When the pulse signal from the zero volt pulse generation circuit is not input, the control unit displays an abnormal state on the display unit and switches the switching element via the drive circuit. Is to be stopped.

Further, the fourth fourth means for solving problems of the present invention for achieving the object of the cooling for cooling the heat generating components such as switching elements have contact with the second means for solving problems <br/> and means, and cooling means driving circuit for driving the cooling unit
The control means includes a detection signal of the zero volt pulse generation circuit .
No. and respond to the combination of the detection signal of the low-voltage detection circuit
In addition, an abnormal state is displayed on the display means, and the cooling means is driven via a cooling means drive circuit.

The fifth object of the present invention for achieving the fifth object is to provide a cooling means for cooling a heat-generating component such as a switching element in the fourth object means, A cooling means driving circuit for driving the
Control means for controlling the drive circuit and the cooling means drive circuit to perform rice cooking control; a zero volt pulse generation circuit for generating a pulse near zero volt of the AC power supply and supplying the pulse signal to the control means; A low-voltage detection circuit for detecting a drop in the voltage of the power supply circuit , wherein the power supply circuit
When the voltage of the zero-voltage pulse generation circuit
Stopping the generation of the pulse signal supplied to the control means.
With such a configuration, the control unit performs the display when the pulse signal from the zero volt pulse generation circuit is not input.
In addition to displaying an abnormal condition on the cooling means ,
In this configuration, the cooling means is driven via the cooling means .

According to a sixth aspect of the present invention for achieving the sixth object, the PTC thermistor element according to the first to fifth aspects is arranged near the switching element. It is.

[0022]

In the first means for solving the problems, an inverter circuit is provided.
During oscillation, various heat-generating components such as switching elements
Even under conditions (for example, continuous rice cooking)
In a configuration where cooling is performed using cooling means,
Resistance value hardly changes at normal cooling temperature
Above a certain temperature that does not exceed the guaranteed temperature of parts such as switching elements
When the temperature rises, the PTC is set so that the resistance value increases rapidly.
By selecting the characteristics of the thermistor, the cooling means
If the PTC thermistor cannot be cooled sufficiently due to an abnormality, the resistance of the PTC thermistor increases. Since the PTC thermistor element is connected between the AC power supply and a power supply circuit that supplies a DC voltage to the control means, the AC power supply is not supplied to the power supply circuit, and the power supply circuit cannot supply the DC voltage to the control means. Therefore, since the control means does not operate, the drive signal cannot be supplied to the drive circuit, and the oscillation of the inverter circuit stops.

In the second means for solving the above problems, the inverter circuit oscillates during the cooking of rice, the temperature of the heat-generating components such as the switching elements rises, raising the atmosphere of the components inside the body, and the PTC thermistor element is also warmed. By selecting the characteristics of the PTC thermistor element so that the resistance value increases when the temperature of the PTC thermistor element exceeds a certain temperature which does not exceed the guaranteed temperature of the parts such as the switching element, the temperature of the heat generating parts such as the switching element is reduced. Abnormal rise P
The resistance value of the TC thermistor element increases. And this P
Since the TC thermistor element is connected between the AC power supply and a power supply circuit that supplies a DC voltage to the control means, the AC power is not sufficiently supplied to the power supply circuit, and the voltage of the power supply circuit decreases. Then, the power failure detection circuit detects that the voltage of the power supply circuit has dropped, and outputs a detection signal to the control means. On the other hand, since the pulse signal is normally output from the zero volt pulse generation circuit to the control means, the control means abnormally raises the temperature of the heat-generating components such as the switching elements until the voltage of the power supply circuit is completely reduced and the operation is stopped. Then, the abnormality is displayed on the display means and the oscillation of the inverter circuit is stopped.

In the third means for solving the above problems, the inverter circuit oscillates during rice cooking, the temperature of the heat-generating components such as the switching elements rises, raising the atmosphere of the components inside the body, and the PTC thermistor element is also warmed. By selecting the characteristics of the PTC thermistor element so that the resistance value increases when the temperature of the PTC thermistor element exceeds a certain temperature which does not exceed the guaranteed temperature of the parts such as the switching element, the temperature of the heat generating parts such as the switching element is reduced. Abnormal rise P
The resistance value of the TC thermistor element increases. And this P
Since the TC thermistor element is connected between the AC power supply and a power supply circuit that supplies a DC voltage to the control means, the AC power is not sufficiently supplied to the power supply circuit, and the voltage of the power supply circuit decreases. The control means detects that the voltage of the power supply circuit has dropped and cuts off the pulse signal supplied from the zero volt pulse generation circuit to the control means. By this time, it is determined that the temperature of the heat-generating component such as the switching element has risen abnormally, the abnormality is displayed on the display means, and the oscillation of the inverter circuit is stopped.

In the fourth means for solving the above-mentioned problems, the inverter circuit oscillates during the cooking of rice, the temperature of the heat-generating components such as the switching elements rises, the atmosphere of the components inside the body is raised, and the PTC thermistor element is also warmed. By selecting the characteristics of the PTC thermistor element so that the resistance value increases when the temperature of the PTC thermistor element exceeds a certain temperature which does not exceed the guaranteed temperature of the parts such as the switching element, the temperature of the heat generating parts such as the switching element is reduced. Abnormal rise P
The resistance value of the TC thermistor element increases. And this P
Since the TC thermistor element is connected between the AC power supply and a power supply circuit that supplies a DC voltage to the control means, the AC power is not sufficiently supplied to the power supply circuit, and the voltage of the power supply circuit decreases. Then, the power failure detection circuit detects that the voltage of the power supply circuit has dropped, and outputs a detection signal to the control means. On the other hand, since the pulse signal is normally output from the zero volt pulse generation circuit to the control means, the control means abnormally raises the temperature of the heat-generating components such as the switching elements until the voltage of the power supply circuit is completely reduced and the operation is stopped. Display means
And outputs a signal for driving the cooling means to the cooling means drive circuit to operate the cooling means.

In the fifth means for solving the above problems, the inverter circuit oscillates during the cooking of rice, the temperature of the heat-generating components such as the switching elements rises, raising the atmosphere of the components inside the housing, and the PTC thermistor element is also warmed. By selecting the characteristics of the PTC thermistor element so that the resistance value increases when the temperature of the PTC thermistor element exceeds a certain temperature which does not exceed the guaranteed temperature of the parts such as the switching element, the temperature of the heat generating parts such as the switching element is reduced. Abnormal rise P
The resistance value of the TC thermistor element increases. And this P
Since the TC thermistor element is connected between the AC power supply and a power supply circuit that supplies a DC voltage to the control means, the AC power is not sufficiently supplied to the power supply circuit, and the voltage of the power supply circuit decreases. The control means detects that the voltage of the power supply circuit has dropped and cuts off the pulse signal supplied from the zero volt pulse generation circuit to the control means. By this time, it is determined that the temperature of the heat-generating component such as the switching element has risen abnormally, the abnormality is displayed on the display means, and a signal for driving the cooling means is output to the cooling means drive circuit to operate the cooling means.

In the sixth means for solving the above problems, the PTC thermistor element whose characteristics are selected so that the resistance value increases when the temperature exceeds a certain temperature which does not exceed the guaranteed temperature of the components such as the switching element, generates the most self-heating when the inverter oscillates. By placing the switching element near a switching element requiring a large temperature and requiring temperature control, the switching element can be protected from destruction due to heat generation.

[0028]

(Embodiment 1) One embodiment of the first means for solving the problems of the present invention is shown in FIGS.
2 will be described. In FIG. 1, reference numeral 1 denotes a pot for accommodating rice or the like. A heating coil 2 is arranged at the bottom of the pot 1. A high-frequency current is supplied to the heating coil 2 from an inverter circuit 4 including a switching element 3. Heats the pot 1 by induction. Reference numeral 5 denotes an inverter driving circuit which drives the switching element 3 by a signal from a control means 6 such as a microcomputer. A power supply circuit 7 supplies a DC voltage to the inverter drive circuit 5 and the control means 6.
Reference numeral 8 denotes an AC power supply, which supplies power to the inverter circuit 4 and the power supply circuit 7. Reference numeral 9 denotes a diode bridge that performs full-wave rectification on the AC power supply 8 and supplies power to the inverter circuit 4. Reference numerals 10a and 10b denote first and second diodes which perform full-wave rectification on the AC power supply 8 and supply power to the power supply circuit 7. Reference numeral 11 denotes a PTC thermistor, and the first and second diodes 10a and 10b and the power supply circuit 7
Connected between As shown in FIG. 2, the PTC thermistor 11 is an element whose resistance value rapidly increases when the temperature of the element rises above a certain level. The switching element 3, the inverter circuit 4, the power supply circuit 7, and the diode bridge 9
And the first and second diodes 10a and 10b are mounted on the same printed wiring board (not shown).

In the IH rice cooker thus configured, when rice cooking is started, a drive signal is sent to the inverter drive circuit 5 according to the program in which the control means 6 is incorporated, and the switching element 3 is driven to oscillate the inverter circuit 4. Let it. At that time, the switching element 3 self-heats due to a loss at the time of conduction or a switching loss generated when switching from off to on and from on to off. In addition, the rated current consumption (about 12 A) of the rice cooker flows through the diode bridge 9 and self-heats with a loss corresponding to the product of the forward voltage and the rice cooker itself generates heat when cooking rice, causing the PTC thermistor 11 to generate heat. Raise the ambient temperature of the mounted printed wiring board. On the other hand, the PTC thermistor 11 itself also has a resistance value (about 40Ω at low temperature),
And the current supplied to the power supply circuit 7 via the second diodes 10a and 10b (current supplied from the power supply circuit to the control means 6 and the inverter drive circuit 5) to generate heat. When the rice cooker is used in a normal state, the temperature rise of the PTC thermistor 11 is designed to be about 70 ° C. to 80 ° C. Therefore, in this state, the resistance value of the PTC thermistor 11 remains at low temperature (40
Ω to 50Ω). The temperature rises of the switching element 3 and the diode bridge 9 are lower than the respective guaranteed temperatures (125 ° C. to 150 ° C. for semiconductor components).

On the other hand, when the temperature of the place where the rice cooker is placed is continuously high or where the rice cooker is abnormally high, the ambient temperature of the printed wiring board rises more than usual, and the temperature of the switching element 3 and the diode bridge 9 rises. May exceed the guaranteed temperature, in which case the parts exceeding the guaranteed temperature will be destroyed. Therefore, the components mounted on the printed wiring board do not exceed the guaranteed temperature,
The characteristics of the PTC thermistor 11 are selected so that the resistance value rapidly increases at a temperature higher than about (° C. to 80 ° C.) (about 100 ° C. in FIG. 2).

When the temperature of the PTC thermistor 11 is going to exceed 100 ° C. due to the above-mentioned abnormality,
As the resistance value increases, the first and second
The current supplied to the power supply circuit 7 via the diodes 10a and 10b is limited, the power supply circuit 7 cannot output a normal voltage, and the control means 6 and the inverter drive circuit 5 do not operate. Therefore, switching element 3 stops switching and stops oscillation of inverter circuit 4.

As described above, when continuous rice cooking is performed repeatedly or when the temperature of the place where the rice cooker is placed becomes abnormally high or the temperature on the printed wiring board rises more than usual, Before the components mounted on the printed wiring board exceed the guaranteed temperature, the resistance value of the PTC thermistor 11 increases and the operation of the inverter circuit 4 stops, so that the temperature does not rise further and the components do not break.

[0033] (Example 2) In addition there will be described only differs from that of Figure 1 by 3 parts of an embodiment of a first means for solving problems of the present invention. FIG.
Numeral 12 denotes a fan motor for cooling heat generating components such as the switching element 3, the inverter circuit 4, and the diode bridge 9. A fan motor drive circuit 13 drives the fan motor 12 based on a signal from the control unit 6. Reference numeral 7 denotes a power supply circuit, and an inverter drive circuit 5
The DC voltage is supplied to the control means 6 and the fan motor drive circuit 13. Reference numeral 8 denotes an AC power supply, which supplies power to the inverter circuit 4, the power supply circuit 7, and the fan motor 12.

In the IH rice cooker thus configured, when rice cooking is started, a drive signal is sent to the inverter drive circuit 5 according to the program in which the control means 6 is incorporated, and the switching element 3 is driven to oscillate the inverter circuit 4. At the same time, a drive signal is sent to the fan motor drive circuit 13 to rotate the fan motor 12. When the fan motor 12 is operating normally, the temperature rise of the PTC thermistor 11 is designed to be about 70 ° C. to 80 ° C. no matter what conditions the rice cooker is used. Therefore, in this state, the resistance value of the PTC thermistor 11 remains at a low temperature (40Ω to 50Ω). The temperature rises of the switching element 3 and the diode bridge 9 are lower than the respective guaranteed temperatures (125 ° C. to 150 ° C. for semiconductor components).

However, when the fan motor 12 is attached with debris or gets caught in the fan motor 12 and the number of revolutions of the fan motor 12 drops or stops, and the components cannot be cooled sufficiently, the ambient temperature of the printed wiring board is usually increased. The temperature of the switching element 3 and the diode bridge 9 exceeds the guaranteed temperature, and the components are destroyed. Therefore, the characteristics of the PTC thermistor 11 are selected so that the components mounted on the printed wiring board do not exceed the guaranteed temperature and the resistance value rapidly increases at a temperature higher than normal (about 70 ° C. to 80 ° C.). (About 100 ° C. in FIG. 2).

When the temperature of the PTC thermistor 11 is going to exceed 100 ° C. due to the above-mentioned abnormality,
As the resistance value increases, the first and second
The current supplied to the power supply circuit 7 via the diodes 10a and 10b is limited, the power supply circuit 7 cannot output a normal voltage, and the control means 6 and the inverter drive circuit 5 do not operate. Therefore, switching element 3 stops switching and stops oscillation of inverter circuit 4.

As described above, when an abnormality occurs in the fan motor 12 and the components cannot be cooled sufficiently, the components mounted on the printed wiring board are required to reach P
The resistance value of the TC thermistor 11 increases and the inverter circuit 4
Since the operation is stopped, the temperature does not rise any more and the parts are not broken.

[0038] (Example 3) further, an embodiment of the first means for solving problems of the present invention FIG. 4
Only the parts different from FIG. 1 will be described. In FIG. 4, reference numeral 15 denotes a fan motor for cooling the heating elements such as the switching element 3 and the inverter circuit 4 and the diode bridge 9.
It operates using the voltage C as a power supply. Reference numeral 16 denotes a fan motor drive circuit, which drives the fan motor 15 by a signal from the control means 6 including a microcomputer or the like. Reference numeral 7 denotes a power supply circuit, which supplies a DC voltage to the inverter drive circuit 5, the control means 6, the fan motor 15, and the fan motor drive circuit 16.

In the IH rice cooker thus configured, when rice cooking is started, a drive signal is sent to the inverter drive circuit 5 in accordance with the program in which the control means 6 is incorporated to drive the switching element 3 to oscillate the inverter circuit 4. At the same time, a drive signal is sent to the fan motor drive circuit 16 to rotate the fan motor 15. When the fan motor 15 is operating normally, the temperature rise of the PTC thermistor 11 is designed to be about 70 ° C. to 80 ° C. no matter what conditions the rice cooker is used. Therefore, in this state, the resistance value of the PTC thermistor 11 remains at a low temperature (40Ω to 50Ω). The temperature rises of the switching element 3 and the diode bridge 9 are lower than the respective guaranteed temperatures (125 ° C. to 150 ° C. for semiconductor components).

However, dust adheres to the fan motor 15 or an object gets caught, so that the rotation speed of the fan motor 15 decreases or stops. Since the fan motor 15 is a load having an inductance component, when rotation is stopped, the current consumption increases sharply, and the current flowing through the PTC thermistor 11 increases. PTC thermistor 11
Has a resistance value, so as the flowing current increases, the loss increases and the self-temperature rise increases. On the other hand, if the components cannot be cooled sufficiently, the ambient temperature of the printed wiring board rises more than usual, and the temperatures of the switching element 3 and the diode bridge 9 exceed the guaranteed temperatures, and the components are destroyed. Therefore, the temperature (70 ° C.-
(About 80 ° C.), the resistance does not increase and the fan motor 15
The PTC thermistor 1 prevents the resistance value from suddenly increasing at a temperature that rises when the current increases when the current is increased, and does not exceed the guaranteed temperature of the components mounted on the printed wiring board.
1 is selected (about 100 ° C. in FIG. 2).

When the temperature of the PTC thermistor 11 increases due to the above-mentioned abnormality and the temperature rises to exceed 100 ° C., the resistance increases, and the first and second AC power sources 8 increase the resistance. 2 diode 10
The current supplied to the power supply circuit 7 through the terminals a and b is limited, so that the power supply circuit 7 cannot output a normal voltage, and the control means 6 and the inverter drive circuit 5 do not operate. Therefore, switching element 3 stops switching and stops oscillation of inverter circuit 4.

As described above, when an abnormality occurs in the fan motor 15 and the components cannot be cooled sufficiently, the temperature of the PTC thermistor 11 increases due to the increased current, the resistance value increases, and the PTC thermistor 11 is mounted on the printed wiring board. Since the operation of the inverter circuit 4 is stopped before the temperature of the component exceeds the guaranteed temperature, the temperature does not further rise and the component is not destroyed.

(Embodiment 4) Next, an embodiment of the second problem solving means of the present invention will be described with reference to FIG. FIG.
At 17, full-wave rectification of the AC voltage waveform of the AC power supply 8 is performed, and HI is applied near zero volts, and LOW is applied at other potentials.
Is a zero volt pulse generation circuit for supplying the pulse signal to the control means 6. Reference numeral 7 denotes a power supply circuit, which is connected to the inverter drive circuit 5, the control means 6, and the zero volt pulse generation circuit 17 by DC.
Supplying voltage. Reference numeral 8 denotes an AC power supply, which supplies power to the inverter circuit 4, the power supply circuit 7, and the zero volt pulse generation circuit 17. Reference numeral 18 denotes a DC voltage output from the power supply circuit 7, and when the DC voltage falls below a certain level, the control unit 6 receives the DC voltage.
Is a blackout detection circuit that outputs a LOW signal. 19
Is a display means, which receives the output from the control means 6 and displays the state of the rice cooker. Further, the control means 6 receives output signals from the zero volt pulse generation circuit 17 and the low voltage detection circuit 18 and checks the state of the DC voltage of the AC power supply 8 and the power supply circuit 11.

In the IH rice cooker thus configured, when rice cooking is started, a drive signal is sent to the inverter drive circuit 5 according to the program in which the control means 6 is incorporated, and the switching element 3 is driven to oscillate the inverter circuit 4. At the same time, the state of the IH rice cooker is output to the display means 19. At that time, the switching element 3 self-heats due to a loss at the time of conduction or a switching loss generated when switching from off to on and from on to off. In addition, the rated current consumption (about 12 A) of the rice cooker flows through the diode bridge 9 and self-heats with a loss corresponding to the product of the forward voltage and the rice cooker itself generates heat when cooking rice, causing the PTC thermistor 11 to generate heat. Raise the ambient temperature of the mounted printed wiring board. On the other hand, the PTC thermistor 11 itself also has a resistance value (about 40Ω at low temperature),
And the current supplied to the power supply circuit 7 via the second diodes 10a and 10b (current supplied from the power supply circuit to the control means 6 and the inverter drive circuit 5) to generate heat. When the rice cooker is used in a normal state, the temperature rise of the PTC thermistor 11 is designed to be about 70 ° C. to 80 ° C. Therefore, in this state, the resistance value of the PTC thermistor 11 remains at low temperature (40
Ω to 50Ω). The temperature rises of the switching element 3 and the diode bridge 9 are lower than the respective guaranteed temperatures (125 ° C. to 150 ° C. for semiconductor components).

On the other hand, when the temperature of a place where a rice cooker is placed is continuous continuous rice cooking or a rice cooker is abnormally high, the ambient temperature of the printed wiring board rises more than usual, and the temperature of the switching element 3 and the diode bridge 9 increases. May exceed the guaranteed temperature, in which case the parts exceeding the guaranteed temperature will be destroyed. Therefore, the components mounted on the printed wiring board do not exceed the guaranteed temperature,
The characteristics of the PTC thermistor 11 are selected so that the resistance value rapidly increases at a temperature higher than about (° C. to 80 ° C.) (about 100 ° C. in FIG. 2).

When the temperature of the PTC thermistor 11 is going to exceed 100 ° C. due to the above-mentioned abnormality,
As the resistance value increases, the first and second
The current supplied to the power supply circuit 7 via the diodes 10a and 10b is limited, and the power supply circuit 7 cannot output a normal voltage. The low voltage detection circuit 18 detects a drop in the DC voltage and outputs a detection signal to the control means 6. The control means 6 includes a zero volt pulse generation circuit 17.
Is normal and the signal from the low-voltage detection circuit 18 is abnormal, it is determined that the temperature near the printed wiring board on which the components are mounted has become abnormally high, and the oscillation stop signal is sent to the inverter drive circuit 5. A signal is output to stop the switching of the switching element 3 to stop the oscillation of the inverter circuit 4 and to display on the display means 19 that the temperature in the IH rice cooker is abnormal.

As described above, in the case where rice is repeatedly cooked, the temperature of the place where the rice cooker is placed becomes abnormally high, or the temperature on the printed wiring board rises more than usual, Before the components mounted on the printed wiring board exceed the guaranteed temperature, the resistance value of the PTC thermistor 11 increases, and the operation of the inverter circuit 4 stops. In addition, the user can be notified of the abnormality of the IH rice cooker.

(Embodiment 5) Next, an embodiment of the third problem solving means of the present invention will be described with reference to FIG. FIG.
At 17, full-wave rectification of the AC voltage waveform of the AC power supply 8 is performed, and HI is applied near zero volts, and LOW is applied at other potentials.
Is a zero volt pulse generation circuit for supplying the pulse signal to the control means 6. Reference numeral 7 denotes a power supply circuit, which is connected to the inverter drive circuit 5, the control means 6, and the zero volt pulse generation circuit 17 by DC.
Supplying voltage. Reference numeral 8 denotes an AC power supply, which includes an inverter circuit 4, a power supply circuit 7, and a zero volt pulse generation circuit 1.
7 is supplied with electric power. Reference numeral 18 denotes a stop voltage detecting circuit which receives a DC voltage potential output from the power supply circuit 7 and cuts off a pulse signal supplied from the zero volt pulse generating circuit 17 to the control means 6 when the DC voltage falls below a certain potential. Reference numeral 19 denotes a display unit which receives the output from the control unit 6 and displays the state of the rice cooker. The control means 6 receives a pulse signal from the zero volt pulse generation circuit 17 and checks the voltage state of the AC power supply 8.

In the IH rice cooker thus configured, when rice cooking is started, a drive signal is sent to the inverter drive circuit 5 according to the program in which the control means 6 is incorporated to drive the switching element 3 to oscillate the inverter circuit 4. At the same time, the state of the IH rice cooker is output to the display means 19. At that time, the switching element 3 self-heats due to a loss at the time of conduction or a switching loss generated when switching from off to on and from on to off. In addition, the rated current consumption (about 12 A) of the rice cooker flows through the diode bridge 9 and self-heats with a loss corresponding to the product of the forward voltage and the rice cooker itself generates heat when cooking rice, causing the PTC thermistor 11 to generate heat. Raise the ambient temperature of the mounted printed wiring board. On the other hand, the PTC thermistor 11 itself also has a resistance value (about 40Ω at low temperature),
And the current supplied to the power supply circuit 7 via the second diodes 10a and 10b (current supplied from the power supply circuit to the control means 6 and the inverter drive circuit 5) to generate heat. When the rice cooker is used in a normal state, the temperature rise of the PTC thermistor 11 is designed to be about 70 ° C. to 80 ° C. Therefore, in this state, the resistance value of the PTC thermistor 11 remains at low temperature (40
Ω to 50Ω). The temperature rises of the switching element 3 and the diode bridge 9 are lower than the respective guaranteed temperatures (125 ° C. to 150 ° C. for semiconductor components).

On the other hand, when the temperature of the place where a rice cooker is continuously placed or where rice is repeatedly cooked is abnormally high, the ambient temperature of the printed wiring board rises more than usual, and the temperature of the switching element 3 and the diode bridge 9 increases. May exceed the guaranteed temperature, in which case the parts exceeding the guaranteed temperature will be destroyed. Therefore, the components mounted on the printed wiring board do not exceed the guaranteed temperature,
The characteristics of the PTC thermistor 11 are selected so that the resistance value rapidly increases at a temperature higher than about (° C. to 80 ° C.) (about 100 ° C. in FIG. 2).

When the temperature of the PTC thermistor 11 is going to exceed 100 ° C. due to the above-mentioned abnormality,
As the resistance value increases, the first and second
The current supplied to the power supply circuit 7 via the diodes 10a and 10b is limited, and the power supply circuit 7 cannot output a normal voltage. A low voltage detection circuit 18 detects a drop in DC voltage and generates a zero volt pulse generation circuit 17.
To the control means 6 is interrupted. When the pulse signal from the zero volt pulse generation circuit 17 is interrupted while the DC voltage is supplied from the power supply circuit 7, the control means 6 abnormally increases the temperature near the printed wiring board on which the components are mounted. And outputs a stop signal to the inverter drive circuit 5 to stop the oscillation of the inverter circuit 4 by stopping the switching of the switching element 3 and the display means 19 to indicate that the temperature in the IH rice cooker is abnormal. The signal for displaying is output.

As described above, when continuous rice cooking is performed repeatedly, or when the temperature of the place where the rice cooker is placed becomes abnormally high or the temperature on the printed wiring board rises more than usual, Before the components mounted on the printed wiring board exceed the guaranteed temperature, the resistance value of the PTC thermistor 11 increases, and the operation of the inverter circuit 4 stops. In addition, the user can be notified of the abnormality of the IH rice cooker.

(Embodiment 6) Next, an embodiment of the fourth problem solving means of the present invention will be described with reference to FIG. FIG.
Numeral 12 denotes a fan motor for cooling heat generating components such as the switching element 3, the inverter circuit 4, and the diode bridge 9. Reference numeral 13 denotes a fan motor drive circuit, which drives the fan motor 12 by a signal from the control means 6 including a microcomputer or the like. 17 is AC
This is a zero volt pulse generation circuit that supplies a pulse signal of HI at near zero volt and LOW at other potentials to the control means 6 after full-wave rectification of the AC voltage waveform of the power supply 8. Reference numeral 7 denotes a power supply circuit, which includes an inverter drive circuit 5, a control means 6, a fan motor drive circuit 13, and a zero volt pulse generation circuit 1.
7 is supplied with a DC voltage. Reference numeral 8 denotes an AC power supply, and the inverter circuit 4, the power supply circuit 7, and the fan motor 12
And a zero volt pulse generating circuit 17.
Reference numeral 18 denotes a stop voltage detecting circuit which receives the DC voltage potential output from the power supply circuit 7 and outputs a LOW signal to the control means 6 when the DC voltage falls below a certain potential. Control means 6
Input the output signals from the zero volt pulse generation circuit 17 and the low voltage detection circuit 18 and supply the DC power of the AC power supply 8 and the power supply circuit 11
Checking the voltage status.

In the IH rice cooker thus configured, when rice cooking is started, a drive signal is sent to the inverter drive circuit 5 according to the program in which the control means 6 is incorporated, and the switching element 3 is driven to oscillate the inverter circuit 4. Let it. At that time, the switching element 3 self-heats due to a loss at the time of conduction or a switching loss generated when switching from off to on and from on to off. In addition, the rated current consumption (about 12 A) of the rice cooker flows through the diode bridge 9 and self-heats with a loss corresponding to the product of the forward voltage and the rice cooker itself generates heat when cooking rice, causing the PTC thermistor 11 to generate heat. Raise the ambient temperature of the mounted printed wiring board. On the other hand, the PTC thermistor 11 itself also has a resistance value (about 40Ω at low temperature),
And the current supplied to the power supply circuit 7 via the second diodes 10a and 10b (current supplied from the power supply circuit to the control means 6 and the inverter drive circuit 5) to generate heat. When the rice cooker is used in a normal state, the temperature rise of the PTC thermistor 11 is designed to be about 70 ° C. to 80 ° C. Therefore, in this state, the resistance value of the PTC thermistor 11 remains at low temperature (40
Ω to 50Ω). The temperature rises of the switching element 3 and the diode bridge 9 are lower than the respective guaranteed temperatures (125 ° C. to 150 ° C. for semiconductor components).

On the other hand, when the temperature of the place where the rice cooker is placed is continuous abnormal rice cooker or the rice cooker is abnormally high, the ambient temperature of the printed wiring board rises more than usual, and the temperature of the switching element 3 and the diode bridge 9 increases. May exceed the guaranteed temperature, in which case the parts exceeding the guaranteed temperature will be destroyed. Therefore, the components mounted on the printed wiring board do not exceed the guaranteed temperature,
The characteristics of the PTC thermistor 11 are selected so that the resistance value rapidly increases at a temperature higher than about (° C. to 80 ° C.) (about 100 ° C. in FIG. 2).

When the temperature of the PTC thermistor 11 is going to exceed 100 ° C. due to the above-mentioned abnormality,
As the resistance value increases, the first and second
The current supplied to the power supply circuit 7 via the diodes 10a and 10b is limited, and the power supply circuit 7 cannot output a normal voltage. The low voltage detection circuit 18 detects a drop in the DC voltage and outputs a detection signal to the control means 6. The control means 6 includes a zero volt pulse generation circuit 17.
Is normal and the signal from the low voltage detection circuit 18 is abnormal, it is determined that the temperature near the printed wiring board on which the components are mounted has become abnormally high, and a drive signal is output to the fan motor drive circuit 13. Then, the fan motor 12 is operated.

As described above, in the normal state, the fan motor 12 does not operate, and when the rice cooker repeats the rice cooker, the temperature of the place where the rice cooker is placed becomes abnormally high, or the printed circuit board is overheated. If the temperature rises above normal, the fan motor 12 operates before the components mounted on the printed wiring board exceed the guaranteed temperature and cools the components, causing the temperature to rise further and destroying the components. In addition to the above, noise during rotation of the fan motor in a normal use state can be eliminated.

(Embodiment 7) Next, an embodiment of the fifth problem solving means of the present invention will be described with reference to FIG. FIG.
Numeral 12 denotes a fan motor for cooling heat generating components such as the switching element 3, the inverter circuit 4, and the diode bridge 9. Reference numeral 13 denotes a fan motor drive circuit, which drives the fan motor 12 based on a signal from the control unit 6 which is a control unit. Reference numeral 17 denotes a zero volt pulse generation circuit which supplies a full-wave rectified AC voltage waveform of the AC power source 8 to the control means 6 at a voltage near zero volts and supplies a LOW pulse signal at other potentials. 7 is a power supply circuit,
A DC voltage is supplied to the inverter drive circuit 5, the control means 6, the fan motor drive circuit 13, and the zero volt pulse generation circuit 17. Reference numeral 8 denotes an AC power supply, which supplies power to the inverter circuit 4, the power supply circuit 7, the fan motor 12, and the zero volt pulse generation circuit 17. Reference numeral 18 denotes a stop voltage detecting circuit which receives a DC voltage potential output from the power supply circuit 7 and cuts off a pulse signal supplied from the zero volt pulse generating circuit 17 to the control means 6 when the DC voltage falls below a certain potential. The control means 6 receives a pulse signal from the zero volt pulse generation circuit 17 and checks the voltage state of the AC power supply 8.

In the thus constructed IH rice cooker, when rice cooking is started, a drive signal is sent to the inverter drive circuit 5 in accordance with the program in which the control means 6 is incorporated to drive the switching element 3 to oscillate the inverter circuit 4. Let it. At that time, the switching element 3 self-heats due to a loss at the time of conduction or a switching loss generated when switching from off to on and from on to off. In addition, the rated current consumption (about 12 A) of the rice cooker flows through the diode bridge 9 and self-heats with a loss corresponding to the product of the forward voltage and the rice cooker itself generates heat when cooking rice, causing the PTC thermistor 11 to generate heat. Raise the ambient temperature of the mounted printed wiring board. On the other hand, the PTC thermistor 11 itself also has a resistance value (about 40Ω at low temperature),
And the current supplied to the power supply circuit 7 via the second diodes 10a and 10b (current supplied from the power supply circuit to the control means 6 and the inverter drive circuit 5) to generate heat. When the rice cooker is used in a normal state, the temperature rise of the PTC thermistor 11 is designed to be about 70 ° C. to 80 ° C. Therefore, in this state, the resistance value of the PTC thermistor 11 remains at low temperature (40
Ω to 50Ω). The temperature rises of the switching element 3 and the diode bridge 9 are lower than the respective guaranteed temperatures (125 ° C. to 150 ° C. for semiconductor components).

On the other hand, when the temperature of the place where the rice cooker is placed is continuous continuous rice cooker or rice cooker is abnormally high, the ambient temperature of the printed wiring board rises more than usual, and the temperature of the switching element 3 and the diode bridge 9 becomes higher. May exceed the guaranteed temperature, in which case the parts exceeding the guaranteed temperature will be destroyed. Therefore, the components mounted on the printed wiring board do not exceed the guaranteed temperature,
The characteristics of the PTC thermistor 11 are selected so that the resistance value rapidly increases at a temperature higher than about (° C. to 80 ° C.) (about 100 ° C. in FIG. 2).

When the temperature of the PTC thermistor 11 is going to exceed 100 ° C. due to the above-mentioned abnormality,
As the resistance value increases, the first and second
The current supplied to the power supply circuit 7 via the diodes 10a and 10b is limited, and the power supply circuit 7 cannot output a normal voltage. A low voltage detection circuit 18 detects a drop in DC voltage and generates a zero volt pulse generation circuit 17.
To the control means 6 is interrupted. When the pulse signal from the zero volt pulse generation circuit 17 is interrupted while the DC voltage is supplied from the power supply circuit 7, the control means 6 abnormally increases the temperature near the printed wiring board on which the components are mounted. And the fan motor drive circuit 1
3 to output a drive signal to operate the fan motor 12.

As described above, the fan motor 12 does not operate in the normal state, and the rice cooker repeats the continuous rice cooking, or the temperature of the place where the rice cooker is placed becomes abnormally high, or the printed circuit board is overheated. If the temperature rises above normal, the fan motor 12 operates before the components mounted on the printed wiring board exceed the guaranteed temperature and cools the components, causing the temperature to rise further and destroying the components. In addition to the above, noise during rotation of the fan motor in a normal use state can be eliminated.

Embodiment 8 Next, an embodiment of the sixth means for solving the problem of the present invention will be described with reference to FIG. In FIG. 1, the difference from the first problem solving means is that the PTC thermistor 11 is installed near the switching element 3 and the switching element 3
To quickly detect temperature rises.

In the thus constructed IH rice cooker, when rice cooking is started, a drive signal is sent to the inverter drive circuit 5 according to the program in which the control means 6 is incorporated, and the switching element 3 is driven to oscillate the inverter circuit 4. Let it. At that time, the switching element 3 self-heats due to a loss at the time of conduction or a switching loss generated when switching from off to on and from on to off. In addition, the rated current consumption (about 12 A) of the rice cooker flows through the diode bridge 9 and self-heats with a loss corresponding to the product of the forward voltage and the rice cooker itself generates heat when cooking rice, causing the PTC thermistor 11 to generate heat. Raise the ambient temperature of the mounted printed wiring board. On the other hand, the PTC thermistor 11 itself also has a resistance value (about 40Ω at low temperature),
And the current supplied to the power supply circuit 7 via the second diodes 10a and 10b (current supplied from the power supply circuit to the control means 6 and the inverter drive circuit 5) to generate heat. When the rice cooker is used in a normal state, the temperature rise of the PTC thermistor 11 is designed to be about 70 ° C. to 80 ° C. Therefore, in this state, the resistance value of the PTC thermistor 11 remains at low temperature (40
Ω to 50Ω). The temperature rises of the switching element 3 and the diode bridge 9 are lower than the respective guaranteed temperatures (125 ° C. to 150 ° C. for semiconductor components).

On the other hand, when the temperature of a place where a rice cooker is placed is continuous continuous rice cooker or a rice cooker is abnormally high, the ambient temperature of the printed wiring board rises more than usual, and the temperature of the switching element 3 and the diode bridge 9 increases. May exceed the guaranteed temperature, in which case the parts exceeding the guaranteed temperature will be destroyed.

Further, since the inverter circuit 4 is optimally coupled to the pot 1 incorporated when assembling the main body of the IH rice cooker, the inverter circuit 4 is adjusted so as to oscillate and output accurate power consumption. Although the temperature rise does not exceed the guaranteed temperature in normal use, if the user mistakenly puts another pot (for example, an aluminum pot) and starts cooking rice, only the self-loss of the switching element 3 is lower than usual. When the temperature exceeds the guaranteed temperature, the switching element 3 is broken.

Therefore, in the components mounted on the printed wiring board, particularly, the switching element 3 does not exceed the guaranteed temperature, and the resistance value rapidly increases at a temperature higher than usual (about 70 ° C. to 80 ° C.). PTC thermistor 11
(About 100 ° C. in FIG. 2).

When the temperature of the PTC thermistor 11 is going to exceed 100 ° C. due to the above-mentioned abnormality,
As the resistance value increases, the first and second
The current supplied to the power supply circuit 7 via the diodes 10a and 10b is limited, the power supply circuit 7 cannot output a normal voltage, and the control means 6 and the inverter drive circuit 5 do not operate. Therefore, switching element 3 stops switching and stops oscillation of inverter circuit 4.

As described above, when continuous rice is cooked repeatedly, when the temperature of the place where the rice cooker is placed becomes abnormally high, or when rice is cooked with the wrong pot inserted, In particular, the resistance of the PTC thermistor 11 increases before the switching element 3 exceeds the guaranteed temperature, and the operation of the inverter circuit 4 stops before the switching element 3 exceeds the guaranteed temperature. Never do.

[0070]

As described above, the present invention provides an inverter circuit.
While the circuit is oscillating, various heat-generating components such as switching elements
Cooling means to prevent destruction by heat even under difficult conditions
Printed wiring with cooling and inverter components
Since the PTC thermistor detects the ambient temperature of the plate,
An abnormality has occurred in the cooling means and the parts cannot be cooled sufficiently.
AC electric resistance value of the PTC thermistor increases before the parts are also mounted on the printed wiring board by exceeds the guarantee temperature
The control unit will stop the power supply from the source to the power supply circuit
No drive signal can be supplied to the drive circuit because it will not operate
As a result , the operation of the inverter circuit stops, so that the temperature does not rise any more and the components are not destroyed.

Further, since the PTC thermistor detects the ambient temperature of the printed wiring board on which the inverter components are mounted, the temperature of the place where the rice cooker is placed may be abnormal when the rice cooker repeats the continuous rice cooker. Even if the temperature rises or the temperature on the printed wiring board rises higher than normal, the resistance of the PTC thermistor increases before the components mounted on the printed wiring board exceed the guaranteed temperature, and the voltage of the power supply circuit decreases. Is detected by the low voltage detection circuit, and a detection signal is output to the control means. As a result, the control means controls the zero volt pulse generation circuit.
The combination of the detection signal and the detection signal of the low voltage detection circuit outputs a stop signal to the inverter drive circuit and a signal for displaying an abnormality of the rice cooker on the display means, so that the operation of the inverter circuit is stopped. It is possible to inform the user of the abnormality of the rice cooker without the temperature being raised any more and the parts being destroyed.

Further, since the PTC thermistor detects the ambient temperature of the printed wiring board on which the inverter component is mounted, the temperature of the place where the rice cooker is placed may be abnormal when the rice cooker repeats the continuous rice cooker. Even if the temperature rises or the temperature on the printed wiring board rises higher than normal, the resistance of the PTC thermistor increases before the components mounted on the printed wiring board exceed the guaranteed temperature, and the voltage of the power supply circuit decreases. Is detected by the low voltage detection circuit, and the pulse signal supplied from the zero volt pulse generation circuit to the control means is cut off. As a result, the control means outputs a stop signal to the inverter drive circuit and a signal for displaying an abnormality of the rice cooker on the display means, so that the operation of the inverter circuit stops and the temperature rises further, and the parts are destroyed. And the user can be notified of the abnormality of the rice cooker.

Further, since the PTC thermistor detects the ambient temperature of the printed wiring board on which the inverter components are mounted, the temperature of the place where the rice cooker is placed may be abnormal when the rice cooker repeats continuous rice cookers. Even if the temperature rises or the temperature on the printed wiring board rises higher than normal, the resistance of the PTC thermistor increases before the components mounted on the printed wiring board exceed the guaranteed temperature, and the voltage of the power supply circuit decreases. Is detected by the low voltage detection circuit, and a detection signal is output to the control means. As a result, the control means displays the abnormality of the rice cooker on the display means.
Outputs a drive signal to output vital fan motor driving circuit a signal to be displayed, since operating the fan motor, it is possible to part to prevent temperature rise by cooling the component is prevented from destroying, rice to the user Can alert you of any abnormalities in the vessel . Further, since the rotation of the fan motor is stopped in the normal use state, noise and unnecessary power consumption due to the rotation can be eliminated.

Further, since the PTC thermistor detects the ambient temperature of the printed wiring board on which the inverter parts are mounted, the temperature of the place where the rice cooker is placed may be abnormal when the rice cooker repeats the continuous rice cooker. Even if the temperature rises or the temperature on the printed wiring board rises higher than normal, the resistance of the PTC thermistor increases before the components mounted on the printed wiring board exceed the guaranteed temperature, and the voltage of the power supply circuit decreases. Is detected by the low voltage detection circuit, and the pulse signal supplied from the zero volt pulse generation circuit to the control means is cut off. Thereby, the control means outputs a signal indicating the abnormality of the rice cooker to the display means.
And outputs a drive signal to the fan motor drive circuit to operate the fan motor, so it is possible to cool the parts without stopping the oscillation of the inverter circuit, prevent the temperature from rising, and prevent the parts from being destroyed. Yes , the user has a different rice cooker
Ru can inform the ordinary. Further, since the rotation of the fan motor is stopped in the normal use state, noise and unnecessary power consumption due to the rotation can be eliminated.

Further, since the temperature near the switching element is detected by the PTC thermistor, the temperature of the place where the rice cooker is placed may become abnormally high or erroneous when continuous rice is repeatedly cooked. When cooked rice in a pot, PTC is required before the switching element exceeds the guaranteed temperature, especially for the components mounted on the printed wiring board.
Since the resistance value of the thermistor increases and the control means and the inverter drive circuit do not operate and the operation of the inverter circuit stops, the temperature does not rise further and the parts are not destroyed.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram of a PTC thermistor of the IH rice cooker.

FIG. 3 is a circuit diagram of an IH rice cooker showing a second embodiment of the present invention.

FIG. 4 is a circuit diagram of an IH rice cooker showing a third embodiment of the present invention.

FIG. 5 is a circuit diagram of an IH rice cooker showing a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram of an IH rice cooker showing a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram of an IH rice cooker showing a sixth embodiment of the present invention.

FIG. 8 is a circuit diagram of an IH rice cooker showing a seventh embodiment of the present invention.

FIG. 9 is a circuit diagram of an IH rice cooker showing a conventional example.

FIG. 10 is a circuit diagram of an IH rice cooker showing another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pot 2 Heating coil 3 Switching element 4 Inverter circuit 5 Inverter drive circuit 6 Control means 7 Power supply circuit 8 AC power supply 11 PTC thermistor 12 Fan motor 13 Fan motor drive circuit 17 Zero volt pulse generation circuit 18 Low voltage detection circuit 19 Display means

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Showa 57-63512 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) A47J 27/00 103 A47J 27/00 109 H05B 3/00 330

Claims (6)

(57) [Claims] 1. An inner pot for accommodating rice or the like, a heating coil for heating the inner pot, an inverter circuit for supplying a high-frequency current to the heating coil, a switching element for switching the inverter circuit, and a switching element for , A control unit for controlling the drive circuit to perform rice cooking control, a power supply circuit for supplying a DC voltage to at least the control unit, and an AC for supplying power to at least the inverter circuit and the power supply circuit. Power supply and PT whose resistance value increases rapidly when the temperature of the element rises above a certain level
Heating components such as C thermistor elements and switching elements
Cooling means for cooling, and cooling means for driving the cooling means
A driving circuit , wherein the PTC thermistor element
C power supply and the power supply circuit, wherein the cooling means
An IH rice cooker configured to stop supplying power from the AC power supply to the power supply circuit when the ambient temperature of the PTC thermistor element becomes high outside the normal cooling range . 2. An inner pot containing rice and the like, and the inner pot is heated.
Heating coil and supplying high frequency current to the heating coil
Inverter circuit and switch this inverter circuit
Switching element to be switched and this switching element
A driving circuit for driving, and rice cooking control by controlling the driving circuit
And a DC power supply to at least the control means.
A power supply circuit for supplying voltage to the inverter circuit;
An AC power supply for supplying power to the circuit and the power supply circuit;
PT whose resistance increases rapidly when the temperature rises above a certain level
Display means for displaying an abnormal state of a heating element such as a C thermistor element and a switching element; a zero volt pulse generating circuit for generating a pulse near zero volt of an AC power supply; and detecting a drop in the voltage of the power supply circuit. A low voltage detection circuit, wherein the PTC thermistor element includes the AC power source and the PTC thermistor element.
The PTC thermistor element is connected between the power supply circuits.
When the ambient temperature becomes high, the AC power
Power supply to the control circuit, and the control means displays the abnormal condition on the display means according to a combination of the detection signal of the zero volt pulse generation circuit and the detection signal of the low voltage detection circuit, and controls the drive circuit. IH configured to stop the switching of the switching element via
rice cooker. 3. The IH rice cooker according to claim 2, wherein the generation of the detection signal of the zero volt pulse generation circuit is stopped according to the output of the low voltage detection circuit. 4. Heating parts such as switching elements are cooled.
And cooling means that the cooling means driving times for driving the cooling unit
And a control means for displaying an abnormal state on the display means in accordance with a combination of the detection signal of the zero volt pulse generation circuit and the detection signal of the low voltage detection circuit, and via a cooling means drive circuit. The IH rice cooker according to claim 2 , wherein the IH rice cooker is configured to drive the cooling means. 5. The IH rice cooker according to claim 4 , wherein the generation of the detection signal of the zero volt pulse generation circuit is stopped according to the output of the low voltage detection circuit. 6. The PTC thermistor element, the IH rice cooker according to any one of claims 1 to 5 disposed substantially in the vicinity of the switching element.