JP2864800B2 - 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 electromagnetic induction heating type rice cooker for induction heating a pot using a high-frequency magnetic field.

[0002]

2. Description of the Related Art An electromagnetic induction heating rice cooker supplies a high-frequency magnetic field generated at a frequency of about 20 KHz from an inverter circuit to a heating coil, thereby supplying a high-frequency magnetic field generated from the heating coil to a magnetic material pot such as iron. By doing so, the pot itself generates heat due to eddy current loss generated in the pot and cooks rice.

The circuit configuration of a conventional rice cooker of the electromagnetic induction heating type will be described below. FIG. 3 shows a circuit configuration diagram of a conventional electromagnetic induction heating type rice cooker. In FIG. 3, reference numeral 1 denotes an AC power supply to which a rectifier 2 is connected. An inverter circuit 3 is connected to the output side of the rectifier 2. The inverter circuit 3 includes a smoothing capacitor 31, a resonance capacitor 32 connected in parallel with the heating coil 4, and a switching element 33 and a diode 34 connected in anti-parallel. Above the heating coil 4, a cooking pot 5 is provided. Reference numeral 6 denotes a control circuit for controlling the operation of the inverter circuit 3, a peak voltage control circuit 61 for detecting the peak voltage of the switching element 33 and controlling it to be constant, and a peak voltage control for adjusting the peak voltage of the switching element 33. Means 61b, an input current control circuit 64 for receiving the output of the current transformer 7 for detecting the input current of the inverter circuit 3 and controlling the input current of the inverter circuit 3 to be constant, and adjusting the input current of the inverter circuit 3 Input current adjusting means 64a, a comparison circuit 66 which compares the output voltage of the peak voltage control circuit 61 with the output voltage of the input current control circuit 64, and outputs the output according to the higher output voltage. The ON time width setting circuit 65 receives the ON time of the switching element 33 and determines the ON time.

[0004] Regarding the rice cooker configured as described above,
The operation will be described below. First, the operation of the inverter circuit 3 is controlled by the peak voltage adjusting means 61b in the peak voltage control circuit 61 and the input current adjusting means 64a in the input current control circuit 64 when the AC power supply 1 is at the rated voltage, for example, at 100V. The peak voltage of the switching element 33 is adjusted to, for example, 700 V and the input current of the inverter circuit 3 is adjusted to, for example, 12 A so that the input power of the rice cooker becomes 1200 W. The peak voltage control circuit 61 outputs an output to the comparison circuit 66 so that the peak voltage of the switching element 33 is 700 V even when the AC power supply 1 fluctuates, for example, between 90 and 110 V. If the inverter circuit 3 is controlled only by the peak voltage control circuit 61, the peak voltage of the switching element 33 is always kept constant at 700 V by the peak voltage control circuit 61. Regardless of the operation, the input power of the rice cooker is almost 1200W.
Be kept constant.

[0005] The input current control circuit 64 controls the comparison circuit 6 so that the input current of the inverter circuit 3 is kept constant at 12 A even if the AC power supply 1 fluctuates, for example, between 90 and 110V.
6. Output to 6. If the inverter circuit 3 is controlled only by the input current control circuit 64, the input current of the inverter circuit 3 is always 12 A by the input current control circuit 64.
The inverter circuit 3 is operated at an almost constant input current in accordance with the fluctuation of the AC power supply 1, and the input current of the rice cooker is kept substantially constant at 12A, that is, the inverter circuit 3 is linearly operated in accordance with the fluctuation of the AC power supply 1. In general, the input power of the rice cooker changes. Therefore, when the AC power supply 1 is at 90 V, the input power of the rice cooker is 1
When the AC power supply 1 is 110 V, the input power of the rice cooker fluctuates to 1320 W. Actually, the peak voltage control circuit 61 and the input current control circuit 64 are configured so that the input power of the rice cooker is 1200 W when the AC power supply 1 is at 100 V by the peak voltage adjusting means 61 b and the input current adjusting means 64 a, respectively.
It is adjusted in advance so that That is, although not shown, the input power of the rice cooker linearly decreases with respect to the fluctuation of the AC power supply 1 when the AC power supply 1 has a rated voltage of 100 V or less, and substantially 1200 W when the AC power supply 1 has a rated voltage of 100 V or more. Has properties that are kept constant. Therefore,
In particular, the AC power supply 1 is set to 100 V
When the voltage falls below, the input current of the inverter circuit 3 decreases in proportion to the value of the AC power supply 1, so that the loss of the rectifier 2 and the switching element 33 can be suppressed from increasing, and a cooling heat sink, a cooling fan, etc. Cooling components and the rice cooker body can be downsized.

[0006]

However, in the conventional configuration described above, the cooling components such as the cooling heat sink and the cooling fan and the size and cost reduction of the rice cooker are reduced by controlling the input current by the current transformer 7 or the like. Circuit 64
Is indispensable, and there is a problem that the input current control method cannot be abolished by rationalization of circuit components and the like.

The present invention solves the above-mentioned conventional problems, and comprises an input current control circuit 64 and an input current adjusting means 64a.
Instead, a means for newly controlling and adjusting the ON time of the switching element 33 is provided, the current transformer 7 and the input current control circuit 64 are eliminated, and the object is to provide a rice cooker which can be reduced in size and cost.

[0008]

SUMMARY OF THE INVENTION In order to achieve this object, a rice cooker according to the present invention comprises a pot for placing an object to be heated, a heating coil for inductively heating the pot, and an inverter circuit for supplying high-frequency power to the heating coil. And a control circuit for controlling an inverter circuit, wherein the inverter circuit is connected in parallel with the heating coil, a switching element connected in series with the heating coil, and connected in anti-parallel with the switching element. A control circuit that controls the peak voltage of the switching element to be constant, an on-time control circuit that controls the on-time of the switching element to be constant, A peak voltage adjusting means for adjusting a peak voltage of the switching element; and an on-time of the switching element. And an on-time width setting circuit for setting an on-time width of the switching element in accordance with a higher output voltage of the peak voltage control circuit and the on-time control circuit, wherein the power supply voltage is rated. The output voltage of the peak voltage control circuit is equal to the output voltage of the on-time control circuit when the voltage is equal to or lower than the voltage, and the peak voltage adjustment means and the on-time adjustment means are adjusted.

[0009]

With this configuration, the AC power supply can be operated at a rated voltage of 10%.
Even if the voltage drops to 0 V or less, the input of the inverter circuit is reduced according to the value of the AC power supply by the on-time control circuit, so that it is possible to suppress an increase in loss of the rectifier and the switching element. Cooling components such as a fan and the rice cooker body can be miniaturized.

[0010]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an AC power supply to which a rectifier 2 is connected. An inverter circuit 3 is connected to the output side of the rectifier 2. The inverter circuit 3 includes a smoothing capacitor 31, a resonance capacitor 32 connected in parallel with the heating coil 4, and a switching element 3 connected in anti-parallel.
3 and a diode 34. Heating coil 4
Above is provided a cooking pot 5. 6, a control circuit for controlling the operation of the inverter circuit 3; a peak voltage control circuit 61 for detecting the peak voltage of the switching element 33 and controlling it to be constant;
A peak voltage adjusting means 61b for adjusting the peak voltage of
An on-time control circuit 62 for controlling the on-time of the switching element 33 to be constant;
ON time adjusting means 62a for adjusting the ON time of the output voltage of the peak voltage control circuit 61 and the ON time control circuit 62
And an on-time width setting circuit 65 that receives the output signal of the comparing circuit 66 and determines the on-time width of the switching element 33. Make up.

In FIG. 2, the AC power supply 1 is controlled when the peak voltage control circuit 61 controls the peak voltage of the switching element 33 to be constant, and when the ON time control circuit 62 controls the ON time of the switching element 33 to be constant. It is a characteristic view which shows the input electric power characteristic of the rice cooker with respect to a voltage.

In the above configuration, when the AC power supply 1 has a rated voltage of 100 V or less, for example, 95 V, the output voltage of the peak voltage control circuit 61 and the output voltage of the on-time control circuit 62 are the same, that is, rice cooking. The peak voltage adjusting means 61a and the on-time adjusting means 62a are adjusted so that the input power of the heater becomes the same. The actual adjustment is performed when the AC power supply 1 is at 100 V by the peak voltage adjusting means 61a.
200 W, the AC power supply 1 is
It is adjusted to be 1320 W at 00 V. The peak voltage control circuit 61 and the on-time control circuit 62 thus adjusted have input power characteristics with respect to the voltage of the AC power supply 1 as shown in FIG. That is, about 95V
In the vicinity, the output voltage of the peak voltage control circuit 61 and the output voltage of the on-time control circuit 62 become the same. If the output voltage is 95 V or more, the input power of the rice cooker is controlled to be approximately 1200 W constant by the peak voltage control circuit 61, In the following, the input power of the rice cooker is controlled by the
Decreases linearly in proportion to the voltage value of
It decreases to about 80W. Almost AC power supply 1 as shown in FIG.
Is 95V, so that the power characteristic straight line of the peak voltage control circuit 61 and the power characteristic straight line of the on-time control circuit 62 intersect with each other.
Is adjusted because the slope of the power characteristic line where the on time of the switching element 33 is kept constant by the on time control circuit 62 is changed to the slope of the power characteristic line where the input current is kept constant by the conventional input current control circuit. Since the input power of the rice cooker is large when the ON time of the switching element 33 is constant, the AC power supply 1 is 100 V and the power characteristic line of the peak voltage control circuit 61 is the same as in the conventional example. Voltage adjusting means 61b and on-time adjusting means 6 so that the power characteristic line of
By adjusting 2a, the input power of the rice cooker at 90V becomes 10
This is because it becomes less than 00W and the rice cooking performance is hindered.

As described above, the peak voltage control circuit 6
1 and the on-time control circuit 62 control the operation of the inverter circuit 3, and the peak voltage adjusting means 61b and the on-time control circuit 62a determine the output of the peak voltage control circuit 61 when the AC power supply 1 is at or below the rated voltage of 100V. Since the voltage and the output voltage of the on-time control circuit 62 are adjusted to be constant, it is possible to obtain an input power characteristic with respect to the voltage of the AC power supply 1 substantially equal to that of the rice cooker having the conventional input current control circuit. Thus, the current transformer can be abolished, the circuit and the circuit board can be reduced in size and rationalized, the cost can be reduced, and the size of the rice cooker can be reduced.

[0015]

As described above, according to the present invention, the peak voltage adjusting means and the on-time control means make the AC power supply equal to the rated voltage of one.
Since the output voltage of the peak voltage control circuit and the output voltage of the on-time control circuit are adjusted to be constant at or below 00 V, rice cooking performance can be ensured, circuit components can be downsized, the cooling configuration can be simplified, An excellent rice cooker that can reduce costs and improve reliability can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a rice cooker according to one embodiment of the present invention.

FIG. 2 is a graph showing input power characteristics of a peak voltage control circuit and an on-time control circuit with respect to a voltage of an AC power supply.

FIG. 3 is a circuit diagram of a conventional rice cooker.

[Description of Signs] 3 Inverter circuit 4 Heating coil 5 Pot 6 Control circuit 32 Resonant capacitor 33 Switching element 34 Diode 61 Peak voltage control circuit 62 ON time control circuit 65 ON time width setting circuit 61b Peak voltage adjusting means 62a ON time adjustment means

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) A47J 27/00 103 G05D 23/19

Claims (1)

(57) [Claims] 1. A pan for placing an object to be heated, a heating coil for induction heating the pan, an inverter circuit for supplying high-frequency power to the heating coil, and a control circuit for controlling the inverter circuit, wherein the inverter circuit comprises: The heating capacitor includes a resonance capacitor connected in parallel with the heating coil, a switching element connected in series with the heating coil, and a diode connected in anti-parallel with the switching element, wherein the control circuit has a constant peak voltage of the switching element. A peak voltage control circuit that controls the switching element to have a constant on time; an on time control circuit that controls the switching element to have a constant on time; peak voltage adjusting means that adjusts the peak voltage of the switching element; On-time adjusting means for adjusting the on-time, the peak voltage control circuit, and the on-time system. An on-time width setting circuit for setting an on-time width of the switching element according to a higher output voltage of the circuit, wherein the output voltage of the peak voltage control circuit and the on-time when the power supply voltage is equal to or lower than the rated voltage. A rice cooker in which the peak voltage adjusting means and the on-time adjusting means are adjusted so that the output voltage of the time control circuit becomes the same.