JP2003109739A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve usability and reliability through an appropriate power control such as raising the control speed. SOLUTION: With the induction heating cooker provided with a power level setting means 12 allowing a user to set power level suitable for his cooking, and a driving signal generating means 13 generating and outputting driving signals of a switching element 6 based on power control volume corresponding to the power level set by the power level setting means 12, a loading state detecting means 11 is fitted having areas divided in a plural number, which outputs area-correspondent values correspondent to output signals of an input current detecting means 8 and a resonance voltage detecting means 9. The driving signal generating means 13 controls input power by changing rate of increase and decrease of power control volume in correspondence with the area-correspondent values outputted from the loading state detecting means 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control method for an induction heating cooker.

[0002]

2. Description of the Related Art Conventional induction heating cookers do not produce an open flame,
It is recognized as a heat source to replace a gas table on a table because it can control the temperature of the load and is highly safe. Further, as an electric cooker to be incorporated in a system kitchen or the like, conventionally, a heater such as a sheath heater, a plate heater, or a halogen heater is used as a heat source, and one mouth is replaced with induction heating, or two or more heaters are induction-heated. It is being replaced with a cooker.

The induction heating cooker controls the input of a key switch operated by the user, the notification output thereof, the operation output of the heating means, the sensor signal input for detecting the state, and the like, and heats the load. A control means for setting and controlling electric power is provided.

An example of such a conventional example will be described with reference to FIG. FIG. 6 is a circuit block diagram of a conventional example.

In the figure, 1 is an AC power source. Reference numeral 2 denotes a rectifier circuit, which is composed of a plurality of rectifiers, whose input is connected to an AC power source 1, which rectifies the power source 1 and converts it into a DC power source for output. An inverter 3 is composed of a resonance capacitor 4, a heating coil 5, a switching element 6 and the like. The input is connected to the output of the rectifier circuit 2 and the switching element 6 is driven to convert the DC power supply into a high frequency current. And heats a load (not shown) arranged in the vicinity.

The resonance capacitor 4 and the heating coil 5 are connected in parallel, one end of this connection point is connected to the high-voltage side terminal (+ terminal in the figure) of the rectifier circuit 2, and the other end is the switching element 6
Connected to one end of. The other end of the switching element 6 is connected to the low voltage side terminal (− terminal in the figure) of the rectifier circuit 2.

Reference numeral 7 denotes an input voltage detecting means, which is connected between the input terminals of the rectifying circuit 2 and has a rectifying circuit 2, that is, an inverter 3.
The input voltage of is detected. Reference numeral 8 denotes an input current detecting means, which has an input current sensor 8a arranged to detect a current flowing between the power supply 1 and the rectifier circuit 2 and detects an input current of the inverter 3.

Reference numeral 9 is a resonance voltage detecting means for detecting the voltage at the connection point between the heating coil 5 and the switching element 6, that is, the resonance voltage applied to the switching element 6. Reference numeral 10 denotes an input power detecting means, which detects and calculates the input power from the output signals of the input voltage detecting means 7 and the input current detecting means 8 and outputs it. Reference numeral 12 is a power level setting means, in which the user sets a power level suitable for cooking and outputs the signal.

Reference numeral 13 is a drive signal generating means, which generates and outputs a drive signal for the switching element 6 based on the power control amount corresponding to the power level set by the power level setting means 12 to control the input power. In generating the drive signal, the drive signal generation means 13 controls the input power by increasing or decreasing the power control amount by a constant amount.

By the way, in the inverter 3, the resonance voltage applied to the switching element 6 and the energy for heating a load (not shown), that is, the input power, are basically the same with the power control amount as described below. I have a relationship.

The resonance voltage V has a linear function relationship with the power control amount W, and this relationship is expressed by the following equation. The V∝W input power Win has the following relationship with the capacitance C of the resonance capacitor 4 and the resonance voltage V. Win∝1 / 2 · C · V ^{2 From the} above two relational expressions, the input power Win is the power control amount W.
On the other hand, it is derived that there is a quadratic function relation as in the following equation. FIG. 5 is a schematic diagram of Win∝W ^{2 and} above, and is a characteristic diagram of the input power Win and the resonance voltage V with respect to the power control amount W in the inverter.

The horizontal axis of FIG. 5 is the power control amount W, one of the vertical axes is the resonance voltage V, and one is the input power Win.

In the figure, the resonance voltage V is shown by a broken line, and the input power Win is shown by a solid line. In addition, regarding each of the three lines, A is a ferrous magnetic load, B is a stainless magnetic load, and C is an improper load such as aluminum.

In the case of the iron-based magnetic material load of A, the input power Win changes abruptly in the region where the high resonance voltage V is applied, so that it is difficult to control it with constant power.

In the case of the stainless steel magnetic load of B, there is a portion where the resonance voltage V becomes high even if the input power Win is low, and even in such a low power region, the allowable value of the switching element 6 etc. may be exceeded. .

In the case of an improper load of C, a high resonance voltage V is applied even though the input power Win is low, and the allowable value of the switching element 6 or the like may be exceeded. Can not.

Based on the characteristics of the inverter 3 described above, the control method will be described next.

Since the detection processing of the input current, the input voltage and the resonance voltage V is performed by the analog-digital converter, the averaging processing for eliminating the influence of noise is required, and the predetermined values are determined until these detection values are determined. It takes time. Therefore, the power control amount W, which is the basis of the drive signal output of the drive signal generation means 13 for controlling the input power Win, is changed by a constant increase / decrease amount ΔW at every predetermined time, and the average of analog-digital conversion is obtained. The control is performed without being affected by the processing time.

This pattern will be described with reference to FIG. Figure 7
FIG. 6 is a diagram showing a power control method of an example of a conventional example.

In the figure, one of the vertical axes is the input power Win.
Is indicated by a solid line, and the other one is indicated by a broken line of the power control amount W,
The horizontal axis represents time.

The portion indicated by the period of time t1 shows the period from when the power level is set to level 1 by the power level setting means 12 and when the input power Win reaches level 1 after the heating starts. When heating is started, the drive signal generation means 13 generates and outputs a drive signal based on the low power control amount W, and the input power Win becomes a value corresponding to this.

Thereafter, the drive signal generating means 13 increases the power control amount W by a constant increase / decrease amount ΔW at predetermined time intervals and outputs a drive signal based on this. This pattern is shown by a stepped broken line in the period of time t1. Eventually, the input power Win rises corresponding to the output of the drive signal generation means 13 and reaches level 1. This pattern is shown by a solid curve in the period of time t1.

In the part indicated by the period of time t2, the power level setting means 12 changes the power level from level 1 to low level 2.
Shows the case of changing to. When the power level is changed, the drive signal generation means 13 reduces a constant increase / decrease amount ΔW from the control power amount W corresponding to level 1 in a predetermined time cycle, and outputs a drive signal based on this.

The drive signal generating means 13 continues to decrease the power control amount W by a constant increase / decrease amount ΔW every predetermined time until the input power Win reaches the level 2, and then outputs the drive signal based on this. This pattern is shown by a stepped broken line in the period of time t2. Eventually, the input power Wi
n rises corresponding to the output of the drive signal generating means 13 and reaches level 2. This pattern is shown by a solid curve in the period of time t2.

As described above, this control method is a relatively simple method because it only increases / decreases the power control amount W by a constant increase / decrease amount ΔW at predetermined time intervals, but has the following drawbacks. is there.

Since the rising time of the input power Win is slow in the low power region, it is inconvenient for the user that it takes time to reach the power level set at the stage when heating is started.

Further, in the high power region, since the input power Win increases greatly, the set power level is set to the maximum level,
The load may cause the voltage applied to the switching element 6 or the like to exceed an allowable value.

Further, since the dropping rate of the input power Win is insufficient in the high power region, the switching element 6 and the like stay in the vicinity of the overload region for a long time, which may cause a problem in reliability.

As another conventional example, Japanese Patent Laid-Open No. 2000-
There is 156281 publication. In this example, power detection means for detecting the power supplied to the inverter circuit, control means for outputting the conduction time of the switching element to control the power in a plurality of steps, and power for detecting the amount of power change per step A change amount detection means is provided, and the output of the control means adjusts the power by varying the conduction time of the switching element according to the power change amount per step. Since it is necessary to grasp the change in the power consumption, there is a drawback that the power cannot be controlled appropriately immediately.

Therefore, there are problems that the allowable value of the switching element or the like is exceeded at the time of the second output, and that appropriate power control cannot be performed for an unknown load.

[0031]

As described above, the conventional induction heating cooker is a control method in which the electric power control amount W is increased / decreased by a constant increase / decrease amount ΔW every predetermined time. There was a problem.

Since the rising time of the input power Win is slow in the low power region, it takes time for the user to reach the power level set at the stage when heating is started, which is inconvenient.

In the high power region, the input power Win rises greatly, so the set power level is set to the maximum level.
The load may cause the voltage applied to the switching element 6 or the like to exceed an allowable value.

Further, since the dropping rate of the input power Win is insufficient in the high power region, the switching element 6 and the like stay in the vicinity of the overload region for a long time, which may cause a problem in reliability.

Further, as in the example of Japanese Patent Application Laid-Open No. 2000-156281, the method of controlling the electric power by changing the increase / decrease amount of the electric power control amount according to the electric power change amount per step immediately controls the appropriate electric power. There is a problem that the control cannot be performed, the allowable value of the switching element or the like is exceeded at the time of the second output, and appropriate power control cannot be performed for an unknown load.

The present invention is intended to solve the above problems, and an object of the present invention is to perform appropriate power control such as increasing the control speed, to improve usability and reliability.

Further, the control speed is increased in the low power region, and the possibility that the voltage applied to the switching element or the like exceeds the allowable value is greatly reduced.

Furthermore, the switching element or the like is quickly moved from the state close to the overload region to the safe operation region to improve the reliability.

[0039]

In order to solve the above-mentioned problems, the present invention comprises a rectifying circuit for rectifying an AC power source, converting it to a DC power source, and outputting it, a resonance capacitor, a heating coil, a switching element and the like. And an inverter for converting the DC power supply into a high frequency current to heat a load arranged in the vicinity, an input voltage detecting means for detecting an input voltage of the inverter, and an input current detecting means for detecting an input current of the inverter. A resonance voltage detecting means for detecting a resonance voltage applied to the switching element 6, an input power detecting means for detecting and calculating input power from output signals of the input voltage detecting means and the input current detecting means, and outputting the input power. Based on the power level setting means for setting the power level suitable for cooking and the power control amount corresponding to the power level set by the power level setting means. In an induction heating cooker provided with a drive signal generating means for generating and outputting a drive signal for a switching element and controlling input power, a load state detecting means having a plurality of divided regions is provided, and the load state detecting means is an input. An area equivalent value corresponding to the output signals of the current detection means and the resonance voltage detection means is output, and the drive signal generation means corresponds to the area equivalent value output from the load state detection means, and the amount of increase or decrease of the power control amount To control the input power.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention, as described above, rectifies an AC power source, converts it to a DC power source, and outputs the rectified circuit.
An inverter configured by a resonance capacitor, a heating coil, a switching element, etc., for converting the DC power supply into a high frequency current to heat a load arranged in the vicinity, an input voltage detection means for detecting an input voltage of the inverter, and an inverter. Input current detecting means for detecting the input current of the switching element 6, a resonance voltage detecting means for detecting the resonance voltage applied to the switching element 6, and an input power is detected and calculated from the output signals of the input voltage detecting means and the input current detecting means. Input power detection means for outputting, power level setting means for the user to set a power level suitable for cooking, and drive signal for the switching element based on the power control amount corresponding to the power level set by the power level setting means. In an induction heating cooker having a drive signal generating means for generating and outputting and controlling input power. Provided the load state detection means having a frequency, the load state detection means outputs the region corresponding value corresponding to the output signal of the resonance voltage detector and the input current detection means,
The drive signal generating means controls the input power by changing the increase / decrease amount of the power control amount corresponding to the area equivalent value output from the load state detecting means.

As a result, it is possible to perform appropriate power control, improve usability, and improve reliability.

Further, when the drive signal generating means raises the input power, the input current detected by the input current detection means becomes a large value or the resonance voltage detected by the resonance voltage detection means becomes a high value, and this value is set to this value. Correspondingly, the input power is controlled by setting a small increase / decrease amount of the power control amount corresponding to the area equivalent value output by the load state detecting means.

As a result, the control speed is increased in the low power region, and the possibility that the voltage applied to the switching element or the like exceeds the allowable value can be greatly reduced.

Further, when the drive signal generating means decreases the input power, as the input current detected by the input current detecting means becomes smaller or the resonance voltage detected by the resonance voltage detecting means becomes lower, this value becomes Correspondingly, the amount of increase / decrease in the power control amount corresponding to the area equivalent value output by the load state detecting means is set to a large amount to control the input power.

As a result, the switching element or the like can be quickly moved from the state close to the overload region to the safe operation region and the reliability can be improved.

[0046]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing area division of a load state in the embodiment of the present invention, and FIG. 3 is a load state area in the embodiment of the present invention. It is the figure which showed division with a digital value.

The overall construction of an embodiment of the present invention will be described with reference to FIG.

In the figure, 1 is an AC power source. Reference numeral 2 denotes a rectifier circuit, which is composed of a plurality of rectifiers, whose input is connected to an AC power source 1, which rectifies the power source 1 and converts it into a DC power source for output. An inverter 3 is composed of a resonance capacitor 4, a heating coil 5, a switching element 6 and the like. The input is connected to the output of the rectifier circuit 2 and the switching element 6 is driven to convert the DC power supply into a high frequency current. And heats a load (not shown) arranged in the vicinity.

The resonance capacitor 4 and the heating coil 5 are connected in parallel, one end of this connection point is connected to the high voltage side terminal (+ terminal in the figure) of the rectifier circuit 2, and the other end is the switching element 6.
Connected to one end of. The other end of the switching element 6 is connected to the low voltage side terminal (− terminal in the figure) of the rectifier circuit 2.

Reference numeral 7 denotes an input voltage detecting means, which is connected between the input terminals of the rectifying circuit 2 and has the rectifying circuit 2, that is, the inverter 3.
The input voltage of is detected. Reference numeral 8 denotes an input current detecting means, which has an input current sensor 8a arranged to detect a current flowing between the power supply 1 and the rectifier circuit 2 and detects an input current of the inverter 3.

Reference numeral 9 is a resonance voltage detecting means for detecting the voltage at the connection point between the heating coil 5 and the switching element 6, that is, the resonance voltage applied to the switching element 6. Reference numeral 10 denotes an input power detecting means, which detects and calculates the input power from the output signals of the input voltage detecting means 7 and the input current detecting means 8 and outputs it.

Reference numeral 11 denotes a load state detecting means, which has a plurality of divided areas and outputs an area equivalent value corresponding to the output signals of the input current detecting means 8 and the resonance voltage detecting means 9. Reference numeral 12 is a power level setting means, in which the user sets a power level suitable for cooking and outputs the signal.

Reference numeral 13 is a drive signal generating means, which generates and outputs a drive signal for the switching element 6 based on the power control amount corresponding to the power level set by the power level setting means 12 to control the input power. When generating the drive signal, the drive signal generation unit 13 controls the input power by changing the increase / decrease amount of the power control amount in accordance with the area equivalent value output from the load state detection unit 11.

The overall operation of the above configuration will be described.

When the user operates the power level setting means 12 to set the power level and start heating, the rectifier circuit 2 rectifies the AC power supply 1 to convert it into a DC power supply and outputs it to the inverter 3. .

The drive signal generating means 13 generates and outputs a drive signal for the switching element 6 based on the power control amount corresponding to the set power level, and the switching element 6 is switched at a high frequency by this drive signal to generate the direct current. Converts the power supply into high frequency current. The high-frequency current flows through the resonance capacitor 4 and the heating coil 5, and the induction of the heating coil 5 starts heating a load (not shown) disposed in the vicinity.

The input power detecting means 10 has an output signal of the input voltage detecting means 7 for detecting the input voltage of the inverter 3, and
Input current detecting means 8 for detecting the input current of the inverter 3
Then, the input power is detected and calculated from the output signal of 1 and output to the drive signal generating means 13.

On the other hand, the load state detecting means 11 drives an area equivalent value corresponding to the output signal of the input current detecting means 8 and the output signal of the resonance voltage detecting means 9 for detecting the resonance voltage applied to the switching element 6. It outputs to the signal generation means 13.

The drive signal generation means 13 refers to the fed back output signal of the input power detection means 10 and controls the power corresponding to the area equivalent value output from the load state detection means 11 at predetermined time intervals. The amount of increase / decrease is changed, and based on this, a drive signal for the switching element 6 is output to control the input power, and heating is continued.

When the end of heating is instructed by a user's instruction or the like, the drive signal generating means 13 stops the signal output, and thereby the switching operation of the switching element 6 is stopped, and the heating operation is ended.

Next, the concept of area division of the load state in the load state detecting means 11 will be described with reference to FIG.
In the figure, the horizontal axis is the input current detected by the input current detection means 8 and the vertical axis is the resonance voltage detected by the resonance voltage detection means 9.

The region formed by the input current on the horizontal axis and the resonance voltage on the vertical axis is divided by the five lines described below. The line J is a boundary line that divides a load that can be heated and a load that cannot be heated into a lower part and an upper part. The line K is a boundary line indicating a limit due to the allowable voltage of the switching element 6 or the like. The line L is a boundary line indicating a limit due to the allowable current of the rectifier circuit 2 and the wiring due to the input current. A line D is a boundary line that divides a high resonance voltage region and a low resonance voltage region into upper and lower regions. A line E is a boundary line that divides a large input current region and a small input current region into upper and lower regions.

These five lines divide the entire area into the following seven areas. 1) Region A is a region where the input current is small and the resonance voltage is low. 2) Region B is a region where the input current is large and the resonance voltage is low. 3) Region C is a region where the input current is small and the resonance voltage is high. 4) Region D is a region where the input current is large and the resonance voltage is high. 5) Region E is the region where the resonance voltage exceeds the allowable value. 6) Area where the input current exceeds the allowable value. 7) Region is a region where the load cannot be heated.

The relationship between the load state and the area will be described more specifically. When the iron-based magnetic load is placed at the proper position, the area A or the area B is set. When the magnetic material of stainless steel is placed at the proper position, the area C or area D is set. When it is placed in a regular position with a load of aluminum or the like, it becomes a region E or a region G.

Further, when the iron-based magnetic load is placed at an abnormal position such as a distance from the heating coil 5, the area C or area G is set. When the power supply voltage suddenly rises due to an iron-based magnetic load, it may reach the region. If the user shakes during heating with a ferrous or stainless steel magnetic material load, it may become a region E. In this way, since the load exists in these seven areas regardless of the state, it is possible to perform appropriate power control even for an unknown load.

FIG. 3 shows the area division of the load state by digital values, and is an example of the area division adapted when the load state detecting means 11 and the like are constituted by a microcomputer.

In the figure, the horizontal axis represents the input current, and the vertical axis represents the resonance voltage, which are both divided into 16 levels of digital values.
The above area is divided into 7 areas as described above, and the areas a to g are replaced with area equivalent values of numerical values 1 to 7 so that the microcomputer can perform processing.

Then, the increase / decrease amount ΔW of the power control amount W, which is the basis of the drive signal generated and output by the drive signal generating means 13 at every predetermined time, is set to the following relation for each region.

When increasing the input power Win, [Region A> Region B or Region C> Region D] Set like.

That is, when the drive signal generating means 13 raises the input power Win, as the input current detected by the input current detecting means 8 becomes a large value or the resonance voltage detected by the resonance voltage detecting means 9 becomes a high value. The input power Win is controlled by setting the increase / decrease amount ΔW of the power control amount W corresponding to the area equivalent value output by the load state detecting means 11 to a small value in correspondence with this value. When lowering the input power Win, set [area d> area b or area c> area b].

That is, when the drive signal generating means 13 lowers the input power Win, the input current detected by the input current detecting means 8 becomes a small value or the resonance voltage V detected by the resonance voltage detecting means 9 becomes a low value. According to this value, the input power Win is controlled by setting the increase / decrease amount ΔW of the power control amount W corresponding to the area equivalent value output by the load state detecting means 11 to a large value.

In the following description, the increase / decrease amount ΔW of the power control amount W will be determined as follows. When the input power Win rises, the area B is “ΔWup (large)”, the area B or area C is “ΔWup (medium)”, and the area D is “ΔWu”.
p (small) ". When the input power Win is decreasing, it is “ΔWdw (large)” in the case of area D, “ΔWdw (medium)” in the case of area B or area C, and “ΔWdw in the case of area B”.
(Small) ".

The magnitudes of ΔWup (small) and ΔWdw (small) are substantially the same as the constant increase / decrease amount ΔW of the power control amount W of the conventional example.

Further, since the regions E and H have special load states, the heating is temporarily stopped, and if the same state continues, the heating is completely stopped.

A power control method of one embodiment of the present invention having the above configuration will be described with reference to FIG.

In the figure, one of the vertical axes is the input power Win.
Is indicated by a solid line, and the other one is indicated by a broken line of the power control amount W,
The horizontal axis represents time.

The part indicated by the period of time t1 shows the period from when the power level is set to level 1 by the power level setting means 12 and when the input power Win reaches the power level 1 from the start of heating. The drive signal generation means 13 outputs the drive signal based on the change amount ΔW of the power control amount W while changing the increase / decrease amount ΔW at predetermined time intervals. This pattern is shown by a stepped broken line in the period of time t1. Input power Win
Corresponding to the output of the drive signal generating means 13 rises to reach level 1. This pattern is shown by a solid curve in the period of time t1.

In the portion indicated by the period of time t2, the power level setting means 12 changes the power level from level 1 to low level 2.
Shows the case of changing to. The drive signal generation means 13 outputs the drive signal based on the change amount ΔW of the power control amount W changing at every predetermined time until the input power Win reaches the level 2. This pattern is shown by a stepped broken line in the period of time t2. The input power Win rises corresponding to the output of the drive signal generation means 13 and reaches level 2. This pattern is shown by a solid curve in the period of time t2.

When the power level is set to level 1 by the power level setting means 12 and the heating of the load is started, the drive signal generating means 13 first generates and outputs the drive signal based on the low power control amount W. The load state detecting means 11 discriminates the load state from the seven regions based on the output signals of the input current detecting means 8 and the resonance voltage detecting means 9 which have started to operate, selects one and outputs it.

Usually, since the electric power is low at the start of heating, the load state detecting means 11 discriminates and selects the load state as the area B. Therefore, after a predetermined time, the increase / decrease amount ΔW of the power control amount W which is the basis of the output signal of the drive signal generating means 13 is “ΔWup.
(Large) ”, and the input power Win is significantly higher than in the past. This operation is continued while the load state area selected and determined by the load state detecting means 11 continues in the same area.

When the input power Win continues to rise and the load state selected by the load state detecting means 11 is in the range b,
The increase / decrease amount ΔW of the power control amount W which is the basis of the output signal of the drive signal generation means 13 becomes “ΔWup (medium)”, and the increase width of the input power Win is slightly decreased.

Further, when the input power Win continues to increase and the load state determined by the load state detecting means 11 becomes the area D, the increase / decrease amount Δ of the power control amount W which is the basis of the output signal of the drive signal generating means 13 W becomes "△ Wup (small)",
The increase width of the input power Win is further reduced.

Then, the input power Win reaches the set power level 1 equivalent. The time t1 from the start of heating to reaching the power level 1 is shortened as compared with the conventional example shown in FIG. That is, the control speed becomes faster in the low power region.

Further, since the rising width of the input power Win is made small in the region where the input power Win is high, that is, the region where the input current is large or the region where the resonance voltage V is high, it is applied to the switching element 6, the heating coil 5, etc. It is possible to significantly reduce the possibility that the voltage exceeds the allowable value.

Next, the case where the set power is changed from level 1 to low level 2 will be described.

Input power Wi when the power level is changed
Since n is level 1, the load state detected by the load state detection unit 11 is in the area D, and the increase / decrease amount ΔW of the power control amount W which is the basis of the output signal of the drive signal generation unit 13 is “ΔW”.
dw (large) ”, the amount of decrease in power is large, and the input power Win rapidly decreases. This operation is continued during the same load condition region selected and determined by the load condition detecting means 11.

Further, when the input power Win decreases and the load state to be discriminated and selected by the load state detecting means 11 becomes the area B, the power control amount W which is the basis of the output signal of the drive signal generating means 13 The amount of increase / decrease ΔW becomes “ΔWdw (medium)”, the width of decrease is slightly smaller, and the input power Win decreases.

As an effect of this, since the falling width of the input power Win is made large in the region where the input power Win is high, that is, the region where the input current is large or the resonance voltage V is high, the switching element 6 and the like are close to the overload region. Reliability is improved by quickly shifting from the state to the safe operation area.

In the above embodiment, the area is divided into seven areas. However, by increasing the number of divisions, quick power control and switching element 6 can be applied to various loads.
It is possible to increase the protection level against the like and improve the reliability.

Further, the areas E and E shown in FIG. 2 are not set in the load state detecting means 11, and the outputs of the resonance voltage detecting means 9 and the input current detecting means 8 are compared with respective threshold values by a comparator. However, the increase / decrease amount ΔW of the power control amount W may be set from the result of the direct determination. With this configuration, the processing speed can be further improved.

[0092]

As described above, according to the induction heating cooker of the present invention, the drive signal of the switching element is generated and output based on the power control amount corresponding to the power level set by the power level setting means. In an induction heating cooker having a drive signal generating means for controlling electric power, a load state detecting means having a plurality of divided regions is provided, and the load state detecting means outputs the input current detecting means and the resonance voltage detecting means. A region equivalent value corresponding to a signal is output, and the drive signal generation unit controls the input power by changing the increase / decrease amount of the power control amount corresponding to the region equivalent value output from the load state detection unit. , The power is controlled properly, it is easy to use and the reliability can be improved.

When the drive signal generating means raises the input power, the input current detected by the input current detecting means has a large value or the resonance voltage detected by the resonance voltage detecting means has a high value. Correspondingly, the input power is controlled by setting a small increase / decrease amount of the power control amount corresponding to the area equivalent value output by the load state detecting means.

As a result, the control speed is increased in the low power region, and the possibility that the voltage applied to the switching element or the like exceeds the allowable value can be greatly reduced.

Further, when the drive signal generating means lowers the input power, as the input current detected by the input current detecting means becomes smaller or the resonance voltage detected by the resonance voltage detecting means becomes lower, this value is set to this value. Correspondingly, the amount of increase / decrease in the power control amount corresponding to the area equivalent value output by the load state detecting means is set to a large amount to control the input power.

As a result, the switching element and the like are swiftly moved from the state close to the overload region to the safe operation region, and the reliability is improved.

By further increasing the number of divisions of the area in the load state detecting means, it is possible to improve the reliability by swiftly controlling the electric power and increasing the protection level for the switching element and the like even for a wide variety of loads. .

Further, since the power control can be performed immediately, the power control can be appropriately performed even for an unknown load.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing area division in a load state according to an embodiment of the present invention.

FIG. 3 is a diagram showing, in digital values, area division in a load state according to an embodiment of the present invention.

FIG. 4 is a diagram showing a power control method according to an embodiment of the present invention.

FIG. 5 is a characteristic diagram of the input power Win and the resonance voltage V with respect to the power control amount W in the inverter.

FIG. 6 is a circuit block diagram of a conventional example.

FIG. 7 is a diagram showing a power control method of a conventional example.

[Explanation of symbols]

1 power supply 2 rectifier circuit 3 inverter 5 heating coils 6 switching elements 7 Input voltage detection means 8 Input current detection means 9 Resonance voltage detection means 10 Input power detection means 11 Load state detection means 12 Power level setting means 13 Drive signal generating means

Claims (3)

[Claims] 1. A rectifier circuit (2) for rectifying an AC power source (1) and converting it to a DC power source for output, a resonance capacitor (4), a heating coil (5), a switching element (6) and the like. An inverter (3) for converting the DC power supply into a high frequency current to heat a load arranged in the vicinity thereof, an input voltage detecting means (7) for detecting an input voltage of the inverter (3), and an inverter (3) Input current detecting means (8) for detecting the input current of the switching element, resonance voltage detecting means (9) for detecting the resonance voltage applied to the switching element (6), input voltage detecting means (7) and input current detecting means. Input power detection means (10) for detecting and calculating input power from the output signal of (8), and power level setting means (12) for setting a power level suitable for cooking by the user.
And a drive signal generating means (13) for generating and outputting a drive signal for the switching element (6) based on the power control amount corresponding to the power level set by the power level setting means (12) and controlling the input power. In an induction heating cooker including a load condition detecting means (11) having a plurality of divided regions, the load condition detecting means (11) is an input current detecting means (8) and a resonance voltage detecting means (9). Area corresponding value corresponding to the output signal of the control signal is output, and the drive signal generating means (13) changes the increase / decrease amount of the power control amount corresponding to the area equivalent value output from the load state detecting means (11). An induction heating cooker characterized in that the input power is controlled by controlling the induction heating cooker. 2. When the drive signal generating means (13) increases the input power, the input current detected by the input current detecting means (8) has a large value or the resonance voltage detected by the resonance voltage detecting means (9) is As the value becomes higher, the input power is controlled by setting the increase / decrease amount of the power control amount corresponding to the area equivalent value output by the load state detecting means (11) to be smaller corresponding to this value. Item 1. An induction heating cooker according to item 1. 3. When the drive signal generating means (13) lowers the input power, the input current detected by the input current detecting means (8) has a small value or the resonance voltage detected by the resonance voltage detecting means (9) is As the value becomes lower, the increase / decrease amount of the power control amount corresponding to the area equivalent value output by the load state detecting means (11) is set correspondingly to this value to control the input power. The induction heating cooker according to claim 1 or 2.