JP2643430B2 - Induction heating cooker - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an induction heating cooker.

2. Description of the Related Art As shown in FIG. 4, a conventional induction heating cooker of this type comprises a frequency device 3 which converts a commercial power supply 1 into a high-frequency large current of about 20 KHz or more and supplies it to a heating coil 2; An input current detection circuit 4 for detecting an input current of the conversion device 3,
A maximum input current setting circuit 5, a collector voltage detecting circuit 6 of the switching transistor 305 of the frequency converter 3,
It consisted of a maximum collector voltage setting circuit 7. The frequency converter 3 includes a rectifier 301, a choke coil 302, a filter capacitor 303, a switching transistor 305, and a control circuit 306 for driving and controlling the switching transistor.
The heating coil 2 is connected in parallel with the resonance capacitor 304. The input detection circuit 4 includes a current transformer 401, a diode 402, and a smoothing capacitor 403, and outputs a detection voltage proportional to an input current. The output signal of the input detection circuit 4 is a variable signal of the maximum input current setting circuit 5. The reference voltage, which is input to the minus terminal of the comparator 504 via the resistor 501 and is determined by the division ratio of the resistor 502 and the resistor 503, is input to the plus input terminal of the comparator 504. The collector voltage detection circuit 6 includes a switching transistor 305
A detection voltage proportional to the voltage applied to the input current setting circuit 5 is output to a maximum collector voltage setting circuit 7 having the same circuit configuration as the input current setting circuit 5. Output signals to the maximum input current setting circuit 5 and the maximum collector current setting circuit 6 are input to an OR circuit 8 using diodes, and the lower output signal of the two setting circuits is input to a control circuit 306, and a switching transistor 305 was configured to control the conduction time. Variable resistor of the maximum input current setting circuit 5
Reference numeral 501 denotes a comparator 504 due to a variation in the output voltage of the input current detection circuit 4 due to a variation in the characteristics of components such as the current transformer 401, the diode 402, or the capacitor 403 or a variation in the resistances of the resistors 502 and 503 of the maximum input current setting circuit 5. Similarly, the resistor 701 is used to correct the switching due to the characteristic variation of the components of the collector current detection circuit 6 or the maximum collector voltage setting circuit 7 due to the variation of the set value of the maximum input current caused by the variation of the reference voltage. This is to correct the characteristic variation of the collector voltage applied to the transistor 305.

SUMMARY OF THE INVENTION In such a conventional configuration, after assembling the device, the adjuster measures the input current while adjusting the variable resistor 501 or the variable resistor 701.
Has to be set to a predetermined value, and it takes time and effort to perform the adjustment, and there is a problem that the variation of the adjustment value in mass production increases.

Therefore, an object of the present invention is to simplify the adjustment work required when setting the maximum input current or setting the maximum collector voltage, and to increase the setting accuracy at the time of adjustment.

Means for Solving the Problems In order to achieve the above object, the present invention provides a frequency converter, a first input current detector or a component applied voltage and a current detector of the frequency converter, Input current control means for controlling the input current by comparing the signal level detected by the input current detection means for input with the signal level stored in the set value storage means, or the component applied voltage;
A component application voltage for controlling the voltage or current applied to the components of the frequency conversion device by comparing the detection signal level of the current detection means with the signal level stored in the set value storage means, current control means, and an output correction start signal Input means, and when a predetermined signal is input from the output correction start signal input means, the input current control means sets a predetermined input current based on an output signal of a second input current detection circuit external to the device. Maximum input current correction means for storing the output signal level of the first input current detection means or the component applied voltage and the output signal level of the current detection means at this time in the set value storage means, or A maximum component applied voltage correction means is provided.

Function The induction heating cooker of the present invention has the above-described configuration, and uses a high-precision input current detection device calibrated using a predetermined heated pan as a load as a second input current detection unit outside the device. When a predetermined signal is input from the output correction start signal input means, the input current control means controls the frequency so that a predetermined maximum input current value can be obtained based on an accurate detection signal from the second input current detection means. Since the output of the converter is controlled, the accuracy of the set input current value is high. When a predetermined input current value is obtained, the input correction means then inputs the signal level detected by the first input current detection means inside the device, stores this value in the set value storage means, and outputs it again. Unless a correction start signal is input,
Since the maximum input current of the frequency conversion device is controlled based on the detection signal of the first input current detection means and the corrected maximum input current set value stored in the set value storage means,
The target maximum input current can be set accurately. That is, the setting error of the maximum input current value due to the detection variation due to the variation in the electrical characteristics of the components of the first input current detection means is extremely small. Is connected from the outside and an output correction start signal is input to the device, and the maximum input current can be set automatically, accurately and easily.

Similarly, the maximum component applied voltage correction means also places a predetermined heated pan, uses the calibrated accurate input current detection device as the second input current detection means outside the device, and starts output correction. When a predetermined signal is input from the signal input means, the input current control means accurately controls the input current value to a predetermined value based on the accurate detection signal from the second input current detection means. The maximum component applied voltage correction means inputs the component applied voltage at this time and the output signal level of the current detection means, and stores this value in the set value storage means,
Unless the output correction start signal is input again, the voltage and current applied to the components of the frequency conversion device are controlled based on these values thereafter. Thus, the maximum applied voltage and current value of the component can be set to predetermined values with high accuracy without receiving the same.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, the main circuit of the frequency converter 9 includes a rectifier 11 for rectifying a commercial power supply 10, a filter coil 12,
It comprises a filter capacitor 13, a resonance capacitor 14, a heating coil 15 connected in parallel to the capacitor, and a switching transistor 16. On the other hand, the control unit of the frequency converter 9 converts an output voltage of the first input current detection circuit 17 including a current transformer for detecting an input current into a digital signal, and inputs the digital signal to the microcomputer 19. 18, an A / D converter 21 for converting an output voltage of a collector voltage detection circuit 20 for detecting a collector voltage of the switching transistor 16 into a digital signal and inputting the digital signal to a microcomputer 19, and a set value storage including a nonvolatile digital storage element A circuit 22 and a correction start switch 23 are provided. Furthermore, an input terminal 26, which is installed outside the device and is input by a second input current detection circuit 24 which detects an input current and receives a digitized detection signal by an A / D converter 25, is provided in the control unit. Have been. The signal input from the input terminal 26 is input to the microcomputer 19. The output voltage of the second input current detection circuit 24 and
The output voltage of the A / D converter 25 is accurately calibrated so that a predetermined relationship between the input current and the output voltage can be accurately obtained. The microcomputer 19 is a one-chip microcomputer having a CUP, a ROM, a RAN, and an input / output, and as shown in FIG. 2, an input current control means 19a, a component applied voltage, a current control means 19b, and a maximum input current correction means 19c. And a maximum component applied voltage correction means 19d, after power-on, first, after turning on the transistor 16 for a predetermined time width, gradually increase the conduction time to increase the supply current to the heating coil 15. It is configured. The input current control means 19a and the component applied voltage and the current control means 19b are provided with a D / A converter so that the detection voltage of the input current detection circuit 17 or the detection voltage of the collector voltage detection circuit 20 is not applied more than a predetermined set value. A drive circuit (PWM circuit) 27 is configured to control the conduction time width of the switching transistor 16 via 28.

Next, the operation of the induction cooking device configured as described above will be described with reference to the flowchart of FIG. When a power supply switch is turned on with a predetermined standard pan serving as a load and placed on top of the heating coil 15, the microcomputer 19 determines whether or not the data of the set value storage circuit 22 is within a predetermined range (step 30). ). If the data is not within this range, an abnormal value is stored in the set value storage circuit 22,
There is a possibility that data has been set under unset, abnormal load, or abnormal power supply conditions. If it is determined at this time that the correction start switch 23 has not been pressed (step 31), an alarm is issued. Then, the user is informed that no setting has been made (step 37). If the correction start switch 23 is on in step 31, that is, if the user turns on the correction start switch 23 to set the maximum input current or the maximum value of the collector applied voltage, the input current of the microcomputer 19 The control means 19a compares the set value set internally (ROM) with the detection data of the second input current detection circuit 24, and controls the output so that the input current becomes I _VMAX (step 32). Where I
_VMAX is the transistor under the specified load and supply voltage conditions.
This is the input current when the collector voltage (V _CE ) applied to 16 reaches the maximum set value. When the input current reaches I _VMAX ,
The maximum component applied voltage correction means 19d reads the output data of the collector voltage detection circuit 20 and stores it in the set value storage circuit 22 (Step 33). Next, the input current control means 19a compares the detection data of the second input current detection circuit 24 with the set value set in the microcomputer 19 (ROM), and outputs an output so that the input current becomes I _INMAX. Control (step 34). Here, I _INMAX is a maximum input current set value. When the input current becomes I _INMAX , the maximum input current correction means
In step 19c, the output data of the first input current detection circuit is read and stored in the set value storage circuit 22 (step 35), and the setting operation of the maximum input current and the maximum collector voltage ends. If the data of the set value storage circuit 22 is within the predetermined range in step 30, it is determined that the setting of the maximum input current value and the setting of the maximum collector voltage value have been completed, and the maximum input current correction Means 19c and maximum component applied voltage correction means 19d
Reads the set value of the set value storage circuit 22 and stores the maximum set value V of the input current control means 19a in an internal storage circuit (RAM).
_It is stored as _{IMAX and} as the maximum set value V _CEMAX of the component applied voltage / current control means 19b (step 38). Next, the microcomputer 39 sets the output to Lo based on the internal set value (step 39), and the detected voltages of the collector voltage detecting circuit 20 and the first current detecting circuit 17 become the maximum set values V _CEMAX and V _CE respectively. If it is not larger than _INMAX , the output is increased by a predetermined amount, and finally the output is stabilized at any set value within a range not _exceeding the maximum set value of both detection circuits (steps 40 to 45). When the correction start switch 23 is pressed again (step 44), the process returns to step 32, and the maximum value setting procedure is executed.

According to the configuration of the above embodiment, a predetermined load is applied to the heating coil.
Calibrated second input current detection circuit mounted on top of 15
By inputting the detection circuit 24 to the input terminal 26 via the A / D converter 25 and pressing the correction start switch 23, the maximum value of the input current of the frequency converter and the switching transistor 16 The maximum value of the collector voltage can be set. A second input current detection circuit accurately calibrated so that the correlation between the input current and the detection output becomes a predetermined value.
According to 24, the input current can be accurately controlled to a predetermined value, and the output of the two internal detection circuits at this time is controlled by using the data of the two internal detection circuits as the maximum set values of the internal detection circuits. It is possible to accurately set a predetermined set value irrespective of a detected voltage error due to a variation in electrical characteristics of components. In the present embodiment, the storage circuit 22
If the data set in is not within the predetermined range and the correction start button 23 is not pressed, an alarm is issued and the heating operation is not performed, so the maximum input current setting circuit 17 or the maximum value of the collector voltage detection circuit is not detected. Destruction of components due to over-output operation of the frequency converter due to unset can be prevented. Further, in the present embodiment, since a non-luminous storage element is used as the set value storage circuit 22, when the power supply voltage is turned off and then turned on again, the maximum value is set again. There is an effect that there is no need.

Effects of the Invention As is apparent from the description of the embodiments, the present invention has the following effects.

If a predetermined signal is input from the output correction start signal input means, the input current is controlled to a predetermined value based on the signal detected by the second input current detection means outside the equipment, and then the internal Storing the output signal level of the first input current detection means or the component applied voltage and the output signal level of the current detection means mounted on the set value storage means;
Thereafter, the first internal device based on the stored setting values is used.
Since the output is controlled by the detection circuit or the component applied voltage / current detection circuit, the setting of the maximum value can be automatically performed with a simple operation with high accuracy.

If a non-luminous storage element is used as the set value storage element, it is not necessary to correct the set value again after the power of the device is turned off.

[Brief description of the drawings]

1 and 2 are block diagrams showing an embodiment of the present invention, FIG. 3 is a flowchart showing an example of a program for setting an input current and a maximum value of a voltage applied to components, and FIG. 4 is a conventional example. FIG. 9: frequency conversion device, 17: first input current detection means, 19a: input current control means, 19b: component applied voltage,
Current control means, 19c ... maximum input current correction means, 19d ...
Maximum component applied voltage correction means, 20: component applied voltage and current detection means, 22: set value storage means, 23: output correction start signal input means, 24: second input current detection means.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiaki Iwai 1006 Odakadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-27089 (JP, A) JP-A-60- 160591 (JP, A) JP-A-60-170184 (JP, A)

Claims (1)

(57) [Claims] 1. A frequency converter, a first input current detecting means of the frequency converter or a means for detecting a voltage or current applied to a component of the frequency converter, and a first input current detecting means. Input current control means for controlling the input current by comparing the input signal level with the signal level stored in the set value storage means, or the detected signal level of the component applied voltage and current detection means and stored in the set value storage means. A voltage / current control unit for controlling a voltage or a current applied to the components of the frequency converter by comparing the signal level with the output signal level, and an output correction start signal input unit. When the signal of is input,
The input current control means controls so as to obtain a predetermined input current based on an output signal of a second input current detection circuit external to the device, and at this time an output signal level of the first input current detection means or An induction heating cooker configured to store the component applied voltage and the output signal level of the current detection means in the set value storage means by the maximum input current correction means or the maximum component applied voltage correction means.