JPS60115190A - Induction heating cooking device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a control circuit for an induction heating cooking apparatus.

<Prior art> In general, induction heating cooking devices perform constant current control based on the input current on the primary side of an AC power source. If you heat food with a pot that has a characteristic that the heating coil current on the secondary side is large compared to the input current of the pot, the internal heat generation will increase, causing the thermocircuit to malfunction.

Therefore, in the past, the use of this type of pot was prohibited, and a method was proposed in which the output was corrected by the voltage across the resonant condenser.
Methods have been considered to identify stainless steel chains based on the timing of switching transistors and suppress the output, but these methods have drawbacks such as complicating the control circuit and making the determination circuit unstable.

<Purpose> The present invention has been made in view of the above-mentioned points. In addition to detecting the coil current and suppressing abnormal rises in the internal temperature of the induction heating cooking device, when using a pot that has the characteristic that the input current on the primary side becomes larger than the heating coil current on the secondary side, AC Its purpose is to detect the input current on the primary side of the power supply and control the output.

<Configuration> In order to achieve the above-mentioned object, the present invention includes means for detecting the input current on the primary side of the induction heating cooking device, and selects the higher output value of the rain detection means. It is characterized by being introduced into a control circuit.

<Example> Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a control circuit block diagram of an induction heating cooking apparatus showing an embodiment of the present invention, and FIG. 2 is an electrical circuit diagram of the main parts in FIG. 1.

In the figure, 1 is an AC power supply, 2 is a rectifier diode, 3 is a choke coil, 4 is a smoothing capacitor, and 5 is an NPN transistor. By switching the transistor 6 at a high frequency of 20 to 30 KH2, an alternating magnetic field is applied to the high frequency current flowing through the heating coil 7. This is the drive circuit that generates the signal. 8 is a resonant capacitor, and 9 is a damper diode. 10 is a current transformer that detects the current flowing in the primary side of the AC power supply 1, 11 is a current transformer that detects the current flowing in the heating coil lv7 on the secondary side, and each is a first current-voltage conversion circuit 12. , are connected to the second current-voltage conversion circuit 13. 14 is the above current-voltage conversion circuit 12.13
This control circuit 15 is an OR circuit that introduces the larger voltage value among the output values of the heating coil lv7 into the control circuit 15.
The pulse width of the oscillation circuit section that controls the high frequency current flowing through the NPN converter 6 is set to control the ON time of the NPN transducer 6.

FIG. 2 shows a specific circuit example of the current-voltage conversion circuit 12.13, and 16.17 indicates the current transformer 10.
11 is a load resistor connected in parallel, 18.19 is a rectifier diode, 20.21 is a smoothing capacitor, 22.2
3 is a resistor for discharging the capacitor. Diodes 24 and 25 form an OR circuit 14 whose anodes are connected to the resistors 22 and 23 and whose cathodes are connected to the control circuit 15, respectively.

Next, the operation of the present invention having the above configuration will be explained.

First, when heating is started by placing a pot made of high-grade stainless steel such as 18-10 stainless steel above the heating coil/I/7, in this case, the input current detected by the current transformer 10 Since the input current detected by the sictive transformer 11 is larger, in the circuit shown in FIG. Therefore, the diode 24 is turned off, but the diode 25 is turned on and the control circuit 15 detects the output voltage at the zero point of the load resistor 23, that is, the current flowing through the heating coil 7 on the secondary side. The pulse width of the output can be set. Therefore, in the case of a stainless steel pot, the current flowing through the heating coil 7 can be detected by the current transformer 11.

When the heating coil current on the secondary side is relatively small compared to the primary input current, such as with an enamel pot, the current detected by the Karen 1-1-Lanne 10 provided on the primary side is The output voltage at the zero point of the load resistor 22, which is the converted voltage, is introduced into the control circuit 15 via the diode 24.

In this way, the input current detected by the current transformer is divided into the primary side and the secondary side according to the characteristics of the pot, and is detected independently, and the voltage level of the higher output is adopted. The output of the heating coil can be controlled.

<Effects> As described above, the present invention includes a means for detecting an input current on the primary side of an induction heating cooking apparatus and a means for detecting a heating coil current on the secondary side, and the rain detecting means Since the output of the heating coil is controlled by selecting the higher output value of゛The output of the induction heating cooking device can be controlled by comparing the magnitude of the current and the current on the primary side and using the current that flows in large quantities, so the current flowing through the heating coil is abnormally large. This eliminates the inconvenience of internal heat generation, and by adding a simple circuit configuration, the number of types of pots that can be used increases, and the output can be easily controlled according to the characteristics of the pot, making it easier to use. It is possible to provide an induction heating cooking device with good practical value.

[Brief explanation of the drawing]

FIG. 1 is a control circuit block diagram of an induction heating cooking apparatus showing an embodiment of the present invention, and FIG. 2 is an electrical circuit diagram of the main part of FIG. 1. 1... AC power supply, 5... Drive circuit, 6... NP
N transistor, 7... Heating coil, 8 Resonant capacitor, 10.11... Current transformer, 12...
- 1st current-voltage conversion circuit, 13. 2nd current-voltage conversion circuit, 14... OR circuit, 15... control circuit.

Claims (1)

[Claims] 1. Equipped with means for detecting an input current on the primary side of the induction heating cooking device and means for detecting a heating coil current on the secondary side,
An induction heating cooking device characterized in that the output of the heating coil is controlled by selecting the higher output value of the rain detection means.