JPS60193290A - 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 (a) Field of Industrial Application The present invention relates to an induction heating cooker having a temperature control device.

(b) Prior art Conventionally, this type of induction heating cooker
As disclosed in Publication No. 835, etc., on-off control is performed using a detection means such as a thermistor, but the temperature range from the on temperature to the off temperature is wide, and for example, when cooking stewed food, In this case, it was necessary to simmer for a long time at a simmering heat, which was not suitable for cooking at a temperature as constant as possible.

(c) Objective The object of the present invention is to provide an induction heating cooker having a highly accurate temperature control device.

B) Structure The present invention provides a series circuit comprising a sensing element for detecting the temperature of the top plate and a first switching means, and a series circuit comprising a variable resistor for determining the lower limit or upper limit of the temperature and a second switching means. , a series circuit consisting of a temperature-compensating resistor, and a third switching means; these series circuits are connected in parallel, and a divided voltage is digitally calculated when each of the first to third switching means is operated. an A/D converter that converts the voltage into a voltage; a control section that generates a signal that controls the operation of the induction heating coil according to the output digital voltage of the A/D converter; and the first to third switching means. The oscillators are operated alternately.

(e) Examples Hereinafter, the induction heating cooker of the present invention will be explained based on FIGS. 1 to 4.

In FIG. 1, (1) is an induction heating cooker according to an embodiment, and is equipped with a top plate (2) made of an insulating plate such as a ceramic plate on the upper surface and an operating section on the negative side. (
3) is a temperature/output selector switch, and (4) is a temperature/output setting knob that also serves to turn on/off the power, and consists of a slide switch. (5) is a power indicator lamp that lights up when the power is turned on;
(6) is a temperature operation indicator lamp that lights up when the temperature control circuit is in operation;

In Figure 2, (8) is a commercial AC power supply, (9) is a power switch driven by the temperature/output setting knob (4), and when this is closed, AC power supply (8) is energized to power supply circuit a. do. This power supply circuit (8) consists of a rectifier circuit that converts alternating current into pulsating current or direct current, and the power supply voltage rectified here is:
Supplied to a high frequency inverter circuit.

The high frequency inverter circuit includes an induction heating coil az, a resonant capacitor (not shown), a power switching element (not shown), and the like.

This high-frequency inverter circuit (1υ) oscillates in synchronization with a high-frequency pulse signal of approximately 20 to 40 KHz applied to the power switching element, and a high-frequency alternating current of the same frequency flows through the induction heating coil (L). This alternating current generates a magnetic field. Then, the magnetic cooking pot a3 placed within this magnetic field is heated.α(a) is an auxiliary power supply to which an AC power supply (8) is supplied via a step-down transformer (not shown), and a control unit (described later) (
This is for driving L4 and the inverter drive circuit E. The inverter drive circuit Qe generates drive pulses for controlling on/off the power switching elements of the high frequency inverter circuit (11), and an LED is provided on its input side as a power indicator lamp (5).

FIG. 3 is a detailed diagram illustrating one embodiment of the control section (10), in which (17) is a first transistor as a switching means, and αQ is a detection sensor attached below the pot device on the back side of the top plate (2). An element such as a thermistor is a negative resistance characteristic element whose resistance value decreases as the temperature rises.Q9
is a second transistor as a switching means, and the collector of this transistor (19+) is equipped with a variable resistor ( whose resistance value changes in conjunction with the temperature/output setting knob (4)).
b) is connected. (2) is a third transistor as a switching means, and a resistor (2) for setting a differential for temperature compensation is connected to the collector of the transistor (21).

The emitters of the first to third transistors uus (2υ) are grounded, and the collectors are connected to a common resistor (c) via the thermistor U, variable resistor, and resistor, respectively. The resistor (C) is connected to an auxiliary power source αa.

The foundation is an A/D device that converts analog voltage into digital voltage.
It is a converter.

(E) is a microcomputer as a control unit; 2ω is the A/D converter (24);
A signal for operating or stopping the inverter drive circuit aυ is outputted from the output terminal d based on the digital voltage outputted by the inverter drive circuit aυ. Further, in one embodiment of the present invention, the description will be continued assuming that the microcomputer (c) has two built-in oscillators. Pulse output terminal c! of the oscillator in the microcomputer (c)! The bases of the first to third transistors (17) H (2υ) are connected to the amplifier (A) through the respective resistors (27) (support) ℃0, and the pulses output from the oscillator generate , these transistors (17) (19clI) are operated alternately.In addition, the microcomputer (c) contains the first to third transistors.
Transistor α7)al (A corresponding to when 2υ is on)
It is provided with first to third registers (to) 0υ03 consisting of a RAM and the like for storing the output of the /D converter. In addition, the microcontroller (two are connected to the display unit) via the amplifier (towards).
is connected to.

The present invention has the above-mentioned configuration, and its operation will be explained below. First, when the oscillator in the microcomputer (c) outputs a first pulse to turn on the first transistor (17), the resistance (c) and the sensing element 08) proportional to the temperature of the top plate (2) are activated. The divided voltage with the resistance value is converted into a digital voltage by an A/D converter (incorporated) and then stored in the first register (to) in the microcomputer (c), and the digital voltage is converted into the current pot α. ■ Supplying a signal as temperature to the display unit 134) via the amplifier (2) and displaying the LED (LE
D,) ~ (LED?) is turned on. Next, the second transistor α9 is turned on by the second pulse output from the oscillator, and the resistance value is linked to the position where the resistance (c) and the temperature/output knob (4) are arbitrarily set by the user. resistance(
The divided voltage (off voltage) due to the A/D converter (
After being converted to digital voltage by the microcomputer Ci!
It is stored in the second register 6υ in ω. Next, the third transistor (2
! υ is activated, and the divided voltage between the resistance (c) and the differential resistance that determines the temperature range is converted into a digital voltage by an A/D converter (incorporated), and then the microcontroller (c)
The data is stored in the third register 0 of the memory.

The digital voltage, which is the temperature of the top plate (pan, etc.) (2), is stored in the first register (to) in the microcomputer (251), and the temperature/output knob (4) is stored in the second register Gυ.
), the digital voltage corresponding to the temperature set by the second register is stored in the third register. (to) is A, the digital voltage of the second resistor C (1) is C, and the digital voltage near 0 of the third register is C. As shown in the flowchart, a comparison operation is performed, and if B-A≧θ, an off signal is output from the output terminal (c) to the inverter drive circuit αD, and (B-A(θ)
If it is, the current state (on if it is on, off if it is off) is maintained, and if ((B+C)-A≦θ), it sends an on signal to the drive circuit I. If ((B+C)-A>θ), the current state is maintained.

One operation is completed as described above, and is repeated thereafter.

The present invention is as described above, and the temperature of the top plate (2), the arbitrary temperature set by the temperature/output setting knob (4), and the resistor (2) that determines the differential.
′;! The microcomputer (
Temperature control is performed by comparison calculation in (c), so
By setting the resistance value of the resistor (221) that determines the differential to a desired resistance value, the set temperature can be maintained with high accuracy.

Furthermore, the present invention is not limited to the configuration described above,
The variable resistor may be configured to be turned on with the lower limit level. Further, as shown in FIG. 5, the resistance (2) that determines the upper limit and the resistance (2) that determines the lower limit (c) Effects The present invention is as described above, and has the following effects.

■ It can be easily corrected by replacing the detection means with one with different characteristics.

■ Differential can be set freely by setting the resistance value of the temperature compensation resistor.

[Brief explanation of drawings]

Fig. 1 is an external perspective view of the expansion heating cooker of the present invention, Fig. 2 is a circuit diagram explaining one embodiment, Fig. 3 is an enlarged view of the main part of Fig. 2, and Fig. 4 is the operation of the control section. It is a flowchart figure which shows. FIG. 5 is a diagram showing another embodiment. (113...High frequency inverter circuit, α...induction heating coil, (1...control unit, QS-...thermistor, Foundation)...A/D converter, (c)...・
microcomputer. Applicant Sanyo Electric Co., Ltd. and one other agent Patent attorney Shizuo Sano, Figure V, Figure 2, Figure 4

Claims (1)

[Claims] (1) A sensing element that detects the temperature of the top plate and a first
a series circuit consisting of a variable resistor that determines the lower or upper limit of temperature and a second switching means; a resistor that performs temperature compensation;
an A/D converter that connects these series circuits in parallel and converts divided voltages into digital voltages when the first to third switching means are respectively activated; , a control section that generates a signal for controlling the operation of the induction heating coil according to the output digital voltage of the A/D converter, and an oscillator that alternately operates each of the first to third switching means. Heating cooker.