JPS61153991A - Adaptive load detector for induction heating cooker - 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 Field of Industrial Application The present invention relates to an appropriate load detection device for an induction heating cooker used in a general household.

2. Description of the Related Art Conventionally, this type of suitable load detection device uses only a well-known small object detection means to determine a load other than the small object load as an appropriate load, or, for example, uses a magnetic load detection means composed of a permanent magnet and a switch and the small object. It was common to use magnetic loads other than small object loads as suitable loads when used in combination with a detection means.

Problems to be Solved by the Invention However, there is a problem in that aluminum foil, which is not detected as a small load by the conventional suitable load detection device of the former, is judged to be a suitable load and becomes red hot, which is dangerous, and the latter is dangerous. Aluminum foil does not become red hot in the device, but for example 5
Since non-magnetic suitable loads such as US304 are judged as unsuitable loads and are not heated, there is a problem in that the usable loads are limited.

In view of the above-mentioned problems, the present invention is an induction heating cooker that can determine aluminum foil as an inappropriate load and non-magnetic load as an appropriate load, thereby increasing the safety and heating range of the induction heating cooker. The present invention provides an appropriate load detection device.

Means for Solving the Problems In order to achieve this object, the suitable load detection device for an induction heating cooker of the present invention includes a heating coil, a resonant capacitor,
a magnetic load detection means, a small object detection means for detecting a small object load, a resonance period detection means for detecting a resonance period of the resonant capacitor of the heating coil and the resonant capacitor, and a voltage of the heating coil and an input current of the induction heating cooker. and a coil voltage/input current comparing means for comparing the values, the small object detecting means distinguishes a small load, and the magnetic load detecting means discriminates whether a load other than a small object is a magnetic load or a non-magnetic load. For magnetic loads, it is determined that the load is suitable, and for non-magnetic loads, the resonance period detection means and the coil voltage
The configuration is such that the non-magnetic suitability load is determined by the input current comparison means.

Effect: With this configuration, a non-magnetic suitable load such as SUSgo4 can be determined as a suitable load, and aluminum foil can be determined as an unsuitable load.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a device applied to an appropriate load detection device for an induction heating cooker according to an embodiment of the present invention.

In FIG. 1, 28 is a small object detection means that outputs an L signal to a small load, 60 is a magnetic load detection means that outputs an H signal to a magnetic load composed of, for example, a permanent magnet and a switch, and 36 is an induction device. Resonance period detection means for detecting whether the resonant period T of the heating coil of the heating cooker and the resonant capacitor is longer or shorter than a certain value; 47 indicates the voltage v0 of the coil;
The resonance period detection means 3 and the coil voltage/input current comparison means 47 both output an L signal to an unsuitable load. 51 is an AND circuit whose inputs are the output of the resonance period detection means 36 and the output of the coil turtle pressure/input current comparison means 47; 62 is an OR circuit whose inputs are the output of the magnetic load detection means 60 and the output of the AND circuit 51; 63 is an AND circuit which receives the output of the small object detection means 28 and the output of the OR circuit 62, and the output of the AND circuit 63 is an appropriate load detection signal.

FIG. 2 is a flowchart illustrating the operation of the embodiment of FIG. The operation of the embodiment shown in FIG. 1 will be explained using FIG. 2.

First, when a load is placed on the induction heating cooker, the small object detection means 28 determines whether the load is a small object or not, and as shown by block SD in the flowchart of FIG. It is determined that it is a cargo. For loads other than small items, the magnetic load detection means 6o determines whether it is a magnetic load or a non-magnetic load. As shown by the block MD in FIG. 36 and coil voltage/input current comparison means 47 to determine whether the load is inappropriate, and as shown in FIG. 2, loads that are not determined to be inappropriate are determined to be appropriate loads.

Next, the operations of the resonance period detection means and the coil voltage/input current comparison means will be explained using the characteristic diagrams shown in FIGS. 3 and 4. FIG. 3 is a characteristic diagram illustrating the operation of the resonance period detection means, in which the horizontal axis represents the input current I of the induction heating cooker, and the vertical axis represents the resonance period T.

The characteristic S shown by a solid line indicates the characteristic of a non-magnetic suitable load such as 5US304, and the characteristic A shown by a broken line indicates the characteristic of aluminum foil.

t indicates the thickness of the non-magnetic load tl〈t2〈t3〈t
There is a relationship of 4<15. d is the area of the aluminum foil dl
There is a relationship of 〈d2〈d3〈d4〈d6. The resonance period detection means determines that the load in the diagonally shaded area NTD in FIG. 3 is inappropriate. In other words, aluminum foil with an area of d3 or more is determined to be unsuitable. FIG. 4 is similar to the characteristic diagram for explaining the operation of the coil voltage/input current comparing means. If a load determined to be unsuitable by either of the coil voltage/input current comparison means is considered to be an unsuitable load, NTD NCI
'In other words, the entire area of aluminum foil is determined to be an inappropriate load. Further, all non-magnetic loads such as NTD NCI are determined to be suitable loads.

As described above, in the embodiment shown in FIG. 1, small object loads and aluminum foil are determined to be inappropriate, and magnetic loads other than small objects and non-magnetic loads other than small objects and other than aluminum foil are determined to be appropriate.

FIG. 6 is a circuit diagram showing an embodiment of the appropriate load detection device for the induction heating cooker shown in FIG. 1. In FIG. 6, 10 is an AC power supply, 11 is a full-wave rectifier, 12 is a smoothing capacitor,
13 is a heating coil, 14 is a resonant capacitor, and 16 is a switching element, which constitutes an inverter. 16.17
The current transformer detects the input current of the inverter, that is, the input current I of the induction heating cooker.

18 is a resistor, 19 is a diode, 20 is a capacitor, 2
1 is a resistor that generates a DC voltage proportional to the input current I. 22 and 23 are resistors that divide the voltage VC across the heating coil 130, and together with the diode 24, capacitor 25, and resistor 26, generate a voltage proportional to the coil voltage VC. 27 is a comparator. A portion 28 surrounded by a one-dot chain line is small object detection means that determines that the load is a small object and outputs an L signal when the coil voltage v0 is higher than the value determined by the input current factor 1. 29.30 is the coil voltage V. A resistor 31 is a comparator that determines whether the coil voltage VC is positive or negative, and the output of the comparator 31 is an open collector. 32 is an integrating capacitor, 33 is a constant current source for charging the capacitor 32, 34 is a DC power supply with a voltage v1, and 35 is a comparator for comparing the voltage of the capacitor 32 and the voltage of the DC power supply 34. A portion 36 surrounded by a one-dot chain line is a resonance period detection means that determines that the load in the region NTD in FIG. 3 is inappropriate and outputs an L signal. FIG. 6 shows the operation of the resonance period detection means.

The period during which the coil voltage vc becomes positive is the resonance period T. Coil voltage V. is positive, the comparator 31
Since the output of the comparator 32 is open, the voltage of the comparator 32 increases in proportion to time due to charging from the constant current source 33. V is set so that when T becomes equal to TD shown in Fig. 3, the voltage of the capacitor 32 becomes vl.If a load in the region NTD of Fig. 3 is placed, the voltage shown in Fig. 6 is set. As such, the output of the comparator 36 becomes L, and it is determined to be inappropriate.

37, 38 are resistors that divide the coil voltage VC, a diode 39, a capacitor 40. A direct current voltage proportional to the coil voltage vc is generated across the resistor 41. 42 is a resistor, 43 is a diode, 44 is a capacitor, and 45 is a resistor, which generates a DC voltage proportional to the input current I. 4
6 is a comparator. Part 47 surrounded by a dashed line
4 is a coil voltage/input current comparison means that determines that the load in the region Nci in FIG. 4 is inappropriate and outputs an L signal. 48
numeral 49 represents a switch that is non-conductive to the magnetic load; A portion 6o surrounded by a dashed line is a magnetic load detection means that outputs an H signal to a magnetic load. 61 is an AND circuit, 62 is an OR circuit, and 63 is an AND circuit. As can be easily understood, the specific circuit example shown in FIG. 5 realizes the operation of the embodiment shown in FIG.
becomes H, and the detection output S0 becomes L for an inappropriate load.

Effects of the Invention As is clear from the above, the suitable load detection device for an induction heating cooker of the present invention is achieved by using a resonance period detection means and a coil voltage/input current comparison means in combination with the small object detection means and the magnetic load detection means. , magnetic suitability load plus 5US30
Since the non-magnetic suitable load such as No. 4 can be determined as the suitable load, the safety of the induction heating cooker and the possible heating range can be expanded.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an appropriate load device for a heating cooker which is an embodiment of the present invention, and FIG. 2 is a flowchart explaining the same operation.
3 and 4 are characteristic diagrams explaining the same operation, FIG. 6 is a circuit diagram of the same, and FIG. 6 is a waveform diagram in the circuit of FIG. 6. 28... Small object detection means, 60... Magnetic load detection means, 36... Resonance period detection means, 4
7... Coil voltage/input current comparison means. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3

Claims (1)

[Claims] a heating coil, a resonant capacitor, a magnetic load detection means, a small object detection means for detecting a small object load, a resonance period detection means for detecting a resonance period of the heating coil and the resonance capacitor, and a voltage of the heating coil and induction heating. It has a coil voltage/input current comparison means for comparing the input current of the cooker,
The small object detection means determines a small object load, and for loads other than small objects, the magnetic load detection means determines whether the load is a magnetic load or a non-magnetic load. An appropriate load detection device for an induction heating cooker that determines an appropriate non-magnetic load for the load using the resonance period detection means and the coil voltage/input current comparison means.