JPS63168988A - Relay driver of electric 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 The present invention relates to a relay driving device that has a plurality of electric heating elements and selectively switches and uses one of them.

BACKGROUND OF THE INVENTION Conventionally, an electric hot plate, as shown in FIG.
The temperature of the plate is detected by a temperature detection means 1 such as a bimetal thermometer, and the temperature of the plate is controlled by mechanically opening and closing the contacts. Further, the electric heating elements 2 and 3 arranged as shown in FIG. 2 can be switched and energized by a changeover switch 4.

On the other hand, in recent years, with improvements in electronic technology, electric hot plates equipped with a temperature control device that combines an electronic circuit and a negative characteristic thermistor have been considered in order to improve control temperature. The electric heating elements are selectively switched using relays to generate heat individually. An example of such a configuration is shown in FIG.

As shown in FIG. 3, relay contacts 4.6 are connected in series to the electric heating elements 2 and 3, the first relay contact 4 is controlled to open and close by energizing the relay coil 7 by the transistor 6, and the second The relay contacts 6 are controlled to open and close by energizing a relay coil 9 using a transistor 8.

16 is a holding circuit for selectively using one of the heaters, which can be selected by the input temperature switch 17; 18 is a temperature control circuit, which controls the temperature between both ends of the thermistor 19 with respect to the 3t/-7 reference voltage; Temperature control is performed by changing the voltage of , and the control temperature can be made variable by changing the reference voltage externally.

Note that 10 and 11Fi in the figure are resistors and diodes, which generate a DC voltage for driving the relay across the capacitor 12. Similarly, the control circuit 16,1 is constructed using a 13°14.15 DC resistor and a diode capacitor.
7.18 power is obtained.

Problems to be Solved by the Invention However, in the configuration shown in FIG. There was a problem that 2°3 were energized at the same time. These electric heating elements 2, 3
Each wire has a capacity of about 12 A, and if two wires are energized at the same time, a large current of 24 A will be generated, causing the power wire to generate heat and creating a risk of fire.

The present invention takes into account the above-mentioned conventional problems and attempts to improve safety by preventing the two heating elements from being energized at the same time.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention makes the power supply of the relay drive circuit independent for each relay, and connects it to a relay contact different from the relay contact to be driven. It is configured to be generated via a heater.

Operation The present invention provides that when a relay contact closes with the above-described configuration, the power of the other relays is extinguished, so that the other relays are guaranteed to be turned off, and therefore a plurality of electrical connections are made.

Simultaneous energization of the heating elements will be prevented.

Example FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In Fig. 1, numerals 2 and 3 are electric heating elements connected to a power source, and each energizing circuit has a relay contact 4.
, 6 are inserted. The relay contact 6 is controlled to open and close by a relay coil 7, the relay contact 46 is controlled to open and close by a relay coil 9, the relay coil 7 is driven by a transistor 6, and the relay coil 9 is driven by a transistor 8. .

Each relay drive circuit has an independent power supply and a resistor of 10.2
0. Diodes 11, 21, capacitors 12, 23
It is made by. In particular, the power supply for the relay coil 9 is obtained via the electric heating element 3 connected to the uncorresponding relay reading point 6, and the power supply for the relay coil 7 is obtained via the electric heating element 2 connected to the uncorresponding relay contact 4. I'm trying to get through it. In addition, resistors 13, 14, and 15 in the figure.

A power source for the holding circuit 24 is created by a diode and a capacitor. 26 is a switch for selecting which relay to drive, and 26 is a switch for varying the set temperature. 27 is a temperature control device composed of a voltage comparator or the like, and 28 is a temperature detection element composed of a negative characteristic thermistor.

The operation of the circuit configured as described above is as follows.

Now, when the power is connected and the electric heating element 2 is energized to 6 h/h, input is made from the switch 26, and the holding circuit 2 is turned on.
4, the transistor 8 is activated and energizes the coil 9, which closes the contact 4 and energizes the electric heating element 2. After this,
As the temperature rises, the contact 4 is turned on and off according to the output of the voltage comparator connected to the negative characteristic thermistor 28, and the temperature is held constant.

In the case of the electric heating element 3, the transistor 6 is driven by the holding circuit 24 to perform the same operation.

Now, in this configuration, if we look at the case where the contacts 4 are welded or the transistor 8 is short-circuited, in this case the electric heating element 2 is energized, but when trying to drive the transistor 6, the capacitor 12 Contact 6 cannot be closed because no voltage is generated across it.

If the contacts 6 are welded or the transistor 6 is short-circuited, no voltage will be generated across the capacitor 23 as well. Therefore, simultaneous energization of the two electric heating elements is prevented.

As is clear from the description of the embodiments above, the effects of the present invention are as follows:
1 According to Akira, the relay is selectively driven by an electronic circuit to energize one of the plurality of electric heating elements, and even if a failure occurs, multiple heaters will not be energized at the same time. It is possible to prevent a risk of fire or the like due to heat generation due to the generation of a large current.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram showing the configuration of the present invention, Fig. 2 a, b
3 is a circuit diagram and a top view showing a conventional example, and FIG. 3 is a circuit diagram showing a conventional example. 2.3...Electric heating element, 4,6...Relay contact, 6.8...Transistor, 7,9...
・・Relay coil.

Claims (1)

[Claims] The drive circuit for each relay includes a plurality of electric heating elements connected to a power source, a relay contact connected in series to each of the electric heating elements, a plurality of relay drive circuits corresponding to the relay contacts, and a drive selection circuit. A relay drive device for an electric cooker configured to obtain power through an electric heating element connected to a relay contact on a different side from the relay contact that drives the relay.