JPS59175581A - Power controller - 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 the Invention The present invention relates to household cooking appliances such as rice cookers, and particularly to a power control device that performs on/off control of these heaters.

Conventional configurations and their problems/points In recent years, household electric cooking appliances such as rice cookers have been equipped with drive control circuits equipped with microcomputers to perform fine-grained power control according to a certain program by turning the power control on and off. Attempts are being made to improve cooking performance by doing so.

Hereinafter, a conventional cooking device as described above will be explained with reference to the drawings.

FIG. 1 particularly shows a jar rice cooker equipped with a microcomputer as an example of a conventional cooker. In Figure 1, 1 is a power plug, 2 is a power switch, 3 is a temperature fuse, 4 is a line capacitor for noise reduction, 5 is a lower heater with a large power installed at the inner bottom of the main body, and 6 is an inner surface of the main body. 7 is a lid heater provided on the lower surface of the lid, 8 is a relay contact, 9 is a coil, 10 is a lower heater
6, and a triac for keeping warm that controls the side heater 6 and the lid heater 7 connected in series in a parallel circuit, 11
is a microcomputer, and this output turns on and off Citra/Jister 12 and 13 to drive the relay and triac. Reference numeral 14 designates an output display section, 16 a temperature input section for the pot consisting of a heat-sensitive element that contacts the pot, and 16 a thermoswitch that detects the completion of rice cooking. Note that the resistor 17, diode 18, resistor 19, Zener diode 20, and electrolytic capacitors 2''l and 22 constitute a power source for this drive control circuit.

The operation of the jar rice cooker configured as above will be explained below.

When cooking rice without sweetness, when the thermo switch 16 is turned on, the microcomputer 11 goes into rice cooking mode.
While the relay 8 is turned on and off by a single word from the pot temperature input section 15, the lower heater 5 is energized and rice is cooked through a step of absorbing water from the rice and a step of automatically determining the amount of rice to be cooked. When the rice cooking is finished, the thermo switch 16 shuts off, and the microcomputer 11 detects the end of the rice cooking mode, turns off the relay 8, stops the electricity supply to the lower heater, and finishes the rice cooking. Thereafter, only the lower heater 5 is temporarily energized, and after a good cooking and uneven cooking process, the mode shifts to the heat retention mode.

In the maintenance mode, the triac 10 is turned on and off in response to a signal from the pot temperature input section, and energizes the lower heater 6, side heater 6, and lid heater 7 to perform a maintenance operation.

However, in the above configuration, since on/off control of the large current is performed by the relay contact 8, it is necessary to increase the capacity of the relay contact 8, and when the relay contact 8 reaches the end of its life, the contact will weld. In this case, a large current is continuously applied and the temperature fuse 3 is activated.

The above disadvantages can be improved by using a power semiconductor for relay 8, but in that case, cooling fins etc. will be required, which will increase the cost, and the parts will become larger and will not fit inside the cooker. There was a problem that made it difficult to incorporate.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a power control device that solves the above problems and can control large currents, has high reliability, and can be realized at low cost.

Structure of the Invention In the cooking device of the present invention, the control means is constituted by a parallel circuit of a relay contact and a power semiconductor such as a triac, and further includes a continuity detection circuit for the power semiconductor and a relay coil drive circuit, The relay coil drive circuit is connected to operate based on the conduction of the power semiconductor + the output of the output circuit, and a momentary firing circuit 5 of the power semiconductor is further provided to cause temporary firing when the operation of the relay coil driving circuit ends. Since the circuit is designed to operate, when all the triacs are fired, the υ rule is necessarily driven, and a highly reliable power control means can be obtained.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to all the drawings.

FIG. 2 shows a block diagram of a power control device as an embodiment of the present invention.

In FIG. 2, 30 is a power semiconductor, 31 is a relay contact, 32 is a continuity detection circuit for the power semiconductor, 33 is a relay coil drive circuit, 34 is an ignition circuit for the power semiconductor 30, 35
is a power semiconductor single-time firing circuit.

Each block is connected as shown in the figure, and when the power semiconductor terminal voltage detection circuit 32 operates, the relay coil drive (b) path 33 operates, and when the relay coil operation is completed, the temporary ignition circuit 35 is configured to work.

FIG. 3 is an electric circuit showing an example of a specific configuration of its main parts. 4Q is the power plug, 41 is the power switch,
42 is a temperature fuse, 43 is a heater load, 44 is a relay contact, and 45 is a triac which is one of the power semiconductors.

A current transformer 46 is connected to the T2 terminal of the triac 45.
A conduction detection circuit 32 of the triac 45 is configured by a capacitor 48, a transistor 5o, etc. via a diode 47.

Note that the transistor 50 also serves as a relay coil and the drive circuit 33, and drives the link coil 52 together with the diode 51.

Reference numeral 53 denotes a temperature control circuit, and the triac ignition circuit 34 is entirely composed of a zero-cross 1-word generation LL circuit 64 and a transistor 56. In addition, the transistor 56 and
The transistor 67 and the capacitor 58 constitute a triac one-time firing circuit 35.

Therefore, when the power switch 40 is turned on to start the operation of the appliance, the output of the humidity control device 53 etc. causes the triac 45 to turn off/off once, one word is generated by the zero cross one word generating circuit 54, and the transistor 65 generates one word. The signal is amplified and added to the triac 45. When the triac 45 conducts, the current generates a voltage across the current node 46, which is rectified by the diode 47 and the resulting voltage charges the capacitor 48.
L.

This voltage is applied to the base of the transistor 50 through the resistor 49, turning off the transistor 60 and allowing current to flow through the relay coil 52, which closes the relay contact 44 and switches the current to the relay contact.Next, When the ignition signal is turned off, the triac leaf 5 is turned off, the transistor 50 is also turned off, the current in the relay coil 52 is stopped, and the relay contact 44 is opened. At the same time as the transistor 50 is turned off, the transistor 56 is turned off.
is also turned off, but at this time, the base current flows to the transistor 57 through the capacitor 58, and the transistor 57 is turned off.
Continue to fire 5. The time constant determined by the capacitor 58 and the base resistor is set to be longer than the off-operation time of the relay. Therefore, when the relay contact opens,
The triac 45 is on and can prevent arcing.

Therefore, even if the triac 45 and the relay are used for small currents, the lifespan will not be significantly shortened due to arcing, and large currents can be controlled.

As I learned, when there is no relay firing signal, if the triac accidentally fires due to the dV/dtl/C of the surge voltage, the triac will self-trigger, and as a result, the relay contact will follow. Since it closes, even if a surge voltage is continuously applied, current can be prevented from flowing continuously to the triac 45 for small current, and it can quickly switch to the relay contact side. be.

Therefore, it is possible to control the power of cooking appliances with high reliability, and since the triac prevents arcing during off-off, the relay can be a contact for small current. Further, since the operating time of the triac is short, it is sufficient to use a triac for small current.

Furthermore, even if the triac accidentally fires due to an external surge, the relay contact will follow and operate.
This completely prevents a large current from continuing to flow through the triac.

Effects of the Invention As described above, the present invention makes it possible to construct a highly reliable power control device at a low cost, and since only one intelligent drive word is required for the triac, the configuration of the ignition circuit can be reduced. It is possible to provide a power control device that is not only simple but also highly durable, with no elements being destroyed even by external surges.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a jar rice cooker using a conventional power control device, Fig. 2 is a block diagram showing a power control device according to an embodiment of the present invention, and Fig. 3 is a circuit diagram showing the power control device according to an embodiment of the present invention. It is a circuit diagram of the cooking device used. 30...Power semiconductor, 31,44...
Relay contact side 33...Relay coil drive circuit,
34...Ignition circuit, 35...Temporary ignition circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3

Claims (1)

[Claims] A power control means comprising a parallel circuit of a power semiconductor and a relay contact, an ignition device for the power semiconductor, a continuity detection circuit for the power semiconductor, and a relay coil drive circuit that operates with the output of the continuity detection device for the power semiconductor. A power control device comprising a temporary ignition circuit that operates when the operation of the relay coil drive circuit ends.