JPH0554969B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for a cooking appliance such as an electric cooking heater.

Conventional Technology In recent years, cooking devices such as electric shoe heaters use temperature sensors that touch the bottom of the pot to monitor the temperature of the pot to prevent the pot from drying out or igniting even if heated for a long time with oil etc. Products with a function to prevent pots from overheating have begun to be made, detecting the temperature of the pot and shutting off the electricity at a certain temperature.

An example of a control circuit for such a conventional cooking appliance is shown in FIG. In FIG. 3, reference numeral 1 denotes a temperature sensor provided in contact with the bottom of the pot, which is connected to a temperature detection circuit 2, and the pot temperature signal detected by the temperature detection circuit 2 is sent to a microcomputer 3. It is being output. The microcomputer 3 is the first,
It has a program that determines how to energize the second heaters 4 and 5 according to the cooking method, and a drive circuit 6 is supplied from the output terminal P ₂ according to the pot temperature signal.
The first power control element 7 is driven through the output terminal P1 to control the energization to the first heater 4, and the second power control element 8 is driven from the output terminal _P1 through the drive circuit 6 to control the second power supply. When the pot temperature signal detects a temperature above a certain level, the drive of the first and second power control elements 7 and 8 is stopped. The power supply to the heaters 4 and 5 is stopped. Reference numeral 9 is a power switch, 10 is a power supply circuit, and 11 is an input circuit that instructs to start cooking and the like.

Problems to be Solved by the Invention However, in such a conventional electric cooker, if the power control elements 7 and 8 fail in a short state, the microcomputer 3
Even if the drive of the power control elements 7 and 8 is stopped, the power control elements 7 and 8 cannot be turned off and are continuously energized. This created a dangerous situation that could cause a fire.

The present invention solves the above-mentioned problems, and aims to provide a control device for a cooking appliance that can detect a failure in the short state of a power control element and prevent continuous energization of the heater. be.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides first and second power control elements connected to both ends of a heater, and a combination of the first power control element and the heater. an energization detection circuit connected to the connection point and detecting the energization state of the first and second power control elements;
A microcomputer is provided that controls energization to the heater by driving a second power control element, and the microcomputer is configured to control the energization detection circuit in a state in which neither the first nor second power control element is driven. Check the signal, then drive at least one of the first and second power control elements, check the signal of the energization detection circuit again, and when both are normal, normally energize the heater. It is configured to execute control operations.

Effect With the above configuration, before performing normal energization control operation, the microcomputer checks the signal of the energization detection circuit and confirms that the first and second power control elements operate normally. Starts energization control operation. If the first or second power control element is out of order, the energization control operation is not started.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings. The same circuits and parts as those in FIG. 3 showing the conventional example are given the same reference numerals and their explanations will be omitted.

FIG. 1 shows a control device for a cooking appliance according to the present invention. In FIG. 1, a relay 13 as a first power control element and a thyristor 14 as a second power control element are provided at both ends of a heater 12. An energization detection circuit 15 is installed at the connection point between the heater 12 and the relay 13.
is connected, and the output of this energization detection circuit 15 is connected to an input terminal _P3 of a microcomputer 16, which will be described later. The energization detection circuit 15 is composed of a transistor 17, and if both the relay 13 and the thyristor 14 are normal, and the relay 13 and the thyristor 14 are both off, the transistor 17 is turned off and the output of the energization detection circuit 15 is When the level is low (mode A) and only the thyristor 14 is on, the transistor 17 is driven according to the frequency of the power supply, the output of the energization detection circuit 15 becomes a pulse signal (mode B), and the relay 13 and thyristor 14 are turned on. When both are on, the transistor 17 is turned off and the output of the energization detection circuit 15 is configured to be at a low level. 18 is a power supply circuit.

The microcomputer 16 drives the relay 13 from the output terminal P ₂ via the first drive circuit 19 and drives the thyristor 14 from the output terminal P ₁ via the second drive circuit 20 depending on the pot temperature. Like the conventional microcomputer 3, the heater 12
In addition to controlling the energization of the heater 12, the microcomputer 3 performs a confirmation operation as shown in FIG. 2, which is not present in the conventional microcomputer 3, before starting the normal energization control operation of the heater 12 after the reset is released. FIG. 2 is a flowchart of a confirmation routine that is provided after the reset is released and before the normal energization control of the heater 12 starts. After the start, in the first step,
The output terminals P ₁ and P ₂ of the microcomputer 16 are set to high level, and the relay 13 and thyristor 14 are set to the off state. Next, in the second step, the presence or absence of a signal at the input terminal _P3 to which the output of the energization detection circuit 15 is connected is checked, and if the input terminal _P3 is at a low level in mode A, the relay 13 and thyristor 14
is judged to be in a normal off state, and the process moves to the third step. If a pulse signal is detected at the input terminal _P3 , it is determined that the thyristor 14 is firing, and the process branches to the sixth step, which will be described later. In the third step, the output terminal _P1 is set to a low level and the thyristor 14 is turned on. In the fourth step, the signal at input terminal _P3 is checked again, and if a pulse signal is detected in the state of mode B, it is determined to be normal, and the process moves to the next fifth step, where input terminal _P1 is set to a high level. Then, the thyristor 14 is turned off and the normal energization control operation of the heater 12 is started. If no pulse signal is detected at the input terminal _P3 , it is determined that either the thyristor 14 is in the OFF state or the relay 13 is in the SHOOT state, and the process branches to the sixth step. In the sixth step, the operation is stopped and an abnormality is displayed.

In this way, the failure of the relay 13 and thyristor 14 is detected in advance before the normal energization control operation of the heater 12 is performed.
Therefore, the relay 13 and thyristor 14 cannot be turned off, and as a result, continuous energization is avoided, and a dangerous situation such as oil catching fire due to overheating of the pot is prevented.

Note that the confirmation routine of this embodiment is designed to operate after the reset is released and before the normal energization control operation of the heater 12 starts, but it is possible to interrupt the normal operation and repeat the above confirmation routine at regular intervals. You may go. Further, in this embodiment, the energization detection circuit 15 is connected to the connection point between the relay 13 and the heater 12, but the thyristor 14 and the heater 1
The energization detection circuit 15 may be connected to the second connection point. However, in this case, the relay 13 is driven instead of the thyristor 14 in the above confirmation routine.

Effects of the Invention As described above, according to the present invention, the signal of the energization detection circuit is checked by a microcomputer and the first and second
After confirming that none of the power control elements is malfunctioning, the normal energization control operation for the heater is performed, so if one of the power control elements fails in short state, the energization control described above is executed. To provide a safe cooking device in which the operation of the heater does not start, the heater is prevented from being continuously energized by the shorting of the power control element, and dangers such as oil ignition due to overheating are prevented. can.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a control device for a cooking appliance showing an embodiment of the present invention, Fig. 2 is a flowchart of the control device for the cooking appliance, and Fig. 3 is a circuit diagram of a conventional control device for a cooking appliance. be. 12... Heater, 13... Relay (first power control element), 14... Thyristor (second power control element), 15... Energization detection circuit, 16... Microcomputer.

Claims (1)

[Claims] 1 first and second power control elements connected to both ends of the heater, and a power control element connected to a connection point between the first power control element and the heater to control the energization state of the first and second power control elements. A energization detection circuit for detecting the current, and a microcomputer for driving the first and second power control elements to control energization to the heater, and the microcomputer is connected to the first and second power control elements. Check the signal of the energization detection circuit in a state in which neither of the first and second power control elements is driven, and then check the signal of the energization detection circuit again after driving at least one of the first and second power control elements, and determine that both are normal. A control device for a cooking appliance configured to perform a normal energization control operation to the heater when the heater is hot.