JPS63316202A - Temperature controller - Google Patents

Abstract

PURPOSE:To eliminate a danger that a load goes to an abnormal high temperature by interrupting energizing to the load with an interrupting circuit part, as a switch part is latched as it is turned on when the output of a switch part on/off detecting circuit part informs that the switch part is turned on. CONSTITUTION:When a relay RL1 outputs an off signal, and an output voltage V5 of a comparator 8 is kept to a low level, counts are counted, and when a value goes to the specified frequency, it is considered that the relay RL1 is welded and an on signal and an off signal are alternately supplied to the relay RL1 several times. Thereafter, the output voltage V5 of the comparator 8 is read into a microcomputer 9 again. When the voltage V5 is the low level, it is judged that the relay is completely welded and a relay RL2 is turned off. As such a result, the temperature of a load 2 cannot rise further.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a temperature control device for preventing abnormal heat generation of a load.

2. Description of the Related Art Conventionally, this type of temperature control device has often been configured to use a heater as a load and a relay to control energization to the load. However, in such a configuration, when the relay is welded, the temperature increases rapidly. Conventionally, when the temperature is detected to be above a certain temperature, it is determined that the relay is welded, and an on/off signal is given to the relay to try to remove the weld. If the relay is still welded, The heater was disconnected from the power supply using a temperature fuse, etc. to stop the temperature rise.

Problems to be Solved by the Invention However, in such a conventional configuration, when the relay is completely welded, the temperature rises until the temperature fuse blows out, so taking into account variations in the temperature fuse, etc., the heater can reach a considerably high temperature. This is potentially dangerous.

The present invention solves these problems by quickly detecting abnormalities in switch parts such as relays and preventing abnormal heat generation in the load.

Means for Solving the Problems The present invention solves the above problems by providing a power source, a load,
a switch section that controls energization to the load; a switch section drive circuit section that drives the switch section; a switch section on/off detection circuit section that detects whether the operation of the switch section is on or off; A switch part abnormality judgment part receives the outputs from the switch part drive circuit part and the switch part on/off detection circuit part to determine whether there is an abnormality in the switch part, and a switch part abnormality judgment part receives the output from the switch part abnormality judgment part and cuts off the power to the load. It consists of a cut-off circuit section.

According to the above-described configuration, the present invention detects whether the switch is on when the drive signal of the switch drive circuit is off and the output of the switch on/off detection circuit is information indicating that the switch is on. It is determined that the load is latched, and the cutoff circuit cuts off the power to the load.

Example An embodiment of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a circuit diagram of one embodiment. Figure 1.

In FIG. 2, 1 is a power source, 2 is a load, and consists of a heater. The switch section 3 consists of a relay It1.1, and the switch section drive circuit section 4 consists of a transistor Ql.
The switch section on/off detection circuit section 5 consists of a comparator 8 and its peripheral circuits, and the switch section abnormality judgment section 6 consists of a microcomputer 9 and a cutoff circuit section 7. consists of relays H1 and H2, a transistor 02, resistors R8 and R9, and a microcomputer 9. Base current now flows through the furnace resistor R9, turning on the transistor Q2. Therefore, relay RL
Current flows through coil No. 2, and relays R1 and R2 turn on.

Similarly, when the terminal voltage v2 of the switch drive circuit 4 becomes low level, the transistor Q1 turns on and the relay RL
I turns on. It is now assumed that the relay 11L2 of the cutoff circuit section 7 is on, and the following description will be made assuming that the relay flL2 is on. Relay R of switch section 3
When LI is turned on, power supply 1 is connected to load 2, and power is supplied to load 2. At this time, the terminal voltage v of load 2
3 is V3 = Vl. Further, when the terminal voltage v2 of the switch section drive circuit section 4 becomes high level, the transistor Ql is turned off and the relay 11LI is turned off. At this time, when the power supply voltage is υ, the voltage v3 is V3=υ−V
It becomes l. The switch section on/off detection circuit section 5 divides the voltage v3 using resistors R4 and R5 to reduce the input voltage v4 to the comparator 8. In addition, Dio-Tro 2 is a rectifying capacitor, and capacitor C2 is a smoothing capacitor.
When the relay RL1 is turned off, the terminal voltage v3 of the load 2 is rectified and smoothed, and converted into a DC voltage to obtain the input voltage v4 to the comparator 8. Therefore, when the contact of relay RLI is on, voltage 4 is small and relay RLI
When the contact is off, the voltage v4 is large. Resistance R
6.R7 divides the voltage Vl to obtain the reference voltage Vr.

Therefore, when the contact of relay RLI is turned on, V4<V
At r, the output voltage v5 of the comparator 8 becomes a low level, and when the contact of the relay RLI is turned off, V4>Vr, the output voltage v5 of the comparator 8 becomes a high level. That is,
The output voltage v5 of the comparator 8 allows detection of whether the contact of the relay RLI is on or off. Therefore, this voltage is input to the switch section abnormality determination section 6, and even though the voltage v2 of the switch section drive circuit section 4 is at a high level and the relay RLI is turned off, the output voltage v5 of the comparator 8 is at a low level. If so, it can be determined that the contacts of relay RLI are welded. If it is determined that welding has occurred, the terminal voltage v6 of the cutoff circuit section 7 is set to a high level, the relay RL2 is turned off, and the power supply to the load 2 is cut off. In addition,
Resistor R1 is a resistor for dropping the AC power supply voltage υ, diode 01 is for rectification, Z old is a Zener diode, CI
obtains the DC voltage Vl with a smoothing capacitor.

FIG. 3 shows a schematic flow of the operation of this circuit.

First, relay RL2 is turned on, and thereafter the amount of power supplied to the load is controlled by on/off control of relay 1'LI. After controlling relay RLI, a certain delay time is provided, and then the output voltage v of comparator 8 is
5 into the microcomputer 9. The reason why we set a certain delay time after controlling relay RLl is that since it takes time to charge and discharge capacitor C2, correct information cannot be obtained if the output voltage of comparator 8 is read immediately after controlling relay nL1. be. Here, if relay RLI
If v5 becomes low level while outputting an off signal to Perform a soft stick prevention routine. The soft stick countermeasure routine is a routine that alternately applies an on signal and an off signal to relay rlLl several times, and if it is a light weld, it can be removed by this routine. After the soft stick countermeasure routine, the output voltage v5 of the comparator 8 is read into the microcomputer 9 again, and if the output voltage v5 is low level, the relay 1? Judging that LI is completely welded, relay RL2 is turned off.

Like this, relay 1? When Ll is welded, the welding can be detected in a short time, and by turning off the relay 11L2, the temperature of the load can be prevented from rising any further. In addition,
Since the number of operations of relay nL2 is small and no discharge occurs between the contacts except when relay 111-1 is welded, there is no need to worry about welding.

Next, other embodiments of the present invention will be described. FIG. 4 is a circuit diagram of another embodiment. The difference in FIG. 4 from FIG. 2 is that a triac Tl is used instead of the relay rill. Therefore, when the terminal voltage v2 is at a high level and the output voltage v5 is at a low level, it is considered that the triac Tl is short-circuited, and in this case, the load 2 is disconnected from the power supply 1 by the relay nL2. Furthermore, when the triac Tl is overheated, v5 becomes high level while v2 is low level, so this can be detected and countermeasures such as sounding an alarm buzzer can be taken.

Effects of the Invention As described above, according to the present invention, an abnormality in the switch section can be detected in a short period of time, and in the event of an abnormality, a cutoff circuit prevents energization to the load, thereby reducing the risk of the load becoming abnormally high temperature. There is no. Additionally, if safety measures were taken using only the temperature fuse, the switch and temperature fuse would have to be replaced in the event of a failure, but with the present invention, only the switch needs to be replaced, and repairs can be done cheaply and quickly. be. Furthermore, the circuit configuration of the present invention is extremely useful as it can be applied not only to temperature control of loads but also to control of all kinds of loads such as motors.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a circuit diagram showing one embodiment, Fig. 3 is a flowchart showing the operation flow of one embodiment of the circuit, and Fig. 4 shows another embodiment. It is a circuit diagram. 1. Power supply, 2. Load, 3. Switch section, 4. Switch section drive circuit section, 5. Switch section on/off detection circuit section, 6. Switch section abnormality judgment section, 7.. Shutdown. Circuit section, 8... Comparator, 9... Microcomputer Name of agent Patent attorney Toshio Nakao and one other person Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A power supply, a load, a switch unit that controls the power supply to the load, a switch drive circuit unit that drives the switch unit, and a switch unit that detects whether the switch unit is on or off. a detection circuit unit, a switch unit abnormality determination unit that receives outputs from the switch unit drive circuit unit and the switch unit on/off detection circuit unit to determine whether the switch unit is abnormal; and a switch unit abnormality determination unit that receives the outputs of the switch unit abnormality determination unit A temperature control device comprising a cutoff circuit section that cuts off electricity to the temperature control device.