JPH0527824Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a safety device for power controllers such as triacs, SCRs, and relays.

[Prior Art] Conventionally, there are detection circuits that detect short circuits and disconnections in controllers such as triacs, SCRs, and relays, and disconnections in heaters.

As an example, as shown in Fig. 2, controller 1 and controller 2, such as triacs or SCRs, are configured in circuits such that when they are ON, they are OFF, and when they are OFF, they are ON, and the circuits are opposite to each other. There is.

Therefore, normally no current flows through the resistor 3 and the circuit operates normally. Instructions to controller 1
If controller 1 turns on even though it is off,
Since the controller 2 is also turned on, current flows through the resistor 3, causing it to overheat and blow out the temperature fuse 4.

Therefore, no current flows through the heater 5. As conventional example 2, in the safety device of the power controller shown in Fig. 3, when the SCR 7 conducts reversely, current flows through the resistor 3 and the diode 9, and this resistor 3 overheats, blowing out the temperature fuse 4. , heater 5
Power is cut off.

As a conventional example 3, in the safety device of the power controller shown in FIG. 4, since the heaters 5a and 5b are normally normal, the capacitor 12 is charged when the transistor 11 is turned on. Therefore, when transistor 13 is turned on, relay 15 is turned on.

When the heater 5a is disconnected, the base current does not flow to the transistor 11, so the transistor 11
By turning off, the transistor 13 is also turned off, the relay contact 16 is also turned off, and the main circuit heaters 5a,
Current no longer flows through 5b.

As conventional example 4, in the safety device of the current controller shown in FIG. 5, when the output of the temperature regulator 20 is H, the thyristor is turned on and current flows through the main circuit.
Therefore, since no gate current flows to the thyristor 21, the thyristor 21 is turned off. Next, when the temperature controller output is L, the transistor 11 is turned on, so no gate current flows through the thyristor 21, and the thyristor 21 is turned off.

Here, even though the output of the temperature regulator 20 is H, when the thyristor 7 is turned off, the transistor 11 is turned off, so a gate current flows to the thyristor 21, turning on the thyristor 21, and the resistor 3
heats up, the temperature fuse 4 blows, and the heater 5 is turned on.
Turn off.

[Problem to be solved by the invention] In the safety devices of these power controllers, the heater 5
When detecting a disconnection in the controller 1 or the thyristor 7, a short circuit, or a disconnection in the controller 1 or the thyristor 7, it is necessary to provide separate detection circuits for each, which has the disadvantage of complicating the circuit.

In addition, in the short circuit or disconnection detection circuit, if one of the circuits connected to one power line from the contact point between the heater 5 and the controller 1 or thyristor 7 is disconnected, the safety device will fail and the line circuit will operate normally. . Therefore, if the controller 1 or the thyristor 7 were to fail due to a short circuit, the safety device would not operate and there was a risk of a serious accident. Especially heater 5
Both the controller 1 or the thyristor 7, etc., generate heat, and the lead wire drawn out from the contact point between the heater 5 and the controller 1, the thyristor 7, etc. is naturally affected by the heat, and is susceptible to thermal deterioration. The lead wires were easily broken. Therefore, failure of the safety device is likely to occur, which poses a problem.

Therefore, an object of the present invention is to provide a safety device for a power controller that has a simple circuit and improves reliability by turning off the main circuit even in the event of a failure of the safety device.

[Means for solving the problem] It has a main circuit in which a heater and a controller are connected in series to the power line, and a detector that detects ON/OFF of the controller from the voltage across the controller, and It has an EX-OR logic circuit that inputs the detector signal,
It has a temperature controller that inputs a signal to the EX-OR logic circuit, a controller connected to the output side of the EX-OR logic circuit, and a configuration in which the power supply circuit is turned off when the controller is turned on. A safety device for a power controller featuring:

[Embodiment] FIG. 1 shows an embodiment of a safety device for a power controller according to the present invention.

The illustrated safety device for the power controller has a main circuit in which a heater 31 and a controller 32 such as a triac or SCR are connected in series between power lines. A voltage detector 35 is connected to both ends of the controller 32 . The output side of the voltage detector 35 is connected to the EX-OR logic circuit 3 via the switching element 37.
9 is connected to one input end.

One output terminal of the temperature controller 41 is connected to the other input terminal of this EX-OR logic circuit 39. The temperature regulator 41 is connected to a DC power source 43 connected between power lines.

Further, the controller 32 is connected to a connection line between the temperature regulator 41 and the EX-OR logic circuit 39 via a signal circuit 45.

On the other hand, on the output side of the EX-OR logic circuit 39,
A controller 51 is connected via a signal circuit 49. The controller 51 has a resistor 53 connected in series, and the series end thereof is connected to a power supply line.

A current detecting means, that is, a current transformer 58 is connected to the connection line between one power supply line and the resistor 53.
is provided. Current transformer 58 is connected to current detector 60. The current detector 60 is connected to the power line and serves to turn off the power based on the current detected by the current transformer 58.

The voltage across the controller 32 is detected by the voltage detector 35, and this signal is input to the EX-OR logic circuit 39. The EX-OR logic circuit 39 constantly monitors whether the controller 32 is being controlled according to the instructions from the output of the temperature regulator 41 based on its input.

At this time, if the output of the temperature controller is controlled differently due to a disconnection of the heater 31 or a short circuit or disconnection of the controller 32, or if the safety device malfunctions due to a disconnection of the voltage detector 35, etc., the EX-OR logic circuit 3
9 detects this and turns on the controller 51.

This current is detected by a current transformer 58, and a current detector 60 turns off the power.

Furthermore, in a circuit that controls a plurality of heaters 31 using a plurality of controllers 32, when a sensor is attached to one heater 31 to control the heater 31, if the heater 31 to which the sensor is attached breaks, Since the temperature of that heater 31 does not rise, the other heaters 31 will become abnormally overheated.

In such a case, by periodically and forcibly turning off the output of the temperature regulator 41 (main circuit), disconnection of the heater 31 is detected and the main circuit is turned off.

In addition, in the case of O-volt switch ON-OFF control or in the case of a relay, etc., a time delay occurs until the controller 32 operates after the instruction from the temperature regulator 41.

In this case, it is necessary to lock the output of the temperature regulator 41 after the instruction, confirm that the operation is normal at a certain moment after the controller 32 operates, and transmit the signal at that time to the controller 51.

[Effects of the invention] As explained above using the embodiments, according to the safety device of the power controller of the invention, the output of the temperature controller and the operation result of the controller can be input to the EX-OR logic circuit. This makes it possible to check for disconnection of heaters, short circuits, and disconnection failures of controllers, etc., with a single safety device.

In addition, safety devices that check for disconnections in heaters, short circuits in controllers, and disconnections have traditionally had to be connected directly to the contacts of heaters, controllers, etc., so safety devices are susceptible to thermal effects from heaters and have a long lifespan. However, in the present invention, the safety device operates even in the event of a breakage of the lead wire.

Furthermore, a voltage detector detects the operation of the controller in the signal circuit up to the EX-OR input.
Even if a failure occurs and the EX-OR input is always L or always H, the safety device operates to ensure safety.

That is, the safety device of the present invention not only detects a heater disconnection or a short circuit or disconnection of a controller, but also detects a failure of the safety device itself to ensure safety.

Furthermore, by comparing and monitoring the temperature controller output and the power control results, a safety device is activated even in the event of a component failure on the way from the temperature controller output to the controller input, making it extremely reliable. It can be said to be a highly reliable safety device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a safety device for a power controller according to the present invention, and FIGS. 2 to 5 are circuit diagrams of safety circuits for a conventional power controller. 31... Heater, 32... Controller, 35... Voltage detector, 39... EX-OR logic circuit, 41...
...Temperature regulator, 51...Controller, 58...Current transformer, 60...Current detector.

Claims (1)

[Scope of utility model registration request] It has a main circuit in which a heater and a controller are connected in series to the power line, and a detector that detects ON-OFF of the controller from the voltage across the controller, and an EX-OR that inputs the signal of the detector. has a logic circuit,
It has a temperature controller that inputs a signal to the EX-OR logic circuit, a controller connected to the output side of the EX-OR logic circuit, and a configuration in which the power supply circuit is turned off when the controller is turned on. A safety device for a power controller featuring: