JPH02876Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to an electric carpet having an earth leakage detection function.

[Background technology]

The earth leakage detection device is configured to detect a current leakage in an electric appliance, cut off the current supply path to the electric appliance, and maintain the cut-off state until it is reset.
Such a function is essential for safety in earth leakage circuit breakers etc. built into indoor wiring, etc., but when installing earth leakage detection devices in individual electrical appliances, for example, it is necessary for electric carpets to prevent electric shocks. When a leakage detection device is installed, it is necessary to set its sensitivity to about several mA to 10 mA and the cutoff speed to about 2 to 3 cycles for safety reasons. However, such high-sensitivity and high-speed settings tend to cause malfunctions due to leakage current from the electric carpet to the ground and external noise, making it impossible to fully perform the heating function originally required of the electric carpet.

[Purpose of invention]

Therefore, the object of this invention is to provide an electric carpet that can fully utilize its heating function even if it malfunctions due to external noise or the like.

[Disclosure of invention]

The electric carpet of this invention includes a self-holding current leakage detection circuit that detects current leakage in the electric carpet body with high sensitivity and quickly cuts off the current flow path to the electric carpet body, and a current flow path to the electric carpet body. The present invention is characterized in that it is configured to include a timer circuit that releases the self-holding of the earth leakage detection circuit after a predetermined period of time has elapsed after the earth leakage detection circuit is shut off.

An embodiment of this invention will be described based on the drawings. This electric carpet includes a self-holding current leakage detection circuit 2 that detects a current leakage in the electric carpet body (not shown) and cuts off the current flow path to the electric carpet body, and a current leakage detection circuit 2 that blocks the current flow path to the electric carpet body. It is provided with a timer circuit 3 that releases the self-holding state of the earth leakage detection circuit 2 after a certain period of time (about 3 to 15 minutes) has passed after the circuit is cut off.

This electric carpet will be explained in detail below. This electric carpet detects the level of a temperature detection signal applied from a terminal 1a of the temperature control device 1 by a switching circuit 1b having hysteresis. When the temperature of the electric carpet body becomes lower than a predetermined value and a high-level signal is input, this switching circuit 1b generates a high-level output and turns on the transistor 1c, thereby supplying power to the relay 1d to generate electricity. A heater (not shown) in the carpet body is energized; on the other hand, when the temperature of the electric carpet body becomes higher than a predetermined value and a low level signal is input, a low level output is generated and the transistor 1c is turned off; Thereby, the power supply to the relay 1d is stopped and the power supply to the heater is stopped, and by repeating this operation, the temperature of the electric carpet body is controlled to be constant.

The earth leakage detection circuit 2 is a secondary coil 2 of a zero-phase current transformer obtained by detecting earth leakage in the electric carpet main body.
The output of a is amplified by an amplifier 2b, and this amplifier 2b
When the output of thyristor 2c exceeds a certain voltage,
is triggered to conduct, thereby making the output of the switching circuit 1b always at a low level, that is, dropping the base potential of the transistor 1c to the ground potential (emitter potential), regardless of the high or low input level of the switching circuit 1b. is turned off, the power supply to the relay 1d is cut off, and the power supply to the heater of the electric carpet body is cut off. In this case, the leakage detection sensitivity and cutoff speed are determined by the capacitor 2d and the resistor 2e.

In the timer circuit 3, when the output of the switching circuit 1b is at a high level, the counter 3a and the flip-flop 3b are reset, and the output of the flip-flop 3b becomes low level and the transistor 3 is reset.
c is turned off. However, when the earth leakage detection circuit 2 detects an earth leakage and sets the output of the switching circuit 1b to a low level, the counter 3a starts counting, and when the counter 3a counts a certain number, that is, after a certain period of time has elapsed, the flip-flop 3b The output of transistor 3 is set to high level, and
c is turned on, the gate and cathode of thyristor 2c are short-circuited, and thyristor 2c is cut off. As a result, the temperature control device 1 resumes normal operation. At the same time, a high level signal is also applied from the flip-flop 3b to the switching circuit 1b via the diode 3d, the output of the switching circuit 1b becomes high level, the counter 3a and the flip-flop 3b are reset, and the output of the flip-flop 3b becomes low level. and transistor 3c
is turned off. Note that if the leakage state continues even after the thyristor 2c is cut off by the operation of the timer circuit 3, the above-described operation is repeated again.

Thus, the electric carpet of this example is
Since the earth leakage detection circuit 2 with high sensitivity detection and high-speed shutoff type is activated and is configured to automatically reset the earth leakage detection circuit 2 by the timer circuit 3 after a certain period of time has elapsed, the electric It is possible to reliably prevent instantaneous electric shock accidents caused by the flow of current, and by making the earth leakage detection circuit 2 a highly sensitive and fast cut-off type, it is possible to prevent transient noise or Even if the earth leakage detection circuit 2 tends to malfunction due to direct leakage current from the electric carpet body to the ground, the earth leakage detection circuit 2 is automatically reset by the timer circuit 3, so that power cannot be supplied to the electric carpet body. is automatically restarted, allowing the heating function to be fully utilized. In addition, because electric shock accidents are temporary and will not continue,
Even if the earth leakage detection circuit 2 is automatically reset, safety will not be compromised.

[Effect of idea]

As mentioned above, the electric carpet of this invention is
A self-holding current leakage detection circuit that detects current leakage in an electric carpet body with high sensitivity and quickly cuts off a current path to the electric carpet body; Since it is equipped with a timer circuit that releases the self-holding of the earth leakage detection circuit, it is possible to reliably prevent instantaneous electric shock accidents caused by current flowing from the electric carpet body through the human body to the earth. By making the circuit highly sensitive and fast-cutting, the earth leakage detection circuit is more likely to malfunction due to transient noise coming from the electric carpet body or power line, or direct leakage current from the electric carpet body to the ground. However, since the earth leakage detection circuit is automatically reset by the timer circuit, power supply to the electric carpet body is automatically restarted, and the heating function can be fully utilized.
Furthermore, since electric shock accidents are temporary and will not continue, safety will not be compromised even if the earth leakage detection circuit is automatically reset.

[Brief explanation of drawings]

The drawing is a circuit diagram of an embodiment of this invention. 1...Temperature control device, 2...Earth leakage detection circuit, 3
...Timer circuit.

Claims (1)

[Scope of utility model registration request] A self-holding current leakage detection circuit that detects current leakage in an electric carpet body with high sensitivity and quickly cuts off a current path to the electric carpet body; and a timer circuit for releasing the self-holding of the earth leakage detection circuit.