JP2014204635A - Cord short-circuit detection circuit, and outlet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cord short-circuit detection circuit capable of detecting occurrence of cord short-circuit on early stage by highly accurately detecting whisker cord short-circuit without reacting to an inrush current, and to provide an outlet device for breaking a circuit when cord short-circuit occurs.SOLUTION: A cord short-circuit detection circuit comprises: a rectifier circuit 11 for rectifying a voltage waveform of a circuit; a window comparator circuit 13 which compares specific two values which are less than a crest value of the voltage waveform, with an instantaneous value of an output voltage from the rectifier circuit 11, and, while the instantaneous value is situated within the specific two values, outputs a certain signal; a first comparator circuit 16 which determines occurrence of specific waveform distortion on the basis of output from the window comparator circuit; a second comparator circuit 18 which monitors reduction of a voltage crest value caused by an inrush current; and a second one-shot pulse circuit 19 which determines occurrence of cord short-circuit when the first comparator circuit 16 determines the occurrence of the specific distortion and the second comparator circuit 18 determines absence of the voltage reduction.

Description

  The present invention relates to a cord short-circuit detection circuit for detecting a cord short-circuit, and an outlet device having a function of interrupting an electric circuit when a cord short-circuit occurs.

It is known that this cord short circuit starts at first from a so-called beard cord short circuit in which an electric wire of about one stranded wire is short-circuited. Therefore, if the whisker cord short circuit can be detected with high accuracy, the initial stage of the cord short circuit can be detected, and it can be dealt with before the burnout of the electric wire or the fire occurs. Therefore, the present inventor has proposed a circuit capable of detecting a whisker code short circuit with high accuracy in Patent Document 1.
It has been confirmed from experiments that a current of several hundred amperes does not flow when a whisker cord is short-circuited, and the voltage waveform shows a unique shape as shown in FIG. A missing waveform is generated. Since this waveform is different from the waveforms of overcurrent and inrush current, this characteristic specific distorted voltage waveform is detected by setting two thresholds, and the initial stage of the cord short circuit can be detected.

JP 2012-186653 A

  The technique of Patent Document 1 has been able to detect a unique voltage waveform due to the occurrence of a beard code short circuit as shown in FIG. However, for example, the phenomenon that the voltage drops momentarily due to the so-called inrush current that occurs when a large number of lamps are turned on at one time cannot be completely eliminated, and it is mistakenly recognized as a specific voltage distortion caused by a beard code short circuit. In some cases, inrush current countermeasures were not sufficient.

  Therefore, in view of such a problem, the present invention detects a whisker cord short-circuit with high accuracy without reacting to an inrush current, a cord short-circuit detection circuit capable of early detection of a cord short-circuit occurrence, and an electric circuit when a cord short-circuit occurs. The object is to provide an outlet device that shuts off.

In order to solve the above problems, a cord short-circuit detection circuit according to the first aspect of the present invention detects a specific waveform distortion caused by a rectifier circuit that rectifies a voltage waveform of an electric circuit that supplies commercial power to a load, and a whisker cord short-circuit occurrence. Therefore, a window comparator circuit that compares a specific binary value lower than the peak value of the commercial voltage waveform with an instantaneous value of the rectifier circuit output voltage and outputs a constant signal while the instantaneous value is between the specific binary values A specific distortion determination circuit that determines the occurrence of a specific waveform distortion based on the output of the window comparator circuit, a voltage monitoring circuit that monitors a decrease in the peak value of the voltage waveform output from the rectifier circuit, and a specific distortion determination circuit And a determination circuit that determines that a cord short-circuit has occurred when it is determined that specific distortion has occurred and the voltage monitoring circuit determines that there is no voltage drop.
According to this configuration, even if the specific distortion determination circuit determines that a specific distortion has occurred due to the occurrence of a mustache cord short circuit, the voltage monitoring circuit does not determine the occurrence of a cord short circuit if it detects a decrease in the circuit voltage due to the inrush current. The occurrence of the cord short circuit can be detected early and with high accuracy by eliminating the decrease.

According to a second aspect of the present invention, there is provided an outlet device in which a load is connected, an electric circuit for supplying commercial power to the electric outlet, an opening / closing means provided on the electric circuit for opening and closing the electric circuit, and an opening / closing means. It is characterized by having a shut-off means to be operated, a cord short-circuit detecting circuit according to claim 1, and an output circuit for driving the shut-off means based on a cord short-circuit occurrence signal output from the cord short-circuit detecting circuit.
According to this configuration, since the occurrence of the cord short circuit is detected early and the outlet output is stopped, it is possible to reliably prevent the occurrence of a fire due to the cord short circuit.

According to the cord short circuit detection circuit according to the present invention, even if the specific distortion determination circuit determines that the specific distortion occurs due to the beard code short circuit occurrence, if the voltage monitoring circuit detects a decrease in the circuit voltage due to the inrush current, the code short circuit detection is not determined. Therefore, the voltage drop due to the inrush current is eliminated, and the occurrence of the cord short circuit can be detected early and with high accuracy.
Further, according to the outlet device of the present invention, since the occurrence of the cord short circuit is detected at an early stage and the outlet output is stopped, it is possible to reliably prevent the occurrence of a fire due to the cord short circuit.

It is a circuit diagram which shows an example of the outlet apparatus which concerns on this invention. 2 is a waveform diagram of a main part of the cord short-circuit detection circuit of FIG. 1, (a) is an output waveform of a rectifier circuit, (b) is a window comparator circuit output waveform, (c) is an integration circuit output waveform, and (d) is a first waveform. The output of the comparison circuit is shown. The waveform of each part at the time of rush current generation | occurrence | production is shown, (a) is an outlet output voltage waveform, (b) is a rectifier circuit output voltage waveform, (c) is a 2nd comparison circuit output waveform. The waveform of each part in normal times is shown, (a) is an outlet output voltage waveform, (b) is a rectifier circuit output voltage waveform, and (c) is a second comparison circuit output waveform. It is explanatory drawing of the circuit voltage waveform at the time of a beard code short circuit occurrence.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an example of an outlet device according to the present invention, in which 1 is an outlet device, 2 is a commercial power source supplied from a distribution board, etc., 3 is a load such as a television or lighting, and 4 is a load 3. An outlet to be connected, L1 is an electric circuit from the commercial power source 2 to the outlet device 1, and L2 is a load electric circuit from a plug (not shown) connected to the outlet 4 to the load 3. Note that the outlet device 1 is normally installed in a wall surface.

  As shown in FIG. 1, the outlet device 1 includes an open / close contact 6 provided on an internal electric circuit L <b> 3 extending from the power supply connection portion connecting the electric circuit L <b> 1 to which the commercial power supply 2 is connected to the outlet 4, and a plunger for opening the open / close contact 6. An electromagnetic coil 7 provided with 7a, an output circuit 8 for driving the electromagnetic coil 7, and a cord short-circuit detecting circuit 10 for detecting a cord short-circuit are provided.

  The cord short-circuit detection circuit 10 is a rectifier circuit 11 that performs full-wave rectification of the circuit voltage of the internal circuit L3, a power supply circuit 12 that supplies power to each part of the cord short-circuit detection circuit 10, The window comparator circuit 13 for comparing with the value, the waveform shaping circuit 14 for shaping the output waveform of the window comparator circuit 13, the integrating circuit 15 for integrating the output waveform of the waveform shaping circuit 14, and the output of the integrating circuit 15 are compared with a predetermined threshold value. The first comparison circuit 16 as a specific distortion determination circuit that determines the occurrence of specific distortion, the first one-shot pulse circuit 17 that receives the output of the first comparison circuit 16 and outputs a pulse signal, and the voltage rectified by the rectifier circuit 11 Second comparison circuit 18 serving as a voltage monitoring circuit for comparing the waveform with a specific threshold, the output of second comparison circuit 18 and the first one-shot pulse circuit 7 outputs a to determine the Higekodo short circuit based and a second one-shot pulse circuit 19 or the like as a determination circuit for outputting a pulse signal.

The operation of the cord short circuit detection circuit 10 configured as described above is as follows. This will be described with reference to the waveform explanatory diagrams of FIGS. The window comparator circuit 13 has a specific binary value (a higher first fixed value EH and a lower second fixed value EL) that is lower than a peak value of a preset circuit voltage waveform (commercial voltage waveform). The voltage waveform output from the rectifier circuit 11 is compared, and a specific signal is output while there is an instantaneous value of the circuit voltage between the two fixed values.
Specifically, the electric circuit voltage is divided and inputted to the window comparator circuit 13, and for example, a voltage divided by 1/10 is inputted. As a result, a voltage having a peak value of about 14 volts is input. For this value of voltage, for example, the first fixed value EH = 5 volts and the second fixed value EL = 1 volt are set. With this setting, it is possible to detect a unique change in the circuit voltage caused by the beard cord short circuit shown in FIG.

Here, FIG. 2 shows the waveform of the main part of the cord short circuit detection circuit 10, FIG. 2A shows the relationship between the voltage waveform V inputted to the window comparator circuit 13 and specific binary values EH and EL, and FIG. 2B shows the output of the waveform shaping circuit 14, FIG. 2C shows the output of the integrating circuit 15, and FIG. 2D shows the output waveform of the first comparison circuit 16.
As shown in FIG. 2A, specific binary values EH and EL are set so as to sandwich a unique change in the circuit voltage caused by a beard code short circuit. As shown in FIG. 2B, the waveform shaping circuit 14 outputs a rectangular wave with a time width T1 when normal, but outputs a rectangular wave with a long time width T2 when a whisker code short circuit occurs. When a whisker code short circuit occurs, a characteristic voltage waveform is generated. Therefore, it can be seen that a state in which the instantaneous value stays for several ms is from about several tens of volts to about 70 volts, which is about 50% of the peak value. Therefore, by setting the first fixed value EH and the second fixed value EL as described above, the state can be detected, and a mustache code short circuit can be detected.

  The integrating circuit 15 integrates the rectangular wave output from the waveform shaping circuit 14 and outputs a signal M having a waveform as shown in FIG. As shown in FIG. 2 (c), a waveform M1 having a small peak value is output for a normal sine wave, but a waveform of T2 generated by a cord short circuit (whisker code short circuit) is received and indicated by M2. A waveform having a large peak value is output.

  The first comparison circuit 16 compares the output of the integration circuit 15 with a predetermined threshold Th and outputs a signal N as shown in FIG. Thus, in the case of a normal sine wave, there is no output, and a signal N is output when distortion as shown in S of FIG. 5 occurs. The first one-shot pulse circuit 17 receives the output N of the first comparison circuit 16 and outputs a pulse signal.

On the other hand, the second comparison circuit 18 compares the rectified electric circuit voltage waveform with a predetermined threshold value, and does not generate an output unless the instantaneous value of the electric circuit voltage reaches a predetermined value. 3 and 4 specifically show the output of the second comparison circuit 18, and FIG. 3 shows a normal state where the circuit voltage is normal when the circuit voltage is greatly reduced due to the occurrence of an excessive inrush current. Vth represents a predetermined threshold value. As shown in FIGS. 3 and 4, the second comparison circuit 18 always outputs a rectangular wave in accordance with the voltage peak in the normal state, but when an inrush current occurs, the output is temporarily output as shown in FIG. Will be lost.
The second one-shot pulse circuit 19 receives the output signals of the second comparison circuit 18 and the first one-shot pulse circuit 17, and when both output a rectangular wave, that is, when the [H] signal is output, the output circuit 8 Outputs a pulse signal that activates.

  The output circuit 8 is turned on in response to this signal, and drives the electromagnetic coil 7 so that the plunger 7a is pulled out. As a result, the open / close contact 6 is opened and the supply of power to the load 3 is stopped.

Thus, even if the first comparison circuit 16 determines that the specific distortion has occurred, if the second comparison circuit 18 detects a decrease in the circuit voltage due to the inrush current, it does not determine that a cord short-circuit has occurred. The occurrence of the cord short circuit can be detected with high accuracy. And since a shading cord short circuit is detected and the interruption | blocking operation | movement is carried out, a code short circuit can be detected at an early stage.
Also, if a cord short-circuit occurs, it is detected and the electrical circuit is shut off to stop the outlet output, so that a fire due to a cord short-circuit can be reliably prevented.

In addition, although the said embodiment demonstrated the case where the cord short circuit detection circuit 10 was integrated in an outlet, it may be incorporated in circuit breakers, such as a branch breaker, or it is incorporated in the tap outlet used by connecting to an outlet. You may let them.
Moreover, although the interruption | blocking function is provided in the outlet apparatus, it is good also as a structure which notifies by sound or light emission of LED, when a cord short circuit generate | occur | produces.

  1 .... Outlet device, 4 .... Outlet, 6 .... Open / close contact (open / close means), 7 .... Electromagnetic coil (breaking means), 8 .... Output circuit, 10 .... Cord short circuit detection circuit, 11 .... Rectifier circuit , 13 .. Window comparator circuit, 16... First comparison circuit (specific distortion detection circuit), 18... Second comparison circuit (voltage monitoring circuit), 19 .. Second one-shot pulse circuit (determination circuit), L 3 ..Internal circuit (electric circuit).

Claims (2)

A rectifier circuit that rectifies the voltage waveform of the electric circuit that supplies commercial power to the load;
In order to detect a specific waveform distortion due to the occurrence of a whisker code short circuit, a specific binary value lower than a peak value of a commercial voltage waveform is compared with an instantaneous value of the rectifier circuit output voltage, and the instantaneous value is between the specific binary values. A window comparator circuit that outputs a constant signal while
A specific distortion determination circuit that determines the occurrence of the specific waveform distortion based on an output of the window comparator circuit;
A voltage monitoring circuit for monitoring a drop in the peak value of the voltage waveform output by the rectifier circuit;
A cord short circuit detection circuit comprising: a determination circuit that determines that a cord short circuit has occurred when the specific distortion determination circuit determines that a specific distortion has occurred and the voltage monitoring circuit determines that there is no voltage drop. An outlet to which a load is connected, an electric circuit for supplying commercial power to the outlet, an opening / closing means provided on the electric circuit for opening and closing the electric circuit, and a blocking means for opening the opening / closing means. An outlet device comprising: the cord short-circuit detection circuit according to claim 1; and an output circuit that drives the blocking means based on a cord short-circuit occurrence signal output from the cord short-circuit detection circuit.

Images