JP2015089228A - Cord short circuit detection circuit and outlet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cord short circuit detection circuit which can highly accurately detect whisker cord short circuit and does not cause malfunction by inrush current.SOLUTION: A cord short circuit detection circuit has: a specific distortion detection circuit 14 which detects specific waveform distortion from a rectified electric path voltage waveform; an inrush voltage detection circuit 15 which detects a voltage change by inrush current of load from a rectification waveform; and a determination circuit 16 which determines an occurrence of cord short circuit. The specific distortion detection circuit 14 is provided with: a window comparator circuit 20 which detects a state that a rectified voltage waveform is between 2 prescribed thresholds; an average value circuit 19 for generating 2 thresholds from output of a rectifying circuit 13; and a first comparison circuit 23 which determines that waveform distortion has occurred when a time when the waveform is between the 2 thresholds is longer than a prescribed time. The inrush voltage detection circuit 15 detects a state that a peak value of electric path voltage is below a prescribed voltage. The determination circuit 16 outputs a cord short circuit generation signal on the basis of outputs of the specific distortion detection circuit 14 and the inrush voltage detection circuit 15.

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.

2. Description of the Related Art Conventionally, there is an outlet device that has a function of detecting an occurrence of a short-circuiting of a cord on an electric path from a plug inserted into an outlet to a load and interrupting the electric circuit.
It is known that this cord short circuit starts from a so-called whisker cord short circuit in which a wire of about one stranded wire is first short-circuited. At this time, it is confirmed by experiment that the voltage waveform of the electric circuit shows a unique shape. Has been. FIG. 6 shows a voltage waveform when the whisker code short-circuit occurs, and a waveform that is largely cut out from the vicinity of the peak as indicated by S is generated.
The present inventor proposed in Patent Document 1 an outlet device that detects the occurrence of a cord short circuit by detecting the characteristics of the voltage waveform and interrupts the electric circuit.

JP 2012-186653 A

  However, the circuit configuration of Patent Document 1 has the following problems. First, the voltage waveform rectified in the rectifier circuit did not drop to the zero point (0 volt), and the next half cycle started (shown in FIG. 2A). For this reason, the setting of “specific binary” for detecting a mustache code short circuit is limited, and it is difficult to accurately detect a beard code short circuit. However, this is caused by a capacitor provided in the power supply circuit, and it is impossible to omit this because the power supply becomes unstable and affects other circuits.

In addition, when the inrush current generated when the load device is turned on is extremely large, the electric circuit voltage is greatly reduced, and this voltage change may be determined as the occurrence of a whisker code short circuit.
Furthermore, it is preferable for the above-mentioned “specific binary” to change following the fluctuation of the circuit voltage in order to detect the whisker cord short-circuit with high accuracy, but it is set so as to maintain a constant value and changes accordingly. It was not configured to do.

  Therefore, in view of this problem, the present invention eliminates the influence of the capacitor of the power supply circuit, eliminates malfunction due to inrush current, and further detects a shorted cord short circuit with high accuracy even if the circuit voltage fluctuates, and this An object of the present invention is to provide an outlet device including a cord short circuit detection circuit.

In order to solve the above-mentioned problem, a cord short-circuit detection circuit according to the invention of claim 1 includes a rectifier circuit that obtains a voltage waveform of an electric circuit that supplies commercial power to a load and performs full-wave rectification; A specific distortion detection circuit for detecting a specific waveform distortion from the waveform; an inrush voltage detection circuit for detecting a voltage change due to the inrush current of the load from the rectified voltage waveform of the rectifier circuit; and a determination circuit for determining occurrence of a cord short-circuit A power circuit that is independent of the rectifier circuit that supplies power to each circuit from the circuit, and the specific distortion detection circuit includes a predetermined first threshold value and a first threshold value that are less than a peak value of the circuit voltage A window comparator circuit that compares a smaller second threshold value with the rectified voltage waveform to detect a state in which an instantaneous value of the rectified voltage waveform is between the two threshold values; An average value circuit for generating a value, and a waveform distortion determination circuit that determines that a waveform distortion has occurred when a time between the two thresholds exceeds a certain time, and the inrush voltage detection circuit includes a circuit voltage wave A circuit that compares the voltage waveform with a predetermined third threshold value that is lower than a high value, wherein the determination circuit determines that the specific distortion detection circuit is waveform distortion, and the inrush voltage detection circuit is the voltage waveform. When it is determined that the peak value is greater than the third threshold value, it is determined that a code short circuit has occurred, and a code short circuit occurrence signal is output.
According to this configuration, since the rectifier circuit is provided independently of the power supply circuit, the output voltage waveform can reach 0 volts every half cycle without being affected by the capacitor. Therefore, even if the second threshold value is provided near 0 volts, the specific distortion detection circuit does not malfunction, so that it is possible to detect a cord short-circuit with high accuracy.
In addition, since the first and second threshold values are generated from the output of the rectifier circuit for detecting the cord short-circuit, it can be generated so as to fluctuate in accordance with the fluctuation of the circuit voltage, and can always be set to a predetermined ratio with respect to the circuit voltage. Even if voltage fluctuation occurs, highly accurate determination can be continued.
Furthermore, even if a large drop in the circuit voltage occurs instantaneously due to the inrush current, it is possible to detect a short circuit of the cord with high accuracy in any environment in order to eliminate a situation in which the short circuit is erroneously detected.

According to a second aspect of the present invention, there is provided an outlet device comprising: 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 cord short circuit detecting circuit according to claim 1 and an output circuit for driving the shutting device based on a code short circuit occurrence signal output from the code short circuit detecting circuit. And
According to this configuration, when a cord short-circuit occurs, it is detected and the electric circuit is interrupted to stop the outlet output. Therefore, it is possible to reliably prevent the occurrence of a fire due to the cord short-circuit.

According to the present invention, since the rectifier circuit is provided independently of the power supply circuit, the output voltage waveform can reach 0 volt every half cycle without being affected by the capacitor. Therefore, even if the second threshold value is provided near 0 volts, the specific distortion detection circuit does not malfunction, so that it is possible to detect a cord short-circuit with high accuracy.
In addition, since the first and second threshold values are generated from the output of the rectifier circuit for detecting the cord short-circuit, it can be generated so as to fluctuate in accordance with the fluctuation of the circuit voltage, and always has a predetermined ratio with respect to the circuit voltage. Even if voltage fluctuation occurs, highly accurate determination can be continued.
Furthermore, even if a large drop in the circuit voltage occurs instantaneously due to the inrush current, it is possible to detect a short circuit of the cord with high accuracy in any environment in order to eliminate a situation in which the short circuit is erroneously detected.

It is a circuit diagram which shows an example of the outlet apparatus which concerns on this invention. The rectification waveform of an electric circuit voltage is shown, (a) is a conventional waveform, (b) is a waveform of the rectifier circuit of FIG. It is a principal part wave form diagram of the specific distortion detection circuit at the time of code | cord | chord short circuit occurrence, (a) is an output waveform of a rectifier circuit, (b) is an output waveform of a window comparator circuit, (c) is an output waveform of an integration circuit, (d ) Shows the output waveform of the first comparison circuit, and (e) shows the output of the first one-shot pulse circuit. It is a principal part waveform diagram of the specific distortion detection circuit at the time of inrush current generation, (a) is an output waveform of a rectifier circuit, (b) is an output waveform of the 1st window comparator circuit, (c) is an output waveform of an integration circuit, (D) shows the output of the first one-shot pulse circuit. It is explanatory drawing of the output waveform of an inrush voltage detection circuit, (a) is an output waveform of a rectifier circuit, (b) is an output waveform of a 2nd comparison circuit and an integration circuit, (c) is an output waveform of a 3rd comparison circuit, respectively. Show. It is an electric circuit voltage waveform diagram 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, wherein 1 is an outlet device, 2 is a commercial power source, 3 is a load such as home appliances and lighting, 4 is an outlet, and L1 is an outlet device from the commercial power source 2. 1 is a load circuit extending from a plug (not shown) connected to the outlet 4 to the load 3. The outlet device 1 is usually used by being installed on a wall surface.

  As shown in FIG. 1, the outlet device 1 includes an opening / closing contact 7 provided on an electric path L3 from the power supply connecting portion connecting the electric circuit L1 to which the commercial power supply 2 is connected to the outlet 4, and a plunger 8a for opening the opening / closing contact 7. An electromagnetic coil 8, an output circuit 9 for driving the electromagnetic coil 8, and a cord short-circuit detecting circuit 11 for detecting a cord short-circuit.

  The cord short circuit detection circuit 11 includes a rectifier circuit 13 composed of a diode bridge circuit that full-wave rectifies the commercial voltage waveform flowing through the electric circuit L3, a specific distortion detection circuit 14 that detects a waveform peculiar to a mustache cord short circuit, and a load 3 when the load 3 is activated. An inrush voltage detection circuit 15 for detecting a voltage drop caused by the occurrence of an excessive inrush current, a second one-shot pulse circuit 16 as a determination circuit for determining the occurrence of a code short circuit, and a power supply circuit for supplying power to each circuit 17 or the like.

  The rectifier circuit 13 is provided independently of the rectifier circuit 17a provided in the power supply circuit 17, and no capacitor is disposed in the vicinity thereof. The rectified waveform output from the rectifier circuit 13 is shown in FIG. FIG. 2A shows a waveform output from the rectifier circuit of Patent Document 1. As shown in FIG. 2, the rectified waveform output from the rectifier circuit 13 rises after decreasing to 0 volts every half cycle.

  The specific distortion detection circuit 14 includes an average value circuit 19 for generating predetermined two values (a first threshold and a second threshold smaller than the first threshold) from the rectified voltage waveform, the generated two thresholds, A window comparator circuit (hereinafter simply referred to as “comparator circuit”) 20 for comparison, a waveform shaping circuit 21 for shaping the output waveform of the comparator circuit 20, a first integration circuit 22 for integrating the output waveform of the waveform shaping circuit 21, 1 includes a first comparison circuit 23 as a waveform distortion determination circuit that compares the output of the integration circuit 22 with a predetermined threshold, and a first one-shot pulse circuit 24 that receives the output of the first comparison circuit 23 and outputs a pulse signal. Yes.

  On the other hand, the inrush voltage detection circuit 15 includes a second comparison circuit 15a, a second integration circuit 15b, and a third comparison circuit 15c that compare the instantaneous value of the circuit voltage rectified by the rectification circuit 13 with a predetermined third threshold value. It consists of The third threshold value is set between the peak value of the circuit voltage and the first threshold value.

  The second one-shot pulse circuit 16 determines the occurrence of a code short circuit based on the outputs of the specific distortion detection circuit 14 and the inrush voltage detection circuit 15.

  Hereinafter, the operation of the cord short-circuit detection circuit 11 will be specifically described. FIG. 3 shows a waveform of a main part of the specific distortion detection circuit 14 when a cord short-circuit occurs, which will be described with reference to FIG. 3, (a) is the output waveform of the rectifier circuit 13, (b) is the output waveform of the comparator circuit 20, (c) is the output waveform of the integration circuit, (d) is the output waveform of the first comparison circuit, (E) shows the output of the first one-shot pulse circuit.

First, the voltage waveform of the electric circuit rectified by the rectifier circuit 13 is input to an average value circuit 19 for generating a threshold value to be described later. At this time, the voltage is divided by a resistor (hereinafter, a case where the voltage is divided by 1/10 will be described) and input. Although the output of the rectifier circuit 13 is averaged by the average value circuit 19, this output changes according to the fluctuation of the circuit voltage.
The threshold value of the comparator circuit 20 is generated by the averaged voltage, and the threshold value is set so as to always have a constant ratio with respect to the circuit voltage.

The comparator circuit 20 includes a threshold value (a higher first threshold value EH and a lower second threshold value EL) generated by the DC voltage output from the average value circuit 19, and rectification after voltage division by the rectifier circuit 13. The waveform is compared, and a specific signal is output while there is an instantaneous value of the rectified circuit voltage between the two threshold values.
Specifically, the comparator circuit 20 compares the electric circuit voltage waveform divided by 1/10 with the threshold value, and compares the voltage having a peak value of about 14 volts with the threshold value. In this case, for example, the first threshold value EH = 5 volts and the second threshold value EL = 1 volt are set and compared. FIG. 3A shows the relationship between the voltage waveform of the electric circuit L3 and the two threshold values EH and EL in the comparator circuit 20 set as described above.

  When a whisker code short circuit occurs, a voltage waveform having a notch as shown by S in FIG. 6 is generated. Therefore, the generation of this waveform takes several ms from several volts to about 70 volts, which is about 50% of the peak value. Judgment can be made using the characteristics that remain.

Therefore, the first threshold value EH is about 50% or less with respect to the crest value of the circuit voltage (70 V or less if the crest value of the circuit voltage is about 140 V), and the second threshold value EL is 3% or more (wave circuit voltage). If the high value is about 140V, set it to 4V or higher).
The threshold value is not a constant value, but is set by the average value circuit 19 at a constant ratio with respect to the circuit voltage. Therefore, if the electric circuit voltage is lowered, the threshold value is also lowered. The relationship between the first threshold value and the second threshold value may be further limited. The first fixed value EH is about 36% (50V) of the circuit voltage, and the second fixed value EL is about 7% ( 10V), it is possible to detect the cord short-circuit well.

  The waveform shaping circuit 21 receives the output of the comparator circuit 20 and outputs an “H” signal when the instantaneous voltage value is between the first threshold value EH and the second threshold value EL. Otherwise, the waveform shaping circuit 21 is “L”. Output a signal. FIG. 3B shows this output, and while the voltage waveform of the electric circuit L3 to be monitored is a normal sine wave, a constant signal having a narrow width (short time) shown in T1 is output. Indicates a state in which a wide (long time) signal as shown in T2 is output.

  The first integration circuit 22 integrates a rectangular wave that is an “H” signal output from the waveform shaping circuit 21 and outputs a signal M having a waveform as shown in FIG. As shown in FIG. 3C, a waveform M1 having a small peak value is output with respect to a normal sine wave, but a large peak value is obtained as indicated by M2 in response to a rectangular wave of T2 generated by a cord short circuit. Is output.

The first comparison circuit 23 compares the output of the integration circuit 22 with a constant voltage value (first set value) Th1, and outputs a signal N1 as shown in FIG. 3D when the threshold Th1 is exceeded. As shown in FIG. 3D, the threshold value Th1 is set to a specific value that does not reach in the case of a normal sine wave and reaches when a distortion as shown in S occurs.
Thus, when the integration value M2 of the rectangular wave T2 when the cord is short-circuited is received, the first comparison circuit 23 outputs the signal N1, and the output of the comparator circuit 20 outputs the signal “H” exceeds a certain time. Is detected.

  As shown in FIG. 3 (e), the first one-shot pulse circuit 24 receives the output N1 of the comparison circuit 23 and generates a signal N2 as an output signal of the specific distortion detection circuit 14 to the point A shown in FIG. Output.

Here, the operation of the specific distortion detection circuit 14 when an inrush current occurs will be described. 4A and 4B are waveform diagrams of essential parts of the specific distortion detection circuit 14 when an inrush current is generated. FIG. 4A is an output waveform of the rectifier circuit 13, FIG. 4B is an output waveform of the comparator circuit 20, and FIG. (D) shows the output of the first one-shot pulse circuit 24, that is, the output of the specific distortion detection circuit 14.
When an inrush current is generated, particularly when a large inrush current is generated, the circuit voltage is instantaneously greatly reduced and gradually recovered as shown by the voltage waveform V in FIG. As a result, the comparator circuit 20 outputs an “H” signal for a long time as shown in FIG. 4B, and the first integration circuit 22 outputs a large integrated waveform M as shown in FIG. 4C. As shown in FIG. 4D, the first one-shot pulse circuit 24 outputs the signal N2. That is, the specific distortion detection circuit 14 determines that the voltage drop due to the inrush current is the occurrence of the specific distortion.

  On the other hand, the operation of the inrush voltage output circuit 15 when an inrush current occurs is as follows. FIG. 5 shows the waveform of the main part of the inrush voltage detection circuit 15, which will be described with reference to FIG. 5A shows the output waveform of the rectifier circuit 13, FIG. 5B shows the output waveform of the second comparison circuit 15a and the integration circuit 15b, and FIG. 5C shows the output waveform of the third comparison circuit 5c. Yes.

  The second comparison circuit 15a compares the peak value of the circuit voltage with a constant voltage value (second set value as the third threshold value) Th2, and when the threshold value Th2 is exceeded, as shown in FIG. ”Signal is output, otherwise the“ L ”signal is output. The second set value Th2 is set to a value larger than the minimum value of the circuit voltage that decreases due to the inrush current, and outputs a “H” signal in a normal state, and does not output “H” when an inrush current occurs. Only when an inrush current occurs in L3, the peak value of the circuit voltage is set not to exceed the second set value.

  The waveform obtained by integrating the output of the second comparison circuit 15a in the integration circuit 15b is further compared with a constant voltage value (third set value) Th3 in the third comparison circuit 15c, and is “H” when the circuit voltage is not normal. Is reliably excluded, and a signal of “H” is always output to point B in a normal voltage state. As a result, when an inrush current occurs, the “H” signal is not output, and this state can be eliminated.

The second one-shot pulse circuit 16 outputs an “H” signal when both output “H” based on the output of the specific distortion detection circuit 14 and the output of the inrush voltage detection circuit 15. . As a result, the specific distortion detection circuit 14 outputs an “H” signal when an inrush current is generated as described above, but no output signal is generated because the output of the inrush current detection circuit 15 is “L”.
However, when both the output of the specific distortion detection circuit 14 and the output of the inrush voltage detection circuit 15 output “H” signals, an output signal (code short-circuit occurrence signal) is output to the output circuit 9, and the output circuit 9 The electromagnetic coil 8 is driven and the plunger 8a is pulled out. As a result, the opening / closing contact 7 opens and the supply of power to the load 3 is stopped.

Thus, since the rectifier circuit 13 is provided independently of the power supply circuit 17, the voltage waveform to be output can reach 0 volts every half cycle without being affected by the capacitor. Therefore, even if the second threshold value EL is provided near 0 point, the specific distortion detection circuit 14 does not malfunction, so that it is possible to detect a cord short-circuit with high accuracy.
Further, since the first threshold value EH and the second threshold value EL are generated from the rectified voltage of the rectifier circuit 13, it can be generated so as to fluctuate in accordance with the fluctuation of the circuit voltage, and can always be set to a predetermined ratio with respect to the circuit voltage. Even if voltage fluctuation occurs, highly accurate determination can be continued.
Furthermore, even if a large drop in the circuit voltage occurs instantaneously due to the inrush current, it is possible to detect a short circuit of the cord with high accuracy in any environment in order to eliminate a situation in which the short circuit is erroneously detected.
And if a cord short circuit occurs, it will be detected, the electric circuit will be cut off, and the outlet output will be stopped, so that it is possible to reliably prevent the occurrence of fire due to the cord short circuit.

In addition, although the said embodiment demonstrated the case where the cord short circuit detection circuit 11 was provided in the outlet, it may be incorporated in circuit interruptions, such as a branch breaker, or it may be incorporated in the tap outlet used by connecting to an outlet. May be.
In addition, the power outlet is provided with a shut-off function, and the power path is cut off. However, when a cord short-circuit occurs, a notification may be made by sound or LED light emission.
Further, the determination of the voltage drop due to the inrush current is added to the detection by the second comparison circuit 15a and the third comparison circuit 15c is further added via the second integration circuit 15b to improve the detection accuracy. It is also possible to determine only by

  1 .. Outlet device, 7 .. Open / close contact, 9 .. Output circuit, 11 .. Code short circuit detection circuit, 13 .. Rectifier circuit, 14 .. Specific distortion detection circuit, 15 .. Inrush voltage detection circuit, 16. 2nd one-shot pulse circuit (determination circuit), 17 .. Power supply circuit, 19 .. Average circuit, 20 .. Window comparator circuit, 23 .. First comparison circuit (waveform distortion determination circuit), 24. The first one-shot pulse circuit, EH, first threshold, EL, second threshold, Th2, third threshold.

Claims (2)

A rectifier circuit that obtains the voltage waveform of the electric circuit that supplies commercial power to the load and performs full-wave rectification,
A specific distortion detection circuit for detecting a specific waveform distortion from the rectified voltage waveform of the rectifier circuit;
An inrush voltage detection circuit for detecting a voltage change due to an inrush current of the load from a rectified voltage waveform of the rectifier circuit;
A determination circuit for determining the occurrence of a cord short circuit;
A power supply circuit independent of the rectifier circuit for supplying power from the electric circuit to each circuit;
The specific distortion detection circuit compares the rectified voltage waveform with a predetermined first threshold value lower than the peak value of the circuit voltage and a second threshold value smaller than the first threshold value, and an instantaneous value of the rectified voltage waveform is obtained. A window comparator circuit for detecting a state between the two threshold values;
An average value circuit for generating the two threshold values from the output of the rectifier circuit;
A waveform distortion determination circuit that determines that waveform distortion occurs when a time between the two thresholds exceeds a certain time,
The inrush voltage detection circuit is a circuit that compares the voltage waveform with a predetermined third threshold value that is lower than the peak value of the circuit voltage,
The determination circuit determines that a code short circuit has occurred when the specific distortion detection circuit determines that waveform distortion has occurred and the inrush voltage detection circuit determines that the peak value of the voltage waveform is greater than the third threshold value. A cord short circuit detection circuit that outputs a cord short circuit occurrence signal. 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.

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