JP7702286B2 - Detection Circuit - Google Patents

Description

The present invention relates to a detection circuit.

Patent Document 1 (Figure 4) describes a detection circuit that detects momentary power outages or missing phases by using a comparator to compare the voltage obtained by half-wave rectifying the three-phase voltage with a set voltage. A momentary power outage refers to an instantaneous power outage in three phases. A missing phase refers to a voltage drop in one of the three phases.

Japanese Unexamined Patent Publication No. 63-23516

There is a demand for a detection circuit to reliably detect momentary power outages or phase loss, and a demand not to detect very brief voltage fluctuations that do not correspond to momentary power outages or phase loss. The detection circuit described in Patent Document 1 has low design flexibility, meaning there are few adjustment elements and adjustment ranges, making it difficult to meet both of the above two demands.

The present invention aims to provide a detection circuit that can detect momentary power outages or missing phases without detecting voltage fluctuations.

A detection circuit according to one aspect of the present invention includes:
a three-phase full-wave rectifier circuit that outputs a first voltage obtained by full-wave rectifying a three-phase AC voltage;
a voltage division and delay circuit that outputs a second voltage obtained by dividing and delaying the first voltage;
a first comparator, the first input terminal of which receives the second voltage and the second input terminal of which receives a first threshold voltage, the first comparator outputting a third voltage of a first level when the second voltage is lower than the first threshold voltage and outputting the third voltage of a second level when the second voltage is higher than the first threshold voltage;
a threshold voltage changing circuit that shifts the first threshold voltage to a higher voltage side when the third voltage is at the first level;
a delay circuit that outputs a fourth voltage obtained by delaying the third voltage;
a second comparator, the first input terminal of which receives a second threshold voltage and the fourth voltage is input to a second input terminal of which, the second comparator outputs a fifth voltage of a third level when the fourth voltage is higher than the second threshold voltage and outputs the fifth voltage of a fourth level when the fourth voltage is lower than the second threshold voltage;
Including,
It is characterized by:

In the detection circuit,
The voltage divider delay circuit includes:
A first resistor, one end of which is electrically connected to the three-phase full-wave rectifier circuit;
a second resistor, one end of which is electrically connected to the other end of the first resistor and the other end of which is electrically connected to a reference potential;
a third resistor, one end of which is electrically connected to the other end of the first resistor and one end of the second resistor, and the other end of which is electrically connected to the first input terminal of the first comparator;
a first capacitor, one end of which is electrically connected to the other end of the third resistor and the first input terminal of the first comparator, and the other end of which is electrically connected to a reference potential;
Including,
It is characterized by:

In the detection circuit,
The threshold voltage changing circuit includes:
a fourth resistor, one end of which is supplied with a voltage higher than the third voltage and the other end of which is electrically connected to the output terminal of the first comparator;
a diode, the anode of which is electrically connected to the other end of the fourth resistor and the output terminal of the first comparator;
a fifth resistor, one end of which is electrically connected to the cathode of the diode and the other end of which is electrically connected to the second input terminal of the first comparator;
Including,
It is characterized by:

In the detection circuit,
The delay circuit is a low-pass filter.
It is characterized by:

In the detection circuit,
The delay circuit includes:
a sixth resistor, one end of which is electrically connected to the output terminal of the first comparator and the other end of which is electrically connected to the second input terminal of the second comparator;
a second capacitor, one end of which is electrically connected to the other end of the sixth resistor and the second input terminal of the second comparator, and the other end of which is electrically connected to a reference potential;
Including,
It is characterized by:

The detection circuit of one aspect of the present invention has the effect of providing a detection circuit that can detect momentary power outages or missing phases without detecting voltage fluctuations.

FIG. 1 is a diagram showing a configuration of an application example of a detection circuit according to an embodiment and a comparative example. FIG. 2 is a diagram showing the configuration of a detection circuit of a comparative example. FIG. 3 is a diagram showing operational waveforms in the detection circuit of the comparative example when a missing phase occurs. FIG. 4 is a diagram showing operational waveforms of the detection circuit of the comparative example when an instantaneous power outage and fluctuations in the three-phase AC voltage occur. FIG. 5 is a diagram showing a configuration of a detection circuit according to the embodiment. FIG. 6 is a diagram showing operational waveforms of the detection circuit according to the embodiment when a missing phase occurs. FIG. 7 is a diagram showing operational waveforms of the detection circuit according to the embodiment when an instantaneous power outage and fluctuations in three-phase AC voltage occur.

Below, an embodiment of the detection circuit of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment.

<Application Examples>
1 is a diagram showing a configuration of an application example of a detection circuit according to an embodiment and a comparative example. A power supply device 1 of the application example converts three-phase AC power input from an AC power supply 2 and outputs the converted power to a load 3.

The power supply device 1 includes an input circuit 21, a detection circuit 11 of the embodiment or a detection circuit 111 of the comparative example, a control circuit 22, and a main circuit 23.

A three-phase AC voltage is input to the input circuit 21 from the AC power source 2. The input circuit 21 is exemplified by a filter circuit, but the present disclosure is not limited thereto. The AC power source 2 is exemplified by a system power source, but the present disclosure is not limited thereto.

When the detection circuit 11 or 111 detects an instantaneous power outage or a phase loss of the three-phase AC voltage after passing through the input circuit 21, it outputs a high-level signal to the control circuit 22. When the detection circuit 11 or 111 does not detect an instantaneous power outage or a phase loss of the three-phase AC voltage after passing through the input circuit 21, it outputs a low-level signal to the control circuit 22. However, the present disclosure is not limited to this. The detection circuit 11 or 111 may output a low-level signal when it detects an instantaneous power outage or a phase loss of the three-phase AC voltage, and may output a high-level signal when it does not detect an instantaneous power outage or a phase loss of the three-phase AC voltage.

The control circuit 22 operates the main circuit 23 when the detection circuit 11 or 111 does not detect a momentary power outage or a missing phase. The control circuit 22 stops the main circuit 23 when the detection circuit 11 or 111 detects a momentary power outage or a missing phase.

The main circuit 23 is a converter circuit, but the present disclosure is not limited to this. Under the control of the control circuit 22, the main circuit 23 converts the three-phase AC voltage that has passed through the input circuit 21 into a DC voltage and outputs it to the load 3.

<Embodiments and Comparative Examples>
An embodiment will be described below, but in order to facilitate understanding of the embodiment, a comparative example will be described first.

Comparative Example
FIG. 2 is a diagram showing the configuration of a detection circuit of a comparative example.

The detection circuit 111 of the comparative example outputs a high-level signal when it detects a momentary power outage or a phase loss of the three-phase AC voltage. The detection circuit 111 outputs a low-level signal when it does not detect a momentary power outage or a phase loss of the three-phase AC voltage.

The detection circuit 111 includes a three-phase full-wave rectifier circuit 31, a voltage divider smoothing circuit 32, a resistive voltage divider circuit 33, and a first comparator 34.

The three-phase full-wave rectifier circuit 31 outputs a first voltage V1 obtained by full-wave rectifying a three-phase AC voltage. An example of the three-phase full-wave rectifier circuit 31 is a three-arm bridge diode, but the present disclosure is not limited thereto.

The voltage dividing and smoothing circuit 32 outputs a second voltage V2 obtained by resistively dividing and smoothing the first voltage V1. The voltage dividing and smoothing circuit 32 includes resistors 51 and 52 and a capacitor 53.

The resistors 51 and 52 form a resistive voltage divider circuit. One end of the resistor 51 is electrically connected to the three-phase full-wave rectifier circuit 31. One end of the resistor 52 is electrically connected to the other end of the resistor 51. The other end of the resistor 52 is electrically connected to a reference potential. The reference potential is exemplified by a ground potential, but the present disclosure is not limited thereto. One end of the capacitor 53 is electrically connected to the connection point between the resistors 51 and 52 and the inverting input terminal (- terminal) of the first comparator 34. The other end of the capacitor 53 is electrically connected to the reference potential. The capacitor 53 smoothes the voltage resistively divided by the resistors 51 and 52.

The resistive voltage divider circuit 33 includes resistors 61 and 62. The resistors 61 and 62 output a constant first threshold voltage Vth1, which is obtained by resistively dividing the power supply voltage Vcc, to the non-inverting input terminal (+ terminal) of the first comparator 34.

When the second voltage V2 is lower than the first threshold voltage Vth1, the first comparator 34 outputs a high-level third voltage V3.

When the second voltage V2 is higher than the first threshold voltage Vth1, the first comparator 34 outputs a low-level third voltage V3.

The detection circuit 111 can adjust only the first threshold voltage Vth1 and the voltage dividing and smoothing circuit 32 (consisting of resistors 51 and 52 and capacitor 53). In other words, the detection circuit 111 has low design flexibility.

Figure 3 shows the operating waveforms of the detection circuit of the comparative example when a phase loss occurs. In Figure 3, the horizontal axis represents time and the vertical axis represents voltage.

In FIG. 3, waveform 121 shows the voltage of the first threshold voltage Vth1. Waveform 122 shows the voltage of the second voltage V2. Waveform 123 shows the voltage of the third voltage V3.

Before the loss of a phase occurs at time _t0 , the second voltage V2 (waveform 122) fluctuates periodically.

When a phase loss occurs at timing _t0 , the extreme value on the low potential side of the second voltage V2 (waveform 122) decreases.

When the second voltage V2 (waveform 122) becomes lower than the first threshold voltage Vth1 (waveform 121) at timing _t1 , the third voltage V3 (waveform 123) changes from a low level to a high level.

When the second voltage V2 (waveform 122) becomes higher than the first threshold voltage Vth1 (waveform 121) at timing _t2 , the third voltage V3 (waveform 123) changes from a high level to a low level.

When the second voltage V2 (waveform 122) becomes lower than the first threshold voltage Vth1 (waveform 121) at timing _t3 , the third voltage V3 (waveform 123) changes from a low level to a high level.

When the second voltage V2 (waveform 122) becomes higher than the first threshold voltage Vth1 (waveform 121) at timing _t4 , the third voltage V3 (waveform 123) changes from a high level to a low level.

Figure 4 shows the operating waveforms of the detection circuit of the comparative example when an instantaneous power outage and fluctuations in the three-phase AC voltage occur. In Figure 4, the horizontal axis represents time and the vertical axis represents voltage.

In FIG. 4, waveform 121 shows the voltage of the first threshold voltage Vth1. Waveform 131 shows the voltage of the second voltage V2 when an instantaneous power outage occurs. Waveform 132 shows the voltage of the second voltage V2 when a fluctuation occurs. Waveform 133 shows the voltage of the third voltage V3 when an instantaneous power outage occurs. Waveform 134 shows the voltage of the third voltage V3 when a fluctuation occurs.

The case of an instantaneous power outage (waveform 131) will now be described. When an instantaneous power outage occurs at timing _t10 , the second voltage V2 (waveform 131) starts to decrease.

When the second voltage V2 (waveform 131) becomes lower than the first threshold voltage Vth1 (waveform 121) at timing _t11 , the third voltage V3 (waveform 133) changes from a low level to a high level.

When the second voltage V2 (waveform 131) becomes higher than the first threshold voltage Vth1 (waveform 121) at timing _t13 , the third voltage V3 (waveform 133) changes from a high level to a low level.

In the case of fluctuation (waveform 132), a fluctuation occurs at timing _t10 , and the second voltage V2 (waveform 132) starts to decrease.

When the second voltage V2 (waveform 132) becomes lower than the first threshold voltage Vth1 (waveform 121) at timing _t11 , the third voltage V3 (waveform 134) changes from a low level to a high level.

When the second voltage V2 (waveform 132) becomes higher than the first threshold voltage Vth1 (waveform 121) at timing _t12 , the third voltage V3 (waveform 134) changes from a high level to a low level.

The case where it is most difficult to detect a momentary power outage or a missing phase is when the periodically fluctuating second voltage V2 is at its highest. Also, when the load on the main circuit 23 (see FIG. 1) is light, even if a momentary power outage or a missing phase occurs, the second voltage V2 does not drop much due to the line capacitance of the three-phase AC, noise, and the charge stored in the capacitor connected for power factor improvement. In these cases, it is possible to set the first threshold voltage Vth1 high so that the detection circuit 111 can reliably detect a momentary power outage or a missing phase. However, if this is done, the detection circuit 111 will detect the fluctuation (see waveforms 132 and 134 in FIG. 4). As a result, the control circuit 22 will stop the main circuit 23.

(Embodiment)
Among the components of the detection circuit of the embodiment, the same components as those in the comparative example are given the same reference numerals and description thereof will be omitted.

Figure 5 shows the configuration of a detection circuit according to an embodiment.

The detection circuit 11 of the embodiment outputs a high-level signal when it detects a momentary power outage or a phase loss of the three-phase AC voltage. The detection circuit 11 outputs a low-level signal when it does not detect a momentary power outage or a phase loss of the three-phase AC voltage. However, the present disclosure is not limited to this. The detection circuit 11 may output a low-level signal when it detects a momentary power outage or a phase loss of the three-phase AC voltage, and may output a high-level signal when it does not detect a momentary power outage or a phase loss of the three-phase AC voltage.

Compared to the detection circuit 111 (see FIG. 2) of the comparative example, the detection circuit 11 of the embodiment includes a voltage division delay circuit 35 instead of the voltage division smoothing circuit 32. Compared to the detection circuit 111, the detection circuit 11 further includes a threshold voltage change circuit 36, a delay circuit 37, a resistive voltage division circuit 38, and a second comparator 39.

Compared to the voltage divider smoothing circuit 32 (see FIG. 2), the voltage divider delay circuit 35 further includes a resistor 54.

Resistor 51 corresponds to an example of a "first resistor" in the present disclosure. Resistor 52 corresponds to an example of a "second resistor" in the present disclosure. Resistor 54 corresponds to an example of a "third resistor" in the present disclosure. Capacitor 53 corresponds to an example of a "first capacitor" in the present disclosure.

One end of resistor 54 is electrically connected to the connection point between resistors 51 and 52. The other end of resistor 54 is electrically connected to one end of capacitor 53 and the inverting input terminal (- terminal) of first comparator 34.

The inverting input terminal (- terminal) of the first comparator 34 corresponds to an example of the "first input terminal" of the first comparator of the present disclosure.

The voltage divider delay circuit 35 can also be considered as a combination of a resistive voltage divider circuit (resistors 51 and 52) and a low-pass filter (resistor 54 and capacitor 53).

The voltage divider delay circuit 35 delays the second voltage V2 relative to the output voltage waveform of the three-phase full-wave rectification, preventing the effects of very short voltage fluctuations that do not correspond to momentary power outages or missing phases and that do not require detection.

The threshold voltage change circuit 36 includes resistors 71 and 73 and a diode 72.

Resistor 71 corresponds to an example of a "fourth resistor" in the present disclosure. Resistor 73 corresponds to an example of a "fifth resistor" in the present disclosure.

One end of resistor 71 is electrically connected to the power supply voltage Vcc, but the present disclosure is not limited to this. It is sufficient that a voltage higher than the third voltage V3 is supplied to one end of resistor 71. The other end of resistor 71 is electrically connected to the output terminal of the first comparator 34.

The anode of the diode 72 is electrically connected to the other end of the resistor 71 and the output terminal of the first comparator 34. The cathode of the diode 72 is electrically connected to one end of the resistor 73. The other end of the resistor 73 is electrically connected to the non-inverting input terminal (+ terminal) of the first comparator 34.

The non-inverting input terminal (+ terminal) of the first comparator 34 corresponds to an example of the "second input terminal" of the first comparator of the present disclosure.

When the first comparator 34 outputs a low-level voltage, a current flows from the power supply voltage Vcc through resistor 71 to the output terminal of the first comparator 34. In other words, a voltage drop of Vcc occurs in resistor 71. In this case, the anode of diode 72 is at a low level and the cathode is at the first threshold voltage Vth1, so the diode is in a reverse bias state and is non-conductive. Therefore, the first threshold voltage Vth1 does not change.

The low level of the third voltage V3 corresponds to an example of the "second level" of this disclosure.

When the first comparator 34 outputs a high-level voltage, the diode 72 is forward biased and becomes conductive. Therefore, the first threshold voltage Vth1 changes to a voltage obtained by subtracting the voltage drop across the resistor 73 from the high level of the first comparator 34.

The high level of the third voltage V3 corresponds to an example of the "first level" of this disclosure.

In other words, when the third voltage V3 is at a high level, the threshold voltage change circuit 36 shifts the first threshold voltage Vth1 to a higher voltage.

This allows the first comparator 34 to reliably detect a drop in the second voltage V2. In addition, the time during which the second voltage V2 is smaller than the first threshold voltage Vth1 becomes longer. In other words, the pulse width of the third voltage V3 becomes larger (see waveform 143 in FIG. 6 and waveform 155 in FIG. 7, which will be described later).

The delay circuit 37 includes a resistor 81 and a capacitor 82.

Resistor 81 corresponds to an example of a "sixth resistor" in the present disclosure. Capacitor 82 corresponds to an example of a "second capacitor" in the present disclosure.

One end of the resistor 81 is electrically connected to the output terminal of the first comparator 34. The other end of the resistor 81 is electrically connected to one end of the capacitor 82 and the non-inverting input terminal (+ terminal) of the second comparator 39.

The non-inverting input terminal (+ terminal) of the second comparator 39 corresponds to an example of the "second input terminal" of the second comparator of the present disclosure.

One end of the capacitor 82 is electrically connected to the other end of the resistor 81 and the non-inverting input terminal (+ terminal) of the second comparator 39. The other end of the capacitor 82 is electrically connected to the reference potential.

In other words, the delay circuit 37 is a first-order low-pass filter. The delay circuit 37 outputs the fourth voltage V4, which is the third voltage V3 delayed by the time constant CR, to the non-inverting input terminal (+ terminal) of the second comparator 39.

The delay time of the delay circuit 37 can be adjusted by the time constant CR, that is, by the resistance value of resistor 81 or the capacitance of capacitor 82.

The threshold voltage change circuit 36 and the delay circuit 37 can be adjusted independently. In addition, the adjustment range of the time constant CR increases as the pulse width of the third voltage V3 increases. In other words, the detection circuit 11 of the embodiment has high design flexibility.

The resistive voltage divider circuit 38 includes resistors 91 and 92. The resistors 91 and 92 output a constant second threshold voltage Vth2, which is obtained by resistively dividing the power supply voltage Vcc, to the inverting input terminal (- terminal) of the second comparator 39.

The inverting input terminal (- terminal) of the second comparator 39 corresponds to an example of the "first input terminal" of the second comparator of the present disclosure.

The second comparator 39 outputs a high-level fifth voltage V5 when the fourth voltage V4 is higher than the second threshold voltage Vth2.

The high level of the fifth voltage V5 corresponds to an example of the "third level" of this disclosure.

The second comparator 39 outputs a low-level fifth voltage V5 when the fourth voltage V4 is lower than the second threshold voltage Vth2.

The low level of the fifth voltage V5 corresponds to an example of the "fourth level" of this disclosure.

Figure 6 is a diagram showing the operating waveforms of the detection circuit of the embodiment when a phase loss occurs. In Figure 6, the horizontal axis represents time and the vertical axis represents voltage.

In FIG. 6, waveform 141 shows the voltage of the first threshold voltage Vth1. Waveform 142 shows the voltage of the second voltage V2. Waveform 143 shows the voltage of the third voltage V3. Waveform 144 shows the voltage of the second threshold voltage Vth2. Waveform 145 shows the voltage of the fourth voltage V4. Waveform 146 shows the voltage of the fifth voltage V5.

Before the loss of a phase occurs at time _t20 , the second voltage V2 (waveform 142) fluctuates periodically.

When a phase loss occurs at timing _t20 , the extreme value on the low potential side of the second voltage V2 (waveform 142) decreases.

When the second voltage V2 (waveform 142) becomes lower than the first threshold voltage Vth1 (waveform 141) at time _t21 , the first threshold voltage Vth1 (waveform 141) shifts to a higher potential. The third voltage V3 (waveform 143) changes from a low level to a high level. The fourth voltage V4 (waveform 145) starts to rise.

When the fourth voltage V4 (waveform 145) becomes higher than the second threshold voltage Vth2 (waveform 144) at timing _t22 , the fifth voltage V5 (waveform 146) changes from a low level to a high level.

When the second voltage V2 (waveform 142) becomes higher than the first threshold voltage Vth1 (waveform 141) at time _t23 , the first threshold voltage Vth1 (waveform 141) shifts to a lower potential side (returns to the original potential). The third voltage V3 (waveform 143) changes from a high level to a low level. The fourth voltage V4 (waveform 145) starts to decrease.

When the fourth voltage V4 (waveform 145) becomes lower than the second threshold voltage Vth2 (waveform 144) at timing _t24 , the fifth voltage V5 (waveform 146) changes from a high level to a low level.

When the second voltage V2 (waveform 142) becomes lower than the first threshold voltage Vth1 (waveform 141) at time _t25 , the first threshold voltage Vth1 (waveform 141) shifts to a higher potential. The third voltage V3 (waveform 143) changes from a low level to a high level. The fourth voltage V4 (waveform 145) starts to rise.

When the fourth voltage V4 (waveform 145) becomes higher than the second threshold voltage Vth2 (waveform 144) at timing _t26 , the fifth voltage V5 (waveform 146) changes from a low level to a high level.

When the second voltage V2 (waveform 142) becomes higher than the first threshold voltage Vth1 (waveform 141) at time _t27 , the first threshold voltage Vth1 (waveform 141) shifts to a lower potential (returns to the original potential). The third voltage V3 (waveform 143) changes from a high level to a low level. The fourth voltage V4 (waveform 145) starts to decrease.

When the fourth voltage V4 (waveform 145) becomes lower than the second threshold voltage Vth2 (waveform 144) at timing _t28 , the fifth voltage V5 (waveform 146) changes from a high level to a low level.

Figure 7 is a diagram showing the operating waveforms of the detection circuit of the embodiment when a momentary power outage and fluctuations in the three-phase AC voltage occur. In Figure 7, the horizontal axis represents time and the vertical axis represents voltage.

In FIG. 7, waveform 151 shows the voltage of the first threshold voltage Vth1 when an instantaneous power outage occurs. Waveform 152 shows the voltage of the first threshold voltage Vth1 when a fluctuation occurs. Waveform 153 shows the voltage of the second voltage V2 when an instantaneous power outage occurs. Waveform 154 shows the voltage of the second voltage V2 when a fluctuation occurs. Waveform 155 shows the voltage of the third voltage V3 when an instantaneous power outage occurs. Waveform 156 shows the voltage of the third voltage V3 when a fluctuation occurs. Waveform 157 shows the voltage of the second threshold voltage Vth2. Waveform 158 shows the voltage of the fourth voltage V4 when an instantaneous power outage occurs. Waveform 159 shows the voltage of the fourth voltage V4 when a fluctuation occurs. Waveform 160 shows the voltage of the fifth voltage V5 when an instantaneous power outage occurs. Waveform 161 shows the voltage of the fifth voltage V5 when a fluctuation occurs.

The case of an instantaneous power outage (waveform 153) will now be described. When an instantaneous power outage occurs at timing _t30 , the second voltage V2 (waveform 153) starts to decrease.

When the second voltage V2 (waveform 153) becomes lower than the first threshold voltage Vth1 (waveform 151) at time _t31 , the first threshold voltage Vth1 (waveform 151) shifts to a higher potential. The third voltage V3 (waveform 155) changes from a low level to a high level. The fourth voltage V4 (waveform 158) starts to rise.

When the fourth voltage V4 (waveform 158) becomes higher than the second threshold voltage Vth2 (waveform 157) at timing _t32 , the fifth voltage V5 (waveform 160) changes from a low level to a high level.

When the second voltage V2 (waveform 153) becomes higher than the first threshold voltage Vth1 (waveform 151) at timing _t33 , the first threshold voltage Vth1 (waveform 151) shifts to a lower potential side (returns to the original potential). The third voltage V3 (waveform 155) changes from a high level to a low level. The fourth voltage V4 (waveform 158) starts to decrease.

When the fourth voltage V4 (waveform 158) becomes lower than the second threshold voltage Vth2 (waveform 157) at timing _t34 , the fifth voltage V5 (waveform 160) changes from a high level to a low level.

In the case of fluctuation (waveform 154), a fluctuation occurs at time _t30 , and the second voltage V2 (waveform 154) starts to decrease.

When the second voltage V2 (waveform 154) becomes lower than the first threshold voltage Vth1 (waveform 152) at time _t31 , the first threshold voltage Vth1 (waveform 152) shifts to a higher potential. The third voltage V3 (waveform 156) changes from a low level to a high level. The fourth voltage V4 (waveform 159) starts to rise.

When the second voltage V2 (waveform 154) becomes higher than the first threshold voltage Vth1 (waveform 152) at time _t32 , the first threshold voltage Vth1 (waveform 152) shifts to a lower potential (returns to the original potential). The third voltage V3 (waveform 156) changes from a high level to a low level. The fourth voltage V4 (waveform 159) starts to decrease. The fifth voltage V5 (waveform 161) remains at a low level.

(summary)
In the detection circuit 11 according to the embodiment, the threshold voltage change circuit 36 and the delay circuit 37 can be adjusted independently. In addition, the adjustment range of the time constant CR increases as the pulse width of the third voltage V3 increases. In other words, the detection circuit 11 according to the embodiment has high design flexibility.

The detection circuit 11 of the embodiment can reliably detect missing phases (see waveform 142 in FIG. 6) and momentary power outages (see waveform 153 in FIG. 7) without detecting fluctuations (see waveform 154 in FIG. 7) by adjusting the constant of the voltage divider delay circuit 35 and the time constant CR.

Therefore, the detection circuit 11 of the embodiment can prevent the control circuit 22 (see FIG. 1) from stopping the main circuit 23 (see FIG. 1) when a fluctuation (see waveform 154 in FIG. 7) occurs.

(Additional Note)
In the embodiment, the detection circuit 11 is realized by an analog circuit, but the present disclosure is not limited to this. The detection circuit 11 can also be realized by a digital circuit.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and gist of the invention.

REFERENCE SIGNS LIST 1 Power supply device 2 AC power supply 3 Load 11, 111 Detection circuit 21 Input circuit 22 Control circuit 23 Main circuit 31 Three-phase full-wave rectifier circuit 32 Voltage dividing smoothing circuit 33, 38 Resistive voltage dividing circuit 34 First comparator 35 Voltage dividing delay circuit 36 Threshold voltage changing circuit 37 Delay circuit 39 Second comparator 51, 52, 54, 61, 62, 71, 73, 81, 91, 92 Resistor 53, 82 Capacitor 72 Diode

Claims (5)

a three-phase full-wave rectifier circuit that outputs a first voltage obtained by full-wave rectifying a three-phase AC voltage;
a voltage division and delay circuit that outputs a second voltage obtained by dividing and delaying the first voltage;
a first comparator, the first input terminal of which receives the second voltage and the second input terminal of which receives a first threshold voltage, the first comparator outputting a third voltage of a first level when the second voltage is lower than the first threshold voltage and outputting the third voltage of a second level when the second voltage is higher than the first threshold voltage;
a threshold voltage changing circuit that shifts the first threshold voltage to a higher voltage side when the third voltage is at the first level;
a delay circuit that outputs a fourth voltage obtained by delaying the third voltage;
a second comparator, the first input terminal of which receives a second threshold voltage and the fourth voltage is input to a second input terminal of which, the second comparator outputs a fifth voltage of a third level when the fourth voltage is higher than the second threshold voltage and outputs the fifth voltage of a fourth level when the fourth voltage is lower than the second threshold voltage;
Including ,
When fluctuations occur in the three-phase AC,
At a first timing when the fluctuation occurs, the voltage dividing delay circuit starts to decrease the second voltage;
at a second timing when the second voltage becomes lower than the first threshold voltage, the first comparator changes the third voltage from the second level to the first level, the threshold voltage changing circuit shifts the first threshold voltage to a high potential side, and the delay circuit starts to increase the fourth voltage;
At a third timing when the second voltage becomes higher than the first threshold voltage, the first comparator changes the third voltage from a first level to a second level, the threshold voltage changing circuit shifts the first threshold voltage to a lower potential side, the delay circuit starts to decrease the fourth voltage, and the second comparator maintains the fifth voltage at the fourth level.
As a result, the occurrence of the fluctuation is not detected.
A detection circuit comprising: The voltage divider delay circuit includes:
A first resistor, one end of which is electrically connected to the three-phase full-wave rectifier circuit;
a second resistor, one end of which is electrically connected to the other end of the first resistor and the other end of which is electrically connected to a reference potential;
a third resistor, one end of which is electrically connected to the other end of the first resistor and one end of the second resistor, and the other end of which is electrically connected to the first input terminal of the first comparator;
a first capacitor, one end of which is electrically connected to the other end of the third resistor and the first input terminal of the first comparator, and the other end of which is electrically connected to a reference potential;
Including,
2. The detection circuit according to claim 1 , The threshold voltage changing circuit includes:
a fourth resistor, one end of which is supplied with a voltage higher than the third voltage and the other end of which is electrically connected to the output terminal of the first comparator;
a diode, the anode of which is electrically connected to the other end of the fourth resistor and the output terminal of the first comparator;
a fifth resistor, one end of which is electrically connected to the cathode of the diode and the other end of which is electrically connected to the second input terminal of the first comparator;
Including,
3. A detection circuit as claimed in claim 1 or 2. The delay circuit is a low-pass filter.
A detection circuit according to any one of claims 1 to 3, characterized in that it comprises: The delay circuit includes:
a sixth resistor, one end of which is electrically connected to the output terminal of the first comparator and the other end of which is electrically connected to the second input terminal of the second comparator;
a second capacitor, one end of which is electrically connected to the other end of the sixth resistor and the second input terminal of the second comparator, and the other end of which is electrically connected to a reference potential;
Including,
5. The detection circuit according to claim 4, wherein the detection circuit comprises:

Images