Detection circuit

Abstract

To provide a detection circuit capable of detecting an instantaneous power failure or a phase interruption without detecting fluctuation in voltage.SOLUTION: A detection circuit comprises: a three-phase all-wavelength rectification circuit that outputs a first voltage used for rectifying all wavelength of a three-phase AC; a partial-pressure delay circuit that outputs a second voltage obtained by parting and delaying the first voltage; a first comparator that outputs a third voltage at a first level when the second voltage is lower than a first threshold value voltage, and outputs a third voltage at a second level when the second voltage is higher than the first threshold value; a threshold value voltage change circuit that shifts the first threshold value voltage to a high 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; and a second comparator that outputs a fifth voltage at a third level when the fourth voltage is higher than a second threshold value voltage, and outputs a fifth voltage at the fourth level when the fourth voltage is lower than the second threshold value voltage.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a detection circuit.

Background Art

[0002] Patent Document 1 (Figure 4) describes a detection circuit that detects instantaneous power failure or open phase by comparing a voltage obtained by half-wave rectifying a three-phase voltage with a set voltage. Instantaneous power failure means that the three phases are instantaneously powered off. Open phase means that any one of the three phases has a voltage drop.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There are demands for a detection circuit to reliably detect instantaneous power failure or open phase and not to detect short-term voltage fluctuations that do not correspond to instantaneous power failure or open phase. In the detection circuit described in Patent Document 1, the design flexibility is low, that is, the adjustment elements and the adjustment range are small, and it is difficult to meet both of the above two demands.

[0005] An object of the present invention is to provide a detection circuit that can detect instantaneous power failure or open phase without detecting voltage fluctuations.

Means for Solving the Problems

[0006] 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 alternating current; a voltage division delay circuit that outputs a second voltage obtained by dividing and delaying the first voltage; The second voltage is input to the first input terminal, the first threshold voltage is input to the second input terminal, a third voltage of a first level is output when the second voltage is lower than the first threshold voltage, and the third voltage of a second level is output when the second voltage is higher than the first threshold voltage; a first comparator; A threshold voltage changing circuit that shifts the first threshold voltage to the high 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 threshold voltage is input to the first input terminal, the fourth voltage is input to the second input terminal, a fifth voltage of a third level is output when the fourth voltage is higher than the second threshold voltage, and a fifth voltage of a fourth level is output when the fourth voltage is lower than the second threshold voltage; a second comparator; Including Characterized by

[0007] In the detection circuit The voltage dividing and delaying circuit A first resistor having one end electrically connected to the three-phase full-wave rectifier circuit; A second resistor having one end electrically connected to the other end of the first resistor and the other end electrically connected to the reference potential; A third resistor having one end electrically connected to the other end of the first resistor and one end of the second resistor and the other end electrically connected to the first input terminal of the first comparator; A first capacitor having one end electrically connected to the other end of the third resistor and the first input terminal of the first comparator and the other end electrically connected to the reference potential; Including Characterized by

[0008] In the detection circuit The threshold voltage changing circuit A fourth resistor having a voltage higher than the third voltage supplied to one end and the other end electrically connected to the output terminal of the first comparator; A diode having an anode electrically connected to the other end of the fourth resistor and the output terminal of the first comparator; A fifth resistor having one end electrically connected to the cathode of the diode and the other end electrically connected to the second input terminal of the first comparator, including, characterized in that.

[0009] In the detection circuit, The delay circuit is a low-pass filter, characterized in that.

[0010] In the detection circuit, The delay circuit is, A sixth resistor having one end electrically connected to the output terminal of the first comparator and the other end electrically connected to the second input terminal of the second comparator, A second capacitor having one end electrically connected to the other end of the sixth resistor and the second input terminal of the second comparator and the other end electrically connected to a reference potential, including, characterized in that.

Effect of the Invention

[0011] The detection circuit according to one aspect of the present invention can provide a detection circuit that can detect an instantaneous power failure or a phase failure without detecting voltage fluctuations.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments 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 by this embodiment.

[0014] <Application Example> FIG. 1 is a diagram showing the configuration of an application example of the detection circuits according to the embodiment and the comparative example. The power supply device 1 of the application example converts three-phase AC power input from the AC power supply 2 and outputs it to the load 3.

[0015] The power supply device 1 includes an input circuit 21, a detection circuit 11 according to the embodiment or a detection circuit 111 according to the comparative example, a control circuit 22, and a main circuit 23.

[0016] A three-phase AC voltage is input to the input circuit 21 from the AC power supply 2. The input circuit 21 is exemplified by a filter circuit, but the present disclosure is not limited thereto. The AC power supply 2 is exemplified by a utility power supply, but the present disclosure is not limited thereto.

[0017] When the detection circuit 11 or 111 detects an instantaneous power failure or a phase failure 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 failure or a phase failure 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 thereto. The detection circuit 11 or 111 may output a low-level signal when detecting an instantaneous power failure or a phase failure of the three-phase AC voltage, and output a high-level signal when not detecting an instantaneous power failure or a phase failure of the three-phase AC voltage.

[0018] When the detection circuit 11 or 111 does not detect an instantaneous power failure or a phase failure, the control circuit 22 operates the main circuit 23. When the detection circuit 11 or 111 detects an instantaneous power failure or a phase failure, the control circuit 22 stops the main circuit 23.

[0019] The main circuit 23 is a converter circuit, but the present disclosure is not limited thereto. Under the control of the control circuit 22, the main circuit 23 power-converts the three-phase AC voltage after passing through the input circuit 21 into a DC voltage and outputs it to the load 3.

[0020] <Embodiments and Comparative Examples> Hereinafter, embodiments will be described. For the sake of easy understanding of the embodiments, the comparative examples will be described first.

[0021] (Comparative Example) FIG. 2 is a diagram showing the configuration of the detection circuit of the comparative example.

[0022] When the detection circuit 111 of the comparative example detects an instantaneous power failure or a phase failure of the three-phase AC voltage, it outputs a high-level signal. When the detection circuit 111 does not detect an instantaneous power failure or a phase failure of the three-phase AC voltage, it outputs a low-level signal.

[0023] The detection circuit 111 includes a three-phase full-wave rectifier circuit 31, a voltage-dividing smoothing circuit 32, a resistance voltage-dividing circuit 33, and a first comparator 34.

[0024] The three-phase full-wave rectifier circuit 31 outputs a first voltage V1 obtained by full-wave rectifying the three-phase AC voltage. The three-phase full-wave rectifier circuit 31 is exemplified by a three-arm bridge diode, but the present disclosure is not limited thereto.

[0025] The voltage-dividing smoothing circuit 32 outputs a second voltage V2 obtained by resistance voltage-dividing and smoothing the first voltage V1. The voltage-dividing smoothing circuit 32 includes resistors 51 and 52 and a capacitor 53.

[0026] Resistors 51 and 52 form a resistive voltage divider circuit. One end of resistor 51 is electrically connected to the three-phase full-wave rectifier circuit 31. One end of resistor 52 is electrically connected to the other end of resistor 51. The other end of resistor 52 is electrically connected to the reference potential. The reference potential is exemplified by the ground potential, but the present disclosure is not limited thereto. One end of capacitor 53 is electrically connected to the connection point between resistor 51 and resistor 52 and the inverting input terminal (- terminal) of the first comparator 34. The other end of capacitor 53 is electrically connected to the reference potential. Capacitor 53 smoothes the voltage divided by resistors 51 and 52.

[0027] The resistive voltage divider circuit 33 includes resistors 61 and 62. Resistors 61 and 62 output a constant first threshold voltage Vth1 obtained by dividing the power supply voltage Vcc to the non-inverting input terminal (+ terminal) of the first comparator 34.

[0028] When the second voltage V2 is lower than the first threshold voltage Vth1, the first comparator 34 outputs a high-level third voltage V3.

[0029] When the second voltage V2 is higher than the first threshold voltage Vth1, the first comparator 34 outputs a low-level third voltage V3.

[0030] What can be adjusted by the detection circuit 111 is the first threshold voltage Vth1 and the voltage dividing and smoothing circuit 32 (composed of resistors 51 and 52 and capacitor 53). That is, the detection circuit 111 has low design flexibility.

[0031] FIG. 3 is a diagram showing the operation waveform of the detection circuit of the comparative example when a phase failure occurs. In FIG. 3, the horizontal axis represents time and the vertical axis represents voltage.

[0032] In FIG. 3, waveform 121 indicates the voltage of the first threshold voltage Vth1. Waveform 122 indicates the voltage of the second voltage V2. Waveform 123 indicates the voltage of the third voltage V3.

[0033] Before a phase failure occurs at timing t0, the second voltage V2 (waveform 122) fluctuates periodically.

[0034] When a phase loss occurs at timing t0, the second voltage V2 (waveform 122) has a reduced extreme value on the low potential side.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] FIG. 4 is a diagram showing the operation waveforms of the detection circuit of the comparative example when an instantaneous power failure and fluctuations in the three-phase AC voltage occur. In FIG. 4, the horizontal axis represents time, and the vertical axis represents voltage.

[0040] In FIG. 4, waveform 121 indicates the voltage of the first threshold voltage Vth1. Waveform 131 indicates the voltage of the second voltage V2 when an instantaneous power failure occurs. Waveform 132 indicates the voltage of the second voltage V2 when fluctuations occur. Waveform 133 indicates the voltage of the third voltage V3 when an instantaneous power failure occurs. Waveform 134 indicates the voltage of the third voltage V3 when fluctuations occur.

[0041] The case of an instantaneous power failure (waveform 131) will be described. At timing t 10 when an instantaneous power failure occurs, the second voltage V2 (waveform 131) starts to decline.

[0042] Timing t 11 When the second voltage V2 (waveform 131) becomes lower than the first threshold voltage Vth1 (waveform 121) at timing t, the third voltage V3 (waveform 133) changes from the low level to the high level.

[0043] Timing t 13 When the second voltage V2 (waveform 131) becomes higher than the first threshold voltage Vth1 (waveform 121) at timing t, the third voltage V3 (waveform 133) changes from the high level to the low level.

[0044] The case of fluctuation (waveform 132) will be described. At timing t 10 When a fluctuation occurs at timing t, the second voltage V2 (waveform 132) starts to decline.

[0045] Timing t 11 When the second voltage V2 (waveform 132) becomes lower than the first threshold voltage Vth1 (waveform 121) at timing t, the third voltage V3 (waveform 134) changes from the low level to the high level.

[0046] Timing t 12 When the second voltage V2 (waveform 132) becomes higher than the first threshold voltage Vth1 (waveform 121) at timing t, the third voltage V3 (waveform 134) changes from the high level to the low level.

[0047] The case where momentary power failure or phase loss is most difficult to detect is when the periodically fluctuating second voltage V2 is the highest. Also, when the load of the main circuit 23 (see FIG. 1) is light, even if there is a momentary power failure or phase loss, due to the charge stored in the capacitor connected for the line capacitance, noise, and power factor improvement of the three-phase alternating current, the second voltage V2 does not drop much. In these cases, in order for the detection circuit 111 to surely detect momentary power failure or phase loss, it is conceivable to set the first threshold voltage Vth1 high. 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.

[0048] (Embodiment) Among the components of the detection circuit according to the embodiment, the same components as those in the comparative example are denoted by the same reference numerals, and the description thereof is omitted.

[0049] FIG. 5 is a diagram showing the configuration of the detection circuit according to the embodiment.

[0050] When the detection circuit 11 according to the embodiment detects an instantaneous power failure or a phase failure of a three-phase AC voltage, it outputs a high-level signal. When the detection circuit 11 does not detect an instantaneous power failure or a phase failure of the three-phase AC voltage, it outputs a low-level signal. However, the present disclosure is not limited thereto. When the detection circuit 11 detects an instantaneous power failure or a phase failure of the three-phase AC voltage, it may output a low-level signal, and when the detection circuit 11 does not detect an instantaneous power failure or a phase failure of the three-phase AC voltage, it may output a high-level signal.

[0051] The detection circuit 11 according to the embodiment includes a voltage division delay circuit 35 instead of the voltage division smoothing circuit 32 as compared with the detection circuit 111 (see FIG. 2) of the comparative example. Further, the detection circuit 11 further includes a threshold voltage change circuit 36, a delay circuit 37, a resistance voltage division circuit 38, and a second comparator 39 as compared with the detection circuit 111.

[0052] The voltage division delay circuit 35 further includes a resistor 54 as compared with the voltage division smoothing circuit 32 (see FIG. 2).

[0053] The resistor 51 corresponds to an example of the "first resistor" of the present disclosure. The resistor 52 corresponds to an example of the "second resistor" of the present disclosure. The resistor 54 corresponds to an example of the "third resistor" of the present disclosure. The capacitor 53 corresponds to an example of the "first capacitor" of the present disclosure.

[0054] One end of the resistor 54 is electrically connected to the connection point between the resistor 51 and the resistor 52. The other end of the resistor 54 is electrically connected to one end of the capacitor 53 and the inverting input terminal (- terminal) of the first comparator 34.

[0055] 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.

[0056] The voltage dividing delay circuit 35 can also be considered as a combination of a resistive voltage dividing circuit (resistors 51 and 52) and a low-pass filter (resistor 54 and capacitor 53).

[0057] The voltage dividing delay circuit 35 can delay the second voltage V2 with respect to the output voltage waveform of the three-phase full-wave rectification, and can prevent the influence of voltage fluctuations in a very short time that are not considered to be momentary power outages or phase failures and for which detection is not desired.

[0058] The threshold voltage change circuit 36 includes resistors 71 and 73 and a diode 72.

[0059] Resistor 71 corresponds to an example of the "fourth resistor" of the present disclosure. Resistor 73 corresponds to an example of the "fifth resistor" of the present disclosure.

[0060] One end of resistor 71 is electrically connected to the power supply voltage Vcc, but the present disclosure is not limited thereto. A voltage higher than the third voltage V3 may be 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.

[0061] The anode of diode 72 is electrically connected to the other end of resistor 71 and the output terminal of the first comparator 34. The cathode of diode 72 is electrically connected to one end of resistor 73. The other end of resistor 73 is electrically connected to the non-inverting input terminal (+ terminal) of the first comparator 34.

[0062] 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.

[0063] When the first comparator 34 outputs a low-level voltage, a current flows from the power supply voltage Vcc to the output terminal of the first comparator 34 via the resistor 71. That is, in the resistor 71, a voltage drop of Vcc occurs. In this case, since the anode of the diode 72 is at a low level and the cathode is at the first threshold voltage Vth1, it is in a reverse bias state and non-conductive. Therefore, the first threshold voltage Vth1 does not change.

[0064] The low level of the third voltage V3 corresponds to an example of the "second level" of the present disclosure.

[0065] When the first comparator 34 outputs a high-level voltage, the diode 72 is in a forward bias state and 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.

[0066] The high level of the third voltage V3 corresponds to an example of the "first level" of the present disclosure.

[0067] That is, when the third voltage V3 is at a high level, the threshold voltage change circuit 36 shifts the first threshold voltage Vth1 to the high voltage side.

[0068] Thereby, the first comparator 34 can surely detect the decrease in the second voltage V2. Also, the time when (the second voltage V2) < (the first threshold voltage Vth1) becomes longer. That is, the pulse width of the third voltage V3 becomes larger (see waveforms 143 in FIG. 6 and 155 in FIG. 7 described later).

[0069] The delay circuit 37 includes a resistor 81 and a capacitor 82.

[0070] The resistor 81 corresponds to an example of the "sixth resistor" of the present disclosure. The capacitor 82 corresponds to an example of the "second capacitor" of the present disclosure.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] That is, the delay circuit 37 is a first-order low-pass filter. The delay circuit 37 outputs a fourth voltage V4 obtained by delaying the third voltage V3 by a time constant CR to the non-inverting input terminal (+ terminal) of the second comparator 39.

[0075] The delay time of the delay circuit 37 can be adjusted by the time constant CR, that is, it can be adjusted by the resistance value of the resistor 81 or the capacitance of the capacitor 82.

[0076] The threshold voltage change circuit 36 and the delay circuit 37 can be adjusted independently of each other. Also, as the pulse width of the third voltage V3 increases, the adjustment range of the time constant CR increases. That is, the detection circuit 11 of the embodiment has high design flexibility.

[0077] The resistor voltage division circuit 38 includes resistors 91 and 92. The resistors 91 and 92 output a constant second threshold voltage Vth2 obtained by dividing the power supply voltage Vcc by resistance to the inverting input terminal (- terminal) of the second comparator 39.

[0078] 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.

[0079] The second comparator 39 outputs a high-level fifth voltage V5 when the fourth voltage V4 is higher than the second threshold voltage Vth2.

[0080] The high level of the fifth voltage V5 corresponds to an example of the "third level" of the present disclosure.

[0081] When the fourth voltage V4 is lower than the second threshold voltage Vth2, the second comparator 39 outputs a low-level fifth voltage V5.

[0082] The low level of the fifth voltage V5 corresponds to an example of the "fourth level" of the present disclosure.

[0083] FIG. 6 is a diagram showing the operation waveforms of the detection circuit according to the embodiment when a phase failure occurs. In FIG. 6, the horizontal axis represents time and the vertical axis represents voltage.

[0084] In FIG. 6, waveform 141 indicates the voltage of the first threshold voltage Vth1. Waveform 142 indicates the voltage of the second voltage V2. Waveform 143 indicates the voltage of the third voltage V3. Waveform 144 indicates the voltage of the second threshold voltage Vth2. Waveform 145 indicates the voltage of the fourth voltage V4. Waveform 146 indicates the voltage of the fifth voltage V5.

[0085] Timing t 20 Before a phase failure occurs at timing t, the second voltage V2 (waveform 142) fluctuates periodically.

[0086] Timing t 20 When a phase failure occurs at timing t, the second voltage V2 (waveform 142) has a lower extreme value on the low potential side.

[0087] Timing t 21 When the second voltage V2 (waveform 142) becomes lower than the first threshold voltage Vth1 (waveform 141) at timing t, the first threshold voltage Vth1 (waveform 141) shifts to the high potential side. The third voltage V3 (waveform 143) changes from a low level to a high level. The fourth voltage V4 (waveform 145) starts to rise.

[0088] Timing t 22 When the fourth voltage V4 (waveform 145) becomes higher than the second threshold voltage Vth2 (waveform 144) at timing t, the fifth voltage V5 (waveform 146) changes from a low level to a high level.

[0089] Timing t 23 When the second voltage V2 (waveform 142) becomes higher than the first threshold voltage Vth1 (waveform 141) at time t, the first threshold voltage Vth1 (waveform 141) shifts (returns) to the low potential side. The third voltage V3 (waveform 143) changes from the high level to the low level. The fourth voltage V4 (waveform 145) starts to decline.

[0090] Timing t 24 When the fourth voltage V4 (waveform 145) becomes lower than the second threshold voltage Vth2 (waveform 144) at time t, the fifth voltage V5 (waveform 146) changes from the high level to the low level.

[0091] Timing t 25 When the second voltage V2 (waveform 142) becomes lower than the first threshold voltage Vth1 (waveform 141) at time t, the first threshold voltage Vth1 (waveform 141) shifts to the high potential side. The third voltage V3 (waveform 143) changes from the low level to the high level. The fourth voltage V4 (waveform 145) starts to rise.

[0092] Timing t 26 When the fourth voltage V4 (waveform 145) becomes higher than the second threshold voltage Vth2 (waveform 144) at time t, the fifth voltage V5 (waveform 146) changes from the low level to the high level.

[0093] Timing t 27 When the second voltage V2 (waveform 142) becomes higher than the first threshold voltage Vth1 (waveform 141) at time t, the first threshold voltage Vth1 (waveform 141) shifts (returns) to the low potential side. The third voltage V3 (waveform 143) changes from the high level to the low level. The fourth voltage V4 (waveform 145) starts to decline.

[0094] Timing t 28 When the fourth voltage V4 (waveform 145) becomes lower than the second threshold voltage Vth2 (waveform 144) at time t, the fifth voltage V5 (waveform 146) changes from the high level to the low level.

[0095] FIG. 7 is a diagram showing the operation waveforms of the detection circuit according to the embodiment when an instantaneous power failure and fluctuations in the three-phase AC voltage occur. In FIG. 7, the horizontal axis represents time, and the vertical axis represents voltage.

[0096] In FIG. 7, waveform 151 indicates the voltage of the first threshold voltage Vth1 when an instantaneous power failure occurs. Waveform 152 indicates the voltage of the first threshold voltage Vth1 when fluctuations occur. Waveform 153 indicates the voltage of the second voltage V2 when an instantaneous power failure occurs. Waveform 154 indicates the voltage of the second voltage V2 when fluctuations occur. Waveform 155 indicates the voltage of the third voltage V3 when an instantaneous power failure occurs. Waveform 156 indicates the voltage of the third voltage V3 when fluctuations occur. Waveform 157 indicates the voltage of the second threshold voltage Vth2. Waveform 158 indicates the voltage of the fourth voltage V4 when an instantaneous power failure occurs. Waveform 159 indicates the voltage of the fourth voltage V4 when fluctuations occur. Waveform 160 indicates the voltage of the fifth voltage V5 when an instantaneous power failure occurs. Waveform 161 indicates the voltage of the fifth voltage V5 when fluctuations occur.

[0097] Regarding the case of an instantaneous power failure (waveform 153), at timing t 30 when an instantaneous power failure occurs, the second voltage V2 (waveform 153) starts to decrease.

[0098] At timing t 31 when the second voltage V2 (waveform 153) becomes lower than the first threshold voltage Vth1 (waveform 151), the first threshold voltage Vth1 (waveform 151) shifts to the high potential side. The third voltage V3 (waveform 155) changes from the low level to the high level. The fourth voltage V4 (waveform 158) starts to rise.

[0099] At timing t 32 when the fourth voltage V4 (waveform 158) becomes higher than the second threshold voltage Vth2 (waveform 157), the fifth voltage V5 (waveform 160) changes from the low level to the high level.

[0100] At timing t 33When the second voltage V2 (waveform 153) becomes higher than the first threshold voltage Vth1 (waveform 151), the first threshold voltage Vth1 (waveform 151) shifts (returns) to the low potential side. The third voltage V3 (waveform 155) changes from the high level to the low level. The fourth voltage V4 (waveform 158) starts to decline.

[0101] Timing t 34 When the fourth voltage V4 (waveform 158) becomes lower than the second threshold voltage Vth2 (waveform 157), the fifth voltage V5 (waveform 160) changes from the high level to the low level.

[0102] The case of fluctuation (waveform 154) will be described. Timing t 30 When a fluctuation occurs at timing t, the second voltage V2 (waveform 154) starts to decline.

[0103] Timing t 31 When the second voltage V2 (waveform 154) becomes lower than the first threshold voltage Vth1 (waveform 152) at timing t, the first threshold voltage Vth1 (waveform 152) shifts to the high potential side. The third voltage V3 (waveform 156) changes from the low level to the high level. The fourth voltage V4 (waveform 159) starts to rise.

[0104] Timing t 32 When the second voltage V2 (waveform 154) becomes higher than the first threshold voltage Vth1 (waveform 152) at timing t, the first threshold voltage Vth1 (waveform 152) shifts (returns) to the low potential side. The third voltage V3 (waveform 156) changes from the high level to the low level. The fourth voltage V4 (waveform 159) starts to decline. The fifth voltage V5 (waveform 161) remains at the low level.

[0105] (Summary) In the detection circuit 11 of the embodiment, the threshold voltage change circuit 36 and the delay circuit 37 can be adjusted separately and independently. Also, by increasing the pulse width of the third voltage V3, the adjustment range of the time constant CR increases. That is, the detection circuit 11 of the embodiment has high design flexibility.

[0106] The detection circuit 11 of the embodiment can reliably detect open phase (see waveform 142 in FIG. 6) and momentary power failure (see waveform 153 in FIG. 7) without detecting fluctuations (see waveform 154 in FIG. 7) by adjusting the constant of the voltage division delay circuit 35 and the time constant CR.

[0107] Therefore, when fluctuations (see waveform 154 in FIG. 7) occur, 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).

[0108] (Appendix) 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.

[0109] Although some 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 implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0110] 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 division smoothing circuit 33, 38 Resistance voltage division circuit 34 First comparator 35 Voltage division delay circuit 36 Threshold voltage change circuit 37 Delay circuit 39 Second comparator Resistances 51, 52, 54, 61, 62, 71, 73, 81, 91, 92 Capacitors 53, 82 Diode 72

Claims

1. A three-phase full-wave rectifier circuit that outputs a first voltage obtained by full-wave rectifying three-phase alternating current; A voltage division delay circuit that outputs a second voltage obtained by dividing and delaying the first voltage; The second voltage is input to a first input terminal, a first threshold voltage is input to a second input terminal, and when the second voltage is lower than the first threshold voltage, a third voltage at a first level is output, and when the second voltage is higher than the first threshold voltage, the third voltage at a second level is output, a first comparator; A threshold voltage change circuit that shifts the first threshold voltage to the high 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 threshold voltage is input to a first input terminal, the fourth voltage is input to a second input terminal, and when the fourth voltage is higher than the second threshold voltage, a fifth voltage at a third level is output, and when the fourth voltage is lower than the second threshold voltage, the fifth voltage at a fourth level is output, a second comparator; comprising when fluctuations occur in the three-phase alternating current, at a first timing when the fluctuations occur, the voltage division 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 change circuit shifts the first threshold voltage to the 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 the first level to the second level, the threshold voltage change circuit shifts the first threshold voltage to the low potential side, the delay circuit starts to decrease the fourth voltage, and the second comparator maintains the fifth voltage at the fourth level; thereby not detecting the occurrence of the fluctuations; A detection circuit, characterized in that.

2. The voltage division delay circuit A first resistor having one end electrically connected to the three-phase full-wave rectifier circuit; A second resistor having one end electrically connected to the other end of the first resistor and the other end electrically connected to a reference potential; A third resistor having one end electrically connected to the other end of the first resistor and one end of the second resistor and the other end electrically connected to the first input terminal of the first comparator; A first capacitor having one end electrically connected to the other end of the third resistor and the first input terminal of the first comparator, and the other end electrically connected to a reference potential; comprising; The detection circuit according to claim 1, characterized in that.

3. The threshold voltage change circuit includes: A fourth resistor having a voltage higher than the third voltage supplied to one end and the other end electrically connected to the output terminal of the first comparator; A diode having an anode electrically connected to the other end of the fourth resistor and the output terminal of the first comparator; A fifth resistor having one end electrically connected to the cathode of the diode and the other end electrically connected to the second input terminal of the first comparator; comprising; The detection circuit according to claim 1 or 2, characterized in that.

4. The delay circuit is a low-pass filter, The detection circuit according to any one of claims 1 to 3, characterized in that.

5. The delay circuit includes: A sixth resistor having one end electrically connected to the output terminal of the first comparator and the other end electrically connected to the second input terminal of the second comparator; A second capacitor having one end electrically connected to the other end of the sixth resistor and the second input terminal of the second comparator, and the other end electrically connected to a reference potential; comprising; The detection circuit according to claim 4, characterized in that.

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