Noise filter and noise removal method

Abstract

If a fuse is applied as an overcurrent protection circuit to cut off impulse noise, and a transmission line is electrically disconnected, a problem that has existed is that the transmission line remains disconnected until a new fuse is mounted, making it difficult to operate a load continuously. A noise filter according to the present disclosure is provided with a control unit that turns off a switching element if a time equivalent to the time from detection of a first impulse noise to detection of a second impulse noise has elapsed after the second impulse noise was detected, and therefore impulse noise can be prevented from flowing to the load without hindering continuous operation of the load.

Description

[Technical field]

[0001] The present disclosure relates to filters for periodic impulse noise. [Background technology]

[0002] As a conventional technique, for example, Patent Document 1 describes a power supply circuit that performs a protective operation when impulse noise generated by a surge voltage or when an incompatible power source is supplied. In the power supply circuit of Patent Document 1, a low-pass filter, for example, including a coil and a capacitor, is inserted between the AC transmission line to be monitored by the overvoltage detection circuit and the overvoltage detection circuit, and the low-pass filter removes impulse noise. In addition, this power supply circuit includes an overcurrent protection circuit that electrically cuts off the transmission line when the overvoltage detection circuit detects an overvoltage caused by the supply of an incompatible power source. The overcurrent protection circuit is composed of a fuse that melts down due to an overcurrent flowing through the transmission line. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2012-182956 Summary of the Invention [Problem to be solved by the invention]

[0004] In the power supply circuit described in Patent Document 1, impulse noise is removed by a low-pass filter consisting of a coil and a capacitor. However, the capacitor cannot respond to rapid voltage changes, and some impulse noise may flow to the load downstream of the filter, and the coil core may become magnetically saturated, causing the countermeasure effect to be lost. In addition, if a fuse is applied as an overcurrent protection circuit to cut off the impulse noise that could not be completely removed, and the transmission line is electrically disconnected, the disconnection remains until a new fuse is installed, making it difficult to operate the load continuously. [Means for solving the problem]

[0005] The noise filter according to the present disclosure is provided in a power supply line that electrically connects a power supply and a load, When in the ON state, the power supply and the load are electrically connected, and when in the OFF state, the power supply and the load are electrically disconnected. A switching element, a sensor for detecting periodic impulse noise applied to a power line, and a detection circuit for turning off the switching element when a time corresponding to a time from when a first impulse noise is detected to when a second impulse noise is detected has elapsed from when the second impulse noise is detected. Status and Let, When a preset open time has elapsed after the time has elapsed since the second impulse noise was detected, the switching element is turned on. and a control unit. Effect of the Invention

[0006] The noise filter of the present disclosure includes a control unit that turns off the switching element when a time equivalent to the time between detecting the first impulse noise and detecting the second impulse noise has elapsed since detecting the second impulse noise.The power supply and the circuit are cut off in response to the arrival of the impulse noise without cutting off the connection between the power supply and the load by blowing a fuse, and therefore it is possible to prevent the impulse noise from flowing to the load without interrupting the continuous operation of the load. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a configuration diagram of a noise filter according to the first embodiment. [Diagram 2]Schematic diagram showing the periodicity of impulse noise [Diagram 3] 1 is a timing chart showing changes in voltage across a power line and a load before and after application of a noise filter according to the first embodiment; [Figure 4] 1 is a timing chart showing the operation of components of a noise filter and changes in voltage across a power line and a load after application of the noise filter according to the first embodiment. [Diagram 5] 1 is a flowchart showing the operation of a control unit in the first embodiment. [Figure 6] State transition diagram of the control unit in the first embodiment [Figure 7] FIG. 1 is a configuration diagram of a noise filter according to a modification of the first embodiment. [Figure 8] FIG. 11 is a diagram showing the relationship between the operation of components of a noise filter after application of a noise filter according to a modification of the first embodiment, the change in voltage applied to the power supply line and the load, and the open time of a switching element and the voltage between the power supply lines. [Figure 9] FIG. 13 is a configuration diagram of a noise filter according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Embodiment 1 FIG. 1 is a diagram showing a configuration of a noise filter 3 in the first embodiment. In the first embodiment, a case where the noise filter 3 is applied to a single-phase power line 4 will be described. As shown in FIG. 1, the noise filter 3 is provided between a power source 1 and a load 2. The power source 1 supplies power to the load 2. The load 2 is driven by the power supplied from the power source 1 through the power line 4. The load 2 is composed of one or more circuit elements. The power line 4 electrically connects the power source 1 and the load 2. The power line 4 is made up of two lines, a first power line 41 and a second power line 42. In addition, when it is not necessary to separately describe the first power line 41 and the second power line 42, they will be simply referred to as the power line 4 from here on. In the first embodiment, a case where the power line 4 becomes a propagation path of impulse noise will be described.

[0009] 1, the noise filter 3 includes a switching element 31, a sensor 32, and a control unit 33. The noise filter 3 is provided on the power line 4 to protect the load 2 from impulse noise.

[0010] The switching element 31 is provided on the power supply line 4 at a position closer to the power supply 1 than the load 2. The switching element 31 is made up of two elements: a first switching element 311 and a second switching element 312. The first switching element 311 is provided on the first power supply line 41. The second switching element 312 is provided on the second power supply line 42. Hereinafter, in explanations of the case where the first switching element 311 and the second switching element 312 perform the same operation, they will be referred to as switching element 31.

[0011] For example, if only the first switching element 311 is operated and the second switching element 312 is not operated, there is a possibility that impulse noise may propagate through the second power supply line 42. Therefore, in this embodiment, in order to prevent the propagation of impulse noise, the first switching element 311 and the second switching element 312 are operated simultaneously.

[0012] The switching element 31 switches between electrical connection and disconnection between the power source 1 and the load 2 by an on / off operation. When the switching element 31 is in an on state, it electrically connects the power source 1 and the load 2, and when the switching element 31 is in an off state, it electrically disconnects the power source 1 and the load 2. The on / off operation of the switching element 31 is controlled by a control unit 33, the details of which will be described later. The switching element 31 is, for example, a switching diode. In addition, the switching element 31 is not limited to being provided separately for the noise filter 3, and may be substituted by a switching element in a circuit of a switching power supply such as a DC-DC converter.

[0013] The sensor 32 is provided on the power line 4 at a position closer to the power source 1 than the switching element 31. The sensor 32 is, for example, a voltage sensor that measures the voltage applied to the power line 4. When the measured voltage value is equal to or greater than a predetermined value, the sensor 32 detects it as impulse noise. The impulse noise handled in this embodiment will be described with reference to FIG. 2. FIG. 2 is a schematic diagram showing the periodicity of impulse noise. FIG. 2(a) is a schematic diagram showing the aperiodicity of bursts. A burst refers to a bundle of impulse noises lasting several tens of times. As shown in FIG. 2(a), bursts arrive aperiodically.

[0014] FIG. 2(b) is a schematic diagram showing the periodicity of multiple impulse noises included in a burst. As shown in FIG. 2(b), multiple impulse noises included in one burst arrive periodically to a certain extent. In the first embodiment, such impulse noise is called periodic impulse noise. Specifically, periodic impulse noise refers to noise in which the difference in time between the arrival of the first impulse noise and the arrival of the second impulse noise is approximately equal to the difference in time between the arrival of the second impulse noise and the arrival of the third impulse noise. In other words, the differences in time at which multiple impulse noises included in a burst arrive are approximately equal to each other.

[0015] Fig. 2(c) is a schematic diagram showing the voltage waveform of one impulse noise. As shown in Fig. 2(c), impulse noise is, for example, electrical noise that is generated outside the load 2 and propagates through the power line 4, and has a voltage waveform that rises from 10% to 90% in a few nanoseconds when the maximum voltage value is 100%. The impulse noise is detected by the sensor 32, for example, during this rise time of a few nanoseconds.

[0016] The sensor 32 may be a current sensor, an electric field sensor, or a magnetic field sensor, instead of a voltage sensor. When the sensor 32 detects impulse noise, it transmits the detection result to the control unit 33. The sensor 32 transmits, for example, a sensor signal to the control unit 33 as the detection result.

[0017] As shown in FIG. 1, the control unit 33 controls the on / off operation of the switching element 31. The control unit 33 is electrically connected to the switching element 31 and the sensor 32. The control unit 33 is, for example, a board or device configured with a CPU and a memory. In this case, the control unit 33 operates by the CPU reading and executing a program stored in the memory. The control unit 33 outputs, for example, a gate signal as a signal for controlling the on / off operation of the switching element 31. The gate signal may be either a digital signal or an analog signal, and is selected according to the driving method of the switching element 31. Here, a case where the gate signal is a digital signal will be described.

[0018] Next, the operation of the noise filter 3 will be described. FIG. 3 is a timing chart showing the change in voltage applied to the power line 4 and the load 2 before the application of the noise filter 3 in the first embodiment. FIG. 3(a) shows the change in voltage applied to the power line 4 before the application of the noise filter in the first embodiment. When the periodic impulse noise propagates to the power line 4, as shown in FIG. 3(a), the voltage of the impulse noise is superimposed on the common mode voltage of the power line 4. Here, the common mode refers to a case where the reference of the voltage applied to the first power line 41 and the second power line 42 is the ground. In the first embodiment, a case where the waveforms of the voltage applied to the first power line 41 and the second power line 42 are in phase will be described. FIG. 3(a) shows that four periodic impulse noises arrive on the power line 4. The impulse noises are the first impulse noise, the second impulse noise, the third impulse noise, and the fourth impulse noise in the order of arrival. The second impulse noise is detected by the sensor 32 following the first impulse noise. Similarly, the third impulse noise is detected by the sensor 32 immediately following the second impulse noise, and the fourth impulse noise is detected by the sensor 32 immediately following the third impulse noise.

[0019] Fig. 3(b) shows a change in the voltage applied to the load 2 before application of the noise filter in the first embodiment. Fig. 3(b) illustrates an example in which the voltage of impulse noise is superimposed on the common mode voltage of the load 2. As can be seen from Fig. 3(b), if the noise filter 3 is not applied, the impulse noise propagates to the load 2.

[0020] 4 is a timing chart showing the operation of the components of the noise filter 3 and the change in voltage across the power line 4 and the load 2 after application of the noise filter 3 in the first embodiment. FIG. 4(a) shows the change in voltage across the power line 4 after application of the noise filter 3 in the first embodiment. When periodic impulse noise propagates through the power line 4, as shown in FIG. 4(a), the voltage of the impulse noise is superimposed on the common mode voltage of the power line 4. FIG. 4(a) also shows that the first to fourth impulse noises arrive at the power line 4, similar to FIG. 3(a).

[0021] Fig. 4(b) shows the operation of the sensor 32 after application of the noise filter 3 in the first embodiment. Fig. 4(b) illustrates that when the sensor 32 detects an impulse noise, it transmits a sensor signal to the control unit 33. When the sensor 32 detects a first impulse noise, it transmits a first signal to the control unit 33 as a sensor signal corresponding to the first impulse noise. Similarly, when the sensor 32 detects a second, third, or fourth impulse noise, it transmits the second, third, or fourth signal to the control unit 33 as a sensor signal.

[0022] FIG. 4(c) shows the operation of the control unit 33 after application of the noise filter 3 in the first embodiment. FIG. 4(c) illustrates that the control unit 33 transmits a gate signal to the switching element 31 in accordance with the time when the impulse noise arrives. The control unit 33 calculates time differences ΔT12, ΔT23, and ΔT34, which are the difference between the time when each impulse noise arrives, from the time when the sensor signal is received. Here, the time difference ΔT12 is the difference between the time when the first and second impulse noises arrive, which corresponds to the time from when the first impulse noise is detected to when the second impulse noise is detected. Similarly, the time difference ΔT23 is the difference between the time when the second and third impulse noises arrive, and the time difference ΔT34 is the difference between the time when the third and fourth impulse noises arrive. When the time difference ΔT12 has passed from the time when the second impulse noise arrives, the control unit 33 transmits a gate signal=1 to the switching element 31. When the gate signal=1 is received, the switching element 31 is turned off. When the switching element 31 is turned off, the power supply line 4 is electrically cut off at the location where the switching element 31 is provided, and therefore the load 2 is electrically cut off from the power supply 1.

[0023] Fig. 4(d) shows the operation of the switching element 31 after application of the noise filter 3 in embodiment 1. Fig. 4(d) shows that the switching element 31 electrically connects and disconnects the power source 1 and the load 2 in accordance with the gate signal transmitted from the control unit 33 to the switching element 31 in Fig. 4(c).

[0024] When the time difference ΔT12 has elapsed and then the open time Toff has elapsed, the control unit 33 transmits a gate signal=0 to the switching element 31. The open time Toff is the time during which the load 2 is electrically disconnected from the power source 1. The length of the open time Toff is, for example, several hundred nanoseconds. When the gate signal=0 is received, the switching element 31 is turned on. When the switching element 31 is turned on, the power line 4 is electrically connected at the location where the switching element 31 is provided, and therefore the load 2 is electrically connected to the power source 1.

[0025] The control unit 33 performs the same operation as that performed after the time difference ΔT12 has passed from the arrival time of the second impulse noise, both after the time difference ΔT23 has passed from the arrival time of the third impulse noise and after the time difference ΔT34 has passed from the arrival time of the fourth impulse noise. In this way, the control unit 33 performs the operation for each of the successive impulse noises, so that the noise filter 3 can remove the third impulse noise and subsequent impulse noises without missing any of them.

[0026] If the control unit 33 does not receive a sensor signal from the sensor 32 during the open time Toff after the time difference ΔT34 has elapsed from the time when the fourth impulse noise arrives, the control unit 33 waits for a further waiting time Twait after the open time Toff has elapsed. If the control unit 33 does not receive a sensor signal from the sensor 32 during the waiting time Twait, the control unit 33 determines that the arrival of the burst has ended and returns to a state of waiting for the reception of a sensor signal from the sensor 32. If the control unit 33 receives a sensor signal from the sensor 32 during the waiting time Twait, the control unit 33 repeats the operation in FIG. 4(c). Here, the waiting time Twait may be sufficiently longer than the open time Toff, for example, several seconds.

[0027] Fig. 4(e) shows a change in the voltage applied to the load 2 after application of the noise filter 3 in the first embodiment. Fig. 4(e) illustrates that the voltages of the third impulse noise and the fourth impulse noise are not superimposed on the common mode voltage applied to the load 2. As described above, the control unit 33 controls the on / off operation of the switching element 31 in accordance with the time when the impulse noise arrives. Then, the switching element 31 electrically cuts off the load 2 from the power source 1 in accordance with the time when the impulse noise arrives, thereby protecting the load 2 from the impulse noise.

[0028] Next, the operation of the control unit 33 for protecting the load 2 from impulse noise will be described in detail with reference to FIG. 5. FIG. 5 is a flowchart showing the operation of the control unit 33. The control unit 33 starts operating when the steady state is reached. Here, the steady state refers to a state in which the control unit 33 waits to receive a first signal from the sensor 32. It also includes a state in which the control unit 33 does not receive a sensor signal and waits to receive a first signal during a waiting time Twait described later. In step S11, the control unit 33 transmits a gate signal=0 to the switching element 31. In step S12, if the control unit 33 does not receive a first signal from the sensor 32, it waits until it receives a sensor signal from the sensor 32. In step S12, if the control unit 33 receives a first signal from the sensor 32, it proceeds to step S13. In step S13, if the control unit 33 does not receive a second signal from the sensor 32, it waits until it receives a sensor signal from the sensor 32. In step S13, if the control unit 33 receives a second signal from the sensor 32, it proceeds to step S14.

[0029] In step S14, the control unit 33 calculates the time difference ΔT12 from when the first signal is received to when the second signal is received. For example, the time difference ΔT12 can be calculated by the following formula (1), where T1 is the time when the first signal is received and T2 is the time when the second signal is received. ΔT12 = T2 - T1 (1)

[0030] Furthermore, the control unit 33 predicts the time T'3 at which the third impulse noise will arrive using the calculated time difference ΔT12. The time T'3 can be calculated using the following formula (2). Note that the predicted time at which the impulse noise will arrive is marked with "'" to distinguish it from the time at which the sensor signal is actually received. T'3 = T2 + ΔT12 (2)

[0031] In step S15, if the control unit 33 has not received a new sensor signal from the sensor 32, the process proceeds to step S16. In step S16, if the time difference ΔT12 has not elapsed since time T2, the process returns to step S15. By repeating steps S15 and S16, the control unit 33 monitors whether or not an impulse noise has arrived before the time difference ΔT12 has elapsed. In step S16, if the time difference ΔT12 has elapsed since time T2, the process proceeds to step S18.

[0032] In step S15, when a third signal is received from the sensor 32, it can be determined that the third impulse noise has arrived before the time difference ΔT12 has elapsed. In this case, the process returns to step S14, and in step S14 again, the control unit 33 calculates the time difference ΔT23 from when the second signal is received to when the third signal is received, similar to the above formula (1). Furthermore, the control unit 33 predicts the time T'4 at which the fourth impulse noise will arrive, using the calculated time difference ΔT23, similar to the above formula (2).

[0033] Here, a generalized explanation will be given of the case where the operation of step S14 is repeated. First, in step S14, where n is an integer equal to or greater than 2, the time difference ΔT(n-1)(n) from when the n-1th signal is received to when the nth signal is received is calculated. Then, the time difference ΔT(n-1)(n) is added to the time when the nth signal was received to calculate the time T'(n+1) when the n+1th impulse noise arrives.

[0034] Next, in step S15, when a sensor signal is received from the sensor 32, the process returns to step S14. Then, the control unit 33 increments the integer substituted for n by 1, and calculates the time difference ΔT(n-1)(n) from when the (n-1)th signal is received to when the nth signal is received. The control unit 33 uses the calculated time difference ΔT(n-1)(n) to predict the time T'(n+1) at which the next (n+1)th impulse noise will arrive.

[0035] In this way, if the next impulse noise arrives before the time T'(n+1) of the arrival of the n+1th impulse noise predicted in step S14, the control unit 33 receives a sensor signal corresponding to that impulse noise in step S15. In step S14 again, the control unit 33 increments the integer substituted for n by 1, and again predicts the time T'(n+1) of the arrival of the n+1th impulse noise using the time difference ΔT(n-1)(n) from when the n-1th signal is received to when the nth signal is received. Thereafter, each time returning to step 14, the control unit 33 repeats the same operation, and each time increases the integer substituted for n by 1.

[0036] Incidentally, by setting the open time Toff to an appropriate length in advance, even if the arrival of the n+1th impulse noise is slightly delayed from the predicted time T'(n+1), it is possible to prevent the n+1th impulse noise from propagating to the load 2 via the power line 4 as a propagation path. Therefore, even if the arrival of the n+1th impulse noise is slightly delayed, it is not necessary to re-predict the time T'(n+1). Also, the open time Toff is, for example, set in advance and stored in the memory of the control unit 33.

[0037] If it is determined in step S16 that the time T'(n+1) has not elapsed, the process returns to step S15. By repeating steps S15 and S16, the control unit 33 monitors whether or not impulse noise has arrived before the time T'(n+1) has elapsed. If it is determined in step S16 that the time T'(n+1) has elapsed, the process proceeds to step S17. In step S17, the control unit 33 transmits a gate signal=1 to the switching element 31. Upon receiving the gate signal 1, the switching element 31 is turned off for the opening time Toff. With the switching element 31 turned off, the load 2 is cut off from the power line 4 through which the impulse noise propagates.

[0038] In step S18, if the opening time Toff has not elapsed since the time T'(n+1) at which the (n+1)th impulse noise is predicted to arrive, the control unit 33 waits until the opening time Toff has elapsed.

[0039] In step S18, when the open time Toff has elapsed, the process proceeds to step S19.

[0040] In step S19 , the control unit 33 transmits a gate signal=0 to the switching element 31 .

[0041] In step S20, if the control unit 33 does not receive a sensor signal from the sensor 32 during the period from the time T'(n+1) at which the n+1th impulse noise is predicted to arrive until the open time Toff has elapsed, the process proceeds to step S21. In step S20, if the control unit 33 receives a sensor signal from the sensor 32 before the open time Toff has elapsed, the control unit 33 can determine that the n+1th impulse noise has arrived at the predicted time. In this case, the process returns to step S14.

[0042] In step S21, if the control unit 33 does not receive a sensor signal from the sensor 32 while the waiting time Twait has elapsed since the open time Toff, the process proceeds to step S22. In step S21, if the control unit 33 receives a sensor signal from the sensor 32 while the waiting time Twait has elapsed since the open time Toff, the process can determine that a new impulse noise has arrived before the waiting time Twait has elapsed. The new impulse noise is, for example, a delayed fifth impulse noise. In this case, the process returns to step S14. By repeating steps S21 and S22, the control unit 33 monitors whether an impulse noise has arrived before the waiting time Twait has elapsed.

[0043] In step S22, if the waiting time Twait has elapsed, the process proceeds to step S23. In step S23, the control unit 33 enters a steady state, and ends the operation for removing noise from one burst made up of periodic impulse noise.

[0044] Next, a description will be given of state transitions of the control unit 33. Fig. 6 is a state transition diagram of the control unit 33. In a state transition diagram, multiple states of the control unit 33 are written in boxes, with arrows indicating state transitions, and information that triggers the state transition is written near the arrows.

[0045] 6, the control unit 33 is in a steady state. When the control unit 33 enters the steady state, the control unit 33 transmits a gate signal=0 to the switching element 31. In the steady state, the control unit 33 waits for a sensor signal from the sensor 32. When the control unit 33 receives a first signal from the sensor 32, the control unit 33 transitions to state 2. At this time, the control unit 33 records the time T1 at which the first signal was received, for example, in a memory. 4, the control unit 33 waits for a second signal. When the control unit 33 receives the second signal from the sensor 32, the control unit 33 transitions to state 3.

[0046] In state 3, when the control unit 33 receives the first signal and the second signal from the sensor 32, the control unit 33 calculates the time difference ΔT12 from when the first signal is received to when the second signal is received. The control unit 33 adds this time difference ΔT12 to the time T2 when the second signal is received to calculate time T'3. Time T'3 is the time when the third impulse noise is predicted to arrive. After calculating time T'3, the control unit 33 transitions to state 4.

[0047] In State 4, the control unit 33 waits until the predicted time T'3 arrives. If the control unit 33 receives a third signal from the sensor 32 before the predicted time T'3 arrives, the control unit 33 transitions to State 3.

[0048] When transitioning from state 4 to state 3, the control unit 33 calculates the time difference ΔT23 between when the second signal is received and when the third signal is received. The control unit 33 adds the time difference ΔT23 to the time T3 when the third signal is received to calculate time T'4, and transitions to state 4 again. Time T'4 is the time when the fourth impulse noise is predicted to arrive. In state 4 again, the control unit 33 waits until time T'4. If the control unit 33 receives a sensor signal before time T'4, it transitions to state 3 again.

[0049] The transition between state 3 and state 4 will be described in general terms. First, in state 3, the time difference ΔT(n-1)(n) is calculated, and the time T'(n+1) at which the n+1th impulse noise is expected to arrive is calculated using this. Here, n is an integer of 2 or more. If the state transitions to state 4 and a sensor signal is received before the expected arrival time T'(n+1), the state transitions to state 3. Then, the control unit 33 increments the integer substituted for n by 1, and calculates the time difference ΔT(n-1)(n) from when the n-1th signal is received to when the nth signal is received. The control unit 33 adds the time difference ΔT(n-1)(n) to the time T(n) to recalculate the time T'(n+1) at which the n+1th impulse noise is expected to arrive. Thereafter, every time the state transitions to state 3, the control unit 33 repeats the same operation, and increments the integer substituted for n by 1 each time. If no sensor signal is received from the sensor 32 while waiting until time T'(n+1), and time T'(n+1) arrives, the control unit 33 outputs a gate signal=1 to transition to state 5. Receiving a gate signal=1 causes the switching element 31 to enter the off state. Note that the operation when transitioning from state 5 to state 3 and the operation when transitioning from state 6 to state 3 are similar to the operation when transitioning from state 4 to state 3.

[0050] In state 5, the control unit 33 waits for a sensor signal from the sensor 32 until the release time Toff has elapsed from the time T'(n+1) at which the (n+1)th impulse noise is predicted to arrive.

[0051] If a sensor signal is received between time T'(n+1) and the elapse of the open time Toff, the control unit 33 outputs a gate signal = 0 after the open time Toff has elapsed, and transitions to state 3. In state 3, the control unit 33 increments the integer substituted for n by 1, calculates the time difference ΔT(n-1)(n) from when the n-1th signal is received to when the nth signal is received, and uses this to further calculate the time T'(n+1) when the next n+1th signal arrives.

[0052] If no sensor signal is received from time T'(n+1) until the open time Toff has elapsed, the control unit 33 outputs a gate signal=0 after the open time Toff has elapsed, and transitions to state 6.

[0053] In state 6, the control unit 33 waits to receive a sensor signal until the release time Toff has elapsed and the waiting time Twait has elapsed. If a sensor signal is received before the waiting time Twait has elapsed, the control unit 33 transitions to state 3. In state 3, the control unit 33 increments the integer substituted for n by 1, and predicts the time T'(n+1) at which the n+1th signal will arrive from the difference in the reception time between the n-1th signal and the nth signal. If a sensor signal is not received during the waiting time Twait, the control unit 33 transitions to state 1 and returns to the steady state. The operation of the control unit 33 in state 1 is the same as that described above.

[0054] The noise filter 3 of the first embodiment includes a control unit 33 that causes the sensor 32 to detect periodic impulse noise applied to the power line 4 and transmits a sensor signal to the control unit 33, and turns off the switching element 31 when a time equivalent to the time from when the first impulse noise is detected to when the second impulse noise is detected has elapsed since the detection of the second impulse noise, thereby electrically cutting off the power source 1 and the load 2 in response to the arrival of the impulse noise. Therefore, the noise filter 3 of the first embodiment can prevent the impulse noise from flowing to the load 2 without interfering with the continuous operation of the load 2.

[0055] In the first embodiment, the case where the power supply line 4 has two wires has been described, but the power supply line 4 may have three or more wires. In this case, since a switching element 31 may be provided for each power supply line 4, the number of switching elements 31 corresponding to the number of power supply lines 4 may be prepared.

[0056] In the first embodiment, the sensor 32 is provided on the power supply line 41 and the power supply line 42. However, the sensor 32 may be located anywhere as long as it can detect the impulse noise applied to the power supply line 4. For example, the sensor 32 may be connected in series to a capacitor that has the function of removing impulse noise. An example of such a capacitor is a Y capacitor connected between the power supply line and the ground.

[0057] As a modification, the noise filter 3 may include a power supply circuit 5 that supplies power to the load 2 when the load 2 is electrically disconnected from the power source 1. Here, it is assumed that the load 2 is a circuit such as a precision instrument that cannot operate if it is electrically disconnected for even a few ns. In this case, the load 2 operates when a normal mode voltage is applied. If the load 2 is electrically disconnected from the power source 1 even during the open time Toff, that is, if the normal mode voltage applied to the load 2 falls below a certain value, the load 2 cannot continue to operate. Here, the normal mode voltage refers to the voltage between the first power line 41 and the second power line 42.

[0058] Fig. 7 is a configuration diagram of a noise filter in a modification of the first embodiment. As shown in Fig. 7, the power supply circuit 5 is provided in the power line 4 between the switching element 31 and the load 2. The power supply circuit 5 supplies power to the load 2 when the switching element 31 is in an off state. The power supply circuit 5 is, for example, a capacitor. There is no limit to the number of capacitors used as the power supply circuit 5. The power supply circuit 5 may also use a capacitor provided for the purpose of dealing with momentary power outages and smoothing current.

[0059] When a capacitor is used as the power supply circuit 5, a voltage drop occurs in the power supplied to the load 2 depending on the capacitance value of the capacitor and the power consumption of the load 2. Therefore, the capacitance value of the capacitor required to continue the operation of the load 2 is calculated from the power consumption of the load 2 and the length of the open time Toff during which the switching element 31 is in the off state.

[0060] Fig. 8 shows the operation of the components of the noise filter 3 after application of the noise filter 3, changes in voltage applied to the power line and load, and the relationship between the open time Toff of the switching element 31 and the power line voltage Vn, which is the voltage applied between the first power line 41 and the second power line 42. (a) to (e) at the top of Fig. 8 are the same as (a) to (e) in Fig. 4. (f) of Fig. 8 shows changes in the normal mode voltage applied to the load 2 after application of the noise filter 3 in the modified example. The normal mode voltage changes during the time when the switching element 31 electrically connects and disconnects the power source 1 and the load 2.

[0061] When the switching element 31 is turned off, the power supply from the power source 1 to the load 2 is cut off. Therefore, power is supplied to the load 2 from the capacitor used as the power supply circuit 5. In this case, as shown in FIG. 8(g), the power line voltage Vn decreases over time as the capacitor discharges. Therefore, in order to continue the operation of the load 2, a capacitor with a sufficient capacity calculated from the power consumption of the load 2 and the length of the open time Toff during which the switching element 31 is turned off should be selected.

[0062] If the power supply 1 is on the upstream side and the load 2 is on the downstream side, then the power supply 1, sensor 32, control unit 33, switching element 31, power supply circuit 5, and load 2 may be electrically connected in this order from the upstream side. Other circuits or elements such as a diode bridge, a DC-DC converter, other filters, or input / output protection circuits may be disposed between the respective circuits or elements.

[0063] According to the modified example, the noise filter 3 of the present application is provided with a power supply circuit 5 that supplies power to the load 2 when the load 2 is electrically disconnected from the power source 1. Therefore, even if the load 2 is a circuit mounted on a precision instrument that cannot operate if it is electrically disconnected for even a few nanoseconds, it is possible to continuously operate the load 2.

[0064] Embodiment 2 In the first embodiment, a case where the switching elements 31 are required for the number of power lines 4 has been described. In the present embodiment, a case where the power line 4 has three or more lines and a diode bridge 6 is provided on the power line 4 between the power source 1 and the switching element 31 will be described. By arranging the switching element 31 downstream of the diode bridge 6, even if the power line 4 has three or more lines, it can be configured with two switching elements. Note that the noise filter 3 of the second embodiment has most of the same parts as the noise filter 3 of the first embodiment or its modified example. Therefore, in the following, the differences from the noise filter 3 of the first embodiment or its modified example will be mainly described, and the description of the configuration and the like common to the noise filter 3 of the first embodiment or its modified example will be omitted as appropriate.

[0065] FIG. 9 shows a configuration diagram of the noise filter 3 in the second embodiment. In the second embodiment, an example will be described in which the power line 4 is for three-phase AC and the current flowing through the power line 4 is rectified by the diode bridge 6. The power line 4 is made up of a first power line 401, a second power line 402, and a third power line 403, which are provided at a position closer to the power source 1 than the diode bridge 6. The power line 7, which is provided at a position closer to the load 2 than the diode bridge 6, is made up of a first power line 701 and a second power line 702. The first power line 401, the second power line 402, and the third power line 403 electrically connect the power source 1 and the diode bridge 6. The first power line 701 and the second power line 702 electrically connect the diode bridge 6 and the load 2. In addition, when it is not necessary to separately describe the first power line 701 and the second power line 702, they will be simply referred to as the power line 7 from here on. The diode bridge 6 rectifies the three-phase AC supplied from the power source 1 into DC and outputs it. Therefore, the diode bridge 6 has a three-wire input and a two-wire output.

[0066] The configuration described in the second embodiment is similar to that of the first embodiment, except that the power supply line 4 is for three-phase AC and a diode bridge 6 is provided. That is, the configuration is similar to that of the first embodiment, including a power supply 1 that supplies power to a load 2, a load 2 that receives power from the power supply 1 via a power supply line 4 and is driven by the supplied power, and a noise filter 3 provided on the power supply line 4 to protect the load 2 from impulse noise.

[0067] The noise filter 3 has the same configuration as in the first embodiment, including a switching element 31, a sensor 32, and a control unit 33. The switching element 31 also has the same configuration as in the first embodiment, including a first switching element 311 and a second switching element 312. As shown in FIG. 9, the first switching element 311 is provided on a first power supply line 701. The second switching element 312 is provided on a second power supply line 702.

[0068] Next, the operation of the noise filter 3 will be described. The sensor 32 detects impulse noise propagating through the first power line 401, the second power line 402, and the third power line 403, and transmits a sensor signal to the control unit 33. Upon receiving the sensor signal from the sensor 32, the control unit 33 controls the on / off operation of the switching element 31. The operation performed by the control unit 33 is the same as that of the first embodiment. The switching element 31 prevents the impulse noise from propagating to the load 2 by performing the on / off operation.

[0069] According to the second embodiment, since the diode bridge 6 that rectifies three-phase AC to DC and outputs it is provided, the input from the three-wire power supply line 4 is output via two wires of the power supply line 7. Therefore, the noise filter 3 can be configured with the same number of switching elements 31 as the number of the power supply lines 7, which is fewer than the number of the power supply lines 4.

[0070] In the second embodiment, the noise filter 3 is used in a three-phase three-wire power supply, but the present invention is not limited to this. For example, even if the noise filter is used in a three-phase four-wire power supply, the noise filter can be configured with fewer switching elements than the number of power supply lines. [Explanation of symbols]

[0071] REFERENCE SIGNS LIST 1 power supply, 2 load, 3 noise filter, 4 power supply line, 5 power supply circuit, 6 diode bridge, 7 power supply line, 31 switching element, 32 sensor, 33 control unit, 41 first power supply line, 42 second power supply line, 311 first switching element, 312 second switching element, 401 first power supply line, 402 second power supply line, 403 third power supply line, 701 first power supply line, 702 second power supply line

Claims

1. a switching element that is provided in a power supply line that electrically connects a power supply and a load, electrically connecting the power supply and the load when in an on state and electrically disconnecting the power supply and the load when in an off state; a sensor for detecting periodic impulse noise applied to the power line; a control unit that turns the switching element off when a time corresponding to a time from detecting a first impulse noise to detecting a second impulse noise has elapsed since detecting the second impulse noise, and turns the switching element on when a preset open time has elapsed after the time has elapsed since detecting the second impulse noise; A noise filter equipped with

2. A power supply line is provided between the switching element and the load. A power supply circuit is provided to supply power to the load when the switching element is off.

2. The noise filter according to claim 1.

3. The sensor detects the second impulse noise subsequent to the first impulse noise.

2. The noise filter according to claim 1.

4. The switching element is a switching diode.

2. The noise filter according to claim 1.

5. The sensor is a voltage sensor or a current sensor.

2. The noise filter according to claim 1.

6. The power supply circuit is a capacitor. The noise filter according to claim 2.

7. When the sensor detects the first impulse noise, the sensor transmits a first signal corresponding to the first impulse noise to the control unit, and when the sensor detects the second impulse noise, the sensor transmits a second signal corresponding to the second impulse noise to the control unit; The control unit controls the switching element to be in an OFF state at a time when a difference between a time when the first signal and a time when the second signal are received has elapsed from a time when the second signal is received, and controls the switching element to be in an ON state when the opening time has elapsed after the time has elapsed.

2. The noise filter according to claim 1.

8. The power supply further includes a diode bridge that is provided on the power supply line between the power supply and the switching element and that rectifies the three-phase AC supplied from the power supply into a DC current and outputs the DC current.

2. The noise filter according to claim 1.

9. detecting, by a sensor, periodic impulse noise applied to a power line electrically connecting a power supply and a load; When the sensor detects a first impulse noise, the sensor transmits a first signal corresponding to the first impulse noise to a control unit; When the sensor detects a second impulse noise, the sensor transmits a second signal corresponding to the second impulse noise to the controller; a step of the control unit calculating a time difference between when the first signal is received and when the second signal is received; determining whether the time difference has elapsed since the control unit received the second signal; a step in which, when the time difference has elapsed since receiving the second signal, the control unit controls a switching element, which electrically connects the power source and the load when in an on state and electrically disconnects the power source and the load when in an off state, to an off state; When a preset open time has elapsed after the time difference has elapsed since the detection of the second impulse noise, the control unit controls the switching element to be in an on state; A noise removal method comprising:

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