Noise filter and noise removal method

Abstract

When a fuse is used as an overcurrent protection circuit and a transmission line is electrically cut off in order to cut off impulse noise, the line is still broken before a new fuse is assembled, and a load is difficult to continuously operate. The noise filter according to the present disclosure has a control unit that turns off a switching element when a time corresponding to the time from the detection of a first pulse noise to the detection of a second pulse noise has elapsed since the detection of a second pulse noise, and thus can prevent the pulse noise from flowing to a load without hindering the continuous operation of the load.

Description

Technical Field

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

[0002] As a prior art, for example, Patent Document 1 describes a power supply circuit that performs a protective action when supplied with pulse noise or an incompatible power supply due to a surge voltage. In the power supply circuit of Patent Document 1, a low-pass filter such as a coil and a capacitor is inserted between the transmission line of the alternating current that is the monitoring object of the overvoltage detection circuit and the overvoltage detection circuit, and the pulse noise is removed by the low-pass filter. In addition, the power supply circuit has an overcurrent protection circuit that electrically cuts off the transmission line when the overvoltage detection circuit detects an overvoltage when an incompatible power supply is supplied. The overcurrent protection circuit is composed of a fuse that is blown by an overcurrent flowing through the transmission line.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-182956 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the power supply circuit described in Patent Document 1, pulse noise is removed by a low-pass filter composed of a coil and a capacitor. However, the capacitor cannot cope with rapid voltage changes, and part of the pulse noise may flow to the load at the subsequent stage of the filter, and the core of the coil may lose the countermeasure effect due to magnetic saturation. In addition, there is the following problem: if a fuse is applied as an overcurrent protection circuit to cut off the pulse noise that has not been completely removed and the transmission line is electrically cut off, it is difficult to keep the load operating because the line is still broken before a new fuse is installed.

[0008] Means for solving problems

[0009] The noise filter disclosed in the present invention comprises: a switch element, which is provided in a power line that electrically connects a power supply and a load, and switches the electrical connection or disconnection between the power supply and the load by an on-off action; a sensor, which detects periodic pulse noise applied to the power line; and a control unit, which turns off the switch element when a time equivalent to the time from the detection of the first pulse noise to the detection of the second pulse noise has passed since the detection of the second pulse noise.

[0010] Effects of the Invention

[0011] The noise filter disclosed in the present invention has a control unit that turns off the switch element when a time equivalent to the time from the detection of the first pulse noise to the detection of the second pulse noise has passed since the second pulse noise was detected. The power supply and the load are not cut off by blowing the fuse, but the power supply and the circuit are cut off in response to the arrival of the pulse noise. Therefore, it is possible to prevent the pulse noise from flowing to the load without hindering the continuous operation of the load. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a diagram showing the structure of the noise filter in the first embodiment.

[0013] Figure 2 is a schematic diagram showing the periodicity of impulse noise.

[0014] Figure 3 1 is a timing chart showing changes in voltage applied to a power supply line and a load before the noise filter in the first embodiment is applied.

[0015] Figure 4 This is a timing chart showing the operation of the components of the noise filter after the noise filter in the first embodiment is applied and the change of the voltage applied to the power line and the load.

[0016] Figure 5 This is a flowchart showing the operation of the control unit in the first embodiment.

[0017] Figure 6 This is a state transition diagram of the control unit in the first embodiment.

[0018] Figure 7 This is a diagram showing the configuration of a noise filter in a modified example of the first embodiment.

[0019] Figure 8 This is a diagram showing the relationship between the operation of the components of the noise filter after the noise filter in the modification of the first embodiment is applied, the change in the voltage applied to the power line and the load, and the open time of the switching element and the voltage between the power lines.

[0020] Fig. 9 This is a diagram showing the structure of a noise filter in the second embodiment. DETAILED DESCRIPTION

[0021] Implementation Method 1

[0022] Figure 1 1 is a diagram showing the structure of the noise filter 3 in the first embodiment. In the first embodiment, the case where the noise filter 3 is applied to the single-phase power supply line 4 is described. Figure 1As shown, the noise filter 3 is provided between the power supply 1 and the load 2. The power supply 1 supplies electric power to the load 2. Electric power is supplied from the power supply 1 to the load 2 via the power supply line 4, and the load 2 is driven by the supplied electric power. The load 2 is composed of one or more circuit elements. The power supply line 4 electrically connects the power supply 1 and the load 2. The power supply line 4 is composed of two lines, namely, a first power supply line 41 and a second power supply line 42. In addition, when it is not necessary to separately describe the first power supply line 41 and the second power supply line 42, they are only described as the power supply line 4 hereinafter. In the first embodiment, the case where the power supply line 4 becomes a propagation path of the impulse noise is described.

[0023] like Figure 1 As shown, the noise filter 3 includes a switch 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 the influence of the pulse noise.

[0024] The switch element 31 is provided in the power line 4 at a position closer to the power source 1 than the load 2. The switch element 31 is composed of two switch elements, namely, a first switch element 311 and a second switch element 312. The first switch element 311 is provided in the first power line 41. The second switch element 312 is provided in the second power line 42. Hereinafter, the description of the case where the first switch element 311 and the second switch element 312 perform the same operation is described as the switch element 31.

[0025] For example, when only the first switching element 311 is operated and the second switching element 312 is not operated, pulse noise may propagate through the second power supply line 42. Therefore, in order to prevent the propagation of pulse noise, in this embodiment, the first switching element 311 and the second switching element 312 are operated simultaneously.

[0026] The switch element 31 switches the electrical connection or disconnection between the power supply 1 and the load 2 by turning on and off. The switch element 31 electrically connects the power supply 1 and the load 2 when it is in the on state, and electrically disconnects the power supply 1 and the load 2 when it is in the off state. The details of the switch element 31 will be described later, but the on and off actions are controlled by the control unit 33. The switch element 31 is, for example, a switching diode. In addition, the switch element 31 is not limited to being additionally provided for the noise filter 3, and a switch element in a circuit of a switching power supply such as a DC-DC converter may be used instead.

[0027] The sensor 32 is provided in 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 value of the voltage is greater than a predetermined value, the sensor 32 detects it as a pulse noise. Figure 2 The impulse noise handled in this embodiment will be described. Figure 2is a schematic diagram showing the periodicity of impulse noise. Figure 2 (a) is a schematic diagram showing the non-periodicity of a burst. A burst is a bundle of pulse noises of about dozens of times. Figure 2 As shown in (a), the pulse train arrives non-periodically.

[0028] Figure 2 (b) is a schematic diagram showing the periodicity of multiple pulse noises contained in a pulse train. Figure 2 As shown in (b), a plurality of pulse noises contained in a certain pulse train arrives periodically to a certain extent. In the first embodiment, such pulse noise is referred to as periodic pulse noise. Specifically, periodic pulse noise refers to a pulse noise in which the time difference from the arrival of the first pulse noise to the arrival of the second pulse noise is approximately equal to the time difference from the arrival of the second pulse noise to the arrival of the third pulse noise. That is, the time differences of the arrival of the plurality of pulse noises contained in the pulse train are approximately equal.

[0029] Figure 2 (c) is a schematic diagram showing a voltage waveform of a pulse noise. Figure 2 As shown in (c), the pulse noise is, for example, electrical noise generated outside the load 2 and propagated in the power supply line 4, and has a voltage waveform that rises from 10% to 90% in a few ns when the maximum voltage is 100%. The pulse noise is detected by the sensor 32, for example, within the rise time of a few ns.

[0030] In addition, the sensor 32 may be not only a voltage sensor but also a current sensor, an electric field sensor, or a magnetic field sensor. When the sensor 32 detects the pulse noise, it sends the detection result to the control unit 33. For example, the sensor 32 sends the sensor signal as the detection result to the control unit 33.

[0031] like Figure 1 As shown, the control unit 33 controls the on-off action of the switch element 31. The control unit 33 is electrically connected to the switch element 31 and the sensor 32. The control unit 33 is, for example, a substrate or device composed of a CPU and a memory. In this case, the CPU reads out and executes the program stored in the memory, whereby the control unit 33 operates. The control unit 33 outputs, for example, a selection signal as a signal for controlling the on-off action of the switch element 31. The selection signal can be either a digital signal or an analog signal, and is selected according to the driving method of the switch element 31. Here, the case where the selection signal is a digital signal is described.

[0032] Next, the operation of the noise filter 3 will be described. Figure 31 is a timing chart showing changes in voltage applied to power line 4 and load 2 before noise filter 3 in Embodiment 1 is applied. Figure 3 (a) shows the change of the voltage applied to the power line 4 before the noise filter in Embodiment 1 is applied. When periodic pulse noise propagates to the power line 4, as shown in FIG. Figure 3 As shown in (a), the voltage of pulse noise is superimposed on the common mode voltage of the power line 4. Here, the common mode refers to the case where the reference of the voltage applied to the first power line 41 and the second power line 42 is grounded. In the first embodiment, the case where the waveforms of the voltages applied to the first power line 41 and the second power line 42 are in the same phase is described. Figure 3 In (a), four periodic pulse noises are shown arriving at the power line 4. The pulse noises are set as the first pulse noise, the second pulse noise, the third pulse noise, and the fourth pulse noise in the order of arrival. The second pulse noise is detected continuously by the sensor 32 with the first pulse noise. Similarly, the third pulse noise is detected continuously by the sensor 32 with the second pulse noise, and the fourth pulse noise is detected continuously by the sensor 32 with the third pulse noise.

[0033] Figure 3 (b) shows the change of the voltage applied to the load 2 before the noise filter in Embodiment 1 is applied. Figure 3 (b) of FIG. 1 shows an example in which the voltage of the pulse noise is superimposed on the common mode voltage of the load 2. Figure 3 As can be seen from (b), when the noise filter 3 is not applied, the pulse noise propagates to the load 2.

[0034] Figure 4 This is a timing chart showing the operation of the components of the noise filter 3 and the change of the voltage applied to the power line 4 and the load 2 after the noise filter 3 in the first embodiment is applied. Figure 4 (a) shows the change of the voltage applied to the power line 4 after the noise filter 3 in the first embodiment is applied. When periodic pulse noise propagates to the power line 4, as shown in FIG. Figure 4 As shown in (a), the voltage of the pulse noise is superimposed on the common mode voltage of the power supply line 4. Figure 4 In (a), it is also related to Figure 3 (a) similarly shows that the first to fourth pulse noises reach the power supply line 4 .

[0035] Figure 4 (b) shows the operation of the sensor 32 after the noise filter 3 in the first embodiment is applied. Figure 4In (b), it is illustrated that when the sensor 32 detects impulse noise, the sensor signal is sent to the control unit 33. When the sensor 32 detects the first impulse noise, the first signal is sent to the control unit 33 as a sensor signal corresponding to the first impulse noise. Similarly, when the sensor 32 detects the second, third, and fourth impulse noises, the second, third, and fourth signals are sent to the control unit 33 as sensor signals.

[0036] Figure 4 (c) shows the operation of the control unit 33 after the noise filter 3 in the first embodiment is applied. Figure 4 In (c), the control unit 33 is shown to send a gating signal to the switch element 31 according to the time when the pulse noise arrives. The control unit 33 calculates the difference in the time of arrival of each pulse noise, that is, the time difference ΔT12, ΔT23, and ΔT34 according to the time when the sensor signal is received. Here, the time difference ΔT12 is the difference in the time of arrival of the first and second pulse noises, which is equivalent to the time from the detection of the first pulse noise to the detection of the second pulse noise. Similarly, the time difference ΔT23 is the difference in the time of arrival of the second and third pulse noises, and the time difference ΔT34 is the difference in the time of arrival of the third and fourth pulse noises. When the time difference ΔT12 has passed since the arrival of the second pulse noise, the control unit 33 sends a gating signal = 1 to the switch element 31. When the gating signal = 1 is received, the switch element 31 becomes an off state. When the switch element 31 becomes an off state, the power line 4 becomes an electrically disconnected state at the location where the switch element 31 is provided, and therefore, the load 2 is electrically disconnected from the power supply 1.

[0037] Figure 4 (d) shows the operation of the switching element 31 after the noise filter 3 in the first embodiment is applied. Figure 4 In (d), the switch element 31 is shown according to Figure 4 In (c), the selection signal sent from the control unit 33 to the switching element 31 performs electrical connection and disconnection between the power supply 1 and the load 2.

[0038] When the open time Toff further passes after the time difference ΔT12, the control unit 33 sends a gate signal = 0 to the switch element 31. The open time Toff refers to the time for electrically disconnecting the load 2 from the power supply 1. The length of the open time Toff is, for example, several hundred nanoseconds. When the gate signal = 0 is received, the switch element 31 is turned on. When the switch element 31 is turned on, the power line 4 is electrically connected to the portion where the switch element 31 is provided, and thus the load 2 is electrically connected to the power supply 1.

[0039] The control unit 33 also performs the same operation as after the time difference ΔT12 has passed since the arrival of the second pulse noise after the time difference ΔT23 has passed since the arrival of the third pulse noise and after the time difference ΔT34 has passed since the arrival of the fourth pulse noise. In this way, the control unit 33 operates on the continuous pulse noises respectively, so the noise filter 3 can remove the pulse noises after the third pulse noise without omission.

[0040] 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 passed since the arrival of the fourth pulse noise, the control unit 33 further waits for a standby time Twait after the open time Toff has passed. If the control unit 33 does not receive a sensor signal from the sensor 32 during the standby time Twait, the control unit 33 determines that the arrival of the pulse train has ended and returns to the state of waiting for the sensor signal from the sensor 32. If the control unit 33 receives a sensor signal from the sensor 32 during the standby time Twait, the control unit 33 repeats the state. Figure 4 Here, the waiting time Twait may be a time sufficiently longer than the open time Toff, for example, several seconds.

[0041] Figure 4 (e) shows the change in voltage applied to the load 2 after the noise filter 3 in the first embodiment is applied. Figure 4 (e) of FIG. 1 shows a voltage without overlapping the third pulse noise and the fourth pulse noise in the common mode voltage applied to the load 2. As described above, the control unit 33 controls the on-off operation of the switch element 31 according to the arrival time of the pulse noise. Moreover, the switch element 31 electrically disconnects the load 2 from the power supply 1 according to the arrival time of the pulse noise, thereby protecting the load 2 from the influence of the pulse noise.

[0042] Next, refer to Figure 5 The operation of the control unit 33 for protecting the load 2 from the influence of the impulse noise will be described in detail. Figure 5: is a flowchart showing the operation of the control unit 33. The control unit 33 starts to operate after becoming a stable state. Here, the stable state refers to a state in which the control unit 33 waits to receive the first signal from the sensor 32. In addition, it includes a state in which the control unit 33 does not receive a sensor signal but waits to receive the first signal within the waiting time Twait described later. In step S11, the control unit 33 sends a selection signal = 0 to the switch element 31. In step S12, the control unit 33 waits until the sensor signal is received from the sensor 32 when the first signal is not received from the sensor 32. When the control unit 33 receives the first signal from the sensor 32 in step S12, the process proceeds to step S13. In step S13, the control unit 33 waits until the sensor signal is received from the sensor 32 when the second signal is not received from the sensor 32. When the control unit 33 receives the second signal from the sensor 32 in step S13, the process proceeds to step S14.

[0043] 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, when the time when the first signal is received is T1 and the time when the second signal is received is T2, the time difference ΔT12 can be obtained by the following formula (1).

[0044] ΔT12=T2-T1…(1)

[0045] The control unit 33 uses the calculated time difference ΔT12 to predict the time T'3 when the third pulse noise arrives. The time T'3 can be calculated by the following equation (2). The time predicted to be the time of the pulse noise arrival is marked with "'" to distinguish it from the time when the sensor signal is actually received.

[0046] T'3=T2+ΔT12…(2)

[0047] If the control unit 33 does not receive a new sensor signal from the sensor 32 in step S15, the process proceeds to step S16. If the time difference ΔT12 has not passed since time T2 in step S16, the process returns to step S15. By repeating steps S15 and S16, the control unit 33 monitors whether the impulse noise arrives during the period until the time difference ΔT12 passes. If the time difference ΔT12 has passed since time T2 in step S16, the process proceeds to step S18.

[0048] In step S15, when the third signal is received from the sensor 32, it can be determined that the third pulse noise arrives within the period until the time difference ΔT12 has passed. In this case, the process returns to step S14, and in the next step S14, the control unit 33 calculates the time difference ΔT23 from the reception of the second signal to the reception of the third signal, as in the above equation (1). In addition, as in the above equation (2), the control unit 33 uses the calculated time difference ΔT23 to predict the time T'4 when the fourth pulse noise arrives.

[0049] Here, the case of repeating the operation of step S14 is generalized for explanation. First, in step S14, when n is an integer greater than 2, the time difference ΔT(n-1)(n) from the reception of the n-1th signal to the reception of the nth signal is calculated. Then, the time difference ΔT(n-1)(n) is added to the time when the nth signal is received, thereby calculating the time T'(n+1) when the n+1th impulse noise arrives.

[0050] Next, when a sensor signal is received from the sensor 32 in step S15, the process returns to step S14. Then, the control unit 33 increases the integer substituted into 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 uses the calculated time difference ΔT(n-1)(n) to predict the time T'(n+1) when the next n+1th impulse noise arrives.

[0051] In this way, when the next pulse noise arrives before the arrival time T'(n+1) of the n+1th pulse noise predicted in step S14, in step S15, the control unit 33 receives the sensor signal corresponding to the pulse noise. In the next step S14, the control unit 33 increases the integer substituted into n by 1, and then re-predicts the arrival time T'(n+1) of the n+1th pulse noise using the time difference ΔT(n-1)(n) from the reception of the n-1th signal to the reception of the nth signal. Thereafter, each time the control unit 33 returns to step 14, the control unit 33 repeats the same operation, increasing the integer substituted into n by 1 each time.

[0052] In addition, by setting the open time Toff to an appropriate length in advance, even if the arrival of the n+1th pulse noise is slightly delayed compared to the predicted time T'(n+1), it is possible to prevent the n+1th pulse noise from propagating to the load 2 using the power line 4 as a propagation path. Thus, even if the arrival of the n+1th pulse noise is slightly delayed, there is no need to re-predict the time T'(n+1). In addition, the open time Toff is set in advance and stored in the memory of the control unit 33, for example.

[0053] If the time T'(n+1) has not passed in step S16, the process returns to step S15. By repeating steps S15 and S16, the control unit 33 monitors whether the pulse noise has arrived during the period until the time T'(n+1) has passed. If the time T'(n+1) has passed in step S16, the process proceeds to step S17. In step S17, the control unit 33 sends a strobe signal = 1 to the switch element 31. When the switch element 31 receives the strobe signal 1, it becomes an OFF state within the open time Toff. The switch element 31 becomes an OFF state, thereby disconnecting the load 2 from the power line 4 that propagates the pulse noise.

[0054] In step S18 , if the open time Toff has not elapsed from the time T′(n+1) when the n+1-th impulse noise is predicted to arrive, the control unit 33 waits until the open time Toff elapses.

[0055] When the open time Toff has elapsed in step S18, the process proceeds to step S19.

[0056] In step S19 , the control section 33 sends a gate signal=0 to the switch element 31 .

[0057] 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 pulse noise is predicted to arrive to the open time Toff, the process proceeds to step S21. In step S20, if the control unit 33 receives a sensor signal from the sensor 32 during the period from the open time Toff, the process can determine that the n+1th pulse noise arrives at the predicted time. In this case, the process returns to step S14.

[0058] In step S21, if the control unit 33 does not receive a sensor signal from the sensor 32 during the waiting time Twait from the opening time Toff, the process proceeds to step S22. In step S21, if the control unit 33 receives a sensor signal from the sensor 32 during the waiting time Twait from the opening time Toff, it can be determined that a new pulse noise arrives during the waiting time Twait. The new pulse noise is, for example, the delayed fifth pulse noise. In this case, the process returns to step S14. By repeating steps S21 and S22, the control unit 33 monitors whether the pulse noise arrives during the waiting time Twait.

[0059] When the waiting time Twait has elapsed in step S22, the process proceeds to step S23. In step S23, the control unit 33 enters a stable state and ends the noise removal operation for one pulse train composed of periodic pulse noise.

[0060] Next, the state transition of the control unit 33 will be described. Figure 6 This is a state transition diagram of the control unit 33. The state transition diagram is a diagram in which a plurality of states of the control unit 33 are respectively described in quadrilaterals, state transitions are indicated by arrows, and information that triggers state transitions is described near the arrows.

[0061] exist Figure 6 In state 1, the control unit 33 is in a stable state. When the control unit 33 becomes a stable state, the control unit 33 sends a selection signal = 0 to the switch element 31. In the stable state, the control unit 33 waits for a sensor signal from the sensor 32. When the control unit 33 receives the first signal from the sensor 32, it changes to state 2. At this time, the control unit 33 records the time T1 when the first signal is received in a memory, for example.

[0062] exist Figure 4 In the state 2, the control unit 33 is in a state of waiting for the second signal. When the control unit 33 receives the second signal from the sensor 32, it changes to the state 3.

[0063] In state 3, when the first signal and the second signal are received from the sensor 32, the control unit 33 calculates the time difference ΔT12 from the reception of the first signal to the reception of the second signal. The control unit 33 adds the time difference ΔT12 to the time T2 when the second signal is received to calculate the time T'3. The time T'3 is the time when the third impulse noise is predicted to arrive. Then, when the control unit 33 calculates the time T'3, it changes to state 4.

[0064] In the state 4 , the control unit 33 waits until the predicted time T′3 arrives. If the third signal is received from the sensor 32 before the predicted time T′3 arrives, the control unit 33 shifts to the state 3 .

[0065] When changing from state 4 to state 3, the control unit 33 calculates the time difference ΔT23 from when the second signal is received to 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, calculates the time T'4, and changes to state 4 again. The time T'4 is the time when the fourth impulse noise is predicted to arrive. In the state 4 again, the control unit 33 waits until the time T'4 comes. If the control unit 33 receives a sensor signal before the time T'4 comes, it changes to state 3 again.

[0066] The transition between state 3 and state 4 is explained by generalization. First, in state 3, the time difference ΔT(n-1)(n) is calculated, and the predicted time T'(n+1) for the arrival of the n+1th pulse noise is calculated using the time difference ΔT(n-1)(n). In addition, n is an integer greater than 2. The state is transitioned to state 4, and when the sensor signal is received before the predicted arrival time T'(n+1), the state is transitioned to state 3. Then, the control unit 33 increases the integer substituted into n by 1, and calculates the time difference ΔT(n-1)(n) from the reception of the n-1th signal to the reception of the nth signal. The control unit 33 adds the time difference ΔT(n-1)(n) to the time T(n), and recalculates the time T'(n+1) for the arrival of the n+1th pulse noise. Thereafter, each time the state is transitioned to state 3, the control unit 33 repeats the same operation, increasing the integer substituted into n by 1 each time. When the sensor signal is not received from the sensor 32 during the waiting period until the time T'(n+1), and the time T'(n+1) comes, the control unit 33 outputs the strobe signal = 1, and the state is changed to state 5. By receiving the strobe signal = 1, the switch element 31 is turned off. In addition, the operation when changing from state 5 to state 3 and the operation when changing from state 6 to state 3 are the same as the operation when changing from state 4 to state 3.

[0067] In State 5 , the control unit 33 waits for the sensor signal from the sensor 32 during a period from the time T′(n+1) when the n+1-th impulse noise is predicted to arrive until the open time Toff has passed.

[0068] When a sensor signal is received during the period from time T'(n+1) to the open time Toff, the control unit 33 outputs a strobe signal = 0 after the open time Toff has passed, and transitions to state 3. In state 3, the control unit 33 increases the integer substituted into n by 1, calculates the time difference ΔT(n-1)(n) from the reception of the n-1th signal to the reception of the nth signal, and further calculates the arrival time T'(n+1) of the next n+1th signal using the time difference ΔT(n-1)(n).

[0069] If the sensor signal is not received during the period from time T′(n+1) to the open time Toff, the control unit 33 outputs the gate signal=0 after the open time Toff has elapsed, and the state is changed to State 6 .

[0070] In state 6, the control unit 33 waits for receiving a sensor signal during the period from the opening time Toff to the waiting time Twait. If a sensor signal is received during the waiting time Twait, the control unit 33 changes to state 3. In state 3, the control unit 33 increases the integer substituted into n by 1, and predicts the arrival time T'(n+1) of the n+1th signal based on the difference between the reception time of the n-1th signal and the nth signal. If a sensor signal is not received during the waiting time Twait, the control unit 33 changes to state 1 and returns to the stable state. The operation of the control unit 33 in state 1 is the same as the above operation.

[0071] The noise filter 3 of the first embodiment includes a control unit 33, the sensor 32 detects the periodic pulse noise applied to the power line 4 and sends the sensor signal to the control unit 33, and when a time equivalent to the time from the detection of the first pulse noise to the detection of the second pulse noise has passed since the second pulse noise was detected, the control unit 33 turns off the switch element 31, and electrically cuts off the power supply 1 and the load 2 in response to the arrival of the pulse noise. Therefore, the noise filter 3 of the first embodiment can prevent the pulse noise from flowing to the load 2 without hindering the continuous operation of the load 2.

[0072] In the first embodiment, the case where the power line 4 is two wires is described, but the power line 4 may be three or more wires. In this case, the switch element 31 may be provided in each power line 4, and therefore, the switch elements 31 corresponding to the number of power lines 4 may be prepared.

[0073] In addition, in Embodiment 1, the case where the sensor 32 is provided on the power line 41 and the power line 42 is described. However, the sensor 32 may be provided at any position as long as it is a configuration capable of detecting the pulse noise applied to the power line 4. For example, the sensor 32 may be provided in a configuration connected in series with a capacitor having a function of removing the pulse noise. As an example of such a capacitor, there is a Y capacitor connected between the power line and the ground line.

[0074] As a modified example, the noise filter 3 may also include a power supply circuit 5 that supplies power to the load 2 when the load 2 is electrically disconnected from the power supply 1. Here, as the load 2, for example, a circuit of a precision device that cannot operate even when it is electrically disconnected for a few ns is assumed. In this case, the load 2 operates by applying a normal mode voltage. When the load 2 is also electrically disconnected from the power supply 1 within the open time Toff, that is, when the normal mode voltage applied to the load 2 becomes less than 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.

[0075] Figure 7 is a structural diagram of a noise filter in a modified example of Implementation 1. Figure 7 As shown, the power supply circuit 5 is provided in the power supply line 4 between the switch element 31 and the load 2. When the switch element 31 is in the off state, the power supply circuit 5 supplies power to the load 2. The power supply circuit 5 is, for example, a capacitor. The number of capacitors used as the power supply circuit 5 can be several, and there is no limit. In addition, the power supply circuit 5 can also use a capacitor provided for the purpose of instantaneous power failure countermeasures and current smoothing.

[0076] When a capacitor is used as the power supply circuit 5, a voltage drop occurs in the power supplied to the load 2, which depends on the capacitance value of the capacitor and the power consumption of the load 2. Therefore, the capacitance value of the capacitor required to keep the load 2 operating is calculated based on the power consumption of the load 2 and the length of the open time Toff when the switch element 31 is in the off state.

[0077] Figure 8 The diagram shows the relationship between the operation of the components of the noise filter 3 after the noise filter 3 is applied, the change in the voltage applied to the power line and the load, the open time Toff of the switch element 31, and the voltage applied between the first power line 41 and the second power line 42, that is, the power line voltage Vn. Figure 8 (a) to (e) in the upper part and Figure 4 (a) to (e) are the same. Figure 8 (f) shows the change of the normal mode voltage applied to the load 2 after the noise filter 3 in the modification is applied. During the time when the switching element 31 electrically connects and disconnects the power supply 1 and the load 2, the normal mode voltage changes.

[0078] When the switch element 31 is turned off, the load 2 is cut off from the power supply 1. Therefore, the load 2 is supplied with power from the capacitor used as the power supply circuit 5. In this case, Figure 8 As shown in (g), the voltage Vn between the power supply lines decreases over time as the capacitor is discharged. Therefore, in order to keep the load 2 operating, a capacitor having a sufficient capacitance calculated based on the power consumption of the load 2 and the length of the open time Toff when the switch element 31 is in the off state can be selected.

[0079] In addition, when the power supply 1 is the upstream side and the load 2 is the downstream side, the power supply 1, the sensor 32, the control unit 33, the switching element 31, the power supply circuit 5, and the load 2 can be electrically connected in the order from the upstream side. A diode bridge, a DC-DC converter, other filters, or an input / output protection circuit, etc., which are other circuits or elements, may be arranged between each circuit or element.

[0080] According to a variation, the noise filter 3 of the present application is provided with a power supply circuit 5 for supplying power to the load 2 when the load 2 is electrically disconnected from the power supply 1. Therefore, even if the load 2 is mounted on a circuit of a precision device that cannot operate even when it is electrically disconnected for a few ns, the load 2 can continue to operate.

[0081] Implementation Method 2

[0082] In the first embodiment, the case where the number of switch elements 31 required for the power lines 4 is described. In the present embodiment, the case where the number of power lines 4 is more than three and the power lines 4 between the power source 1 and the switch element 31 are provided with a diode bridge 6 is described. By configuring the switch element 31 downstream of the diode bridge 6, even if the number of power lines 4 is more than three, it can be composed of two switch elements. In addition, in the noise filter 3 of the second embodiment, most of the parts are common with the noise filter 3 of the first embodiment or its modified example. Therefore, the following description will focus on the differences from the noise filter 3 of the first embodiment or its modified example, and the description of the structure common to the noise filter 3 of the first embodiment or its modified example will be appropriately omitted.

[0083] Fig. 9 The configuration diagram of the noise filter 3 in the second embodiment is shown. In the second embodiment, an example is described in which the power line 4 is for three-phase AC power and the current flowing through the power line 4 is rectified by the diode bridge 6. The power line 4 is composed of a first power line 401, a second power line 402, and a third power line 403 provided at a position closer to the power source 1 than the diode bridge 6. In addition, the power line 7 provided at a position closer to the load 2 than the diode bridge 6 is composed 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 are only described as the power line 7 hereinafter. The diode bridge 6 rectifies the three-phase AC power supplied from the power source 1 into DC power and outputs it. Thus, the diode bridge 6 utilizes a two-wire output for a three-wire input.

[0084] The configuration described in the second embodiment is the same as that in the first embodiment except that the power line 4 is for three-phase AC power and a diode bridge 6 is provided. That is, the configuration including the power supply 1 that supplies power to the load 2, the load 2 that is supplied with power from the power supply 1 via the power line 4 and driven by the supplied power, and the noise filter 3 provided on the power line 4 to protect the load 2 from the influence of pulse noise is the same as that in the first embodiment.

[0085] The noise filter 3 has a switch element 31, a sensor 32, and a control unit 33, which is the same as that in the first embodiment. In addition, the switch element 31 is composed of a first switch element 311 and a second switch element 312, which is the same as that in the first embodiment. Fig. 9 As shown, the first switching element 311 is provided on the first power line 701 . In addition, the second switching element 312 is provided on the second power line 702 .

[0086] Next, the operation of the noise filter 3 is described. The sensor 32 detects the pulse noise propagating in the first power line 401, the second power line 402, and the third power line 403, and sends a sensor signal to the control unit 33. When the control unit 33 receives the sensor signal from the sensor 32, it controls the on-off operation of the switch element 31. The operation performed by the control unit 33 is the same as that of the first embodiment. The switch element 31 prevents the pulse noise from propagating to the load 2 by performing the on-off operation.

[0087] According to the second embodiment, the diode bridge 6 for rectifying the three-phase AC power into DC power and outputting the power supply line 4 is provided, so that the input from the three-wire power supply line 4 is outputted by the two-wire power supply line 7. Therefore, the noise filter 3 can be constituted by the same number of switch elements 31 as the number of power supply lines 7 which is less than the number of power supply lines 4.

[0088] In the second embodiment, the noise filter 3 is used for a three-phase three-wire power supply, but the invention is not limited thereto. For example, when used for a three-phase four-wire power supply, the noise filter can be formed by using a smaller number of switching elements than the number of power lines.

[0089] Description of symbols

[0090] 1: power supply; 2: load; 3: noise filter; 4: power line; 5: power supply circuit; 6: diode bridge; 7: power line; 31: switching element; 32: sensor; 33: control unit; 41: first power line; 42: second power line; 311: first switching element; 312: second switching element; 401: first power line; 402: second power line; 403: third power line; 701: first power line; 702: second power line.

Claims

1. A noise filter, comprising: A switch element is provided on a power line electrically connecting a power source and a load, and switches the electrical connection or disconnection between the power source and the load by an on-off action; a sensor that detects periodic pulse noise applied to the power line; as well as The control unit turns off the switching element when a time corresponding to a time from detection of the first pulse noise to detection of the second pulse noise has elapsed since the second pulse noise was detected.

2. The noise filter according to claim 1, wherein: The noise filter includes a power supply circuit provided in the power supply line between the switching element and the load, and supplies power to the load when the switching element is turned off.

3. The noise filter according to claim 1, wherein: The sensor detects the second pulse noise that is continuous with the first pulse noise.

4. The noise filter according to claim 1, wherein: The switching element is a switching diode.

5. The noise filter according to claim 1, wherein: The sensor is a voltage sensor or a current sensor.

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

7. The noise filter according to claim 1, wherein The sensor sends a first signal corresponding to the first pulse noise to the control unit when the first pulse noise is detected, and sends a second signal corresponding to the second pulse noise to the control unit when the second pulse noise is detected. The control unit performs control to turn off the switching element at a time when a difference between the time when the first signal and the time when the second signal is received has elapsed from the time when the second signal is received.

8. The noise filter according to claim 1, wherein The noise filter further includes a diode bridge provided on the power line between the power source and the switching element, and rectifying the three-phase alternating current supplied from the power source into direct current for output.

9. A noise removal method comprising the following steps: The sensor detects periodic pulse noise applied to a power line electrically connecting the power source and the load; When the sensor detects the first pulse noise, the sensor sends a first signal corresponding to the first pulse noise to the control unit; When the sensor detects the second pulse noise, the sensor sends a second signal corresponding to the second pulse noise to the control unit; The control unit calculates a time difference from when the first signal is received to when the second signal is received; the control unit determines whether the time difference has elapsed since the second signal was received; and When the time difference has elapsed since the second signal was received, the control unit performs control to turn off the switch element, wherein: The switch element switches the electrical connection or disconnection between the power source and the load through on-off operations.

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