Noise detection device and noise detection test method

Abstract

To improve convenience of noise detection by measuring a voltage change for a wide range of signal levels.SOLUTION: The input signal voltage dividing section 1 generates a measurement voltage by dividing the voltage of the input signal based on the set termination potential. The termination potential generating section 2 generates a termination voltage in the input signal voltage dividing section. The signal detecting unit 3 detects a measurement voltage outside a predetermined voltage range. The detection state holding unit 4 holds detection information indicating that the signal detecting unit 3 has detected a measurement voltage outside the predetermined range. The display unit 5 displays the detection information held by the detection state holding unit 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a noise detection device and a noise detection test method. [Background technology]

[0002] When measuring the circuit operation inside a device, it is common to use a general-purpose measuring instrument such as an oscilloscope. When checking the operation of a device on a printed wiring board to be measured, measurements are made by connecting probes to the check terminals.

[0003] Because probes are large and require a cable to connect to the measuring instrument itself, they are often connected to the check terminals after removing the cover of the instrument when performing measurements. Furthermore, if probing is difficult even after removing the cover due to other components such as printed wiring boards and mechanical parts, it is necessary to secure probing space by removing those other components or by shifting the positions of those components using extenders, etc.

[0004] As a noise detection technology for equipment, a technology has been proposed in which a comparator compares a signal received by a probe with a threshold value, and a latch circuit that holds the comparison output drives a display element to notify noise detection. A noise measurement device using a variable window comparator has also been proposed. A noise detection circuit has also been proposed in which a first reference voltage and a second reference voltage can be applied to different terminals of a single comparator, and the comparator output is fed back to one of the terminals. Another technology has been proposed in which noise is detected using voltage division in a voltage detection unit that detects when a target voltage reaches a predetermined voltage and outputs a predetermined signal upon detection. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 3-4273 [Patent Document 2] Registered Utility Model No. 3096469 [Patent Document 3] International Publication No. 2019 / 116470 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-47870 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with noise detection technology using probes, it is not possible to maintain the target equipment in its finished state, which can lead to changes in EMC (Electromagnetic Compatibility) characteristics such as noise paths and impedance, making it difficult to measure accurately.In addition, if the signals applied in EMC testing cause internal circuits such as protective elements to respond nonlinearly and quickly, the measurement bandwidth of a high-voltage oscilloscope probe may be insufficient, making it impossible to capture the phenomenon.

[0007] Furthermore, in technologies that drive display elements using a latch circuit that holds the comparison output of a comparator compared with a threshold value to notify noise detection, the measurable signal level is limited to the device's power supply voltage range. Therefore, this technology is insufficient for EMC evaluations, where voltages of several hundred volts or more can occur in both positive and negative polarities, making it difficult to perform appropriate noise detection. Furthermore, even noise measurement devices using variable window comparators have a limited range of noise detection levels. Furthermore, in technologies that use a single comparator pair, where the first and second reference voltages can be applied to different terminals and the comparator output is fed back to one of the terminals, it is difficult to mitigate changes in EMC characteristics during measurement. Furthermore, in technologies that use voltage division to detect noise, the measured voltage is limited to below the power supply voltage because it is assumed to be an IC output, making appropriate noise detection difficult.

[0008] One aspect of the present invention is to measure voltage changes over a wide range of signal levels to improve the convenience of noise detection. [Means for solving the problem]

[0009] A noise detection device according to one aspect has the following components: an input signal voltage divider that generates a measurement voltage by dividing an input signal based on a set termination potential; a termination potential generator that generates the termination voltage in the input signal voltage divider; a signal detector that detects the measurement voltage outside a predetermined voltage range; a detection status holder that holds detection information indicating that the signal detector has detected the measurement voltage outside the predetermined range; and a display that displays the detection information held by the detection status holder. [Effects of the Invention]

[0010] According to the present invention, it is possible to measure voltage changes over a wide range of signal levels, thereby improving the convenience of noise detection. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram of a noise detection device according to a first embodiment. [Figure 2] FIG. 10 is a diagram illustrating the relationship between an input signal and an output of a window comparator. [Figure 3] FIG. 1 is a plan view illustrating an example of a noise detection device. [Figure 4] FIG. 1 is a side view illustrating an example of a noise detection device. [Figure 5] FIG. 2 is a bottom view illustrating an example of a noise detection device. [Figure 6] 4 is a flowchart of a noise detection process performed by the noise detection device according to the first embodiment. [Figure 7] FIG. 1 is a diagram illustrating an example of an electronic device to be measured for a noise detection test. [Figure 8] 1 is a flowchart of a noise detection test for electronic devices. [Figure 9] FIG. 10 is a block diagram of a noise detection device in which the voltage division ratio of the input signal voltage dividing section is changeable. [Figure 10] FIG. 4 is a diagram illustrating the relationship between signal levels in the noise detection device. [Figure 11] FIG. 10 is a diagram illustrating the configuration of an input signal voltage dividing section and a termination potential generating section according to a third embodiment. [Figure 12] FIG. 10 is a diagram illustrating the configuration of a signal detection unit according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of a noise detection device and a noise detection test method will be described with reference to the drawings. The same elements are designated by the same reference numerals, and duplicated descriptions will be omitted as appropriate. Furthermore, each embodiment can be appropriately combined within a range that does not cause inconsistencies.

[0013] First Embodiment (Configuration of noise detection device) 1 is a block diagram of a noise detection device according to a first embodiment. The noise detection device 100 is a device that detects noise generated in various electronic devices. Electronic devices are generally subject to EMC regulations, and the noise detection device 100 is used for testing to comply with these EMC regulations.

[0014] When a high voltage is applied, noise may pass through a path such as a housing, damaging the IC. In such cases, it is important to determine the path through which the noise has flowed. For example, transient burst noise generated by power equipment, noise caused by electrostatic discharge, or surge voltage generated by lightning may cause noise to flow to a circuit board on which an IC or other device is mounted. Therefore, the noise detection device 100 is mounted on the circuit board and detects whether noise has flowed onto the circuit board.

[0015] 1, the noise detection device 100 includes an input signal voltage dividing unit 1, a terminal potential generating unit 2, a signal detection unit 3, a detection state holding unit 4, a display unit 5, and a power supply unit 6. The noise detection device 100 further includes input terminals 101 and 102.

[0016] An input signal to be measured is input to input terminals 101 and 102. The input voltage due to the input signal is the potential difference between input terminal 101 and input terminal 102.

[0017] The power supply unit 6 has a power supply 61. The power supply 61 is, for example, a small battery such as a button cell. The power supply 61 provides a power supply voltage of several volts. By using a small battery as the power supply 61, the entire noise detection device 100 can be made smaller and insulation can be ensured.

[0018] The input signal voltage dividing unit 1 is an attenuator having resistors 11 and 12. The resistor 11 is connected to an input terminal 101. The resistors 11 and 12 are connected in series. A path branches between the resistors 11 and 12, and the branched path is connected to input terminals of comparators 35 and 36 of the signal detecting unit 3. The resistor 12 is connected to an inverting input terminal of an amplifier 23 of the terminal potential generating unit 2. The output terminal of the amplifier 23 is connected to a path extending from the resistor 12 to the amplifier 23.

[0019] The input signal voltage dividing unit 1 divides the voltage according to the signal level of the input signal input to the input terminal 101, i.e., the voltage value of the input voltage, using the ratio of resistors 11 and 12 and the termination voltage set by the termination potential generating unit 2. That is, even if the voltage value of the input voltage is much larger than the power supply voltage supplied from the power supply unit 6, the input voltage is divided and attenuated to a voltage value that can be measured. Hereinafter, the voltage after the input voltage is divided will be referred to as the "measurement voltage."

[0020] The measured voltage is the sum of the input voltage multiplied by the resistance value of resistor 12 divided by the sum of the resistance values ​​of resistors 11 and 12, and the termination voltage multiplied by the resistance value of resistor 11 divided by the sum of the resistance values ​​of resistors 11 and 12. Then, the input signal voltage dividing unit 1 outputs a voltage based on the termination voltage generated by the termination potential generating unit 2 to comparators 35 and 36 from a path branching between resistors 11 and 12.

[0021] In this way, the input signal voltage dividing section 1 divides the input signal based on the set terminal potential to generate a measurement voltage.

[0022] The termination potential generating unit 2 has resistors 21 and 22 and an amplifier 23. The resistors 21 and 22 are connected in series to a path connecting the input and output of the power supply 61, i.e., a path connecting the power supply voltage (VDD) and ground (GND). The path branches between the resistors 21 and 22, and the branched path is connected to the non-inverting input terminal of the amplifier 23. The output terminal of the amplifier 23 is fed back to the inverting input terminal. In other words, the amplifier 23 has a voltage follower configuration and operates as a buffer. Furthermore, the output of the amplifier 23 is connected to one end of the resistor 12 as the termination voltage of the input signal voltage dividing unit.

[0023] The termination potential generating unit 2 generates a termination voltage for the input signal voltage dividing unit 1. The resistors 21 and 22 have high resistance values ​​that do not affect the current consumption of the entire circuit. The power supply voltage provided by the power supply 61 is divided in accordance with the voltage division ratio of the resistors 21 and 22. The voltage divided by the resistors 21 and 22 is then input to the amplifier 23.

[0024] The amplifier 23 is a low-current-consumption buffer circuit, and is capable of suppressing current consumption. The amplifier 23 receives an input of a voltage divided by resistors 21 and 22, and outputs a voltage having the same voltage value as the input voltage. The output of the amplifier 23 becomes the termination voltage of the input signal voltage divider unit 1. Depending on the voltage division ratio of the resistors 21 and 22, the voltage value of the divided voltage can be set to any level between 0 and the power supply voltage. Therefore, by adjusting the voltage division ratio of the resistors 21 and 22, the termination voltage of the input signal voltage divider unit 1 can be set to a desired voltage value.

[0025] When resistor 22 is zero, the termination voltage is 0 V, so when the voltage of the input signal is negative, the measured voltage is also negative. Because noise detection device 100 uses a positive voltage for noise detection, when the termination voltage is 0 V, noise detection can be performed when the voltage of the input signal is positive. However, by setting resistor 22 to a desired value other than zero, the termination voltage can be made 0 V or higher, and noise detection device 100 can also accept negative values ​​as the voltage of the input signal.

[0026] In this way, the termination potential generating unit 2 generates the termination voltage in the input signal voltage dividing unit 1. More specifically, the termination potential generating unit 2 uses the amplifier 23 as a buffer, and sets a voltage corresponding to the predetermined voltage output from the amplifier 23 to which a predetermined voltage has been input as the termination voltage. Here, the voltage obtained by dividing the power supply voltage by the resistors 21 and 22 is an example of a "predetermined voltage."

[0027] The signal detection unit 3 has resistors 31 to 34 and comparators 35 and 36. The resistors 31 to 33 are connected in series to a path connecting the input and output of the power supply 61, i.e., a path connecting the power supply voltage and ground. The path branches between the resistors 31 and 32, and the branched path is connected to one input terminal of the comparator 35. The path branches between the resistors 32 and 33, and the branched path is connected to one input terminal of the comparator 36. The other input terminal of the comparator 35 and the other input terminal of the comparator 36 are connected to the path branched between the resistors 11 and 12 in the input signal voltage dividing unit 1. The resistor 34 is a pull-up resistor having one end connected to a path to which the power supply voltage is supplied from the power supply 61 and the other end connected to the output terminals of the comparators 35 and 36.

[0028] The power supply voltage is divided by resistors 31 to 33. The voltage divided by the voltage division ratio of resistor 31 to resistors 32 and 33 is input to comparator 35. The voltage divided by the voltage division ratio of resistor 31 to resistors 32 and 33 is called a "first reference voltage." The voltage divided by the voltage division ratio of resistors 31 and 32 to resistor 33 is input to comparator 36. The voltage divided by the voltage division ratio of resistors 31 and 32 to resistor 33 is called a "second reference voltage." The first reference voltage input to comparator 35 is higher than the second reference voltage input to comparator 36.

[0029] The output circuits of the comparators 35 and 36 are open collector or open drain. Because the output circuits of the comparators 35 and 36 are open collector or open drain, when the output transistor is OFF, the output becomes high level due to the resistor 34. The comparators 35 and 36 and the resistor 34, which is a pull-up resistor, form a window comparator. The output of the window comparator is output to the clock terminal of the D flip-flop 41 of the detection state holding unit 4. The window comparator forms a wired OR (negative logic logical sum) with the comparators 35 and 36 and the resistor 34, which is a pull-up resistor.

[0030] The comparator 35 uses the input first reference voltage as the upper threshold for voltage comparison. The comparator 35 also receives the measurement voltage attenuated by the input signal voltage divider 1. The comparator 35 then determines whether the measurement voltage is equal to or greater than the first reference voltage, which is the upper threshold. If the measurement voltage is equal to or greater than the upper threshold, the comparator 35 outputs a low-level signal. Conversely, if the measurement voltage is less than the upper threshold, the comparator 35 outputs a high-level signal.

[0031] The comparator 36 uses the input second reference voltage as the lower threshold for voltage comparison. The comparator 36 also receives the measurement voltage attenuated by the input signal voltage divider 1. The comparator 36 then determines whether the measurement voltage is less than the second reference voltage, which is the lower threshold. If the measurement voltage is less than the lower threshold, the comparator 36 outputs a low-level signal. Conversely, if the measurement voltage is equal to or greater than the lower threshold, the comparator 36 outputs a high-level signal.

[0032] As described above, the upper and lower thresholds of the window comparator are set according to the ratio of the resistors 31 to 33. Hereinafter, the range equal to or greater than the lower threshold and equal to or less than the upper threshold may be referred to as the range of upper and lower thresholds.

[0033] 2 is a diagram showing the relationship between the input signal and the output of the window comparator. In FIG. 2, the attenuated measurement voltage is simply represented as the measurement voltage. Also, the output of the window comparator is represented as the output signal.

[0034] As shown in Figure 2, when the measured voltage is equal to or greater than the upper threshold, the window comparator outputs a low-level signal. When the measured voltage is less than the upper threshold and equal to or greater than the lower threshold, the window comparator outputs a high-level signal. When the measured voltage is less than the lower threshold, the window comparator outputs a low-level signal. In other words, the window comparator outputs a high-level signal if the measured voltage falls within the range of the upper and lower thresholds, and outputs a low-level signal if the measured signal is outside the range of the upper and lower thresholds.

[0035] In this way, the signal detection unit 3 detects a measured voltage outside a predetermined voltage range. Here, the range between the first reference voltage and the second reference voltage, i.e., the range between the upper and lower thresholds, is an example of a "predetermined voltage range." More specifically, the signal detection unit 3 uses a window comparator to determine whether the measured voltage is outside the predetermined voltage range.

[0036] Continuing the explanation, returning to Fig. 1, the detection state holding unit 4 includes a D flip-flop 41 and a switch 42.

[0037] The D flip-flop 41 has an input terminal D, a clock (CLK) terminal, an output terminal Q, an output terminal / Q, and a reset terminal. In the figure, a symbol with a bar above Q is represented as " / Q" here. Also, in FIG. 1, the reset terminal is represented as "CLR (Clear)." The input terminal D of the D flip-flop 41 is connected to a power supply voltage. That is, a high-level signal is input to the input terminal D.

[0038] The output from the window comparator of the signal detection unit 3 is input to the clock terminal of the D flip-flop 41. As described above, the window comparator of the signal detection unit 3 outputs a high-level signal if the measured voltage is within the range of the upper and lower thresholds, and outputs a low-level signal if the measured voltage is outside the range of the upper and lower thresholds. In other words, the clock terminal of the D flip-flop 41 receives as a clock the pulse-like output change that occurs when the measured voltage is outside the range of the upper and lower thresholds.

[0039] When a signal is input to the clock input terminal at the falling edge of the clock when it changes to low level while the input terminal D is receiving a high level signal, the output terminal Q of the D flip-flop 41 transitions to high level and is fixed at high level. In this case, the output terminal / Q of the D flip-flop 41 transitions to low level and is fixed at low level. By keeping the output terminal / Q at low level, the D flip-flop 41 holds information indicating that a measured voltage outside the range of the upper and lower threshold limits has been detected.

[0040] Furthermore, the reset terminal of D flip-flop 41 is connected to the supply path of the power supply voltage via switch 42. When switch 42 is off, the reset terminal is in a low-level state, and the state of D flip-flop 41 is maintained. When switch 42 is turned on, a high-level signal is input to the reset terminal, and the state of D flip-flop 41 is initialized. That is, when switch 42 is turned on, output terminal Q of D flip-flop 41 transitions to a low level, and output terminal / Q of D flip-flop 41 transitions to a high level.

[0041] When the switch 42 is turned on, it initializes the state of the D flip-flop 41. Therefore, when starting noise measurement by the noise detection device 100, it is preferable that the operator turn on the switch 42 to initialize the state of the D flip-flop 41, and then turn off the switch 42 before starting noise measurement.

[0042] In this way, the detection status holding unit 4 holds detection information indicating that the signal detection unit 3 has detected the measured voltage outside the predetermined range. Furthermore, when the signal detection unit 3 has detected a measured voltage outside the predetermined range, the detection status holding unit 4 holds the detection information by changing the voltage it holds. Transitioning the output terminal / Q to a low level and fixing it is an example of "holding detection information by changing the voltage it holds."

[0043] The display unit 5 has a resistor 51 and an LED (Light Emitting Diode) 52. One end of the resistor 51 is connected to a supply path of a power supply voltage (VDD). The other end of the resistor 51 is connected to an anode of the LED 52. The cathode of the LED 52 is connected to an output terminal / Q of a D flip-flop 41 included in the detection state holding unit 4.

[0044] If the measured voltage is within the range of the upper and lower thresholds, the output terminal / Q of the D flip-flop 41 is in a high level state, and no current flows to the LED 52. If the measured voltage falls outside the range of the upper and lower thresholds, the output terminal / Q of the D flip-flop 41 transitions to a low level, causing a steady current to flow to the LED 52 through the resistor 51, and the LED 52 lights up. Even if the input signal disappears, the output terminal / Q of the D flip-flop 41 remains low, so the LED 52 continues to light up.

[0045] In this way, the display unit 5 displays that the detection information is being held by the detection status holding unit 4. More specifically, the display unit 5 turns on the LED 52 when the detection status holding unit 4 holds the detection information. The lighting of the LED 52 is an example of "displaying that the detection information is being held by the detection status holding unit 4."

[0046] Fig. 3 is a plan view showing an example of a noise detection device, Fig. 4 is a side view showing an example of a noise detection device, and Fig. 5 is a bottom view showing an example of a noise detection device.

[0047] The small printed circuit board 110 of the noise detection device 100 has a size of approximately 2 to 3 cm in length and width. The size of the small printed circuit board 110 is basically determined by the size of the power source 61, such as a button battery.

[0048] 3, the switch 42, LED 52, amplifier 23, comparators 35 and 36, and D flip-flop 41 are arranged on one side of the small-sized printed circuit board 110. Furthermore, input terminals 101 and 102 extend from the small-sized printed circuit board 110. Hereinafter, the surface on which the switch 42, LED 52, amplifier 23, comparators 35 and 36, and D flip-flop 41 are arranged will be referred to as the front surface of the small-sized printed circuit board 110. The surface opposite to the front surface of the small-sized printed circuit board 110 will be referred to as the back surface of the small-sized printed circuit board 110.

[0049] 4 and 5, a battery case 62 and a clip 63 are provided on the back surface of the small printed circuit board 110. A power source 61, which is a button battery, is housed in the battery case 62, and the button battery is fixed to the battery case 62 by the clip 63.

[0050] When carrying out a noise detection test, an operator attaches noise detection device 100 shown in FIGS. 3 to 5 at an appropriate position on the target device, and detects noise that has passed through the target device.

[0051] (Example of noise detection) A specific example of noise detection will now be described. Here, it is assumed that resistor 11 has a resistance of 100 kΩ and resistor 12 has a resistance of 200 Ω. It is also assumed that the ratio of the resistance values ​​of resistor 21 and resistor 22 is 2:1, and resistors 31 to 33 have the same resistance value. It is also assumed that the electromotive force of power supply 61 is 3 V. For example, the case will be described where a voltage of 800 V is applied to input terminal 101 and a voltage of 0 V is applied to input terminal 102 as a measurement signal.

[0052] In this case, the voltage after the power supply voltage is divided by resistors 21 and 22 is 1 V. As a result, the termination voltage of input signal voltage divider 1 is set to 1 V. When the termination voltage is set to 1 V, the measurement voltage attenuated by voltage division by resistors 11 and 12 becomes 2.59 V. In other words, 2.59 V is input to comparators 35 and 36 as the measurement voltage.

[0053] Furthermore, since the power supply voltage is 3 V and resistors 31 to 33 have the same resistance value, the first reference voltage is 2 V and the second reference voltage is 1 V. That is, the first reference voltage of 2 V is input to comparator 35, and the second reference voltage of 1 V is input to comparator 36.

[0054] Because the measured voltage of 2.59V is greater than or equal to the upper threshold value of 2V, comparator 35 outputs a low-level signal. Also, because the measured voltage of 2.59V is greater than or equal to the lower threshold value of 1V, comparator 36 outputs a high-level signal. In this case, the window comparator outputs a low-level signal to the clock terminal of D flip-flop 41.

[0055] Upon receiving a clock signal at its clock terminal, the D flip-flop 41 transitions and fixes the output terminal / D to a low level. Since the output terminal / D of the D flip-flop 41 is fixed to a low level, a current flows through the LED 52, causing it to light up and remain lit.

[0056] That is, when a voltage of 800 V is applied to input terminal 101 as a measurement signal and a voltage of 0 V is applied to input terminal 102, LED 52 lights up, and the operator can confirm from the state of LED 52 that noise has flowed.

[0057] (Noise detection process flow) 6 is a flowchart of the noise detection process by the noise detection device according to the first embodiment. Next, the flow of the noise detection process by the noise detection device 100 according to the first embodiment will be described with reference to FIG.

[0058] Before the flow of FIG. 6 is executed, the following hardware settings are performed. The power supply voltage provided by the power supply 61 is divided by resistors 21 and 22 and input to the amplifier 23. The output from the amplifier 23 sets the termination voltage of the input signal voltage divider 1. The termination voltage is the power supply voltage divided by resistors 21 and 22. The power supply voltage provided by the power supply 61 is also divided by resistors 31 to 33 to generate a first reference voltage and a second reference voltage. The first reference voltage is input to comparator 35, and the second reference voltage is input to comparator 36, so that the first reference voltage and the second reference voltage are input to the window comparator of the signal detection unit 3. After the above hardware settings are performed, the following processing is executed.

[0059] The switch 42 is pressed, and the D flip-flop 41 is initialized (step S1).

[0060] A measurement signal is input from input terminals 101 and 102. Then, the voltage of the measurement signal is divided and attenuated by resistors 11 and 12 based on the termination voltage (step S2).

[0061] The attenuated measurement voltage is input to the comparators 35 and 36, and is then input to the window comparator of the signal detection unit 3 (step S3).

[0062] The window comparator of the signal detection unit 3 determines whether the measured voltage is outside the range of the upper and lower thresholds (step S4).

[0063] If the measured voltage is outside the range of the upper and lower thresholds (step S4: Yes), the window comparator of the signal detection unit 3 outputs a low-level signal (step S5).

[0064] The D flip-flop 41 receives the clock input to its clock terminal, and then transitions the output terminal / Q to a low level and fixes it there (step S6).

[0065] The LED 52 lights up (step S7).

[0066] On the other hand, if the measured voltage is within the range of the upper and lower threshold limits (step S4: No), the window comparator of the signal detection unit 3 outputs a high-level signal (step S8).

[0067] The D flip-flop 41 maintains its state (step S9).

[0068] The LED 52 remains off (step S10).

[0069] (Noise detection test) 7 is a diagram showing an example of an electronic device to be measured for a noise detection test. Here, a noise detection test is performed on electronic device 200.

[0070] Electronic device 200 is equipped with printed circuit board 210 and many other printed circuit boards 220, etc. Here, a noise detection test on printed circuit board 210 will be described. Multiple devices 211 and multiple mechanical parts 212 are arranged on printed circuit board 210. Electronic device 200 has cover 201. By removing cover 201, printed circuit board 210, etc. can be accessed from the outside.

[0071] 8 is a flowchart of a noise detection test for an electronic device. Here, an example flow of a noise detection test for the electronic device 200 will be described with reference to FIG.

[0072] The worker opens the cover 201 of the electronic device 200 to make the printed circuit board 210 accessible, and then the worker removes the printed circuit board 210 (step S101).

[0073] The worker connects noise detection device 100 with wiring via input terminals 101 and 102 to multiple locations on printed circuit board 210 where noise is suspected to flow, and then fixes noise detection device 100 (step S102). For example, the worker connects short cables to input terminals 101 and 102 with sockets, and brings the ends of the connected cables into contact with measurement points on printed circuit board 210 by soldering, clips, or the like.

[0074] The worker turns on the switch 42 of each noise detection device 100 placed on the printed circuit board 210 to initialize the D flip-flop 41 (step S103). After that, the worker turns off the switch 42. Here, the worker may initialize the D flip-flop 41 before placing the noise detection device 100 on the printed circuit board 210.

[0075] Thereafter, the worker returns the printed circuit board 210 to the housing of the electronic device 200, attaches the cover 201, and returns the electronic device 200 to its operational state (step S104).

[0076] Next, the worker artificially generates noise such as a lightning surge voltage, and passes electricity through the housing of the electronic device 200 (step S105).

[0077] Thereafter, the worker opens the cover 201, takes out the printed circuit board 210, and checks the LEDs 52 of the noise detection devices 100 arranged on the printed circuit board 210 (step S106).

[0078] If the LED 52 is lit, the worker estimates the path of the noise from the arrangement position of the noise detection device 100 whose LED 52 is lit (step S107).

[0079] In this way, by arranging a plurality of noise detection devices 100 on the printed circuit board 210, it can be determined that noise has passed along the row of noise detection devices 100 whose LEDs 52 are lit. In other words, by arranging a plurality of noise detection devices 100 on the printed circuit board 210, it can be confirmed what path the noise has taken to pass through the printed circuit board 210.

[0080] Here, we have described multiple noise detection devices 100 arranged on one printed circuit board 210, but this is not limiting; by arranging noise detection devices 100 on other printed circuit boards 220, etc., it is possible to check how noise passes through the entire electronic device 200.

[0081] (effect) As described above, the noise detection device 100 according to this embodiment divides and attenuates the voltage of the measurement signal based on a predetermined termination voltage, and uses a window comparator to determine whether the attenuated measurement voltage is within the range of the upper and lower threshold limits, thereby detecting noise.

[0082] Conventional noise detection technology limits the measurable signal level to the range of the device's power supply voltage. In contrast, by dividing the measurement signal voltage using the input signal voltage divider 1, it is possible to measure input signals with levels of several hundred volts or higher. Furthermore, by raising the attenuator's termination voltage toward the power supply voltage using the input signal voltage divider 1 and termination potential generator 2, the range of input signal voltages that can be measured can be expanded to negative voltages. Furthermore, the use of a window comparator in the signal detector 3 makes it possible to set upper and lower threshold limits for both positive and negative voltages. In this way, the noise detector 100 can set the attenuation, determined by the voltage division ratio of resistors 11 and 12, the termination voltage level, determined by the voltage division ratio of resistors 21 and 22, and the upper and lower threshold limits, determined by the settings of resistors 31 to 33, to desired values. By appropriately configuring these settings, the noise detector 100 can detect noise even in EMC evaluations where voltages of several hundred volts or higher may occur in both positive and negative polarities. Therefore, it is possible to measure voltage changes over a wide dynamic range independent of polarity, thereby improving the convenience of noise detection.

[0083] Second Embodiment Next, a second embodiment will be described. The noise detection device 100 according to this embodiment is capable of changing the detection level. There are three methods for changing the detection level: changing the voltage division ratio in the input signal voltage divider section 1, changing the termination voltage of the input signal voltage divider section 1, and changing the reference voltage used for comparison. These three methods will be described below.

[0084] (Change the voltage division ratio of the input signal voltage divider) 9 is a block diagram of a noise detection device in which the voltage division ratio of the input signal voltage dividing section 1 is changeable. Referring to FIG. 9, a noise detection device 100 in which the voltage division ratio of the input signal voltage dividing section 1 is changeable will be described.

[0085] The input signal voltage dividing unit 1 according to this embodiment has a variable resistor, resistor 12. By changing the resistance value of resistor 12, the voltage division ratio between resistors 11 and 12 can be changed. This makes it possible to generate a measurement voltage for noise detection at a desired ratio with respect to the input signal. In this way, the voltage division ratio of the input signal voltage dividing unit 1 according to this embodiment is changeable.

[0086] In this case, the voltage division ratio between resistor 11 and resistor 12 can be changed, and the detection level for the input signal can be changed without changing the upper and lower thresholds set in comparators 35 and 36 of signal detection unit 3. Here, in this embodiment, resistor 12 is a variable resistor, but resistor 11 may be a variable resistor, or both resistors 11 and 12 may be variable resistors.

[0087] (Change of termination voltage) Next, a noise detection device 100 in which the termination voltage is changeable will be described. Here, the description will be made with reference to FIG. 1. In the termination potential generation unit 2 according to this embodiment, the values ​​of the resistors 21 and 22, or both, can be changed. By changing the voltage division ratio between the resistors 21 and 22 in the termination potential generation unit 2, the termination voltage of the input signal voltage division unit 1 changes.

[0088] The termination voltage of the input signal voltage dividing section 1 in Figure 1 is expressed by the following formula (1). Here, Vref is the termination voltage of the input signal voltage dividing section 1. Furthermore, R21 is the resistance value of resistor 21, and R22 is the resistance value of resistor 22. Furthermore, VCC represents the power supply voltage.

[0089] Vref=R22 / (R21+R22)×VCC (1)

[0090] The measured voltage divided by the input signal voltage dividing unit 1 is expressed by the following equation (2): where Vatt is the measured voltage divided by the input signal voltage dividing unit 1, and Vin is the input voltage.

[0091] Vatt=R12 / (R11+R12)×Vin+R11 / (R11+R12)×Vref...(2)

[0092] When Vin is a negative voltage, adjusting R21 and R22 in equations (1) and (2) allows Vref to be set so that the value of Vatt calculated by equation (2) is a positive value in the range of 0 to VCC. By setting Vatt, which is the measurement voltage, to a positive value, the comparators 35 and 36 of the signal detection unit 3 can compare the measurement voltage with the upper and lower thresholds. In this way, the termination potential generation unit 2 according to this embodiment can change the predetermined voltage, which corresponds to the voltage obtained by dividing the power supply voltage by resistors 21 and 22.

[0093] (Change of reference voltage) Next, a description will be given of the noise detection device 100 in which the reference voltage is changeable. In the signal detection section 3 according to this embodiment, the first reference voltage and the second reference voltage can be changed by changing the combination of voltage values ​​of the resistors 31 to 33.

[0094] The first reference voltage is expressed by the following equation (3): where VH represents the first reference voltage.

[0095] VH=(R32+R33) / (R31+R32+R33)×VCC...(3)

[0096] The second reference voltage is expressed by the following equation (4): where VL represents the second reference voltage.

[0097] VL=R33 / (R31+R32+R33)×VCC...(4)

[0098] As shown in equations (3) and (4), the first reference voltage increases by increasing the ratio of the combined resistance of resistors 32 and 33 to the overall combined resistance of resistors 31 to 33. Also, the second reference voltage decreases by decreasing the ratio of the combined resistance of resistor 33 to the overall combined resistance of resistors 31 to 33. In this way, the signal detection unit 3 according to this embodiment is capable of changing the upper and lower thresholds used in the window comparator.

[0099] (Total detection level adjustment) 10 is a diagram showing the relationship between signal levels in the noise detection device. Signal level 301 indicates the voltage of the input signal. Signal level 302 indicates the measured voltage obtained by attenuating the voltage indicated by signal level 301.

[0100] By adjusting the voltage division ratio of resistors 11 and 12, it is possible to adjust the voltage width of signal level 302 with respect to signal level 301. In other words, it is possible to attenuate signal level 301 so that signal level 302 falls within the range between the power supply voltage (VCC) and ground (GND).

[0101] Furthermore, the termination voltage can be adjusted by adjusting the voltage division ratio of resistors 21 and 22. By adjusting the termination voltage, the minimum value of signal level 302 can be adjusted to 0 or more, and signal level 302 can be kept within the range between the power supply voltage (VCC) and ground (GND).

[0102] Furthermore, the first reference voltage and the second reference voltage can be adjusted by adjusting the voltage division ratio of each of the resistors 31 to 33. By adjusting the first reference voltage and the second reference voltage, the upper and lower thresholds of the signal level for detecting noise can be changed.

[0103] The above has been described as a case where the detection level can be changed by changing the voltage division ratio in the input signal voltage divider section 1, changing the termination voltage, or changing the reference voltage, but the noise detection device 100 may be configured to use any one of these three methods or a combination thereof.

[0104] (effect) As described above, the noise detection device 100 according to this embodiment can adjust the detection level. This allows the measurement voltage to be adjusted to a value comparable with the upper and lower thresholds, regardless of the magnitude or polarity of the signal level of the input signal, depending on the expected input signal, even if the signal level is large or has a negative value, thereby enabling noise detection.

[0105] Third Embodiment Next, a third embodiment will be described. Fig. 11 is a diagram showing the configuration of an input signal voltage dividing section and a termination potential generating section according to the third embodiment.

[0106] In the termination potential generating section 2 according to this embodiment, the output terminal of the resistor 11 is connected to a path connecting the resistors 21 and 22. In this case, the parallel combined resistance value of the resistors 21 and 22 plays the same role as the resistance value of the resistor 12 in FIG. 1. That is, the input signal is divided by the voltage division ratio between the resistance value of the resistor 11 and the parallel combined resistance value of the resistors 21 and 22.

[0107] Furthermore, in this case, the voltage obtained by dividing the power supply voltage by resistors 21 and 22 becomes the terminal voltage of the voltage division by input signal voltage divider 1. Also, path 13 is connected to comparators 35 and 36. This makes it possible to omit amplifier 23.

[0108] In this way, the termination potential generating section 2 according to this embodiment generates a termination voltage by dividing the power supply voltage using two resistors, 21 and 22. The input signal voltage dividing section 1 according to this embodiment divides the input signal using resistor 11 to which the input signal is input and a parallel combined resistance of the two resistors, 21 and 22, that the termination potential generating section 2 has.

[0109] (effect) The noise detection device 100 according to this embodiment does not need to include the resistor 12 and the amplifier 23. This allows the noise detection device 100 to be made smaller and consume less current.

[0110] <Fourth embodiment> Next, a fourth embodiment will be described below. Fig. 12 is a diagram showing the configuration of a signal detection unit according to the fourth embodiment.

[0111] The comparators 37 and 38 of the signal detection unit 3 according to this embodiment are not open collectors or open drains. In other words, the comparators 37 and 38 are circuits in which the signal level of a totem-pole output or the like is always determined. Furthermore, the signal detection unit 3 has an OR circuit 39 instead of the wired OR circuit using the resistor 34. The OR circuit 39 inverts and outputs the logical sum of the outputs of the comparators 37 and 38.

[0112] This configuration also produces an output similar to that of the wired OR shown in Fig. 1. That is, when noise is detected, the output terminal / Q of the D flip-flop 41 transitions to a low level. In this way, the signal detection unit 3 according to this embodiment uses comparators 37 and 38, which always determine the signal level, and the OR circuit 39, which is a logical OR circuit, to determine whether the measured voltage is outside the predetermined voltage range.

[0113] (effect) The comparators 37 and 38 according to this embodiment can be applied regardless of the output format. Generally, many fast-response comparators have an output level that is always set to either a high level or a low level. Therefore, the noise detection device 100 according to this embodiment can perform appropriate noise detection even when handling high-speed signals.

[0114] <System> The information including the processing procedures, control procedures, specific names, various data and parameters shown in the above documents and drawings can be changed arbitrarily unless otherwise specified.

[0115] Furthermore, the components of each device shown in the figure are functional concepts and do not necessarily have to be physically configured as shown. In other words, the specific form of distribution and integration of each device and circuit is not limited to that shown. In other words, all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0116] Some examples of combinations of the disclosed technical features are set out below.

[0117] (1) an input signal voltage dividing unit that divides an input signal based on a set termination voltage to generate a measurement voltage; a termination potential generating unit that generates the termination voltage in the input signal voltage dividing unit; a signal detection unit that detects the measured voltage outside a predetermined voltage range; a detection status holding unit that holds detection information indicating that the signal detection unit has detected the measured voltage outside the predetermined voltage range; a display unit that displays the detection information held by the detection state holding unit; A noise detection device comprising: (2) The noise detection device according to (1), wherein the input signal voltage dividing section has a variable voltage dividing ratio. (3) The noise detection device described in (1) or (2) is characterized in that the termination potential generation unit uses an amplifier as a buffer, and sets a voltage corresponding to the predetermined voltage output from the amplifier to which a predetermined voltage has been input as the termination voltage. (4) The noise detection device according to (3), wherein the terminal potential generating unit is capable of changing the predetermined voltage. (5) the termination potential generating unit divides a power supply voltage using two resistors to generate the termination voltage; The input signal voltage dividing section divides the input signal using a resistor to which the input signal is input and a parallel combined resistance of the two resistors included in the termination potential generating section. The noise detection device according to any one of (1) to (4) above. (6) The noise detection device according to any one of (1) to (5), wherein the signal detection unit uses a window comparator to determine whether the measured voltage is outside the predetermined voltage range. (7) The noise detection device according to (6), wherein the signal detection unit is capable of changing the upper and lower thresholds used in the window comparator. (8) The noise detection device according to any one of (1) to (5), wherein the signal detection unit determines whether the measured voltage is outside the predetermined voltage range using a comparator and an OR circuit whose signal level is always determined. (9) The noise detection device according to any one of (1) to (8), characterized in that the detection status holding unit holds the detection information by changing the voltage to be held when the signal detection unit detects the measured voltage outside the predetermined voltage range. (10) The noise detection device according to any one of (1) to (9), wherein the display unit lights up an LED when the detection status storage unit stores the detection information. (11) a step of attaching noise detection devices at a plurality of locations within a housing of an electronic device, the noise detection devices including an input signal voltage dividing section that divides an input signal based on a set terminal voltage to generate a measurement voltage, a terminal potential generating section that generates the terminal voltage in the input signal voltage dividing section, a signal detection section that detects the measurement voltage outside a predetermined voltage range, a detection status holding section that holds detection information indicating that the signal detection section has detected the measurement voltage outside the predetermined voltage range, and a display section that displays the detection information held by the detection status holding section; A step of passing electricity through the housing to the electronic device; a step of estimating a noise passage path based on the display of the display unit of each of the noise detection devices attached to the plurality of locations after electricity is passed through the electronic device; A noise detection test method comprising: [Explanation of symbols]

[0118] 1 Input signal voltage divider 2. Terminal potential generator 3. Signal detection section 4. Detection status storage unit 5 Display section 6 Power supply section 11, 12, 21, 22, 31-34 Resistance 23 Amplifier 35~38 Comparator 39 OR Circuit 41 D Flip-Flop 42 Switch 51 Resistance 52 LED 61 Power supply 62 Battery case 63 clips

Claims

1. an input signal voltage dividing unit that divides an input signal based on a set termination voltage to generate a measurement voltage; a termination potential generating unit that generates the termination voltage in the input signal voltage dividing unit; a signal detection unit that detects the measured voltage outside a predetermined voltage range; a detection status holding unit that holds detection information indicating that the signal detection unit has detected the measured voltage outside the predetermined voltage range; a display unit that displays the detection information held by the detection state holding unit; A noise detection device comprising:

2. 2. The noise detection device according to claim 1, wherein the input signal voltage dividing section has a variable voltage dividing ratio.

3. 2. The noise detection device according to claim 1, wherein the termination potential generating unit uses an amplifier as a buffer, and sets a voltage corresponding to a predetermined voltage output from the amplifier to which the predetermined voltage is input as the termination voltage.

4. 4. The noise detection device according to claim 3, wherein the terminal potential generating section is capable of changing the predetermined voltage.

5. the termination potential generating unit divides a power supply voltage using two resistors to generate the termination voltage; The input signal voltage dividing section divides the input signal using a resistor to which the input signal is input and a parallel combined resistance of the two resistors included in the terminal potential generating section.

2. The noise detection device according to claim 1.

6. 2. The noise detection device according to claim 1, wherein the signal detection unit uses a window comparator to determine whether the measured voltage is outside the predetermined voltage range.

7. 7. The noise detection device according to claim 6, wherein the signal detection unit is capable of changing upper and lower thresholds used in the window comparator.

8. 2. The noise detection device according to claim 1, wherein the signal detection unit determines whether the measured voltage is outside the predetermined voltage range by using a comparator and an OR circuit whose signal level is always determined.

9. 2. The noise detection device according to claim 1, wherein the detection state holding unit holds the detection information by changing the held voltage when the signal detection unit detects the measured voltage outside the predetermined voltage range.

10. 2. The noise detection device according to claim 1, wherein the display unit lights up an LED when the detection status storage unit stores the detection information.

11. a step of attaching noise detection devices at a plurality of locations within a housing of an electronic device, the noise detection devices including an input signal voltage dividing section that divides an input signal based on a set terminal voltage to generate a measurement voltage, a terminal potential generating section that generates the terminal voltage in the input signal voltage dividing section, a signal detection section that detects the measurement voltage outside a predetermined voltage range, a detection status holding section that holds detection information indicating that the signal detection section has detected the measurement voltage outside the predetermined voltage range, and a display section that displays the detection information held by the detection status holding section; A step of passing electricity through the housing to the electronic device; a step of estimating a noise passage path based on the display of the display unit of each of the noise detection devices attached to the plurality of locations after electricity is passed through the electronic device; A noise detection test method comprising:

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