Conduction noise visualization device and conduction noise visualization method

Abstract

To obtain a measurement result suitable for specifying a noise source or the like of conduction noise.SOLUTION: A conduction noise visualization device includes a trigger detection unit that detects a trigger on the basis of a switching operation of a circuit to be measured, a magnetic field strength measurement unit that measures a magnetic field strength at each measurement point arbitrarily set in the circuit to be measured for each measurement time arbitrarily set from a detection time point of the trigger, a storage unit that stores data of the magnetic field strength measured at each measurement point for each measurement time in association with the measurement point and the measurement time, and a display control unit that displays information on a measurement result at the measurement point on a display unit. A phase detection unit that detects a specific phase of a cycle longer than the cycle of the switching operation of the circuit to be measured is provided, and the trigger detection unit detects the trigger as a timing at which the switching operation is performed and which is close to the detected phase.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a conduction noise visualization device and a conduction noise visualization method. [Background technology]

[0002] In the internal circuits of electrical and electronic devices, tests (magnetic field probe method) are conducted to measure the magnetic fields generated from semiconductors such as ICs (Integrated Circuits) or LSIs (Large Scale Integration) in order to identify the noise source of conducted noise or visualize the transmission path. In this test, for example, a magnetic field probe is used near the measurement object to measure the magnetic field strength at the measurement point and the frequency characteristics of the magnetic field strength, and from the results, the measurement point and magnetic field strength are mapped on a plane to identify noise sources, etc.

[0003] Conduction noise from power semiconductor devices incorporated as power supply circuits in electrical and electronic equipment occurs at regular intervals due to the speed of the switching operation, due to the nature of the devices performing constant switching operations. It has now become possible to visualize the transmission path of the conduction noise generated by switching operations (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-25797 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional techniques described above, when the switching operation conditions related to the generation of conduction noise change at a period longer than the switching period, such as in an AC-DC converter or a DC-AC inverter, the magnetic field strength with different switching operation conditions for each measurement point is mapped on a plane, and in some cases the mapping is not suitable for identifying the noise source, etc.

[0006] The present disclosure has been made in consideration of these circumstances, and aims to provide a conduction noise visualization device and a conduction noise visualization method that can obtain measurement results suitable for identifying noise sources, etc., even when the conditions of switching operations related to the generation of conduction noise in the circuit under measurement change at a period longer than the switching period. [Means for solving the problem]

[0007] One aspect is a conduction noise visualization device comprising: a trigger detection unit that detects a trigger based on the switching operation of a circuit under measurement; a magnetic field strength measurement unit that measures magnetic field strength at each measurement point arbitrarily set in the circuit under measurement for each measurement time that is arbitrarily set from the time point at which the trigger detected by the trigger detection unit is detected; a storage unit that stores data on the magnetic field strength at each measurement point for each measurement time measured by the magnetic field strength measurement unit in association with the corresponding measurement point and the measurement time; and a display control unit that displays information about the measurement results at the measurement points on a display unit, wherein the conduction noise visualization device further comprises a phase detection unit that detects a specific phase with a period longer than the period of the switching operation of the circuit under measurement, and the trigger detection unit detects the trigger as a timing when the switching operation is occurring and close to the phase detected by the phase detection unit.

[0008] One aspect is a conduction noise visualization method in which a trigger detection unit detects a trigger based on the switching operation of a circuit under measurement, a magnetic field strength measurement unit measures the magnetic field strength at each measurement point arbitrarily set in the circuit under measurement for each measurement time arbitrarily set from the time point at which the trigger detected by the trigger detection unit is detected, a memory unit stores the data of the magnetic field strength at each measurement point for each measurement time measured by the magnetic field strength measurement unit in association with the corresponding measurement point and the measurement time, and a display control unit causes a display unit to display information about the measurement results at the measurement points, wherein a phase detection unit detects that a specific phase has a longer period than the period of the switching operation of the circuit under measurement, and the trigger detection unit detects the trigger as a timing when the switching operation is occurring and close to the phase detected by the phase detection unit. [Effects of the Invention]

[0009] According to the present disclosure, in the conduction noise visualization device and the conduction noise visualization method, measurement results suitable for identifying noise sources, etc. can be obtained even when the conditions of the switching operation related to the generation of conduction noise in the circuit under measurement change at a period longer than the switching period. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a schematic configuration example of a conduction noise visualization device according to an embodiment. FIG. [Figure 2A] FIG. 1 is a diagram illustrating an example of a circuit under measurement according to an embodiment. [Figure 2B] FIG. 2 is a diagram illustrating an example of a plurality of measurement points in a circuit under measurement according to an embodiment. [Figure 2C] FIG. 1 is a diagram illustrating an example of a circuit under measurement according to an embodiment. [Figure 3A] FIG. 2 is a diagram illustrating an example of the configuration of a conduction noise visualization processing unit according to the embodiment. [Figure 3B]5A to 5C are diagrams illustrating examples of signal waveforms in a conduction noise visualization processing unit according to the embodiment. [Figure 4A] FIG. 2 is a diagram illustrating an example of the configuration of a conduction noise visualization processing unit according to the embodiment. [Figure 4B] 1 is a diagram illustrating a configuration example of a three-phase PWM inverter circuit according to an embodiment. [Figure 4C] FIG. 4 is a diagram showing an example of a signal waveform in a conduction noise visualization processing unit according to the embodiment. [Figure 4D] 10A and 10B are diagrams illustrating other examples of signal waveforms in the conduction noise visualization processing unit according to the embodiment. [Figure 4E] FIG. 10 is a diagram showing an example of a procedure of a trigger generation process when the circuit under measurement according to the embodiment is a DC-AC inverter. [Figure 5A] FIG. 2 is a diagram illustrating an example of the configuration of a conduction noise visualization processing unit according to the embodiment. [Figure 5B] FIG. 2 is a diagram illustrating an example of the configuration of a trigger detection unit according to the embodiment. [Figure 5C] FIG. 4 is a diagram showing an example of a signal waveform in a conduction noise visualization processing unit according to the embodiment. [Figure 5D] FIG. 10 is a diagram showing an example of a procedure for a trigger generation process when the circuit under measurement according to the embodiment is a PFC and DC-DC converter. [Figure 6A] FIG. 2 is a diagram illustrating an example of the configuration of a conduction noise visualization processing unit according to the embodiment. [Figure 6B] FIG. 2 is a diagram illustrating an example of the configuration of a DUT according to an embodiment. [Figure 6C] FIG. 10 is a diagram showing an example of a procedure for trigger generation processing when the circuit under measurement according to the embodiment is a plurality of DC-DC converters. [Figure 7A] FIG. 10 is a diagram showing an example of a time domain magnetic field measurement result according to the embodiment. [Figure 7B] FIG. 10 is a diagram illustrating an example of a magnetic field measurement result in the frequency domain according to the embodiment. [Figure 8] FIG. 4 is a diagram showing an example of a signal of a drain-source voltage of a switching element according to the embodiment. [Figure 9] FIG. 10 is a diagram showing an example of a procedure of a magnetic field strength data acquisition process according to the embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of a procedure of a magnetic field intensity map generation process according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0012] [Conductive noise visualization device] FIG. 1 is a diagram showing a schematic configuration example of a conduction noise visualization device A1 according to an embodiment. The conduction noise visualization device A1 includes an input / output unit A11, a storage unit A12, a trigger detection unit A13, a phase detection unit A14, a magnetic field intensity measurement unit A15, a display unit A16, and a control unit A17. The phase detection unit A14 includes an arbitrary waveform generator A31. The magnetic field strength measuring unit A15 includes a magnetic field probe A51, a probe moving unit A52, a signal processing unit A53, and an imaging device A54. The signal processing unit A53 includes a data conversion unit A71 and a mapping unit A72. The control unit A17 includes a display control unit A91.

[0013] Here, the example in Figure 1 shows a schematic configuration example of the conduction noise visualization device A1, and for example, a configuration that does not include some components may be used, or a configuration that includes other components may be used. For example, the storage unit A12 may be provided as an external device of the conduction noise visualization device A1. For example, the display unit A16 may be provided as an external device of the conduction noise visualization device A1.

[0014] Furthermore, depending on the situation in which the conduction noise visualization device A1 shown in FIG. 1 is applied, some functions of the components may not be used. Furthermore, when the conduction noise visualization device A1 shown in FIG. 1 is configured by a circuit or the like, for example, one component may be distributed among multiple circuits or the like, or two or more components may be combined into one circuit or the like.

[0015] The input / output unit A11 has a function of inputting information from the outside and a function of outputting information to the outside. Here, the function of inputting information from outside may include, for example, a function of having an operation unit operated by a user (person) and inputting information according to the operation content of the operation unit.Furthermore, the function of inputting information from outside may include, for example, a function of inputting information output from an external device. Furthermore, the function of outputting information to the outside may include, for example, a function of outputting information to an external device.

[0016] The information may be input by receiving the information through wired or wireless communication. Furthermore, the information may be output by transmitting the information via wired or wireless communication.

[0017] The storage unit A12 stores various types of information. The trigger detector A13 detects a predetermined trigger, which in this embodiment is used as a trigger for measuring the magnetic field strength. Here, the trigger detection unit A13 may use the detection result of the phase detection unit A14 when generating a trigger, for example.

[0018] The phase detector A14 detects a specific phase of the alternating current (AC). The phase detection unit A14 does not necessarily have to know the value of a specific phase, and may, for example, detect that a specific phase is reached (the timing of a specific phase). The arbitrary waveform generator A31 has the function of generating an arbitrary waveform. Here, the function of the arbitrary waveform generator A31 may or may not be provided as a function of the phase detection unit A14.

[0019] The magnetic field strength measuring unit A15 has a function of measuring the magnetic field strength. In this embodiment, the magnetic field strength measurement unit A15 has a function of performing signal processing based on the measurement results of the magnetic field strength. The magnetic field probe A51 is a device that detects the magnetic field strength. The probe moving section A52 has a mechanism for moving the magnetic field probe A51. The area in which the magnetic field probe A51 can be moved is configured, for example, so that an area in which the magnetic field probe A51 needs to move for measurement is secured in advance. The measurement of a magnetic field may also be referred to as, for example, a measurement of magnetism.

[0020] The signal processing unit A53 has a function of performing various information processing on the measurement results of the magnetic field strength. The data conversion unit A71 has a function of performing predetermined data conversion. The data conversion unit A71 may have, for example, a function to convert the format of data (for example, description format), or may have a function to convert time domain data into frequency domain data. The mapping unit A72 has a function of performing predetermined mapping processing (for example, processing for drawing synthesis). The mapping is, for example, mapping based on the measurement results of the magnetic field strength. Here, the functions of the data conversion unit A71 and the mapping unit A72 are examples of the functions of the signal processing unit A53, and may not necessarily be provided.

[0021] In this embodiment, an example configuration is shown in which the functions of the signal processing unit A53 are included in the magnetic field strength measurement unit A15, but as another example, the functions of the signal processing unit A53 may be provided separately from the magnetic field strength measurement unit A15.

[0022] The imaging device A54 has a function of capturing an image. The imaging device A54 is configured using, for example, a camera. Note that imaging may also be called photography.

[0023] The display unit A16 has, for example, a screen, and displays information to be displayed on the screen. The control unit A17 performs various processes and controls in the conduction noise visualization device A1. The display control unit A91 has a function of controlling the display of information. In this embodiment, the display control unit A91 controls the display unit A16 to display the information to be displayed.

[0024] Here, the control unit A17 may include a processor such as a CPU (Central Processing Unit) and may perform various processes and controls by executing a predetermined program (computer program) using the processor. The program may be stored in the storage unit A12, for example. The conduction noise visualization device A1 may be configured using, for example, a computer. However, for example, the mechanisms of the magnetic field probe A51 and the probe moving unit A52 may be configured as devices separate from the computer. Also, for example, the imaging device A54 may be configured as a device separate from the computer. Furthermore, for example, if a display unit A16 is provided separately from the conduction noise visualization device A1 and the display unit A16 has all or part of the functions of the display control unit A91, the display control function of the display unit A16 does not need to be provided in the above-mentioned computer.

[0025] In this way, the conduction noise visualization device A1 may be configured in any way; for example, the conduction noise visualization device A1 may be configured as an integrated device (which may be called a system), or the conduction noise visualization device A1 may be configured from multiple devices (which may be called equipment, etc.).

[0026] [Circuit under test] FIG. 2A is a diagram schematically illustrating an example of a circuit under test (DUT) B1 according to the embodiment. In this embodiment, the circuit under test B1 is a circuit for which magnetic field strength is to be measured. The circuit under test B1 includes a switching element B11 that performs a switching operation. Here, the circuit under test B1 includes at least one switching element B11, and may include, for example, a plurality of switching elements including the switching element B11.

[0027] The circuit under test B1 may be a circuit that is normally treated as a single unit, such as a converter or an inverter, or may be a combination of two or more circuits that are normally treated as a single unit, such as a combination of a power factor correction (PFC) circuit and a converter. Furthermore, the circuit under test B1 may be, for example, a combination of multiple converters or multiple inverters, in which multiple circuits of the same type are normally treated as a single unit and connected in series or in parallel.

[0028] Here, in a circuit (e.g., a converter, inverter, or PFC) included in the circuit under test B1 that is normally treated as a single unit, if two or more switching elements perform switching operations in synchronization with one another, information on the timing of the switching operations may be detected, for example, based on a voltage (or current) signal related to at least one of these two or more switching elements. It may be arbitrarily set which of these two or more switching elements the signal related to is to be referenced.

[0029] FIG. 2B is a diagram schematically illustrating an example of a plurality of measurement points P(i, j) in a circuit under measurement B1 according to the embodiment. In the example of FIG. 2B, for convenience of explanation, it is assumed that the surface (measurement surface) of the circuit under test B1 during measurement has a rectangular shape. 2B shows the i-axis parallel to one of the two orthogonal sides of the rectangle, and the j-axis parallel to the other side. Coordinates are provided for the i-axis and j-axis, with the origin at zero (0) and integer values ​​increasing at regular intervals. In the example of Figure 2B, the minimum value of parameter i is 0 and the maximum value is m (m is an integer greater than or equal to 1), and the minimum value of parameter j is 0 and the maximum value is n (n is an integer greater than or equal to 1). In this embodiment, the measurement point P(i, j) is represented using coordinates (i, j). Here, the shape of the surface (measurement surface) of the circuit under test B1 during measurement may be arbitrary, and any measurement points may be used as the multiple measurement points.

[0030] <Other Examples of Circuits Under Test> FIG. 2C is a diagram schematically illustrating an example of a circuit under test (DUT) B2 according to the embodiment. The circuit under test B2 includes a plurality of M (M is an integer of 2 or more) switching power supply circuits (first switching power supply circuit C1 to M-th switching power supply circuit CM). Each of the first switching power supply circuit C1 to the M-th switching power supply circuit CM includes at least one switching element. Note that the circuit under test B2 shown in FIG. 2C is an example of the circuit under test B1 shown in FIG. 2A, and for the sake of convenience, the circuit under test B2 will be referred to as the circuit under test B1 below.

[0031] [Example when the circuit under test is an AC-DC converter] 3A and 3B, an example in which the circuit under test B1 is an AC (Alternating Current)-DC (Direct Current) converter is shown.

[0032] FIG. 3A is a diagram illustrating an example of the configuration of a conduction noise visualization processing unit 301 according to the embodiment. Here, the conduction noise visualization processing unit 301 represents a component including the conduction noise visualization device A1 and the circuit under test B1. Note that the name "conduction noise visualization processing unit" is a name for explanatory purposes and is not particularly limited. The conduction noise visualization processing unit 301 includes a bipolar power amplifier 331, a transformer 332, a LISN 333 which is a pseudo power circuit network, a resistor 334, an arbitrary waveform generator 335, a D flip-flop 336 having input terminals (D terminal, CLK terminal) and an output terminal (Q terminal), a magnetic field probe unit 337, an oscilloscope 338, a signal processing unit 339, and a DUT (Device Under Test) 311 which is a circuit under test B1. In this example, the DUT 311 is an AC-DC converter, and a resistor 334 is connected to the output side as a load.

[0033] An example of the general operation of the conduction noise visualization processing unit 301 will be shown. The arbitrary waveform generator 335 generates a signal Sg1 with a predetermined waveform and outputs the signal Sg1 to the power amplifier 331. Here, the waveform of the signal Sg1 is, for example, a sine wave having a predetermined frequency, but may be another waveform. Moreover, the arbitrary waveform generator 335 inputs a phase detection trigger signal Sg2 synchronized with the waveform of the signal Sg1 to the D terminal of the D flip-flop.

[0034] The power amplifier 331 amplifies the power of the signal Sg1 in response to the signal Sg1 from the arbitrary waveform generator 335, and outputs the amplified power (for example, AC power having a voltage of 100 V) to the transformer 332. The power is input to the DUT 311 via a transformer 332 and a LISN 333 .

[0035] The DUT 311 operates using the power, and at least one switching element performs a switching operation. In this example, the switching element is a field effect transistor (FET). A signal Sg3 of the gate-source voltage VGS of the switching element is input to the clock terminal (CLK terminal) of the D flip-flop 336. Here, the gate-source voltage VGS of the switching element is the gate drive voltage of the switching element.

[0036] The D flip-flop 336 outputs a trigger signal Sg4 from the Q terminal to the oscilloscope 338. The magnetic field probe unit 337 measures (detects) the magnetic field strength at each measurement point P(i, j) of the DUT 311. The magnetic field probe unit 337 outputs the measurement results to the oscilloscope 338. The oscilloscope 338 acquires the measurement result at the timing according to the trigger signal Sg4, and outputs the measurement result to the signal processing unit 339.

[0037] The signal processing unit 339 performs predetermined signal processing using the measurement results input from the oscilloscope 338 . The signal processing unit 339 may perform, for example, a process of acquiring a spectrogram, a process of determining a magnetic field strength distribution, and the like.

[0038] 3A, when the conduction noise visualization device A1 shown in Fig. 1 is applied, the arbitrary waveform generator 335 configures the function of the arbitrary waveform generator A31 (phase detection unit A14), the D flip-flop 336 configures the function of the trigger detection unit A13, the magnetic field probe unit 337 configures the magnetic field probe A51 and probe movement unit A52 of the magnetic field intensity measurement unit A15, and the oscilloscope 338 and signal processing unit 339 configure the function of the signal processing unit A53. The oscilloscope 338 may also be considered to be an example of the display unit A16. In the example of FIG. 3A, the DUT 311 is an example of the circuit under test B1. In the example of FIG. 3A, the transformer 332, the LISN 333, and the resistor 334 are auxiliary circuit units for measurement. In the example of FIG. 3A, the power amplifier 331 may be regarded as, for example, a function of the phase detector A14.

[0039] FIG. 3B is a diagram showing an example of a signal waveform in the conduction noise visualization processing unit 301 according to the embodiment. In the graph shown in FIG. 3B, the horizontal axis represents time, and each vertical axis represents the voltage of each signal. Figure 3B shows the signal waveforms in the conduction noise visualization processing unit 301, including the waveform of the AC input signal Sg1, the waveform of the phase detection trigger signal Sg2, the waveform of the signal Sg3 of the gate-source voltage VGS of the switch element of the DUT 311, and the waveform of the trigger signal Sg4.

[0040] Here, the phase detection trigger signal Sg2 has a waveform that indicates a specific phase angle (for example, 50°). The D flip-flop 336 generates a trigger that is synchronized with both the phase detection trigger and the switching action (eg, the predetermined timing of the voltage VGS). As a result, the conduction noise visualization processing unit 301 can acquire, for example, data on magnetic field strength at a specific phase angle and under consistent conditions at turn-on (rising of gate voltage) for all measurement points.

[0041] For example, in conventional measurements, the magnetic field strength was measured continuously every time period equivalent to two cycles of switching operation (e.g., 20 μs), but in this embodiment, the magnetic field strength can be measured for a time period equivalent to two cycles of switching operation (e.g., 20 μs) once every predetermined time period (e.g., 10 ns).

[0042] In addition, when the AC-DC converter that is DUT 311 is configured using a diode bridge, for example, if conductive noise tends to occur during the period when the diode bridge is energized, a configuration may be used in which the measurement interval (measurement time interval) of the magnetic field strength is shortened during the period when the diode bridge is energized, and the measurement interval is lengthened (relatively long) during other periods.

[0043] 3A and 3B, when the circuit under test B1 according to the embodiment is an AC-DC converter, it is possible to provide a component such as a field programmable gate array (FPGA) instead of the D flip-flop 336. The component may perform a process similar to the trigger generation process shown in FIG. 4E. In other words, the examples of FIGS. 3A and 3B are similar to the example of FIG. 4E in other respects, except for the signal used as the AC voltage.

[0044] [When the circuit under test is a DC-AC inverter] 4A to 4E, an example in which the circuit under test B1 is a DC-AC inverter will be shown.

[0045] FIG. 4A is a diagram illustrating an example of the configuration of a conduction noise visualization processing unit 401 according to the embodiment. Here, the conduction noise visualization processing unit 401 represents a component including the conduction noise visualization device A1 and the circuit under test B1. Note that the name "conduction noise visualization processing unit" is a name for the purpose of explanation and is not particularly limited. The conduction noise visualization processing unit 401 includes a DC stabilized power supply 431, a LISN 432 which is a pseudo power supply circuit network, a motor 433, a trigger detection unit 434, a magnetic field probe unit 435, an oscilloscope 436, a signal processing unit 437, and a DUT 411 which is a circuit under test B1. In this example, the DUT 411 is a DC-AC inverter, and a motor 433, which is a load, is connected to the output side.

[0046] FIG. 4B is a diagram showing an example of the configuration of a three-phase PWM inverter circuit 501 according to the embodiment. The three-phase PWM inverter circuit 501 shown in FIG. 4B is a commonly known circuit. In this example, the three-phase PWM inverter circuit 501 is an example of a DC-AC inverter used as the DUT 411 .

[0047] The three-phase PWM inverter circuit 501 includes a U-phase high-side switching element 531 and a low-side switching element 532, a V-phase high-side switching element 541 and a low-side switching element 542, and a W-phase high-side switching element 551 and a low-side switching element 552.

[0048] FIG. 4B shows a power supply G1 and a motor G2. In this example, the power supply G1 corresponds to the DC stabilized power supply 431 shown in FIG. 4A, and the motor G2 corresponds to the motor 433 shown in FIG. 4A. In the example of FIG. 4B, the LISN 432 is omitted from the illustration.

[0049] FIG. 4B shows the voltage of each phase of the three-phase PWM inverter circuit 501. The U-phase output voltage is represented as voltage Vu, the V-phase output voltage is represented as voltage Vv, and the W-phase output voltage is represented as voltage Vw. The voltage between the U phase and the V phase (inter-phase voltage) is represented as voltage Vuv, the voltage between the V phase and the W phase (inter-phase voltage) is represented as voltage Vvw, and the voltage between the W phase and the U phase (inter-phase voltage) is represented as voltage Vwu.

[0050] The three-phase AC waveform is set by a signal wave (reference sine wave) having a frequency synchronized with the rotation speed of the motor G2. The triangular wave (modulation wave) is set by the carrier frequency that determines the switching frequency. The levels of both these waveforms are compared, and when the value of the signal wave is greater than the value of the triangular wave, an ON signal is input to a high-side switching element (for example, a transistor). In each phase, when the high-side switching element is in the on state, the voltages Vu, Vv, and Vw are at high level (H). Also, an inverted signal of the high-side signal is input to the low-side switching element.

[0051] The voltage supplied to the motor G2 is the difference between the input voltages to each phase (voltage Vu, voltage Vv, voltage Vw) (example of FIG. 4D). The inter-phase voltages (voltage Vuv, voltage Vvw, voltage Vwu) are supplied to the motor G2 as waveforms with the same frequency as the reference sine wave at the time of signal generation. The voltage supplied to the motor G2 can be adjusted by changing the levels of the three-phase AC and triangular wave when generating the PWM signal.

[0052] 4B shows an example of a schematic operation of the conduction noise visualization processing unit 401 shown in FIG. 4A. The DC regulated power supply 431 outputs power of a DC power supply (for example, power having a voltage of 100 V) to the LISN 432. The power is input to the DUT 411 via the LISN 432 .

[0053] The DUT 411 operates using this power, and in this example, six switching elements 531 to 532, 541 to 542, and 551 to 552 perform switching operations. In this example, each of the six switching elements 531 to 532, 541 to 542, and 551 to 552 is a field effect transistor (FET). As an example, a signal of the gate-source voltage VGS_QVL of the V-phase low-side switching element 542 in the DUT 411 is input to the trigger detection unit 434. Furthermore, a V-phase signal V1, which is a reference sine wave of the three-phase AC waveform in the DUT 411, is input to the trigger detection unit 434. Here, the gate-source voltage VGS_QVL of the V-phase low-side switching element 542 is the gate drive voltage of the switching element 542.

[0054] The trigger detection unit 434 outputs a trigger signal to the oscilloscope 436 in response to the input signal.

[0055] The magnetic field probe unit 435 measures (detects) the magnetic field strength at each measurement point P(i, j) of the DUT 411. The magnetic field probe unit 435 outputs the measurement results to the oscilloscope 436. The oscilloscope 436 acquires the measurement results at the timing corresponding to the trigger signal, and outputs the measurement results to the signal processing unit 437 .

[0056] The signal processing unit 437 uses the measurement results input from the oscilloscope 436 to perform predetermined signal processing. The signal processing unit 437 may perform, for example, a process of acquiring a spectrogram, a process of determining a magnetic field strength distribution, and the like.

[0057] 4A, when the conduction noise visualization device A1 shown in Fig. 1 is applied, the trigger detection unit 454 configures the functions of the phase detection unit A14 and the trigger detection unit A13, the magnetic field probe unit 435 configures the magnetic field probe A51 and the probe movement unit A52 of the magnetic field intensity measurement unit A15, and the oscilloscope 436 and the signal processing unit 437 configure the function of the signal processing unit A53. The oscilloscope 436 may be regarded as an example of the display unit A16. In the example of FIG. 4A, the DUT 411 is an example of the circuit under test B1. In the example of FIG. 4A, the LISN 432 and the motor 433 are auxiliary circuit units for measurement. In the example of FIG. 4A, the regulated DC power supply 431 may be regarded as, for example, an auxiliary circuit section for measurement, or as an external device of the conduction noise visualization device A1.

[0058] FIG. 4C is a diagram showing an example of a signal waveform in the conduction noise visualization processing unit 401 according to the embodiment. FIG. 4C shows an example in which an internal signal of the DUT 411 is input to the trigger detection unit 434 as a reference for the AC voltage. The example of FIG. 4C uses a configuration in which the signal V1 (reference sine wave) is output from the DUT 411 to the trigger detection section 434 in the example of FIG. 4A.

[0059] In the graph shown in FIG. 4C, the horizontal axis represents time, and each vertical axis represents the voltage of each signal. Figure 4C shows the signal waveforms in the conduction noise visualization processing unit 401, including a carrier frequency signal Sg11, a U-phase signal U1, a V-phase signal V1, and a W-phase signal W1, which are reference sine waves of the three-phase AC waveform, a V-phase input voltage signal Sg22, a W-phase input voltage signal Sg23, and a phase detection trigger signal Sg31.

[0060] Here, the signals U1, V1, and W1 have the same waveform as the three-phase AC waveform (reference sine wave). The carrier frequency signal Sg11 is a triangular wave, and in this example, a triangular wave comparison method is used. For example, the signal of the gate-source voltage VGS_QVL of the V-phase low-side switching element 542 is an inverted signal of the voltage Vv.

[0061] Further explanation will be given to FIG. 4C. In this example, in three-phase inverter control for three-phase modulation, an internal signal of an inverter control circuit that generates a gate drive signal is used. When the voltage of the reference sine wave (signal V1) is greater than the voltage of the triangular wave, the voltage Vv becomes high level (H), the gate-source voltage VGS_QVH of the V-phase high-side switching element 541 also becomes high level (H), and the gate-source voltage VGS_QVL of the V-phase low-side switching element 542 becomes low level (L). On the other hand, when the voltage of the reference sine wave (signal V1) is smaller than the voltage of the triangular wave, the voltage Vv becomes low level (L), the gate-source voltage VGS_QVH of the V-phase high-side switching element 541 also becomes low level (L), and the gate-source voltage VGS_QVL of the V-phase low-side switching element 542 becomes high level (H).

[0062] The trigger detection unit 434 receives the reference sine wave signal (signal V1) and the gate-source voltage VGS_QVL of the V-phase low-side switching element 542 from the DUT 411, and outputs a trigger signal. In the example of FIG. 4C, the zero-crossing time T0 indicates the time when the AC voltage signal V1 changes from negative to positive.

[0063] In this example, the trigger detection unit 434 detects the AC voltage signal V1 from the DUT 411, and determines the timing at which the signal V1 changes from negative to positive as the zero-cross time T0. The zero-cross time T0 occurs every cycle of the AC voltage. The trigger detection unit 434 generates a trigger signal based on the gate-source voltage VGS_QVL of the V-phase low-side switching element 542 and the zero-cross time T0.

[0064] FIG. 4D is a diagram showing another example of a signal waveform in the conduction noise visualization processing unit 401 according to the embodiment. FIG. 4D shows an example in which the output signal from the DUT 411 is input to the trigger detection unit 434 as the reference for the AC voltage. In the example of Figure 4D, instead of the configuration in the example of Figure 4A where signal V1 (reference sine wave signal) is output from DUT 411 to trigger detection unit 434 (example of Figure 4C), a configuration is used in which signal Sg24 of voltage Vuv between UV of the AC output is output from DUT 411 to trigger detection unit 434.

[0065] In this way, the trigger detection unit 434 receives the signal Sg24 of the voltage Vuv and the gate-source voltage VGS_QVL of the V-phase low-side switching element 542 from the DUT 411, and outputs a trigger signal. In this example, the signal Sg24 specifies the time when the reference sine wave (signal V1) has a predetermined phase. In the example of FIG. 4D, the zero-crossing time T0 indicates the time when the UV voltage Vuv of the AC output changes from negative to positive.

[0066] In this example, the trigger detection unit 434 detects the voltage Vuv of the AC output from the DUT 411, and determines the timing at which the voltage Vuv changes from negative to positive as the zero-cross time T0. The zero-cross time T0 occurs every cycle of the AC output (AC voltage). The trigger detection unit 434 generates a trigger signal based on the gate-source voltage VGS_QVL of the V-phase low-side switching element 542 and the zero-cross time T0.

[0067] In addition, instead of detecting the voltage Vuv and detecting the time when the voltage switches from a negative pulse voltage to a positive pulse voltage (zero-cross time T0), a configuration may be used in which, for example, the timing when the magnitude relationship between the pulse width of the voltage Vu and the pulse width of the voltage Vv is reversed is detected, and the time of that timing is set as the zero-cross time T0.

[0068] In the graph shown in FIG. 4D, the horizontal axis represents time, and each vertical axis represents the voltage of each signal. FIG. 4D shows, as signal waveforms in the conduction noise visualization processing unit 401, a carrier frequency signal Sg11 (for example, a triangular wave signal), a U-phase signal U1, a V-phase signal V1, and a W-phase signal W1 which are reference sine waves of a three-phase AC waveform, a U-phase input voltage signal Sg21, a V-phase input voltage signal Sg22, a W-phase input voltage signal Sg23, a signal Sg24 of the voltage Vuv between UV of the AC output, a signal Sg25 of the voltage Vvw between V and W of the AC output, a signal Sg26 of the voltage Vwu between W and U of the AC output, and a phase detection trigger signal Sg31.

[0069] FIG. 4E is a diagram showing an example of the procedure of the trigger generation process when the circuit under test B1 according to the embodiment is a DC-AC inverter. In this embodiment, the trigger generation process is performed by the trigger detection unit 434. In this case, the trigger detection unit 434 may be configured using, for example, an FPGA.

[0070] (Step S1) The trigger detection unit 434 measures the AC voltage and detects the zero-cross time T0, and then proceeds to the processing of step S2. In this example, the zero-cross time T0 is the time when the AC voltage changes from negative to positive, and occurs once every cycle of the AC voltage.

[0071] (Step S2) The trigger detection section 434 determines whether a predetermined time T_phase1 has elapsed since the zero cross time T0. As a result of this determination, if the trigger detection unit 434 determines that the predetermined time T_phase1 has elapsed since time 0 (step S2: YES), the process proceeds to step S3. On the other hand, if the trigger detection unit 434 determines that the predetermined T_phase1 time has not elapsed since time 0 (step S2: NO), it repeats the process of step S2.

[0072] (Step S3) The trigger detection unit 434 determines whether or not a rise in the gate voltage has occurred. As a result of this determination, if the trigger detection unit 434 determines that a rise in the gate voltage has occurred (step S3: YES), the process proceeds to step S4. On the other hand, if the trigger detection unit 434 determines that a rise in the gate voltage has not occurred (step S3: NO), it repeats the process of step S3.

[0073] (Step S4) The trigger detection unit 434 sets the trigger signal to high level (H), and then the process proceeds to step S5.

[0074] (Step S5) The trigger detection unit 434 determines whether a predetermined time T_phase2 has elapsed since time 0. As a result of this determination, if the trigger detection unit 434 determines that the predetermined time T_phase2 has elapsed since time 0 (step S5: YES), the process proceeds to step S6. On the other hand, if the trigger detection unit 434 determines that the predetermined time T_phase2 has not elapsed since time 0 (step S5: NO), it repeats the process of step S5. Here, the T_phase2 time is longer than the T_phase1 time.

[0075] (Step S6) The trigger detection unit 434 sets the trigger signal to low level (L), and then proceeds to the processing of step S1. As a result, the trigger detection unit 434 repeats the same processing as above.

[0076] [When the circuit under test is a PFC or DC-DC converter] 5A to 5D, an example in which the circuit under test B1 is a PFC and DC-DC converter is shown. The PFC and the DC-DC converter may, for example, operate asynchronously.

[0077] FIG. 5A is a diagram illustrating an example of the configuration of a conduction noise visualization processing unit 601 according to the embodiment. Here, the conduction noise visualization processing unit 601 represents a component including the conduction noise visualization device A1 and the circuit under test B1. Note that the name "conduction noise visualization processing unit" is a name for the purpose of explanation and is not particularly limited. The conduction noise visualization processing unit 601 includes a bipolar power amplifier 631, a transformer 632, a LISN 633 which is a pseudo power circuit network, a resistor 634, an arbitrary waveform generator 635, a trigger detection unit 636, a magnetic field probe unit 637, an oscilloscope 638, a signal processing unit 639, and a DUT 611 which is a circuit under test B1. In this example, the DUT 611 is a PFC and DC-DC converter, and a resistor 634 is connected to the output side as a load.

[0078] An example of the general operation of the conduction noise visualization processing unit 601 will be shown. The arbitrary waveform generator 635 generates a signal with a predetermined waveform and outputs the signal to the power amplifier 631 . Here, the waveform of the signal is, for example, a sine wave having a predetermined frequency, but may be another waveform. Moreover, the arbitrary waveform generator 635 outputs to the trigger detector 636 a phase detection trigger signal Sg53 synchronized with the waveform of the signal.

[0079] The power amplifier 631 amplifies the power of the signal from the arbitrary waveform generator 635 in response to the signal, and outputs the amplified power (for example, AC power having a voltage of 100 V) to the transformer 632 . The power is input to the DUT 611 via a transformer 632 and a LISN 633 .

[0080] The DUT 611 operates using the power, and at least one switching element of the PFC and at least one switching element of the DC-DC converter perform switching operations. In this example, each of these switching elements is a field effect transistor (FET).

[0081] A PWM1 signal Sg51, which is a PWM (Pulse Width Modulation) signal of a PFC switching element, is input to a trigger detection unit 636. A signal Sg52 of PWM2, which is the PWM of the switching element of the DC-DC converter, is input to the trigger detection unit 636.

[0082] The trigger detection unit 636 outputs a trigger signal Sg55 to the oscilloscope 638 in response to the input signal. The magnetic field probe unit 637 measures (detects) the magnetic field strength at each measurement point P(i, j) of the DUT 611. The magnetic field probe unit 637 outputs the measurement results to the oscilloscope 638. The oscilloscope 638 acquires the measurement results at the timing according to the trigger signal Sg55, and outputs the measurement results to the signal processing unit 639.

[0083] The signal processing unit 639 performs predetermined signal processing using the measurement results input from the oscilloscope 638 . The signal processing unit 639 may perform, for example, a process of acquiring a spectrogram, a process of determining a magnetic field strength distribution, and the like.

[0084] 5A, when the conduction noise visualization device A1 shown in Fig. 1 is applied, the arbitrary waveform generator 635 configures the function of the arbitrary waveform generator A31 (phase detection unit A14), the trigger detection unit 636 configures the function of the trigger detection unit A13, the magnetic field probe unit 637 configures the magnetic field probe A51 and probe movement unit A52 of the magnetic field intensity measurement unit A15, and the oscilloscope 638 and signal processing unit 639 configure the function of the signal processing unit A53. Also, the oscilloscope 638 may be considered to be an example of the display unit A16. In the example of FIG. 5A, the DUT 611 is an example of the circuit under test B1. In the example of FIG. 5A, the transformer 632, the LISN 633, and the resistor 634 are auxiliary circuit units for measurement. In the example of FIG. 5A, the power amplifier 631 may be regarded as, for example, a function of the phase detector A14.

[0085] FIG. 5B is a diagram illustrating an example of the configuration of the trigger detection unit 636 according to the embodiment. The trigger detection unit 636 includes a NOT 711, an AND 712, a delay unit 713, a delay unit 714, an AND 715 having one input inverted, a D flip-flop 716 having input terminals (D terminal, CLK terminal) and an output terminal (Q terminal), and an RS flip-flop 717 having input terminals (S terminal, R terminal) and an output terminal (Q terminal).

[0086] An example of the general operation of the trigger detection unit 636 will be described below. The phase detection trigger signal Sg53 is input to NOT711, and the output signal from NOT711 is input to the R terminal of an RS flip-flop717. The PWM2 signal Sg52 is input to one input terminal of an AND 715 via a delay device 713, and the PWM2 signal Sg52 is inverted via a delay device 714 and then input to the other input terminal of the AND 715.

[0087] A phase detection trigger signal Sg53 is input to one input terminal of an AND 712, and a signal Sg54, which is an output signal from an AND 715, is input to the other input terminal of the AND 712. The output signal from the AND 712 is input to a D terminal of a D flip-flop 716. The PWM1 signal Sg51 is input to the clock terminal (CLK terminal) of the D flip-flop 716.

[0088] The output signal from the Q terminal of the D flip-flop 716 is input to the S terminal of the RS flip-flop 717 . The trigger signal Sg55 is output as an output signal from the Q terminal of the RS flip-flop 717.

[0089] FIG. 5C is a diagram showing an example of a signal waveform in the conduction noise visualization processing unit 601 according to the embodiment.

[0090] In the graph shown in FIG. 5C, the horizontal axis represents time, and each vertical axis represents the voltage of each signal. Figure 5C shows the signal waveforms in the conduction noise visualization processing unit 601, including the waveform of the PWM1 signal Sg51, the waveform of the PWM2 signal Sg52, the waveform of the phase detection trigger signal Sg53, the waveform of the SILENT signal Sg54, and the waveform of the trigger signal Sg55.

[0091] The signal Sg51 of PWM1 is a gate signal for the PFC switching element. The signal Sg52 of PWM2 is a gate signal for the switching element of the DC-DC converter. The phase detection trigger signal Sg53 is a signal corresponding to the phase detected by the function of the phase detection unit A14. The SILENT signal Sg54 is a signal generated from the PWM2 signal Sg52. The trigger signal Sg55 is detected by the function of the trigger detection unit A13.

[0092] Here, the phase detection trigger has a time width corresponding to a predetermined phase portion, and the phase portion may be, for example, 1°. As a specific example, when the phase portion is 1°, the time width from the rising edge to the falling edge of the phase detection trigger corresponds to 1°, and when the rising edge corresponds to a phase of 50°, the falling edge corresponds to a phase of 51°.

[0093] In this embodiment, the SILENT signal is generated from PWM2 so that the timing of the second turn-on of PWM1 is shifted relative to the turn-on and turn-off timings of PWM2. Such a configuration may be set in advance, for example, by prior experimentation or theory.

[0094] Further explanation will be given to FIG. 5C. In the example of FIG. 5C, the zero cross time T0 is not shown. The example of FIG. 5C shows how a predetermined time Ta has passed since the rising edge of PWM2, and how a predetermined time Tb has passed since the rising edge of PWM2. Here, the Tb time is longer than the Ta time.

[0095] If it is determined that the rising edge of PWM1 is within a predetermined period, the trigger signal Sg55 is set to high level (H). The predetermined period is a period during which the phase detection trigger signal Sg53 is at a high level (H) and the SILENT signal Sg54 is at a high level (H). As a result, PWM2 is not turned on or off during a period when the magnetic field strength (for example, a magnetic field strength map) is desired to be observed, such as the second rising edge of PWM1.

[0096] The example in Figure 5C illustrates a period R1 during which the trigger signal Sg55 changes from low level (L) to high level (H), and a period R2 during which the second rising edge of PWM1 occurs when the first rising edge of PWM1 occurs during period R1. In the example of Figure 5C, the trigger signal Sg55 rises to high level (H) when the rising edge of PWM1 first occurs during the period when the phase detection trigger signal Sg53 is at high level (H) and within a predetermined period from the rising edge of PWM2 (in this example, more than time Ta and less than time Tb).

[0097] The time width of the phase detection trigger signal Sg53 affects the accuracy of determining that AC is in a specific phase and the number of trials for determining whether the rising edge of PWM1 is within the SILENT width. The time width of the SILENT signal Sg54 affects the accuracy of the phase relationship between PWM1 and PWM2 and the probability that the rising edge of PWM1 is determined to be within the width of the SILENT signal Sg54.

[0098] For example, if the trigger signal Sg55 cannot be set to high level (H) even after a certain number of attempts in the time width of the phase detection trigger signal Sg53 in a certain AC cycle, determination is made in the next AC cycle. Therefore, to prevent a situation where it takes a long time (for example, seconds) to generate a trigger and therefore the measurement time is long, the time width of the phase detection trigger signal Sg53 and the time width of the SILENT signal Sg54 may be adjusted, taking into account the trade-off with accuracy.

[0099] FIG. 5D is a diagram showing an example of the procedure of the trigger generation process when the circuit under measurement B1 according to the embodiment is a PFC and DC-DC converter. In this embodiment, the trigger generation process is performed by the trigger detection unit 636. In this case, the trigger detection unit 636 may be configured using, for example, an FPGA.

[0100] (Step S11) The trigger detection unit 636 measures the AC voltage and detects the zero-cross time T0, and then proceeds to the process of step S12. In this example, the zero-cross time T0 is the time when the AC voltage changes from negative to positive, and occurs once every cycle of the AC voltage.

[0101] (Step S12) The trigger detection section 636 determines whether a time period equal to or greater than a predetermined T_phase1 time and equal to or less than a predetermined T_phase2 time has elapsed since the zero cross time T0. If, as a result of this determination, the trigger detection unit 636 determines that a time period equal to or greater than a predetermined T_phase1 time and equal to or less than a predetermined T_phase2 time has passed since the zero-cross time T0 (step S12: YES), the trigger detection unit 636 proceeds to processing in step S13. On the other hand, if the trigger detection unit 636 determines that a time period equal to or greater than the predetermined T_phase1 time and equal to or less than the predetermined T_phase2 time has not elapsed since the zero cross time T0 (step S12: NO), it repeats the processing of step S16. Here, the T_phase2 time is longer than the T_phase1 time.

[0102] (Step S13) The trigger detection unit 636 determines whether a time period equal to or greater than a predetermined time Ta and equal to or less than a predetermined time Tb has elapsed since the rising edge of PWM2. If the trigger detection unit 636 determines that a time period longer than or equal to a predetermined time Ta and shorter than or equal to a predetermined time Tb has elapsed since the rising edge of PWM2 (step S13: YES), the trigger detection unit 636 proceeds to processing in step S14. On the other hand, if the trigger detection unit 636 determines that a time period longer than or equal to the predetermined Ta time and shorter than or equal to the predetermined Tb time has not elapsed since the rising edge of PWM2 (step S13: NO), it repeats the processing of step S13.

[0103] (Step S14) The trigger detection unit 636 determines whether or not it is the rising edge of PWM1. As a result of this determination, if the trigger detection unit 636 determines that it is the rising edge of PWM1 (step S14: YES), the process proceeds to step S15. On the other hand, if the trigger detection unit 636 determines that the timing is not the rising edge of PWM1 (step S14: NO), the process proceeds to step S11.

[0104] (Step S15) The trigger detection unit 636 sets the trigger signal to high level (H), and then the process proceeds to step S11.

[0105] (Step S16) The trigger detection unit 636 sets the trigger signal to low level (L), and then the process proceeds to step S11.

[0106] When the process returns to step S11, the trigger detection unit 636 repeats the same process as above.

[0107] [Modified Conduction Noise Visualization Device] For convenience of explanation, the same reference numerals as those shown in FIG. 1 will be used. An example of the configuration of a conduction noise visualization device A1 according to a modified example will be shown, in which the circuit under test B1 is a plurality of DC-DC converters. Here, the circuit under test B1 is, for example, a two-stage asynchronous DC-DC converter, but may also be a three or more stage DC-DC converter.

[0108] This example shows a case where the conduction noise visualization device A1 does not have the function of the trigger detection unit A13 detecting a trigger as timing close to the phase (specific phase) detected by the phase detection unit A14. That is, in this example, the trigger detection unit A13 is configured to detect a trigger based on the switching operation of the circuit under test B1, without taking phase into consideration. The conduction noise visualization device A1 of this example does not need to be equipped with the function of the phase detection unit A14 in the example of Figure 1, for example.

[0109] As an example configuration, the conduction noise visualization device A1 includes a trigger detection unit A13 that detects a trigger based on the switching operation of the circuit under test B1, and a magnetic field strength measurement unit A15 that measures the magnetic field strength at each measurement point arbitrarily set in the circuit under test B1 at every arbitrarily set measurement time from the point of detection of the trigger detected by the trigger detection unit A13. The circuit under test B1 is made up of a plurality of switching power supply circuits including a first switching power supply circuit, and performs the switching operations asynchronously. In addition, the trigger detection unit A13 detects a trigger so that, when the first switching power supply circuit is performing a switching operation and the first switching power supply circuit is about to switch again, a switching power supply circuit other than the first switching power supply circuit (for example, a second switching power supply circuit) is not performing a switching operation.

[0110] Therefore, in such a conduction noise visualization device A1, when asynchronous switching operations are performed in a two-stage DC-DC converter, the transmission path of the conduction noise caused by one of the DC-DC converters can be separated and the magnetic field strength (conduction noise) can be measured, thereby making it possible to generate, for example, a visualized magnetic field strength map.

[0111] In addition, in the conduction noise visualization device A1 according to this modified example, the trigger is not synchronized with a specific phase of AC, and therefore the effect obtained when the trigger is synchronized with both a specific phase of AC and the switching operation cannot be obtained, but the above-mentioned effect can be obtained.

[0112] <Example when the circuit under test is multiple DC-DC converters> 6A to 6C, an example in which the circuit under test B1 is a plurality of DC-DC converters will be shown. It should be noted that these multiple DC-DC converters operate, for example, asynchronously.

[0113] FIG. 6A is a diagram illustrating an example of the configuration of a conduction noise visualization processing unit 801 according to the embodiment. Here, the conduction noise visualization processing unit 801 represents a component including the conduction noise visualization device A1 and the circuit under test B1. Note that the name "conduction noise visualization processing unit" is a name for the purpose of explanation and is not particularly limited. The conduction noise visualization processing unit 801 includes a DC stabilized power supply 831, a LISN 832 which is a pseudo power supply circuit network, a trigger detection unit 834, a magnetic field probe unit 835, an oscilloscope 836, a signal processing unit 837, and a DUT 811 which is a circuit under test B1. In this example, the DUT 811 includes multiple DC-DC converters.

[0114] FIG. 6B is a diagram showing an example of the configuration of a DUT 811 according to the embodiment. In this example, the DUT 811 includes a bus converter 911, converters 921 and 931 which are POL (Point of Load) DC-DC converters, and an MPU (Micro Processing Unit) 922 and a GPU (Graphic Processing Unit) 932 as loads. In the examples of FIGS. 6A and 6B, the MPU 922 and GPU 932 included in the DUT 811 can each act as a load in the visualization of conducted noise.

[0115] Converter 921 and converter 931 are connected in parallel to the output terminal of bus converter 911 . The converter 921 is connected to an MPU 922 . The converter 931 is connected to a GPU 932 .

[0116] An example of the general operation of the conduction noise visualization processing unit 801 will be shown. The DC regulated power supply 831 outputs power of a DC power supply (for example, power having a voltage of 48 V) to the LISN 832. The power is input to the DUT 811 via the LISN 832.

[0117] The DUT 811 operates using this power, and the switching elements of the multiple DC-DC converters perform switching operations. In this example, the switching elements are field effect transistors (FETs).

[0118] A PWM1 signal, which is the PWM of the switching element of the bus converter 911, is input to the trigger detection unit 834. A PWM2 signal, which is the PWM of the switching element of the converter 921, is input to the trigger detection unit 834. A PWM3 signal, which is the PWM of the switching element of the converter 931, is input to the trigger detection unit 834.

[0119] The trigger detection unit 834 outputs a trigger signal to the oscilloscope 836 in response to the input signal. The magnetic field probe unit 835 measures (detects) the magnetic field strength at each measurement point P(i, j) of the DUT 811. The magnetic field probe unit 835 outputs the measurement results to the oscilloscope 836. The oscilloscope 836 acquires the measurement results at the timing corresponding to the trigger signal, and outputs the measurement results to the signal processing unit 837 .

[0120] The signal processing unit 837 performs predetermined signal processing using the measurement results input from the oscilloscope 836 . The signal processing unit 837 may perform, for example, a process of acquiring a spectrogram, a process of determining a magnetic field strength distribution, and the like.

[0121] 6A, when the conduction noise visualization device A1 shown in Fig. 1 is applied, the trigger detection unit 834 configures the function of detecting a trigger, the magnetic field probe unit 835 configures the magnetic field probe A51 and probe movement unit A52 of the magnetic field intensity measurement unit A15, and the oscilloscope 836 and signal processing unit 837 configure the function of the signal processing unit A53. Also, the oscilloscope 836 may be considered to be an example of the display unit A16. In the example of FIG. 6A, the DUT 811 is an example of the circuit under test B1. In the example of FIG. 6A, the LISN 832 is an auxiliary circuit unit for measurement. In the example of FIG. 6A, the DC stabilized power supply 831 may be considered to be, for example, an external device of the conduction noise visualization device A1. The MPU 922 and GPU 932 included in the DUT 811 can be replaced with resistors in the conduction noise visualization device A1.

[0122] FIG. 6C is a diagram showing an example of the procedure of the trigger generation process when the circuit under test B1 according to the embodiment is a plurality of DC-DC converters. In this embodiment, the trigger generation process is performed by the trigger detection unit 834. In this case, the trigger detection unit 834 may be configured using, for example, an FPGA.

[0123] (Step S21) The trigger detection unit 834 determines whether a time equal to or longer than a predetermined time Ta and equal to or shorter than a predetermined time Tb has elapsed since the rising edge of PWM2. If the trigger detection unit 834 determines that a time equal to or longer than the predetermined time Ta and equal to or shorter than the predetermined time Tb has elapsed since the rising edge of PWM2 (step S21: YES), the trigger detection unit 834 proceeds to the process of step S22. On the other hand, if the trigger detection unit 834 determines that a time longer than or equal to the predetermined time Ta and shorter than or equal to the predetermined time Tb has not elapsed since the rising edge of PWM2 (step S21: NO), it repeats the process of step S21. Here, the Tb time is longer than the Ta time.

[0124] The Ta and Tb times in step S21 may be set in the same sense as the Ta and Tb times in step S13 in the example of FIG. 5D, or may be set to the same times as the Ta and Tb times in step S13 in the example of FIG. 5D, or may be set to different times depending on the characteristics of the circuit under test B1, such as the switching operation.

[0125] (Step S22) The trigger detection unit 834 determines whether a time equal to or longer than a predetermined time Tc and equal to or shorter than a predetermined time Td has elapsed since the rising edge of PWM3. If the trigger detection unit 834 determines that a time equal to or longer than the predetermined Tc time and equal to or shorter than the predetermined Td time has elapsed since the rise of PWM3 (step S22: YES), the trigger detection unit 834 proceeds to the process of step S23. On the other hand, if the trigger detection unit 834 determines that a time longer than or equal to the predetermined Tc time and shorter than or equal to the predetermined Td time has not elapsed since the rising edge of PWM3 (step S22: NO), the trigger detection unit 834 proceeds to the processing of step S21. Here, the Td time is longer than the Tc time.

[0126] The Tc and Td times in step S22 may be set in the same sense as the Ta and Tb times in step S13 in the example of FIG. 5D, or may be set to the same times as the Ta and Tb times in step S13 in the example of FIG. 5D, or may be set to different times depending on the characteristics of the circuit under test B1, such as the switching operation.

[0127] (Step S23) The trigger detection unit 834 determines whether or not it is the rising edge of PWM1. As a result of this determination, if the trigger detection unit 834 determines that it is the rising edge of PWM1 (step S23: YES), the process proceeds to step S24. On the other hand, if the trigger detection unit 834 determines that the trigger is not a rising edge of PWM1 (step S23: NO), the process proceeds to step S21.

[0128] (Step S24) The trigger detection unit 834 sets the trigger signal to high level (H), and then the process proceeds to step S25.

[0129] (Step S25) The trigger detection unit 834 determines whether or not PWM1 is at a low level (L). As a result of this determination, if the trigger detection unit 834 determines that PWM1 is at a low level (L) (step S25: YES), the process proceeds to step S26. On the other hand, if the trigger detection unit 834 determines that PWM1 is not at low level (L) (step S25: NO), the process proceeds to step S25.

[0130] (Step S26) The trigger detection unit 834 sets the trigger signal to low level (L), and then the process proceeds to step S21.

[0131] When the process returns to step S21, the trigger detection unit 834 repeats the same process as above.

[0132] In the example of Figure 6C, when PWM1 rises within a predetermined period (in this example, more than Ta time and less than Tb time) from the rising edge of PWM2 and also within a predetermined period (in this example, more than Tc time and less than Td time) from the rising edge of PWM3, the trigger signal rises to high level (H).

[0133] [Signal processing example] 7A to 7B and 8 to 10, examples of signal processing performed by the various conduction noise visualization devices A1 described above will be shown. In this embodiment, the conduction noise visualization device A1 performs, for example, a spectrogram generation process and a magnetic field intensity map generation process as post-processing after obtaining the magnetic field measurement results. Such post-processing may be performed automatically by the conduction noise visualization device A1, for example.

[0134] <Data format example> In this embodiment, various data formats may be used for the data format of the magnetic field measurement results.

[0135] Here, an example of the data format of the magnetic field measurement results is shown. As a magnetic field measurement result, first, time domain data may be obtained in a data format consisting of text data and binary data. The text data represents setting data and is written in XML (Extensible Markup Language) format. The binary data represents the measurement result itself and includes IQ data (I data and Q data).

[0136] The data conversion unit A71 converts the time domain binary data into time domain text, and saves the converted text in CSV (Comma Separated Values) format. Next, the data conversion unit A71 converts the time domain text (CSV format) data into frequency domain CSV format data by performing a complex Fourier transform on the IQ data.

[0137] Here, as a Fourier transform technique, for example, a fast Fourier transform (FFT) may be used. Furthermore, in the Fourier transform, for example, a predetermined window (window function) may be used. For example, a Kaiser window may be used as the window. Furthermore, the transformed frequency domain data represents, for example, a power spectrum.

[0138] In this embodiment, the data obtained by such data conversion may be used to generate a spectrogram, a magnetic field intensity map, and the like.

[0139] <Time domain to frequency domain conversion> Conversion of magnetic field measurement results from time domain data to frequency domain data will be described with reference to FIGS. 7A and 7B.

[0140] FIG. 7A is a diagram illustrating an example of a time domain magnetic field measurement result according to the embodiment. In the graph shown in FIG. 7A, the horizontal axis represents time, and the vertical axis represents signal intensity. FIG. 7A shows a time domain measurement result signal St1 for the magnetic field measurement result.

[0141] For each section (period) of a predetermined time length N, a discrete Fourier transform is performed on the time domain measurement result signal St1. In the example of FIG. 7A, a plurality of sections are shown as section T1, section T2, section T3, . . .

[0142] FIG. 7B is a diagram illustrating an example of a magnetic field measurement result in the frequency domain according to the embodiment. In the graph shown in FIG. 7B, the horizontal axis represents time, and the vertical axis represents signal intensity. FIG. 7B shows the measurement result transform signal Sf1 in the frequency domain for the signal after the discrete Fourier transform.

[0143] The frequency domain measurement result transformed signal Sf1 is acquired for each interval of a predetermined time length N. In the example of Figure 7B, multiple intervals are shown: interval T1, interval T2, interval T3, .... An example of a Fourier spectrum is shown for each interval, which represents the change in frequency distribution over time.

[0144] FIG. 7B also shows a signal Sg71 of the gate-source voltage VGS of the switching element of the circuit under test B1. For example, the signal processing unit A53 may select a frequency at which conducted emission (CE) is large when the gate of the switching element is turned on, and map the magnetic field strength of the selected frequency.

[0145] 7B, the time when the signal Sg71 changes from low level (L) to high level (H) corresponds to section T2. ​​Then, in a frequency band R11 included in section T2, a magnetic field intensity Mg1 is measured. In this way, the magnetic field strength (in the example of Figure 7B, magnetic field strength Mg1) within an arbitrarily set frequency band (in the example of Figure 7B, frequency band R11) is measured at each arbitrarily set measurement time from the time the trigger is detected.

[0146] Here, in the examples of Figures 7A and 7B, multiple sections T1, T2, T3, ... are set up in such a way that the sections of time length N do not overlap on the time axis, but as another example, a configuration may be used in which, among such multiple sections, two adjacent sections have overlapping portions.

[0147] 7A and 7B, an example of processing performed by the conduction noise visualization device A1 is shown. The magnetic field strength measurement unit A15 uses the magnetic field probe A51 to measure the magnetic field strength at a measurement point P(0,0) arbitrarily set on the circuit under test B1, for a period of two switching periods (e.g., 20 μs) at every measurement time arbitrarily set (e.g., every 10 ns) from the time of detection of the trigger detected by the trigger detection unit A13, and stores the measurement result data in the memory unit A12 in association with the measurement point P(0,0).

[0148] Next, when the magnetic field strength measurement unit A15 completes measurement for a period of two switching cycles, it moves the magnetic field probe A51 to the next measurement point P(0, 1) and measures the magnetic field strength again for a predetermined time (in this example, the above-mentioned 20 μs) from the time the trigger is detected, and stores the measurement result data in the memory unit A12 in association with the measurement point P(0, 1). Similarly, the magnetic field intensity measurement unit A15 stores the measurement result data for all measurement points P(i, j) in association with the measurement points P(i, j) in the storage unit A12.

[0149] The magnetic field strength data stored in the storage unit A12 is time domain data stored in association with the corresponding measurement point P(i, j) and measurement time. The data conversion unit A71 converts this time domain data into frequency domain data by applying a window function to each of intervals T1, T2, T3, . . . of time length N and performing FFT.

[0150] The mapping unit A72 refers to the switching waveform of the circuit under test B1 (for example, a waveform such as the drain voltage of an FET) and selects a frequency with a large conducted emission (CE) from the frequency domain data obtained by FFT of a section Tk (k is an integer greater than or equal to 1) of time length N when the switching element is turned on, turned off, or when the voltage is oscillating. Then, the mapping unit A72 maps the magnetic field strength of the selected frequency for each measurement point P(i, j). As a result, the conduction noise visualization device A1 can visualize, for example, the reason why CE is large at that frequency, as well as the noise source and propagation path.

[0151] FIG. 8 is a diagram showing an example of a signal of the drain-source voltage of the switching element according to the embodiment.

[0152] In the graph shown in FIG. 8, the horizontal axis represents time, and the vertical axis represents the voltage of the signal. FIG. 8 shows a signal Sg81 of the drain-source voltage of the switching element.

[0153] The example of FIG. 8 shows a period R21 in which the signal Sg81 falls, a period R22 in which the signal Sg81 rises, and a period R23 in which the signal Sg81 oscillates. Here, the time widths of the periods R21, R22, and R23 shown in FIG. 8 are examples for the purpose of explanation, and are not necessarily strict.

[0154] FIG. 9 is a diagram illustrating an example of a procedure of the magnetic field strength data acquisition process according to the embodiment. In this embodiment, the magnetic field strength data acquisition process is performed by the magnetic field strength measurement unit A15.

[0155] (Step S61) The magnetic field strength measurement unit A15 captures an image of the circuit under test B1 using, for example, the imaging device A54, and then proceeds to the processing of step S62.

[0156] (Step S62) The magnetic field intensity measurement unit A15 divides the image data obtained by imaging to determine the two-dimensional coordinates of the measurement point P(i, j), and then proceeds to the processing of step S63.

[0157] Here, the processes of steps S61 and S62 may be performed in advance of the subsequent processes, for example.

[0158] (Step S63) The magnetic field strength measurement unit A15 moves the magnetic field probe A51 to the measurement point P(0, 0) by the probe movement unit A52, and then proceeds to the processing of step S64.

[0159] (Step S64) The magnetic field strength measurement unit A15 determines whether or not a rising edge of the trigger signal has occurred. As a result of this determination, if the magnetic field intensity measurement unit A15 determines that a rising edge of the trigger signal has occurred (step S64: YES), the magnetic field intensity measurement unit A15 proceeds to the process of step S65. On the other hand, if the magnetic field intensity measurement unit A15 determines that the rising edge of the trigger signal has not occurred (step S64: NO), it repeats the process of step S65.

[0160] (Step S65) The magnetic field strength measurement unit A15 measures the magnetic field strength at each measurement time, and then the process proceeds to step S66.

[0161] (Step S66) The magnetic field strength measurement unit A15 stores the position information of the measurement points in association with the data of the measurement times and the data of the measurement results (data of magnetic field strength), and then proceeds to the processing of step S67.

[0162] (Step S67) The magnetic field strength measurement unit A15 determines whether or not the measurement of the magnetic field strength at the final measurement point has been completed. If the magnetic field strength measurement unit A15 determines that the measurement of the magnetic field strength at the final measurement point is completed (step S67: YES), it ends the processing of this flow. On the other hand, if the magnetic field strength measurement unit A15 determines that the measurement of the magnetic field strength at the final measurement point has not been completed (step S67: NO), the process proceeds to step S68.

[0163] (Step S68) The magnetic field strength measurement unit A15 moves the magnetic field probe A51 to the next measurement point using the probe movement unit A52, and then proceeds to the processing of step S64.

[0164] FIG. 10 is a diagram illustrating an example of a procedure of a magnetic field intensity map generation process according to the embodiment. In this embodiment, the magnetic field strength map generation process is performed by the signal processing unit A53 of the magnetic field strength measurement unit A15. In this example flow, it is assumed that measurement by the magnetic field strength measurement unit A15 has already been completed, and the magnetic field strength data that is the measurement result has been stored in the storage unit A12 or the like.

[0165] (Step S71) The signal processing unit A53 refers to the magnetic field intensity data for each measurement time at the first measurement point P(0,0), and then proceeds to the processing of step S72. Here, the magnetic field strength data is time domain data.

[0166] (Step S72) The signal processing unit A53 selects K (K is an integer of 1 or more) intervals before and after the phenomenon that the user or the like wants to see from measurement times t0, t1, t2, ..., tJ (J is an integer of 1 or more, and in this example, an integer of 3 or more), and then proceeds to the processing of step S73.

[0167] Here, the phenomenon that the user or the like wants to see may be specified by an operation performed by the user (person), or may be automatically specified by the conduction noise visualization device A1 according to a predetermined rule. Furthermore, examples of phenomena that users may want to see include the phenomenon of the voltage falling period R21 in the example of Figure 8, the phenomenon of the voltage rising period R22 in the example of Figure 8, or the phenomenon of the voltage oscillation period R22 in the example of Figure 8.

[0168] (Step S73) The signal processing unit A53 converts the time domain data into frequency domain data (magnetic field intensity data) by using the data conversion unit A71 to perform a fast Fourier transform (FFT) on the magnetic field intensity for each of the selected K sections, with the magnetic field intensity for the time interval of time length N being multiplied by a predetermined window function, and then proceeds to the processing of step S74.

[0169] (Step S74) The signal processing unit A53 selects the frequency F1 at which measures against conducted emission (CE) are required, and acquires the magnetic field strength data at the frequency F1 from the frequency domain data (magnetic field strength data).Then, the process proceeds to step S75.

[0170] (Step S75) The signal processing unit A53 uses the mapping unit A72 to map the acquired magnetic field strength data at frequency F1 onto image data as the magnetic field strength data of the measurement point P(i, j) being processed, and then proceeds to the processing of step S76. In this example, the measurement point P(i, j) to be processed is initially measurement point P(0.0), and is changed thereafter.

[0171] (Step S76) The signal processing unit A53 determines whether the mapping process has been completed up to the final measurement point. If the signal processing unit A53 determines that the mapping process has been completed up to the final measurement point (step S76: YES), it ends the process of this flow. On the other hand, if the signal processing unit A53 determines that the mapping process has not been completed up to the final measurement point (step S76: NO), the process proceeds to step S77.

[0172] (Step S77) The signal processing unit A53 refers to the data (time domain magnetic field intensity data) of the next measurement point P(i, j), and then proceeds to the processing of step S72.

[0173] In this example, the order in which all measurement points P(i, j) are processed one by one is set in advance for the multiple measurement points P(i, j). In this example, the initial measurement point is measurement point P(0, 0), and the order thereafter may be arbitrary.

[0174] In this example, in order to measure the magnetic field strength distribution of the circuit under test B1 (e.g., the printed circuit board of the circuit under test B1), the magnetic field strength measuring unit A15 measures the magnetic field strength using the magnetic field probe A51 while moving the magnetic field probe A51 at regular intervals in each of the i-axis direction and the j-axis direction using the probe moving unit A52. Then, the mapping unit A72 generates a magnetic field strength map by, for example, displaying the magnetic field strength with dots. Here, in this example, the magnetic field strength map is generated using the magnetic field strength in the frequency domain, but as another example, the magnetic field strength map may be generated using the magnetic field strength in the time domain.

[0175] Various visualized magnetic field strength maps may be used. For example, information on the distribution of magnetic field strength may be displayed within the area of ​​the circuit under test B1 as shown in FIG. 2B using colors or patterns that represent the magnetic field strength. Additionally, the information on the magnetic field strength measurements, or other information related thereto, may be visualized in any manner. In this way, various types of information may be visualized in various ways.

[0176] <About frequency filters> In this embodiment, a case has been described in which frequency domain data is generated from time domain data by performing FFT using a window function. A variety of such frequency filters may be used.

[0177] A frequency filter can, for example, limit the magnetic field strength of the measured conducted noise to that of a predetermined frequency band. Here, the predetermined frequency band may be set in advance, or may be specified by a user operation, for example. Furthermore, the predetermined frequency band may be specified using, for example, the center frequency of the frequency band and the bandwidth of the frequency band.

[0178] In this embodiment, the frequency filter may be configured, for example, by a digital filter that passes and acquires only components of a relevant frequency band from the magnetic field strength of the conducted noise measured from the magnetic field probe A51 via an oscilloscope. In this case, a digital filter is used to perform filtering on the time domain data for each measurement time, allowing only components in a specified frequency band to pass, thereby obtaining frequency domain data.

[0179] This makes it possible to visualize, on the time axis, the transmission path of conduction noise in an arbitrarily specified frequency band that occurs in conjunction with the switching operation of a semiconductor device, for example.

[0180] In this embodiment, the measurement results of the magnetic field strength (in this embodiment, conductive noise) are converted into frequency domain data and then visualized. However, as another example, the measurement results of the magnetic field strength (in this embodiment, conductive noise) may be visualized based on time domain data. In this way, visualization of conducted noise may be performed in any manner.

[0181] As described above, the conduction noise visualization device A1 of this embodiment can obtain measurement results suitable for identifying noise sources, etc., even when the conditions of the switching operation related to the generation of conduction noise in the measured circuit B1 change at a period longer than the switching period.

[0182] Here, in this embodiment, it is assumed that it takes a time longer than the AC period for the probe moving unit A52 to mechanically move the magnetic field probe A51 from one measurement point to the next. As a specific example, when the circuit under test B1 is an AC-DC converter or the like, a configuration in which the trigger is synchronized only with the switching operation may result in measurement results in which the AC phase may differ for each measurement point, and therefore the accuracy of visualization of the propagation path of the conducted noise may be insufficient. To address this issue, the conduction noise visualization device A1 of this embodiment generates a trigger synchronized with both a specific phase of the AC and the switching operation, and measures the magnetic field strength using this trigger as a trigger.

[0183] In this embodiment, a synchronization technique for synchronizing near-field magnetic field intensity distribution measurements has been devised to be suitable for many types of measurement targets (circuits under test B1). This makes it possible to generate magnetic field intensity maps under the same conditions, for example, and to visualize the propagation paths of conductive noise with high accuracy.

[0184] As a specific example, the conduction noise visualization device A1 of this embodiment can generate a magnetic field intensity map that visualizes the transmission path of the conduction noise for one operating condition (e.g., a condition synchronized with both the AC and switching operations) even if the conditions for the switching operation related to the generation of the conduction noise change at a period longer than the switching period due to the AC input of the AC-DC converter, which is the circuit under test B1, or the AC output of the DC-AC inverter, which is the circuit under test B1.

[0185] As a specific example, the conduction noise visualization device A1 according to this embodiment can generate a magnetic field intensity map that separately visualizes, for example, the transmission path of the conduction noise caused by the PFC or the transmission path of the conduction noise caused by the DC-DC converter, even when asynchronous switching operations are performed in the PFC and DC-DC converter, which are the circuit under test B1.

[0186] In this embodiment, a case has been described in which a specific phase is detected based on an AC voltage, but as another example, a configuration may be used in which a specific phase is detected based on an AC current. Furthermore, in order to detect a specific phase of AC, it is not necessary to know the value of the phase, and for example, a mode of detecting the timing of the phase may be used.

[0187] As an example configuration, the conduction noise visualization device A1 includes a trigger detection unit A13, a magnetic field intensity measurement unit A15, a storage unit A12, a display control unit A91, and a phase detection unit A14. The display unit A16 may be provided in the conduction noise visualization device A1, or may be provided as an external device to the conduction noise visualization device A1.

[0188] The trigger detector A13 detects a trigger based on the switching operation of the circuit under test B1. The magnetic field strength measuring unit A15 measures the magnetic field strength at each measurement point arbitrarily set in the circuit under test B1 at each measurement time arbitrarily set from the time point at which the trigger detected by the trigger detecting unit A13 is detected. The storage unit A12 stores data on the magnetic field strength measured at each measurement point by the magnetic field strength measurement unit A15 for each measurement time, in association with the corresponding measurement point and measurement time. The display control unit A91 causes the display unit A16 to display information relating to the measurement results at the measurement points. The phase detector A14 detects that a specific phase has a period longer than the period of the switching operation of the circuit under test B1, and thereby detects the timing of that phase. The trigger detector A13 then detects a trigger as a timing when a switching operation is being performed and which is close to the phase detected by the phase detector A14.

[0189] Therefore, the conduction noise visualization device A1 can visualize, for example, the transmission path of conduction noise generated in conjunction with the switching operation of a semiconductor device on the time axis. The conducted noise visualization device A1 can visualize the conduction noise transmission path for one operating condition (for example, the same operating condition or a similar operating condition) even if the switching operation conditions related to the generation of conducted noise change in a period longer than the switching period. As a specific example, the conducted noise visualization device A1 can measure and display the near magnetic field distribution synchronized with the switching period for one operating condition in order to identify the cause of noise emission from a power converter whose operating conditions related to the generation of conducted noise change in a period longer than the switching period.

[0190] Here, the timing at which a switching operation is performed and which is close to the phase detected by the phase detection unit A14 may be, for example, the timing of a turn-on or turn-off switching operation, and may be a timing within a predetermined period from the timing of the phase detected by the phase detection unit A14.

[0191] As an example configuration, in a conduction noise visualization device A1, a circuit under test B1 is an AC-DC converter. The phase detection section A14 detects a specific phase of the alternating current voltage (AC voltage) input to the circuit under test B1. Therefore, with the conduction noise visualization device A1, even if the conditions for the switching operation related to the generation of conduction noise change depending on the phase of the AC input of an AC-DC converter, the transmission path of the conduction noise can be visualized for one phase condition. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0192] As an example configuration, in the conduction noise visualization device A1, the circuit under test B1 is a DC-AC inverter. The phase detection section A14 detects a specific phase of the alternating current voltage (AC voltage) output from the circuit under test B1. Therefore, with the conduction noise visualization device A1, even if the conditions of the switching operation related to the generation of conduction noise change depending on the phase of the AC output of a DC-AC inverter, the transmission path of the conduction noise can be visualized for one phase condition. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0193] As one configuration example (the example of FIG. 3A), in the conduction noise visualization device A1, the trigger detection unit A13 includes a D flip-flop. The trigger detection unit A13 inputs the timing of a specific phase detected by the phase detection unit A14 as a phase detection trigger to the D input terminal (D terminal) of the D flip-flop, inputs a signal based on a switching operation (for example, a signal indicating turn-on or a signal indicating turn-off) to the clock input terminal (CLK terminal) of the D flip-flop, and uses the signal output from the Q output terminal (Q terminal) of the D flip-flop as a trigger. Therefore, with the conduction noise visualization device A1, for example, a trigger synchronized with the switching operation for one phase condition can be obtained with a simple configuration, and the trigger can be used to easily visualize the transmission path of the conduction noise for one phase condition. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0194] As an example configuration (example of Figure 3A, example of Figure 4A), in the conduction noise visualization device A1, the phase detection unit A14 detects the phase of the period of the voltage or current input to the circuit under test B1, the phase of the period of the voltage or current output from the circuit under test B1, or the phase of the period of the voltage or current generated inside the circuit under test B1. The phase detection section A14 detects one of these phases in accordance with, for example, the circuit under test B1. Therefore, in the conduction noise visualization device A1, for example, the timing of a specific phase can be easily detected by detecting a specific phase with a period longer than the period of the switching operation for a voltage or current signal that can be detected by the operation of the measured circuit B1. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0195] As one configuration example (the example of FIG. 3A and the example of FIG. 5A), in the conduction noise visualization device A1, the phase detection unit A14 includes an arbitrary waveform generator. The arbitrary waveform generator generates a sinusoidal voltage signal and a phase detection trigger for any phase of the sinusoidal voltage signal. The phase detection unit A14 amplifies the sinusoidal voltage signal and inputs it to the circuit under test B1 as an AC voltage, and detects a trigger based on a phase detection trigger and a switching operation. Therefore, in the conduction noise visualization device A1, for example, the AC input voltage signal and phase signal to be applied to the circuit under test B1 can be generated using a single arbitrary waveform generator, making it easy to detect the timing of a specific phase. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0196] As an example configuration, in the conduction noise visualization device A1, the magnetic field strength measurement unit A15 has a magnetic field probe A51 that measures the magnetic field strength, and a probe movement unit A52 that moves the magnetic field probe A51 in accordance with the circuit under test B1. The magnetic field strength measurement unit A15 moves the magnetic field probe A51 to each measurement point arbitrarily set on the circuit under test B1 using the probe movement unit A52, and measures the magnetic field strength at each measurement point at every arbitrarily set measurement time from the time when the trigger detected by the trigger detection unit A13 is detected. The period of the phase detected by the phase detection unit A14 is shorter than the time required for the probe movement unit A52 to move the magnetic field probe A51 between two measurement points that are adjacent in order. Therefore, with the conduction noise visualization device A1, even if it takes time to move the magnetic field probe A51, it is possible to visualize the transmission path of the conduction noise for one operating condition (e.g., the same operating condition or a similar operating condition). Here, as a manner in which the magnetic field probe A51 is moved in correspondence with the circuit under test B1, for example, the magnetic field probe A51 may be moved above or below the circuit under test B1 (for example, above or below the surface shown in Figure 2B), and a manner in which the magnetic field strength at each measurement point can be measured is used. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0197] As one configuration example (the example of FIG. 5A), in a conduction noise visualization device A1, a circuit under measurement B1 is made up of a plurality of switching power supply circuits including a first switching power supply circuit, and performs the switching operations asynchronously. The trigger detector A13 detects a trigger based on the switching operation of the first switching power supply circuit and the phase detected by the phase detector A14. Therefore, in the conduction noise visualization device A1, for example, when multiple switching power supply circuits in the measured circuit B1 are switching asynchronously, the conduction noise visualization device A1 can synchronize with one of these multiple switching power supply circuits and visualize the transmission path of the conduction noise for one phase condition. As a specific example, in the conducted noise visualization device A1, when an AC-DC converter, which is a circuit under test B1, is configured with a PFC (an example of a switching power supply circuit) and a DC-DC converter (another example of a switching power supply circuit), and the PFC and the DC-DC converter are switched asynchronously, the conducted noise transmission path can be visualized for one phase condition in synchronization with either the PFC or the DC-DC converter. For example, any one of the PFC and the DC-DC converter may be an example of a first switching power supply circuit, and the other may be an example of a second switching power supply circuit. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0198] As one configuration example (the example of FIG. 5A), in the conduction noise visualization device A1, the trigger detection unit A13 detects a trigger only during a period in which a specific time has elapsed since the switching operation of a switching power supply circuit other than the first switching power supply circuit (e.g., a second switching power supply circuit). Therefore, in the conducted noise visualization device A1, for example, it is possible to set a condition such that the turn-on or turn-off timing of the switching operation of the first switching power supply circuit does not overlap with the turn-on or turn-off timing of the switching operation of the second switching power supply circuit. As a result, in the conducted noise visualization device A1, for example, it is possible to visualize the transmission path of conducted noise that is generated and propagated by the turn-on of the first switching power supply circuit, while excluding the influence of the turn-on or turn-off of the second switching power supply circuit. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0199] As one configuration example (the example of FIG. 5A), the conduction noise visualization device A1 sets a period (a period in which a specific time has elapsed) so that switching operations (e.g., turn-on or turn-off) of switching power supply circuits other than the first switching power supply circuit (e.g., the second switching power supply circuit) are not performed at the timing when the switching operation of the first switching power supply circuit is performed again from the time of trigger detection (e.g., the timing of the second turn-on based on the first time). Therefore, the conduction noise visualization device A1 can visualize, for example, the transmission path of the conduction noise that is generated and propagated by turning on the first switching power supply circuit, while eliminating the influence of turning on or off the second switching power supply circuit. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0200] As one configuration example, in the conduction noise visualization device A1, the storage unit A12 stores data of magnetic field intensity as time domain data in association with the corresponding measurement point and measurement time. The magnetic field strength measuring unit A15 measures (detects) the magnetic field strength within an arbitrarily set frequency band at each measurement point arbitrarily set in the circuit under test B1, at each arbitrarily set measurement time from the time point at which the trigger detected by the trigger detection unit A13 is detected. Therefore, the conduction noise visualization device A1 can acquire the magnetic field intensity in a predetermined frequency band for each measurement point and for each measurement time, for example. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0201] As one configuration example, the conduction noise visualization device A1 includes a data conversion unit A71. The data conversion unit A71 performs a process of converting the time domain data stored in the storage unit A12 from binary data to CSV data, and a process of converting the CSV data into frequency domain data by applying a window function and performing FFT on it. Therefore, in the conduction noise visualization device A1, for example, time domain data can be converted into frequency domain data and various processes can be performed. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0202] As an example of configuration, the conduction noise visualization device A1 includes a mapping unit A72. The data conversion unit A71 converts the time domain data stored at each measurement point arbitrarily set in the circuit under test B1 for each measurement time arbitrarily set from the time point at which the trigger detected by the trigger detection unit A13 is detected into frequency domain data by applying a window function to each interval T1, T2, T3, ... of a predetermined time length N and performing an FFT. The mapping unit A72 maps the magnetic field strength of a specific frequency of the frequency domain data at each measurement point for a section of a predetermined time length N after a specific time has elapsed since the trigger was detected. Therefore, the conduction noise visualization device A1 can generate a magnetic field intensity map using, for example, data in the frequency domain. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0203] As an example configuration, in the conduction noise visualization device A1, the display control unit A91 combines an image showing the measurement points with an image of the circuit under test B1 in chronological order of each measurement time and displays the combined image on the display unit A16. Therefore, the conduction noise visualization device A1 can display information about the measurement results (for example, magnetic field intensity) for each measurement point in the circuit under test B1 in chronological order of the measurement times. Note that this configuration is just an example and is not necessarily limited to this configuration.

[0204] Here, the image showing each measurement point may be, for example, an image showing the measurement result of the magnetic field strength corresponding to the measurement point. In this case, the measurement result of the magnetic field strength corresponding to the measurement point may be, for example, an image showing the measurement result itself (e.g., raw data) obtained for the measurement point, or may be an image showing the result of performing predetermined information processing (e.g., processing such as Fourier transform) on the measurement result obtained for the measurement point. In this embodiment, the image showing each measurement point may be, for example, an image resulting from mapping performed by the mapping unit A72. In addition, in this embodiment, the image of the circuit under test B1 captured by the imaging device A54 is used as the image of the circuit under test B1, but as another example, an image that schematically represents the circuit under test B1 may be generated in advance by any image generation software, and the generated image may be used. The image may be stored in advance in the storage unit A12 of the conduction noise visualization device A1, for example.

[0205] [Regarding the above embodiment] A program for implementing the functions of any of the components of any of the above-described devices may be recorded on a computer-readable recording medium and loaded into a computer system for execution. The term "computer system" as used herein includes hardware such as an operating system or peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and compact discs (CDs) and read-only memories (ROMs), as well as storage devices such as hard disks built into computer systems. The term "computer-readable recording medium" also includes devices that retain a program for a certain period of time, such as volatile memory within a computer system that acts as a server or client when a program is transmitted over a network such as the Internet or a communication line such as a telephone line. Such volatile memory may be, for example, random access memory (RAM). The recording medium may also be, for example, a non-transitory recording medium.

[0206] The above program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by transmission waves in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has the function of transmitting information, such as a network such as the Internet or a communication line such as a telephone line. The above program may also be one that realizes part of the above-mentioned functions. Furthermore, the above program may be a so-called differential file that can realize the above-mentioned functions in combination with a program already recorded in a computer system. A differential file may also be called a differential program.

[0207] Furthermore, the functions of any of the components in any of the above-described devices may be implemented by a processor. For example, each process in the embodiments may be implemented by a processor operating based on information such as a program and a computer-readable recording medium storing information such as the program. Here, the functions of each unit of the processor may be implemented by, for example, individual hardware, or may be implemented by integrated hardware. For example, the processor may include hardware, and the hardware may include at least one of a circuit for processing digital signals and a circuit for processing analog signals. For example, the processor may be configured using one or more circuit devices mounted on a circuit board, or one or both of one or more circuit elements. An integrated circuit (IC) or the like may be used as the circuit device, and a resistor or a capacitor may be used as the circuit element.

[0208] Here, the processor may be, for example, a CPU. However, the processor is not limited to a CPU, and various types of processors such as a GPU or a DSP (Digital Signal Processor) may be used. The processor may also be, for example, a hardware circuit such as an ASIC (Application Specific Integrated Circuit). The processor may also be, for example, composed of multiple CPUs, or may be composed of a hardware circuit such as a multiple ASIC. The processor may also be, for example, composed of a combination of multiple CPUs and a hardware circuit such as a multiple ASIC. The processor may also include, for example, one or more of an amplifier circuit or a filter circuit that processes analog signals.

[0209] The embodiments of this disclosure have been described in detail above with reference to the drawings, but the specific configuration is not limited to this embodiment, and includes designs within the scope that do not deviate from the gist of this disclosure.

[0210] [Note] (Configuration example 1) to (Configuration example 15) are shown. It should be noted that the content of another configuration example that is subordinate to a certain configuration example may or may not be adopted.

[0211] (Configuration example 1) a trigger detection unit that detects a trigger based on a switching operation of the circuit under test; a magnetic field strength measuring unit that measures a magnetic field strength at each measurement point arbitrarily set in the circuit under test for each measurement time arbitrarily set from the time point at which the trigger detected by the trigger detecting unit is detected; a storage unit that stores data of the magnetic field strength measured at each of the measurement points by the magnetic field strength measurement unit for each of the measurement times in association with the corresponding measurement point and the measurement time; a display control unit that causes information about the measurement results at the measurement points to be displayed on a display unit; A conduction noise visualization device comprising: a phase detection unit that detects a specific phase having a period longer than the period of the switching operation of the circuit under test, the trigger detection unit detects the trigger as a timing when the switching operation is being performed and close to the phase detected by the phase detection unit. Conduction noise visualization device.

[0212] (Configuration example 2) the circuit under test is an AC-DC converter, the phase detection unit detects a specific phase of the AC voltage input to the circuit under test. The conduction noise visualization device according to (Configuration Example 1).

[0213] (Configuration example 3) the circuit under test is a DC-AC inverter, the phase detection unit detects a specific phase of the AC voltage output from the circuit under test. The conduction noise visualization device according to (Configuration Example 1).

[0214] (Configuration example 4) the trigger detection unit includes a D flip-flop, inputs the timing of a specific phase detected by the phase detection unit as a phase detection trigger to a D input terminal of the D flip-flop, inputs a signal based on the switching operation to a clock input terminal of the D flip-flop, and uses a signal output from a Q output terminal of the D flip-flop as the trigger; The conduction noise visualization device according to any one of (Configuration Example 1) to (Configuration Example 3).

[0215] (Configuration Example 5) the phase detection unit detects the phase of the period of the voltage or current input to the circuit under measurement, the phase of the period of the voltage or current output from the circuit under measurement, or the phase of the period of the voltage or current generated inside the circuit under measurement. The conduction noise visualization device according to any one of (Configuration Example 1) to (Configuration Example 4).

[0216] (Configuration Example 6) the phase detection unit includes an arbitrary waveform generator; the arbitrary waveform generator generates a sinusoidal voltage signal and a phase detection trigger for any phase of the sinusoidal voltage signal; the phase detection unit amplifies the sine wave voltage signal and inputs it to the circuit under test as an AC voltage, and detects the trigger based on the phase detection trigger and a switching operation. The conduction noise visualization device according to (Configuration Example 2) or (Configuration Example 4).

[0217] (Configuration Example 7) the magnetic field strength measurement unit has a magnetic field probe that measures the magnetic field strength, and a probe movement unit that moves the magnetic field probe in accordance with the circuit under test, and moves the magnetic field probe to each of the measurement points arbitrarily set on the circuit under test by the probe movement unit, and measures the magnetic field strength at each of the measurement points for each of the measurement times arbitrarily set from the time point at which the trigger detected by the trigger detection unit is detected, a period of the phase detected by the phase detection unit is shorter than the time required for the probe movement unit to move the magnetic field probe between two measurement points that are adjacent in order; The conduction noise visualization device according to any one of (Configuration Example 1) to (Configuration Example 6).

[0218] (Configuration Example 8) the circuit under test is configured with a plurality of switching power supply circuits including a first switching power supply circuit, and performs the switching operation asynchronously; the trigger detection unit detects the trigger based on the switching operation of the first switching power supply circuit and the phase detected by the phase detection unit. The conduction noise visualization device according to (Configuration Example 1).

[0219] (Configuration Example 9) the trigger detection unit detects the trigger only during a period in which a specific time has elapsed since the switching operation of the switching power supply circuits other than the first switching power supply circuit. The conduction noise visualization device according to (Configuration Example 8).

[0220] (Configuration Example 10) a period of time after the specific time has elapsed since the trigger was detected, at a timing when the switching operation of the first switching power supply circuit is performed again, is set so that the switching operation of the switching power supply circuits other than the first switching power supply circuit is not performed. The conduction noise visualization device according to (Configuration Example 9).

[0221] (Configuration Example 11) the storage unit stores the magnetic field strength data as time domain data in association with the corresponding measurement point and the measurement time; the magnetic field strength measuring unit measures the magnetic field strength within an arbitrarily set frequency band at each of the measurement points arbitrarily set in the circuit under test for each of the measurement times arbitrarily set from the time point at which the trigger detected by the trigger detecting unit is detected. The conduction noise visualization device according to any one of (Configuration Example 1) to (Configuration Example 10).

[0222] (Configuration Example 12) a data conversion unit that converts the time domain data stored in the storage unit from binary data to CSV data, and converts the CSV data into frequency domain data by applying a window function and FFT to the CSV data; The conduction noise visualization device according to (Configuration Example 11).

[0223] (Configuration Example 13) the data conversion unit converts the time domain data stored at each measurement point arbitrarily set in the circuit under test for each measurement time arbitrarily set from the time point at which the trigger detected by the trigger detection unit was detected into the frequency domain data by multiplying the time domain data by the window function for each interval of a predetermined time length and performing an FFT; a mapping unit that maps a magnetic field intensity of a specific frequency of the frequency domain data at each of the measurement points for the section of the predetermined time length after a specific time has elapsed since the detection of the trigger; The conduction noise visualization device according to (Configuration Example 12).

[0224] (Configuration Example 14) the display control unit causes the display unit to combine an image showing the measurement points with an image of the circuit under test in chronological order of the measurement times. The conduction noise visualization device according to any one of (Configuration Example 1) to (Configuration Example 13).

[0225] For example, it is also possible to provide a method of processing performed in a conducted noise visualization device. (Configuration Example 15) a trigger detection unit that detects a trigger based on a switching operation of the circuit under test; a magnetic field strength measuring unit measures a magnetic field strength at each measurement point arbitrarily set on the circuit under test for each measurement time arbitrarily set from the time point when the trigger detected by the trigger detecting unit is detected; a storage unit stores data of the magnetic field strength measured at each of the measurement points by the magnetic field strength measurement unit for each of the measurement times in association with the corresponding measurement point and the measurement time; A conduction noise visualization method, wherein a display control unit displays information about the measurement results at the measurement points on a display unit, a phase detection unit detects that a specific phase has a period longer than the period of the switching operation of the circuit under test; the trigger detection unit detects the trigger as a timing when the switching operation is being performed and close to the phase detected by the phase detection unit. Conducted noise visualization method. [Explanation of symbols]

[0226] 301, 401, 601, 801... Conduction noise visualization processing unit, 331, 631... Power amplifier, 332, 632... Transformer, 333, 432, 633, 832... LISN, 334, 634... Resistor, 335, 635... Arbitrary waveform generator, 336... D flip-flop, 337, 435, 637, 835... Magnetic field probe unit, 338, 436, 638, 836... Oscilloscope, 431, 831... DC regulated power supply ,711...NOT, 712, 715...AND, 713~714...Delay unit, 716...D flip-flop, 717...RS flip-flop, 911...Bus converter, 921, 931...Converter, 922...MPU, 932...GPU, A1...Conductive noise visualization device, A11...Input / output unit, A12...Memory unit, A13, 434, 636, 834...Trigger detection unit, A14...Phase detection unit, A15...Magnetic field strength measurement unit, A 16...Display unit, A17...Control unit, A31...Arbitrary waveform generator, A51...Magnetic field probe, A52...Probe movement unit, A53, 339, 437, 639, 837...Signal processing unit, A71...Data conversion unit, A72...Mapping unit, A91...Display control unit, B1, B2, 311, 411, 611, 811...Circuit under test (DUT), B11, 531 to 532, 541 to 542, 551 to 552...Switching element, C1... First switching power supply circuit, C2...Second switching power supply circuit, CM...Mth switching power supply circuit, G1...Power supply, G2, 433...Motor, Mg1...Magnetic field strength, R1 to R2, R21 to R23...Period, R11...Frequency band, Sf1...Measurement result conversion signal, Sg1 to Sg4, Sg11, Sg21 to Sg26, Sg31, Sg51 to Sg55, Sg71, Sg81, U1, V1, W1...Signal, St1...Measurement result signal

Claims

1. a trigger detection unit that detects a trigger based on a switching operation of the circuit under test; a magnetic field strength measuring unit that measures a magnetic field strength at each measurement point arbitrarily set in the circuit under test for each measurement time arbitrarily set from the time point at which the trigger detected by the trigger detecting unit is detected; a storage unit that stores data of the magnetic field strength measured at each of the measurement points by the magnetic field strength measurement unit for each of the measurement times in association with the corresponding measurement point and the measurement time; a display control unit that causes information about the measurement results at the measurement points to be displayed on a display unit; A conduction noise visualization device comprising: a phase detection unit that detects a specific phase having a period longer than the period of the switching operation of the circuit under test, the trigger detection unit detects the trigger as a timing when the switching operation is being performed and close to the phase detected by the phase detection unit. Conduction noise visualization device.

2. the circuit under test is an AC-DC converter, the phase detection unit detects a specific phase of the AC voltage input to the circuit under test. The conduction noise visualization device according to claim 1 .

3. the circuit under test is a DC-AC inverter, the phase detection unit detects a specific phase of the AC voltage output from the circuit under test. The conduction noise visualization device according to claim 1 .

4. the trigger detection unit includes a D flip-flop, inputs the timing of a specific phase detected by the phase detection unit as a phase detection trigger to a D input terminal of the D flip-flop, inputs a signal based on the switching operation to a clock input terminal of the D flip-flop, and uses a signal output from a Q output terminal of the D flip-flop as the trigger; The conduction noise visualization device according to claim 1 .

5. the phase detection unit detects the phase of the period of the voltage or current input to the circuit under measurement, the phase of the period of the voltage or current output from the circuit under measurement, or the phase of the period of the voltage or current generated inside the circuit under measurement. The conduction noise visualization device according to claim 1 .

6. the phase detection unit includes an arbitrary waveform generator; the arbitrary waveform generator generates a sinusoidal voltage signal and a phase detection trigger for any phase of the sinusoidal voltage signal; the phase detection unit amplifies the sine wave voltage signal and inputs it to the circuit under test as an AC voltage, and detects the trigger based on the phase detection trigger and a switching operation. The conduction noise visualization device according to claim 2 or 4.

7. the magnetic field strength measurement unit has a magnetic field probe that measures the magnetic field strength, and a probe movement unit that moves the magnetic field probe in accordance with the circuit under test, and moves the magnetic field probe to each of the measurement points arbitrarily set on the circuit under test by the probe movement unit, and measures the magnetic field strength at each of the measurement points for each of the measurement times arbitrarily set from the time point at which the trigger detected by the trigger detection unit is detected, a period of the phase detected by the phase detection unit is shorter than a time required for the probe movement unit to move the magnetic field probe between two measurement points that are adjacent in order; The conduction noise visualization device according to claim 1 .

8. the circuit under test is configured with a plurality of switching power supply circuits including a first switching power supply circuit, and performs the switching operation asynchronously; the trigger detection unit detects the trigger based on the switching operation of the first switching power supply circuit and the phase detected by the phase detection unit. The conduction noise visualization device according to claim 1 .

9. the trigger detection unit detects the trigger only during a period in which a specific time has elapsed since the switching operation of the switching power supply circuits other than the first switching power supply circuit. The conduction noise visualization device according to claim 8.

10. a period of time after the specific time has elapsed since the trigger was detected, at a timing when the switching operation of the first switching power supply circuit is performed again, is set so that the switching operation of the switching power supply circuits other than the first switching power supply circuit is not performed; The conduction noise visualization device according to claim 9.

11. the storage unit stores the magnetic field strength data as time domain data in association with the corresponding measurement point and the measurement time; the magnetic field strength measuring unit measures the magnetic field strength within an arbitrarily set frequency band at each of the measurement points arbitrarily set in the circuit under test for each of the measurement times arbitrarily set from the time point at which the trigger detected by the trigger detecting unit is detected; The conduction noise visualization device according to claim 1 .

12. a data conversion unit that converts the time domain data stored in the storage unit from binary data to CSV data, and converts the CSV data into frequency domain data by applying a window function and performing FFT on the CSV data; The conduction noise visualization device according to claim 11.

13. the data conversion unit converts the time domain data stored at each measurement point arbitrarily set in the circuit under test for each measurement time arbitrarily set from the time point at which the trigger detected by the trigger detection unit was detected into the frequency domain data by multiplying the time domain data by the window function for each interval of a predetermined time length and performing FFT; a mapping unit that maps a magnetic field intensity of a specific frequency of the frequency domain data at each of the measurement points for the section of the predetermined time length after a specific time has elapsed since the detection of the trigger; The conduction noise visualization device according to claim 12.

14. the display control unit causes the display unit to combine an image showing the measurement points with an image of the circuit under test in chronological order of the measurement times. The conduction noise visualization device according to claim 1 .

15. a trigger detection unit that detects a trigger based on a switching operation of the circuit under test; a magnetic field strength measuring unit measures a magnetic field strength at each measurement point arbitrarily set on the circuit under test for each measurement time arbitrarily set from the time point when the trigger detected by the trigger detecting unit is detected; a storage unit stores data of the magnetic field strength measured at each of the measurement points by the magnetic field strength measurement unit for each of the measurement times in association with the corresponding measurement point and the measurement time; A conduction noise visualization method, wherein a display control unit displays information about the measurement results at the measurement points on a display unit, a phase detection unit detects that a specific phase has a period longer than the period of the switching operation of the circuit under test; the trigger detection unit detects the trigger as a timing when the switching operation is being performed and close to the phase detected by the phase detection unit. Conducted noise visualization method.

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