JP7125208B2 - NOISE ANALYSIS DEVICE AND NOISE ANALYSIS METHOD - Google Patents

Description

The present invention relates to a noise analysis device and a noise analysis method.

2. Description of the Related Art In recent years, in board design for electronic equipment, it has become very important to perform power integrity (PI) analysis and to design a board configuration that sufficiently suppresses noise generation. In particular, as electronic devices become more multi-functional, the circuit scale tends to increase, and power consumption increases, making designing an appropriate power supply a difficult task.

In Cited Document 1, the effects of decoupling due to resistance, capacitance, and inductance of the power supply and ground are reflected in the power supply current calculation while performing high-speed analysis, so that unnecessary radiation of LSI can be evaluated in a realistic time on simulation. We propose a method of analysis of unwanted radiation that can

JP-A-2002-164434

In order to perform noise analysis of a DCDC converter with high precision, for example, it is conceivable to perform analysis in cooperation with a circuit simulation analysis tool and an electromagnetic field simulation analysis tool. However, in circuit simulation analysis tools, it is difficult to obtain component data (for example, data in SPICE format) necessary for analysis. Moreover, even if it is possible to obtain it, the accuracy is poor and correct analysis may not be possible.

In addition, in the electromagnetic field simulation analysis tool, it is difficult to model the printed circuit board and the like in order to perform the analysis efficiently. For this reason, for example, in a DCDC converter, since the operating state of the switching circuit changes in a short cycle, it has been difficult to reproduce and sequentially analyze this operation.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a technique capable of easily analyzing noise in a DCDC converter.

In order to solve the above problems, the noise analysis device of the present invention includes:
an information acquisition unit that acquires circuit information of a device to be analyzed;
a closed circuit extraction unit that extracts information on a closed circuit including switching elements from the circuit information;
a replacing unit that converts the information of the closed circuit into equivalent closed circuit information by replacing the information of the switching element among the information of the closed circuit with information of the equivalent circuit;
an observation point setting unit that sets an observation point based on the equivalent closed circuit information;
a noise analysis unit that calculates the amount of noise when the circuit indicated by the equivalent closed circuit information is observed at the observation point;
Prepare.

The device to be analyzed may be a DCDC converter.

In the noise analysis device, the closed circuit extracting unit uses the closed circuit as a first closed circuit, and extracts information on a second closed circuit that is a closed circuit that includes the switching element and is different from the first closed circuit. extract from the information,
wherein the replacing unit replaces the information on the switching element with the information on the equivalent circuit in the composite circuit information obtained by adding the information on the second closed circuit in addition to the information on the first closed circuit, thereby obtaining the composite circuit information may be used as the equivalent closed circuit information.

In the noise analysis device, the replacement unit replaces the switching element with a current source as the equivalent circuit,
The noise analysis unit may calculate the amount of noise using data obtained by actually measuring the current flowing through the switching element in advance as data of the current supplied from the current source.

In the noise analysis device, the noise analysis unit may calculate the amount of noise with respect to information obtained by adding information of components other than the circuit of the device to be analyzed to the equivalent closed circuit information.

In the noise analysis device, the device to be analyzed includes an integrated circuit including the switching element,
The closed circuit extraction unit may extract a closed circuit including the integrated circuit from the circuit information.

In the noise analysis device, the noise analysis unit may calculate the amount of noise with respect to information obtained by adding information about noise entering from outside the device to be analyzed to the equivalent closed circuit information.

In order to solve the above problems, the noise analysis method of the present invention includes:
an information acquisition step of acquiring circuit information of a device to be analyzed;
a closed circuit extraction step of extracting information on a closed circuit including switching elements from the circuit information;
A replacing step of replacing the information of the switching element among the information of the closed circuit with the information of the equivalent circuit to make the information of the closed circuit equivalent closed circuit information;
an observation point setting step of setting an observation point based on the equivalent closed circuit information;
a noise analysis step of calculating a noise amount when the circuit indicated by the equivalent closed circuit information is observed at the observation point;
is executed by the computer.

In the noise analysis method, the device to be analyzed may be a DCDC converter.

In the noise analysis method, in the closed circuit extraction step, the closed circuit is defined as a first closed circuit, and information on a second closed circuit that includes the switching element and is different from the first closed circuit is obtained from the circuit. extract from the information,
In the replacing step, out of the composite circuit information obtained by adding the information about the second closed circuit in addition to the information about the first closed circuit, by replacing the information about the switching element with the information about the equivalent circuit, the composite circuit information may be used as the equivalent closed circuit information.

In the noise analysis method, in the replacement step, the switching element is replaced with a current source as the equivalent circuit;
The amount of noise may be calculated in the noise analysis step using data obtained by actually measuring the current flowing through the switching element in advance as the data of the current supplied from the current source.

In the noise analysis method, the noise amount may be calculated in the noise analysis step for information obtained by adding information on components other than the circuit of the device to be analyzed to the equivalent closed circuit information.

In the noise analysis method, the device to be analyzed includes an integrated circuit including the switching element,
In the closed circuit extraction step, a closed circuit including the integrated circuit may be extracted from the circuit information.

In the noise analysis method, the noise amount may be calculated in the noise analysis step for information obtained by adding information about noise entering from outside the apparatus to be analyzed to the equivalent closed circuit information.

In order to solve the above problems, the present invention may also be a noise analysis program for causing a computer to execute each step of the noise analysis method. The present invention may also be a storage medium storing the noise analysis program in a computer-readable manner.

ADVANTAGE OF THE INVENTION According to this invention, the technique which can analyze the noise of a DCDC converter simply can be provided.

It is a figure which shows the structure of a noise-analysis apparatus. It is a figure which shows the hardware constitutions of a noise-analysis apparatus. It is a figure which shows an example of the noise analysis method which concerns on this embodiment. It is a figure which shows an example of the input circuit information. It is a figure which shows an example of the closed circuit information which was extracted. It is a figure which shows an example of a DCDC converter. It is a figure which shows the equivalent closed circuit replaced by the equivalent circuit. It is a figure which shows the example which set the observation point to the equivalent closed circuit. A diagram showing the Z parameter calculated by the noise analyzer It is a figure which shows near-field noise distribution which the noise-analysis apparatus calculated. Diagram showing Z parameter and its allowable value It is a figure which shows the example which used the integrated circuit for the switching circuit. It is a figure which shows the equivalent closed circuit after replacement. FIG. 3 is a diagram showing an example using a step-up DCDC converter; It is a figure which shows the equivalent closed circuit replaced by the equivalent circuit. It is a figure which shows the example which used LSI for a switching circuit. It is a figure which shows the equivalent closed circuit after replacement. It is a figure which shows the example which extracted the 2nd closed circuit in addition to the 1st closed circuit. It is a figure which shows the replaced equivalent closed circuit. FIG. 11 is a diagram showing a noise analysis method according to Modification 2; FIG. 11 is a diagram showing a noise analysis method according to Modification 3;

<First embodiment>
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a diagram showing the configuration of a noise analysis device 10. As shown in FIG. This noise analysis apparatus 10 acquires circuit information of the DCDC converter 20, extracts a switching circuit from this circuit information, replaces the switching elements of this switching circuit with an equivalent circuit, and performs noise analysis. As a result, the noise analysis device 10 uses the DCD
The purpose is to enable simulation of noise generated from the C converter 20 in a short period of time.
<Device configuration>
The noise analysis device 10 includes an information acquisition unit 11, a closed circuit extraction unit 12, a substitution unit 13, an observation point setting unit 14, and a noise analysis unit 15, as shown in FIG.

The information acquisition unit 11 acquires at least circuit information of the DCDC converter 20 of the electronic device to be analyzed. Here, the circuit information is information that indicates the circuit of the DCDC converter 20, and is information that indicates the shape, specifications, and the like of the parts that constitute the circuit. For example, it is CAD (computer-aided design) data of the circuit. Examples of components that make up the circuit include a printed circuit board, wiring patterns formed on the printed circuit board, elements provided on the printed circuit board, and a power source that supplies power to the circuit. The circuit information includes, for example, the shape, layer structure, and material of the printed circuit board, the shape of the wiring pattern, the connection position with the element, and the specifications of the element (capacity, dimensions, electrical characteristics, etc.).

A closed circuit extractor 12 extracts information on a closed circuit including switching elements of a switching circuit from the circuit information.

The replacement unit 13 replaces the switching element information in the closed circuit information with the equivalent circuit information, thereby converting the closed circuit information into equivalent closed circuit information. For example, the replacement unit 13 replaces at least one of the switching elements included in the closed circuit with a current supply source (noise supply source), and uses information about the circuit after this replacement as equivalent closed circuit information.

The observation point setting unit 14 sets observation points for observing noise based on the equivalent closed circuit information. For example, in the closed circuit, observation points are set at a current source serving as a noise supply source and a location where noise is propagated to a current supply destination from this current source. Note that specific setting locations will be described later.

The noise analysis unit 15 calculates the amount of noise when the circuit indicated by the equivalent closed circuit information is observed at the observation point. As a method for calculating the amount of noise, a known analysis technique such as so-called PI simulation can be used, so detailed description thereof will be omitted.

FIG. 2 is a diagram showing the hardware configuration of the noise analysis device 10. As shown in FIG. As shown in FIG. 2 , the noise analysis device 10 is an information processing device (computer) having a CPU (Central Processing Unit) 101 , a memory 102 , an input/output IF 103 and a communication IF 104 that are interconnected by a connection bus 110 . A CPU 101 is a central processing unit that controls the entire information processing apparatus. CPU 101 is also called a processor. However, the CPU 101 is not limited to a single processor, and may have a multiprocessor configuration. Also, a single CPU 101 connected by a single socket may have a multi-core configuration.

Memory 102 includes a main memory and an auxiliary memory. The main memory is used as a work area for the CPU 101, a storage area for programs and data, and a buffer area for communication data. The main memory is formed by, for example, random access memory (RAM) or a combination of RAM and read only memory (ROM). The main storage device is a storage medium in which the CPU 101 caches programs and data and develops work areas. The main memory includes, for example, flash memory, RAM (Random Access Memory), and ROM (Read Only Memory). The auxiliary storage unit is a storage medium that stores programs executed by the CPU 101, operation setting information, and the like. Auxiliary storage devices are, for example, HDDs (Hard-disk Drives), SSDs (Solid State Drives), EPROMs (Erasable Programmable ROMs), flash memories, USB memories, memory cards, and the like. In this embodiment, circuit information, setting information, and the like are stored in part of the storage area of the auxiliary storage device, which is a non-volatile storage medium.

The input/output IF 103 includes a sensor and an operation unit connected to the noise analysis device 10, a disk drive for reading data from storage media such as CDs and DVDs, a reader/writer for reading and writing data from storage media such as memory cards, and a display. An interface that inputs and outputs data to and from equipment such as devices and printers. The communication IF 104 is an interface (communication module) that communicates with other devices via a communication line. In addition, each of the above components may be provided in plurality, or some components may not be provided.

In the noise analysis device 10, the CPU 101 executes an application program (noise analysis program) to perform the information acquisition unit 11, the closed circuit extraction unit 12, the substitution unit 13, the observation point setting unit 14, and the noise analysis unit shown in FIG. 15 functions as each processing unit. However, at least part of the processing of each processing unit may be provided by a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), or the like. again,
At least part of each of the above processing units may be a dedicated LSI (large scale integration) such as an FPGA (Field-Programmable Gate Array), or other digital circuits. again,
An analog circuit may be included in at least part of each processing unit.

<Noise analysis method>
Next, a noise analysis method executed by the noise analysis apparatus 10 of this embodiment will be described. FIG. 3 is a diagram showing an example of the noise analysis method according to this embodiment. The noise analysis apparatus 10 starts the process of FIG. 3 when the power is turned on or when the user performs an operation to instruct the start of the analysis process.

In step S<b>10 , the noise analysis device 10 acquires circuit information of the equipment to be analyzed including the DCDC converter 20 . For example, circuit information created by CAD is stored in a storage device in advance, and the circuit information is obtained by reading the information from the storage device. Also, it may be received from another device. Furthermore, the user may input part of the information by operating the operation unit. FIG. 4 is a diagram showing an example of input circuit information. Although FIG. 4 mainly shows the planar shape of the circuit, the circuit information also includes information indicating the substrate configuration on the back surface and between layers. In addition, the circuit information includes not only the shape but also attribute information such as the type and specifications of each component.

In step S20, noise analysis apparatus 10 extracts information on a closed circuit including switching elements of DCDC converter 20, which is estimated to generate a lot of noise, based on the circuit information. FIG. 5 is a diagram showing an example of the extracted closed circuit information, and FIG. 6 is a diagram showing an example of the DCDC converter 20. As shown in FIG. DCDC converter 20 shown in FIG. The DCDC converter 20 has an input capacitor C1, switching elements Qt and Qb, a coil L1, and an output capacitor C2. For convenience of explanation, FIG. 6 shows only main elements and omits some elements such as a control circuit that supplies control signals to the gates of the switching elements Qt and Qb.

The input capacitor C<b>1 has one end connected to the positive electrode of the power supply 21 and the other end connected to the negative electrode of the power supply 21 , that is, the GND line 23 . The switching element Qt has one terminal (drain) connected to the positive electrode of the power supply 21 and the other terminal (source) connected to one terminal (drain) of the switching element Qb and the coil L1. The switching element Qb has one terminal (drain) connected to one terminal (source) of the switching element Qt and the coil L1, and the other terminal (source) connected to the GND line.

The coil L1 has one end connected between the source of the switching element Qt and the drain of the switching element Qb, and the other end connected to the output capacitor C2. One end of the output capacitor C2 is connected to the coil L1 and the load 22, that is, the output end (positive electrode) of the DCDC converter, and the other end is connected to the load 22, that is, the output end (negative electrode) of the DCDC converter through the GND line 23. ing.

The noise analysis device 10 extracts from the circuit information the information of the circuit in which the switching elements, coils, and capacitors are connected as shown in FIG. Then, the input capacitor C1 provided on the input side and the wiring pattern connecting them are extracted as a closed circuit (switching circuit) (FIG. 5). The circuits in FIGS. 5 and 6 are examples, and the DCDC converter 20 may have other configurations, for example. Also, the switching element is not limited to a unipolar transistor, and may be a bipolar transistor.

In step S30, the noise analysis apparatus 10 replaces the information of the switching elements Qt and Qb among the information of the closed circuit with the information of the equivalent circuit. In this embodiment, the closed circuit includes two switching elements Qt and Qb, but the switching element Qb connected to the GND line 23 is dominant in the influence of noise. Therefore, the switching element Qb connected to the GND line 23 side is replaced with a current source (noise source) Qbe, and the switching element Qt connected to the positive electrode side is replaced with a wiring pattern Qte that conducts between the drain and the source. FIG. 7 is a diagram showing an equivalent closed circuit replaced with an equivalent circuit. Information indicating this equivalent closed circuit is referred to as equivalent closed circuit information. When the DCDC converter 20 has another configuration, the switching element connected to the GND line side is replaced with a current source, and the other switching element is replaced with a wiring pattern that conducts between the source and the drain. Also, when there is one switching element, it is replaced with a current source.

In step S40, noise analysis apparatus 10 sets an observation point for observing noise based on the equivalent closed circuit information. FIG. 8 is a diagram showing an example in which observation points are set in an equivalent closed circuit. The noise analysis device 10 sets the first observation points P1a and P1b at both ends of the current source Qbe, which is the source of noise in the closed circuit, for example. The noise analysis device 10 also sets second observation points P2a and P2b across the input capacitor C1 that propagates noise by accumulating or discharging power from the current source Qbe.

At step S50, the noise analysis apparatus 10 calculates the amount of noise when the equivalent closed circuit shown in FIG. 8 is observed at observation points P1a, P1b, P2a, and P2b. 9 is a diagram showing the Z parameter calculated by the noise analysis device 10, and FIG. 10 is a diagram showing the near-field noise distribution calculated by the noise analysis device 10. FIG.

In FIG. 9, the frequency of the current (sine wave) supplied from the current source Qbe is plotted on the horizontal axis, and the impedance is plotted on the vertical axis to indicate the magnitude of noise. When obtaining the radiation noise, obtain the Z11 parameter when observation is performed between the first observation points P1a and P1b, and when obtaining the radiation noise, obtain the first observation points P1a and P1b and Obtain the Z21 parameter when observation is performed between the points P2a and P2b.

The noise analysis device 10 also measures the amount of noise when the current is supplied from the current source Qbe, the amount of noise when this current flows through each wiring pattern, the amount of noise when the input capacitor C1 stores or discharges power, and the like. , the amount of noise generated in each component is obtained, and shown for each position, and a near-field noise distribution such as that shown in FIG. 10 is output.

Note that the current supplied from the current source Qbe is not limited to a sine wave, and actual measurement data may be used. For example, the current between the drain and the source of the switching element Qb may be measured in advance when the switching element Qb is operated at different frequencies, and the measured data may be used to calculate the amount of noise, that is, analyze the noise. This makes it possible to obtain more accurate analysis results.

In step S60, the noise analysis apparatus 10 determines whether the noise amount calculated in step S50 is acceptable, that is, whether the noise amount is suppressed to an allowable value or less. For example, as shown in FIG. 11, for the Z parameter, an allowable value (broken line in FIG. 11) 51 is set for each frequency, and if the amount of noise calculated in step S50 exceeds the allowable value 51, NG , it is determined to be OK (possible).

If the determination in step S60 is affirmative, the noise analysis apparatus 10 ends the processing of FIG. 3, and if the determination is negative, the process proceeds to step S70.

In step S70, the noise analysis apparatus 10 notifies the user that the amount of noise is an unacceptable value and prompts the user to make corrections. For example, as shown in FIG. 11, the noise analysis apparatus 10 obtains the frequency (600 MHz in FIG. 11) at which a noise peak exceeding the allowable value 51 appears, and displays the neighborhood noise distribution of this frequency to determine which The noise propagates as shown, and it indicates from which point the noise is generated, that is, the point to be improved. As a result, for example, the user can change the wiring pattern by changing the width and length of the wiring pattern.

If the circuit information is changed by the user, the process of FIG. 3 is executed again to acquire the circuit information after the change, and the process is repeated until an affirmative determination is made in step S60.

This makes it possible to achieve a design in which the amount of noise is sufficiently suppressed. In the present embodiment, the switching circuit of the DCDC converter 20, which generates a lot of noise among electronic devices, is limited to the switching circuit, and the switching elements Qt and Qb are replaced with an equivalent circuit to analyze the noise. The generation amount can be calculated, and the noise can be analyzed in a short time.

FIG. 12 is a diagram showing an example of using an integrated circuit for a switching circuit. In FIG. 12, IC 52 is an integrated circuit containing a MOSFET (switching element). The IC 52 has a power input terminal Vin connected to the positive electrode of the power supply 21 , a switching terminal Lx connected to the coil L 1 , and a power GND terminal PG connected to the GND line 23 .

In this case, the noise analysis apparatus 10 acquires circuit information in step S10 in the same manner as described above, and in step S20, the input capacitor C1, the IC 52, and the wiring pattern connecting them are regarded as a closed circuit (switching circuit). Extract.

In step S30, the noise analysis device 10 replaces the switching terminal Lx where the switching element Qb in the IC 52 is arranged and the power GND terminal PG with the current source Qbe. Also, the wiring pattern Qte replaces the power input terminal Vin where the switching element Qt is arranged and the switching terminal Lx. FIG. 13 is a diagram showing an equivalent closed circuit after replacement. The information on the portion to be replaced with the current source Qbe and the wiring pattern Qte is included in the circuit information as attribute information of the IC 52 .

In step S40, the noise analysis device 10 sets first observation points P1a and P1b at the switching terminal Lx and the power GND terminal PG, and sets second observation points P2a and P2b at both ends of the input capacitor C1. Steps S50 to S70 are the same as described above.

As described above, even when an integrated circuit is used as a switching circuit, noise can be analyzed in a short time by replacing it with an equivalent circuit as described above.

FIG. 14 is a diagram showing an example using a step-up DCDC converter 20A. DCDC converter 20A shown in FIG.

The DCDC converter 20A has a coil L2, switching elements Qt and Qb, and an output capacitor C2. In addition, in FIG. 14, for convenience of explanation, only main elements are shown, and some elements are omitted.

The coil L2 has one end connected to the positive electrode of the power supply 21 and the other end connected between the source of the switching element Qt and the drain of the switching element Qb. The switching element Qt has one end connected to the output capacitor C2 and the load 22, that is, the output terminal (positive electrode) of the DCDC converter, and the other end connected to one terminal (drain) of the switching element Qb. The switching element Qb has one terminal (drain) connected to one terminal (source) of the switching element Qt and the coil L1, and the other terminal (source) connected to the GND line.

One end of the output capacitor C2 is connected to the drain of the switching element Qt and the load 22, i.e., the output end (positive electrode) of the DCDC converter, and the other end is connected to the load 22, i.e., the output end (negative electrode) of the DCDC converter, via a GND line 23. is connected with

The noise analysis device 10 acquires circuit information in step S10 as described above. In step S20, the noise analysis apparatus 10 extracts from the circuit information the information of the circuit in which the switching elements, coils, and capacitors are connected as shown in FIG. Among them, the switching elements Qt and Qb, the output capacitor C2 provided on the output side, and the wiring pattern connecting them are extracted as a closed circuit (switching circuit).

In step S30, the noise analysis apparatus 10 replaces the information of the switching elements Qt and Qb among the information of the closed circuit with the information of the equivalent circuit. This replacement is the same as in the example of FIG. The switching element Qt connected to the side is replaced with a wiring pattern Qte that conducts between the drain and the source. FIG. 15 is a diagram showing an equivalent closed circuit replaced with an equivalent circuit.

In step S40, noise analysis apparatus 10 sets an observation point for observing noise based on the equivalent closed circuit information. For example, the noise analysis device 10 sets the first observation points P1a and P1b at both ends of the current source Qbe, which is the source of noise in the closed circuit. The noise analyzer 10 also sets second observation points P2a and P2b across the output capacitor C2 that propagates noise by accumulating or discharging power from the current source Qbe.
As described above, even when the DCDC converter 20A different from the above-described example (FIG. 6) is used, the noise can be analyzed in a short time by similarly replacing it with an equivalent circuit.

FIG. 16 is a diagram showing an example using an LSI for a switching circuit. In FIG. 16, LSI 53 is an integrated circuit containing a MOSFET (switching element). The LSI 53 has a power input terminal VDD connected to the coil L1 and a GND terminal VSS connected to the GND line 23 . The capacitors C3 and C4 have one ends connected between the power supply input terminal VDD of the LSI 53 and the coil L1, and the other ends connected to the GND line 23 .

The noise analysis apparatus 10 acquires circuit information in step S10 in the same manner as described above, and in step S20 extracts the LSI 53, the output capacitor C2, and the wiring pattern connecting them as a closed circuit (switching circuit).

In step S30, the noise analysis apparatus 10 replaces the power supply input terminal VDD-GND terminal VSS where the switching element Qb in the LSI 53 is arranged with the current source Qbe. FIG. 17 is a diagram showing an equivalent closed circuit after replacement. Information on the portion to be replaced with the current source Qbe is included in the circuit information as attribute information of the LSI 53 .

In step S40, the noise analysis apparatus 10 sets first observation points P1a and P1b at the power supply input terminal VDD and the GND terminal VSS. The noise analysis device 10 also sets second observation points P2a and P2b across the output capacitor C2 that propagates noise by accumulating or discharging power from the current source Qbe based on the equivalent closed circuit information. It should be noted that which of the capacitors C2 to C4 the second observation points P2a and P2b are to be set can be specified by the layout and specifications of each capacitor indicated in the circuit information. For example, it is set at both ends of the element that generates the most noise in the closed circuit. Steps S50 to S70 are the same as described above.

As described above, even when an LSI is used for the switching circuit, the noise can be analyzed in a short time by replacing it with an equivalent circuit in the same manner as described above.

<Modification 1>
In the above-described embodiment, in step S20, one closed circuit is extracted as shown in FIG. 7, but not limited to this, a plurality of closed circuits may be extracted. Since other configurations are the same as those of the above-described embodiment, repetitive description is omitted.

For example, the noise analysis device 10 of the present embodiment uses the closed circuit including the switching element Qb and the input capacitor C1 as the first closed circuit, and the closed circuit including the switching element Qb and different from the first closed circuit. Closed circuit information is extracted from the circuit information. FIG. 18 shows an example of extracting the second closed circuit including the switching element Qb, the output capacitor C2, the coil L1, and the wiring pattern connecting them in addition to the first closed circuit.

In step S30, the noise analysis device 10 replaces the information of the switching element Qb with the information of the equivalent circuit (current source Qbe) in the composite circuit information obtained by adding the second information in addition to the information of the first closed circuit. Thus, the composite circuit information is used as equivalent closed circuit information. FIG. 19 is a diagram showing the replaced equivalent closed circuit. Steps S40 to S70 after performing noise analysis using this equivalent closed circuit information are the same as described above. In this example, two closed circuits are extracted, but a plurality of second closed circuits are extracted, three or more closed circuits are extracted, and noise analysis is performed using these equivalent closed circuit information. good too.

By extracting a plurality of closed circuits in this manner, noise analysis can be performed in a wide range.

<Modification 2>
In the above-described embodiments, noise analysis was performed based on circuit information, but noise analysis may be performed by adding information on components other than the circuit. Since other configurations are the same as those of the above-described embodiment, the description thereof will be omitted.

FIG. 20 is a diagram showing a noise analysis method according to Modification 2. In FIG. Note that steps S10 to S40 are the same as in the example of FIG. 3 described above.

In step S45, the noise analysis apparatus 10 adds information on components other than the circuit of the electronic device to the equivalent closed circuit information. Components other than circuits include, for example, housings, chassis,
It is something that exists around the circuit, such as a shield. Information such as the shape, position, and material of these components is added to the equivalent closed circuit information.

In step S50, the noise analysis device 10 performs noise analysis on the equivalent closed circuit information to which the information on the constituent elements is added in step S45, and calculates the amount of noise.

As a result, noise analysis can be performed in a state close to a real machine in which components such as a housing are present.

<Modification 3>
In Modification 2 described above, noise analysis is performed by adding information on components other than the circuit, but noise analysis may be performed by adding information on noise entering from the outside. Since the rest of the configuration is the same as that of Modified Example 2 described above, repetitive description will be omitted.

FIG. 21 is a diagram showing a noise analysis method according to Modification 3. As shown in FIG. Note that steps S10 to S45 are the same as in the example of FIG. 20 described above.

In step S47, the noise analysis apparatus 10 reads out information on noise entering from outside the DCDC converter or the electronic device from the storage device and adds it to the equivalent closed circuit information. As for the information on the noise entering from the outside, the noise entering the electronic device from the outside is actually measured in advance and stored in the storage device.

In step S50, the noise analysis apparatus 10 performs noise analysis on the equivalent closed circuit information to which the information of the noise entering from the outside is added in step S47, and calculates the amount of noise.

Accordingly, noise analysis including the influence of the external environment can be performed. In addition, in this modified example 3, the process of step S47 is added to the process of FIG. 20 according to the modified example 2, but the configuration is not limited to this, and the process of FIG. , and the process of adding information on components other than the circuit (step S45) may be omitted.

Although the embodiments of the present invention have been described above, they are merely examples, and the present invention is not limited to these. Various modifications are possible.

10: Noise analysis device 11: Information acquisition unit 12: Closed circuit extraction unit 13: Substitution unit 14: Observation point setting unit 15: Noise analysis unit 20: DCDC converter 20A: DCDC converter 21: Power supply 22: Load 23: GND line 51 : Allowable value 53 : LSI

Claims (8)

an information acquisition unit that acquires circuit information of a device to be analyzed;
a closed circuit extraction unit that extracts information on a closed circuit including switching elements from the circuit information;
a replacing unit that converts the information of the closed circuit into equivalent closed circuit information by replacing the information of the switching element among the information of the closed circuit with information of the equivalent circuit;
an observation point setting unit that sets an observation point based on the equivalent closed circuit information;
a noise analysis unit that calculates the amount of noise when the circuit indicated by the equivalent closed circuit information is observed at the observation point;
A noise analysis device with 2. A noise analysis apparatus according to claim 1, wherein said apparatus to be analyzed is a DCDC converter. The closed circuit extracting unit uses the closed circuit as a first closed circuit, extracts information on a second closed circuit that is a closed circuit that includes the switching element and is different from the first closed circuit, from the circuit information;
wherein the replacing unit replaces the information on the switching element with the information on the equivalent circuit in the composite circuit information obtained by adding the information on the second closed circuit in addition to the information on the first closed circuit, thereby obtaining the composite circuit information 3. The noise analysis apparatus according to claim 1, wherein is the equivalent closed circuit information. the replacement unit replaces the switching element with a current source as the equivalent circuit;
4. The noise analysis unit according to any one of claims 1 to 3, wherein the noise analysis unit calculates the amount of noise using data obtained by actually measuring the current flowing through the switching element in advance as the data of the current supplied from the current source. noise analyzer. 5. The noise analysis unit according to any one of claims 1 to 4, wherein the noise analysis unit calculates the noise amount with respect to information obtained by adding information on components other than the circuit of the device to be analyzed to the equivalent closed circuit information. noise analyzer. The device to be analyzed comprises an integrated circuit including the switching element,
6. The noise analysis apparatus according to claim 1, wherein said closed circuit extraction unit extracts a closed circuit including said integrated circuit from said circuit information. 7. The noise analysis unit according to any one of claims 1 to 6, wherein the noise analysis unit calculates the amount of noise with respect to information obtained by adding information about noise entering from outside the device to be analyzed to the equivalent closed circuit information. noise analyzer. a step of acquiring circuit information of a device to be analyzed;
a step of extracting closed circuit information including switching elements from the circuit information;
A step of converting the information of the closed circuit into equivalent closed circuit information by replacing the information of the switching element with the information of the equivalent circuit among the information of the closed circuit;
setting an observation point based on the equivalent closed circuit information;
a step of calculating a noise amount when the circuit indicated by the equivalent closed circuit information is observed at the observation point;
a computer-implemented noise analysis method.

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