JP5705349B2 - Noise analysis design method and noise analysis design apparatus - Google Patents

Description

  The present invention relates to a noise analysis design technique for electrical devices, and more particularly to a technique that is effective when applied to an EMC (Electro Magnetic Compatibility) analysis design method such as an inverter for an automobile.

  According to a study by the present inventor, for example, techniques disclosed in Patent Documents 1 and 2 can be cited as noise analysis design techniques for electrical devices.

  In Patent Document 1, in an electromagnetic field analysis device that greatly reduces the amount of memory used by a computer and simulation calculation time, an error between an electromagnetic field calculation result by simulation and an actual electromagnetic field calculation result is minimized. Techniques for doing so are described.

  Patent Document 2 describes a wiring board design apparatus that performs various simulations such as waveforms, heat, timing, and electromagnetic radiation with high accuracy in designing a printed wiring board and a multichip module substrate.

JP 2006-209590 A Japanese Patent Laid-Open No. 9-245076

  By the way, as a result of examination by the present inventor regarding the noise analysis design technique of the electric device as described above, the following has been clarified. For example, in the above-mentioned Patent Document 1, simplification of the model is based on only the return current of vias (holes for conductive connection between layers of a multilayer board), and is not described between boards and between boards and cables. A part (main route) having a high contribution is not extracted. Moreover, the said patent document 2 is not described about speeding up of EMC simulation.

  In addition, in the noise analysis design technology for electric devices in the prior art, in the case of an automotive inverter, when EMC design is obtained by electromagnetic field analysis, for example, in the design of an inverter of a 100 kW class, to suppress the allowable leakage power below 1 nW or less, It is necessary to suppress the ratio of the two to 10 −14 or less, the analysis accuracy is required, and the calculation is not completed within the practical time even if the computer cost is increased.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a simulation technique for ending heat, vibration, and EMC multiphysics analysis in a practical time and at a low cost calculation process at an upstream stage of product design.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  That is, a typical outline is a noise analysis design method for an electric device such as an inverter for an automobile. The electric device includes one or more energy sources, a propagation path through which energy from the energy source propagates, and a propagation There is a noise generation site where electromagnetic radiation noise is generated by energy transmitted from the route, and using a computer, the route specified by the user is analyzed to estimate the generated noise such as the generated radiation noise. The path specified by the user is a path of energy flowing through the propagation path.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  That is, the effect obtained by the representative one can provide a simulation technique that can end the multi-physics analysis of heat, vibration, and EMC in a practical time and in a low-cost calculation process in the upstream stage of product design.

It is a figure for demonstrating the flow of the EMC design method which is one embodiment of this invention, and the structure of an EMC design apparatus. In one embodiment of the present invention, it is a diagram for explaining a detailed flow of the model equivalent circuit. In one embodiment of the present invention, it is a figure for demonstrating the design flow by multiphysics analysis. In one embodiment of the present invention, it is a diagram for explaining the structure of an inverter. In one embodiment of the present invention, it is a diagram for explaining the EMC design of the inverter for automobiles. In one embodiment of the present invention, it is a diagram for explaining a cross section of an inverter. FIG. 5 is a diagram for explaining an equivalent model for each element in an embodiment of the present invention. In one embodiment of the present invention, it is a diagram for explaining a model equivalent circuit of the inverter. In one embodiment of the present invention, it is a diagram for explaining the creation of a circuit constant database. In one embodiment of the present invention, it is a figure for explaining an input interface of an EMC design device.

<Outline of the embodiment>
An outline of a noise analysis design technique for an electric device according to an embodiment of the present invention will be described. In the present embodiment, circuit analysis is used to realize an EMC high-speed analysis technique.

  Since EMC is originally a problem of electromagnetic phenomena, it is common to solve electromagnetic field analysis, but in this embodiment, the idea of speeding up by analyzing it with an electric circuit is changed. Yes. The premise that this is possible is that the noise mechanism of the product is clear and the noise propagation path including parasitic components is clear. Thereby, an equivalent circuit in the EMC circuit analysis can be realized.

  The concept of this EMC circuit analysis is that, as a basic equation, E = SPA, that is, emission (E), which is radiation intensity, is a product of a source (S) of a noise source, a propagation path (P), and an antenna (A). This is based on the idea that In the inverter for automobiles, the mechanism of which part of the E = SPA corresponds to each part constituting the inverter is clarified. Then, by creating an equivalent circuit corresponding to this mechanism and performing circuit analysis, the electric field strength of EMC can be calculated.

  Hereinafter, an embodiment of the present invention based on the outline of the present embodiment will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

<Flow of EMC design method and configuration of EMC design apparatus>
FIG. 1 is a diagram for explaining the flow of an EMC design method and the configuration of an EMC design apparatus according to an embodiment of the present invention.

  Prior to circuit analysis, the EMC design method of this embodiment performs a template equivalent circuit (step 301), converts it into a circuit constant (step 308), and creates a circuit constant database (step 309). Thus, a circuit constant database is prepared in advance prior to circuit analysis.

  When this circuit constant database is prepared, first, noise source information and structure dimensions are input by the user (steps 302 and 303). An equivalent circuit is created based on the input information and information of a circuit constant database created in advance (step 304), and circuit analysis is performed (step 305). Then, the electric field strength is displayed (step 306), and the result of the circuit analysis is determined (step 307). If the target is not achieved as a result of this determination, the process returns to step 302, and the processing from step 302 to step 306 is performed. repeat. When the target is achieved as a result of the determination in step 307, the EMC design is finished. Here, prior to or simultaneously with the display of the electric field strength (step 306), the result of the circuit analysis (step 305) may be displayed in correspondence with the circuit diagram to clearly indicate the part that has not achieved the target. In this case, the user can easily estimate where in the circuit diagram the target unachieved part corresponds, that is, where in the structure.

  The EMC design method as described above is realized using a computer including a central processing unit and a storage device. That is, the EMC design apparatus according to the present embodiment uses a computer to execute a program describing the algorithm of the EMC design method stored in the storage device on the central processing unit, so that a template equivalent circuit can be realized. Function part, circuit part conversion function part, noise source information input function part, structural dimension input function part, equivalent circuit creation function part, circuit analysis function part, circuit A functional unit for determining the analysis result, a functional unit for displaying the electric field strength, and the like are constructed. In the EMC design apparatus, a circuit constant database is also built on the storage device.

<Detailed flow of model equivalent circuit construction>
FIG. 2 is a diagram for explaining a detailed flow of forming a template equivalent circuit in the present embodiment.

  In the template equivalent circuit formation in step 301 shown in FIG. 1, the main path of propagation is input by the user (step 3011). In this case, the user extracts the main path of propagation of electric energy and defines the main path of propagation. For example, in the case of an automotive inverter described later, this inverter has a propagation path through which energy from an energy source propagates, and a noise generation site where electromagnetic radiation noise is generated by energy transmitted from this propagation path. The path of flowing energy is defined as the main path of propagation.

  Based on the defined propagation main path, the propagation main path is divided (step 3012), and the divided parts are assigned to S (noise source), P (path), and A (antenna) (step 3013). ). That is, in order to obtain E (radiated electric field) by circuit analysis, each part of the product is classified as E = SPA. Then, a template equivalent circuit according to the E = SPA classification is created (step 3014).

  As described above, the template equivalent circuit is formed. Thereafter, the circuit constants in step 308 described above are performed, and in step 309 described above, a circuit constant database depending on the input shape is generated. Further, in the circuit analysis in step 305 described above, the radiation electric field is calculated based on the input shape.

<Design flow by multiphysics analysis>
FIG. 3 is a diagram for explaining a design flow by multiphysics analysis in the present embodiment.

  In the design flow based on multi-physics analysis, concept specifications are formulated based on market needs, and equipment is designed. In the inverter, at this stage, circuit design and structural design are performed based on the concept specification, and a rough structure of the component is determined so as not to be reversed from the viewpoint of heat, vibration, and EMC. After that, products are shipped in the flow of detailed design, trial manufacture evaluation, and mass production.

  In the device concept design stage, which is an upstream of the design, a plurality of structure plans in accordance with the heat rule, vibration rule, and EMC rule are extracted. This rule-based design can be roughly designed based on past accumulation. By analyzing each of the plurality of structure plans individually, it is possible to determine whether the structure plan can achieve each target.

  For example, even in the prior art, it is difficult to fully solve the thermal analysis and vibration analysis, but at the upstream stage of the design, a practical value can be obtained from the practical time by partially modeling the energy propagation main path. Can be calculated within.

  However, in the EMC analysis in the prior art, since quantitative analysis has not been performed, it has been impossible to select and narrow down one of a plurality of structure plans. That is, in the case of EMC analysis, it is necessary to handle a very large number of powers from 100 kW to 1 nW, and in order to calculate a leakage path of the order of 1 nW, it is necessary to handle parasitic components such as electrostatic coupling and inductive coupling. Therefore, it is necessary to analyze the entire space. Therefore, analysis of a huge mesh is required, and there is a difficulty that EMC analysis cannot be performed within a practical time.

  Therefore, the design flow of the present embodiment satisfies the EMC design as well as the thermal design and vibration design by enabling quantitative analysis of the EMC analysis at high speed from a plurality of structure plans obtained from the rule-based design. To be able to determine the structure plan to be That is, the goal in the design flow of the present embodiment is to realize high-speed EMC analysis that enables multiphysics quantitative analysis.

  In the design flow based on the above multiphysics analysis, the part of the EMC analysis of the structure plan based on the EMC rule is a part corresponding to the flow of the EMC design method shown in FIG. 1 and FIG.

<Inverter structure>
FIG. 4 is a diagram for explaining the structure of the inverter in the present embodiment.

  The inverter 100 is housed in a housing 101 and includes an LSI 102 on which a control circuit is formed, a substrate 103 on which the LSI 102 is mounted, two power modules 104, and a bus bar 105 connected to the power module 104. The motor cable 110 is connected to the bus bar 105, and the control cable 111 is connected to the substrate 103 on which the LSI 102 is mounted. The motor cable 110 and the control cable 111 are drawn out through openings 112 and 113 formed on the side surface of the housing 101, respectively. Although not shown, a ground plate is disposed on the back surface of the substrate 103.

  In the inverter 100, the power module 104 functions as one or more energy sources, the bus bar 105 and the control cable 111 function as a propagation path through which energy from the energy source propagates, and the control cable 111 transmits energy transmitted from the propagation path. It functions as a noise generation site where electromagnetic radiation noise is generated. In such an inverter 100, a path of energy flowing through the propagation path is designated by the user, and generated radiation noise is estimated by analyzing the path designated by the user.

<EMC design of inverters for automobiles>
FIG. 5 is a diagram for explaining the EMC design of the inverter for automobiles in the present embodiment.

  The inverter for automobiles includes the inverter 100 as shown in FIG. 4 described above, and a battery 150 is connected to the inverter 100. In addition, a motor cable 110 drawn from the inverter 100 is connected to a motor 170 that drives the tire 160, and a control cable 111 is connected to an ECU (Engine Control Unit) 180.

  In the case of an automobile, an inverter 100 that converts direct current from the battery 150 into alternating current is used to drive the tire 160 with the motor 170. Here, control signals for accelerating or decelerating the vehicle are transmitted from the ECU 180 to the inverter 100 via the control cable 111, and the inverter 100 performs torque control by pulse modulation in accordance therewith.

  Noise is generated during the pulse modulation of the inverter 100, which partially leaks to the outside, and noise radiation is generated therefrom. In order to prevent the electric field intensity at the electric field antenna from exceeding the regulation value, the allowable leakage power corresponds to 1 nW. On the other hand, the maximum output of the inverter 100 is a 100 kW class, and in order to suppress the output voltage below this allowable leakage power, a power suppression amount of 10 −14 or less, which is the ratio of the two, is required. That is, in the EMC design in which the leakage of the inverter 100 to the outside of the device is suppressed to reduce the radiation noise to a regulation value or less, there is a difficulty that the leakage power must be suppressed to 14 digits or less of the output.

  For this reason, in the prior art, as described above, the calculation was not completed within the practical time even when the computer cost was spent in this EMC design. However, in the present embodiment, the above-described FIG. 1 and FIG. By applying the EMC design method shown, the calculation process can be completed within a practical time and at a low price.

<Cross section of inverter>
FIG. 6 is a diagram for explaining a cross section of the inverter in the present embodiment.

  The cross section of the inverter 100 shown in FIG. 4 is as shown in FIG. As shown in FIG. 6, capacitive coupling occurs between the substrate 103 on which the LSI 102 is mounted and the bus bar 105 connected to the power module 104. Further, inductive coupling occurs between the substrate 103 and the ground plate, and conductive coupling occurs between the substrate 103 and the housing 101.

  In the inverter 100 having such a cross-sectional structure, there are the following methods for specifying a noise propagation path. For example, in the current analysis of the substrate 103, the distribution of the noise current flowing through the substrate 103 can be measured by scanning directly above the substrate 103 using a magnetic field sensor. Further, the current flowing between components such as the substrate 103 and the housing 101 can also be measured by using a screw current probe. This is a technique in which a coiled wiring is formed on a minute substrate so as to surround a screw connecting the substrate 103 and the housing 101, and a current flowing through the screw is measured. The technique of measuring the current distribution with a high-sensitivity magnetic field sensor on the surface of the housing 101 can also measure a standing wave of 3 GHz.

  With these measurement techniques, it is possible to specify the propagation path of the noise current unique to the product, which greatly depends on the mounting state. Next, the propagation path of the identified noise current is converted into an equivalent circuit by combining an equivalent model for each element as will be described later.

<Equivalent model for each element>
FIG. 7 is a diagram for explaining an equivalent model for each element in the present embodiment.

  When the noise current propagation path is converted into an equivalent circuit, the parasitic component or noise path specified as shown in FIG. 6 is converted into an equivalent circuit for each part as shown in FIG. For example, in the case of the power module 104, the equivalent expression is expressed by a current source having impedance as the element S (noise source). Further, the equivalent between the control cable 111 and the bus bar 105 that propagates large power is expressed by a capacitor as an element P1 (capacitive coupling by current). In addition, the equivalent between the substrate 103 and the ground plate is expressed by an inductor as an element P2 (inductive coupling by current). Further, in the case of a screw between the substrate 103 and the housing 101, it is equivalently expressed by a resistance as an element P3 (conductive coupling by a current flowing through the screw). In the case of the control cable 111, the antenna efficiency, which is the radiation efficiency of the antenna, is expressed by the subordinate power source as the element A (antenna by noise current).

  As described above, each noise path and part can be converted into an equivalent circuit. Next, by combining equivalent circuits for each element, one template equivalent circuit as described later is obtained.

<Inverter template equivalent circuit>
FIG. 8 is a diagram for explaining a model equivalent circuit of an inverter in the present embodiment.

  By combining the equivalent circuits for each element shown in FIG. 7 as described above, one template equivalent circuit can be obtained as shown in FIG. For example, the portion of the power module 104 can be represented by a current source having impedance. The portion of the bus bar 105 can be represented by an inductor. The portion of the motor 170 can be represented by an inductor and a capacitor. The control cable 111 can be represented by a spatial impedance of an antenna coefficient (power source) and a radiation electric field (E). The space between the control cable 111 and the bus bar 105 can be represented by a capacitor 201 by capacitive coupling. A space between the substrate 103 and the ground plate can be represented by an inductor 202 by inductive coupling. A space between the substrate 103 and the housing 101 can be represented by a resistor 203 by conductive coupling. Although power is actually supplied from the inverter 100 to the motor by three-phase AC, the model equivalent circuit may be described by a circuit network showing three-phase AC.

  Thus, the EMC mechanism of the inverter 100 can be represented by a model equivalent circuit. Next, the obtained template equivalent circuit is made into a circuit constant database as will be described later.

<Creation of circuit constant database>
FIG. 9 is a diagram for explaining the creation of a circuit constant database in the present embodiment.

  When the model equivalent circuit is made into a circuit constant database, the constant of the equivalent circuit changes depending on the position of the part and the dimension between the parts. Therefore, for example, as shown in FIG. 9, when calculating the parasitic capacitance C between the control cable 111 and the bus bar 105, first, in the cross-sectional structure, the distance h between the control cable 111 and the bus bar 105 and the width w of the bus bar 105 can be mounted. Find the right range. Within this mountable range, a constant is calculated using an analytical expression for coupling capacitance, a two-dimensional electromagnetic field analysis, and the like. Since the constant value has a value for the position of the control cable 111 and the bus bar 105, the relationship between C, h, and w can be used as a database for the mounting structure.

  Similarly, for inductive coupling between the substrate 103 and the ground plate and conductive coupling between the substrate 103 and the housing 101, a database corresponding to the dimensions of each structure can be created.

  EMC can be analyzed by performing circuit analysis using this circuit constant database.

<Input interface of EMC design equipment>
FIG. 10 is a diagram for explaining an input interface of the EMC design apparatus in the present embodiment.

  As described above, a model equivalent circuit for a noise propagation path of a product is created, and a circuit constant database is created. After that, by inputting the dimension information of the mountable range, it becomes possible to calculate the automatic citation of circuit constants, the creation of an equivalent circuit, circuit analysis, and the electric field strength of radiated noise as an output display.

  The input interface of this EMC design apparatus has an input screen as shown in FIG. For example, a noise source information input unit that inputs noise source information by a user includes input items of slew rate, high voltage battery voltage, surge voltage, switching frequency, and maximum current as power module waveform information. Also, in the dimension input part (propagation path / radiation part) for inputting the dimension of the structure, the bus bar structure (power module PM1) has a bus bar length, a bus bar width, P- There are input items for the distance between N and the distance to the control cable.

  From such an input screen, the rising and falling times of the noise waveform, the maximum current value, dimensional constraint information such as control cables and bus bars, and the like are input. By using this input interface, the EMC electric field strength can be calculated at a high speed on the order of several minutes per structure.

<Effect>
As described above, according to this embodiment, based on the main path of propagation of electrical energy defined by the user, the radiated electric field is obtained by circuit analysis, and each part of the product is divided into four parts of E = SPA. By classifying, making a template equivalent circuit according to this classification, creating a database of circuit constants depending on the input shape, and calculating the radiation electric field based on the input shape, EMC analysis becomes possible in a short time. Therefore, EMC of many structure plans can be evaluated by performing EMC analysis in a short time.

  Furthermore, in the case of performing thermal analysis and vibration analysis in addition to EMC analysis, since the structure is the same, there is an effect that a new input becomes unnecessary.

  As a result, it is possible to provide a simulation technique in which multi-physics analysis of heat, vibration, and EMC is completed in a practical time and at a low cost calculation process at an upstream stage of product design.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention relates to a noise analysis design technique for an electric device, and is particularly applicable to an EMC noise analysis design method for an inverter for an automobile.

DESCRIPTION OF SYMBOLS 100 ... Inverter, 101 ... Housing, 102 ... LSI, 103 ... Board, 104 ... Power module, 105 ... Bus bar, 110 ... Motor cable, 111 ... Control cable, 112, 113 ... Opening,
150 ... battery, 160 ... tyre, 170 ... motor, 180 ... ECU,
201 ... capacitor, 202 ... inductor, 203 ... resistance.

Claims (3)

In the noise analysis design method for electrical equipment,
Dividing a main path of propagation of designated electrical energy of an electrical device into parts;
Classifying each of the divided parts into elements;
Creating an equivalent circuit for each part based on the classification;
Calculating a circuit constant of the equivalent circuit and creating a circuit constant database;
The computer performs the step of calculating the electric field strength based on the input information of the electric device to be analyzed and the circuit constant database,
The element includes a noise source, a propagation path, and an antenna. In claim 1,
The information on the electric device to be analyzed includes information on a noise source and information on the dimensions of each part. In the noise analysis design device that analyzes the noise of electrical equipment,
Storage means having a circuit constant database in which the path of electric energy propagation of the electric device is converted into an equivalent circuit for each part, and data of an equivalent circuit including its elements and circuit constants is stored;
Computation means for calculating the electric field intensity generated by the electric energy propagation path of the electric device based on the input information of the electric device to be analyzed and the circuit constant database,
The element includes a noise source, a propagation path, and an antenna.