JP3388987B2 - Stationary analyzer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steady state analysis device, and more particularly to a circuit simulation in designing an analog circuit for communication.

[0002]

2. Description of the Related Art The periodic steady state of a nonlinear circuit to which a periodic input is applied can be obtained by performing transient analysis (numerical integration) until the time when the circuit reaches the steady state. However, depending on the circuit, there are circuits that require long-time integration or it is difficult to determine when the steady state is reached. As a method of accurately and rapidly calculating a periodic stationary solution for such a problem, there is a method of reference [1].

Reference [1]: TJAprilie and TNTrick, “St
eady-state analysis of nonlinear circuits with peri
odic inputs, ”Proc.IEEE, Vol.60, No.1, pp.108-114, Ja
n.1972. According to the method of reference [1], the value x (T) when numerically integrated is equal to the initial value x (0) for one cycle (cycle: T [sec]) from a certain initial value x (0). Is obtained by the Newton method.

Further, the method of the following document [2] utilizes a periodic stationary solution to calculate the frequency response of a periodic nonlinear circuit. Reference [2]: Makiko Okumura, Tustomu Sugawara and Hirosh
i Tanimoto, “AnEfficient Small Signal Analysis Me
thod of Nonlinear Circuits with TwoFrequency Excit
ations, ”IEEE Trans.Comput.-Aided Des. Integrated
Circuits Syst., Vol.9, No3, pp.225-235, Mar.1990.

[0005]

However, according to the method described in the above-mentioned document [1], the steady state can be calculated faster than the method of performing transient analysis for a long time depending on the circuit. Although the analysis can be obtained, there are cases where it takes a long time to calculate, or convergence fails and a steady solution cannot be finally obtained.

Further, one of the purposes for obtaining a periodic stationary solution is to obtain data necessary for analyzing a periodic nonlinear circuit, but the method shown in the document [2] cannot surely obtain a stationary solution. There were cases.

The present invention has been made by paying attention to such a problem, and an object of the present invention is to make it possible to reliably and accurately analyze a periodic stationary solution of a non-linear circuit that operates periodically, at a high speed. It is to provide an analysis device.

[0008]

In order to achieve the above object, the present invention provides a periodic circuit for a non-linear circuit that operates periodically.
It is preset in the steady state analysis device that calculates the steady state response.
The transient analysis of a predetermined period based on the parameters
Transient analysis means and, following this transient analysis, Newton's method
Analysis that performs steady analysis using iterative calculation
Means and the transient analysis process by the transient analysis means.
Determine if the road is in a transient or steady state
If it is determined that it is in a steady state with the determination means to determine
Is a steady state without repeating the Newton method.
And output means for outputting the solution .

[0009]

[0010]

According to the present invention, the steady analysis means is used.
Is Newton's method of variables in stationary analysis external?
Further comprising a designating means for designating
The analyzing means is the above-mentioned method specified by the specifying means.
A variable deciding means for deciding how to take variables of the Newton method
Including.

The present invention is also based on the above Newton method.
Convergence judgment to judge whether the result of iterative calculation has converged
Further comprising a determining means, and the steady state analyzing means includes the convergence
Iterative calculation by the Newton method by the judging means
If it is determined that the result of does not converge, the variable
The variable of the Newton method determined by the determining means is taken.
It further includes changing means for automatically changing the way.

The present invention is also based on the above Newton method.
Convergence judgment to judge whether the result of iterative calculation has converged
Further comprising a determining means, wherein the convergence determining means
Results of repeated calculation by Newton's method do not converge
If it is determined that the
The transient analysis is performed until a normal solution is obtained.

[0014]

Further, the output means of the present invention is the transient analysis.
And the process of the stationary analysis and the stationary solution finally obtained
Display means for displaying is included.

[0016]

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a stationary analysis device to which the present invention is applied. As shown in the figure, this steady state analysis device is composed of an input means 1, a transient analysis section 2, a steady state analysis section 3, and an output means 4. The transient analysis unit 2 includes a steady solution determination means 5, and the steady analysis unit 3 includes a Newton method convergence determination means 6.

The input means 1 includes a circuit configuration, connection, element value,
It is a means for inputting circuit information such as model parameter values and analysis conditions. In the input means 1, it is possible to specify some methods or parameters for assisting the convergence of the steady analysis. One is that the number of cycles for transient analysis can be specified before starting iterative calculation by Newton's method in steady state analysis. It is already known that starting the iterative calculation by the Newton method after performing the several-period transient analysis improves the convergence, but the appropriate period differs depending on the circuit, and the appropriate period depends on the circuit. Giving the cycle was not considered.

Therefore, in this embodiment, the designer can externally specify an appropriate cycle according to the circuit, for example, from the input means 1. If the designer does not specify the cycle from the outside, a predetermined numerical value is used as the default value. For example, the default value is 3 cycles. Three cycles is a value suitable for the most general circuits.

The above-mentioned steady solution determining means 5 determines whether or not the result has reached a steady solution in the process of transient analysis, and in the transient analysis before starting the iterative calculation by the Newton method, this steady solution is determined. When the solution determination means 5 determines that the steady solution is reached, the result is output as a steady solution without performing the Newton method. Here, it is assumed that the steady solution determination means 5 has reached a steady state when the following conditions are satisfied for all variables, for example.

[0021]

[Equation 1]

Here, the variable x may be, for example, the differential voltage of the capacitor and the branch current of the inductor, or the variable (node voltage, voltage source and inductor) of the circuit equation described in MNA (reference [3] below). Current) or a differential voltage between the capacitor branch current and the inductor.

Reference [3]: C.Ho, AERehli and P. Brennan,
“The modified nodal approach tonetwork analysi
s, ”IEEE Trans.Circuits Syst., Vol.CAS-22, No.6, pp.5
04-509, June 1975. ε in equation (1) is a parameter that is determined based on the allowable relative error, the absolute absolute error voltage, or the absolute absolute error current, and is different for all variables. Has a value. For example, the i-th variable x based on the allowable relative error
Determine ε _i for _i as follows.

[0024]

[Equation 2]

Allowable relative error or allowable absolute error voltage,
Alternatively, the allowable absolute error current can be specified by the input means 1. It is also possible to specify the value of ε, which is automatically determined internally, to be 1/10 or to be doubled.

Next, at the time when the above transient analysis is completed, if the steady solution has not been reached yet, the steady analysis unit 3 executes the iterative calculation by the Newton method. Further, when it is predicted that a steady solution will be obtained by the transient analysis, it is designated via the input means 1 that the transient analysis is performed until the steady solution is obtained without repeating the Newton's method from the beginning. You can In that case, the input means 1 designates the upper limit of how many cycles the transient analysis is performed. If the upper limit is not specified, a predetermined value (for example, 10
0) is used. When a stationary solution is obtained within the upper limit period,
The output means 4 outputs the resulting steady solution, the number of analyzed cycles, the calculation time, and the like. If a steady solution is not obtained even after analyzing the upper limit cycle, the output means 4 outputs that a steady solution has not been obtained, an intermediate result, the number of analyzed cycles, calculation time, and the like.

FIG. 2 shows the configuration of the stationary analysis unit 3,
It has a Newton's method variable determination means 7 and a Newton's method execution means 8 in steady state analysis. The input means 1 can externally specify how to take variables in the Newton method. It is known that it is not necessary to take all the variables in the circuit as the variables of the Newton method of steady state analysis. Document [1] describes a method for removing the parasitic capacitance of a nonlinear element, and document [4] below introduces a method for evaluating the Jacobian matrix of the Newton method in the first step of transient analysis.

Reference [4]: Makiko Kakizaki and Tsutomu Su
gawara, “A modified Newtonmethods for the steady-
state analysis, ”IEEE Trans.Comput.-Aided Des.Inte
grated Circuits Syst., Vol.CAD-4, No.4, pp.662-667, Oc
Since the effectiveness differs depending on the circuit, it is effective that these methods are specified by the user according to the target circuit.

The input unit 1 shown in FIG. Variable reduction method is not adopted,
That is, all state variables are Newton's method variables.
2. The parasitic capacitance of non-linear elements is excluded. 3. Determined by evaluating the Jacobian matrix. The method such as can be specified externally as an option.

The Newton's method variable determining means 7 determines a variable by the method designated by the input means 1 or by a predetermined method if not designated. However, when performing frequency analysis (AC analysis) (reference [2]) using the results of steady state analysis, the variable reduction method of the Newton method is not adopted, and steady state analysis is performed using all variables. This is a method necessary for highly accurate frequency analysis.

In the case of a self-excited system circuit, instead of using the input means 1 as a variable of the Newton method, the circuit variable to be excluded from the variables of the Newton method can be designated. The self-excited system has a problem that it does not converge if this circuit variable changes with each iteration of the Newton method. In that case, the user specifies a variable from the outside and fixes the circuit variable to be excluded from the variable to the specified variable, whereby the convergence is improved.

Further, as shown in FIG. 3, when the convergence determination means 6 of the Newton method determines that the iteration calculation by the Newton method is not repeated even after repeating a predetermined number of times, the convergence is determined via the output means 4. The intermediate result and the calculation time are output together with the error message (Case 1 in the figure). Alternatively, in the steady state analysis unit 3, the way of taking variables of the Newton method of the steady state analysis is changed, and the Newton method is performed again (Case 2 in the figure). Alternatively, the steady analysis is not performed, and the transient analysis is performed again in the transient analysis unit 2 until a steady solution is reached (Case 3 in the figure).

The convergence determining means 6 of the Newton method is
When the error of the iterative calculation by the Newton method satisfies the following expressions (2) and (1) for all variables, it is determined that the solution has converged to a stationary solution.

[0034]

[Equation 3]

Here, j represents the number of iterations of the iterative calculation by the Newton method. When the Newton's method convergence determining means 6 converges the iterative calculation by the Newton's method, or when the steady-state solution determining means 5 obtains a steady-state solution, the output means 4 outputs the steady-state solution, the number of convergences, and the transient. Outputs the analysis cycle, calculation time, etc. The output means 4 also has a function of displaying the result of the analysis. FIG. 4 shows an example of the display. Further, FIG. 5 shows an example in which only the periodic solution, that is, the portion indicated by the dotted line in FIG. 4 is displayed.

When the AC analysis and the noise analysis of the non-linear circuit which operates periodically are continuously performed, the output means 4 has information necessary for the analysis (numerical integration of the non-linear circuit linearized in the vicinity of the steady solution). The information of the equivalent circuit for each time interval, the spectral density of each noise source, etc.) are output. In addition, in the present embodiment, the result obtained by the steady analysis is saved in a file in case of performing AC analysis or noise analysis. As a result, when the analysis conditions of the AC analysis and the noise analysis are changed and the AC analysis and the noise analysis are repeatedly performed, it is not necessary to perform the steady analysis again.

[0037]

According to the present invention, it becomes possible to reliably and accurately analyze a periodic stationary solution of a nonlinear circuit that operates periodically with high speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing in detail the configuration of a steady state analysis unit.

FIG. 3 is a diagram for explaining processing when convergence fails in iterative calculation by the Newton method.

FIG. 4 is a diagram showing an example in which an intermediate result of analysis is displayed.

FIG. 5 is a diagram showing an example in which only periodic solutions are displayed.

[Explanation of symbols]

1 ... Input means, 2 ... Transient analysis part, 3 ... Steady analysis part, 4 ...
Output means, 5 ... Steady solution determination means, 6 ... Newton method convergence determination means, 7 ... Steady analysis Newton method variable determination means, 8 ... Newton method execution means.

Continuation of the front page (56) Reference JP-A-7-295959 (JP, A) JP-A-9-179895 (JP, A) JP-A-6-162128 (JP, A) JP-A-7-121578 (JP , A) Hiroshi Okawara, 4 others, Introduction of new steady-state analysis method to general-purpose circuit simulator, Hitachi Microcomputer Technical Report, Hitachi Microcomputer System, October 1, 1990, Vol. 4, No. 2, p. 84-90 (58) Fields surveyed (Int.Cl. ⁷ , DB name) G06F 17/50 662 JISST file (JOIS)

Claims (5)

(57) [Claims] 1. A periodic constant of a nonlinear circuit which operates periodically.
In a steady-state analyzer that calculates a normal response, a transient solution with a predetermined cycle is set based on preset parameters.
The transient analysis means for performing the analysis and the transient analysis followed by the Newton method
In the process of transient analysis by the transient analysis means and the transient analysis means that performs steady analysis using
Judgment whether it is in the state or in the steady state
Constant means and the Newton method when it is determined to be in a steady state.
Output means for outputting a stationary solution without performing repeated calculations
Steady-state analysis apparatus characterized by comprising the, the. 2. In the steady analysis by the steady analysis means
To specify how to take variables of Newton's method
The designating means is further provided, and the stationary analysis means is designated by the designating means.
A variable that determines how to take the variables of the Newton method by the method
Stationary according to claim 1, characterized in that it comprises a determining means.
Analyzer. 3. Iterative calculation by the Newton method
A convergence determination means for determining whether or not the result has converged is further provided.
The steady-state analysis means includes the convergence determination means,
The result of the iterative calculation by the Hutton method did not converge
Is determined by the variable determining means,
Automatically change how to take variables in the Newton method
The method according to claim 2, further comprising changing means.
Steady state analyzer. 4. An iterative calculation by the Newton method
A convergence determination means for determining whether or not the result has converged is further provided.
The convergence determination means provides the iteration by the Newton method.
If it is determined that the result of the return calculation has not converged,
Until the steady solution is obtained by the transient analysis means.
The constant according to claim 1, wherein the transient analysis is performed.
Regular analyzer. 5. The output means is configured to perform the transient analysis and the transient analysis.
Display the steady- state analysis process and the final steady-state solution
The display device according to claim 1, further comprising:
Regular analyzer.