JP7063552B2 - Capacitor equivalent circuit construction method, simulation method and its equipment - Google Patents

Description

The present invention relates to a method for constructing an equivalent circuit of a capacitor, a simulation method, and an apparatus thereof. In particular, a method for constructing an equivalent circuit for a capacitor and a simulation method suitable for a case where a DC voltage (DC bias voltage) is superimposed and applied to a signal voltage. And its equipment.

Generally, a capacitor has frequency characteristics due to its material and structure, and deviates from the characteristics of an ideal capacitive element. Therefore, when calculating the characteristics of a capacitor with high accuracy using a simulator or the like, an equivalent circuit model that matches the frequency characteristics of the actually measured capacitor is required and is provided by each capacitor vendor.

However, in recent years, especially in multilayer ceramic capacitors, a model that expresses the characteristics when DC voltage is superimposed has become necessary, and a simulation model that incorporates only the frequency characteristics for signals without DC voltage into actual measurement cannot be used. It's coming.

As a method for improving such a problem, for example, there is a "capacitor circuit simulation model and its construction method, a circuit simulation method and a circuit simulator" disclosed in Patent Document 1 below, which uses a voltage control current source and direct current. When a voltage is applied to a capacitor, an equivalent circuit model that automatically flows a current corresponding to the characteristics corresponding to the applied DC voltage is presented. As a result, the characteristics at the time of DC voltage superimposition at the time of actual measurement can be reproduced with high accuracy.

Japanese Unexamined Patent Publication No. 2012-150579

However, in the above-mentioned background technique, as shown in FIG. 1, the circuit configuration includes an element for performing a differential operation, and since it is further developed over a large number as shown in FIG. 6, the actual calculation is performed. In that case, problems such as divergence may occur. Further, the approximation formula of the DC superimposition characteristic is a polynomial approximation, which may cause a problem of divergence. Further, since there are many complicated calculation formulas, the calculation load on the calculation software actually used becomes large, and as a result, the calculation takes time.

In addition, since the configuration of the equivalent circuit model is complicated, it takes a huge amount of man-hours and time to build a simulation model of one capacitor, and it is possible to build a simulation model if you are not technically familiar with it. However, there is also the inconvenience that it is difficult to secure engineers.

The present invention focuses on the above points, solves various practical problems caused by the complexity of the equivalent circuit model, and satisfactorily approximates the DC voltage superimposition characteristics with a simple configuration. It is an object of the present invention to provide a method for constructing a capacitor equivalent circuit, a method for simulating, and a device thereof, which can be used and have excellent practicality and workability.

The method of constructing the equivalent circuit of the capacitor of the present invention is a method of constructing the equivalent circuit of the capacitor in which the DC voltage may be superimposed on the signal and applied, and the DC voltage is not applied and only the signal is applied. In this state, the value of each circuit element included in the equivalent circuit is obtained from actual measurement to obtain a reference equivalent circuit, and the circuit element included in the reference equivalent circuit is a value obtained by superimposing a DC voltage. Step 2 of replacing the circuit element in which the voltage changes with a voltage control current source or a voltage control voltage source, and step 3 of adding a closed circuit expressing a state in which only a signal is applied to the replaced circuit element, and the closing. It is characterized by including step 4 of outputting a current or voltage having a value obtained by multiplying the current or voltage generated in the circuit element by the circuit by a coefficient from the voltage control current source or the voltage control voltage source.

One of the main forms is to compare the frequency characteristics of the circuit element actually measured in the state where the DC voltage is superposed on the signal and the frequency characteristics of the circuit element actually measured in the state where only the signal is applied. The current in the voltage control current source or the voltage control voltage source based on the step 5 for obtaining the change in the value of the circuit element due to the DC voltage superposition and the change in the value of the circuit element due to the DC voltage superimposition obtained in this step 5 . Alternatively, it is characterized by including step 6 in which an output of a coefficient multiple of the voltage value is performed.

In one of the other forms, in the closed circuit, a voltage source or a current source is connected in series with the circuit element replaced by the voltage control current source or the voltage control voltage source, and these voltage sources or current sources are connected. It is characterized in that the output of the voltage control current source or the voltage control voltage source is controlled based on the voltage or current applied to the closed circuit. Alternatively, when there are a plurality of circuit elements included in the reference equivalent circuit, the voltage control current source, the voltage control voltage source, or the closed circuit in which each circuit element is replaced is commonly grouped for the plurality of circuit elements. It is characterized by that. Further, the capacitor is a monolithic ceramic capacitor.

According to still another embodiment, the capacitor is a monolithic ceramic capacitor, and when the reference equivalent circuit is commonly grouped for a plurality of circuit elements, the frequency of the capacitance depending on the presence or absence of DC voltage superimposition in the monolithic ceramic capacitor. It is characterized by being composed of an equivalent circuit unit having a frequency characteristic corresponding to a change capacitance change rate and an equivalent circuit unit having a frequency characteristic corresponding to the lower limit capacitance value of the frequency change.
The simulation method of the present invention is characterized in that the characteristics of an electronic circuit including a capacitor of the equivalent circuit are obtained by a computer by using the equivalent circuit of the capacitor constructed by any of the above-mentioned construction methods.

The simulation apparatus of the present invention is characterized in that the equivalent circuit of the capacitor constructed by any of the above-mentioned construction methods is connected instead of the capacitor included in the circuit to be simulated, and the characteristics of the circuit to be simulated are calculated. do. The above and other objects, features and advantages of the present invention will be clarified from the following detailed description and accompanying drawings.

According to the present invention, an equivalent circuit when no DC voltage is applied is used as a reference, and a circuit showing a characteristic change due to DC voltage superimposition is added to the circuit elements included in the equivalent circuit. The calculation load is reduced, and calculation problems due to divergence are also reduced. In addition, changes in the characteristics of passive components when DC voltage is superimposed can be expressed relatively simply and with high accuracy.

It is explanatory drawing which shows the basic idea of Example 1 with respect to a capacitive element. It is explanatory drawing which shows the basic idea of Example 1 with respect to a resistance element. It is explanatory drawing which shows the other way of thinking of Example 1 with respect to a capacitive element. It is a circuit diagram which shows an example of the equivalent circuit when DC voltage is not applied. It is a graph which shows the frequency characteristic at the time of not applying a DC voltage, and at the time of superimposition. It is a graph which shows the change of the lower limit capacity value and the capacity change rate of the equivalent circuit element when the superimposing DC voltage is changed. It is a circuit diagram which shows the circuit structure when the equivalent circuit of FIGS. 1 and 2 is applied to the equivalent circuit part of FIG. It is a circuit diagram which shows the whole circuit composition when the equivalent circuit of FIGS. 1 and 2 is applied to the reference equivalent circuit of FIG. It is explanatory drawing which shows the basic idea of Example 2 of this invention. It is explanatory drawing which shows the method which put together the plurality of voltage control voltage sources connected to the equivalent circuit in Example 2. It is a circuit diagram which shows the equivalent circuit at the time of superimposing application of DC voltage in Example 2. It is a block diagram which shows the Example of the simulation apparatus of this invention.

Hereinafter, the best mode for carrying out the present invention will be described in detail based on examples.

First, Example 1 of the present invention will be described with reference to FIG. As shown in FIG. 1A, when the signal voltage Vac is applied between the terminals of the capacitance element C10 of the capacitance C, the signal current Iac shown by the equation 1 flows.

On the other hand, as shown in FIG. 3B, the capacitive element C10 in FIG. 6A is replaced with the voltage control current source E10, and the signal voltage Vac is copied to the voltage source E12. The capacitance element C10 and the monitor voltage source Vm for current monitoring are connected in series to the voltage source E12 to form a closed circuit. Since the monitor voltage source Vm does not affect the current characteristics of this closed circuit, this closed circuit is equivalent to the circuit shown in FIG. (A), and the signal current Iac shown in Equation 2 flows through the capacitive element C10. ..

This signal current Iac is monitored by the monitor voltage source Vm and fed back to the voltage control current source E10, and the voltage control current source E10 outputs the signal current Iac multiplied by the coefficient C ^* . By performing the above operation, the current I (E10) flowing between the terminals can be expressed by the equation (3). As is clear from the equations (3), the equivalent circuit of FIG. 1 (B) is equivalent to a circuit in which a capacitance element obtained by multiplying the capacitance C of the capacitance element C10 by C ^* is connected. In this way, by using the voltage control current source E10, it is possible to express the characteristics at the time of DC voltage superimposition.

As in the case of the capacitive element, it is possible to obtain an equivalent circuit obtained by multiplying the resistance by R ^* in almost the same procedure for the resistance element. That is, as shown in FIG. 2A, when the signal voltage Vac is applied between the terminals of the resistance element R10 having the resistance value R, the signal current Iac shown by the equation 4 flows.

On the other hand, as shown in FIG. 3B, the resistance element R10 in FIG. 6A is replaced with the voltage control current source E10, and the signal voltage Vac is copied to the voltage source E12. A resistance element R10 and a monitor voltage source Vm for current monitoring are connected in series to the voltage source E12 to form a closed circuit. Since the monitor voltage source Vm does not affect the current characteristics of this closed circuit, this closed circuit is equivalent to the circuit shown in FIG. (A), and the signal current Iac shown in Equation 5 flows through the resistance element R10. ..

This signal current Iac is monitored by the monitor voltage source Vm and fed back to the voltage control current source E10, and the voltage control current source E10 outputs the signal current Iac multiplied by the coefficient R ^* (“divided”). By performing the above operation, the current I (E10) flowing between the terminals is represented by the equation 6. As is clear from this equation, the equivalent circuit in FIG. 2B is equivalent to a circuit in which a resistance element obtained by multiplying the resistance value R of the resistance element R10 by R ^* times (current is 1 / R ^* times) is connected. Become.

Further, it is also possible to construct an equivalent circuit in which the capacitance of the capacitance element C10 is multiplied by C ^* with the voltage control voltage source. As shown in FIG. 3A, the signal voltage Vac between the terminals of the capacitance element C10 of the capacitance C is expressed by the equation 7 with respect to the signal current Iac.

On the other hand, as shown in the figure (B), the capacitance element C10 in the figure (A) is replaced with the voltage control voltage source E20, and the monitor power supply Vm is connected in series. The signal current Iac monitored by this monitor power supply Vm is copied to the current source E22. A capacitive element C10 is connected in series to the current source E22 to form a closed circuit. This closed circuit is equivalent to the circuit shown in FIG. (A), and the signal current Iac shown by the equation 8 flows through the capacitive element C10.

Then, when the signal voltage Vac applied to the capacitive element C10 is fed back to the voltage control voltage source E20 and the voltage fed back by the voltage control voltage source E20 is multiplied by 1 / C ^* and output, the voltage between the terminals of the current source E22 is output. When is V (3,4), the monitor voltage source Vm has no effect, so the terminal voltage V (1,2) shown in Equation 9 is obtained, and as a result, the capacitance C of the capacitive element C10 is C ^*. A doubled equivalent circuit is obtained.

In the case of a resistance element, the output of the voltage control voltage source is multiplied by R ^* in the same procedure to obtain an equivalent circuit obtained by multiplying the resistance value of the resistance element by R ^* .

Utilizing such a relationship, the DC voltage Vdc of the capacitance element and the resistance element of the equivalent circuit (hereinafter referred to as "reference equivalent circuit") to which only the signal voltage Vac when the DC voltage Vdc is not applied (when no superimposition is applied) is applied. The capacitance change rate and resistance change rate due to superimposition are investigated in advance by actual measurement, and the voltage control current source (voltage control voltage source in FIG. 3 in FIG. 3) is connected in series to each element as described above. The DC voltage superimposition characteristic of the capacitor represented by the circuit can be expressed. That is,
a, The circuit constants of the capacitance element and the resistance element included in the reference equivalent circuit are obtained in advance by actual measurement.
b. Next, the values of the capacitance element and the resistance element in the state where the DC voltage Vdc is superimposed on the signal voltage Vac are obtained by actual measurement.
c. From the value of each element when the DC voltage Vdc = 0 in a and the value of each element when the DC voltage superimposition is applied (Vac + Vdc) in b, the capacitance change rate and resistance change rate due to DC voltage superimposition are obtained. ..
d. From each of the obtained rate of change, the current I (E ₁₀ ) is obtained by the above equations 3 and 6.
e, By connecting the voltage control current source E10 (voltage control voltage source E20 in FIG. 3) of the obtained current I (E ₁₀ ) instead of the capacitive element or resistance element in the reference equivalent circuit, the DC voltage Vdc can be obtained. It is possible to obtain an equivalent circuit when the signal voltage is superimposed on the Vac and applied.

FIG. 4A shows an example of a reference equivalent circuit to which the DC voltage Vdc is not applied. This reference equivalent circuit is known as FIG. 17 of Japanese Patent Application Laid-Open No. 2013-228997. In the figure, the capacitances Cm and C1 to C3 are connected in series, and the resistances RC1 to RC3 are connected in parallel to the capacitances C1 to C3, respectively. Further, the capacitance C0 is connected in parallel to the whole of these circuits. The above equivalent circuit unit QA is a capacitive part, and by replacing each element included in this with a voltage control current source that reflects the rate of change due to DC voltage superimposition, an equivalent circuit with DC voltage superimposition characteristics is obtained. be able to.

Resistance R0 is further connected in parallel and inductance L0 is connected in series to the equivalent circuit unit QA. Further, three series circuits in which the inductance Lm, the inductances L1 to L3, and the resistances RL1 to RL3 are connected in series are further connected in parallel, and this is connected in series with the inductance L0. The resistance Rdc is also connected in series. Then, a series circuit of the capacitance Ct and the resistance Rt is connected in parallel to the above circuit.

Here, eight circuit elements are present in the above-mentioned equivalent circuit unit QA, and the capacitance change rate and the resistance change rate at the time of DC voltage superposition of each element may be all investigated, but the work efficiency is not always good. I can't say. Therefore, in this embodiment, the frequency characteristics of some samples of the multilayer ceramic capacitor will be used.

FIG. 5 shows the frequency characteristics of a monolithic ceramic capacitor sample using a typical material when a small amplitude signal is applied. For example, the frequency characteristics when a small amplitude signal is applied are actually measured using several kinds of samples of the 22 μF multilayer ceramic capacitor manufactured by the applicant. The figure (A) shows the characteristics when the DC voltage is not applied, and the figure (B) shows the characteristics when the DC voltage is superimposed. The horizontal axis of the graph shows frequency (logarithm), and the vertical axis shows capacitance.

As shown in these solid line graphs GFa and GFb, it was found that the capacitor capacity decreases linearly with respect to the logarithm of frequency, and finally converges to that value with a certain capacity value as the lower limit. The graphs GLa and GLb of the chain line are straight lines indicating the decrease in capacity, and the lower limit values are GPa and GPb. As is clear by comparing these graphs, it can be seen that the slopes of the graphs GLa and GLb and the lower limit values GPa and GPb change between when the DC voltage Vdc is not applied and when the DC voltage Vdc is superimposed. In this way, the change in the frequency characteristics of the capacitance depending on the presence or absence of DC voltage superimposition of the multilayer ceramic capacitor is the change in the two parameters of the capacitance change rates ΔGLa and ΔGLb and the lower limit capacitance values GPa and GPb shown by the slopes of the graphs GLa and GLb. Characterized by.

Then, even for the equivalent circuit to which the DC voltage Vdc is superimposed and applied, it is sufficient if there is an element component corresponding to the capacitance change rates ΔGLa and ΔGLb and the lower limit capacitance values GPa and GPb, and FIG. 4 (A) shows. It is not necessary to check the rate of change in capacitance or resistance due to DC voltage superposition for each of the eight circuit elements included in the equivalent circuit unit QA shown in. In fact, the capacitance frequency characteristics of the monolithic ceramic capacitor when no DC voltage is applied are matched by the reference equivalent circuit, the circuit constant at that time is used as the reference, and then the equivalent circuit shown in FIG. 4 (B) is applied when the DC voltage is superimposed. By multiplying the constant of each element by the common rate of change according to the applied voltage in the parts QA1 and QA2, the equivalent circuit constant at the time of applying the DC voltage superimposition can be determined.

FIG. 5 (C) shows the situation. In the figure, the solid line graph GFA shows the measured capacitance frequency characteristics of the applicant's 22 μF multilayer ceramic capacitor when no DC voltage is applied, and the solid line graph GFB shows the measured capacitance of the capacitor when the DC voltage is superimposed. Shows frequency characteristics. The superimposed DC voltage Vdc is 1 [V]. As shown in these graphs, the superposition of the DC voltage Vdc reduces the capacitance change rate and the lower limit capacitance value, and the graph GFA becomes the graph GFB.

On the other hand, the dotted line graph GSA is a combination of the measured capacitance frequency characteristics when no DC voltage is applied by the reference equivalent circuit shown in FIG. Specific numerical examples of each circuit element are as follows.
Cm = 1.5718uF
C1 = 1uF
C2 = 0.52638uF
C3 = 0.001uF
RC1 = 36.345Ω
RC2 = 7.9335Ω
RC3 = 6.5488Ω

The capacitance value of the capacitance C0 of the equivalent circuit section QA1 is about 0.698 times, and the capacitance values of the capacitances Cm and C1 to C3 of the equivalent circuit section QA2 are about 0.48 times the circuit constants when no DC voltage is applied. The capacitive frequency characteristics obtained from the equivalent circuit when the resistance values of resistances RC1 to RC3 are multiplied by about 1 / 0.48 are shown in the dotted graph GSB. Comparing this with the graph GFB of the measured value, it can be seen that they are in very good agreement. Further, when the capacitance value of the capacitance C0 of the equivalent circuit section QA1 is changed, the lower limit capacitance value of the graph GSB (corresponding to the GPa and GPb) changes, and the capacitance values of the capacitances Cm and C1 to C3 of the equivalent circuit section QA2 are changed. Or, when the resistance values of the resistances RC1 to RC3 are changed, the capacitance change rate of the graph GSB (corresponding to the slope of the graphs GLa and GLb) changes. As described above, the characteristics of the equivalent circuit portion QA1 of the reference equivalent circuit of FIG. 4 substantially correspond to the lower limit capacitance value, and the characteristics of the equivalent circuit portion QA2 substantially correspond to the capacitance change rate.

The above-mentioned FIG. 5 shows a case where the superimposed DC voltage Vdc is 1 [V], but when the same processing is repeated by changing the value of the DC voltage Vdc, the DC voltage Vdc and the equivalent circuit unit QA1 and are repeated. The relationship with the rate of change of each circuit constant of each element included in QA2 can be obtained. In FIG. 6A, the calculated value including the measured value of the lower limit capacitance value with respect to the DC voltage Vdc is indicated by a circle, and in FIG. 6B, the actual measurement of the capacitance change rate with respect to the DC voltage Vdc is shown. The calculated values including the values are indicated by circles. FIG. 6A corresponds to the rate of change of the capacitance C0 of the equivalent circuit section QA1 (the rate of change with respect to the value when no DC voltage is applied), and FIG. It corresponds to the inverse of the rate of change of the capacitance value of C3 (the rate of change with respect to the value when no DC voltage is applied) and the rate of change of the resistance values of resistances RC1 to RC3.

When the graph of the measured value of FIG. 6 is shown by a mathematical formula, it becomes as follows. In the equation, Vpk, ζk, αk, βk are fitting coefficients.

Looking at this equation of several tens, the function is even function with respect to the DC voltage Vdc and is symmetric with respect to the inverse voltage, and there is no concern about divergence like a power series. Therefore, inconsistency in the calculation result on the simulator and the load at the time of calculation are unlikely to occur. In this way , by substituting the equivalent circuit units QA1 and QA2 with the voltage control current source described by using the equation tens, the rate of change of the circuit constant due to the application of DC voltage superimposition is generated by the superimposition of the DC voltage Vdc. It can represent the rate of change in capacitance and the rate of change in resistance.

Next, an application example of the equivalent circuit shown in FIGS. 1 and 2 will be described with respect to the equivalent circuit unit QA shown in FIG. 4 described above. For example, focusing on the equivalent circuit section QA2 shown in FIGS. 4 (B) to 7 (A), the capacitance values of the capacitances Cm and C1 to C3 are multiplied by C *, and the resistance values of the resistances RC1 to RC3 are multiplied by 1 / C *. Replace with the equivalent circuits of FIGS. 1 (B) and 2 (B), respectively. Originally, voltage control current sources corresponding to the rate of change should be connected to the parallel connection of the capacitance C1 and the resistance RC1, but this should be summarized. The set of the capacitance C2 and the resistance RC2 and the set of the capacitance C3 and the resistance RC3 are also summarized in the same manner, and the entire equivalent circuit portion QA2 is replaced with the voltage control current source E10.

By multiplying the feedback current by C ^* as in the case of a single element, the following equation 11 can be obtained according to Kirchhoff's law. In the same equation, Ici is the currents Icm, Ic1, Ic2, and Ic3 of the capacitances Cm, C1, C2, and C3, and IRci is the currents IRc1, IRc2, and IRc3 of the resistances RC1, RC2, and RC3. Since the voltage applied to each element Cm, C1 to C3, and RC1 to RC3 does not change, as a result, the effect of multiplying the current flowing through each element constituting the equivalent circuit unit QA2 by C ^* can be obtained. Therefore, in the equivalent circuit of FIG. 7 (B), the capacitance values of the capacitances Cm and C1 to C3 of the equivalent circuit section QA2 of the figure (A) are multiplied by C *, and the resistance values of the resistances RC1 to RC3 are multiplied by 1 / C *. It becomes an equivalent circuit, and it is possible to obtain an equivalent circuit having a simple configuration in which individual current sources are integrated without constructing an equivalent circuit using a current source for each element.

Similarly, when the equivalent circuit of FIG. 1B is applied to the equivalent circuit unit QA1, the equivalent circuit shown in FIG. 4 becomes as shown in FIG.

Next, the overall operation of this embodiment will be described.
a, Each circuit constant of the circuit element included in the reference equivalent circuit of FIG. 4 is determined based on the measured value of the frequency characteristic in the state where the DC voltage Vdc is not superimposed on the capacitor to be simulated.
b. Next, the frequency characteristics when the DC voltage Vdc is superimposed are actually measured, and the graph shown in FIG. 6 is obtained.
c, and the calculation of several tens of equations is performed from those graphs to determine the coefficients C ^* and R ^* of the voltage control current sources EC0 and ECm in FIG.
d. Next, when the DC voltage Vdc is superimposed, the circuit constant change corresponding to the superimposed DC voltage Vdc is generated by the output of the current I (E ₁₀ ) by the voltage control current sources EC0 and ECm.
e, The equivalent circuit of FIG. 8 is described in a spice model format suitable for, for example, a typical spice simulator (LTspice, PSpice), and a simulation is performed on the simulator using the spice model. Alternatively, after describing the circuit constant of each element of the equivalent circuit and the information of the constant change rate of the element of the capacitive part in the software for stand-alone or Web, the calculation method shown in the above embodiment is applied on the software. Then, the graph and data of each frequency characteristic at the arbitrary DC voltage of the target multilayer ceramic capacitor are presented, the search for the capacitor that satisfies the specified frequency characteristic at the arbitrary DC voltage, and the frequency characteristic when applied to a simpler equivalent circuit. Calculations, etc. may be performed.

As described above, according to the present embodiment, the signal current according to the DC voltage Vdc superimposed on the partial QA expressing the capacitance is based on the equivalent circuit when the DC voltage is not applied shown in FIG. The voltage control current sources EC0 and ECm that adjust the Iac are connected in parallel, and the applied signal current change corresponding to the change in the characteristics of the capacitor when DC voltage superimposition is applied is expressed by the voltage control current sources EC0 and ECm. .. As a result, the element expressing the capacitance in the reference equivalent circuit behaves like a variable element by applying DC voltage superimposition. At that time, the approximate expression (Equation 10) of the coefficient (C *, R *) used for the currents (Equation 3 and Equation 6) of the voltage control current sources EC0 and ECm reduces the calculation load during simulation. However, there is no calculation problem due to divergence within the working voltage. As a result, the characteristics of the monolithic ceramic capacitor when an arbitrary DC voltage superimposition is applied can be accurately and quickly expressed on the equivalent circuit. Further, since the configuration of the equivalent circuit is relatively simple, the work such as fitting in the creation of the equivalent circuit becomes easy, and the workability and efficiency of the creation of the equivalent circuit are improved.

Next, Example 2 of the present invention will be described with reference to FIGS. 9 to 11. As shown in FIG. 9A, assuming that a voltage control voltage source is connected in series to the capacitive element and a voltage Vs represented by the following equation 12 is applied by the voltage control voltage source, it is apparently C. It seems that the capacitance value of the capacitive element changes by the rate of change of ^* .

Similarly, as shown in FIG. 9B, assuming that a voltage control voltage source is connected in series to the resistance element and a voltage Vs represented by the following equation 13 is applied by the voltage control voltage source. Apparently, the resistance value of the resistance element changes by the rate of change of R ^* .

Utilizing such a relationship, the capacitance element of the reference equivalent circuit to which only the signal voltage Vac is applied when the DC voltage Vdc is not applied (when no superimposition is applied), the capacitance change rate and the resistance change due to the DC voltage Vdc superposition of the resistance element. By investigating the rate in advance by actual measurement and connecting a voltage control voltage source in series to each element as described above, the DC voltage superimposition characteristic of the capacitor represented by the reference equivalent circuit can be expressed. That is,
a, The circuit constants of the capacitance element and the resistance element included in the reference equivalent circuit are obtained in advance by actual measurement.
b. Next, the values of the capacitance element and the resistance element in the state where the DC voltage Vdc is superimposed on the signal voltage Vac are obtained by actual measurement.
c. From the value of each element when the DC voltage Vdc = 0 in a and the value of each element when the DC voltage superimposition is applied (Vac + Vdc) in b, the capacitance change rate and resistance change rate due to DC voltage superimposition are obtained. ..
d. From each of the obtained rate of change, the voltage Vs is obtained by the above equations 12 and 13.
e. By connecting a DC control voltage source of the obtained voltage Vs in series to the capacitive element or resistance element in the reference equivalent circuit, an equivalent circuit when the DC voltage Vdc is superimposed on the signal voltage Vac is obtained. be able to.

Next, the connection of the voltage control voltage source to the reference equivalent circuit of FIG. 4 will be described. First, for the equivalent circuit unit QA1, a voltage control voltage source DE1 having a voltage value to which the rate of change shown in the graph of FIG. 6A is applied to the equation 12 is connected to the capacitance C0. Next, focusing on the equivalent circuit unit QA2, there are three sets of parallel connections of the capacitances C1 to C3 and the resistances RC1 to RC3. The rate of change of each element of the equivalent circuit unit QA1 is common in capacitance, and the reciprocal of the reciprocal is the rate of change in resistance (see Equation 13). Therefore, when a voltage control voltage source in which the rate of change of the equation (10) is described is connected to each element of the parallel connection, the admittance Y as shown in the equation (14) below is obtained. In the same equation, C is the value of the capacitance connected in parallel, and R is the value of the resistance connected in parallel.

With reference to this number 14 equation, it corresponds to the admittance Y of the circuit in which the voltage control voltage source describing the rate of change of the capacitance is connected to the whole of the set of the parallel connection of the capacitance and the resistance. Therefore, the voltage control voltage sources of each set of parallel connections can be combined into one.

FIG. 10A shows the situation. Originally, the voltage control voltage sources DVC1 and DVRC1 corresponding to the rate of change should be connected to the parallel connection of the capacitance C1 and the resistance RC1, but these are summarized in the voltage control voltage source DV1. The same applies to the pair of capacitance C2 and resistance RC2 and the pair of capacitance C3 and resistance RC3.

Then, the voltage control voltage source of the equivalent circuit unit QA2 described above becomes DVm, DV1 to DV3 shown in FIG. 6B, and becomes a circuit in which four impedances having the same capacitance change rate are connected in series. The impedance due to the series connection of the voltage control voltage sources DVm and DV1 to DV3 having the same rate of change is as follows. Therefore, as shown in the figure, it can be seen that it is equivalent to connecting all the elements other than the voltage control voltage source and then connecting one voltage control voltage source DE2 in series.

Next, when the signal voltage Vac is detected by the voltage control voltage sources DE1 and DE2, it is necessary to remove the superposed DC voltage Vdc. Therefore, the input voltage (signal voltage Vac + superimposed DC voltage Vdc) of the reference equivalent circuit is supplied as a detection signal to the voltage control voltage sources DE1 and DE2 after the DC component is removed by a high-pass filter having an extremely low cutoff frequency. By adding such a filter circuit to the reference equivalent circuit of FIG. 4 together with the voltage control voltage sources DE1 and DE2, an equivalent circuit expressing the frequency characteristics when the DC voltage Vdc is superimposed can be obtained.

FIG. 11 shows an example thereof. In the equivalent circuit unit QA1, the voltage control voltage source DE1 is connected in series, and in the equivalent circuit unit QA2, the voltage control voltage source DE2 is connected in series. Further, in the filter circuit GB, a high-pass filter is configured by the series capacitance CP and the parallel inductance LP, and the signal voltage Vac is detected by the load RP. Further, the input side and the output side of the equivalent circuit are connected to the voltage control voltage source DE3, respectively, and the input voltage Vin and the output voltage Vout are supplied. The voltage control voltage source DE3 outputs the difference between the input voltage Vin and the output voltage Vout. Then, the extra DC voltage Vdc is removed from the difference by the high-pass filter, and the signal voltage Vac is detected by the load RP and supplied to the voltage control voltage sources DE1 and DE2, respectively.

Next, the overall operation of this embodiment will be described.
a, Each circuit constant of the circuit element included in the reference equivalent circuit of FIG. 4 is determined based on the measured value of the frequency characteristic in the state where the DC voltage Vdc is not superimposed on the capacitor to be simulated.
b. Next, the frequency characteristics when the DC voltage Vdc is superimposed are actually measured, and the graph shown in FIG. 6 is obtained.
c, and the calculation of several tens of equations is performed from those graphs to determine the coefficients C ^* of the voltage control voltage sources DE1 and DE2 in FIG. In this example, the voltage control voltage source DE2 is guaranteed to combine the coefficients by the equation 15. However, when the coefficients are individually determined (C ^* ≠ 1 / R ^* ), the voltage control voltage is described. Since the voltage sources cannot be combined like the source DE2, the voltage control voltage source is left connected in series to each element.
d. Next, when the DC voltage Vdc is superimposed, the signal voltage Vac is detected by the filter circuit QB in FIG. 11, and the output of the voltage Vs by the voltage control voltage sources DE1 and DE2 is a circuit corresponding to the superimposed DC voltage Vdc. A constant change is generated.
e, The equivalent circuit of FIG. 11 is described in a spice model format suitable for, for example, a typical spice simulator (LTspice, PSpice), and a simulation is performed on the simulator using the spice model. Alternatively, after describing the circuit constant of each element of the equivalent circuit and the information of the constant change rate of the element of the capacitive part in the software for stand-alone or Web, the calculation method shown in the above embodiment is applied on the software. Then, the graph and data of each frequency characteristic at the arbitrary DC voltage of the target multilayer ceramic capacitor are presented, the search for the capacitor that satisfies the specified frequency characteristic at the arbitrary DC voltage, and the frequency characteristic when applied to a simpler equivalent circuit. Calculations, etc. may be performed.

As described above, according to the present embodiment, the signal voltage according to the DC voltage Vdc superimposed on the partial QA expressing the capacitance is based on the equivalent circuit when the DC voltage is not applied shown in FIG. Voltage control voltage sources DE1 and DE2 that adjust Vac are connected in series, and the applied signal voltage change corresponding to the change in the characteristics of the capacitor when DC voltage superimposition is applied is expressed by the voltage control voltage sources DE1 and DE2. .. As a result, the element expressing the capacitance in the reference equivalent circuit behaves like a variable element by applying DC voltage superimposition. Voltage control at that time The approximate expression (Equation 10) of the coefficient (C *, R *) used for the voltage of the voltage sources DE1 and DE2 (Equation 12 and 13) reduces the calculation load during simulation. However, there is no calculation problem due to divergence within the working voltage. As a result, the characteristics of the monolithic ceramic capacitor when an arbitrary DC voltage superimposition is applied can be accurately and quickly expressed on the equivalent circuit. Further, since the configuration of the equivalent circuit is relatively simple, the work such as fitting in the creation of the equivalent circuit becomes easy, and the workability and efficiency of the creation of the equivalent circuit are improved.

Next, an embodiment of the simulation apparatus will be described with reference to FIG. The simulation device 100 of this embodiment is configured by a general computer system, and has an arithmetic processing unit 110 mainly composed of a CPU, an input unit 122 such as a keyboard, an output unit 124 such as a liquid crystal display, and a program memory. The configuration is such that 130 and a data memory 140 are connected. A simulation program 132 (for example, a SPICE simulator) is stored in the program memory 130. The data memory 140 stores a simulation target circuit 142 including a capacitor and a capacitor equivalent circuit 144 shown in FIGS. 8 to 11.

The simulation target circuit 142 corresponds to a circuit in which a DC voltage Vdc is superimposed and applied to a signal voltage Vac, for example, a power supply line of an arithmetic processing IC such as a CPU. The capacitor equivalent circuit 144 is prepared for each capacitor. For example, the equivalent circuits 144A, 144B, ... Of the model number XX manufactured by XX company. When the simulation program 132 is a SPICE simulator, the capacitor equivalent circuit 144 is provided as a SPICE file.

When it is instructed which model number of the capacitor to use as the capacitor included in the simulation target circuit 142, the equivalent circuit 144 of the corresponding capacitor is read from the data memory 140, and this is the simulation target circuit 142. It is connected to the position of the capacitor. Then, based on the circuit, the simulation program 132 of the program memory 130 is executed by the arithmetic processing unit 110, and a desired simulation is performed. By using the equivalent circuit when the DC voltage superimposition is applied as shown in FIGS. 8 to 11, the time required for the simulation can be shortened and the simulation can be efficiently performed with high accuracy.

As described above, according to this embodiment, the following effects can be obtained.
(1) Electronic component manufacturers and their trading companies provide customers with equivalent circuits for applying DC voltage superimposition to their various capacitors, or publish them on the company's homepage to customers who adopt their products. On the other hand, it is possible to improve the convenience in circuit design, and further, it can lead to the creation of product sales opportunities.
(2) Electronic equipment manufacturers and electronic circuit design companies can efficiently select the most suitable electronic components for the design circuit and accurately select electronic products by using the above-mentioned equivalent circuit when DC voltage superimposition is applied. It can be designed and the design time can be greatly reduced.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, the following are also included.
(1) The reference equivalent circuit shown in the above embodiment is an example, and the present invention can be applied to a reference equivalent circuit having various configurations.
(2) The numerical values and ratios of the circuit constants shown in the above embodiment are also examples, and are not limited in any way.
(3) In the above description, the case where the equivalent circuit using the voltage control current source E10 shown in FIGS. 1 and 2 is applied to the capacitance element and the resistance element included in the reference equivalent circuit has been mainly described, but instead, An equivalent circuit using the voltage control voltage source E20 shown in FIG. 3 may be used. Further, in the above embodiment, the case of the capacitive element and the resistance element included in the reference equivalent circuit has been described, but the same applies to the case of the inductor element.
(4) The present invention is a typical application example of a monolithic ceramic capacitor, but can be applied to an equivalent circuit of various capacitors.

According to the present invention, based on the equivalent circuit when no DC voltage is applied, a circuit showing the characteristic change due to the DC voltage superimposed on the signal is added, so that the calculation load at the time of simulation is reduced and the calculation load is reduced. , Calculation problems due to divergence, etc. are also reduced. Further, since the characteristic change of the circuit element at the time of superimposing the DC voltage can be expressed relatively simply and with high accuracy, it is suitable for the characteristic analysis of the multilayer ceramic capacitor and the like.

C0, C1 to C3, Cm, Ct, CP: Capacitance C10: Capacitive element E10: Voltage control current source E12: Voltage source E20: Voltage control voltage source E22: Current source L0, L1 to L3, Lm, LP: Inverter R0, RC1 to RC3, RL1 to RL3, Rdc, Rt, RP: Resistance R10: Resistance elements DE1, DE2, DE3, DVC1, DVRC1, DVm, DV1 to DV3: Voltage control Voltage source QA, QA1, QA2: Equivalent circuit section QB: Filter circuit Vac: Signal voltage Vdc: DC voltage Vin: Input voltage Vout: Output voltage Vm: Monitor voltage source 100: Simulation device 110: Arithmetic processing unit 122: Input unit 124: Output unit 130: Program memory 132: Simulation program 140: Data memory 142: Simulation target circuit 144, 144A, 144B, ...: Equivalent circuit of capacitor

Claims (8)

It is a method of constructing an equivalent circuit of a capacitor in which a DC voltage may be superimposed on a signal.
Step 1 to obtain a reference equivalent circuit by obtaining the value of each circuit element included in the equivalent circuit from actual measurement in a state where no DC voltage is applied and only a signal is applied.
Step 2 of replacing a circuit element included in the reference equivalent circuit whose value changes due to superimposition of a DC voltage with a voltage control current source or a voltage control voltage source.
Step 3 of adding a closed circuit expressing a state in which only a signal is applied to the replaced circuit element, and step 3
Step 4 and step 4 in which a current or voltage having a value obtained by multiplying the current or voltage generated in the circuit element by the closed circuit by a coefficient is output from the voltage control current source or voltage control voltage source.
A method of constructing an equivalent circuit of a capacitor, which comprises. The frequency characteristics of the circuit element actually measured in the state where the DC voltage is superimposed and applied to the signal are compared with the frequency characteristics of the circuit element actually measured in the state where only the signal is applied. Step 5 for finding the change in value and
Based on the change in the value of the circuit element due to the DC voltage superimposition obtained in step 5 , step 6 for outputting a coefficient double of the current or voltage value in the voltage control current source or voltage control voltage source.
The method for constructing an equivalent circuit of a capacitor according to claim 1, further comprising. In the closed circuit, the voltage source or the current source is connected in series with the circuit element replaced by the voltage control current source or the voltage control voltage source.
The capacitor according to claim 1 or 2, wherein the output of the voltage control current source or the voltage control voltage source is controlled based on the voltage or current applied to the closed circuit by these voltage sources or current sources. How to build an equivalent circuit. When there are a plurality of circuit elements included in the reference equivalent circuit, a voltage control current source, a voltage control voltage source, or a closed circuit in which each circuit element is replaced is grouped in common for a plurality of circuit elements. The method for constructing an equivalent circuit of a capacitor according to any one of claims 1 to 3, wherein the equivalent circuit of the capacitor is constructed. The method for constructing an equivalent circuit of a capacitor according to any one of claims 1 to 4, wherein the capacitor is a monolithic ceramic capacitor. When the capacitor is a multilayer ceramic capacitor and the reference equivalent circuit is commonly integrated for a plurality of circuit elements, it corresponds to the capacitance change rate of the frequency change of the capacitance depending on the presence or absence of DC voltage superimposition in the multilayer ceramic capacitor. The method for constructing an equivalent circuit of a capacitor according to claim 4 , wherein the equivalent circuit portion of the frequency characteristic and the equivalent circuit portion of the frequency characteristic corresponding to the lower limit capacitance value of the frequency change are configured. Equivalence of a capacitor, characterized in that the characteristic of an electronic circuit including the capacitor of the equivalent circuit is obtained by a computer by using the equivalent circuit of the capacitor constructed by the construction method according to any one of claims 1 to 6. Circuit simulation method. The equivalent circuit of the capacitor constructed by the construction method according to any one of claims 1 to 7 is connected in place of the capacitor included in the circuit to be simulated, and the characteristics of the circuit to be simulated are calculated. A simulation device for the equivalent circuit of the characteristic capacitor.

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