JP4364754B2 - Electrode capacitor deterioration prediction method - Google Patents

Description

  The present invention relates to a method for predicting deterioration of an electrolytic capacitor for smoothing the output voltage of the power supply circuit used in a power supply circuit such as a switching regulator, and more particularly to a simple and practical method for predicting deterioration of an electrolytic capacitor. .

Conventionally, a smoothing electrolytic capacitor is used in a power supply circuit such as a switching regulator in order to reduce a ripple voltage in the output voltage. This electrolytic capacitor usually has a shorter life than other resistors, inductances, transformers, active components, etc. of the power supply circuit. For this reason, in most cases, the life of the electrolytic capacitor determines the life of the power supply circuit. Therefore, it is important to predict the life of the electrolytic capacitor of the power supply circuit.
As a method for predicting the life of the electrolytic capacitor, there is a method using a relationship in which the equivalent series resistance of the electrolytic capacitor increases in inverse proportion to the square of the decrease rate of the electrolytic solution of the electrolytic capacitor (see, for example, Non-Patent Document 1).
Specifically, first, the equivalent series resistance ESR of the electrolytic capacitor at 20 ° C. is calculated from the above relationship (step 101). Next, since this equivalent series resistance has temperature dependence, a relational expression between temperature and equivalent series resistance is obtained in advance experimentally. Then, from this relational expression, an equivalent series resistance ESR _hot when the temperature of the electrolytic capacitor rises due to heat generated by the use of the electrolytic capacitor is calculated (step 102), and the calculated equivalent series resistance ESR _hot and the equivalent series resistance ESR _hot are calculated. A temperature rise ΔT of the electrolytic capacitor is calculated from the amount of heat generated by the flowing current and the thermal resistance of the electrolytic capacitor (step 103). Next, the internal temperature T of the electrolytic capacitor is calculated from the calculated temperature rise ΔT and the ambient temperature (step 104). Next, the vapor pressure P (which is a function of the internal temperature T) of the electrolytic solution of the electrolytic capacitor is calculated using the calculated internal temperature T (step 105), and is constant using the calculated vapor pressure P. The amount of electrolyte loss V _l (which is a function of vapor pressure P) in a period (for example, 100 hours) is calculated (step 106).
Next, the remaining amount V of the electrolytic solution of the electrolytic capacitor is calculated using the calculated electrolytic solution loss amount _Vl . Next, the equivalent series resistance ESR of the electrolytic capacitor corresponding to the remaining amount V of the electrolytic solution of the electrolytic capacitor determined by the relationship that the equivalent series resistance of the electrolytic capacitor increases in inverse proportion to the square of the decrease rate of the electrolytic solution of the electrolytic capacitor. Is over a certain limit (three times the initial value) (step 107), the life of the electrolytic capacitor has been reached, so this life prediction is terminated. Steps 101 to 107 are repeated. In this way, the deterioration of the electrolytic capacitor is predicted.
Life prediction model of aluminum electrolytic capacitor Michael Gasperi Rockwell Advanced Technology Laboratory 1996 IAS Conf. Rec. Vol3. pp 1374-1351

However, in the above-described conventional example, the relational expression between the equivalent series resistance of the electrolytic capacitor and the temperature is experimentally obtained in advance, the calorific value when the electrolytic capacitor is used, the calculation of the temperature rise of the electrolytic capacitor, the electrolytic capacitor Complex procedures such as calculating the internal temperature of the electrolyte, calculating the vapor pressure of the electrolyte, calculating the amount of electrolyte loss, calculating the remaining amount of electrolyte, and predicting the equivalent series resistance corresponding to the remaining amount of electrolyte. There was a problem of becoming.
Therefore, the problem to be solved by the present invention is to predict the equivalent series resistance of the electrolytic capacitor for smoothing the output voltage of the power supply circuit by a simple and practical procedure so that the deterioration of the electrolytic capacitor can be predicted. It is.

In order to solve the above problem, the invention according to claim 1 is a method for predicting deterioration of an electrolytic capacitor, wherein the value ESR _o of the equivalent series resistance of the electrolytic capacitor measured at a reference time point and the reference time point The equivalent series resistance value ESR _{n of the} electrolytic capacitor measured after the elapse of N unit time such as N years is measured, and the measured ESR _o and ESR _n and the electrolytic capacitance of the electrolytic capacitor at the reference time point are measured. ESR _n / ESR _o = (V _o / V _n ) ² (1) Relationship between the amount of liquid V _o and the amount of electrolytic solution V _n after N unit time has elapsed from the reference time point
To the remaining ratio ν _n of the electrolytic solution of the electrolytic capacitor after a lapse of N unit time from the reference time point
ν _n = V _n / V _o
Further, the decrease rate δ of the electrolytic solution of the electrolytic capacitor per unit time is calculated as δ = (1−ν _n ) / N (2)
And an average value R of the ESR _n and ESR _o is obtained, and further, K = ESR _n / R (3)
Using this K, the remaining rate ν _{n + 1} of the electrolytic solution after elapse of N + 1 unit time from the reference time point is _expressed as ν _{n + 1} = ν _n −δK (4)
Was predicted as the equivalent series resistance ESR n + ₁ of the electrolytic capacitor after N + 1 unit time from the time when the said reference with [nu _{n + 1} predicted _{ESR n + 1 = ESR o (} 1 / ν n + ₁ ) ² (5)
And predicting deterioration of the electrolytic capacitor based on the ESR _{n + 1} .
As a result, K = ESR _n / R as an acceleration factor K for the decrease in the electrolyte
And the remaining rate ν _n of the electrolytic solution of the electrolytic capacitor after elapse of N unit time from the reference time, the decreasing rate δ of the electrolytic solution per unit time, and the K The remaining ratio ν _{n + 1} of the electrolytic solution after elapse of N + 1 unit time from the point of time becomes ν _{n + 1} = ν _n −δK
Predicted as, since the predicted value ESR n + ₁ of the corresponding equivalent series resistance in the residual ratio [nu _{n + 1} of the predicted electrolyte, the value of the equivalent series resistance by practical procedure simple ESR n _{+ 1} can be predicted. If the N unit time has elapsed, the value of the equivalent series resistance after 1 unit time has elapsed can be predicted. Here, since the value of the equivalent series resistance increases according to the decreasing rate of the electrolytic solution, it is possible to predict the deterioration of the electrolytic capacitor by predicting the value of the equivalent series resistance.

Furthermore, the invention according to claim 2 repeats the ESR _{n + 1} calculation method according to claim 1 at least twice, and M is an integer equal to or greater than 2, and N + M units from the reference time point according to claim 1 An electrolytic capacitor deterioration prediction method for determining an equivalent series resistance value ESR _{n + m} of an electrolytic capacitor after elapse of time and predicting the deterioration of the electrolytic capacitor based on the ESR _{n + m.} The series resistance value is predicted sequentially, and at that time, the equivalent series resistance value predicted in advance and the equivalent series resistance value at the reference time are used to estimate the equivalent series resistance for one unit time. The equivalent series resistance value ESR _{n + m} of the electrolytic capacitor after elapse of N + M unit time from the reference time point according to claim 1 is obtained by predicting the equivalent series resistance value at the elapsed time, and the ESR _n electrolysis based on the _{+ m} A degradation prediction method of an electrolytic capacitor, characterized by predicting the deterioration of the capacitor.
Thus, using the method for calculating ESR _{n + 1} of the electrolytic capacitor according to claim 1, the value ESR _n of the equivalent series resistance of the electrolytic capacitor after elapse of N + M unit time from the reference time point according to claim 1. _{+ m} is obtained, and deterioration of the electrolytic capacitor can be predicted based on the ESR _{n + m} . Then, if the time when the N unit time has elapsed is the current time, the deterioration of the electrolytic capacitor after the M unit time has elapsed can be predicted from the current time.

Furthermore, the invention described in claim 3 is the electrolytic capacitor deterioration prediction method according to claim 1 or 2, wherein the equivalent series resistance value ESR _o is a value of the equivalent series resistance of the electrolytic capacitor when not in use. When the ratio of the equivalent series resistance value ESR _{n + 1} or ESR _{n + m to} the equivalent series resistance value ESR _o is predicted to be 3 or more, the replacement time of the electrolytic capacitor is determined based on this prediction. This is a method for predicting deterioration of an electrolytic capacitor characterized by planning.
Thus, it can be determined that the life of the electrolytic capacitor is exhausted when the ratio of the equivalent series resistance value ESR _{n + 1} or ESR _{n + m to} the equivalent series resistance ESR _o becomes 3 or more.

According to the first aspect of the present invention, it is possible to predict the degree of deterioration of the electrolytic capacitor after the elapse of one unit time from the present time by a simple and practical procedure.
Furthermore, according to the invention described in claim 2, together with the effect of the invention described in claim 1, it is possible to predict the degree of deterioration of the electrolytic capacitor after elapse of M unit time from the present time by a simple and practical procedure. it can.
Furthermore, according to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, it is easy to predict the replacement time due to deterioration of the electrolytic capacitor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a switching regulator incorporating an electrolytic capacitor, FIG. 2 explains a method for predicting deterioration of the electrolytic capacitor, FIG. 3 shows a comparison between predicted data and measured data according to the present invention, and FIG. 4 shows the present invention. The flowchart of the application example of is shown.

As shown in FIG. 1, a switching regulator 10 as a kind of power supply circuit includes a DC / AC switch circuit that converts a DC voltage applied between a pair of DC input terminals 11a and 11b and input terminals 11a and 11b into an AC voltage. 12, a transformer 13 having the output of the DC / AC switch circuit 12 as a primary side input, a diode 14 for rectifying the secondary side output of the transformer 13, a smoothing circuit 15 for smoothing the output of the diode 14, and an output side of the smoothing circuit 15 A pair of output terminals 18a and 18b connected to the. The smoothing circuit 15 includes a coil 16 (connected between the output side of the diode 14 and the output terminal 18a) and an electrolytic capacitor 17 (connected between the output terminals 18a and 18b). The equivalent circuit of the electrolytic capacitor 17 is a series circuit of a capacitance 17a and an equivalent series resistance 17b.
A constant load 20 such as an electronic measurement control device is connected between the output terminals 18a and 18b. In addition, since the power consumption of the fixed load 20 does not normally change with aging, the average effective value of the charge / discharge current of the electrolytic capacitor 17 is also constant.

  The ESR measuring instrument 30 is connected to both ends of a partial circuit in which an AC voltage source 31, a resistor 32, and an AC ammeter 33 are connected in series, an AC voltmeter 34 connected in parallel to the partial circuit, and the AC voltmeter 34. A pair of measurement terminals 35a and 35b is provided.

At this time, if the frequency of the AC voltage source 31 is f, the value of the capacitance 17a is C, the resistance value of the equivalent series resistance 17b is ESR, and f is set so that 1 / 2πfC is significantly smaller than ESR, the electrolytic capacitor 17 Is substantially ESR. Further, the inductance of the coil 16 is L, and f is set so that 2πfL is significantly larger than ESR. In addition, the constant load 20 is, for example, about 5 V (voltage between the output terminals 18a and 18b) and about 10A. At this time, the impedance of the constant load 20 is 0.5Ω. For example, if f is 100 kHz when C is 1000 μF, 1 / 2πfC is about 0.0016Ω. At this time, since the ESR is, for example, about 0.05Ω, the ESR becomes remarkably larger than 1 / 2πfC.
Further, since the inductance of the coil 16 is 100 μH, for example, 2πfL is about 63Ω at this time. For this reason, the impedance of the coil 16 is significantly larger than the ESR. Furthermore, the impedance value obtained by connecting the impedance of the coil 16 and the impedance of the constant load 20 in parallel is about 0.5Ω.
Therefore, at the frequency f, the impedance of the electrolytic capacitor 17 is substantially equal to ESR, and the combined value of the impedance of the constant load 20 and the coil 16 connected in parallel to the electrolytic capacitor 17 is the impedance of the electrolytic capacitor 17. It becomes significantly larger.

  Therefore, when measuring the value ESR of the equivalent series resistance 17 b of the electrolytic capacitor 17, the input terminals 11 a and 11 b are disconnected from the DC power supply, and the electric charge of the electrolytic capacitor 17 is completely discharged. The measurement terminals 35a and 35b are connected to the output terminals 18a and 18b. Then, by dividing the measurement value of the AC voltmeter 34 by the measurement value of the AC ammeter 33, the value ESR of the equivalent series resistance 17b can be obtained.

Specifically, the following deterioration prediction program is executed to predict an increase in the value ESR of the equivalent series resistance 17b, thereby predicting the deterioration of the electrolytic capacitor 17.
When power is supplied to the constant load 20 by the switching regulator 10, as shown in FIG. 2, the value ESR _o of the equivalent series resistance 17b of the electrolytic capacitor 17 measured at the reference time point and the reference time point n unit time (e.g. n year, n month, etc.) to measure the value ESR _n the equivalent series resistance 17b measured after lapse of a ESR _o and ESR _n said measured, the electrolytic capacitor 17 at the time serving as the reference ESR _n / ESR _o = (V _o / V _n ) ² (1) Relation between electrolyte amount V _o and electrolyte amount V _n of electrolytic capacitor 17 after N unit time has elapsed from the reference time point
Ν _n = V _n / V _{o, where} ν _n is the remaining ratio of the electrolytic solution of the electrolytic capacitor 17 after elapse of N unit time from the reference time point
Further, the decrease rate δ of the electrolytic solution of the electrolytic capacitor 17 per unit time is calculated as δ = (1−ν _n ) / N (2)
Further, as described above, since the impedance of the coil 16 connected in series to the equivalent series resistance 17b is significantly larger than the value ESR of the equivalent series resistance 17b, the equivalent due to the increase in the value ESR of the equivalent series resistance 17b is calculated. Since the decrease in the value of the current flowing through the series resistor 17b is slight, the amount of heat generated by the equivalent series resistor 17b increases due to the increase in the value ESR of the equivalent series resistor 17b, and the decrease in the electrolyte is accelerated. Therefore, K = ESR _n / R (3)
Define Note that R is an average value of ESR _n and ESR _o, and K is larger than 1 because ESR _n is larger than ESR _o . Then, using this K, the remaining rate ν _{n + 1} of the electrolytic solution after elapse of N + 1 unit time from the reference time point is _expressed as ν _{n + 1} = ν _n −δK (4)
To predict. Then, using the predicted ν _{n + 1} , the value ESR _{n + 1} of the equivalent series resistance 17b after the elapse of N + 1 unit time from the reference time point is obtained as ESR _{n + 1} = ESR _o (1 / ν _{n + 1} ) ² (5)
To predict.
In addition, by introducing the acceleration factor K in FIG. 2, the amount V _{n + 1} of the electrolytic solution of the electrolytic capacitor after the elapse of N + 1 unit time from the reference time point is a straight line connecting V ₀ and V _n. It lies on a straight line indicated by a lower dotted line.

As a result, K = ESR _n / R as an acceleration factor K for the decrease in the electrolyte
Using this K, the remaining ratio ν _{n + 1} of the electrolytic solution after the elapse of N + 1 unit time from the reference time point is _expressed by ν _{n + 1} = ν _n − according to the simple algebraic equation (4). δK (4)
Predicted as, since the predicted value ESR n + ₁ of the equivalent series resistance 17b corresponding to the remaining rate [nu _{n + 1} of the predicted electrolyte, the value ESR _n the equivalent series resistance 17b by practical procedures in a convenient ₊₁ can be predicted. Thereby, it is possible to predict the deterioration of the electrolytic capacitor depending on whether or not the value of ESR _{n + 1} exceeds the deterioration determination level (for example, three times the equivalent series resistance when not used as shown in FIG. 3).

Further, the above-described method for predicting deterioration of the electrolytic capacitor 17 is repeated at least twice, and the value ESR _{n + m} of the equivalent series resistance 17b after N + M unit time has elapsed from the reference time, with M being an integer of 2 or more. To do. At this time, the value of the equivalent series resistance 17b for each unit time is sequentially predicted, and the previously estimated value of the equivalent series resistance 17b and the value ESR ₀ of the equivalent series resistance 17b at the reference time are used first. By predicting the value of the equivalent series resistance 17b when 1 unit time has elapsed from the time when the value of the equivalent series resistance 17b is predicted, the value ESR _n of the equivalent series resistance 17b after N + M unit time has elapsed from the reference time Predict _{+ m} .
Accordingly, the value ESR _{n + m} of the equivalent series resistance 17b after the lapse of N + M unit time from the reference time point can be predicted using the above-described deterioration prediction method for the electrolytic capacitor 17. If the time when the N unit time has elapsed is the current time, the value ESR _{n + m} of the equivalent series resistance 17b after the M unit time has elapsed can be predicted from the current time.
In FIG. 3, in the lapse of time on the horizontal axis, the time point of the fifth year is set as the reference time, the twelfth year is set as the N year, and the value ESR of the equivalent series resistance 17b is calculated by ESR ₀ at the reference time and the ESR _n of the twelfth year. The predicted case is shown. The value ESR of the equivalent series resistance 17b predicted in this way increases with time. The predicted ESR data is close to the measured ESR data.

Further, in the above-described electrolytic capacitor deterioration prediction method, when the value ESR _o of the equivalent series resistance 17b is the value of the equivalent series resistance 17b of the electrolytic capacitor 17 when not in use, the value ESR _{n + 1} of the equivalent series resistance is obtained. Alternatively, a point in time when the ratio of ESR _{n + m to} the value ESR _o of the equivalent series resistance 17b becomes 3 or more is predicted, and the replacement time of the electrolytic capacitor 17 is planned based on this prediction.
Here, empirically, when the electrolytic solution is reduced by about 40% from the unused state, it is said that the lifetime of the electrolytic capacitor is applied. When this is applied to the above equation (1), the ratio of the equivalent series resistance is almost equal. Therefore, when the ratio ESR _{n + 1} of the equivalent series resistance 17b or the ratio ESR _{n + m} of the equivalent series resistance 17b to the value ESR _o of the equivalent series resistance 17b is predicted to be 3 or more, the replacement time of the electrolytic capacitor 17 is estimated. Can be planned.

(Application example of the present invention)
In the flowchart shown in FIG. 4, first, the initial ESR ₀ of the electrolytic capacitor 17 is measured when the switching regulator 10 is installed (step S1). Next, ESR ₆ is measured at a regular inspection in the sixth year (step S2). Next, ESR ₁₂ is measured in a periodic inspection in the 12th year (step S3).
Next, the above-described deterioration prediction program is executed using the measured ESR ₆ and ESR ₁₂ (step S4).
As shown in FIG. 3, the value of the equivalent series resistance 17b when the electrolytic capacitor 17 is not used and the value of the equivalent series resistance 17b immediately before use of the electrolytic capacitor 17 when the electrolytic capacitor 17 has been used for five years. Therefore, it has been found that the life of the electrolytic capacitor 17 can be predicted based on the deterioration prediction result using the data of 5 years and 12 years. In addition, since the period of the regular periodic inspection is 6 years and 12 years, the data of the 6th and 12th years are used. Here, since the deterioration prediction program is a calculation program corresponding to claim 1, the ESR ₁₈ in the 18th year is predicted by calculating from the above equations (1) to (5).
Next, when the predicted ESR ₁₈ exceeds three times the initial value ESR ₀ (step S5), the ESR _{15 in the} 15th year is measured (step S6). On the other hand, when the predicted ESR ₁₈ does not exceed three times the initial value ESR ₀ , the ESR _{18 in the} 18th year is measured (step S7). When the measured ESR ₁₅ or ESR ₁₈ exceeds three times ESR ₀ (step S8), the switching regulator 10 is repaired, that is, the electrolytic capacitor 17 is replaced (step S9).
On the other hand, when the measured value of ESR ₁₅ or ESR ₁₈ does not exceed three times ESR ₀ , the deterioration determination program is executed (step S10). The conditions at this time are such that the value of the equivalent series resistance 17b at the reference time is ESR ₆ and the value of the equivalent series resistance 17b after the elapse of N unit time is the measured value of ESR ₁₅ or ESR ₁₈ . A time point exceeding 3 times ESR ₀ is predicted.
Finally, it is planned that the switching regulator 10 is repaired, that is, the electrolytic capacitor 17 is replaced in the previous year when the predicted value of the equivalent series resistance 17b exceeds three times ESR ₀ (step S11).
For this reason, an improvement in the reliability of operation of the electronic measurement control device using the switching regulator 10 as a power source can be expected, and the reliability of the operation of the entire plant system including the electronic measurement control device can be improved.

  In the above embodiment, the electrolytic capacitor 17 is used in the switching regulator 10, but the present invention is not limited to this, and the present invention is for smoothing the output voltage used in the power supply circuit including the switching regulator 10. Applies to electrolytic capacitors.

A switching regulator incorporating an electrolytic capacitor. It is a graph explaining the deterioration prediction method of the said electrolytic capacitor. It is a graph which shows the comparison with the prediction data by this invention, and measurement data. It is a flowchart of the application example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Switching regulator 17 Electrolytic capacitor 17a Capacitance 17b Equivalent series resistance 20 Constant load 30 ESR measuring device

Claims (3)

A method for predicting deterioration of an electrolytic capacitor, wherein the equivalent series resistance value ESR _o measured at a reference time point and the electrolytic capacitor measured after N unit time such as N years has elapsed from the reference time point Measure the equivalent series resistance value ESR _{n of}
Relationship between the measured ESR _o and ESR _n , the electrolytic solution volume V _o of the electrolytic capacitor at the reference time point, and the electrolytic solution amount V _n of the electrolytic capacitor after N unit time has elapsed from the reference time point Formula ESR _n / ESR _o = (V _o / V _n ) ²
To the remaining ratio ν _n of the electrolytic solution of the electrolytic capacitor after a lapse of N unit time from the reference time point
ν _n = V _n / V _o
Further, the decrease rate δ of the electrolytic solution of the electrolytic capacitor per unit time is calculated as δ = (1−ν _n ) / N
And calculating an average value R of the ESR _n and ESR _o, and further, K = ESR _n / R as an accelerating factor K of the decrease in the electrolyte
Using this K, the remaining ratio ν _{n + 1} of the electrolytic solution after the elapse of N + 1 unit time from the reference time point is _expressed as ν _{n + 1} = ν _n −δK.
Predicted as a value ESR n + ₁ of the equivalent series resistance of the electrolytic capacitor after N + 1 unit time from the time when the said reference with the predicted _{ν n + 1 ESR n + 1} = ESR o (1 / ν _{n + 1} ) ²
And predicting deterioration of the electrolytic capacitor based on the ESR _{n + 1} . The ESR _{n + 1} calculation method according to claim 1 is repeated at least twice so that M is an integer equal to or greater than 2, and the equivalent series resistance of the electrolytic capacitor after elapse of N + M unit time from the reference time point according to claim 1 A method for predicting deterioration of an electrolytic capacitor that calculates a value ESR _{n + m} of the capacitor and predicting deterioration of the electrolytic capacitor based on the ESR _{n + m} ,
The value of the equivalent series resistance for each unit time is predicted sequentially, and the value of the equivalent series resistance is calculated using the value of the equivalent series resistance previously predicted and the value of the equivalent series resistance at the reference time point. 2. The equivalent series resistance value ESR _n of the electrolytic capacitor after a lapse of N + M unit time from the reference time point according to claim 1, by predicting an equivalent series resistance value at a time point when 1 unit time has elapsed from a predicted time point of _A method for predicting deterioration of an electrolytic capacitor, wherein _{+ m} is obtained and deterioration of the electrolytic capacitor is predicted based on the ESR _{n + m} . In the electrolytic capacitor deterioration prediction method according to claim 1 or 2,
Further, when the equivalent series resistance value ESR _o is an equivalent series resistance value of the electrolytic capacitor when not in use, the equivalent series resistance value ESR of the equivalent series resistance value ESR _{n + 1} or ESR _{n + m} is used. _A method for predicting deterioration of an electrolytic capacitor, wherein a point in time when the ratio to _o is 3 or more is predicted, and a replacement time of the electrolytic capacitor is planned based on the prediction.

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