JP2647683B2 - Electrolytic capacitor short detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor short detection device used for detecting a short circuit of an electrolytic capacitor during an aging process.

[Conventional technology]

During the aging process of the electrolytic capacitor, detection of the short circuit of the electrolytic capacitor is indispensable for determining whether the electrolytic capacitor is good or defective. Conventionally, short detection is generally considered to be a short circuit when the current flowing inside the electrolytic capacitor exceeds a certain level, and the charging period before the electrolytic capacitor reaches the final voltage is a short detection period. Has been excluded from.

[Problems to be solved by the invention]

However, in short-circuit detection focusing only on such a current, the detection time varies depending on the capacitance of the electrolytic capacitor, and a detection error such as a non-defective product being determined as a non-defective product depending on the magnitude of the charging current occurs. There is a drawback in that a defective product is determined as a non-defective product because an instantaneous short circuit occurring outside the time period cannot be detected. In particular, a momentary short is 70% of the voltage rise to the ultimate voltage.
Concentrations occur in the vicinity of about 90%, and placing such a section outside the detection time causes a reduction in detection accuracy. For this reason, the charging period before reaching the final voltage is also included in the short-circuit detection time, and such a short-circuit detection requires detection of a sudden voltage change at the time of a voltage rise.

Accordingly, an object of the present invention is to realize a short-circuit detecting device for an electrolytic capacitor that detects a short-circuit based on a change in voltage when a voltage rises.

[Means for solving the problem]

Short detection device of the electrolytic capacitor of the present invention, as shown in FIG. 1, the voltage V _C which corresponds to the terminal voltage V _X or the terminal voltage V _X of the electrolytic capacitor C _X is the input voltage, just the input voltage The voltage holding means (low-pass filter 6) for holding with a delay time, the voltage held in the voltage holding means (low-pass filter 6), and the input voltage are compared, and a short circuit is generated based on the magnitude relationship between the two. Is determined.
And a short determination unit (short determination unit 11).

In short detection device of the electrolytic capacitor, the input voltage is the terminal voltage V _X or the corresponding voltage of the electrolytic capacitor C _X
V _C may be used, and the corresponding voltage V _C is a voltage obtained by reducing the terminal voltage V _X at a fixed rate by a voltage dividing means or the like.

As shown in FIG. 1, the apparatus for detecting a short circuit of an electrolytic capacitor according to the present invention reduces a holding voltage at a fixed ratio at a subsequent stage of a voltage holding means (a low-pass filter 6) to thereby determine a short circuit. A dead zone setting means (dead zone setting unit 7) in addition to the unit 11) can be provided.

[Action]

Flowing aging current to the electrolytic capacitor C _X, if a short circuit in the electrolytic capacitor C _X does not occur, although the terminal voltage V _X increases over time, if the short circuit occurs, the terminal voltage V _X
Drops sharply. Therefore, such a terminal voltage V _X
Or when the voltage V _C of the input voltage corresponding to the terminal voltage V _X, the voltage change in the mode corresponding to the presence or absence of occurrence of a short circuit occurs in the input voltage.

Voltage holding means (low-pass filter 6) for this input voltage
In addition, the voltage holding means (low-pass filter 6) holds the input voltage with a slight delay time according to the input voltage that changes momentarily during charging due to the characteristic of holding with a slight delay time. You. Therefore, when a short circuit occurs, the input voltage immediately before the short circuit is held. In other words, even if the input voltage decreases due to the short circuit, the input voltage immediately before the short circuit is maintained in the voltage holding means for a certain time. Will be. Looking at this relationship in terms of the magnitude of the voltage, the input voltage is higher or equal to the holding voltage of the voltage holding means before the short circuit, whereas the holding voltage of the voltage holding means is maintained for a certain time immediately after the short circuit. The voltage becomes larger than the input voltage, and the magnitude relationship between the two is reversed before and after the occurrence of the short circuit.

Therefore, a determination result indicating the occurrence of a short circuit is obtained from a change in the magnitude relationship between the voltage held in the voltage holding means and the input voltage.

In the apparatus for detecting a short circuit of an electrolytic capacitor according to the present invention, a dead band setting unit (dead band setting unit 7) is provided downstream of the voltage holding unit to reduce the holding voltage at a fixed ratio and to add the holding voltage to the short determination unit (short judgment unit 11). With this setting, a detection error due to a voltage change other than a short circuit of the input voltage is removed, and the detection accuracy of the short circuit detection is improved.

〔Example〕

FIG. 1 shows an embodiment of an electrolytic capacitor short detection device according to the present invention.

This short detection device is attached to the aging processing circuit 1 in order to detect a short circuit of the electrolytic capacitor _CX during the aging process. The aging processing circuit 1 connects the DC power supply 12 with the resistor 14 and the constant current element 16 to the electrolytic capacitor C _X connected to the aging terminals X ₁ and X _2.
To provide an aging current due to the constant current obtained by the constant current element 16.

The light-emitting diode 21 of the photocoupler 2 for detecting the aging processing is connected in series to the aging processing circuit 1 with respect to the constant current element 16. The light emitting diode 21 is energized by the aging current, and emits light while the electrolytic capacitor _CX is being charged by the aging current. Thus, the light emission indicates the aging processing period. In addition, a diode 18 is connected in parallel to the series circuit of the constant current element 16 and the light emitting diode 21, and the diode 18 protects the constant current element 16 and the light emitting diode 21 from a reverse voltage.

Further, a voltage dividing circuit 3 installed as a voltage detecting unit is connected in parallel to the electrolytic capacitor _CX . Voltage dividing circuit 3 is composed of resistors 31 and 32, dividing the terminal voltage V _X of the electrolytic capacitor C _X by a resistance ratio of the resistors 31 and 32, the terminal voltage
The voltage V _C corresponding to V _X output from the midpoint of resistors 31 and 32.
Here, assuming that the resistance values of the resistors 31 and 32 are R ₁ and R ₂ , the voltage V _C generated at the middle point of the resistors 31 and 32 with respect to the terminal voltage V _X is And is applied as an input voltage to the short-circuit detection unit.

This voltage V _C is applied to a low-pass filter 6 as voltage holding means through a buffer circuit 4 provided on the positive side as impedance conversion means and a buffer circuit 5 provided on the negative side as reference potential setting means. The buffer circuit 4 is provided to increase the input impedance, and includes an operational amplifier 40 and resistors 42 and 44. The buffer circuit 5 includes a DC power supply 12
And the operational amplifier 50 and resistors 52, 54, 56
It is composed of And the low-pass filter 6 is a resistor
It is composed of an inverted L-shaped circuit of 60 and a capacitor 62,
A fixed time constant is set by the resistor 60 and the capacitor 62. Thus, the capacitor 62 voltage V _C obtained through the buffer circuit 4 and 5 are held with a predetermined delay time.

The voltage V _C held in the capacitor 62 is applied to a dead zone setting unit 7 installed to eliminate an error in short-circuit detection. The dead zone setting unit 7 of this embodiment is a series circuit of a resistor 71 and a variable resistor 72. It is configured. The series circuit of the resistor 71 and the variable resistor 72 forms a voltage dividing circuit, and the variable resistor 72 obtains a voltage V _CF divided according to the voltage dividing ratio.
For example, the voltage division ratio of the resistor 71 and the variable resistor 72 is 90%
If it is set to about, the voltage V _CF will be set to 0.9 V _C.

This voltage V _CF is applied to the first inverting amplifier 9 and inverted. Inverting amplifier 9 is constituted by an operational amplifier 90 and resistors 92, 94, 96, and outputs a voltage -V _CF obtained by inverting the voltage V _CF.

On the other hand, the voltage V _C obtained through the voltage dividing circuit 3 is applied to the second inverting amplifier 10 through the buffer circuit 8 provided as an impedance converting means. The buffer circuit 8 includes an operational amplifier 80 and resistors 82 and 84. The inverting amplifier 10 includes an operational amplifier 100 and resistors 102 and 104. A reference potential is set on the positive input side from the output side of the buffer circuit 5 as in the inverting amplifier 9. Therefore, the voltage -V _C which is inverted through the inverting amplifier 10 is obtained.

The voltages −V _CF , −V obtained through the inverting amplifiers 9 and 10
_C is a comparator 11 provided as a voltage comparing means in the short determining section 11 for determining the occurrence of a short from the magnitude relation.
0, the voltage -V _C is applied as a positive input, and the voltage -V _CF is applied as a negative input, and compared. By this comparison, the magnitude relationship between the two is obtained.
It is applied as one input of an AND circuit 113 through a voltage setting means 12.

Then, the light 22 obtained by the light emitting diode 21 of the photocoupler 2 is input to the light receiving transistor 23. Since the voltage V _CC applied to the power supply terminal 24 is applied through the resistor 25 to the collector side of the light receiving transistor 23, conduction is performed by the input light 22 and the conduction output is taken out from the collector side, and the inverter 114 After being inverted through A
It is added to the ND circuit 113.

In the AND circuit 113, a logical product is established by the output of the comparator 110 and the output of the inverter 114, and an H output is obtained when a short circuit occurs during the aging process. The output of the AND circuit 113 is added to the set input S of the SR flip-flop circuit (SR-FF) 115. When the set input S becomes the H input, the output Q of the SR-FF 115 becomes the H output. Is output from the output terminal 116 as a short detection output _VOUT .

The reset input R of the SR-FF 115 has a two-level reset voltage of H / L applied to the reset input terminal 117.
V _R is applied divided through resistors 118 and 119.
That is, during the aging started, by the reset voltage V _R
SR-FF115 is set to the reset state, the short detection output _VOUT is released, and the state is set to the initial state.

 In the above configuration, a short detection operation will be described.

By the start of aging, the electrolytic capacitor C _X is charged by the aging current, and its terminal voltage V _X becomes the second voltage.
As shown in A of FIG rises in accordance with the charging and short circuit the developing occurs after abruptly drops at the short point S _H, it is increased by the charge again.

Such terminal voltage V _X is applied to the voltage dividing circuit 3, resistors
32, the voltage V _C as shown in the second diagram exhibiting the change in proportion to the voltage dividing ratio B is obtained. The voltage V _C, the buffer circuit 4,
5, a low-pass filter 6 and a capacitor
62 is maintained with a constant delay time, it is taken out as a voltage V _CF through a resistor 71 and a variable resistor 72. This voltage V
_CF is a resistor 71 and a variable resistor as shown in FIG.
It has a slightly lower value with a partial pressure ratio of 72 and persists with a certain delay time. At this time, comparing the voltage V _C with the voltage V _CF , before the occurrence of the short circuit, V _C >
V _CF, the predetermined time t ₁ ~t ₂ after short generation, it can be seen that V _C <V _CF, and the magnitude relation short before and after the occurrence are reversed.

These voltages V _CF and V _C are inverted by the inverting amplifiers 9 and 10, and C in FIG. 2 represents voltages −V _C and −V _CF obtained by the inversion. These voltages −V _C and −V _CF are output from the comparator 11
Are compared by 0, as shown in D of FIG. 2, the comparator 110 at a certain time t ₁ ~t ₂ after short the magnitude relationship is inverted
, An H output is obtained as a comparison output.

On the other hand, since the light emitting diode 21 emits light during the aging period, the output of the inverter 114 becomes the H output as shown in E of FIG.

As a result, both inputs of the AND circuit 113 become H inputs, and
The D condition is satisfied, and as shown in F of FIG.
Becomes H output.

Since this H output becomes the set input S of SR-FF115,
As shown by G in FIG. 2, the output Q of the SR-FF 115 becomes an H output, and this H output is taken out from the output terminal 116 as a short detection output V _OUT indicating occurrence of a short circuit.

This short detection output V _OUT is provided as data representing a defective product to a computer that monitors the inspection result, and can be used for determining good or defective.

Then, the input of the comparator 110 is reduced to the voltage V _C by the resistance 71 and the variable resistor 72 to the voltage V _CF in the embodiment, and since then compared with the voltage V _C, to reduce the voltage V _CF min However, it is possible to provide a margin for noise and potential fluctuations, to prevent malfunction due to noise and the like, and to improve the detection accuracy of short-circuit detection.

In the embodiment, the voltage V _C (corresponding to the terminal voltage V _X ) obtained by dividing the terminal voltage V _X of the electrolytic capacitor C _X is used as the input voltage, but the terminal voltage V _X is used directly as the input voltage. The same short-circuit detection is possible.

In the embodiment, the inverting amplifiers 9 and 10 are set to set the voltage.
After the inversion of V _C and V _CF , the comparison is performed by the comparator 110. However, the short circuit can be similarly detected by comparing the voltages V _C and V _CF without installing the inverting amplifiers 9 and 10.

〔The invention's effect〕

As described above, according to the present invention, it is possible to reliably detect a short circuit based on a change in the terminal voltage of an electrolytic capacitor, and to reliably determine whether the electrolytic capacitor is good or defective during aging.

Further, according to the present invention, since the dead zone setting means is provided before the short determination means, malfunction due to noise or the like can be prevented, and the detection accuracy of short detection can be increased.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the electrolytic capacitor short detection device according to the present invention, and FIG. 2 is a diagram showing the operation of the electrolytic capacitor short detection device shown in FIG. C _X ... electrolytic capacitor 6 ... low-pass filter (voltage holding means) 7 ... dead zone setting section (dead zone setting section) 11 ... short determination section (short determination section)

Claims (2)

(57) [Claims] A voltage holding means for holding a terminal voltage of an electrolytic capacitor or a voltage corresponding to the terminal voltage as an input voltage, and holding the input voltage with a certain delay time; a voltage held by the voltage holding means; A short-circuit detecting device for an electrolytic capacitor, comprising: a short-circuit judging means for comparing the input voltage with the input voltage and judging occurrence of a short-circuit based on a magnitude relation between the two. 2. A short-circuit detection of an electrolytic capacitor according to claim 1, further comprising a dead zone setting means for reducing a voltage held by the voltage holding means at a fixed ratio and adding the dead band setting means to the short-circuit judging means after the voltage holding means. apparatus.