JPH0722297A - Characteristics measuring circuit for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To provide a circuit for measuring the characteristics of an electrolytic capacitor with high accuracy by detecting the insufficient contact between the electrolytic capacitor and a probe electrode. CONSTITUTION:The characteristics measuring circuit for electrolytic capacitor comprises a variable DC power supply 8 for feeding current to an electrolytic capacitor 2 to be measured through probes 6a, 6b, means 12 connected in series with the electrolytic capacitor through the probe to impart an AC signal thereto, and a circuit 20 connected in series with the AC signal applying means and the electrolytic capacitor to detect the AC signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a characteristic measuring circuit for an electrolytic capacitor used for detecting leak current.

[0002]

2. Description of the Related Art Generally, one of the electrical characteristics of an electrolytic capacitor is a leakage current characteristic. This leakage current characteristic is caused by the characteristic of the structure in which the anode and the cathode face each other with the dielectric and the electrolyte interposed, and is a factor for judging the quality of the electrolytic capacitor. Normal,
When an initial voltage is applied to an electrolytic capacitor, the current suddenly increases, reaches a peak, and then decays in a gradually decreasing state over time and stabilizes. Is the leakage current. This increase and attenuation of leakage current is peculiar to electrolytic capacitors, and the characteristic that stabilizes after attenuation largely depends on cracks etc. in the dielectric oxide film. The oxide film has the property of repairing. This is a phenomenon described as a self-repairing action and is peculiar to electrolytic capacitors.

[0003]

The leakage current characteristic is measured by a method in which a power source is connected to the electrolytic capacitor to be measured by a probe electrode and the current flowing in the circuit is detected by a current measuring means. However, it is known that the contact state of the probe electrode affects the measurement result. For example, if the lead of the electrolytic capacitor and the probe electrode are poorly contacted, that is, if they are in an insufficiently connected state, the value of the leakage current becomes zero, resulting in defective products being non-defective.

Therefore, conventionally, a contact detection circuit for contacting the probe electrode has been separately provided to improve the detection accuracy. For example, it is a method of inserting a resistor in series with an electrolytic capacitor and measuring the voltage drop appearing in the resistor.
However, using such a resistance drop means that power consumption due to the resistance is large, and heat generation and fluctuations in the current value due to the resistance cannot be ignored. Although contact detection is possible, it affects detection accuracy. It is not preferable.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a characteristic measuring circuit for an electrolytic capacitor, which detects a contact failure between the electrolytic capacitor and a probe electrode to improve detection accuracy.

[0006]

A characteristic measuring circuit for an electrolytic capacitor according to the present invention is a power source (variable DC power source 8) for supplying a current to an electrolytic capacitor (2) whose characteristic is to be measured through probes (6a, 6b). AC signal applying means (transformer 12) that is connected in series to the electrolytic capacitor via the probe to apply an AC signal, and is connected in series to the AC signal applying means and the electrolytic capacitor to output the AC signal. AC signal detecting means for detecting (AC detecting circuit 2
0) and are provided.

[0007]

In this characteristic measuring circuit of the electrolytic capacitor, the power source and the leakage current detecting means are connected in series to the electrolytic capacitor, and the AC signal applying means and the AC signal detecting means are connected in series to the electrolytic capacitor. It is a thing. An alternating current signal is applied from the alternating current signal applying means. Then, this AC signal is detected through AC signal detecting means that forms a series circuit with the electrolytic capacitor. Whether or not the electrolytic capacitor and the probe are correctly connected can be determined based on the presence or absence of the detection of the AC signal. As a result, it can be recognized that the measured leakage current value is correct. Of course, after detecting this contact state, the leak current of the electrolytic capacitor may be detected, and similarly, it can be known that the detection result of the leak current is correct.

[0008]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows an embodiment of a characteristic measuring circuit for an electrolytic capacitor according to the present invention. This characteristic measuring circuit
Leads 4a, 4b of the electrolytic capacitor 2 whose characteristics are to be measured
The probes 6a and 6b are provided corresponding to. A positive electrode of a variable DC power source 8 is connected to the probe 6a as a power source for supplying a current to the electrolytic capacitor 2, and a negative current side thereof is connected to a leakage current determination circuit 10 which is a leakage current detecting means. In the probe 6b, the secondary coil 12s of the first transformer 12 as an AC signal applying means and the primary coil 14 of the second transformer 14 as an AC signal detecting means.
p is connected in series and these transformers 1
The leakage current determination circuit 10 is connected via 2 and 14. That is, in this embodiment, the electrolytic capacitor 2, the probe 6a, the variable DC power source 8, the leakage current determination circuit 10, the primary coil 14p of the transformer 14, the secondary coil 12s of the transformer 12, and the probe 6b form a single closed circuit 16. Is done.

An oscillation circuit 18 is connected to the primary coil 12p of the transformer 12 as an AC signal generating means. An alternating current signal is generated in the oscillator circuit 18 at timing T ₁ every time the electrolytic capacitor 2 is measured.

An AC detection circuit 20 for selectively detecting only an AC signal is connected to the secondary coil 14s of the transformer 14. The AC detection circuit 20 detects the presence or absence of an AC signal and its level, and can be configured by, for example, a rectifying circuit using a diode or a rectifying circuit to which a smoothing circuit such as a capacitor is added. The AC detection circuit 20 operates at timing T ₂ to detect an AC signal.

The detection output of the AC detection circuit 20 is applied to the positive phase input side of the comparator 22. The reference voltage Vref set by the voltage source 24 is applied to the negative phase input side of the comparator 22. Comparator 22
AC detection circuit 20 that exceeds this reference voltage Vref
When the output of is added, its H output is obtained. The output of the comparator 22 is added to the set input S of the SR flip-flop circuit 26, and when the comparator 22 produces the H output, the output Q of the SR flip-flop circuit 26 is output.
Becomes H output.

The output Q of the SR flip-flop circuit 26 is applied to the AND circuit 28 which is the judging means, and has one of the AND conditions. The detected leakage determination output of the leakage current determination circuit 10 is added to the AND circuit 28 as the other AND condition input. When both AND conditions are satisfied, the final judgment output V _J is output to the output terminal 30.
Is obtained.

With this structure, the probe 6 is attached to the leads 4a and 4b of the electrolytic capacitor 2 to be measured.
When the voltage applied to the closed circuit 16 from the variable DC power supply 8 is raised to the specified voltage in a state where the operation of the oscillation circuit 18 is stopped after the a and 6b are brought into contact with each other, a leakage current flows through the electrolytic capacitor 2. When the leakage current determination circuit 10 is operated at a specific timing T ₁ , the leakage current is determined by the leakage current determination circuit 10. When an appropriate leakage current is obtained, the H output is obtained as the determination output from the leakage current determination circuit 10.

Next, at timing T ₂ , the oscillator circuit 18 is operated to oscillate an AC signal. This AC signal is applied to the closed circuit 16 through the transformer 12. This closed circuit 1
The condition of 6 is established on condition that the probe 6a and the lead 4a and the probe 6b and the lead 4b are in electrical contact with each other. If this condition is satisfied, an AC signal is applied inside the closed circuit 16, and this AC signal is detected by the AC detection circuit 20 through the transformer 14. This detection output is applied to the comparator 22 and compared with the reference voltage Vref to obtain the reference voltage Vref.
When a level exceeding 0 is reached, an H output is obtained from the comparator 22. In response to this H output, the output Q of the SR flip-flop circuit 26 becomes an H output.

The H output and SR of this leakage current determination circuit 10
When the output Q of the flip-flop circuit 26 is established, AN
The AND condition of the D circuit 28 is satisfied, and the judgment output V _J is obtained at the output terminal 30 thereof. That is, the probes 6a and 6b
Touches the leads 4A, 4b of the electrolytic capacitor 2 and indicates that the leak current value obtained at that time is appropriate. If the AND circuit 28 is not established, it means that the probes 6a and 6b have a poor contact, or the determination result of the leakage current determination circuit 10 indicates that the electrolytic capacitor 2 is defective. Therefore, it can be known from the result whether the electrolytic capacitor 2 is a good product or a defective product.

In this way, the leakage current is judged at the timing T ₁ , and the leads 4a and 4b and the probe 6 at the timing T _2.
The contact detection with a and 6b is carried out in order to prevent the adverse effect of the simultaneous detection and the leakage output from affecting the oscillation output. Such leak current measurement and contact detection are performed for each electrolytic capacitor 2, but the reset input R of the SR flip-flop circuit 26 is reset by the reset circuit in order to cancel the output Q for each detection and measurement. If the next contact detection is performed after the addition of, the detection and measurement can be performed with high accuracy. Regarding the setting of the timings T ₁ and T ₂ , the contact detection may be performed _first at the timing T ₁ , and then the leakage current determination may be performed at the timing T ₂ .

Next, FIG. 2 shows another embodiment of the characteristic measuring circuit for electrolytic capacitors of the present invention. In the above embodiment, the oscillator circuit 18 is used as the AC signal generating means,
The AC signal does not need to be a continuous signal for contact determination. Therefore, the circuit shown in FIG.
The DC signal power supply 34 is connected to the primary coil 12p of the transformer 12 via the switch 32 by utilizing the inductance of the AC signal generating circuit 36. That is, in the AC signal generating circuit 36, when the switch 32 is closed, a transient current flows in the primary coil 12p of the transformer 12 due to the voltage application of the DC power supply 34. This change in the transient current causes an AC signal in the secondary coil 12s. This AC signal exponentially decays over time because the power supply applied is DC, but is sufficient as an AC signal for detecting the contact state.

[0019]

As described above, according to the present invention,
The contact state of the probe with respect to the electrolytic capacitor can be electrically detected regardless of the leakage current, the correctness of the measured value of the leakage current can be reliably recognized, the measurement accuracy can be improved, and the measurement efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a characteristic measuring circuit for an electrolytic capacitor of the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the characteristic measuring circuit for an electrolytic capacitor of the present invention.

[Explanation of symbols]

 2 Electrolytic Capacitors 6a, 6b Probe 8 Variable DC Power Supply 12 Transformer (AC Signal Applying Means) 14 AC Detection Circuit (AC Signal Detecting Means)

Claims (1)

[Claims] 1. A power source for supplying a current to an electrolytic capacitor whose characteristics are to be measured via a probe, and an AC signal applying unit connected in series to the electrolytic capacitor via the probe to apply an AC signal, An electrolytic capacitor characteristic measuring circuit comprising: a signal applying unit and an AC signal detecting unit that is connected in series to the electrolytic capacitor to detect the AC signal.