JPH0729781A - Self-repair circuit for tantalum capacitor - Google Patents

Abstract

PURPOSE:To correct the unsatisfactory state of leakage current by a method wherein, when the voltage of a tantalum capacitor after power source has been turned on is less than the prescribed, voltage, constant DC voltage is applied to the tantalum capacitor. CONSTITUTION:The voltage on one end (a) of a tantalum capacitor C0 and the threshold value Vth, which is determined by resistors R4 and R5, are compared by a comparator IC3. A transistor Q2 is turned on when the output of the above-mentioned comparator is 'H'. The constant DC voltage (the threshold voltage at which the oxide film inside the tantalum capacitor C0 is repaired) obtained when the transistor Q2 is turned on is applied to the tantalum capacitor C0 by the transistor Q1 through the intermediary of an emitter-collector. As a result, the internal oxide film is repaired by the application of constant voltage to the tantalum capacitor C0, the unsatisfactory state of leakage current is correct, and the leakage current can be made small when the leakage current is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-repairing circuit used in a circuit in which a voltage is applied to a tantalum capacitor for use.

[0002]

2. Description of the Related Art Conventionally, the leakage current of a tantalum capacitor has been
Although improvements have been made to prevent this, tantalum capacitor
When the leakage current becomes large, improve the large leakage current
The method was not considered. Figure 7 is a micro computer
Tantalum capacitor C in the reset circuit₀It was used
An example is shown. In this circuit example, the voltage is 5V DC power supply
Is turned on, the resistance R is increased as shown in FIG.₀Through
Tantalum capacitor C₀Is charged and one end a
Increase the voltage gradually. And the voltage reaches a certain value
Reset circuit IC consisting of a reset IC₂But
Micro computer IC₁Connected to the reset terminal RES of
The voltage at the point b is changed from "L" to "H". One
Mari reset circuit IC₂Reset release signal from Figure 8
Output as shown in FIG.
C₁Is released from the reset state. still
Reset circuit IC₂Has a watchdog timer
Microcomputer IC ₁WATCH / DOG out
Microcomputer IC when power is lost₁Lycee
Do not reset the output terminal RES to "L".
ing.

[0003]

If the leakage current of the tantalum capacitor C ₀ is large in the above-mentioned usage example,
There is a problem in that the voltage at the one end a is saturated at a certain value as shown in FIG. 8C, and the reset release signal is not generated from the reset circuit IC ₂ . In a circuit in which a certain voltage is applied to the tantalum capacitor and the voltage of the tantalum capacitor has a great meaning for the circuit function in this way, when the leakage current of the tantalum capacitor is large, it becomes a serious obstacle to the circuit function. There is a problem.

The present invention has been made in view of the above problems, and an object thereof is to self-repair a tantalum capacitor which can reduce the leakage current when the leakage current of the tantalum capacitor becomes large. In providing the circuit.

[0005]

In order to achieve the above object, the invention of claim 1 is used in a circuit in which a certain voltage is applied to a tantalum capacitor, and the voltage of the tantalum capacitor is set to a predetermined value after power is turned on. When the voltage is lower than the voltage, it comprises voltage applying means for applying a constant DC voltage to the tantalum capacitor to repair the problem of large leakage current of the tantalum capacitor.

The invention of claim 2 is used in a circuit in which a certain voltage is applied to a tantalum capacitor, and a constant DC voltage is applied to the tantalum capacitor when the voltage of the tantalum capacitor is below a predetermined voltage after power is turned on. And a voltage applying means for repairing the problem of large leakage current of the tantalum capacitor, and a display means for displaying that the problem of large leakage current of the tantalum capacitor has been repaired.

The invention of claim 3 is used in a circuit in which a certain voltage is applied to a tantalum capacitor, and when the voltage of the tantalum capacitor is below a predetermined voltage after power is turned on, heat is applied to the tantalum capacitor so that the tantalum capacitor is heated. It is composed of heat generating means for repairing the problem of large leakage current.

[0008]

According to the invention of claim 1, when the leakage current of the tantalum capacitor is large and the voltage thereof does not rise above a predetermined voltage, a constant DC voltage is applied to the tantalum capacitor to leak the leakage current of the tantalum capacitor. Can repair major defects. Therefore, the function of the used circuit can be maintained.

According to the second aspect of the present invention, as in the first aspect of the present invention, it is possible to repair the problem of the large leakage current of the tantalum capacitor, and use it by displaying that the problem has been corrected. It is possible to inform the user that the tantalum capacitor is defective. According to the invention of claim 3, when the leakage current of the tantalum capacitor is large and the voltage thereof does not rise above a predetermined voltage, heat is applied to the tantalum capacitor to repair the problem of the large leakage current of the tantalum capacitor. You can Therefore, the function of the circuit to be used can be maintained as in the first and second aspects of the invention.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a circuit of an embodiment of the present invention. This embodiment circuit is an example in which a tantalum capacitor C ₀ is used in a circuit similar to the conventional example of FIG. In the circuit, a comparator IC ₃ that compares the voltage at one end a of the tantalum capacitor C ₀ with a threshold Vth determined by the resistors R ₄ and R ₅ , and the output of this comparator IC ₃ is “H”.
Transistor Q ₂ that turns on when
_{When 2} is turned on, a constant DC voltage (a threshold voltage at which the oxide film inside the tantalum capacitor C ₀ is restored,
For example, a self-repair circuit according to the present invention, which is composed of a transistor Q ₁ for applying 8 V) to the tantalum capacitor C ₀ through the emitter-collector, is additionally provided.

When the leakage current of the tantalum capacitor C ₀ used is large, T _{1 of} FIG.
As indicated by the period, the voltage at one end a of the tantalum capacitor C ₀ rises only gradually. On the other hand, in the comparator C _3, the voltage at the one end a of the tantalum capacitor C ₀ is the threshold value Vth.
As shown in FIG. 2B, the output c is "
Therefore, the "H" output charges the capacitor C ₄ connected to the base circuit of the transistor Tr ₂ through the resistor R _{6 as} shown in FIG. 2 (c), and one end d of the capacitor C ₄ is charged. When the voltage of becomes larger than the threshold value of the base-emitter of the transistor Q _2, the transistor Q ₂ is turned on. this on the flow the base current of the transistor Q ₁ is, the transistor Q ₁ is also turned on. constant through the transistor Q ₁ by the oN A voltage is applied to the capacitor C _2. Therefore, in the tantalum capacitor C ₀ , the oxide film inside is repaired by the application of this constant voltage, and the problem of leakage current is repaired. Is 8V, but usually 5V to 10V
If added, the problem of large leakage current of the tantalum capacitor is repaired.

Therefore, as shown in FIG. 2A, the tantalum capacitor C is started from the time t ₁ when the transistor Q ₂ is turned on.
The voltage of ₀ rises and finally the threshold value Vt of the comparator IC ₃
h will be exceeded. At this time t ₂ , the comparator I
The output of C ₃ becomes “L”, and the transistors Q ₂ and Q ₁
Is turned off, but the voltage of the tantalum capacitor C ₀ is
It rises as shown in (a). When this voltage reaches a certain value (time point t ₃ ), the reset circuit IC ₂ generates a reset release signal as shown in FIG.
It is set to H "and the reset of the microcomputer IC ₁ is released.

That is, the tantalum capacitor C₀Leakage current
Even if it is large, the problem can be repaired and the reset circuit
IC₂The circuit function of can be maintained. (Embodiment 2) This embodiment is a self-repair circuit of Embodiment 1 described above.
On the display circuit section that indicates that the defect has been repaired.
It is a digit. In other words, the display circuit part is_Fourof
When the voltage becomes higher than the threshold between base and emitter
Transistor Q to turn on₃And light emitting diode LED
Anti-R₈Consisting of a series circuit with a transistor Q₂, Q ₁
Turns on and the tantalum capacitor C₀Apply a constant voltage to
When the problem is repaired by₃Is o
Light emitting diode LED to emit light. I mean Tan
Tal capacitor C₀Was repaired from the root
Therefore, it is not possible to use a light emitting diode LED
Internal capacitor C₀Informs the user that the
To let it.

Since the operation of the self-repair circuit is the same as that of the first embodiment, its explanation is omitted. 4A to 4D are waveform diagrams corresponding to FIGS. 2A to 2D, and FIG. 4E shows the voltage of the anode of the light emitting diode LED. (Third Embodiment) The above-mentioned first and second embodiments are tantalum capacitors C.
_Although a constant voltage is applied to ₀ to repair the defect, in this embodiment, the internal oxide film is repaired by heating the tantalum capacitor C _{0. As} shown in FIG. The heater R _H provided near the capacitor C ₀ applies heat to the tantalum capacitor C ₀ to repair the defect.

That is, when the leakage current of the tantalum capacitor C _{0 to be} used is large, the voltage at one end a of the tantalum capacitor C ₀ gradually increases after the power is turned on, as shown in FIG. 6 (a). Meanwhile comparator C ₃ is the voltage of one end a tantalum capacitor C ₀ is the resistance R _4, the period T ₁ does not exceed the threshold value Vth defined by R _5, the output c and "H" as shown in Figure 6 (b). Therefore, the "H" output charges the capacitor C ₄ connected to the base circuit of the transistor Tr ₂ through the resistor R _{6 as} shown in FIG. 6C, and the voltage at the one end d of the capacitor C ₄ is applied to the transistor Q 4. 'becomes greater than the base-emitter threshold of the transistor Q _{2' 1} is turned on. When turned on, a voltage is applied to the heater R _H through the transistor Q ₁ 'and the heater R _H generates heat. This heat generation heats the tantalum capacitor C _{0 and} repairs the problem of large leakage current. Due to this repair, the voltage of the tantalum capacitor C ₀ rises and finally exceeds the threshold value Vth. The output at time t ₂ the comparator IC ₃ becomes an "L", the transistor Q ₁ 'is turned off, repaired voltage tantalum capacitor C ₀ is increased as shown in Figure 4 (a). And to reach a certain value that voltage (time t _3), the reset circuit IC ₂ is set to "H" voltage of point b to generate a reset release signal as shown in FIG. 2 (d), the microcomputer IC ₁ The reset of is released.

[0016]

The invention of claim 1 is used in a circuit in which a certain voltage is applied to a tantalum capacitor, and when the voltage of the tantalum capacitor is below a predetermined voltage after power-on, a constant DC voltage is applied to the tantalum capacitor. Since it consists of voltage applying means for applying to repair the problem of large leakage current of the tantalum capacitor, if the leakage current of the tantalum capacitor is large and the voltage does not rise above a predetermined voltage,
By applying a constant DC voltage to the tantalum capacitor, it is possible to repair the problem of large leakage current of the tantalum capacitor, and thus it is possible to maintain the function of the used circuit.

The invention of claim 2 is used in a circuit in which a certain voltage is applied to a tantalum capacitor, and a constant DC voltage is applied to the tantalum capacitor when the voltage of the tantalum capacitor is below a predetermined voltage after power is turned on. The tantalum capacitor has a voltage applying means for repairing the problem of large leakage current of the tantalum capacitor and a display means for indicating that the problem of large leakage current of the tantalum capacitor has been repaired. There is an effect that the problem of large leakage current can be repaired, and that the user can be informed that the tantalum capacitor being used is defective by displaying that the defect has been corrected.

The invention of claim 3 is used in a circuit in which a certain voltage is applied to a tantalum capacitor, and when the voltage of the tantalum capacitor is equal to or lower than a predetermined voltage after power is turned on, heat is applied to the tantalum capacitor so that the tantalum capacitor is heated. It consists of heat generating means for repairing the problem of large leakage current, so if the leakage current of the tantalum capacitor is large and the voltage does not rise above the specified voltage, heat is applied to the tantalum capacitor to increase the leakage current of the tantalum capacitor. The defect can be repaired. Therefore, like the inventions of claims 1 and 2, there is an effect that the function of the used circuit can be maintained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the above.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a waveform diagram for explaining the operation of the above.

FIG. 5 is a circuit diagram of a third embodiment of the present invention.

FIG. 6 is a waveform diagram for explaining the operation of the above.

FIG. 7 is a circuit diagram of a conventional example.

FIG. 8 is a waveform diagram for explaining the same operation as above.

[Explanation of symbols]

C ₀ tantalum capacitor IC ₁ microcomputer IC ₂ reset circuit IC ₃ comparator Q ₁ , Q ₂ transistor

Claims (3)

[Claims] 1. A tantalum capacitor is used in a circuit for applying a certain voltage to a tantalum capacitor, and when the voltage of the tantalum capacitor is below a predetermined voltage after power-on, a constant DC voltage is applied to the tantalum capacitor to leak the tantalum capacitor. A tantalum capacitor self-repair circuit comprising a voltage applying means for repairing a problem of large current. 2. A tantalum capacitor used in a circuit in which a certain voltage is applied to a tantalum capacitor, and when the voltage of the tantalum capacitor is below a predetermined voltage after power-on, a constant DC voltage is applied to the tantalum capacitor to leak the tantalum capacitor. A tantalum capacitor self-healing circuit comprising: a voltage applying unit for repairing a defect of large current and a display unit for displaying that the defect of large leakage current of the tantalum capacitor has been repaired. 3. A tantalum capacitor, which is used in a circuit to which a certain voltage is applied, is used, and when the voltage of the tantalum capacitor is below a predetermined voltage after power is turned on, heat is applied to the tantalum capacitor to cause a large leakage current of the tantalum capacitor. A self-healing circuit for a tantalum capacitor, characterized in that it comprises a heating means for repairing.