JPH0783550B2 - Failure determination circuit for electrolytic capacitors for removing power ripple - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention detects and alarms ripples that increase due to deterioration of an electrolytic capacitor for removing ripples after rectification in a power supply circuit that rectifies alternating current to generate direct current. The present invention relates to a circuit for determining a defect of a power ripple removing electrolytic capacitor that is suitable for the operation.

[Conventional technology]

Aluminum electrolytic capacitors are widely used for removing ripples after rectification in a conventional power supply circuit that rectifies AC to generate DC. However, the aluminum electrolytic capacitor has a shorter life than other circuit components, and the capacity of the aluminum electrolytic capacitor due to evaporation (dry-up) of the internal electrolytic solution is reduced, so that the circuit is likely to malfunction. Although this has been pointed out for a switching power supply having a power supply circuit that rectifies an alternating current to obtain a direct current, it is not possible to actually judge the quality of the electrolytic capacitor.

As a device for detecting a failure of this type of capacitor, there is one described in Japanese Utility Model Publication No. Sho 37-6230, which relates to a monitoring device for a capacitor trip device mainly for detecting disconnection of a capacitor circuit, The method and device for detecting disconnection of the capacitor circuit are based on auxiliary transformers and fault disconnection devices, and no consideration is given to detecting deterioration of the capacitor and issuing an alarm.

[Problems to be solved by the invention]

The above-mentioned prior art is for detecting the disconnection of the capacitor circuit in the capacitor trip device and is not considered for detecting the deterioration of the capacitor, and is used in a switching power supply having a power supply circuit that rectifies AC to generate DC. It is not possible to judge the quality by detecting the deterioration of the ripple removing electrolytic capacitor.

An object of the present invention is to prevent deterioration of an electrolytic capacitor that removes ripples after rectification of a power supply circuit that rectifies an alternating current to generate a direct current and to judge pass / fail, thereby preventing a life of the electrolytic capacitor and a circuit failure. Therefore, it is another object of the present invention to provide a defect determination circuit for a power ripple removal electrolytic capacitor that can improve reliability.

[Means for solving problems]

The above-described object is a ripple voltage that generates a pulse when the output voltage of the electrolytic capacitor falls below a predetermined voltage level due to a ripple component in a defective determination circuit for the electrolytic capacitor of an AC / DC conversion circuit having an electrolytic capacitor for removing power ripple. The detecting means, an integrating means composed of a capacitor and a resistor connected in parallel and configured to input and integrate the pulse output from the ripple voltage detecting means, and the output voltage of the capacitor of the integrating means exceeds a predetermined value. This is achieved by providing a drive element that is conductive at this time, an alarm means that outputs an alarm when the drive element is conductive, and a switch means that connects a spare electrolytic capacitor in parallel to the electrolytic capacitor when the drive element is conductive.

[Action]

In the defect determination circuit for the power ripple removing electrolytic capacitor, the ripple voltage of the power ripple removing electrolytic capacitor is detected by the ripple voltage detecting circuit, and the ripple voltage detecting signal is integrated by, for example, an integrating circuit, and the integrated voltage level is detected. The signal can drive the output circuit of the quality determination signal to issue an alarm. This ripple voltage detection circuit has, for example, two sets of circuits for resistance-dividing the voltage across the electrolytic capacitor for removing power ripples. One of the resistance-divided ones is provided with a capacitor to maintain its peak voltage, and the division ratio is the resistance division. It is set so that only the voltage becomes a higher divided voltage, and these two divided voltages are input to the voltage comparator, and the ripple voltage detection signal is output from the voltage comparator. With such a resistance voltage dividing circuit, it is possible to deal with a wide range of DC voltage after AC rectification. Then, the ripple voltage detection signal becomes a pulse-shaped signal which is synchronized with the valley of the ripple voltage, and thus becomes a voltage level signal when integrated by the integrating circuit. Such an integrating circuit prevents erroneous detection at the time of momentary power failure or power-on. When the output voltage level of the integrating circuit becomes equal to or higher than a predetermined voltage, the output circuit of the pass / fail judgment signal operates to warn that the electrolytic capacitor for removing the power supply ripple has deteriorated. Further, even if the alarm is overlooked, the spare electrolytic capacitor is connected in parallel to the deteriorated electrolytic capacitor, so that a failure caused by a power failure can be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a circuit diagram showing an embodiment of a defect judging circuit for an electrolytic capacitor for removing power source ripples according to the present invention. First
In the figure, the failure determination circuit of the electrolytic capacitor for removing power ripple is composed of a ripple voltage detection circuit, an integration circuit of the ripple voltage detection signal, and an output circuit of the pass / fail judgment signal. The voltage across both ends of the power supply ripple removing capacitor is input.

The ripple voltage detection circuit has two sets of resistance voltage divider circuits consisting of voltage divider resistors 1 and 2 and voltage divider resistors 3 and 4 connected between input terminals. In the voltage circuit, a ripple removing capacitor 5 is provided in parallel with the voltage dividing resistor 4 for holding the divided peak voltage. The voltage dividing ratio of these two sets of resistance voltage dividing circuits is set so that the voltage divided by the voltage dividing resistors 1 and 2 is higher than the voltage divided by the voltage dividing resistors 3 and 4.

The voltage divided by the voltage dividing resistors 1 and 2 of the two resistance voltage dividing circuits and the voltage divided by the voltage dividing resistors 3 and 4 and the capacitor 5 are used as a voltage comparator transistor of the differential amplifier. 6 and the base of the transistor 7, respectively, and the output of this differential amplifier becomes a ripple voltage detection signal. The resistor 20 is the emitter resistance of the transistors 6 and 7 of the differential amplifier.

A Zener diode 8 is connected to the load of the transistor 7 of this differential amplifier, and the base of the transistor 10 of the next stage is connected to the load, and the transistor 10 of the next stage and the emitter resistor 9 form a constant current circuit. A parallel circuit of a storage capacitor 11 and a resistor 22 forming an integrating circuit is connected to the load of the transistor 10 of the constant current circuit via a diode 21,
When the transistor 10 is turned on, the capacitor 11 is charged with a constant current. Since the ripple voltage detection signal becomes a pulse signal synchronized with the ripple valley, this pulse signal is integrated by the integrator circuit and converted into a voltage level signal, and the voltage level signal of the capacitor 11 of this integrator circuit outputs the pass / fail judgment signal. It is added to the gate of the thyristor (triac) 12 that forms the circuit, and the voltage of the capacitor 11 rises, causing a thyristor.
When the turn-on voltage of 12 is exceeded, the thyristor 12 turns on and alarms the display lamp and buzzer connected to the output terminal.

FIG. 2 is an example waveform diagram of each part for explaining the operation of FIG. In FIG. 2, first, when the power supply ripple removing capacitor connected to the input terminal of FIG. 1 is a good product, the divided voltage A by the voltage dividing resistors 1 and 2 of the resistance voltage dividing circuit is the solid line of FIG. As shown in, the ripple voltage contained in the direct current after AC rectification, that is, the level difference between the peak and valley voltage levels of the ripple is a normal value, and the voltage dividing resistors 3 and 4 and the ripple removing capacitor of one resistor divider circuit are The divided voltage B from which the ripple component of 5 is removed is set lower than the divided voltage A, and therefore has a constant voltage level as shown by the alternate long and short dash line in FIG. In this way, the divided voltage A is always at a higher level than the divided voltage B, so that the differential amplifier uses the transistor 6
Is on and the transistor 7 is off. Therefore, since the transistor 7 is off, the transistor 10 at the next stage is also off, and at this time, the capacitor 11 of the integrating circuit is turned on.
The voltage across both terminals becomes 0 V, and the thyristor (triac) 12 of the output circuit is turned off.

Next, when the power ripple removing capacitor connected to the input terminal deteriorates, the divided voltage A ₁ by the voltage dividing resistors 1 and 2 is included in the DC after AC rectification as shown by the broken line in FIG. The ripple voltage generated increases and the valley of the ripple becomes an abnormally low value, and the divided voltage B by one of the voltage dividing resistors 3 and 4 is held at the peak value because of the capacitor 5 and becomes substantially the same voltage level. In this way, comparing the divided voltage A ₁ and the divided voltage B, there is a period in which the divided voltage A ₁ becomes a voltage level lower than the divided voltage B in the valley portion of the ripple, and during this period, the differential amplifier Since the transistor 7 is turned on, the transistor 10 at the next stage is also turned on, and as a result, the load is detected by the pulse wave ripple voltage detection signal of the differential amplifier synchronized with the valley of the ripple of the divided voltage A ₁ as shown in FIG. A constant current C determined by the Zener diode 8 and the emitter resistance 9 of the transistor 10 in the next stage flows through the diode 21 to the capacitor 11 of the load integrating circuit to charge the capacitor 11. The voltage across the capacitor 11 of the integrating circuit gradually rises every time a pulse-wave-shaped constant current C flows together with the resistor 22, and when the integrated voltage level reaches the turn-on voltage of the thyristor 12 of the output circuit. The thyristor 12 is turned on and a defect determination signal is output to the output terminal. Therefore, if an indicator lamp or buzzer is connected to the output terminal, an alarm can tell that the power ripple removing capacitor connected to the input terminal has deteriorated.

According to the present embodiment, the input of the differential amplifier remains unstabilized by using the resistance voltage divider circuit by the voltage dividing resistor,
Since the capacitor of the integrating circuit is charged by a constant current, there is no effect of power supply fluctuation, and the voltage immediately after AC rectification can operate over a wide voltage range, and can be used alone as a measuring instrument.

FIG. 3 is a block diagram of an AC / DC converter circuit showing an embodiment of a defect determination circuit for a power supply ripple blocking capacitor according to the present invention. In FIG. 3, an AC / DC converter circuit that rectifies the AC from the AC power supply 23 by the rectifier 13 and converts it to DC has a power supply ripple removal capacitor 14 for removing ripples contained in the DC after AC rectification. To the DC output of the rectifier 13 of this AC / DC converter circuit is inserted a power supply ripple blocking capacitor defect determination circuit 15 as shown in FIG. The alarm device 16 and the relay 17 are connected in parallel, and when the relay 17 operates, the relay contact closes, so that the spare capacitor 18 functions as an electrolytic capacitor for removing power ripple. The resistor 19 is a pre-condenser deterioration preventing resistor for applying a voltage to the pre-condenser 18 to prevent deterioration caused by being left unattended and for preventing the current from flowing to the pre-condenser 18 when the relay 17 is off.

In this AC / DC conversion circuit, when the power ripple removing electrolytic capacitor 14 for removing the ripple of the DC output obtained by rectifying the AC input of the AC power supply 23 by the rectifier 13, the ripple increased due to the deterioration of the electrolytic capacitor 14 is removed. The voltage is detected by the defect determination circuit 15 for the capacitor for removing power supply ripple, and the output is used to activate the alarm device 16 to issue an alarm, and at the same time, the relay 17 is turned on and the spare capacitor 18 is charged through the relay contact to remove the power supply ripple. Since it functions as a use electrolytic capacitor, even if the recognition of the failure determination alarm of the electrolytic capacitor 14 is delayed, it does not cause a failure.

According to this embodiment, the ripple voltage of the electrolytic capacitor for removing ripples of the DC output of the AC / DC exchange circuit is monitored to detect the deterioration due to the dry-up of the electrolytic capacitor due to the increase of the ripple voltage, and to judge the failure before the life ends. Since the capacity can be increased by the auxiliary capacitor at the same time when the alarm is issued, it is particularly effective for a power supply circuit that requires high reliability for emergency use or a power supply circuit that cannot be immediately converted even if the deterioration of the electrolytic capacitor is invented.

〔The invention's effect〕

According to the present invention, the deterioration of the electrolytic capacitor for removing the power ripple can be detected or replaced by a preliminary electrolytic capacitor before the life of the capacitor or the failure of the circuit is reached.
The downtime of the power supply circuit can be minimized and the reliability of the power supply circuit can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a defective judgment circuit for an electrolytic capacitor for removing power ripple according to the present invention, FIG. 2 is a sequence chart of operation waveforms of respective parts in FIG. 1, and FIG. 3 is power ripple removal according to the present invention. FIG. 3 is a block diagram of an AC / DC conversion circuit showing an embodiment of a defect determination circuit for a use electrolytic capacitor. 1 to 4 ... Dividing resistance, 5 ... Capacitor, 6,7 ... Transistor for differential amplification, 8 ... Zener diode, 9 ...
Resistance, 10 ... transistor, 11 ... integrating capacitor,
12 …… Output thyristor, 13 …… Rectifier, 14 …… Power ripple removal electrolytic capacitor, 15 …… Power ripple removal electrolytic capacitor failure judgment circuit, 16 …… Alarm, 17…
… Relay, 18 …… Spare capacitor, 19,20,22 …… Resistance,
21 …… Diode, 23 …… AC power supply.

Claims (1)

[Claims] 1. A ripple for generating a pulse when an output voltage of the electrolytic capacitor falls below a predetermined voltage level due to a ripple component in a defective circuit of the electrolytic capacitor of an AC / DC converting circuit having an electrolytic capacitor for removing a power supply ripple. Voltage detecting means, integrating means composed of a capacitor and a resistor connected in parallel for integrating the pulse output from the ripple voltage detecting means, and the output voltage of the capacitor of the integrating means exceeds a predetermined value. A drive element that is turned on when the drive element is turned on, an alarm means that outputs an alarm when the drive element is turned on, and a switch means that connects a spare electrolytic capacitor in parallel to the electrolytic capacitor when the drive element is turned on. Defect determination circuit for electrolytic capacitor for power supply ripple removal.