JPS63165770A - Circuit for detecting deterioration of electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enhance the reliability of a power source circuit, by providing a low-band filter circuit for removing the high frequency noise contained in a detection voltage level to a comparing circuit performing the judgement of the deterioration state of a smoothing capacitor. CONSTITUTION:The voltage between the terminals of a smoothing capacitor 18 is taken out and the high frequency noise containing in said voltage is removed by a low-band filter circuit consisting of resistors R1, R2 and a capacitor C1. The ripple voltage thus obtained is set to a detection voltage level to be inputted to the negative side terminal of a comparator 28. The comparator 28 compares said detection voltage level with the reference voltage level inputted to the positive side terminal of said comparator 28 and outputs a high level output signal only for a period when the detection voltage level is lower than the reference voltage level. At this time, a predetermined width is generated at the operation point of the comparator 28 by the action of a histeresis resistor 7. Therefore, when the ripple voltage increases by the deterioration of the capacitor and becomes larger than the operation width of the comparator 28, the output signal of the comparator 28 is smoothed by an integration circuit consisting of a resistor R8 and a capacitor C3 and a comparator 44 or an alarm 46 is appropriately energized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a deterioration detection circuit for an electrolytic capacitor used in a smoothing circuit in a power supply device configured to rectify an alternating current voltage to obtain a direct current voltage.

[Conventional technology]

In general, it is used to stabilize switching regulators, etc. equipped with power supply circuits that convert AC voltage to DC voltage and DC-DC converters that convert DC input voltage to AC, transform it to an arbitrary voltage, and then rectify it to obtain DC output voltage. In power supply devices, electrolytic capacitors, which are inexpensive and have a large capacity, are used to smooth DC output.

As described above, the reliability of today's stabilized power supplies, as typified by switching regulators, has improved, but on the other hand, electrolytic capacitors still undergo chemical changes and are difficult to avoid deteriorating over time. There is the inconvenience that it cannot be converted and must be converted periodically over its lifespan.

Generally, it is known that the deterioration state of a capacitor appears as an increase in dielectric loss tangent (tanσ), equivalent series resistance (ESR), or leakage current as the capacitance decreases over time.

However, in order to detect these deterioration characteristics of a capacitor, it is necessary to remove the capacitor from the circuit and measure each capacitor individually, which not only requires a lot of effort and time, but also requires the circuit operation to be temporarily stopped. There is this inconvenience.

From this point of view, conventional methods for detecting the deterioration state of this type of capacitor include detecting heat generated due to increased internal loss of the capacitor and tart-like deformation of the internal mechanism or exterior body of the capacitor due to this. Accordingly, various protection methods have been proposed in which a dangerous state in which a capacitor deteriorates and breaks ↑h is detected in advance and safety operations such as circuit interruption are performed.

However, the conventional deterioration detection method for capacitors described above detects overheating of the capacitor and deformation of the condenser's constituent members, so the deterioration of the capacitor has progressed considerably, and during this time the electrical characteristics of the capacitor has deteriorated significantly, and the negative impact on highly reliable power supply circuits is extremely large.

Therefore, the applicant first proposed a smoothing defrost solution in a power supply circuit configured to smooth a DC voltage including ripples obtained by rectifying an AC voltage, etc. via a smoothing electrolytic capacitor and supplying the smoothed voltage to a load. By detecting the ripple included in the voltage between the terminals of the capacitor with a voltage detection circuit installed so as not to affect the circuit and constantly monitoring it, as the deterioration of the smoothing electrolytic capacitor progresses, it will become normal. Since the ripple voltage value gradually increases compared to the smoothing electrolytic capacitor of We proposed a device for detecting the lifespan of smoothing capacitors and filed a patent application.

FIG. 3 is a stabilized power supply circuit diagram showing an example of the structure of the smoothing capacitor life detection device according to the patent application. In FIG. 3, reference numeral 10 indicates a transformer, and after rectifying the alternating current voltage generated on the output side of the transformer 10 by a diode rectifier 12 and ]4, a smoothing capacitor 16 and a smoothing capacitor 18 are used. The circuit smoothes and generates the required DC output. Here, the ripple voltage of the smoothing capacitor 18 is taken out from the output voltage by the capacitor +C1, inputted into an average value detection circuit consisting of operational amplifiers 20 and 22, and a DC voltage proportional to the output ripple voltage amplitude is taken out. The voltage is configured to be inputted to one input terminal of the comparator 28 as a required voltage level via R7. Further, a reference power supply 30 is provided to set a voltage level based on the ripple voltage when a normal smoothing capacitor is used, and this reference power supply voltage is applied to the other side of the comparator 28 via a voltage dividing resistor R8°R7. It is configured to be input to the input terminal as a reference voltage level.

Therefore, the comparator 28 compares the reference voltage level with the voltage level that decreases due to a decrease in ripple current due to deterioration of the smoothing capacitor 18, and when the deviation exceeds an allowable level, a predetermined voltage level is set. Set to output the output signal. As a result, the output signal of the comparison "1528 can appropriately turn on the switching element 32 and energize the display element or the alarm 34.

[Problem that the invention seeks to solve]

In the above-mentioned smoothing capacitor life detection device, the voltage between the terminals of the smoothing electrolytic capacitor is detected, this is converted to a DC voltage proportional to the output ripple voltage amplitude by the average value detection circuit, and this DC voltage is used as the detection voltage. The deterioration state of the smoothing electrolytic capacitor is determined by inputting the level to a comparison circuit and comparing it with a predetermined reference voltage level.

In contrast, by inputting the DC output including the ripple generated between the terminals of the smoothing electrolytic capacitor as it is to the comparison circuit as a detection voltage level and performing a comparison operation with a predetermined reference voltage level, smoothing It is also possible to determine the state of deterioration of the electrolytic capacitor.

Therefore, an object of the present invention is to directly input the DC output including the ripple generated between the terminals of the smoothing electrolytic capacitor to a comparator circuit to detect the increase in the 'J-/pull amount, and as a result, the operating state The present invention provides an electrolytic capacitor deterioration detection circuit that can easily determine the deterioration of an electrolytic capacitor.

[Means for solving problems]

In the electrolytic capacitor deterioration detection circuit according to the present invention, a DC voltage including a ripple component obtained by rectifying an AC voltage or a pulse voltage is supplied to a smoothing circuit including a smoothing electrolytic capacitor, and the smoothed voltage is applied to a load. In the power supply circuit configured to supply the smoothing electrolytic capacitor, a comparison circuit is provided that detects a ripple voltage generated between the terminals of the smoothing electrolytic capacitor and compares it with a predetermined reference voltage to determine a deterioration state of the smoothing electrolytic capacitor. The present invention is characterized in that a low-pass filter circuit for removing high-frequency noise contained in the detected ripple voltage is provided on the input side of the comparison circuit.

[Effect]

According to the electrolytic capacitor deterioration detection circuit according to the present invention,
In a power supply circuit configured to smooth a DC voltage including a ripple obtained by smoothing an AC voltage, etc. through a smoothing electrolytic capacitor and supplying the smoothed voltage to a load, the ripple voltage of the smoothing electrolytic capacitor is detected and a predetermined voltage is applied. The deterioration state of the smoothing electrolytic capacitor can be easily determined by comparing the amplitude of the detected ripple voltage with the reference signal.

In addition, high-frequency noise included in the detection voltage level is removed via a low-pass filter for the comparison circuit that determines the deterioration state of the smoothing electrolytic capacitor, thereby effectively preventing malfunction of the comparison circuit due to the noise. It can be prevented.

〔Example〕

Next, embodiments of the electrolytic capacitor deterioration detection circuit according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a stabilized power supply circuit diagram showing an embodiment of the deterioration detection circuit of the present invention. Components that are the same as those in the circuit shown in FIG. 3 are designated by the same reference numerals, and detailed explanation thereof will be omitted. That is, in FIG.
0 indicates a transformer, and stabilization is achieved by connecting and arranging a rectifier circuit consisting of diode rectifiers 12 and 14, a smoothing circuit consisting of a smoothing coil 16, and a smoothing capacitor 18 using an electrolytic capacitor to the output side of the transformer 10. The configuration of the power supply circuit is similar to the circuit shown in FIG.

Therefore, in this embodiment, a resistor R1 and a capacitor C4 are connected in series to the (+) side output terminal of the power supply circuit, and a resistor R2 is connected in parallel to this capacitor C1 to provide a low-pass filter. A circuit is constructed, and the connection point (2) between the resistor R1 and the capacitor C is connected to the (-) side terminal of the comparator 28 via the resistor R1. in this case,
The resistor R1 and capacitor C1 are connected to the power supply line through a 50° Zener diode capacitor C1, a 1° resistor WR, and a diode rectifier 48 to the output side of the transformer 10, so that the ripple contained in the power supply voltage is is absorbed by the Zener diode 50. In addition, a resistor R1 and Zener diodes 36 and 38 are connected in series to the (+HIII) output terminal of the power supply circuit, and the DC voltage generated at the connection point of the Zener diodes 36 and 38 is passed through voltage dividing resistors R7 and R6. and is input as a reference voltage level to the (+) side terminal of the comparator 28. Here, the (+) side input terminal and output terminal of this comparator 28 are connected through a resistor R2. , the circuit is configured to give a predetermined hysteresis to the comparator 28. An amplifier circuit including a transistor 40 is connected to the (+) (III output terminal) of the power supply circuit, and the output voltage of this amplifier circuit is The circuit is configured so that it is input to the power input terminal of the comparator 28.

Furthermore, in step 1, a resistor R8 and a capacitor C1 are connected to the output terminal of the comparator 28 via a diode rectifier 42, and a resistor R9 is connected in parallel to the capacitor C1 to form an integrating circuit. , the connection point between the resistor R8 and the capacitor C1 is input to the (-) side terminal of the comparator 44 via the resistor R1°. Also, this comparator 4
The circuit is configured such that the DC voltage generated by the Zener diodes 36 and 38 is input to the (+) side terminal of 4 through voltage dividing resistors R1) and R1)'. Note that the (+) side input terminal and output terminal of this comparator 44 are connected to a resistor R0. Further, an alarm vr46 is connected to the output end of this comparator 44 via a resistor R14, and the other connection end of this alarm 46 is connected to the output side of the transistor 40.

Next, the operation of the deterioration detection circuit configured as described above will be explained with reference to the voltage waveform diagrams shown in FIGS. 2(1) to (4). In the circuit shown in Fig. 1, the voltage between the terminals of the smoothing capacitor 18 is taken out (Fig. 2 (1)), the high frequency noise contained in the taken out voltage is removed by the resistor R1,
The ripple voltage thus obtained, which is removed by a low-pass filter circuit consisting of R2 and capacitor C1 (Fig. 2 (2)), is applied to the comparator 2 as a detection voltage level.
The comparator 28 compares this detection voltage level with the reference voltage level input to the (+) side terminal, and detects the detection voltage input to the (-) side terminal. A high-level output signal is output only during the period when the level is lower than the reference voltage level input to the (+) side terminal.
Figure (3)]. At this time, due to the action of the hysteresis resistor Rr, a predetermined width is generated at the operating point of the comparator 28, as shown in FIG. 2(2). Therefore, the ripple voltage of the new capacitor falls within the operating range of this comparator 28, and the
8 does not operate, but when the ripple voltage increases due to deterioration of the capacitor and becomes larger than the operating width of the comparator 28, the comparator 28 operates and outputs a high-level output signal. The output signal of this comparator 24 is smoothed by an integrating circuit consisting of a resistor R8 and a capacitor C1 [FIG. 2 (4)], and this smoothed voltage signal is used to
Alternatively, the alarm 46 is activated as appropriate.

[Effects of the Invention] As is clear from the embodiments described above, according to the present invention,
In a power supply circuit configured to smooth a DC voltage including ripple obtained by rectifying an AC voltage, etc. via a smoothing electrolytic capacitor and supplying the smoothed voltage to a load, the ripple voltage of the smoothing electrolytic capacitor is detected. The deterioration state of the smoothing electrolytic capacitor can be easily and simply determined by comparing the amplitude of the detected ripple voltage with a predetermined reference signal and performing the necessary i-reporting operation.

Further, by providing a low-pass filter circuit for removing high-frequency noise included in the detection voltage level to the comparison circuit that determines the deterioration state of the smoothing electrolytic capacitor, malfunction of the comparison circuit due to the noise is prevented. By inputting the ripple generated between the terminals of the smoothing electrolytic capacitor as is into the comparison circuit, the deterioration state of the smoothing electrolytic capacitor can be properly determined, improving the reliability of this type of power supination. This can also be achieved at low cost.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a stabilized power supply circuit diagram showing an embodiment of the electrolytic capacitor deterioration detection circuit according to the present invention, and FIG. 2 is a voltage waveform showing the output waveform at each point of the circuit shown in FIG. 3 are stabilized power supply circuit diagrams showing an example of the configuration of a smoothing capacitor life detection device. 10, , , transformer 12.14, 24, 26, 42, 48. ,, Diode rectifier 16, , Smoothing coil 1B, , Smoothing capacitor 20.22. ,, operational amplifier 28.44. ,
, comparator 30, , power supply 32,40. ,,
Transistor 34.46. ,, alarm

Claims (1)

[Claims] (1) In a power supply circuit configured such that a DC voltage including ripples obtained by rectifying an AC voltage or a pulse voltage is supplied to a smoothing circuit including a smoothing electrolytic capacitor, and the smoothed voltage is supplied to a load, A comparison circuit is provided for detecting the ripple voltage generated between the terminals of the smoothing electrolytic capacitor and comparing it with a predetermined reference voltage to determine the deterioration state of the smoothing electrolytic capacitor. A deterioration detection circuit for an electrolytic capacitor, comprising a low-pass filter circuit that removes high-frequency noise contained in a detected ripple voltage.