KR19990050114A - Inverter capacitor replacement time alarm circuit - Google Patents

Abstract

The present invention relates to a capacitor replacement time alarm circuit of an inverter, comprising: a ripple voltage detector for detecting a ripple voltage of an AC component included in a voltage smoothed through the capacitor connected to both ends of a capacitor installed in a rectifier of the inverter. And a warning unit for comparing the level with a voltage of a predetermined level and outputting a signal corresponding thereto, and an alarm unit for notifying the replacement time of the capacitor according to the output signal of the comparing unit. Therefore, it is possible to economically change the replacement time by alerting the reduction of the capacitance caused by the deterioration characteristic of the smoothing capacitor from the ripple voltage so that it can be replaced, thereby preventing the accident of the connected system in advance.

Description

Inverter capacitor replacement time alarm circuit

The present invention relates to an alarm circuit for replacing a capacitor of an inverter, and more particularly, to determine the degree of capacitance reduction according to the service life of a smoothing capacitor mounted in an inverter, and to replace the capacitor of an inverter to recognize the replacement time. It relates to an alarm circuit.

An inverter is a device for converting a commercial sine wave AC voltage and outputting a DC voltage of a predetermined level or an AC voltage modulated with an amplitude and a frequency required by an application device.

In order to improve the power conversion efficiency, the inverter that functions as described above is mostly applied to the pulse width modulation method, and is a voltage source required by a rectifier that smoothly rectifies commercial AC voltage and applies a DC voltage smoothed by the rectifier. The switching unit includes an appropriate switching method according to, for example, voltage level, power consumption, allowable voltage fluctuation range, and the like.

1 is a view schematically showing a typical AC-DC conversion inverter.

Referring to this, the inverter includes a rectifying part made of a smoothing electrolytic capacitor 3 for smoothing the pulsed voltage output through the bridge diode 2 and the bridge diode 2 to rectify the commercial AC voltage 1, and And a secondary rectifier 5 for smoothing and outputting the voltage induced by the turns ratio.

In the conventional inverter as described above, the electrolytic capacitor 3 connected to smooth the commercial AC voltage 1 has a lifespan reduced by half of the lifespan when the operating ambient temperature rises 10 degrees above the set allowable temperature, and vice versa. If the temperature is lowered by 10 degrees, the lifespan is twice as long as the guaranteed life. In addition, the electrolytic capacitor 3, whose characteristics and lifespan are very sensitive to heat, has a rapid decrease in performance, i.e. capacitance, due to continuous heat generation by the internal resistance component after the charging and discharging operation is performed for a predetermined time. The lifetime of the inverter is extended because the guaranteed life of a conventional electrolytic capacitor 3 is about 2000 to 3000 hours at an operating temperature of 85 degrees or 105 degrees, and the extension of the guaranteed life is achieved by lowering the operating temperature of the electrolytic capacitor 3. It depends on the electrolytic capacitor 3.

Therefore, the electrolytic capacitor 3 used for a certain time gradually decreases the capacitance value due to deterioration, and accordingly, the amplitude of the ripple voltage after smoothing increases, affecting the operation of the switching element and other components. In addition, the voltage at the output stage is also outside the range of voltage fluctuations required for the smooth operation of the device, which interferes with the normal operation of the system using the output voltage, and components sensitive to voltage fluctuations may be damaged.

Conventionally, in order to reduce the performance and extend the life of the inverter, a method of replacing the electrolytic capacitor 3 by setting a predetermined regular replacement time has also been performed, but the operating temperature and the operating time of the inverter are not accurately monitored and checked. Because the replacement is made in the United States, there is a problem in that proper countermeasures are not taken, such as the possibility of destroying the device by missing an unnecessary replacement or replacement time.

The present invention has been made to improve the above problems, and an object of the present invention is to provide a capacitor replacement time alarm circuit of an inverter that enables the external device to properly recognize an exchange time of an electrolytic capacitor through ripple voltage monitoring.

1 is a view schematically showing a typical AC-DC conversion inverter,

2 is a block diagram showing a capacitor replacement time alarm circuit of the inverter according to the present invention;

3 is a graph showing the voltage across the capacitor of the inverter of FIG. 2 according to the inverter operating time,

4 is a circuit diagram showing a configuration according to a preferred embodiment of the capacitor replacement timing alarm circuit of the inverter of FIG.

5 is a view showing a circuit configuration according to another embodiment of the alarm means.

<Description of Symbols for Major Parts of Drawings>

1, 11: AC power supply 2, 12: bridge diode

3, 13: electrolytic capacitor 4: switching unit

5: secondary rectifier 20: ripple voltage detector

21: first capacitor 22: diode

23: second capacitor 30: comparison unit

31: amplifier 32: comparator

40: alarm means 41, 43: transistor

42: light emitting diodes 44: buzzer

In order to achieve the above object, the capacitor replacement time alarm circuit of the inverter according to the present invention is connected to both ends of the capacitor installed in the rectifier of the inverter to detect the ripple voltage of the AC component included in the voltage smoothed through the capacitor. ; A comparator for comparing the level of the ripple voltage with a predetermined voltage and outputting a signal corresponding thereto; And alarm means for informing the replacement time of the capacitor according to the output signal of the comparator.

The comparator includes an amplifier for amplifying when the signal output from the ripple voltage detector is weak and a comparator for comparing the signal output from the amplifier with a predetermined level, and the alarm means alerts according to the output signal of the comparator. It is preferable to include a buzzer or a light emitting device that lights up.

Hereinafter, a capacitor replacement timing alarm circuit of an inverter according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 is a block diagram showing a capacitor replacement time alarm circuit of the inverter according to the present invention.

Referring to this, the capacitor replacement time alarm circuit of the inverter includes a rectifier connected to the bridge diode 12 and the capacitor 13, a ripple voltage detector 20 detecting the ripple voltage across the capacitor, and a detected ripple voltage. And a comparison unit 30 for determining and comparing with each other, and an alarm unit 40 for recognizing the outside according to a signal output from the comparison unit 30. The rectifier is for smoothing AC power to DC power, and various methods such as half-wave rectification are used depending on the number and method of diodes connected to the front end of the smoothing capacitor 13.

When the AC power is rectified through the bridge diode 12 and the electrolytic capacitor 13, the voltage across the capacitor 13 is changed to include the ripple voltage due to charge and discharge in the DC voltage level. When the capacitance of the capacitor 13 is reduced in this operating relationship, the width of the initial ripple voltage (rp1) is the amplitude of rp2 as shown in FIG. Is raised.

Therefore, by monitoring the degree of variation in the ripple voltage, it is possible to predict the change in capacitance of the electrolytic capacitor 13, and the replacement time may be determined accordingly.

According to this principle, a more specific signal processing relationship will be described in more detail with reference to FIG. 4.

4 is a circuit diagram illustrating a configuration of a preferred embodiment of a condenser replacement timing alarm circuit of the inverter of FIG. 2.

First, the ripple voltage detector 20 is configured to filter only an AC component, i.e., a ripple voltage component, among voltage components across the electrolytic capacitor 13, and another signal corresponding to the amplitude of the filtered ripple voltage for easier signal processing. This includes converting to. In the illustrated example, the first capacitor 21 filters only the AC component, that is, the ripple voltage, and the AC voltage filtered by the first capacitor is rectified by the diode 22 and then smoothed by the second capacitor 23. do. Therefore, the voltage smoothed by the second capacitor 23 obtains a substantially negative DC voltage proportional to the amplitude of the ripple voltage and is output to the comparator 30.

The comparator 30 includes an amplifier 31 for amplifying a negative DC voltage signal output from the ripple voltage detector 20 and a comparator 32 for comparing the amplified signal with a reference signal for output. Here, the amplifier 31 is applied for the case where the ripple voltage signal source is weak, and the amplifier 31 may be omitted depending on the ripple voltage signal level. Substantially, reference numerals 31 and 32 are actual OP AMPs.

In the operation, first, the negative DC voltage signal output from the ripple voltage detector is multiplied by -R2 / R1 times by the ratio of the resistance elements R1 and R2 through the amplifier 31, and the positive DC voltage is multiplied. It is divided into resistors R3 and R4 and compared with the reference voltage inputted to thereby output a 1 or 0 on / off signal corresponding to a logical signal.

Here, the reference voltage may be set to a DC signal level value output from the amplifier 31 when a ripple voltage having a threshold value corresponding to the allowable ripple voltage range is applied to the ripple voltage detector 20. Therefore, the amplification factor of the signal corresponding to the ripple voltage in relation to the capacitance of the electrolytic capacitor 13 employed may be adjusted by the ratio of the resistances R1 and R2 connected to the amplifier 31, thereby reducing the capacitance due to deterioration. Determination of the replacement time by means of adjustment is made by adjusting the resistors R3 and R4 which diverge the voltage source Vcc1 with respect to the allowable voltage fluctuation range required by the connected equipment.

The output signal of the comparator 32 is configured to be output as a switch signal such as 1 or 0. In the example shown, the signal 0 is output before the electrolytic capacitor 13 reaches the capacitance reduction set in relation to the reference voltage. When the set capacitance decreases, the signal is converted to 1 and output.

The alarm means 40 is configured such that an alarm function can be recognized externally with respect to such an output signal of the comparator 32. In the illustrated example, when one signal is output from the comparator 32, the transistor 41 is turned on. As a result, the light emitting diodes 42 are operated.

Therefore, when the capacitance is reduced to a level corresponding to the lifetime of the electrolytic capacitor 13, the ripple voltage is increased. When the raised ripple voltage is out of the threshold value, the output of the comparator 32 is 1, that is, high. The light emitting diodes 42 are turned on while the transistor 41 is turned on.

In the illustrated example, the transistor 41 and the light emitting diode 42 are connected to the external power source Vcc2 as the warning means 40. However, the transistor 41 may be formed by various methods. The buzzer 44 may be employed to generate the buzzer sound when the 43 is turned on. In addition, when the replacement time comes, the output signal of the comparator 32 may be used as an input source of the control circuit of the system so that appropriate control such as stopping the operation of the connected system is achieved.

Although the condenser replacement time alarm circuit according to the present invention has been described through an example of an AC-DC conversion inverter, it can be seen that it is applicable to a device employing a rectifier that smoothes AC power to DC.

As described so far, the replacement capacitor timing of the inverter according to the present invention is alerted so that the electrolytic capacitor can be replaced at an appropriate time by the alarm replacement circuit alarming circuit, and the operation of the connected system is delayed. It can be prevented.

Claims (4)

A ripple voltage detector connected to both ends of a capacitor provided in the rectifier of the inverter to detect a ripple voltage of an AC component included in the voltage smoothed through the capacitor; A comparator for comparing the level of the ripple voltage with a predetermined voltage and outputting a signal corresponding thereto; And alarm means for informing the replacement time of the capacitor according to the output signal of the comparator. The circuit of claim 1, wherein the comparator comprises an amplifier for amplifying the signal output from the ripple voltage detector and a comparator for comparing the signal output from the amplifier with a predetermined level. . The circuit of claim 1, wherein the alarm means comprises a buzzer that sounds an alarm sound according to the output signal of the comparator. The circuit of claim 1, wherein the alarm means comprises a light emitting device that is turned on according to an output signal of the comparator.