Application of Super Capacitor in Rectifier filter

1.Foreword

     Filter capacitor plays an important role in the rectifier filter circuit, the larger the capacitance, the better the filtering effect. Especially in the low-voltage rectifier (such as 5V, 3.3V or lower voltage) output, because the filter capacitor capacity is not large enough to produce a larger ripple voltage. The test results show that the filter capacitors with 1000, 2200, 3300, 4700 and 10000 micrometers are used in the output of 1A current. The peak values of ripple voltage are: 6 V, 2.8 V, 1.9 V, 1.1 V and 0.6 V, respectively. If a larger filter capacitor is used, the filtering effect will be better. The problem is large capacitors. How can we solve this problem? People immediately wonder whether supercapacitors can be used for rectifier filtering. This paper will give detailed analysis and test results through theoretical analysis and experiments.

2. The basic requirements of rectifier filter for capacitors

     In the switching power supply, the output rectifier filter has four basic requirements for the capacitor. They are: sufficient capacitance, rated voltage that meets the requirements, ESRs (equivalent series resistance) that meet the requirements and can withstand the corresponding ripple current value. Only when these four basic requirements are met at the same time, the supercapacitor can be used in the output rectifier filter of the switching power supply.