Application of Super Capacitor in Rectifier filter(II)

3. Possibility of supercapacitors as rectifier filter capacitors

    For supercapacitors, it can easily reach Farah capacity, so supercapacitors have enough capacity as rectifier filter. In the past, the rated voltage of supercapacitors was relatively low, although it can be solved by the way of multiple series, but after the series of supercapacitors will lead to the increase of ESR, thus increasing the problem of ESR. The main reason why supercapacitors can not be used for rectifying and filtering at the output end is that the filter capacitors are required to have the lowest possible ESR when rectifying and filtering at the output end of the switching power supply, whereas the previous supercapacitors have a large ESR after several supercapacitors are in series. This causes supercapacitors to heat up when used for output rectifier filtering. For example, when five 4.7F supercapacitors are used in series, their ESR is about 300m Ω. In this case, if the output current on the supercapacitor is 1.2W, the power will cause the supercapacitor to heat up seriously.But now supercapacitors have reached very high levels, such as AVX's production of a series of bestcap. ®Supercapacitors, with both high rated voltage and low ESR, For example, a 90mF / 12V bestcap. ®The ESR of supercapacitor is about 90m Ω, which is much smaller than 300m Ω. Can see the best cap. ®The ESR of supercapacitors is much lower than that of previous supercapacitors, which can solve the problem of rated voltage and ESR at the same time; the remaining question is whether the corresponding ripple current can meet the requirements. When the suitable capacitance is selected (for example, the load current per amperes is 1000 ~ 10 000 μ F / L), the aluminum electrolytic capacitor does not bear ripple current basically, and its ESR is relatively low, and the effect produced by the capacitor has almost no effect on the aluminum electrolytic capacitor. Bestcap. ®The ESR of supercapacitor is similar to that of aluminum electrolytic capacitor, and it has very good impedance frequency characteristic, so bestcap. ®Supercapacitors can withstand the corresponding ripple current. Figure 1 is bestcap. ®Impedance frequency characteristic diagram of supercapacitor. This shows that the best cap. ®Super capacitor is suitable for output rectifier filtering.