Upon accepting an invitation from Aetas Technology Incorporated to help develop a small, low cost charging system to charge a photoreceptor in a xerographic full color printer, we designed a charger by connecting an AC corona voltage to the coronode through a high voltage capacitor. In this manner, the capacitor will automatically bias itself to whatever voltage is needed to ensure equal positive and negative corona currents from the wire. The corona wire was partially surrounded by a conducting channel shield biased to the desired asymptote DC potential. The connection through the self-biasing high voltage capacitor produced I-V curves that were concaved downward. This proved to give profound advantages of a more definitive asymptote, and hence better charging uniformity, as well as higher efficiency, permitting higher process speeds.
R. W. Gundlach, A. Fornalik, W. Mey, "New Corona Charging System For Low Cost Printers" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP18), 2002, pp 41 - 44, https://doi.org/10.2352/ISSN.2169-4451.2002.18.1.art00012_1