Hello, I'm new here and I'm not sure if this post belongs here or in a physics forum, but here goes. I'm working on a project to power a 6W (bulb input power) UVC bulb from a low voltage DC battery source (4.5 VDC). This of course requires a high efficiency ballast between the DC supply and the 6W UVC tube itself. Commercially available bulbs for producing UVC (254 nm wavelength) are produced as germicidal fluorescent tubes e.g. a G6T5 bulb. Germicidal bulbs are designed using using clear quartz glass tubes that have below atmospheric pressure. They use a small amount of mercury to produce the UVC wavelength. I am running into ballast difficulty that seems to have something to do with these germicidal bulbs which are different in that they use clear quartz glass with no phosphor coating as in other UVA and UVB bulbs, and perhaps the lower pressure used in germicidal bulbs. DC inverter ballast suppliers and others have stated that their DC inverter ballasts designed for equivalent UVA and UVB bulbs will not reliably work for germicidal bulbs. The issue is somewhat complicated by the fact that these ballasts do NOT supply filament current and instead operate such (hot cathode) bulbs in instant start cold cathode mode. My question is simply ... why do such ballasts work with UVA (i.e. so called 'black lights') and UVB bulbs, but not with the UVC germicidal bulbs. It has to be something to do with the lower pressure used with germicidal bulbs together with their clear quartz glass construction as these are the only differences. Might it have something to do with the reduced opacity of the quartz glass allowing internal discharge heat to escape making the bulb run cooler compared with opaque UVA and UVB bulbs? I'm at a loss for an explanation, understanding and some kind of circuit design solution. Any ideas? Thanks in advance.