US Patent 7102296 Screw-in transformer

An apparatus for providing convenient transforming of electrical energy from a first voltage level to a second voltage level, includes a housing having an end wherein the end includes a conductive threading and a contact for making an electrical connection with a light bulb socket. The apparatus also includes a transformer electrically connected to the electrical connection for receiving power through the light bulb socket and transforming the received electrical energy from the first voltage level to the second voltage level. There is a connection electrically connected to outputs of the transformer to provide power at the second voltage level. The converted power can be used to power a DC-driven device such as an LED.