Transformerless electroluminescent lamp driver topology

Abstract

A transformerless driver circuit for an EL device has a battery or other source of dc power, and a microcontroller that is suitably programmed with associated firmware, so that a first switch control signal appears at a first output and a second switch control signal appears at a second output. A flyback circuit is connected to the first microcontroller output and, through a diode, to a charge storage device, e.g., a capacitor. This charges the capacitor stepwise to a relatively high voltage. The flyback circuit includes an inductor having one end connected to a first terminal of the dc power source, and another end coupled to a transistor or similar switch element. The transistor is coupled to the second dc power terminal, and has a base or gate coupled to the first output of the microcomputer. A controlled discharge arrangement bridges across the charge storage device to discharge the same periodically, and create an alternating current to drive the EL device. A second transistor has its base or gate coupled to the microcontroller second output. An isolating capacitor can be positioned in series between the diode and the charge storage device to eliminate the dc offset to the EL element. In one alternative arrangement, two or more flyback circuits are gated on and off sequentially. In a power-saver arrangement, the discharge circuit returns charge back to the battery.