Permanent Emergency LED Lamp Based on a Series Single-Switch Resonant Converter With Battery Clamp

Permanent emergency lighting is a safety device whose lamp is always on and continues to operate when a mains failure occurs. The circuit has to charge the battery and drive the lamp while the grid is present and keep the lamp running from the battery in case of mains failure. This might require up to three different converters: front-end converter, electronic ballast, and battery charger. Since an emergency lamp must be on for as long as the local regulations require during a grid failure, efficiency is key. This article presents a permanent emergency lamp based on a series resonant current regulator that operates both as a ballast and as a battery charger. In this circuit, the power converter is placed in series with the LED array, operating as a controllable nondissipative impedance. A methodology based on the study of energy balances during resonant operation intervals is presented, aiming to design and build a laboratory prototype with low component count and high efficiency.