This article introduces the topologies implemented in Emergency Lighting Applications and the use of STMicroelectronics' power bipolar transistors. STSA851 is a power bipolar transistor with high gain performance and low saturation voltage. It is suitable for the drive circuit of emergency lamps.
This document is an application note from STMicroelectronics focusing on the STSA851 power bipolar transistor. It explains how this device is utilized in emergency lighting systems, specifically highlighting its suitability for driving fluorescent tubes in DC-AC converter circuits. The note covers the device's electrical characteristics and its operation within specific voltage and current ranges required for these applications.
The text details two main converter topologies: the Push-Pull current fed converter and the Forward converter. It provides a technical analysis of the circuit behavior before and after the fluorescent tube strikes, including voltage and current waveforms. The document also includes mathematical derivations for transformer windings and voltage calculations relevant to the Push-Pull topology.
The applications typically drive a lamp up to 58W, though they usually supply only 10-20% of the nominal lamp power.
These applications are capable of driving a lamp with a maximum power of 58 W.
After striking, the voltage drops to a peak of 220 V.