An efficient dual-stage power supply topology for series connected control devices in intelligent lighting systems

A typical problem in modern intelligent lighting systems is the power supply of smart control devices replacing conventional, series connected light switches or dimmers. This paper proposes a two-stage power supply concept that overcomes the involved issues and compares it to a recently published work [1]. Both concepts can operate without a neutral wire connection at the light switch lead out. The power supply shown in this work consists of a flyback converter as the input stage and a buck converter as the output stage, whereas the concept presented in [1] works with a boost converter as the first stage and a flyback converter as the second stage. The comparison of these two power supply topologies relies on measurement data and evaluates both concepts regarding efficiency, maximum output power, complexity and robustness. Both power supplies are directly attached to the utility grid and hence cope with a high voltage ratio from 230 V_RMS alternating current (AC) mains to a constant direct current (DC) output voltage of 3.3 V. For the comparison the power supplies are exemplarily examined in compliance with the Digital Load-Side Transmission (DLT) standard [2]. It is shown that both concepts can handle these highly discontinuous input voltages while providing a maximum output power high enough to operate even power hungry devices, such as liquid crystal display (LCD) backlights or a WiFi module.