Novel Offline Switched Mode Power Supplies for Solid State Lighting Applications

摘要: In recent years, high brightness light emitting diodes (HBLEDs) have increasingly attracted the interest of both industrial manufacturers and academic research community. Among several aspects that make LED technology so attractive, most appreciated characteristics are related to their robustness, efficiency, small size, easy dimming capability, long lifetime, very short switch-on/switch-off times mercury free manufacturing. Even if all such qualities would seem give solid state lighting a clear advantage over other kinds competing technologies, issues deriving from need improvement, on one hand, development suitable electronic ballasts properly drive sources, other, far hindered expected practical applications. The latter problem, in particular, is nowadays considered main bottleneck view widespread diffusion general market, as replacement still dominant solutions, namely halogen fluorescent lamps. In fact, it true some devices’ (e.g. temperature dependent performance, quality, efficiency droop, price per lumen, etc…) further improvements, now generally recognized key requirements, for large scale spread lighting, optimization driver. In important specifications lamp ballast are: reliability power factor, output current regulation, low cost volume minimization (especially domestic applications). From this standpoint, goal is, therefore, find out simple switched mode converter topologies, characterized by reduced component count current/voltage stresses, avoid use lifetime devices like electrolytic capacitors. Moreover, compactness major issue, also soft switching capability becomes mandatory, order enable reactive components increasing frequency range hundreds kHz without significantly affecting converter’s efficiency. It worth mentioning that, optimize HBLED operation, matters, thermal management concern, should be addressed minimize stress suffered and, consequently, deterioration quality lifetime. However, being work focused innovative driving aforementioned problems, topics improvement technology, will left aside. The presented thesis indeed, out, analyze new capable matching previously described successfully facing many challenges dictated future lighting. First all, overview features, art market provided. After first introduction, offline concern extensively discussed different ways approaching depending specific application considered, described. The kind approach investigated based structure relying single conversion stage, concurrently ensuring: compliance with standards limiting input harmonics, regulation load galvanic isolation. The constraints fulfil EN 61000-3-2 harmonics standard when using solution (<15W) purposes, discussed. A cost, count, converter, asymmetrical half bridge flyback topology, has been studied, developed optimized. simplicity compactness, characterizing solution, good option CFL bulb applications, which mandatory reach placing whole circuitry E27 sockets. analysis performed presented, together design procedure, simulation outcomes control techniques were implemented tested converter's laboratory prototype. Another interesting approach, integrated topologies two stages merged sharing same switch circuitry. In resulting factor correction thus combined semi-stages managed shared switch. Compared conventional two-stages configuration, lower circuit complexity higher can achieved through integration, at increased levels losing degree freedom design. Galvanic isolation provided or not selected integration. If non-isolated semi-stages, user safety guaranteed assuring mechanical throughout case. The smoothing pulsating absorbed line while avoiding capacitors, addressed. A set used supplies, generalized presented. Their voltage ripple attenuation examined procedure described. Moreover, novel double buck an about 15W rated down-lighting performed, concerns carefully tests level provided. The last multi-stage results medium street concern. By adopting possible behavior side, thereby guaranteeing effective proper output. Galvanic either stage additional intermediate isolated DC-DC (operating open loop constant input/output ratio) turns AC/DC topology into three configuration. multiple energy processing along path between utility grid load, effectively thanks flexibility relaxing constraint, allows easily each stage. 150W nominal (three stage) investigated. simulations described, well experimental made prototype.