{"id":786,"date":"2013-06-27T19:59:15","date_gmt":"2013-06-27T19:59:15","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/?p=786"},"modified":"2013-08-13T21:45:57","modified_gmt":"2013-08-13T21:45:57","slug":"two-stage-power-conversion-architecture-for-an-led-driver-circuit","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2013\/two-stage-power-conversion-architecture-for-an-led-driver-circuit\/","title":{"rendered":"Two-stage Power Conversion Architecture for an LED Driver Circuit"},"content":{"rendered":"

LED lighting promises unprecedented reductions in energy consumption, but it comes with an as-yet unmet demand for high power density, high efficiency, and high-power-factor LED drivers[1<\/a>]<\/sup>. Considering a group of commercial line-interfaced LED drivers in the output power range of 3-30 W, we have found efficiencies in the range of 64-83% and power factors of 0.59-0.96, with no systems achieving both high efficiency and a high power factor. The switching frequencies of these drivers were in the range of 57-104 kHz, with correspondingly low power densities below 5 W\/in3<\/sup>. The size of these drivers was uniformly dominated by magnetic components, and in each case the driver represented a major contribution to overall system size. It may be concluded that power conversion electronics continue to represent a major limitation in solid-state lighting, and that significant improvements in driver efficiency, power density and power factor will be necessary to meet market needs.<\/p>\n

We introduce a merged-two-stage circuit topology and associated circuit design and controls to address these challenges. The proposed approach is suitable for efficient LED drivers operating from either a wide-range dc input voltage or an ac line voltage. This two-stage topology is based on a soft-charged switched-capacitor pre-regulator\/transformation stage and a high-frequency magnetic regulator stage. Soft charging in the switched capacitor circuit, zero voltage switching in the high-frequency regulator circuit, and time-scale controls are used to maintain high efficiency, high power density, and a high power factor. Two implementations of the proposed architecture are demonstrated: a wide input voltage range dc-dc converter and a line interfaced ac-dc converter. The dc-dc converter shows 85-95% efficiency at 20W power across 25-200V input voltage range, and the ac-dc converter achieves 88% efficiency with 0.93 power factor at 8.4W average power[2<\/a>]<\/sup>[3<\/a>]<\/sup>[4<\/a>]<\/sup>[5<\/a>]<\/sup>[6<\/a>]<\/sup>[7<\/a>]<\/sup>[8<\/a>]<\/sup>.<\/p>\n\n\t\t