Contactless electronic ballast for high brightness LED lamps with positionally dimmed method

Catastrophic failure of light-emitting-diode (LED) lighting systems are often due to the failure of short-lifetime electrolytic storage capacitor or other switching components inside the ballast in LED lighting applications. The system replacement and maintenance costs are high considering the high cost of the LED lamps which are mostly functional. Existing techniques include the total elimination of electrolytic capacitor and the sole use of passive components within a single LED lamp system. In this paper, we propose a contactless LED ballast based on loosely coupled transformer, which isolates electrically the primary and the secondary circuits without mechanical contact. The primary circuit includes ordinary lifetime storage capacitor, main switching components, and control circuitries. The secondary circuit contains the long lifetime LED lamps and passive components. So the system maintenance can be tailored for the different failure-and-replacement cycles of the active primary circuitry and the passive secondary LED lamps to optimize overall system lifetime. In addition, the system is suitable for a total environmentally-shield secondary enclosure application. A primary equivalent voltage regulation and a secondary non-electrical positional dimming method based on the physical separation of the primary and secondary of the contactless transformer are used for brightness maintenance and control. Analysis, design and prototype verification are given for the LED ballast and dimming control.