Flicker free LED backlight driver with Passive Current Balancing and dimming function

This paper analyses a dimmable flicker-free resonant single-switch three-output LED driver with passive current balancing technique. These converters have applications in LED back-lighting or lighting panels. A combined buck-boost-buck converter with a single switch scheme is adopted. Brightness adjustment is done through a dimmer control. With the use of passive current balancing, the current through all the strings are controlled by monitoring current in any one string, which makes control simple. Current balancing is achieved by capacitor charge balancing and done through Zero Current Based (ZCB) switching of the circuit. The proposed LED driver uses only one active switch thus the circuit can be low cost, lightweight and compact. The converter is studied in terms of operating principle, current balancing principle and key circuit parameter design. A MATLAB simulation has been done for a three-set of 22 series LED string, and various parameters are also checked.