LED lamps have recently become the most preferred alternative to the conventional incandescent and CFL lamps due to their energy efficiency, cool operation and durability. However, LED lighting requires the use of a proper driver for interfacing. Switched Capacitor (SC) converters use a network of capacitors connected by switches that regulate its charging and discharging. Such converters minimize the requirement of inductances and lend themselves to chip integration. These converters have high power density and a good efficiency by choice of an appropriate topology. But regulation is an issue in switched capacitor converters. This work uses a soft switched hybrid combination of switched capacitor converter and a buck boost converter in a divided configuration to drive multiple LED loads. The switched capacitor uses a modified Fibonacci configuration with lesser number of switches to achieve a high conversion ratio with minimal usage of elements. To achieve higher output and to regulate it against load and supply changes, the buck-boost converter controls the voltage at one terminal while the other terminal is controlled by a SC converter. Bulk of the power transfer is through switched capacitor and fine regulation is achieved through buck boost converter. Additionally, by proper choice of switching strategies, a wide range of output voltages is made possible. One major lacuna in switched converters is the inrush current and this is mitigated with a small inductor in the input and output. This also enables zero current switching of the devices, thereby reducing switching losses. The topology is extendable to multiple outputs. Closed loop simulation results and open loop hardware results have been obtained to validate the concept and analysis.
