Stability Analysis of Multiple LEDs Dimming Circuits: An Interaction between an LC Input Filter and Two Buck Converters
Abstract
This paper proposes an average modeling of LED dimming circuits controlled by an indirect sliding mode technique. The circuit and control parameters that affect a multiple LED dimming system's stability are studied. The dimming system comprises two output-capacitorless buck converters and each converter connected to two strings of LEDs as a load. These dimming buck converters are connected to a 48 V power source via an LC filter to reduce the input ripple current. It is known that fast response dc-dc converter might lead to unstable operation of the system due to its negative input resistance characteristic. This paper investigates the control parameters of the sliding control that affect dynamics of a DC bus due to the change of the operating point of LED. The theoretical model is validated through experimental results obtained from the test bench.