Interleaved Buck Converter Applied to High-Power HID Lamps Supply: Design, Modeling and Control

As the output current levels of power converters increase, interleaved topologies become widely used. A well-known topology is the interleaved buck converter (IBC), which presents as main characteristic an inherent low ripple output current source behavior in addition to high efficiency and small volume. At the same time, it is necessary to drive high-intensity discharge (HID) lamps with nearly constant current/power and low-frequency square-wave shape due to HID lamp voltage source characteristics and their acoustic resonance issue. This way, an IBC can be advantageous for supplying such lamps, particularly in high power levels where efficiency and volume become more critical parameters. The goal of this paper is a proposal of an electronic ballast based on a two-cell IBC for high-power HID lamps, with current control loop, voltage sensing, and constant power. A dc model based on averaged state-space technique is obtained for the ballast, as well as an ac model based on small-signal disturbances. A complete concept with a digitally implemented closed loop has been developed and a prototype has been built, successfully achieving performance targets. This paper describes the most relevant aspects of the complete design and presents results both experimental and from simulation in MATLAB/Simulink software.