Digital controller design for electronic ballasts with phase control

This work presents an approach for digital controller design and implementation in resonant inverters and electronic ballasts. The controller is designed around an inner phase loop for fast regulation of the resonant tank operating point and an outer current loop to control the output load current. The concept of direct digital phase control is reviewed, followed by a description of a complete dual-loop digital controller design. The controller is applied to an HID ballast control system with additional functions including lamp startup and output overvoltage protection. The digital system is described with Verilog coding and can be synthesized and implemented automatically in standard digital logic. An FPGA-based test bed for the digital controller is implemented for rapid prototyping, reprogrammability, and realistic hardware realization.