Analysis of a high-bandwidth event-based digital controller for DC-DC converters

This paper analyzes a non-conventional, high-bandwidth digital PID control for DC-DC converters based on an event-driven technique. The controller under consideration employs an asynchronous analog-to-digital converter which updates its output word as soon as the input analog signal crosses a quantization level. A control logic based on a proportional-integral-derivative (PID) structure then updates the converter duty ratio, thus performing the control action on an event-based cycle rather than on a fixed-sampling frequency basis. This paper shows and analyzes how this approach drastically reduces the time delay between the sampling event and the switching event, gaining a main advantage over conventional digital control techniques in terms of both achievable closed-loop bandwidth and reaction time against abrupt load current or input voltage variations. The event-driven PID was VHDL-coded and tested on a FPGA-controlled synchronous buck converter prototype. Comparison with a conventional PID control confirms the effectiveness of the approach.