Analysis of high-performance synchronous-asynchronous digital control for dc-dc boost converters

This paper investigates the application of a mixed synchronous/asynchronous digital controller to dc-dc boost converters. The digital control synchronously generates current and voltage ramps by using two low-resolution Digital-to-Analog Converters (DACs). Switch turn-on and turn-off are determined asynchronously by comparing converter state variables and the digitally generated current and voltage ramps. The control features high dynamic performance, frequency modulation during transients, no quantization effects, and low-complexity. In order to evaluate the dynamic performance and to compare the proposed solution with conventional analog peak current-mode control, a small signal model of the synchronous/asynchronous modulation is derived. Even if aimed to an integrated digital controller, experimental investigation has been performed using discrete components, implementing the digital control in a Field Programmable Gate Array (FPGA) using a hardware description language (VHDL). Simulation and experimental results on 100 W dc-dc boost converter confirm the proposed analysis and shows that the proposed solution enables dynamic performance comparable to that of analog peak current-mode control.