Designing an Accurate and Robust LC-Compliant Asynchronous ΣΔ Boost DC-DC Converter

Portable electronic devices not only require switching DC-DC converters to be compact and integrated but also compliant to wide off-chip LC filter variations, which are subject to manufacturing tolerances, temporal and thermal parameter drifts, and more often than not, application-driven constraints. While optimal LC compliance has been demonstrated in ΣΔ buck converters, little has been done in boosting applications. This paper presents an asynchronous ΣΔ boost converter and describes how LC variations affect stability, steady-state error, and switching frequency, and how a frequency-dependent gain mitigates these effects. Simulations show the circuit is stable for 1-30μH inductances and 15-350μF output capacitances, its steady-state error is less than 1%, and its switching frequency varies 15% less (over load and line variations) than in conventional ΣΔ converters.