Delta-Sigma Modulator-Based Step-Up DC–DC Converter with Dynamic Output Voltage Scaling

Abstract

The switching noise and conversion efficiency of step-up DC-DC converters need to be improved to meet increasing demand. The delta-sigma modulation (DSM) technique is typically used to improve the performance of buck converters; however, this control scheme is not directly applicable for boost converters. This paper presents a boost DC–DC converter using a continuous-time delta-sigma modulator (DSM) controller for battery-powered and noise-sensitive applications. The proposed converter can adjust a wide range of output voltages dynamically by clamping the maximum duty cycle of the DSM, thus enabling stable and robust transient responses of the converter. The switching harmonics in the converter output are reduced effectively by the noise shaping property of the modulator. Moreover, the converter does not suffer from instability of mode switching due to the use of a fixed third-order DSM. Fabricated in a 180 nm CMOS, the converter occupies an active area of 0.76 mm2. It produced an output voltage ranging from 2.5 V to 5.0 V at an input voltage of 2.0 V and achieved a peak conversion efficiency of 95.5%. The output voltage ripples were maintained under 25 mV for all load conditions. A low noise output spectrum with a first spurious peak located −91 dBc from the signal was achieved.