A Dynamic Voltage Scaling Controller for Maximum Energy Saving Across Full Range of Load Conditions

For devices operating mainly in the standby or low power mode, energy saving from dynamic voltage scaling (DVS) is limited due to very poor efficiency of the PWM DC/DC converter operating at light load conditions, resulting in shorter than expected battery life. This paper first presents the design of a DVS controller - realized on a Xilinx CoolRunner 2 CPLD - having a 25μs worst case transient response and 15 mV average V
dd
step size across an 1.30-1.90 V range. Next a scheme is proposed in which the DVS controller automatically selects between the PFM and PWM mode DC/DC conversion to realize maximum power saving across full range of load conditions.