Motivated by emerging portable applications that demand ultra-low-powerhardware to maximize battery run-time, high-efficiency low-voltage DC-DC conversionis presented as a key low-power enabler. Recent innovations in low-power digitalCMOS design have assumed that the supply voltage is a free variable and can be set toany arbitrarily low level with little penalty. This thesis introduces and demonstrates anarray of DC-DC converter design techniques which make this assumption more viable.