Current-sensing technique for current-mode DC-DC buck converter with offset-voltage compensation

As the technology of SoC (system-on-chip) implementation has been improved, power management IC such as DC-DC converters should be also integrated into a single chip. The current-mode control DC-DC converter is preferred to the voltage-mode one because of simpler frequency compensation scheme, which makes it possible to utilize the chip with less off chip components. In order to achieve an efficient current-mode control, an elaborate current sensing technique should be incorporated to maintain conversion efficiency. In this paper, a new current sensing circuitry is proposed that compensates the offset voltage of the operational amplifier that is used in current-mirroring sensing scheme. The chip is implemented in a 0.35-mum CMOS technology.