Pseudo-Ramp Current Balance (PRCB) Technique With Offset Cancellation Control (OCC) in Dual-Phase DC-DC Buck Converter

To cope with monolithic controller replicas and the current unbalance situation in multiphase converters, a pseudo-ramp current balance technique is proposed to achieve time-multiplexing current balance in voltage-mode multiphase DC-DC buck converter. With only one modulation controller, silicon area and power consumption caused by the replicas of controller can be reduced significantly. Current balance accuracy can be further enhanced since the mismatches between different controllers caused by process, voltage, and temperature variations are removed. Moreover, the offset cancellation control embedded in the current matching unit is used to eliminate intrinsic offset voltage existing at the operational transconductance amplifier for improved current balance. An explicit model, which contains both voltage and current balance loops with non-ideal effects, is derived for analyzing system stability. Experimental results show that current difference between each phase can be decreased by over 83% under both heavy and light load conditions.