Development of on-chip current mode synchronous step-up converter without external compensating network and slope compensation

Abstract

A monolithic current mode CMOS DC-DC converter with new control topology and integrated power switches has been developed in this thesis. A unified modulator model is also established for the topology, following the steps, used for deriving familiar models. System and circuit level implementation of the converter have been accomplished for the converter. Afterwards, this converter has been fabricated with a standard 0.5 flm CMOS process. The remarkable features of the converter are complete discharge of the output voltage, pulse-by-pulse current limiting, pulse-skipping mode in light load operation etc. Modulator gain Fm has been found to be a finite quantity and is independent of duty cycle, which reveals the fact that the control loop's stability is independent of compensating signal. In addition, no external components except the inductor and output capacitor and no extra I/O pins are needed for the current mode controller. The simulation and test data are in good agreement. The experiment results show that this converter operates around IMHz with the supply voltage from 0.8V to SV, which is suitable for single cell lithium-ion applications. The power efficiency is over 80% for load current from SOmA to 100mA, load regulation 1.6%, for the load variation 0-1OOmA.