Abstract
This thesis presents a dc-dc buck converter using hysteresis current control mode. A synthetic ripple voltage is proposed to sense the voltage across the inductor and to generate a saw tooth waveform for hysteresis band control. The proposed sensing circuit acts like a low-pass filter and has a local feedback loop to reduce the switching noise. The switching frequency in different load conditions is fixed because the fixed inductor voltage provide constant rising and falling slope of synthetic ripple. The error of the dc term of DCR multiply iL is compensated by an error amplifier to prevent saturation. Full chip simulation results of different load conditions and plus-minus a 10% error of DCR indicate that the synthetic ripple has accuracy about 99%. The range of the operation voltage of the proposed design is from 2.7 to 4.4V; the output voltage recovery time is 24μs under load current conditions between 100mA and 300mA; the maximum conversion efficiency is 89%; the low noise design is particularly suitable for portable device with a Li-ion battery power supply.