Research On High Integration And Fast Response Buck Converter

With the fast development of electronic technology, switching mode power supply (SMPS) buck converter is more widely used in the palm-sized devices and instruments. High integration is one of the main trends of the future on chip SMPS converters. Thanks to the development of modern semiconductor process, more off-chip components are integrated into the chip for minimizing external pins and making it easy to use. To meet the demands of modern on-chip SMPS, a novel high integration and fast response buck converter was presented in this thesis.Three improvements were made with respect to high integration. Firstly, to avoid the use of big capacitors requested by the conventional soft-start mechanism, a digital controlled soft-start method was adopted which eliminates the external capacitor and additional pin and makes the starting more gently. Secondly, the external power switches and driver were integrated into the chip with the synchronization rectifying technology in this design. And the lossless current detection function was realized by parallel-connection proportional power MOSFET. Most importantly, a capacitor multiplier technique was proposed to implement a buck converter with on-chip compensation network featuring high performance and minimized external pins that are favorable for designers to use.Meanwhile, two improvements were made for voltage mode control to raise the response of converter. Firstly, the feed-forward technique was utilized to make the peak-peak voltage proportional to the input voltage to increase its linear regulation. As to load regulation, the response time of system was adaptively modified for dynamically changing the crossover frequency when load step occurred.According to the design principles mentioned above, several circuits were compared and analyzed. What's more, improvements were made to meet the design specification. The system was simulated and verified in a 1.5um BCD process and the simulation results showed all performances were satisfied with the anticipative goal.