| Based on the project"Design technique research of mixed-signal IC for single chip"of Key Lab of High-Speed Circuit Design and EMC, Ministry of Education in Xidian University, the paper focus on the design and implement of high voltage synchronous rectified step down DC/DC converter.A peak current mode high voltage synchronous rectified step down DC/DC converter is designed based on in-depth research of Buck DC/DC converter basic principles and loop stability. High voltage switching power MOS and synchronous power MOS are integrated in the chip. The technique of synchronous rectification is used for improving chip efficiency. A novel current limit is presented to eliminate the slope compensation effect on the load ability and make temperature compensation for the current sense structure, so that the load ability is improved significantly. The system has zero inductor current detection and works in continuous conduction mode or discontinuous conduction mode according to the load. The chip will automatically work in pulse skip mode. In the skip periods, most parts of the chip are shut down to decrease the quiescent current for the consideration of efficiency. The chip also integrates some protections including short protection, over temperature protection, under voltage lock out, over voltage protection, soft start, peak inductor current limit and so on.Based on 0.35um 20V BCD process,circuit design and simulation, layout design are accomplished by using the EDA tools of Cadence. 4.8V to 20V input, 2A load, with highest efficiency 93% and layout area 1560um×1620um, the chip has been taped out.
|
PDF Full Text Request