Wide Conversion Range Of Step-up Dc - Dc Converter Design,

With continuous demands on energy saving and environment protection, solid-state lighting replaces conventional mercury based lamps gradually. As high drive voltage and large drive current are demanded in solid-state lighting, boost converters with high efficiency and high integration are important to the development of solid-state lighting. So the researches on the boost converters become an international hot topic.This thesis begins with the introduction of the basic DC-DC converter, then some control methods and control techniques. Boost converters have two conjugate poles and one right half plane zero in their power stage, which makes their design more difficult than buck converters. Moreover, the poles and zero vary with the conversion ratio, so it is difficult to design a fixed on-chip compensator to stabilize the system with a wide conversion range. A new system structure with theory analysis in detail is designed to overcome this difficulty. Adaptive current sensing technique is proposed to achieve wide conversion range without external compensation, and compared to the conventional PI compensator, the PI compensator designed in this thesis also has the merits of fast response and area saving. Furthermore, constant off-time control is employed to achieve fast transient response, while its switching frequency variation in different conditions is compensated by the proposed off-time generator.The converter was fabricated in CSMC 0.5μm 40V CMOS process. Measurement results demonstrate that a conversion range of 5V input to 5.5-36V output and switching frequency variation of 1% can be obtained. The overshoot or undershoot is about only 0.5% of its output voltage with a load current step of 200mA.