Digital combination of DC/DC converters: A novel theory applied to positive buck-boost converters.

摘要

Portable applications such as digital cameras, cell phones, PDAs, and camcorders need a steady voltage from a single-cell or multi-cell Li-ion, NiMH, or NiCd batteries. With the increasing use of low-voltage portable devices and increasing requirements of functionalities embedded into such devices, efficient power management techniques are needed for longer battery life.; Since the voltage profile of each kind of batteries change, when it is fully charged to the discharged condition, in order to get a steady output voltage in the middle range of the input supply, both the step-down and step-up operations are necessary. The prime decisive factors while making a choice for converters or regulators in portable electronic applications are voltage regulation, efficiency, cost, and size.; A major concern in portable electronic applications is the input voltage to the devices supplied by batteries, becoming equal to the output voltage, when the maximum output voltage transients arise causing the voltage regulation at the output of the converter poor, which finally affects the life of the battery. One of the best approaches to this problem is the use of a single converter named positive buck-boost converter (PBB), which can be made to work in both step-up and step-down modes of operation by digitally changing the switching circuit.; The novel theory proposed in this Ph.D. dissertation is the combination of different converter modes, without changing the hardware of the converter, implemented by digital control logics to improve the transients arising in the output voltage of the converter, thereby, improving the voltage regulation. In addition, aspect of efficiency improvement and optimized switch performance can be achieved by properly choosing the converter modes, which would optimize the switching scheme and, thereby will, reduce the losses.; Simulation results are shown for the proposed novel theory applied to PBB. In the next step, experimental verification of the novel theory is made using dSPACE based implementation of the control algorithm. An extensive comparative analysis based on simulation and experimental results among the proposed novel theory with other topologies and control schemes are presented in this dissertation as well.