Yingying Kuai with adviser Patrick L. Chapman
Integrated circuit (IC) implementation of dc-dc converters is popular in portable electronic systems, as it is the most cost-effective approach to design a complex electronic system. There is a growing application sector within the hand-held electronics market where the dc-dc converter’s load consists of a generic amplifier or a fixed and predictable load, such as an antenna, display/LEDs, a small motor, or a CPU. This project is targeted for low-power applications (up to several watts) to extend battery life. It includes the design and implementation of a dc-dc converter using IC technology and sensorless/predictive digital optimization control, along with a study on integrated hybrid L-C devices.
First, layout issues such as determining the optimal size of power devices and ground isolation are addressed. The MOSFET models for both analog and digital IC design are being investigated to aid in power-loss analysis. Electrical noise presented in a high-frequency switching circuit is a key factor in efficiency reduction. A thorough noise analysis and computation will be performed to further optimize the layout quality of the converter.
Second, novel design and optimization approaches to achieve high-efficiency and high energy density will be explored. Predictive control of power converters is one of the frontiers. For a typical load, its instant power or current can be predicted, then fed forward to the converter. The control scheme then takes advantage of this information to perform online adjustments to the converter, either on the structure or operation. This will help to eliminate excess power loss within the converter and to enhance power conservation of the whole system. Figure 28 shows a generic block diagram of the proposed scheme.
The development of such a system includes two steps. Modeling the load signal using stochastic models, such as Markov chains, could possibly provide fast and accurate prediction. Specific optimization strategies such as segmented MOSFET switching devices and variable frequency control are studied. Third, a novel hybrid integrated L-C device is built and being tested for its possible usage in IC dc-dc converters. Integrating the passives (capacitors and inductors) and combining their features into one multi-resonant device is a big step in converter miniaturization and reliability maximization. The device will be tested on a buck converter to characterize and verify its function. Further improvements may be performed based on the evaluation results.