Embedded frequency response measurement capability for monitoring and tuning of system dynamics in digitally-controlled DC-DC converters.

摘要

This thesis demonstrates the feasibility of integrating nonparametric frequency-domain system identification functionality into digital controllers for switched-mode pulse-width modulated (PWM) DC-DC power converters. The resulting discrete-time frequency response can be used for design, diagnostic or auto-tuning purposes. The success of these applications depends on the fidelity of the identified frequency responses and the degree to which the process is automated, as well as the costs, in terms of hardware resources, time duration of identification, and effects on output voltage, incurred to obtain these benefits. It is shown that relatively accurate and smooth frequency response data can be obtained using a Verilog-coded implementation with low tens of thousands of logic gates and about 10 kB of memory. The identification process can be accomplished in several hundred milliseconds and the output voltage can be kept within specified bounds during the entire process. The impact of this work is demonstrated with an integrated auto-tuning example wherein the controller determines PID controller parameters required to maximize the closed-loop bandwidth of the feedback control system while maintaining user-specified stability margins and integral-based no limit-cycling criteria as well as ensuring single crossover frequency operation and sufficiently high loop gain magnitude at low frequencies. The approach is completely automated and can be applied to a wide range of PWM DC-DC converter architectures with no changes to the identification or auto-tuning algorithms. In order to demonstrate this versatility, identification and auto-tuning experimental results are presented for seven different PWM DC-DC converters operating in voltage-mode control. These include a well-damped synchronous buck, a lightly damped synchronous buck with and without a poorly damped input filter, three different boosts operating in continuous conduction mode with varying capacitor size and non-minimum phase zero frequency, and a boost operating in discontinuous conduction mode.