Integration of Frequency Response Measurement Capabilities in Digital Controllers for DC–DC Converters

Abstract

Recent work has shown 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 self-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 gate count, time duration of identification, and effect on output voltage, incurred to obtain these benefits. This paper demonstrates the feasibility of incorporating fully automated frequency response measurement capabilities in digital PWM controllers at relatively low additional cost. In particular, 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. Experimental results are provided for four different PWM dc-dc converters, including a synchronous buck with two different filter capacitors, a boost operating in continuous conduction mode (CCM), and a boost operating in discontinuous conduction mode (DCM).