Adaptive tuning and monitoring of digitally controlled switched mode power supplies

In many power supply applications, tight regulation of the output is often required despite the highly dynamic nature of the loads. Tight regulation is typically achieved by designing a high bandwidth feedback loop capable of rejecting the effects of uncertainty and/or variations in the power stage. However, design of a control loop capable of operating over a wide range of power stage parameters while maintaining excellent dynamic performance is often difficult to achieve with simple, low cost hardware. Therefore, in many applications there is typically a compromise between the control loop robustness vs. the achievable dynamic performance.;This thesis presents an approach to continuous adaptive tuning and monitoring of switched mode power supply feedback loops. The monitoring system uses information already available inside a digital controller to detect changes in both converter efficiency and frequency response. The information can be used to deduce changes in the health of the electrical components within the power supply before catastrophic system failure.;An approach to adaptive tuning is also presented capable of maintaining dynamic performance specifications despite wide variations and/or uncertainties in power stage parameters. The adaptive tuner is designed to continuously adjust the parameters of a digital compensator such that desired crossover frequency and phase margin are maintained. Models for the adaptive tuning system are derived and a simple design procedure is presented. The core adaptive tuning system is experimentally demonstrated using a synchronous buck converter test-bed.;Additional complications arise when applying the core adaptive tuning system to non-minimum phase (NMP) converters. In general, the achievable bandwidth of NMP converters is dependent on the load and further becomes time varying with a time varying load. Since the load is often considered an unknown, the choice of a desired crossover frequency for the adaptive tuning system can be difficult. In this context, a modified algorithm is presented which automatically determines the desired crossover frequency by using the compensator zero locations as a measure of the tuning effort. The proposed approach is experimentally verified using two different boost power stages.;The adaptive tuning algorithm can be further extended to account for abrupt large-signal variations in plant dynamics, such as continuous-conduction mode (CCM) to discontinuous-conduction mode (DCM) transients caused by changes in the load. Using a simple CCM/DCM sensor, two different sets of compensator parameters are tuned based on the current converter operating mode. Upon load transients, the appropriate set of tuned parameters is then loaded in the output voltage feedback loop compensator. Experimental results are given for a CCM/DCM buck converter.