Control of DC-DC Converters

A constant voltage regulator, to supply constant power loads, is realized using a Switched-capacitor converter. Exhaustive studies have been carried out to find the suitability of available control schemes and finally one control scheme investigated with (i) operation of the converter at different crossover frequencies (ii) operation of the converter at different phase Margins. Various operating modes have been analyzed and then a mathematical model is formulated to carry out the dynamic performance and controller design studies. State-space averaging method is employed in the modeling stage. The switched capacitor converter mathematical analysis, modeling and controller design of the single loop control scheme are presented and closed loop simulation results of the switched capacitor dc-dc converter with this control scheme are obtained through PSIM simulator. In the first stage a simple voltage-mode, single-loop; controller is adopted for load voltage regulation. Four important open-loop system small-signal model transfer functions required for controller design are derived, using these transfer functions together with the K-factor design oriented method the controller is designed to meet the frequency response specifications, gain margin and phase margin, and to ensure stability of the system. Taking this designed controller the closed-loop converter system is simulated in the PSIM power electronics simulator and tested the controller regulation capability against source and load disturbances. To verify the simulation results, experimental investigations have been carried out and the measured results are closely matching with the simulated results