Desenvolvimento de uma fonte chaveada para uso em laboratório de graduação

Abstract

This paper presents a switch mode power supply (SMPS) operating in continuous conduction mode (CCM). Mathematical derivations are verified for the small signal models (SSM) of control-to-output and inductor current-to-output PWM-controlled buck converter. Two controllers are designed to achieve either constant voltage (CV) or constant current (CC) modes of operation. The power stage is digitally controlled at a fixed frequency by a digital signal processor (DSP). Voltage and current signals are quantized each cycle and subtracted to the respective reference signals, so that the error signals can be calculated and used to compensate the system. The softwares PSIM® and MATLAB® are used to simulate the SMPS. The power supply implementation is done on a printed circuit board. The practical results shows an intersting behavior about the automatic transition between the two control modes of operation. A simple control design can be applied to the voltage loop, while the fast response at the inner loop provides current limiting. The proposed SMPS major drawback is the requirement of an adaptative positioning voltage, so that the controller could be able to evaluate suitables coefficients for each point-of-load situations. Even so, the mathematical relations established on this work can be applied to the DSP to match the fitting values for the controllers as the point-of-load is modified.