SMC-PDIC Based Negative Step-Up Converter in DCM for EV LED Headlamps

This paper presents a Sliding Mode ControllerProportional Double Integral Controller (SMC–PDIC) for a Negative Output Step-Up Converter (NOSUC) operating in Discontinuous Conduction Mode (DCM). The NOSUC offers a high voltage conversion ratio, improved power density and reduced current and voltage ripples in the energy-storage components compared with conventional DC–DC converter configurations. However, when operated in Continuous Conduction Mode (CCM), the presence of a Right-Half-Plane Zero (RHPZ) imposes a fundamental limitation on the dynamic response and complicates controller design. To overcome this limitation, the NOSUC is operated in DCM, where RHPZ is eliminated and improved transient characteristics can be obtained. Two control strategies, namely SMC–PDIC and SMC–Fuzzy Logic Controller (SMC–FLC), are developed for the DCM-operated NOSUC and their performances are compared with the conventional SMC–PI control. In the designed control architecture, the PDIC and FLC regulate the output voltage through the outer control loop, while the SMC is employed in the inner current control loop to regulate the inductor current. A State-Space Averaging Model (SSAM) of NOSUC is established to determine dynamic characteristics and obtain the parameters required for controller design. The FLC is developed using control rules derived from the operating behaviour of the converter. The performance of the control structures has been investigated based on MATLAB/Simulink simulation results and laboratory prototype test results. It has been observed from the results that there is an improvement in both transient response and regulation of the designed control schemes in comparison with the existing SMC-PI control. The SMC-PDIC control structure uses an analog control approach, which makes the proposed approach more appropriate for power conversion application with low power requirement. In addition, in the case where DCM operation NOSUC is used for driving LED string for EV headlamps application, the experimental efficiency is 94.7%.