Mixed DCM/CCM pulse adjustment with constant power loads

Efficiency, fuel economy, federal mandates, and global socio-political scenarios are the issues that are forcing the vehicular industry to seek more electrification. As land, sea/undersea, air, and space vehicles become more electric and less mechanical, vehicular industry is emerging as a leading application area for power electronics. Electrical architectures of power electronic based vehicular systems are in the form of multi-converter configurations. In multi-converter vehicular systems power electronic converters are mostly utilized in generating, distributing, and utilizing electrical energy in the vehicle. Power electronic converters, when tightly regulated, act as constant power loads. Constant power loads have a destabilizing effect on multi-converter systems. In order to mitigate this instability problem, which is also known as negative impedance instability, this paper introduces pulse adjustment, a novel digital control technique, to control DC/DC converters. This method applies predefined duty cycles, instead of conventional pulsewidth modulation (PWM) techniques, to regulate the output voltage. It is simple, cost-effective, and needs few logic gates and comparators to implement, thus, making it extremely simple and easy to develop using a low-cost application-specific integrated circuit (ASIC). Experimental results as well as simulation results are presented to describe and verify the proposed technique.