||Based on the concept of partial power regulation, power source conversion circuits can be designed to process a fractional power to outputs for voltage or current adaptation. The partial power regulator (PPR) for processing a part of the supplied power can be connected in series or in parallel with the main power source. A series-connected PPR serves as a voltage regulator, which can be either the same or reverse polarity with the main voltage source to provide a step-up or step-down voltage at output terminal. On the other hand, a current regulator as the parallel-connected PPR can add or detract a current to adapt a higher or lower current. A power source conversion circuit with a PPR for processing only a small part of the input power, delivers the most power directly to the load, and thus can have a high overall power conversion efficiency.|
Two power source conversion circuits with series-connected PPRs are derived for driving LED lamps. Both step-up and step-down voltage regulations are realized by flyback converters. A driver circuit with three PPRs is designed for a white light lamp with three red-green-blue (RGB) LED strings. By multi-phase pulse-width modulation (PWM), LED currents can be controlled precisely and independently. Another LED driver with a series-connected PPR for step-down voltage regulation is accomplished by single active power switch with double-frequency PWM.
In a solar power system, a circuit structure with the parallel-connected PPRs is implemented for utilizing the maximum power from the photovoltaic (PV) panels connected in series. By operating all PV panels at their maximum power points (MPPs) even under partial shaded conditions with unequally illumination, the attached bi-directional flyback converters add a current into or detract a current from the generated MPP currents forming an identical series current. By delicately selecting an adequate series current, the power conversion losses can be minimized. As a result, the maximum generated power from series PV panels can be obtained.
The experimental results carried out on laboratory circuits have demonstrated that the overall power conversion efficiencies of the power source conversion circuits with PPRs are much higher than those of the conventional ones. In addition, the power source conversion circuits with PPRs are advantageous of smaller voltage and current stresses on circuit components, leading to products of smaller size, lighter weight and lower cost.