1 New Times are Coming – Digitally Operated Primary Control Technology for AC/DC SMPS Abstract This paper describes a whole new control technique and had been successfully being employed in off-line type adapter/charger applications, which results in significant reduction to external components and various performance improvements. Introdu ction A new digital control methodology has resulted in greater simplicity and design flexibility in low power SMPS topologies which conventional analog methods would find difficult if not impossible to achieve. By combining this new control scheme into an off-line type of adapter or charger application, it could greatly reduce the number of external components as well as enhance supply performance in many respects. The controller has built-in digital control algorithms to quickly and smoothly transition between different operating modes for reduced switching losses during no-load operation. The full-load efficiency is enhanced by the use of so-called “emulated primary current mode control” to eliminate the need for a primary sensing resistor. The full-load efficiency is also enhanced in cellular charger applications by the elimination of secondary-side constant current sense circuitry. Its unique digital control algorithm allows fast pulse-by-pulse analysis of the switching waveform and provides accurate voltage & constant-current regulation from the primary-side without the need for an opto-coupler, secondary feedback and reference circuits required by traditional analog solutions. This innovative technology is ideal for balancing new regulatory requirements for green-mode operation with more practical design considerations such as lowest possible cost, smallest size and highest effic...
