Abstract: An energy efficient uninterruptible regulated power supply includes a full wave rectifier that is responsive to AC main power generating an unregulated DC voltage signal, a power factor correcting boost converter coupled to receive and selectively increase the unregulated voltage signal to generate a boosted voltage signal, a battery and a single ended forward converter having a primary winding coupled to receive pulse width modulated energy from the boosted voltage signal and a secondary winding couple bidirectionally to the battery with pulse width modulated control. A first controller pulse width modulates the boosted voltage and battery signals coupled to the primary and secondary windings, respectively, to regulate the output voltage while a second controller operates independently of the first controller pulse width modulate the boost converter to regulate the voltage of a transformer secondary signal that is coupled to the battery.