NOVEL APPROACH FOR GENERATION OF POWER FAILURE WARNING SIGNAL TO MAXIMIZE USEABLE HOLD-UP TIME WITH AC/DC RECTIFIERS

摘要

A method of optimally generating a power failure warning (PFW) signal has been disclosed here in such a manner that adjusts timing of PFW signal generation according to load conditions in case of input AC voltage loss. A PFW voltage threshold value can be set at a lower value under light load conditions and at a higher value under heavy load conditions. PFW signal generation can also be triggered by a timing mechanism that is set when a bus voltage drops to a voltage threshold value. A countdown time of the timing mechanism is set according to a determined bus voltage drop rate. In this manner, issuance of the PFW signal is delayed for lighter load conditions and the power supply unit is capable of extending normal operation under lighter load conditions before the PFW signal is issued.

主权项

1. A method of generating a power failure warning signal, the method comprises:
a. monitoring a bus voltage of a power supply unit; b. adjusting a power failure warning voltage threshold value according to a varying load condition of a load coupled to an output of the power supply unit; and c. generating the power failure warning signal when the bus voltage drops to the power failure warning voltage threshold value.