Asynchronous Switched-Mode Power Supply Start Up for Display Monitor
Original Publication Date: 1988-Aug-01
Included in the Prior Art Database: 2005-Feb-15
An overcurrent protection circuit in a switched-mode power supply (SMPS) for a display monitor is inserted to prevent a temporary fault causing a catastrophic failure of the switching device. The setting of the trip level is a matter of compromise between adequate protection at high ambient temperatures, when transformer core saturation lowers the failure threshold, and the need for a quick but smooth start-up over a wide range of input voltages. The current surge that occurs on start-up can lead to spurious tripping of overcurrent protection circuits. Existing solutions rely on a carefully balanced compromise between a slow start-up and adequate protection, but their performance is often marginal when all combinations of input voltage and ambient temperature are accounted for. The circuit shown in Fig.