SMPS Start-Up Circuit
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Switch mode power supplies (SMPS) require a method of providing power to the control and drive circuits operating the high voltage switching element. This disclosure describes a low power circuit capable of starting an SMPS control and base drive circuit. The circuit described initially charges a large capacity from a bus voltage to feed a control IC which powers a base drive circuit. Then a special winding on the lower supply transformer takes over to complete start-up of the power supply. This circuit ensures that even if the supply does not start for some reason (such as an over-current condition), the action of the higher power base drive circuit does not cause the supply to the control IC to drop to the level at which it might malfunction, or reset itself.