Patent ID: 6057607
Filing Date: 2000-05-02
Classification: H02M

Abstract:
A step-down switched-mode power supply circuit, comprising:a transformer having at least one primary winding and at least one secondary winding;a current sensing device for sensing a current through a primary winding of the transformer;a first switch and a second switch;a first comparator for determining if the current through said current sensing device exceeds a threshold;a voltage regulator coupled to the secondary winding to produce a regulated voltage on an output line;a second comparator coupled to said output line of said voltage regulator for determining if the regulated voltage has drooped below an acceptable level;a counter coupled to the second comparator for asserting a power save disable signal for a fixed number of switch cycles when said second comparator determines that the regulated voltage has drooped below said acceptable level; andcontrol circuitry for generating a pair of complimentary signals controlling the first switch and the second switch, said control circuitry responsive to the first comparator to enter a power saving mode disabling the complimentary signals, and to the power save disable signal to temporarily exit the power saving mode while the power save disable signal is asserted.