Single-Cycle Over-Current Shutdown
Original Publication Date: 1985-May-01
Included in the Prior Art Database: 2005-Feb-19
In modulated power supply technology, current limiting usually consists of comparing a voltage, proportional to the power transistor current, to a reference. If this reference is exceeded, the error amplifier's output is shorted to ground. This article describes the use of a shut-down latch that terminates conduction when an over-current exists, but is cleared between conduction periods to allow continued power supply operation. A portion of the control circuitry of a typical high-speed switching regulator is shown in the drawing. The dotted-box portion shows where the shut-down latch 1 is inserted. The latch is set when an over-current is sensed at 2 and turns off the power transistors 3. The latch 1 further prevents a restart from occurring during the same clock period.