Cross-conduction blocked power selection comparison/control circuitry with ntc (negative temperature coefficient) trip voltage

Abstract

Power selection circuitry that may be employed in redundant power supplies. The power selection circuitry includes a comparator, a symmetric resistor array coupled between the comparator inputs and multiple input voltage sources, a plurality of first switching elements, and control logic/drive circuitry coupled between the comparator output and the first switching elements. The first switching elements connect a selected input voltage source to a load. The comparator compares the voltage levels of the respective voltage sources, and provides a voltage indicating which one of the voltage sources is operational to the control logic/drive circuitry, which applies control signals to the first switching elements to connect the operational voltage source to the load. The symmetric resistor array and a plurality of second switching elements assure that symmetric trip voltages with hysteresis are provided to the comparator. The power selection circuitry may be employed in a redundant power supply to block the cross-conduction of current between the multiple input voltage sources, to reduce current spikes during power selection switching, and to satisfy NTC trip voltage requirements of the switching elements connecting the input voltage sources to the load.