Current monitor for field emission displays

摘要

A current measuring circuit for a field emission display includes a testing circuit coupled between a high voltage testing source and the display. The testing circuit includes a sampling circuit formed from a sampling impedance coupled in parallel with a high isolation switch. In one embodiment, the sample circuit is on the high voltage side of the testing source. In another embodiment, the sampling circuit is on the return (low voltage) side of the testing source. In normal operation, the switch is closed to provide the testing voltage directly to the display. During testing, the switch is open so that current flows through the sampling impedance. A sensing circuit coupled to the output of the sampling impedance determines a voltage change in response to opening of the switch. In response to a sensed voltage change, a microprocessor-based controller computes the current drawn by the display. A burn-in system includes a bank of displays within a burn-in oven each selectively coupleable to the testing circuit by respective switches. Another testing system includes separate supply and testing sources each coupled to displays by respective switches. The switches are opened and closed such that the displays are always coupled to one or both of the voltage sources to prevent the switches from being exposed to high voltage swings.