Closed-loop cold cathode current regulator
Palmer, W. D., & Temple, D. (2002). IPC No. U.S.Closed-loop cold cathode current regulator (Patent No. 6492781.)
A current regulator controls the electron emission from a cold cathode using closed-loop feedback from a current sensor in the cathode connection. The regulator circuit includes a cold cathode, a current-sensing element, a current-limiting element, and current-control element. Additionally, the closed-loop current regulator may comprise a reference element for generating the reference level, a circuit power supply and a cathode bias supply. The regulator and cathode may be assembled from separate components, or the entire circuit may be integrated onto a single substrate. In one embodiment, the current level is set by adjusting the reference element directly. In a second embodiment, the current level is set by adjusting the circuit power supply, so that the current level can be set remotely without the need to adjust the reference element directly. The second embodiment is preferably suited for the regulation of beam current in analytical instrumentation. In a third embodiment, the fixed reference element is replaced with a time-varying voltage signal. The current from the cathode then becomes a linear function of the time-varying reference signal. The third embodiment is preferably suited for application as an amplifying element or as the electron source in an emissive display.