CURRENT REGULATOR FOR ELECTRON MICROSCOPE POWER SUPPLY

摘要

ADJUSTABLE SWITCHING CURRENT REGULATOR of the Invention The present invention relates to a high efficiency current regulator control circuit used to adjust and accurately control current flow in a substantially resistive load such as the low resistance filament in an electron gun of an electron microscope. The efficiency is obtained by running a solid state device such as a transistor in a switching mode. The present circuit represents an advantage over previous circuits which utilized a series or shunt pass regulator which dissipates power in performing the regulation function. The present circuit utilizes a switching mode regulator which regulates by switching a fast transistor either full "on" or full "off" in response to current flow through a sensing resistor. The ratio of "on" to "off" time determines the current transfer. It is a requirement of the circuit that the sensing resistor be of a material having an extremely low temperature coefficient such that the current flow through the resistive element and the resulting inherent heating of the element do not substantially affect its resistive characteristics.