Patent ID: 6559711
Filing Date: 2003-05-06
Classification: G05F

Abstract:
A circuit for providing a constant current (I0), comprising:means (10, 11) for generating a first (I1,a) and a second (I1,b) of two substantially identical currents from a voltage source, means (12) for supplying a differential current which is the difference between said two substantially identical currents (I1,a, I1,b) to a first capacitor (13), means (20,21,27,28) for supplying a variable charging current (I2) to at least one second capacitor (22,29) from the voltage source, means (14, 15, 16, 17, 23, 24, 30, 31) for periodically discharging and subsequently charging again the first (13) and the at least one second (22,29) capacitor, means (25, 26, 32, 35, 38, 39,40,44; 44,46,47) for controlling a time period between two periodic discharges using a clock signal, wherein the time period is a measure for the difference in voltage across the first and the at least one second capacitor, means (41,42; 36,37) for generating a setting signal for setting both the variable charging current (I2) and at least one of the two substantially identical currents (I1,a, I1,b) in dependence of said time period, and means (19,18) for controlling an output element (43,43â€²) with a same signal as the setting signal, wherein the output element generates a constant current source from one of the two substantially identical currents.