Patent ID: 6404612
Filing Date: 2002-06-11
Classification: H01H,H02M,Y02B

Abstract:
A pulse width modulated solenoid driver with a reduced rate of power consumption comprising:a solenoid; a flow set-point voltage for establishing a desired current flow through said solenoid; a step-down regulator circuit for controlling said actual current flow through said solenoid based on a difference between said desired current and said actual current flow through said solenoid; wherein said step-down regulator comprises an input voltage pin, a feedback voltage pin, a reset pin, a ground pin, and a switching voltage pin; a first supply voltage tied to said input voltage pin of said step-down regulator; a first terminal of said solenoid tied to said switching voltage pin; a second terminal of said solenoid tied in series to a current-sensing resistor which is also tied to a second supply voltage; a cathode of a diode tied to said switching voltage pin; an anode of said diode tied to a third supply voltage; a first amplifier stage for filtering and amplifying a voltage across said current-sensing resistor to generate a voltage analog of said actual current flow through said solenoid; said ground pin of said step-down regulator tied to said third supply voltage, wherein said feedback voltage pin is biased at a step-down regulator operationally determined voltage above said ground pin voltage when said actual current flow through said solenoid matches said desired current flow; and a second amplifier stage for negatively shifting said voltage analog of said actual current flow through said solenoid by a sum of said second supply voltage and said step-down regulator operationally determined voltage to generate a scaled and biased voltage analog of said actual current flow.