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US 4,045,683 AGranted
Drive circuit with constant current
AssigneeLitton Systems, Inc.
InventorFred William Erickson
Life of this patent
Estimating the term…
Abstract
A constant current drive circuit that can be driven directly from the output of a shift register which can find use, for example, in maintaining a constant current through a controlled device such as one or more light emitting diodes (LEDs) to ensure uniform brightness throughout a display surface that includes a plurality of LEDs.
Claims12
A constant current drive circuit comprising:
- a. first and second source means of electrical potential, said first and second electrical potentials being selectively determinable,
- b. current clamping means electrically connected between said first and second source means of electrical potential drawing a determinable constant current, said current clamping means includes
- 1. bistable control means responsive to said first and second electrical potentials and establishing an electrical current therethrough,
- 2. a resistor, and
- 3. a selectively variable third source of electrical potential,
- 4. said resistor and third source of electrical potential connected in electrical parallel and responsive to said current established by said bistable control means to clamp the electrical level or value of said established current,
- c. a controlled device electrically connected between said current clamping means and a selected one of said first and second source means of electrical potential drawing said determinable constant current, and
- d. signal generating means selectively enabling and disabling said current clamping means so that the constant current drive circuit is selectively enabled and disabled.
5 more elements
Dependencies are inferred from the claim text.