Browse Prior Art Database

High Current Optical Driver Circuit

IP.com Disclosure Number: IPCOM000049935D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Haas, LC: AUTHOR [+2]

Abstract

This article describes a high-current driver circuit for a light emitting diode (LED). Transformer windings are employed to provide the high current LED drive pulses while minimizing disturbances within the power supply circuits.

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High Current Optical Driver Circuit

This article describes a high-current driver circuit for a light emitting diode (LED). Transformer windings are employed to provide the high current LED drive pulses while minimizing disturbances within the power supply circuits.

Referring to Fig. 1, a coded data signal SIG is applied both to a D-type latch 10 and to an exclusive-OR circuit 12. The latch 10 introduces a delayed SIG to a second input to the exclusive-OR circuit 12. Circuit 12 applies trigger pulses to a single-shot circuit 14 which controls a first drive circuit 16 with its normal or SQ output and a second drive circuit 18 with its inverted or SQ output. The output of drive circuit 16 is connected to a primary winding 20 of a transformer having a secondary winding 22. A LED 24 is connected between the junction of the windings 20 and 22 and the drive circuit 18. A power supply 26 provides current through a resistor 28.

When SQ is low, drive circuit 16 establishes a current path to ground for a current IP flowing through the primary winding 20. During this time, drive circuit 18 is "off", preventing conduction through LED 24. When SQ rises, drive circuit 18 turns "on" to provide a current path to ground while drive circuit 16 turns "off". Energy which has been stored in the winding 20 contributes to a high current ID through the LED 24 which acts as a damper diode to prevent a high voltage surge. During this time, the power supply 26 also contributes to the curren...