Wayside LED signal for railroad and transit applications
First Claim
1. A system for controlling power to light emitting diodes in signaling apparatus, said system comprising:
- a plurality of light emitting diodes;
a plurality of current sources for supplying current to each of said light emitting diodes with a separate current source associated with each of said plurality of light emitting diodes;
a data processor with a bus for receiving and sending data, said data processor in communication with said current sources for controlling the amount of current supplied by each current source;
a plurality of resistors in series between the plurality of current sources and the plurality of light emitting diodes; and
a first analog-to-digital converter for determining the voltage potential at each of said plurality of resistors and for providing a digital representation of each determined voltage potential to said data processor;
said data processor using the digital representations of each determined voltage potential to control the amount of current supplied by each current source to its associated light emitting diode.
1 Assignment
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Accused Products
Abstract
A LED signal lamp that monitors, controls and tests the operational status of a plurality of LEDs. A separate current source is provided for each LED and resistors are in series between the current sources and LEDs. Analog-to-digital converters monitor the voltages at the resistors and LEDs and convert the voltages to digital form for a data processor. The data processor determines the junction temperature of each LED, controls the amount of current supplied to each LED and tests the operational status of each LED by matching its characteristics to a known diode curve. A pulse-width modulator provides further control of the amount of power supplied to the current sources. The data processor further controls a vital disconnect and a vital load. An energy storage/limiter circuit stores energy for the data processor during the absence of normal power input. Related methods of monitoring, controlling and testing such an LED system are also disclosed.
40 Citations
24 Claims
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1. A system for controlling power to light emitting diodes in signaling apparatus, said system comprising:
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a plurality of light emitting diodes;
a plurality of current sources for supplying current to each of said light emitting diodes with a separate current source associated with each of said plurality of light emitting diodes;
a data processor with a bus for receiving and sending data, said data processor in communication with said current sources for controlling the amount of current supplied by each current source;
a plurality of resistors in series between the plurality of current sources and the plurality of light emitting diodes; and
a first analog-to-digital converter for determining the voltage potential at each of said plurality of resistors and for providing a digital representation of each determined voltage potential to said data processor;
said data processor using the digital representations of each determined voltage potential to control the amount of current supplied by each current source to its associated light emitting diode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for controlling power to light emitting diodes in signaling apparatus, said signaling apparatus including a plurality of light emitting diodes, a plurality of current sources, a separate current source associated with each of said plurality of light emitting diodes, a plurality of resistors in series between the plurality of current sources and the plurality of light emitting diodes, said method comprising the steps of:
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supplying current to the plurality of light emitting diodes with the plurality of current sources;
controlling the amount of current supplied to each light emitting diode by each current source;
determining the voltage potential at each of said resistors;
providing a digital representation of the voltage potential at each of said resistors; and
using the digital representations of each determined voltage potential to control the amount of current supplied by each current source to its associated light emitting diode. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification