Power supply for light emitting diode roadway lighting fixture
First Claim
1. A method of controlling a power supply for light emitting diode (LED) module in a roadway fixture, the method comprising:
- performing electro-magnetic interference (EMI) filtering of an incoming alternating current (AC) current;
performing AC to direct current (DC) rectification of the AC current;
stepping down the rectified DC current based upon a power correction factor (PFC) value;
providing the stepped down DC current to the LED module;
measuring a current through the LED module;
determining the PFC value based upon at least the measured current through the LED module;
feeding-back the determined PFC value to control the stepped down DC current; and
determining a turn-on cycle used in determining an age of the LED module for a ramp-over-time current mode to provide an increasing current to the LED module to maintain illumination output over time by adjusting the PFC value.
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Accused Products
Abstract
A high efficiency light emitting diode power supply for roadway lighting fixtures is provided. The power supply enables conditioning and monitoring of input power and monitors LEDs current to ensures consistent performance of the LED by changing a power correction factor. The LED output can also be adjusted based upon age or external input parameters and by modifying the power correction factor value. In addition, the LED output can be dimmed, turned down in output to a lower level at any time of night for a prescribed duration in order to further save energy. This dimming function uses a programming scheme that keeps track of the “seasons” (summer, fall, winter and spring) so that time of night is tracked accurately all year long.
26 Citations
22 Claims
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1. A method of controlling a power supply for light emitting diode (LED) module in a roadway fixture, the method comprising:
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performing electro-magnetic interference (EMI) filtering of an incoming alternating current (AC) current; performing AC to direct current (DC) rectification of the AC current; stepping down the rectified DC current based upon a power correction factor (PFC) value; providing the stepped down DC current to the LED module; measuring a current through the LED module; determining the PFC value based upon at least the measured current through the LED module; feeding-back the determined PFC value to control the stepped down DC current; and determining a turn-on cycle used in determining an age of the LED module for a ramp-over-time current mode to provide an increasing current to the LED module to maintain illumination output over time by adjusting the PFC value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of controlling a power supply for light emitting diode (LED) module in a roadway fixture, the method comprising:
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performing electro-magnetic interference (EMI) filtering of an incoming alternating current (AC) current; performing AC to direct current (DC) rectification of the AC current; stepping down the rectified DC current based upon a power correction factor (PFC) value; providing the stepped down DC current to the LED module; measuring a current through the LED module; determining the PFC value based upon at least the measured current through the LED module; and feeding-back the determined PFC value to control the stepped down DC current; wherein the PFC value is further based upon a dimming sequence retrieved from a dimming schedule defining a desired light output level of the LED module over a length of a night period wherein the dimming schedule is determined by; determining the length of the night period from a sunset time and a sunrise time determined from a light sensor; storing the determined length of the night period in memory; determining if a required plurality of lengths of consecutive night periods have been stored; averaging the required plurality of lengths of consecutive night periods; and performing a lookup in a dimming schedule based upon the average length of the night period to determine the dimming sequence associated with the length of the night period. - View Dependent Claims (9, 10, 11)
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12. A power supply for use with a light emitting diode (LED) module in a roadway lighting fixture, the power supply comprising:
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an electro-magnetic interference filter for filtering an alternating current (AC) current; an AC rectifier for rectifying the AC current to a direct current (DC) current; a power factor correction (PFC) circuit maintaining the DC current waveform in phase with line voltages by switching a transformer based upon a received PFC value; a secondary side filtering module for reducing voltage and current ripple in the DC current; an LED current sensor module for detecting a current value used by the LED module in a return line from the LED module; and a micro-controller for monitoring the LED current and processing input to determine the PFC value to be applied to the transformer based upon the detected LED current value; wherein the micro-controller utilizes high ripple voltages representing a proportional current and is averaged and compared to a set value programmed in the micro-controller memory to determine the PFC value. - View Dependent Claims (13, 14, 15)
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16. A power supply for use with a light emitting diode (LED) module in a roadway lighting fixture, the power supply comprising:
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an electro-magnetic interference filter for filtering an alternating current (AC) current; an AC rectifier for rectifying the AC current to a direct current (DC) current; a power factor correction (PFC) circuit maintaining the DC current waveform in phase with line voltages by switching a transformer based upon a received PFC value; a secondary side filtering module for reducing voltage and current ripple in the DC current; an LED current sensor module for detecting a current value used by the LED module in a return line from the LED module; and a micro-controller for monitoring the LED current and processing input to determine the PFC value to be applied to the transformer based upon the detected LED current value; wherein the micro-controller receives input from a light output sensor to be used in determining the PFC value and further comprises a memory for storing a dimming schedule table comprising a plurality of dimming sequences each based upon a length of the average night period, the dimming sequences defining one or more associated PFC values to be applied over an illumination period. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification