AC-powered LED light engine
First Claim
1. A driverless LED light engine comprising:
- a first plurality of LED devices connected in series to form a first LED string, with the first LED string defined as including a plurality of LED substrings connected anode to cathode and connected to the ac power line; and
a plurality of dissipative current limiting devices and at least two bias capacitors coupled to selected LED substrings such that during each power line half cycle two distinct types of LED current flows are present, one type of LED current flow associated with displacement current attributed to one of the at least two bias capacitors and one other type of LED current flow associated with galvanic current passing through the dissipative current limiting devices, such that at some points in time during an AC voltage cycle, at least one LED substring receives capacitively-limited current, and at other points in time during said AC voltage cycle said at least one LED substring receives galvanic current, the at least two bias capacitors operating as a pair, each associated with a power line half cycle such that as a first bias capacitor of the at least two bias capacitors is providing capacitively-limited current, a second bias capacitor of the at least two bias capacitors is re-charging from the ac power line.
1 Assignment
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Accused Products
Abstract
AC LED light engines powered directly from the AC power line contain circuitry of resistors, capacitors, diodes and transistors which enables an array of LEDs to efficiently produce light with a relatively low level of flicker as perceived by the human eye. The LEDs are driven by a current which is alternately capacitively limited and resistively-limited. Capacitively-limited pulses of current are combined with resistively-limited pulses of current so that the resulting output current ripple is at frequencies of 240 Hz or above which the human eye cannot perceive. The combination of resistively-limited current and capacitively-limited current results in a current drain from the power line which is generally sinusoidal and can have a power factor in excess of 0.90, and a flicker index below 0.2.
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Citations
20 Claims
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1. A driverless LED light engine comprising:
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a first plurality of LED devices connected in series to form a first LED string, with the first LED string defined as including a plurality of LED substrings connected anode to cathode and connected to the ac power line; and a plurality of dissipative current limiting devices and at least two bias capacitors coupled to selected LED substrings such that during each power line half cycle two distinct types of LED current flows are present, one type of LED current flow associated with displacement current attributed to one of the at least two bias capacitors and one other type of LED current flow associated with galvanic current passing through the dissipative current limiting devices, such that at some points in time during an AC voltage cycle, at least one LED substring receives capacitively-limited current, and at other points in time during said AC voltage cycle said at least one LED substring receives galvanic current, the at least two bias capacitors operating as a pair, each associated with a power line half cycle such that as a first bias capacitor of the at least two bias capacitors is providing capacitively-limited current, a second bias capacitor of the at least two bias capacitors is re-charging from the ac power line. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A driverless light emitting diode (LED) light engine for providing illumination from an AC voltage source, the driverless LED light engine comprising:
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a plurality of LED devices connected in series as a single string of LEDs, defined as comprising a plurality of LED substrings; dissipative current limiting means disposed along a signal path including the AC voltage source and the single string of LEDs; and at least two capacitive means coupled to separate ones of the LED substrings so that at some points in time during an AC voltage cycle, at least one LED substring receives capacitively-limited current, and at other points in time during said AC voltage cycle said at least one LED substring receives current limited by dissipative current limiting means, the at least two capacitive means operating as a pair, each associated with a power line half cycle such that as a first capacitive means of the at least two capacitive means is providing capacitively-limited current, a second capacitive means of the at least two capacitive means is re-charging from the AC voltage source.
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8. A driverless LED light engine having first and second input terminals connected to an AC power source, the LED light engine comprising:
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a plurality of LED devices connected in series as an LED string having a first end termination and a second, opposing end termination, the LED string defined as comprising a plurality of LED substrings with a midpoint of the LED string connected to the first input terminal; a first rectifier diode coupled between the second input terminal of the AC power source and the first end termination of the LED string so as to permit current flow during positive voltage half cycles; a second rectifier coupled between the second input terminal of the AC power source and the second end termination of the LED string so as to permit current flow during negative voltage half cycles; a first bias capacitor connected from a cathode of the first rectifier diode to an intermediate point on the LED string between the midpoint and the second termination so as to be in parallel with a first plurality of LED substrings; and a second bias capacitor connected from an anode of the second rectifier diode to an intermediate point on the LED string between the midpoint and the first termination so as to be in parallel with a second plurality of LED substrings, the first and second bias capacitors operating such that at some points in time the first plurality of LED substrings receives capacitively-limited current and at other points in time the second plurality of LED substrings receives capacitively-limited current. - View Dependent Claims (9, 10, 11)
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12. A driverless LED light engine having first and second AC power line terminals, the light engine comprising:
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a plurality of LED devices connected in series as a string of LEDs, the string of LEDs defined as having a first end termination and a second, opposing end termination, with a midpoint of the string of LEDs connected to the first AC power line terminal; a first rectifier diode connected between the first end termination of the string of LEDs and the second AC power line terminal; a second rectifier diode connected between the second end termination of the string of LEDs and the second AC power line terminal, wherein a first half of the string of LEDs conducts galvanic current during positive power line voltage half cycles from an AC power source and a second half of the string of LEDs conducts galvanic current during negative power line voltage half cycles from the AC power source; a first bias capacitor connected across a portion of the string of LEDs in such a manner as to cause a substring of LEDs in the first half of the string of LEDs to be illuminated before the beginning of the power line voltage half cycle corresponding to the galvanic forward conduction of the first half of the LED string; and a second bias capacitor connected across a portion of the string of LEDs in such a manner as to cause a substring of LEDs in the second half of the string of LEDs to be illuminated before the beginning of the power line voltage half cycle corresponding to the galvanic forward conduction of the second half of the LED string. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. A driverless LED light engine for energizing directly from an AC power source having at least first and second power terminals, the light engine comprising
a plurality of single LEDs connected in series to form an LED string, the LED string defined as including a midpoint such that the LED string includes a first LED substring and a second LED substring; -
a bridge rectifier disposed between the AC terminal and the LED string; a first capacitor connected between the first power terminal and the midpoint of the LED string; a second capacitor connected across an output of the bridge rectifier; a first bias capacitor connected between a first end termination of the LED string and the second power terminal; and a second bias capacitor connected between a second, opposing end termination of the LED string and the second power terminal.
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Specification