Apparatus and method for controlling LED arrays
DCFirst Claim
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1. An apparatus for controlling the brightness of an LED array comprising:
- a current limiter disposed between the LED array and a power supply, for limiting an amount of current supplied to the entire LED array; and
a controller having an input coupled to receive a plurality of control signals and having an output coupled to the LED array for controlling the brightness of the LED array in accordance with said plurality of control signals.
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Abstract
A high precision, high efficiency controller for LED devices such as LED arrays includes a current limiter, driver and buffer.
192 Citations
12 Claims
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1. An apparatus for controlling the brightness of an LED array comprising:
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a current limiter disposed between the LED array and a power supply, for limiting an amount of current supplied to the entire LED array; and
a controller having an input coupled to receive a plurality of control signals and having an output coupled to the LED array for controlling the brightness of the LED array in accordance with said plurality of control signals. - View Dependent Claims (2)
a drive circuit coupled to said output; and
a buffer disposed between said drive circuit and said input for buffering said plurality of control signals.
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3. A display illuminated using a plurality of LEDs, the display comprising:
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(a) an array of LED devices wherein said array consists of;
(i) a plurality of individual LED devices connected in series to form a string;
(ii) a plurality of said strings connected in parallel to form said array;
(b) a current limiter disposed between a power supply and said array for limiting an amount of current supplied to said array; and
(c) a controller having an input adapted to receive a plurality control signals and an output coupled to said array for controlling a brightness of said array in accordance with said control signals.
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4. A display illuminated using a plurality of LEDs, the display comprising:
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(a) an array of LED devices wherein said array consists of;
(i) a plurality of individual LED devices connected in series to form a string;
(ii) a plurality of said strings connected in parallel to form said array;
(b) a current limiter disposed between a power supply and said array for limiting an amount of current supplied to said array; and
(c) a controller having an input adapted to receive a plurality of control signals and an output coupled to said array for controlling a brightness of said array in accordance with said control signals, wherein said controller comprises;
(i) a drive circuit coupled to said output; and
(ii) a buffer disposed between said drive circuit and said input for buffering said plurality of signals. - View Dependent Claims (5)
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6. A circuit for controlling the brightness of an LED array, the circuit comprising:
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(a) a current limiter having;
(i) a current limiter input coupled to a first pole of a power supply;
(ii) a PNP transistor;
having a collector coupled to said input;
(iii) a first resistor disposed between said input and an emitter of said PNP transistor;
(iv) a second resistor disposed between said emitter of said PNP transistor and ground;
(v) a first FET having a gate coupled to said emitter of said PNP transistor;
(vi) a third resistor disposed between said input and a source of said first FET transistor;
(vii) a fourth resistor disposed between a base of said PNP transistor and said source of said first FET; and
(viii) a current limiter output coupled to a first pole of the LED array and to a drain of said first FET;
(b) a driver having a driver input adapted to receive a plurality of signals useful for controlling a brightness of the LED array and having a driver output coupled to a second pole of the LED array, the driver further including;
(i) a push/pull buffer having a buffer input coupled to said driver input and a buffer output;
(ii) a second FET having a source coupled to ground, a drain coupled to said driver output and a gate; and
(iii) a fifth resistor disposed between said buffer output and said gate of said second FET. - View Dependent Claims (7, 8)
an NPN transistor having an emitter coupled to said buffer output, a base and a collector;
a second PNP transistor having a base coupled to said base of said NPN transistor, an emitter coupled to said emitter of said NPN transistor and to said buffer output, and a collector;
a sixth resistor having a first terminal coupled to said buffer input and a second terminal coupled to said base of said NPN transistor and to said base of said second PNP transistor;
a seventh resistor disposed between said collector of said second PNP transistor and ground; and
an eighth resistor disposed between said collector of said NPN transistor and a voltage input.
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9. A method for controlling an LED array comprising the steps of:
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receiving a control signal;
boosting a current of said control signal using a buffer that operates with a response time at least as fast as the shortest duration pulse of said control signal to obtain a buffered control signal;
supplying said buffered control signal to a driver to drive the LED array according to said buffered control signal; and
limiting an amount of current supplied to the entire array while maintaining continued operation of the LED array.
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10. A method for controlling the brightness of an LED array comprising the steps of:
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supplying power to the LED array in accordance with a control signal; and
preventing a magnitude of an amount of current supplied to the entire LED array from exceeding a predetermined threshold value while maintaining continued operation of the LED array. - View Dependent Claims (11)
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12. A method for controlling the brightness of an LED device comprising the steps of:
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receiving a pulse width modulated control signal representative of a desired LED device brightness;
supplying power to the LED device in accordance with said pulse width modulated control signal; and
preventing a magnitude of current drawn by the LED device from exceeding a predetermined threshold value while maintaining continued operation of the LED device.
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Specification