LED light source for backlighting with integrated electronics
First Claim
1. A light emitting diode (LED) light source for use in a backlight for a display comprising:
- at least one LED of a first color;
at least one LED of a second color;
at least one LED of a third color;
a plurality of current controllers, each controller connected to at least one LED of the first color, at least one LED of the second color, and at least one LED of the third color for controlling a brightness level of each color;
the at least one LED of the first color, the at least one LED of the second color, the at least one LED of the third color, and the plurality of controllers being mounted on a same circuit board; and
a memory mounted on the circuit board, the memory storing values for controlling an output current magnitude of each of the controllers so that a combined light output of the light source has characteristics set by the values stored in the memory.
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Accused Products
Abstract
An LED backlight structure and technique for setting the voltages and currents for the LEDs are described. In one embodiment, red LEDs are connected in series between a first voltage regulator and a first controllable current source, green LEDs are connected in series between a second voltage regulator and a second controllable current source, and blue LEDs are connected in series between a third voltage regulator and a third controllable current source. The current sources may linear current regulators. After all the LEDs are mounted on a printed circuit board, each voltage regulator is controlled so that there is a minimum voltage drop across the current source to minimize energy dissipation by the current source. Also, after all the LEDs are mounted on the printed circuit board, the current sources are controlled to balance the three colors to achieve a target light output of the board using a light detection chamber. In another embodiment, a constant current source is connected to the series string of LEDs. PWM controllers control transistor switches connected in parallel across groups of LEDs, where the duty cycles set the average current through each group of LEDs. The control values used to achieve the target light characteristics are then stored in a memory on the board. With such a technique, LEDs do not need to be binned to match their efficiencies, since the controllable voltage and current sources compensate for the variety of LED efficiencies. Accordingly, all boards will have the same target light output using the particular values stored on each board. In other embodiments, not all the LEDs of a particular color are connected in series. The brightness levels of the LEDs may be further controlled by a PWM controller. The backlight may be for an LCD television or other color display.
83 Citations
31 Claims
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1. A light emitting diode (LED) light source for use in a backlight for a display comprising:
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at least one LED of a first color;
at least one LED of a second color;
at least one LED of a third color;
a plurality of current controllers, each controller connected to at least one LED of the first color, at least one LED of the second color, and at least one LED of the third color for controlling a brightness level of each color;
the at least one LED of the first color, the at least one LED of the second color, the at least one LED of the third color, and the plurality of controllers being mounted on a same circuit board; and
a memory mounted on the circuit board, the memory storing values for controlling an output current magnitude of each of the controllers so that a combined light output of the light source has characteristics set by the values stored in the memory. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for producing a light source for use as a backlight comprising:
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providing on a circuit board at least one LED of a first color, at least one LED of a second color, and at least one LED of a third color;
providing on the circuit board a plurality of current controllers, each controller connected to at least a cathode end of a respective one of the at least one LED of the first color, at least one LED of the second color, and at least one LED of the third color;
providing on the circuit board a memory, values stored in the memory determining a current output of each of the controllers;
controlling the plurality of controllers to vary brightness levels of the at least one LED of the first color, at least one LED of the second color, and at least one LED of the third color while detecting a combined light output of the at least one LED of the first color, at least one LED of the second color, and at least one LED of the third color;
determining control signals for the plurality of controllers needed to obtain a target light output of the board from the combination of the first color, second color, and third color; and
storing in the memory values corresponding to the control signals needed to obtain the target light output. - View Dependent Claims (26, 27, 28, 29, 30, 31)
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Specification