Led illuminator apparatus, using multiple luminescent materials dispensed onto an array of leds, for improved color rendering, color mixing, and color temperature control

Abstract

An LED array includes three or more strings of bare LEDs mounted in close proximity to each other on a substrate. The strings of LEDs emit light of one or more wavelengths of blue, indigo and/or violet light, with peak wavelengths that are less than 490 nm. Luminescent materials deposited on each of the LED chips in the array emit light of different wavelength ranges that are of longer wavelengths than and in response to light emissions from the LED chips. A control circuit applies currents to the strings of LEDs, causing the LEDs in the strings to emit light, which causes the luminescent materials to emit light. A user interface enables users to control the currents applied by the control circuit to the strings of LEDs to achieve a Correlated Color Temperature (CCT) value and hue that are desired by users, with CIE chromaticity coordinates that lie on, or near to the black body radiation curve. Preferably a transparent material is dispensed on the substrate between the LED semiconductor chips to substantially surround the LED semiconductor chips. Thereafter at least one layer containing luminescent materials is applied on the LED semiconductor chips and the transparent material.