Display with localized backlight dimming
A display may have an array of display pixels for displaying images for a user. A backlight unit may provide backlight for the display pixels. The backlight unit may have a substrate such as a printed circuit substrate. An array of locally dimmable backlight elements may be mounted on the substrate. The substrate may be mounted against an inner surface of a metal electronic device housing or other support structure in an electronic device. Each backlight element may have a semiconductor package containing a semiconductor die. The semiconductor die may have a light-emitting diode and a light-emitting-diode control circuit. The light-emitting-diode control circuit may have a pair of transistors and a capacitor. One of the transistors may be connected in series with the light-emitting diode. The light-emitting diode control circuit may receive control signals on a gate line terminal and a source line terminal.
1. A display, comprising:
an array of display pixels; and
a backlight that provides backlight illumination for the array of display pixels, wherein the backlight comprises an array of backlight elements, wherein each backlight element includes a light-emitting diode and a light-emitting-diode control circuit that controls how much backlight is emitted by the light-emitting diode, wherein each light-emitting diode in the backlight is independently controlled by a respective one of the light-emitting-diode control circuits, wherein each backlight element has a plastic semiconductor package, wherein the light-emitting-diode control circuit of each backlight element comprises first and second transistors and a capacitor coupled between the first and second transistors, and wherein the first and second transistors, the capacitor, and the light-emitting diode of each backlight element are part of a common semiconductor die that is packaged in the plastic semiconductor package.
2. The display defined in claim 1 wherein the light-emitting diode of each backlight element is connected in series with the second transistor of that backlight element.
3. The display defined in claim 1 wherein the plastic semiconductor package for each backlight element also contains the light-emitting diode of another one of the backlight elements.
4. The display defined in claim 1 wherein the plastic semiconductor package for each of the backlight elements contains four of the backlight elements.
5. The display defined in claim 1 further comprising a substrate on which the array of backlight elements is mounted.
6. The display defined in claim 5 further comprising metal structures, wherein the substrate is mounted on the metal structures to dissipate heat from the backlight elements through the metal structures.
7. The display defined in claim 6 wherein the metal structures comprise electronic device housing structures.
8. The display defined in claim 6 wherein the array of display pixels comprises an array of liquid crystal display pixels.
9. An electronic device, comprising:
an electronic device housing;
display layers that display images; and
a backlight with an array of locally dimmed backlight elements that provide backlight illumination for the display layers, each backlight element including a light-emitting diode and a light-emitting-diode control circuit, wherein each light-emitting diode in the backlight is independently controlled by a respective one of the light-emitting-diode control circuits, wherein the light-emitting-diode control circuit comprises first and second transistors and a capacitor coupled between the first and second transistors, wherein the light-emitting diode, the first transistor, the second transistor, and the capacitor of each backlight element are formed as part of a common semiconductor die.
10. The electronic device defined in claim 9 wherein the backlight is mounted on an interior surface of the electronic device housing and wherein the electronic device housing comprises metal.
11. A display, comprising:
liquid crystal display layers that display images; and
a backlight unit with an array of locally dimmed backlight elements that provide backlight for the liquid crystal display layers, each backlight element including a light-emitting diode and a light-emitting-diode control circuit, wherein the light-emitting-diode control circuit comprises first and second transistors and a capacitor coupled between the first and second transistors, wherein the light-emitting diode, the first transistor, the second transistor, and the capacitor are formed as part of a common semiconductor die in a plastic semiconductor package, and wherein each light-emitting diode in the backlight is independently controlled by a respective one of the light-emitting-diode control circuits.
12. The display defined in claim 11 wherein the light-emitting-diode control circuit of each backlight element receives control signals from a gate line and a source line.