Methods and apparatus for in-pixel driving of micro-LEDs
Methods and apparatus for in-pixel driving of micro-light-emitting diodes are disclosed. An example light-emitting diode driver includes a first input node to receive a data signal, a second input node to receive a reference signal having a first frequency, and a driver circuit including thin-film transistors to output a current pulse for driving a light-emitting diode, the current pulse having a width based on the data signal and the reference signal, the output signal having a second frequency that is greater than the first frequency.
1. A light-emitting diode driver comprising:
a first input node to receive a data signal;
a second input node to receive a reference signal having a first frequency; and
a driver circuit including thin-film transistors to output a current pulse for driving a light-emitting diode, the current pulse having a width based on the data signal and the reference signal, the output signal having a second frequency that is greater than the first frequency;
a first switching transistor coupled between an electric potential based on an image signal voltage and an in-pixel PWM unit;
a second switching transistor coupled to an output of the in-pixel PWM unit, a third switching transistor, and a first enable signal;
the third switching transistor further coupled to a first micro-LED and a second enable signal, wherein the third switching transistor inverts the second enable signal;
a fourth switching transistor coupled to the output of the in-pixel PWM unit, a fifth switching transistor, and the first enable signal; and
the fifth switching transistor further coupled to a second micro-LED and the second enable signal, wherein the fifth switching transistor inverts the second enable signal.
2. The light-emitting diode driver of claim 1 , wherein the current is a pulse width modulated (PWM) signal.
3. The light-emitting diode driver of claim 1 , wherein the driver circuit includes a transconductance stage and a transresistance stage.
4. The light-emitting diode driver of claim 3 , wherein the transconductance stage includes a differential pair and a current mirror.
5. The light-emitting diode driver of claim 4 , further including a current mirror coupled between a supply voltage and the differential pair.
6. The light-emitting diode driver of claim 4 , wherein the differential pair includes two n-channel transistors and the current mirror includes two p-channel transistors.
7. The light-emitting diode driver of claim 6 , wherein the n-channel transistors are at least one of low temperature polysilicon, indium phosphide (InP), gallium phosphide (GaP), gallium nitride (GaN), or indium gallium zinc oxide (IGZO) thin-film transistors.
8. The light-emitting diode driver of claim 6 , wherein the p-channel transistors are at least one of low temperature polysilicon, indium phosphide (InP), gallium phosphide (GaP), or gallium nitride (GaN).
9. The light-emitting diode driver of claim 1 , wherein the data signal is a direct current (DC) voltage signal.
10. The light-emitting diode driver of claim 1 , wherein the reference signal is one of a triangular wave signal or a sawtooth wave signal.
11. The light-emitting diode driver of claim 1 , wherein the thin-film transistor is a low-temperature polycrystalline or oxide thin-film transistor.
12. The light-emitting diode driver of claim 1 , wherein the light-emitting diode is a micro-light-emitting diode.
13. The light-emitting diode driver of claim 1 , wherein the driver circuit is to compare a first voltage of the data signal to a second voltage of the reference signal.
14. A micro-light-emitting diode (micro-LED) display comprising:
a plurality of pixels arranged in a two-dimensional matrix, the pixels each including:
a first micro-LED;
a second micro-LED; and
a drive circuit for each pixel of a plurality of pixels to drive a light-emission section, the drive circuit including:
an in-pixel pulse-width modulation (PWM) unit configured to:
receive an electric potential based on an image signal voltage and one of a sawtooth or triangular pulse, and
output a predetermined current pulse based on a comparison of the electrical potential and the one of the sawtooth or triangular pulse;
a first switching transistor coupled between the electric potential based on an image signal voltage and the in-pixel PWM unit;
a second switching transistor coupled to the output of the in-pixel PWM unit, a third switching transistor, and a first enable signal;
the third switching transistor further coupled to the first micro-LED and a second enable signal, wherein the third switching transistor inverts the second enable signal;
a fourth switching transistor coupled to the output of the in-pixel PWM unit, a fifth switching transistor, and the first enable signal; and
the fifth switching transistor further coupled to the second micro-LED and the second enable signal, wherein the fifth switching transistor inverts the second enable signal.
15. The micro-LED display of claim 14 , further including a plurality of micro-LEDs coupled to the drive circuit for each pixel.
16. The micro-light-emitting diode (micro-LED) display of claim 15 , wherein the drive circuit includes a memory cell coupled between the first switching transistor and the in-pixel PWM unit, the memory cell to store the electric potential based on the image signal for supplying the electric potential based on the image signal to the in-pixel PWM unit to generate a static image until the electric potential based on the image signal is refreshed.
17. The micro-LED display of claim 15 , further including a capacitor coupled to a connection between the first switching transistor and the in-pixel PWM unit, the capacitor to store the electric potential based on the image signal for supplying the electric potential based on the image signal to the in-pixel PWM unit to generate a static image until the electric potential based on the image signal is refreshed.
18. The micro-LED display of claim 14 , wherein each pixel further includes:
a third micro-LED coupled to the second switching transistor in parallel with the first micro-LED; and
a fourth micro-LED coupled to the fourth switching transistor in parallel with the second micro-LED,
wherein the first micro-LED and the third micro-LED illuminate with a first color and the second micro-LED and the fourth micro-LED illuminate with a second color different than the first color.
19. A light-emitting diode display comprising:
a first light-emitting diode;
a first light-emitting diode driver including:
a first input node to receive a first data signal;
a second input node to receive a reference signal having a first frequency; and
a first driver circuit for a first pixel of a plurality of pixels including a thin- film transistor for the first pixel to output a first current pulse for driving a light- emitting diode, the first current pulse having a width based on the first data signal and the reference signal, the first output having a second frequency that is greater than the first frequency;
a second light-emitting diode;
a second light-emitting diode driver including:
a third input node to receive a second data signal;
a third input node to receive a reference signal having the first frequency; and
a second driver circuit for a second pixel of the plurality of pixels including:
a second column driver for the second pixel;
a second row driver for the second pixel to supply a second scan signal;
a thin-film transistor for the second pixel to output a second current pulse for driving a light-emitting diode, the second current pulse having a width based on the second data signal and the reference signal, the second output having a third frequency that is greater than the first frequency; and
a third light-emitting diode coupled to a first switching transistor in parallel with the first light-emitting diode and a fourth light-emitting diode coupled to a second switching transistor in parallel with the second light-emitting diode, wherein the first light-emitting diode and the third light-emitting diode illuminate with a first color and the second light-emitting diode and the fourth light-emitting diode illuminate with a second color different than the first color.
20. The light-emitting diode display of claim 19 , wherein the first light-emitting diode and the second light-emitting diode are arranged in a first column of the light-emitting diode display and wherein the first light-emitting diode is arranged in a first row of the light-emitting diode display with the third light-emitting diode and the second light-emitting diode is are arranged in a second row of the light- emitting diode display with the fourth light-emitting diode.
21. The light-emitting diode display of claim 19 , wherein the first light emitting diode and the second light emitting diode have at least one of a length or a width that is less than 100 micrometers.
22. The light-emitting diode display of claim 19 , wherein the thin-film transistors are low-temperature polycrystalline or oxide thin-film transistors.