Systems and methods for indirect threshold voltage sensing in an electronic display

Patent metadata

Field	Value
Publication number	US-10360827-B2
Application number	US-201615273470-A
Country	US
Kind code	B2
Filing date	Sep 22, 2016
Priority date	Oct 9, 2015
Publication date	Jul 23, 2019
Grant date	Jul 23, 2019

Abstract

An electronic device includes one or more unit pixels and threshold voltage (Vth) sensing circuitry. The threshold voltage sensing circuitry senses Vth of the one or more unit pixels, by: sampling a charge of a capacitor of the one or more unit pixels, transitioning from the sampling, and reading out the threshold voltage based upon a change in the charge of the capacitor, such that an operation of the one or more unit pixels may be modified based upon the threshold voltage.

First claim

What is claimed is:

1. A processor-implemented method for threshold voltage (Vth) sensing, comprising:
sampling a charge of a capacitor of a unit pixel by configuring the unit pixel, such that a voltage of a second node of the unit pixel is a data voltage (Vdata) supplied by a first data line and a voltage of a third node of the unit pixel is an initialization voltage (Vini);
shorting a feedback capacitor such that a voltage of a first plate of the capacitor is a first voltage of the unit pixel and a voltage of a second plate of the capacitor is the first voltage minus a Vth;
transitioning the voltage of the second node to a sum of the Vini and the Vth;
transitioning the voltage of the third node to the Vini;
reading out the Vth based at least in part on a change in the charge of the capacitor; and
modifying an operation of the unit pixel based at least in part on the Vth, wherein the reading out of the Vth is made without toggling global busses coupled to the unit pixel.

2. The processor-implemented method of claim 1 , wherein the reading out comprises:
removing a short of the feedback capacitor while voltages of the capacitor remain constant;
determining an output voltage (Vout); and
determining the Vth based at least in part on the Vout, the first voltage, and the Vini.

3. The processor-implemented method of claim 1 implemented using at least a source line carrying the Vini, wherein the sampling comprises actuating settings of the unit pixel such that the voltage of the third node of the unit pixel transitions to a voltage difference between the Vdata and the Vth.

4. The processor-implemented method of claim 3 , comprising:
removing a short of the feedback capacitor, such that the voltage of the third node transitions from the voltage difference between the Vdata and the Vth to the Vini;
determining an output voltage (Vout); and
determining the Vth based at least in part on the Vout, the Vini, and the Vdata.

5. The processor-implemented method of claim 4 , wherein Vth is determined according to the relationship: the Vout=the Vini−(the Vdata−the Vini−the Vth).

6. An electronic device, comprising:
one or more unit pixels each comprising a first node, a second node, and a third node; and
threshold voltage (Vth) sensing circuitry configured to sense Vth of the one or more unit pixels, wherein the Vth sensing circuitry is configured to initialize the one or more unit pixels prior to sensing the Vth of the one or more unit pixels such that a voltage of the second node of the one or more unit pixels is set to a data voltage (Vdata) supplied by a Vdata line and a voltage of the third node is set to an initialization voltage (Vini) supplied by a source line, by:
sampling a charge of a capacitor of the one or more unit pixels, wherein the voltage of the second node remains at the Vdata during the sampling, and wherein the voltage of the third node transitions to a voltage difference between the Vdata and the Vth during the sampling;
transitioning from the sampling;
reading out the Vth based at least in part on a change in the charge of the capacitor; and
modifying an operation of the one or more unit pixels based at least in part on the Vth, and wherein the reading out of the Vth is performed without toggling global busses coupled to each of the one or more unit pixels.

7. The electronic device of claim 6 , wherein the transitioning from the sampling comprises the voltage of the second node transitioning to a sum of the Vini and the Vth, and the voltage of the third node transitioning to the Vini.

8. The electronic device of claim 7 , wherein the reading out comprises determining the Vth based at least in part on the Vini, the Vdata, and a known output voltage (Vout).

9. The electronic device of claim 8 , wherein the Vth is determined according to the following relationship: the Vth=2*the Vini−the Vdata+the Vout.

10. The electronic device of claim 6 , wherein the reading out comprises determining the Vth based at least in part on the Vini, the Vdata, and a known output voltage (Vout), and wherein electrical signals provided from the source line remain constant during sensing.

11. The electronic device of claim 10 , wherein the reading out comprises transitioning the voltage at the third node to equal the Vini by removing a short of a feedback capacitor.

12. The electronic device of claim 6 , wherein the Vth sensing circuitry operates by:
applying a step down voltage to the one or more unit pixels to cause the voltage of the second node to equal the Vini and a voltage of the first node to equal the Vdata supplied via the source line; and
outputting the Vth based at least in part on a known output voltage measured via an additional source line, the Vdata, and the Vini.

13. A tangible, non-transitory, machine-readable medium, comprising machine-readable instructions to:
sample a charge of a capacitor of a unit pixel comprising a first node, a second node, and a third node by:
setting a first scanning signal and a second scanning signal to a high logic signal and setting a third scanning signal and an emitter signal to a low logic signal;
closing a first switch, such that a voltage of the second node is set to a first applied reference voltage and a voltage of the third node is set to a threshold voltage (Vth);
setting the first scanning signal to the low logic signal; and
setting the second scanning signal and the third scanning signal to the high logic signal, wherein the voltage of the second node is set to a sum of a second applied reference voltage and the Vth, and wherein the voltage of the third node is set to the second applied reference voltage;

sense the Vth using a data line carrying the second applied reference voltage;
read out the Vth based at least in part on a change in the charge of the capacitor configured to cause variable voltage outputs in response to the second applied reference voltage and the first applied reference voltage by:
setting the first scanning signal and the second scanning signal to the high logic signal; and
determining the Vth based at least in part on the second applied reference voltage and a voltage output (Vout); and

modifying an operation of the unit pixel based at least in part on the Vth, wherein the first applied reference voltage and the second applied reference voltage remain constant during Vth sensing.

14. The tangible, non-transitory, machine-readable medium of claim 13 , wherein sensing the Vth includes using a data line carrying the first applied reference voltage, and wherein the determining the Vth is based at least in part on the first applied reference voltage, the second applied reference voltage, and the Vout.

15. The tangible, non-transitory, machine-readable medium of claim 13 , wherein the first applied reference voltage and the second applied reference voltage are provided to the unit pixel via one or more global busses that are not toggled during Vth sensing.

16. A processor-implemented method for threshold voltage (Vth) sensing, comprising:
sampling a charge of a capacitor of a unit pixel by actuating settings of the unit pixel such that a second node of the unit pixel registers a voltage of a data voltage (Vdata) supplied by a first data line and a voltage of a third node of the unit pixel transitions to equal a voltage difference between the Vdata and the Vth, wherein at least a source line is configured to transmit an initialization voltage (Vini);
transitioning from sampling by removing a short of a feedback capacitor such that the voltage of the third node of the unit pixel transitions from the volt

Assignees

• Apple Inc

Inventors

• Bi Yafei
• Wang Xiaofeng
• Li Haifeng
• Vahid Far Mohammad B
• Bae Hopil
• Lin Hung Shen
• Nho Hyunwoo
• Yao Wei H

Classifications

• G09G3/006 Primary

  Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays (testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309) · CPC title

• G09G3/3233

  with pixel circuitry controlling the current through the light-emitting element · CPC title

• G09G2310/061

  for resetting or blanking · CPC title

• G09G2310/0202

  Addressing of scan or signal lines · CPC title

• G09G2320/045

  Compensation of drifts in the characteristics of light emitting or modulating elements · CPC title