Electronic device display with monitoring circuitry

• US 9,947,255 B2
• Filed: 09/23/2016
• Issued: 04/17/2018
• Est. Priority Date: 08/19/2016
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Zhang, Zhen, Ahmed, Izhar, Kim, Hoon Sik
• Primary Examiner(s): Cheng, Joe H
• Application Number:
  US15/274,942
• Publication Number:
  US 20180053455A1
• Time in Patent Office: 571 Days
• CPC Class Codes: G01L 1/2281 for temperature variations
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0083 by measuring variation of impedance, e.g. resistance, capacitance, induction
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2330/12 Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 3/006 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 Class Codes: G09G 3/035 for flexible display surfaces
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G11C 19/28 using semiconductor elements G11C19/14, G11C19/36 take precedence
• CPC Class Codes: G11C 7/04 with means for avoiding disturbances due to temperature effects
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 77/111 Flexible substrates
• CPC Class Codes: Y02E 10/549 Organic PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

An electronic device may have a flexible display such as an organic light-emitting diode display. A strain sensing resistor may be formed on a bent tail portion of the flexible display to gather strain measurements. Resistance measurement circuitry in a display driver integrated circuit may make resistance measurements on the strain sensing resistor and a temperature compensation resistor to measure strain. A crack detection line may be formed from an elongated pair of traces that are coupled at their ends to form a loop. The crack detection line may run along a peripheral edge of the flexible display. Crack detection circuitry may monitor the resistance of the crack detection line to detect cracks. The crack detection circuitry may include switches that adjust the length of the crack detection line and thereby allow resistances to be measured for different segments of the line.

Claims

1. A display system, comprising:

a flexible display having a bent portion;

a strain-sensitive resistor on the bent portion that has a first resistance;

a temperature calibration resistor on the flexible display that has a second resistance; and

a resistance measurement circuit that measures the strain in the bent portion of the flexible display by subtracting the second resistance from the first resistance.

2. The display system defined in claim 1 further comprising a display driver integrated circuit that supplies data to pixels in the flexible display, wherein the resistance measurement circuit forms part of the display driver integrated circuit.

3. The display system defined in claim 2 wherein the flexible display comprises an organic light-emitting diode display having an array of pixels that receive the data from data lines in the flexible display, wherein the flexible display has an active area that includes the array of pixels and has a tail portion that includes the bent portion, wherein the display system further comprises a flexible printed circuit that is coupled to the tail portion, and wherein the display driver integrated circuit is mounted to the flexible printed circuit.

4. The display system defined in claim 3 further comprising test pads on the flexible printed circuit that are configured to couple to probes from a test system.

5. A display system, comprising:

a flexible display having an array of pixels and having a bent tail portion;

first and second strain sensing resistors on opposing edges of the bent tail portion; and

a resistance measurement circuit that is configured to measure strain in the bent tail portion by measuring resistances for the first and second strain sensing resistors.

6. The display system defined in claim 5 further comprising:

at least one temperature compensation resistor in the bent tail portion, wherein the resistance measurement circuit is configured to measure the strain in the bent tail portion based at least partly on a temperature compensation resistance measurement from the temperature compensation resistor.

7. The display system defined in claim 6 wherein the bent tail portion bends about a bend axis and wherein the temperature compensation resistor comprises a meandering metal trace with a plurality of elongated lines that extend parallel to the bend axis.

8. The display system defined in claim 7 wherein the first and second strain sensing resistors each have a respective meandering metal trace with a plurality of elongated lines that extend perpendicular to the bend axis.

9. The display system defined in claim 5 further comprising a display driver integrated circuit that supplies data to the array of pixels through data lines that extend across the bent tail portion and wherein the resistance measurement circuit forms part of the display driver integrated circuit.

10. The display system defined in claim 9 further comprising:

first and second temperature compensation resistors in the bent tail portion; and

a flexible printed circuit that is coupled to the bent tail portion, wherein the display driver integrated circuit is mounted to the flexible printed circuit and wherein the flexible display comprises an organic light-emitting diode display.

11. The display system defined in claim 5 wherein the resistance measurement circuit comprises:

a first voltage sensor that measures a voltage across the first strain sensing resistor; and

a second voltage sensor that measures a voltage across the second strain sensing resistor.

12. The display system defined in claim 5 wherein the resistance measurement circuit comprises:

a current source that applies a current through the temperature compensation resistor; and

a voltage sensor that measures a voltage across the temperature compensation resistor.

13. The display system defined in claim 12 wherein the flexible display comprises at least one pad and a positive power supply line, wherein the power supply line is coupled to the pad, and wherein the current source is coupled to the pad.

14. The display system defined in claim 5 further comprising:

first and second temperature compensation resistors in the bent tail portion, wherein the resistance measurement circuit is configured to measure the strain in the bent tail portion based at least partly on a resistance measurements from the first and second temperature compensation resistors.

15. A display system, comprising:

a flexible display having an array of pixels and having a bent tail portion;

a strain sensing resistor on the bent tail portion;

a temperature compensation resistor on the flexible display; and

a resistance measurement circuit that is configured to measure strain in the bent tail portion by measuring resistances for the strain sensing resistor and temperature compensation resistor.

16. The display system defined in claim 15 wherein the bent tail portion bends about a bend axis and wherein the strain sensing resistor has a meandering metal trace with a plurality of elongated lines that extend perpendicular to the bend axis.

17. The display system defined in claim 16 wherein the temperature compensation resistor comprises a meandering metal trace with a plurality of elongated lines that extend parallel to the bend axis.

18. The display system defined in claim 17 further comprising a display driver integrated circuit that supplies data to the array of pixels through data lines that extend across the bent tail portion and wherein the resistance measurement circuit forms part of the display driver integrated circuit.

19. The display system defined in claim 18 wherein the resistance measurement circuit comprises:

a current source that applies a current through the strain sensing resistor and the temperature compensation resistor;

a first voltage sensor that measures a voltage across the strain sensing resistor; and

a second voltage sensor that measures a voltage across the temperature compensation resistor.

20. The display system defined in claim 19 wherein the flexible display comprises at least one pad and a positive power supply line, wherein the power supply line is coupled to the pad, and wherein the current source is coupled to the pad.