Electronic devices having displays with compensation for oxide transistor threshold voltage

A display, comprising:

• an array of pixels, wherein each pixel in the array of pixels comprises a light-emitting diode, a drive transistor, and a switching transistor;
• gate driver circuitry configured to provide a control signal to the switching transistor at a first voltage level to turn on the switching transistor;
• a ground power supply voltage trace, wherein the light-emitting diode of each pixel in the array of pixels is coupled to the ground power supply voltage trace;
• sensing circuitry coupled to the ground power supply voltage trace, wherein the sensing circuitry is configured to measure a single display current that is associated with the entire array of pixels;
• and
• processing circuitry configured to change the first voltage level for the entire array of pixels based on the single display current, wherein the light-emitting diode of each pixel is coupled between a first power supply terminal and a second power supply terminal, wherein the sensing circuitry comprises a current sensing resistor coupled to the second power supply terminal and an analog-to-digital converter coupled to the current sensing resistor, wherein an output terminal of the analog-to-digital converter is coupled to the processing circuitry, wherein the processing circuitry is configured to change the first voltage level based on a comparison between the measured single display current and an expected current, wherein the processing circuitry is configured to incrementally change the first voltage level until the measured single display current matches the expected current, wherein the gate driver circuitry is configured to provide the control signal to the switching transistor at a second voltage level to turn off the switching transistor, wherein the processing circuitry is configured to change the second voltage level, and wherein the processing circuitry is configured to lower the first voltage level by a first amount and the second voltage level by the first amount in response to determining that the measured single display current is less than the expected current.

A method of operating a display with an array of pixels, sensing circuitry coupled to a ground power supply voltage trace that is coupled to each pixel in the array of pixels, and processing circuitry coupled to the sensing circuitry, wherein each pixel in the array of pixels includes a light-emitting diode, a drive transistor connected in series with the light-emitting diode, and a switching transistor that has a gate terminal that receives a scan control signal that is provided to the array of pixels, the switching transistor is coupled between a gate terminal of the drive transistor and one of a source terminal and a drain terminal of the drive transistor, and the other one of the source terminal and the drain terminal of the drive transistor is coupled to the light-emitting diode, the method comprising:

• displaying an image using the array of pixels;
• while displaying the image using the array of pixels, using the sensing circuitry to measure a display current value;
• and
• based at least on the display current value and an expected display current value, updating an active voltage level of the scan control signal, wherein updating the active voltage level of the scan control signal comprises lowering the active voltage level of the scan control signal in response to determining that the display current value is less than the expected display current value.