Method of Operating a Display Driver

A drive method for a display device comprising a drive circuit, the display device comprising a plurality of pixels operable at a plurality of grey levels in accordance with a respective plurality of analog drive voltages, the drive circuit comprising a plurality of single grey-level channels, wherein each single grey-level channel comprises an input, an output and a signal processor connected between the input and output, wherein each signal processor comprises a digital-to-analog converter, “DAC”, and an operational amplifier, “op-amp”, having a voltage offset, the method comprising:

• converting a digital signal received at the input into an analog voltage at the output using each respective signal processor;
• switchably-receiving the analog voltage of each single grey-level channel of the plurality of single grey-level channels using a switching circuit connected to the output of each single grey-level channel;
• receiving each analog voltage from the switching circuit;
• and
• for each single grey-level channel, performing a calibration process to individually compensate for the voltage offset of each op-amp based on the received analog voltage for that grey level channel, wherein the calibration process comprises:
• individually determining the output response of each single grey-level channel to a plurality of digital inputs;
• and
• for each single grey-level channel, determining the digital input required to achieve each analog drive voltage at the output based on the individually-determined output response of the single grey-level channel,
• the method further comprising:
• selecting the plurality of grey levels based on the grey level response of the pixels to analog voltage;
• and
• determining the plurality of analog drive voltages required by the pixels to achieve the respective plurality of grey levels based on the grey level response of the pixels.

A system including a display device comprising a drive circuit, the drive circuit comprising:

• a plurality of single grey-level channels, wherein each single grey-level channel comprises an input, an output and a signal processor connected between the input and output, wherein each processor is arranged to convert a digital signal received at the input into an analog voltage at the output, and wherein each signal processor comprises a digital-to-analog converter, “DAC”, and an operational amplifier, “op-amp”, having a voltage offset;
• and
• a switching circuit connected to the output of each single grey-level channel, wherein the switching circuit is arranged to switchably-receive the analog voltage of each single grey-level channel of the plurality of single grey-level channels, wherein the system further comprises:
• a calibration sub-system connected to each op-amp, wherein the calibration sub-system is arranged to receive each analog voltage from the switching circuit and, for each single grey-level channel, perform a calibration process to individually compensate for the voltage offset of each op-amp based on the received analog voltage for that grey level channel, wherein the calibration process comprises:
• individually determining the output response of each single grey-level channel to a plurality of digital inputs;
• and for each single grey-level channel, determining the digital input required to achieve each analog drive voltage at the output based on the individually-determined output response of the single grey-level channel,
• wherein the calibration sub-system is further arranged to select the plurality of grey levels based on the grey level response of the pixels to analog voltage;
• and determine the plurality of analog drive voltages required by the pixels to achieve the respective plurality of grey levels based on the grey level response of the pixels.