Pixel design for calibration compensation
An electronic display provides pulse-width modulation (PWM), data loading, and calibration. The electronic display includes: a light emitting diode (LED); a driving transistor including a source connected to a first terminal of the LED; a first transistor including a source connected to a second terminal of the LED and a gate connected to a scan driver; a storage capacitor having a first node connected to a gate of the driving transistor, and a second node connected to a drain of the first transistor; a second transistor configured to selectively couple the first node of the storage capacitor to a data driver; and a third transistor configured to selectively couple the second node of the storage capacitor to a calibration driver so that the storage capacitor provides a gate voltage corresponding to a sum of the data voltage and the calibration voltage to the gate of the driving transistor.
1. An electronic display, comprising:
a light emitting diode (LED) configured to emit light for a pixel of the electronic display;
a driving transistor including a source connected to a first terminal of the LED, the driving transistor configured to control current in the LED;
a first transistor including a source connected to a second terminal of the LED and a reference voltage;
a storage capacitor configured to provide a gate voltage to a gate of the driving transistor, the storage capacitor having a first node connected to the gate of the driving transistor and a second node connected to a drain of the first transistor;
a second transistor configured to selectively couple the first node of the storage capacitor to a data driver to provide a data voltage to the first node of the storage capacitor; and
a third transistor configured to selectively couple the second node of the storage capacitor to a calibration driver to provide a calibration voltage to the second node so that the storage capacitor provides a gate voltage corresponding to a sum of the data voltage and the calibration voltage to the gate of the driving transistor.
2. The electronic display of claim 1 , further comprising:
a pulse-width modulation (PWM) driver configured to provide a PWM signal to a drain of the driving transistor; and
a scan driver configured to provide scan signals to the gate of the first transistor, the gate of the second transistor, and the gate of the third transistor.
3. The electronic display of claim 2 , wherein to program the pixel with the data voltage:
the PWM driver is configured to provide the PWM signal transitioning between a first voltage and a second voltage lower than the first voltage to the drain of the driving transistor to turn on or off the driving transistor;
the scan driver is configured to provide a first scan signal having the first voltage to the gate of the first transistor to connect the second node to the reference voltage, and the scan driver is configured to provide a second scan signal having the first voltage to a gate of the second transistor to connect the first node to the data driver; and
the data driver is configured to provide a data signal having the data voltage to a source of the second transistor to set a voltage at the first node of the storage capacitor to the data voltage.
4. The electronic display of claim 3 , wherein to calibrate the pixel with the calibration voltage:
the scan driver is configured to provide a third scan signal having the second voltage to the gate of the second transistor to disconnect the second node from the reference voltage;
the scan driver is configured to provide a fourth scan signal having the first voltage to a gate of the third transistor to connect the second node to the calibration driver; and
the calibration driver is configured to provide a calibration signal at the calibration voltage to the source of the second transistor to set a voltage at the second node of the storage capacitor to the sum of the data voltage and the calibration voltage.
5. The electronic display of claim 4 , wherein the scan driver is configured to provide a fifth scan signal having the first voltage to an adjacent pixel to the pixel to program the adjacent pixel in connection with providing the fourth scan signal to the gate of the third transistor to calibrate the pixel.
6. The electronic display of claim 4 , wherein to drive the pixel, the PWM driver provides the PWM signal to the drain of the driving transistor, the LED emitting light according to the PWM signal responsive to the gate voltage exceeding a threshold gate voltage of the driving transistor.
7. The electronic display of claim 4 , further including a memory configured to store the calibration voltage, the calibration driver being further configured to retrieve the calibration voltage from the memory and provide the calibration voltage to a drain of the third transistor using the calibration signal.
8. The electronic display of claim 7 , wherein the memory is further configured to store a second calibration voltage for a second driving transistor configured to control current in a second LED of the electronic display, the second calibration voltage being different from the calibration voltage.
9. A head-mounted display (HMD), comprising:
a light emitting diode (LED) configured to emit light for a pixel of an electronic display;
a driving transistor including a source connected to a first terminal of the LED, the driving transistor configured to control current in the LED;
a first transistor including a source connected to a second terminal of the LED and a reference voltage;
a storage capacitor configured to provide a gate voltage to a gate of the driving transistor, the storage capacitor having a first node connected to the gate of the driving transistor and a second node connected to a drain of the first transistor;
a second transistor configured to selectively couple the first node of the storage capacitor to a data driver to provide a data voltage to the first node of the storage capacitor; and
a third transistor configured to selectively couple the second node of the storage capacitor to a calibration driver to provide a calibration voltage to the second node of the storage capacitor so that the storage capacitor provides a gate voltage corresponding to a sum of the data voltage and the calibration voltage to the gate of the driving transistor.
10. The MID of claim 9 , further comprising
a pulse-width modulation (PWM) driver configured to provide a PWM signal to a drain of the driving transistor; and
a scan driver configured to provide scan signals to the gate of the first transistor, the gate of the second transistor, and the gate of the third transistor.
11. The MID of claim 10 , wherein to program the pixel with the data voltage:
the PWM driver is configured to provide the PWM signal transitioning between a first voltage and a second voltage lower than the first voltage to the drain of the driving transistor to turn on or off the driving transistor;
a scan driver is configured to provide a first scan signal having the first voltage to the gate of the first transistor to connect the second node to the reference voltage, and the scan driver is configured to provide a second scan signal having the first voltage to a gate of the second transistor to connect the first node to the data driver; and
the data driver is configured to provide a data signal having the data voltage to a source of the second transistor to set a voltage of the first node of the storage capacitor to the data voltage.
12. The MID of claim 11 , wherein to calibrate the pixel with the calibration voltage:
the scan driver is configured to provide a third scan signal having the second voltage to the gate of the second transistor to disconnect the second node from the reference voltage;
the scan driver is configured to provide a fourth scan signal having the first voltage to a gate of the third transistor to connect the second node to the calibration driver; and
the calibration driver is configured to provide a calibration signal at the calibration voltage to the source of the second transistor to set a voltage at the second node of the storage capacitor to the of the data voltage and the calibration voltage.
13. The MID of claim 12 , wherein the scan driver is configured to provide a fifth scan signal having the first voltage to an adjacent pixel to the pixel to program the adjacent pixel in connection with providing the fourth scan signal to the gate of the third transistor to calibrate the pixel.
14. The MID of claim 12 , wherein to drive the pixel, the PWM driver provides the PWM signal to the drain of the driving transistor, the LED emitting light according to the PWM signal responsive to the gate voltage exceeding a threshold gate voltage of the driving transistor.
15. The MID of claim 12 , further including a memory configured to store the calibration voltage, the calibration driver being further configured to retrieve the calibration voltage from the memory and provide the calibration voltage to a drain of the third transistor using the calibration signal.
16. The MID of claim 15 , wherein the memory is further configured to store a second calibration voltage for a second driving transistor configured to control current in a second LED of the electronic display, the second calibration voltage being different from the calibration voltage.
17. A method for controlling a pixel of an electronic display, comprising:
setting a data voltage for programming the pixel across a first node and a second node of a storage capacitor responsive to connecting the second node of the storage capacitor to a reference voltage;
disconnecting the second node of the storage capacitor from the reference voltage;
providing a calibration voltage to the second node of the storage capacitor to set a voltage across the first node and the second node of the storage capacitor to a sum of the data voltage and the calibration voltage;
providing the voltage to a gate of the driving transistor to drive a light emitting diode (LED) according to a pulse-width modulation (PWM) signal responsive to the voltage exceeding a threshold gate voltage of the driving transistor; and
providing the PWM signal to a drain of a driving transistor driver.
18. The method of claim 17 , further comprising storing the calibration voltage in a memory and retrieving the calibration voltage from the memory to provide the calibration voltage to the second node of the storage capacitor.
19. The method of claim 17 , further comprising connecting the second node of the storage capacitor to the reference voltage by applying a first scan signal having a first voltage to a gate of a transistor, a drain of the transistor being connected to the second node of the storage capacitor, a source of the transistor being connected to the reference voltage, and wherein disconnecting the second node of the storage capacitor from the reference voltage includes applying a second scan signal having a second voltage lower than the first voltage to the gate of the transistor.
20. The method of claim 17 , further comprising providing a second data voltage to an adjacent pixel of the pixel in connection with providing the calibration voltage to the second node of the storage capacitor.