Pixel circuits for light emitting elements to mitigate degradation
Embodiments of pixel circuits for light emitting elements are disclosed herein. In one example, a pixel circuit includes a pixel driver configured to receive a data signal and drive a light emitting element based on the data signal, a first power signal coupled to an anode of the light emitting element through the pixel driver, and a second power signal coupled to a cathode of the light emitting element. In some embodiments, the second power signal is configured to vary based on the data signal. In some embodiments, in a first period of the data signal, a value of the second power signal is configured to be lower than a value of first power signal, and in a second period of the data signal, the value of the second power signal is configured to be higher than the value of the first power signal.
1. A pixel circuit, comprising:
a pixel driver configured to receive a data signal and drive a light emitting element based on the data signal;
a first power signal coupled to an anode of the light emitting element through the pixel driver;
a second power signal coupled to a cathode of the light emitting element; and
a third power signal coupled to the light emitting element, a value of the third power signal being lower than a positive power supply voltage, wherein:
the second power signal is configured to vary based on the data signal,
in a first period of the data signal, a value of the second power signal is configured to be lower than a value of the first power signal, and
in a second period of the data signal, the value of the first power signal is equal to the value of the third power signal and the value of the second power signal is configured to be higher than the value of the first power signal.
2. The pixel circuit of claim 1 , wherein:
in the first period of the data signal, the light emitting element is configured to emit light; and
in the second period of the data signal, the light emitting element is configured to be reversely biased.
3. The pixel circuit of claim 2 , wherein in the second period of the data signal, the value of the second power signal is configured to increase to be higher than the value of the first power signal.
4. The pixel circuit of claim 3 , wherein:
in the first period of the data signal, the value of the first power signal is equal to Vdd and the value of the second power signal is equal to Vss.
5. The pixel circuit of claim 2 , wherein
the first power signal is configured to vary between a minimum first power value and Vdd based on the data signal;
in the first period of the data signal, the value of the first power signal is equal to Vdd and the value of the second power signal is equal to a negative power supply voltage; and
in the second period of the data signal, the value of the first power signal is configured to decrease such that the value of the second power signal is higher than the value of the first power signal.
6. The pixel circuit of claim 5 , wherein in the second period of the data signal, the value of the first power signal is configured to decrease to Vss and the value of the second power signal is configured to increase to the positive power supply voltage.
7. The pixel circuit of claim 1 , wherein:
the second power signal varies between a negative power supply voltage and a maximum second power value; and
the maximum second power value is greater than the value of the third power signal.
8. The pixel circuit of claim 1 , further comprising a switch device coupled between the third power signal and the anode of the light emitting element, and a control signal applied on the switch device, wherein
in the second period of the data signal, the control signal is configured to turn on the switch device such that the first power signal applies no bias on the light emitting element, and the third power signal is coupled to the anode of the light emitting element.
9. The pixel circuit of claim 8 , wherein the switch device is a transistor, a drain terminal of the transistor being coupled to the third power signal, a source terminal of the transistor being coupled to the cathode of the light emitting element, and the control signal being an external control signal applied on a gate terminal of the transistor.
10. The pixel circuit of claim 8 , wherein the switch device is a transistor, a drain terminal of the transistor being coupled to the third power signal, a source terminal of the transistor being coupled to the cathode of the light emitting element, and the control signal being the second power signal applied on a gate terminal of the transistor.
11. A circuit for driving a plurality of light emitting elements, comprising:
a plurality of pixel circuits, each of the plurality of pixel circuits configured to drive one of a plurality of light emitting elements arranged in a plurality of rows and a plurality of columns and comprising:
a pixel driver configured to receive a data signal and drive a light emitting element based on the data signal;
a first power signal coupled to an anode of the light emitting element through the pixel driver;
a second power signal coupled to a cathode of the light emitting element; and
a third power signal coupled to the light emitting element, a value of the third power signal being lower than a positive power supply voltage, wherein:
the second power signal is configured to vary based on the data signal,
in a first period of the data signal, a value of the second power signal is lower than a value of the first power signal, and
in a second period of the data signal, the value of the first power signal is equal to the value of the third power signal and the value of the second power signal is higher than the value of the first power signal.
12. The circuit of claim 11 , wherein the second power signal is coupled to the cathode of each one of the plurality of light emitting elements arranged in the same row.
13. The circuit of claim 11 , wherein the first power signal is coupled to the anode of each one of the plurality of light emitting elements arranged in the same row.
14. The circuit of claim 11 , wherein the second power signal is coupled to the cathode of each one of the plurality of light emitting elements arranged in the plurality of rows and the plurality of columns, and the first power signal is coupled to the anode of each one of the plurality of light emitting elements arranged in the plurality of rows and the plurality of columns.
15. The pixel circuit of claim 11 , further comprising a switch device coupled to the third power signal and the light emitting element, and a control signal applied on the switch device, wherein
in the second period of the data signal, the control signal is configured to turn on the switch device such that the first power signal applies no bias on the light emitting element and the third power signal is coupled to the anode of the light emitting element.
16. The pixel circuit of claim 11 , wherein:
the first power signal is configured to vary based on the data signal;
in the first period of the data signal, the value of the first power signal is equal to Vdd and the value of the second power signal is equal to a negative power supply voltage; and
in the second period of the data signal, the value of the first power signal is configured to decrease such that the value of the second power signal is higher than the value of the first power signal.
17. A circuit for driving a light emitting element, comprising:
an alternating current (AC) power source circuit comprising a first power circuit configured to output a first power signal and a second power circuit configured to output a second power signal, wherein:
the first power signal ranges between a first high power value and a first low power value, the first high power value being greater than the first low power value, the first high and low power values being equal to or greater than zero;
the second power signal ranges between a second high power value and a second low power value, the second high power value being greater than the second low power value, the second high and low power values being lower than or equal to zero; and
a power swing value of the AC power source circuit is equal to a difference between the first high power value and the second low power value, the difference being equal to or greater than a driving voltage across the light emitting element.
18. The circuit of claim 17 , further comprising a first switch circuit coupled to the first power circuit and a second switch circuit coupled to the second power circuit, wherein:
the first switch circuit comprises a first capacitor, and the second switch circuit comprises a second capacitor;
in response to the first power circuit outputting the first high power value, the first capacitor is configured to be coupled to the first power circuit through a switch; and
in response to the second power circuit outputting the second low power value, the second capacitor is configured to be coupled to the second power circuit through another switch.
19. The circuit of claim 18 , wherein
in response to the first power circuit outputting the first low power value, the first capacitor is configured to be decoupled from the first power circuit through the switch; and
in response to the second power circuit outputting the second high power value, the second capacitor is configured to be decoupled from the second power circuit through the other switch.