OLED Pixel Driving Circuit Threshold Voltage Compensation

The pixel driving circuit is divided into multiple functional modules: a driving module with driving transistor and first capacitor, an initialization module with initialization transistor, a data writing module with second transistor, and a light emitting control module with third and fourth transistors. Each module performs a specific function, allowing independent optimization and compensation for threshold voltage shifts without redesigning the entire circuit.

A first capacitor is introduced as an intermediary element between the gate of the driving transistor and ground. This capacitor compensates for threshold voltage shifts by maintaining a stable voltage relationship, thereby stabilizing the light emitting current without requiring complex active compensation circuits.

The light emitting control module is extracted as a separate functional unit that controls the charging and discharging of the first capacitor. By isolating this control function, the circuit ensures that the voltage across the capacitor (and thus the light emitting current) depends only on the data signal and reference voltages, not on the specific capacitance value, thereby achieving luminance uniformity without precise capacitance matching.

The circuit design changes the dependency relationship by making the light emitting current independent of the capacitor's capacitance value. Through the specific circuit configuration involving the driving transistor, first capacitor, and light emitting control module, the current is determined by voltage differences rather than RC time constants, eliminating the need for precise capacitance matching across different pixels.