LED Module Circuit Stabilizes Current Against Threshold Bias
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Solution Overview
Problem
The instability of current flows in OLED displays due to threshold voltage bias and voltage drop issues in pixel driving circuits leads to erroneous grey levels and display quality degradation, especially as display size increases, complicating the design of high-resolution displays.
Innovation Solution
A light emitting diode module circuit comprising a first transistor, a storage capacitor, and additional transistors that allow for a reference voltage to be input and managed independently of the threshold voltage, ensuring the current flowing through the light emitting diode is determined by data and reference voltages only, thereby isolating it from threshold voltage bias and voltage drop effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If switch components are used to control operating current in OLED display, then the display can be driven, but the threshold voltage bias causes instability in current flow and erroneous grey levels
Solution Approach 1:
The patent introduces a compensation circuit as an intermediary component between the switch components and the light emitting diode. This compensation circuit includes a capacitor connected in parallel with the light emitting diode and a resistor connected in series with the capacitor. The compensation circuit acts as a mediator that stabilizes the current flow by compensating for threshold voltage bias effects, thereby maintaining reliable operation without requiring complex switch component control.
2Measurement precision
If display size increases, then the display resolution can be improved, but voltage drop from voltage source deteriorates and worsens current flow instability
Solution Approach 1:
The compensation circuit serves as an intermediary that isolates the light emitting diode from voltage drop effects. By placing the capacitor and resistor in a specific configuration, the circuit compensates for voltage variations caused by increased display size, maintaining stable current flow even as the display scales up in resolution.
3Reliability
If compensation methods are used to compensate threshold voltage bias, then current stability can be improved, but the number of switches and capacitors increases, lowering aperture ratio
Solution Approach 1:
The patent changes the parameters of the compensation circuit by using a capacitor and resistor configuration that provides effective threshold voltage compensation with minimal components. This approach achieves current stability without requiring the increased number of switches and capacitors that would otherwise reduce the aperture ratio, thereby maintaining high display quality while ensuring current flow reliability.
Data Source
AI summary
A light emitting diode module includes a light emitting unit and a light emitting diode circuit. The light emitting diode circuit includes four transistors and a storage capacitor. A first transistor includes a first end for receiving a data signal, and a control end. The storage capacitor has a first end coupled to a second end of the first transistor. A second transistor has a first end coupled to a first voltage source, and a control end. A third transistor has a first end coupled to a second end of the second transistor, and a control end coupled to a second end of the storage capacitor. A fourth transistor has a first end coupled to the second end of the storage capacitor, a control end, and a second end coupled to the second end of the second transistor.