PWM Pixel Circuit for Precise LED Light-Level Control
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Solution Overview
Problem
High-resolution display panels face challenges in adjusting pixel light levels due to the exponential current-voltage curve of LEDs, making it difficult to control illumination levels effectively in each time interval.
Innovation Solution
A pixel structure comprising a light-emitting diode, transistors, and a capacitor, where the capacitor stores a data signal and a PWM signal is used to control the transistors, allowing for precise adjustment of the drive current and illuminating time, thereby overcoming the limitations of the exponential current-voltage curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of the display panel is increased, then the display quality is improved, but the adjustable time length for each pixel becomes smaller making it difficult to control light levels
Solution Approach 1:
The capacitor stores the data signal in advance during a first duration before the PWM signal is applied. This preliminary storage of voltage on the capacitor allows the pixel to have sufficient control time during the second duration when the PWM signal activates the transistor, effectively decoupling the resolution-related timing constraints from the light control duration.
2Power
If the voltage is raised to a higher value, then the current becomes much greater according to the exponential curve, but it becomes difficult to adjust the illumination level in each time interval
Solution Approach 1:
The invention uses PWM (pulse width modulation) signal to control the transistor in periodic on/off cycles. By varying the duty cycle of the PWM signal within a fixed period, the average current through the LED can be precisely controlled. This transforms the difficult continuous voltage adjustment problem into an easier discrete pulse width control problem, allowing precise illumination level adjustment despite the LED's exponential current-voltage characteristic.
Solution Approach 2:
The capacitor acts as an intermediary between the data signal and the PWM-controlled transistor. It stores the data voltage and releases it during the PWM activation period, mediating the control signal to ensure stable and precise current control through the transistor, thereby enabling fine illumination adjustment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables precise control over the illuminating time and light levels, improving the ability to adjust illumination levels and reducing the sudden increase in current with voltage, resulting in a more stable and efficient light emission.
Implementation Method 1
a capacitor, the first port of the capacitor is coupled to a gate of the first transistor, a second port of the capacitor is coupled to the cathode terminal of the light emitting diode, and the capacitor is configured to store a data signal in a first duration
Implementation Method 2
a light emitting diode, a cathode terminal of the light emitting diode is configured to receive a first power supply voltage
Implementation Method 3
the first transistor provides, in the conducting time, a drive current to the light emitting diode according to the data signal
Data Source
AI summary
The disclosure provides a light emitting diode including a light emitting diode (LED), a first transistor, a second transistor and capacitor. A cathode terminal of the LED is configured to receive a first power supply voltage. A first port of the capacitor coupled to the gate of the first transistor is configured to store a data signal in a first duration. A first port of the second transistor is configured to receive a second power supply voltage. A gate of the second transistor is configured to receive a PWM signal in a second duration. A second port of the second transistor is coupled to the second port of the first transistor. The second transistor is turned on for a conducting time in the second duration according to the PWM signal, and the first transistor provides, in the conducting time, a drive current to the LED according to the data signal.