Pixel Driving Circuit for Efficient Micro LED Gray-Scale Control
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Solution Overview
Problem
Micro LED display devices face inefficiencies in power consumption and energy loss due to low luminous efficiency at low current densities when implementing low gray scale displays, as current-driving methods do not fully utilize the high luminous efficiency at high current densities.
Innovation Solution
A pixel driving circuit with a driving signal control sub-circuit and a driving duration control sub-circuit that controls both the magnitude and duration of the driving signal to optimize luminance, maintaining high current density and efficiency by adjusting the driving current and light-emitting duration based on data signals and voltage signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If current-driving methods are used to implement low gray scale displays, then the driving current is reduced, but the luminous efficiency decreases due to low current density
Solution Approach 1:
The patent employs pulse width modulation (PWM) to drive the micro LED, where the driving signal is applied in periodic pulses rather than continuously. By adjusting the duty cycle of these pulses, different gray scales are achieved while maintaining high current density during the active pulse period, thus preserving high luminous efficiency. The element is switched on and off rapidly, creating the perception of different brightness levels without operating at low current densities.
Solution Approach 2:
The patent dynamically adjusts the duration of the driving signal (pulse width) rather than statically reducing the current magnitude. The driving circuit controls the on-time and off-time of the current flow, allowing the current density to remain high during the on-period while achieving variable luminance through temporal dynamics. This dynamic control resolves the contradiction by making the system adaptive in time domain.
2Illumination intensity
If the driving current is reduced to achieve low gray scale displays, then the luminance is reduced, but the power consumption efficiency deteriorates
Solution Approach 1:
The driving circuit uses periodic pulsing with variable duty cycles to control luminance. During the on-phase of each period, high current density is maintained for efficient energy conversion to light. The off-phase allows energy recovery or reduced consumption. This periodic operation ensures that when energy is consumed, it is used efficiently at high current density, rather than continuously at low efficiency.
Solution Approach 2:
The system dynamically controls the temporal profile of current delivery, adjusting pulse width and frequency based on the desired gray scale level. This dynamic approach ensures that the micro LED operates in its high-efficiency region during active periods, optimizing power consumption efficiency across different luminance levels.
3Loss of energy
If the driving current is maintained at high levels, then the luminous efficiency is improved, but the power consumption increases
Solution Approach 1:
The patent reconciles high luminous efficiency with controlled power consumption through periodic operation. High current density is applied only during the pulse on-time when light emission is required, maximizing luminous efficiency during active periods. The overall power consumption is managed by controlling the duty cycle, so that high current is delivered only for the necessary fraction of time to achieve the desired average luminance.
Solution Approach 2:
The driving circuit dynamically balances current magnitude and duration to optimize the trade-off between luminous efficiency and power consumption. By adjusting pulse width and frequency in real-time based on display requirements, the system maintains high current density for efficiency while limiting total energy delivery to match the actual luminance demand, preventing excessive power consumption.
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 approach reduces power consumption and enhances luminous efficiency by maintaining high current density, allowing for efficient displays with varying gray scales without reducing the driving current, thus saving energy and improving display quality.
Implementation Method 1
a light-emitting diode (LED) has high luminous efficiency at a high current density and has a low luminous efficiency at a low current density
Implementation Method 2
the light-emitting diode (LED) has high luminous efficiency at a high current density
Data Source
AI summary
A pixel driving circuit includes a driving signal control sub-circuit and a driving duration control sub-circuit. The driving signal control sub-circuit is configured to provide a driving signal to the driving duration control sub-circuit under control of both a first scanning signal terminal and a enable signal terminal. The driving signal is related to a first data signal received at a first data signal terminal and a first voltage signal received at a first voltage signal terminal. The driving duration control sub-circuit is configured to, under control of the second scanning signal terminal and the enable signal terminal, transmit the driving signal to the element to be driven based on a second data signal with a gradually varying working potential received at the second data signal terminal. The first data signal is different from the second data signal.