LED Display Driving Circuit Pre-Charging and Current Control
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Solution Overview
Problem
Time delays in LED matrix displays due to capacitance charging hinder the timely illumination of LEDs, as the entire array's capacitors need to be charged before an LED can light up, leading to significant delays in turning on.
Innovation Solution
A driving circuit with a selection circuit, pre-charging circuit, and power circuit that includes a current control mechanism to supply different currents based on the driving current threshold values, allowing for efficient charging and minimizing time delays by pre-charging the equivalent capacitor and optimizing current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current source charges all capacitors on the N by M array before lighting an LED, then the LED can be illuminated, but significant time delay occurs
Solution Approach 1:
The patent applies preliminary action by pre-charging the equivalent capacitor during the dead time period before the LED is selected. The pre-charging circuit charges the capacitor Ci to a voltage close to the LED forward voltage VF0 in advance, so when the LED is selected, the capacitor is already prepared and can immediately supply current to the LED, eliminating the need to charge all capacitors in the array before illumination.
Solution Approach 2:
The patent extracts only the necessary capacitor (the equivalent capacitor Ci associated with the specific LED) from the entire array of capacitors for pre-charging. Instead of charging all N×M capacitors, the circuit identifies and pre-charges only the specific capacitor that will be needed for the selected LED, significantly reducing the charging time and energy consumption.
2Loss of time
If a high current is applied to quickly charge the capacitor, then the charging time is reduced, but current overshoot occurs
Solution Approach 1:
The patent applies dynamics by using a two-stage current control mechanism that dynamically adjusts the charging current based on the charging state. The first current source provides high current for rapid initial charging, and the second current source provides lower current for fine-tuning, allowing the system to adapt the current level to the real-time charging status and avoid overshoot.
Solution Approach 2:
The patent changes the current parameter dynamically during the charging process. The current control mechanism switches between two different current levels (first current and second current) based on the charging progress, transitioning from a higher current for fast charging to a lower current for precise control, thereby achieving both fast charging and avoidance of overshoot.
3Reliability
If the entire array's capacitors are charged before LED selection, then all LEDs can be illuminated, but the power consumption increases
Solution Approach 1:
The patent applies local quality by focusing the pre-charging action only on the specific equivalent capacitor Ci associated with the LED that will be selected, rather than charging all capacitors in the N×M array. This localized approach ensures that only the necessary capacitor is prepared, significantly reducing the total energy consumption while maintaining the ability to illuminate the selected LED.
Solution Approach 2:
The patent performs preliminary charging action during the dead time period, preparing the specific capacitor in advance before the LED is selected. This timing optimization allows the system to charge only the necessary capacitor at an optimal time, avoiding the energy waste of charging all capacitors continuously or simultaneously.
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
The solution significantly reduces the time required to charge the capacitors, enabling LEDs to turn on quickly by employing a two-stage charging mechanism that pre-charges the LEDs during dead time and adjusts current flow to minimize overshoot, resulting in a total charging time of less than 10 ns.
Implementation Method 1
Since the components in an LED matrix display have capacitance that needs to be charged before the LED becomes lit
Implementation Method 2
The current control mechanism is configured to supply a first current to the power source when a driving current through the first light emitter is less than or equal to a first threshold value
Data Source
AI summary
This disclosure provides a circuit and a method for driving an LED display. The driving circuit comprises a selection circuit for selecting a first light emitter from the plurality of light emitters, a pre-charging circuit for charging an equivalent capacitor of the display panel with respect to the selected first light emitter, and a power circuit for supplying power to the first light emitter after the first light emitter is selected, wherein the power circuit is configured to supply a driving current to the first light emitter in one or more stages. The driving circuit and method of this disclosure can be used to significantly increase the refresh rate and resolution of the LED display.