LED Drive Circuit with Output Capacitance for Peak Current Averaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing drive devices for light emitting elements, such as LEDs used in liquid crystal displays, face challenges in maintaining uniform luminance due to current-dependent luminance and voltage variations, leading to increased power supply burdens, size, and noise generation, especially when peak current surges occur.
Innovation Solution
A light emitting element drive device incorporating output capacitance and a power supply controller that adjusts output current based on load current information, using a switch section controlled by a pulse-like lighting signal and a constant current source, to average peak current and reduce noise, while ensuring stable brightness and low crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the amount of surge is increased to maintain brightness during impulse driving, then the brightness of images is maintained, but the burden on the power supply increases and the size and cost of the power supply increases
Solution Approach 1:
The power supply controller pre-charges the output capacitance before the impulse driving occurs. By anticipating the need for peak current and preparing the capacitance in advance, the system can deliver the required surge current without requiring the power supply to continuously provide high power capacity, thus reducing the power supply burden while maintaining brightness.
Solution Approach 2:
The system uses periodic impulse driving with duty cycle control instead of continuous high-current driving. The LED is driven in periodic pulses, allowing the power supply to provide average current at a lower level while the output capacitance supplements the peak current during active periods, reducing the overall power supply burden.
2Illumination intensity
If the amount of surge is increased to maintain brightness during impulse driving, then the brightness of images is maintained, but the size and cost of the power supply increases
Solution Approach 1:
The power supply controller pre-charges the output capacitance before the impulse driving occurs. By anticipating the need for peak current and preparing the capacitance in advance, the system can deliver the required surge current without requiring the power supply to continuously provide high power capacity, thus reducing the power supply burden while maintaining brightness.
3Illumination intensity
If the amount of surge is increased to maintain brightness during impulse driving, then the brightness of images is maintained, but noise generation increases
Solution Approach 1:
The system uses periodic impulse driving with duty cycle control instead of continuous high-current driving. The LED is driven in periodic pulses, allowing the power supply to provide average current at a lower level while the output capacitance supplements the peak current during active periods, reducing the overall power supply burden.
4Illumination intensity
If PWM control is used to adjust luminance in a wide dynamic range, then stable luminance adjustment is achieved, but the drive device complexity increases
Solution Approach 1:
The system uses periodic impulse driving with duty cycle control instead of continuous high-current driving. The LED is driven in periodic pulses, allowing the power supply to provide average current at a lower level while the output capacitance supplements the peak current during active periods, reducing the overall power supply burden.
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 effectively averages peak current, reduces power supply size and cost, and minimizes noise, enabling bright and clear monitor displays with reduced crosstalk by stabilizing the drive current and reacting to load variations.
Implementation Method 1
output capacitance configured to be capable of storing power supplied to the light emitting section
Implementation Method 2
a light emitting element that emits light with luminance depending on a flowing current, such as a light emitting diode (LED)
Data Source
AI summary
A light emitting element drive device includes: a light emitting section having a light emitting element; output capacitance capable of storing power supplied to the light emitting section; a driver connected between the light emitting section and a reference potential and including a switch section whose conductive state is controlled by a pulse-like lighting signal depending on magnitude of a load current and a constant current source section connected in series to the switch section; and a power supply controller being a power supply that provides drive power to the light emitting section and including a function to adjust an output current supplied to the output capacitance. The power supply controller changes the supply amount of the output current for the light emitting section from the power supply controller based on load current information that is necessary peak power of the light emitting section.