LED Driving Circuit Brightness Control via Current Dithering
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Solution Overview
Problem
Existing LED backlight systems face challenges in achieving a wide brightness adjustment range with high resolution while minimizing current variation, as pulse modulation increases power supply load and DC control struggles with fine brightness control.
Innovation Solution
An LED driving circuit comprising a voltage providing unit, a voltage setting unit, a current feedback unit, and a current dithering unit, which adjusts the driving current through the LED string using current setting voltages to achieve high emission resolution and wide brightness control, reducing current variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If pulse modulation is used to control LED backlight brightness, then brightness control capability is improved, but power supply load increases affecting other circuits
Solution Approach 1:
The patent applies periodic action by using pulse modulation with variable duty cycles to control LED backlight brightness. The driving circuit switches the LED current on and off periodically, adjusting the ratio of on-time to total period to achieve different brightness levels. This resolves the contradiction by enabling precise brightness control through timing ratios rather than continuous current variation, thereby maintaining stable power supply load while achieving wide brightness adjustment range.
2Power
If DC current control is used to control LED backlight brightness, then power supply load stability is improved, but brightness control range is limited
Solution Approach 1:
The patent applies dynamics by transitioning from static DC current control to dynamic pulse-width modulation (PWM). The driving circuit dynamically adjusts the duty cycle of the pulse signal while maintaining a stable average current level. This enables wide brightness control range through timing variations without causing large current fluctuations, thereby maintaining power supply load stability while achieving fine-grained brightness adjustment.
3Illumination intensity
If large current variation is used to achieve wide brightness range, then brightness adjustment range is improved, but emission resolution decreases
Solution Approach 1:
The patent applies periodic action through PWM modulation to resolve the contradiction between brightness range and resolution. By varying the duty cycle of periodic pulses rather than the amplitude of continuous current, the system achieves fine brightness steps within a wide range. Each pulse maintains consistent amplitude for high resolution, while the duty cycle provides wide adjustment range, eliminating the need for large current variations.
Solution Approach 2:
The patent applies dimensionality change by shifting the control parameter from current amplitude (one dimension) to time ratio/duty cycle (another dimension). Instead of varying current magnitude to control brightness, the system varies the temporal proportion of on-state within a periodic cycle. This dimensional shift enables both wide brightness range and high emission resolution simultaneously, as time ratio can be precisely controlled without affecting current stability.
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 enables a wide brightness adjustment range for LEDs with low current variation, enhancing emission resolution and reducing the load on the power supply.
Implementation Method 1
a light-emitting diode (LED) string
Data Source
AI summary
An LED driving circuit and a light-emitting apparatus thereof are provided. The driving circuit includes a voltage providing unit, a voltage setting unit, a current feedback unit and a current dithering unit. The voltage providing unit receives a voltage setting signal and an input voltage to provide an emission driving voltage to a first terminal of an LED string. The voltage setting unit receives an emission feedback signal to provide a voltage setting signal. The current feedback unit provides the emission feedback signal and sequentially receives current setting voltages to sequentially set a driving current flowing through the LED string according to the current setting voltages. The current dithering unit receives the backlight control signal to sequentially provide the current setting voltages.