LED Driver Reference Level Adjustment for PWM Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing light emitting diode (LED) driving apparatuses face challenges in stabilizing output voltage, particularly during pulse width modulation (PWM) dimming, leading to current imbalances and unstable luminance due to voltage deviations between LED channels connected in series.
Innovation Solution
A light emitting diode driving apparatus that includes a power supplying unit, a driving unit, and a controlling unit. The controlling unit senses the PWM duty and adjusts the reference level to match the detection voltage level, ensuring stable voltage control by increasing or maintaining the reference level based on the PWM duty, thereby stabilizing the output voltage and preventing switch saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If voltage applied to the switch is decreased to maintain operation in saturation region, then power consumption and heat generation are decreased, but the LED driving current becomes distorted and unstable
Solution Approach 1:
The patent applies dynamics by making the reference voltage level adjustable rather than fixed. The controlling unit dynamically changes the reference voltage level based on the PWM duty cycle, allowing the system to adapt to different operating conditions. This resolves the contradiction by enabling the switch to operate in saturation region at high PWM duties (reducing power consumption) while maintaining stable current at low PWM duties through increased reference voltage level.
Solution Approach 2:
The patent changes the parameter of reference voltage level based on PWM duty cycle. When PWM duty is low, the reference voltage level is increased to prevent current distortion; when PWM duty is high, the reference voltage level is maintained at a lower value to reduce power consumption. This parameter change strategy directly resolves the technical contradiction between energy efficiency and current stability.
2Loss of energy
If voltage applied to the switch is decreased to maintain operation in saturation region, then power consumption and heat generation are decreased, but control of desired brightness level becomes difficult
Solution Approach 1:
The system dynamically adjusts the reference voltage level according to PWM duty cycle, making brightness control easier at low duty cycles while maintaining energy efficiency at high duty cycles. The controlling unit responds to PWM signals by modifying the reference voltage, enabling precise brightness control across the entire PWM range.
Solution Approach 2:
By changing the reference voltage level parameter based on PWM duty, the system achieves both low heat generation and easy brightness control. The reference voltage is increased only when necessary (low PWM duty), allowing full brightness control capability while minimizing overall heat generation during normal operation.
3Volume of moving object
If LEDs are connected in series to form LED channels, then compact form factor is achieved, but voltage deviations occur between LEDs causing current imbalance
Solution Approach 1:
The patent uses feedback by continuously monitoring the actual voltage across LED channels and comparing it with the reference voltage level. The controlling unit adjusts the switch timing based on this comparison to compensate for voltage deviations, thereby maintaining current balance despite the series connection configuration that enables compact form factor.
Solution Approach 2:
The system changes the reference voltage level parameter dynamically to compensate for voltage deviations in series-connected LED channels. By adjusting this parameter based on actual channel voltage and PWM duty, the patent maintains current balance while preserving the compact design enabled by series connections.
Data Source
AI summary
There is provided a light emitting diode driving apparatus, including: a power supplying unit converting input power into driving power according to a control and supplying the converted driving power to a light emitting diode channel; a driving unit controlling current flowing in the light emitting diode channel according to a pulse width modulation (PWM) dimming signal from the outside; and a controlling unit comparing a reference level set by a duty of the PWM dimming signal with a detection voltage level of the light emitting diode channel and controlling a power converting operation of the power supplying unit according to the comparison result.