LED Module PWM Pulse Shaping for Distal Light Uniformity
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Solution Overview
Problem
LED modules with long connection lines suffer from light attenuation and temporal light artifacts due to voltage and current drops, especially at the distal end units, leading to visible optical differences and potential blackouts, exacerbated by increasing length and distance from the terminal.
Innovation Solution
A circuit assembly with an electronic control gear and pulse width modulation (PWM) system that increases the voltage at the rising edge of pulses to compensate for voltage drops, ensuring consistent light emission across the LED module, particularly at shorter pulse widths, while maintaining safe dissipation power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the LED module length is increased to extend coverage area, then the illumination coverage is improved, but the connection line length increases causing voltage drops and light attenuation at distal units
Solution Approach 1:
The patent applies local quality by increasing the voltage specifically at the distal end units of the LED module where voltage drops occur, rather than uniformly across the entire module. The control device detects which units are connected and applies a boosted voltage only to those units, creating a non-uniform voltage distribution that compensates for the voltage drops in long connection lines while maintaining normal operation in shorter modules.
2Ease of operation
If the connection line length is increased to reach more distal units, then the coverage is improved, but the voltage and current drops increase causing darkening effects
Solution Approach 1:
The patent implements feedback by using a control device that detects which module units are actually connected to the LED module. Based on this detection feedback, the control device dynamically adjusts the voltage output, applying a boosted voltage only when distal units are present and need compensation. This closed-loop approach ensures reliable and consistent light emission across all connected units regardless of connection line length.
3Measurement precision
If PWM frequency is increased to improve dimming control, then the dimming precision is improved, but the temporal light artifacts and light attenuation are exacerbated at distal units
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the voltage level parameter based on the detected module configuration. When distal units are detected, the system changes the voltage parameter from nominal to boosted, which compensates for the attenuated PWM signals at higher frequencies. This parameter adjustment ensures that distal units receive sufficient voltage even when high-frequency PWM dimming is applied.
4Illumination intensity
If the voltage is increased to compensate for drops in long modules, then the light emission at distal units is improved, but the dissipation power increases potentially exceeding safe limits
Solution Approach 1:
The patent applies partial action by providing voltage compensation only to the extent necessary for distal units, rather than uniformly increasing voltage across all units. The control device detects which units are present and applies the boosted voltage only to those specific units that need compensation, leaving proximal units operating at nominal voltage. This selective approach compensates for power losses at distal units while minimizing overall dissipation power increase.
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 effectively reduces light attenuation and temporal artifacts, ensuring uniform light emission and compliance with future dimming requirements by compensating for voltage drops and maintaining safe operating conditions, thus enhancing the reliability and performance of LED modules.
Implementation Method 1
controlling the electronic control gear to increase an instantaneous value of the voltage supplied at the output terminal for a duration of a time slice of a predetermined width starting with a rising edge of a respective pulse with respect to a nominal voltage UN
Implementation Method 2
the control device operates the electronic switch via pulse width modulation with a duty-cycle D dependent from the dimming value at a predetermined period T
Implementation Method 3
Each module unit, also denoted as 'smallest electrical unit' (SEU), which forms a functional unit, that operates independently once an appropriate voltage is applied, is composed of an LED string, which includes one or more LEDs electrically coupled in series and/or parallel connection
Implementation Method 4
a current regulator, which compensates for a difference between the operating voltage of the module and a forward voltage of the LEDs and other optional electrical components, for example diodes or resistors, within the string, limits the current through the LED string and converts the same at the given voltage difference into dissipation power
Data Source
AI summary
An assembly and a method is provided where the LED module includes a plurality of module units interconnected between common connection lines in a sequential order with increasing distances towards a connection terminal of the LED module. The circuit assembly includes an output terminal having a first output terminal portion and a second output terminal portion, a main power supply for supplying an operation voltage potential to a first output terminal portion, a control device for generating a pulse width modulation signal, and an electronic switch coupled to the control device and configured to obtain the pulse width modulation signal and arranged to connect and disconnect a second output terminal portion to/from a reference potential in accordance with the pulse width modulation signal, such as to supply a pulse width modulated voltage to the output terminal. A pulse shaping unit is coupled to the control device.