LED Dimming via Variable On-Period and Period Length
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Solution Overview
Problem
Existing light emitting diode (LED) dimming technologies require expensive microcontrollers with high resolution to achieve smooth light intensity adjustments, particularly at lower levels, as they necessitate significant changes in light intensity with each step, making them impractical for cost-effective implementations.
Innovation Solution
The process modifies the pulse width signal by varying both the on-period and period length in response to a target value, allowing an 8-bit microcontroller to generate pulse width modulation with imperceptible jumps in light intensity, using formulas to compute and store these values for efficient processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If digital pulse width modulation is used with standard microcontrollers to dim LED, then device complexity is reduced, but light intensity adjustment precision deteriorates causing noticeable jumps
Solution Approach 1:
The patent applies dynamics by making both the on-period and period length variable rather than fixed. The on-period is adjusted according to the target value, and the period length is simultaneously modified to compensate for quantization steps. This dynamic adjustment of two parameters together allows smooth light intensity transitions without requiring high-resolution fixed-step controllers.
Solution Approach 2:
The patent changes two parameters (on-period and period length) instead of just one. By modifying both parameters in coordination, the system achieves fine-grained light intensity control. The on-period determines the basic duty cycle while the period length adjustment compensates for discrete steps, effectively creating continuous control from an 8-bit microcontroller.
2Manufacturing precision
If 10-bit or higher resolution microcontrollers are used to achieve smooth dimming, then light intensity adjustment precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent adds another dimension to the control space by introducing period length as a second variable parameter. Instead of relying on high-resolution single-parameter control, the system uses coordinated adjustment of on-period and period length. This dimensional expansion allows an 8-bit microcontroller to achieve the same effective resolution as a 10-bit or higher controller would provide with single-parameter control.
3Device complexity
If fixed period length pulse width modulation is used, then device complexity is reduced, but light intensity smoothness deteriorates at lower intensity levels
Solution Approach 1:
The patent implements a feedback mechanism where the period length is adjusted based on the target value to compensate for quantization effects. By monitoring the desired light intensity level and adapting the period length accordingly, the system maintains smooth transitions across all intensity ranges. This feedback approach ensures that even at low intensity levels where fixed-period PWM produces noticeable steps, the light intensity remains perceptually smooth.
Data Source
AI summary
The invention concerns a process to dim a light emitting diode device of a motor vehicle. In order to keep changes of the light intensity from being noticeable, they must be appropriately small. Electronic dimmers with pulse width modulation have historically required a microcontroller with a pulse width modulation generator with at least 10 bits. In order to use cheaper controllers, the invention proposes that the pulse width signal be modulated as a function of a variable on-period and a simultaneously variable period length.