LED Operating Circuit with Adaptive Inductance for Dimming Resolution
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Solution Overview
Problem
Existing LED dimming methods using pulse-modulated pulses face limitations in resolution and efficiency due to fixed time constants and discrete clock frequency adjustments, which result in perceivable brightness jumps, especially at low light levels.
Innovation Solution
The solution involves adaptive time constants for the current curve's rising and falling edges, allowing variable clock frequencies based on dimming levels, achieved through a circuit design with multiple inductances and a second switch to adjust inductance, enabling continuous or discrete changes in clock frequency and improved edge steepness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the clock frequency is increased to improve brightness resolution, then the optical resolution is improved, but switching losses increase
Solution Approach 1:
The patent applies dynamics by making the clock frequency variable rather than fixed. The control circuit dynamically adjusts the clock frequency based on the dimming level: using higher frequencies at low dimming levels where human eyes are more sensitive to brightness changes, and lower frequencies at high dimming levels where switching losses become more significant. This dynamic adaptation resolves the contradiction by optimizing the trade-off between brightness resolution and switching losses under different operating conditions.
2Measurement precision
If the time constant is decreased to improve resolution, then the brightness resolution is improved, but switching frequency increases causing higher losses
Solution Approach 1:
The patent makes the time constant dynamic by adjusting the inductance value based on operating conditions. The control circuit varies the inductance to achieve optimal time constants for different dimming levels, allowing fast response (small time constant) when high resolution is needed while accepting higher switching frequencies, and slower response (larger time constant) when switching losses can be reduced. This dynamic adjustment resolves the contradiction between resolution and switching losses.
3Device complexity
If discrete clock frequency steps are used to simplify control, then the device complexity is reduced, but perceivable brightness jumps occur
Solution Approach 1:
The patent implements feedback by having the control circuit continuously monitor the dimming level and adjust the clock frequency in real-time based on human visual sensitivity characteristics. The feedback mechanism ensures that frequency transitions are timed and sized to avoid perceivable brightness jumps, maintaining smooth dimming performance while managing control complexity through intelligent algorithms.
4Loss of energy
If the inductance is increased to reduce switching frequency, then switching losses are reduced, but the time constant increases reducing resolution
Solution Approach 1:
The patent resolves this contradiction by making the inductance value dynamic rather than fixed. The control circuit adjusts the inductance based on the operating point: using smaller inductance values when high resolution is required (accepting higher switching frequencies and losses), and larger inductance values when switching losses are the primary concern. This dynamic adjustment allows the system to optimize both resolution and efficiency under different operating conditions.
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 approach enhances the optical resolution of LED light pulses and reduces perceivable brightness jumps, particularly at low dimming levels, while managing switching losses by dynamically adjusting clock frequency according to dimming conditions.
Implementation Method 1
An inductor can be used to store energy
Implementation Method 2
light-emitting diode (LED)
Data Source
Figure 1~2
Figure 3~3a
Figure 4
AI summary
The invention relates to a method and an operating circuit for operation of an LED with pulse-modulated pulses which are produced by clocked charging and discharging of an energy store (L1, L2). The clock frequency is variable. The resolution with a low basic brightness of the LED can be increased by choosing a higher clock frequency, while a lower clock frequency can be chosen at the higher basic brightness, in order to keep the losses low.