LED Load Current Control Using Burst-Mode Dimming
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Solution Overview
Problem
Existing LED light sources face challenges in efficiently controlling light intensity across a wide range, particularly when dimming, due to limitations in current and voltage regulation methods, leading to inefficiencies in power delivery and light output.
Innovation Solution
A method and device for controlling LED light sources using a combination of normal and burst modes, where the load current is regulated to achieve target intensities by adjusting average and peak current values, utilizing a load regulation circuit with a control circuit to manage duty cycles and feedback loops for precise power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional current or voltage regulation methods are used for LED dimming, then the LED light source can be controlled to different intensities, but power delivery efficiency deteriorates and energy loss increases
Solution Approach 1:
The patent employs burst mode periodic action by switching the LED driver between active and inactive states in cyclic bursts. During active periods, the driver delivers full power to maintain optimal efficiency; during inactive periods, power delivery is suspended. This periodic operation enables dimming while preserving peak efficiency during active cycles, avoiding the continuous energy loss associated with conventional dimming methods that operate at reduced power levels.
2Illumination intensity
If conventional dimming techniques are used, then light output can be reduced, but control precision deteriorates especially at low intensity levels
Solution Approach 1:
The system dynamically adapts its operating mode based on the desired light output level. At higher intensity levels, the system operates in continuous mode with precise PWM control. When dimming to lower intensities, it transitions to burst mode where the ratio of active to inactive periods is dynamically adjusted. This dynamic adaptation allows precise control across the full intensity range by selecting the most appropriate control mechanism for each operating level.
Solution Approach 2:
The patent incorporates feedback mechanisms that monitor the actual light output and adjust the burst duty cycle accordingly. By measuring the perceived brightness and comparing it to the target intensity, the control system can precisely regulate the ratio of active to inactive periods in burst mode, ensuring accurate dimming control even at low intensity levels where conventional methods struggle.
3Device complexity
If simple regulation circuits are used, then device complexity is reduced, but the ability to manage wide intensity ranges deteriorates
Solution Approach 1:
The patent segments the dimming range into two distinct operating zones: a higher intensity range handled by continuous PWM control and a lower intensity range handled by burst mode control. Each segment uses a specialized control strategy optimized for its range. This segmentation allows the system to achieve wide intensity range capability without requiring a single complex circuit that would need to handle all operating conditions, thereby maintaining relative simplicity while expanding versatility.
Data Source
AI summary
A method for controlling an amount of power delivered to an electrical load may include controlling an average magnitude of a load current towards a target load current that ranges from a maximum-rated current to a minimum-rated current in a normal mode and controlling the average magnitude of the load current below the minimum-rated current in a burst mode. The burst mode may include at least one burst-mode period that comprises a first time period associated with an active state and a second time period associated with an inactive state. During the burst mode, the method may include regulating a peak magnitude of the load current towards the minimum-rated current during the active state and stopping the generation of at least one drive signal during the inactive state to control the average magnitude of the load current to be less than the minimum-rated current.