LED Driver Shunt Circuit for Deep Dimming Stability
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Solution Overview
Problem
Existing lamp drivers face instability and performance issues when dimming LED lights to very low levels of intensity due to minimum load requirements, leading to problems like flickering, audible noise, or complete loss of light.
Innovation Solution
A dimming circuit with a shunt load that diverts current away from the LED when the driving current reaches a low intensity level, maintaining a minimum load to prevent these issues and ensuring stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If AC/DC power supply operates at very low current levels to achieve deep dimming, then light intensity is reduced, but instability and performance degradation occur due to minimum load requirements
Solution Approach 1:
A shunt circuit is introduced as an intermediary component between the LED and the power supply. This shunt circuit diverts a portion of the current away from the LED, allowing the power supply to maintain its minimum load requirement while the LED receives reduced current for deep dimming. The shunt acts as a mediator that resolves the conflict between maintaining driver stability and achieving low light intensity.
2Illumination intensity
If phase control is used to reduce average current for dimming, then light output is reduced, but flickering and audible noise occur at very low dimming levels
Solution Approach 1:
The shunt circuit serves as an intermediary that provides a stable current path, preventing the harmful effects of excessive phase control at very low dimming levels. By diverting current through the shunt, the circuit maintains adequate current flow to prevent flickering and reduce audible noise while still achieving the desired low light output through controlled current diversion.
3Reliability
If minimum load requirement is maintained to ensure driver performance, then current available for LED is reduced, but ability to dim to very low levels is limited
Solution Approach 1:
The current path is segmented into two separate paths: one through the LED and one through the shunt circuit. This segmentation allows independent control of current distribution. The power supply maintains its minimum load through the shunt path while the LED path receives the remaining current, enabling deep dimming capability without compromising driver performance. The total current is divided between these two segments according to dimming requirements.
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 minimizes instability and undesirable effects by maintaining a minimum load, allowing for precise control of LED light intensity down to very low levels without flickering or loss of light.
Implementation Method 1
a second current path connected to the first current path, wherein the second current path includes a shunt load and a dimming control circuit that causes current to flow in the shunt load and controls current flow through one of the first current path and the second current path
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A driver is connectable to an external power supply and configured to output a variable driving current for one or more loads, such as LEDs. A low intensity dimming module is operable to divert some or all of the driving current away from the LEDs when a user selects a very low level of light intensity so that the driver has a constant minimum load. The low intensity dimming module prevents performance issues that commonly affect drivers under light load conditions.