LED Control Circuit Bias Current Termination
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Solution Overview
Problem
The existing LED lighting systems using phase-cut dimming methods for controlling LED light sources experience increased power dissipation due to the need for a bias current, which is not efficiently managed, leading to inefficiencies in power usage.
Innovation Solution
An LED control circuit is configured to detect the current flowing through the LED light source and selectively form a bias current only when necessary, using a current regulator and a dummy load to minimize power dissipation by terminating the bias current when the LED is conducting, thus reducing power consumption independently of the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias current is continuously supplied to the adjustable triac dimmer, then the dimmer operates reliably, but the power dissipation of the LED lighting system increases
Solution Approach 1:
The patent applies periodic action by supplying the bias current only during specific periods when the LED is not conducting (during the off-state of the LED current cycle). The control circuit periodically enables the bias current to the dummy load during intervals when no LED current is flowing, and disables it when LED current is present. This periodic activation maintains dimmer reliability while minimizing continuous power dissipation.
2Ease of operation
If a control circuit continuously monitors and maintains bias current, then the LED current is properly controlled, but the system complexity and power consumption increase
Solution Approach 1:
The patent implements feedback by using the detected LED current signal to control the bias current supply. The control circuit monitors the LED current status and uses this feedback to automatically enable or disable the bias current to the dummy load. This feedback mechanism simplifies the control logic compared to continuous monitoring while ensuring proper operation - the bias current is automatically adjusted based on real-time LED current detection.
Solution Approach 2:
The patent extracts the bias current function from the main LED drive path and places it in a separate dummy load circuit. This separation allows the bias current to be independently controlled and supplied only when needed (when LED current is absent), without interfering with the main LED current control path. The extraction simplifies the overall control architecture by isolating the bias current management function.
Data Source
AI summary
In one embodiment, an LED control circuit is configured to form an LED current for operating an LED light source and configured to form a bias current for a dummy load. The LED control circuit is configured to terminate the bias current responsively to detecting the LED current.