LED Constant Current Driver Circuit with Capacitor Feedback
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Solution Overview
Problem
Conventional LED driving circuits face challenges in maintaining a constant current due to propagation delays in signal transmission, leading to potential LED damage from excessive current, especially when operating frequency varies.
Innovation Solution
A constant current driving circuit comprising a control unit, buck converter, and compensation unit, where the compensation unit adjusts the compensation signal based on input power and cross-voltage variations to maintain a fixed current through the LED, incorporating components like compensation resistors, filter resistors, and capacitors to stabilize the current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a control signal is used to turn on/off a switch coupled to the LED, then the LED can be driven, but propagation delay causes the switch cannot be turned off immediately when abnormal current is detected
Solution Approach 1:
The patent applies preliminary action by using a capacitor coupled between the LED string and ground to immediately respond to current changes. When abnormal current occurs, the capacitor voltage changes instantly, providing immediate feedback to the control unit without waiting for signal transmission through the control chip, thus eliminating propagation delay and enabling immediate switch turn-off for LED protection
Solution Approach 2:
The patent implements feedback by coupling the capacitor between the LED string and ground, creating a direct feedback path that monitors current changes in real-time. The control unit receives feedback through the capacitor voltage changes, allowing immediate adjustment of the switch state without delay, thereby improving both response speed and LED protection capability
2Adaptability or versatility
If the operating frequency of the LED is varied, then the LED can adapt to different applications, but the constant current driving effect cannot be achieved
Solution Approach 1:
The patent applies dynamics by making the feedback mechanism adaptive through the capacitor-based system. The control unit dynamically adjusts the switch timing based on real-time capacitor voltage changes, which automatically compensate for frequency variations. This dynamic feedback ensures that the constant current control remains effective regardless of operating frequency changes, enabling both adaptability and reliable constant current driving
Data Source
AI summary
A constant current driving circuit of a light emitting diode (LED) including a control unit, a buck converter, and a compensation unit is provided. The control unit has an input terminal and an output terminal, and outputs a control signal through the output terminal. The buck converter is coupled to an input power, and is coupled between the output terminal of the control unit and an LED string. The compensation unit is coupled between the LED string and the input terminal of the control unit. The control unit receives a compensation signal of the compensation unit through the input terminal. Besides, a lighting apparatus is also provided.