LED Driver Circuit Using Feedback Inductor for Constant Current
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Solution Overview
Problem
Existing driver circuits for LED lighting are costly and complex, making them unsuitable for mass-market applications, and they often fail to provide a flicker-free, constant current to LEDs, which can lead to damage due to voltage variations.
Innovation Solution
A self-driving switch-mode driver circuit with a storage inductor and feedback inductor that uses feedback voltage to control inductor current and compensate for input and output voltage variations, maintaining a constant average current to the LED without the need for elaborate additional circuitry or voltage sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If elaborate circuit designs such as switching mode power supplies are used to provide constant current to LEDs, then the light output becomes substantially flicker-free and constant, but the circuit complexity and cost increase significantly
Solution Approach 1:
The patent combines the feedback inductor serving dual purposes: it provides feedback voltage for controlling the inductor current through the storage inductor, and simultaneously compensates for variations in input and output voltage. This merging of functions reduces the need for separate voltage sensing circuitry and simplifies the overall circuit design while maintaining constant current stability
Solution Approach 2:
The feedback inductor is designed to perform multiple functions: it generates feedback voltage for current control, detects input voltage variations, and compensates for output voltage variations. This multi-functionality eliminates the need for elaborate additional circuitry or dedicated voltage sensors, reducing circuit complexity while maintaining reliable constant current operation
2Reliability
If additional circuitry or voltage sensors are added to compensate for voltage variations, then the constant current stability improves, but the cost and circuit complexity increase
Solution Approach 1:
The feedback inductor serves itself to detect and compensate for voltage variations without requiring external voltage sensors or additional compensation circuitry. The feedback voltage generated by the inductor naturally reflects input and output voltage variations, which are then used directly to adjust the switching duty cycle and maintain constant current, making the system self-sufficient
3Device complexity
If simple driver circuits are used to reduce cost, then the circuit complexity decreases, but the ability to provide flicker-free constant current under voltage variations is compromised
Solution Approach 1:
The patent employs feedback control using the feedback inductor to continuously monitor the inductor current and adjust the switching duty cycle accordingly. This feedback mechanism, combined with the ability to detect voltage variations through the same feedback voltage, ensures constant current operation under varying input and output voltage conditions while maintaining a simple circuit structure
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 provides a cost-efficient, high-quality, flicker-free light output by maintaining a substantially constant average current to the LED, even with variations in input and output voltage, thus extending the LED's lifespan and reducing installation and replacement costs.
Implementation Method 1
a feedback inductor, inductively coupled to said storage inductor to provide a feedback voltage, corresponding to the variation of the inductor current through said storage inductor during operation
Data Source
AI summary
A driver circuit (1) for operating at least one load, such as a LED unit (7) is provided, comprising a switching controller (5) configured to at least control a switching device (13) between the discharging and charging mode of a storage inductor, in dependence on the inductor current (Is) and to control a duty cycle of the switching operation in dependence on at least one compensation signal, the compensation signal corresponding to either the input (VIN) voltage or the output voltage (VOUT), so that in case of a variation of the input (VIN) or output voltage (VOUT), the average output current, provided to the load, is maintained substantially constant.