Light Source Driving Apparatus Isolated Current Sensing Circuit
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Solution Overview
Problem
Conventional LED drive circuits face challenges in accurately controlling output current at low dimming levels due to low sampling signals and require two independent voltage sources for signal isolation, which complicates design and increases costs.
Innovation Solution
The proposed light source driving apparatus incorporates an isolated current sensing circuit for electromagnetic coupling, a dimming circuit that uses a single independent voltage source, and a feedback circuit to generate a feedback signal, allowing for accurate control of output current without the need for two isolated voltage sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional secondary side resistor sampling current control method is used, then the LED drive circuit can control LED brightness, but the sampling signal becomes too low at low dimming ratios making accurate constant current control impossible
Solution Approach 1:
The patent introduces an isolated current sensing circuit as an intermediary component that couples to the secondary side through electromagnetic coupling. This circuit samples the output current and generates a current sensing signal that is then transmitted to the primary side through the optical coupler, enabling accurate current measurement even at low dimming ratios without being constrained by resistor sampling limitations.
2Reliability
If two independent voltage sources are used for signal isolation, then signal isolation between primary and secondary sides is achieved, but device complexity and cost increase
Solution Approach 1:
The patent merges the functions of multiple voltage sources into a single independent voltage source. The isolated current sensing circuit and optical coupler provide the necessary signal isolation between primary and secondary sides, eliminating the need for two independent voltage sources while maintaining isolation reliability and reducing device complexity.
3Speed
If optical coupler with high response speed is used for three-in-one dimming, then complete dimming output signal is achieved, but device cost and complexity increase
Solution Approach 1:
The isolated current sensing circuit acts as an intermediary that performs current sampling and signal generation on the secondary side, then transmits the signal to the primary side through the optical coupler. This approach enables the use of a standard optical coupler rather than requiring a high-response-speed optical coupler, thereby reducing device complexity and cost while maintaining three-in-one dimming capability.
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
This solution achieves signal isolation and accurate control of output current at low dimming levels, reducing the need for additional isolation elements and voltage sources, thereby simplifying design and reducing costs while maintaining high resolution and dimming accuracy.
Implementation Method 1
The isolated current sensing circuit is coupled to the secondary side, and samples an output current of the light source driving apparatus by electromagnetic coupling to generate a current sensing signal
Data Source
AI summary
A light source driving apparatus including a primary side and a secondary side is provided. The light source driving apparatus includes an isolated current sensing circuit, a dimming circuit, an independent voltage source, and a feedback circuit. The isolated current sensing circuit is coupled to the secondary side, and samples an output current of the light source driving apparatus by electromagnetic coupling to generate a current sensing signal. The dimming circuit receives a dimming input signal, and provides a reference controlled-current signal according to the dimming input signal and based on an operating voltage. The independent voltage source is configured to generate the operating voltage. Based on the operating voltage, the feedback circuit provides a feedback signal according to the current sensing signal and the reference controlled-current signal for adjusting the output current of the light source driving apparatus.