LED Driving Circuit Current Sensing via Magnetic Induction
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Solution Overview
Problem
Existing LED driving circuits face challenges in achieving cost-effective and feasible current sensing for LED lighting applications, particularly in isolated and non-isolated topologies, where direct sensing of average current is hindered by isolation or high DC voltage, leading to the need for expensive optocouplers or impractical sensing methods.
Innovation Solution
A control circuit with a switching circuit, sensing circuit, estimation circuit, amplifying circuit, comparing circuit, and zero-cross detection circuit that regulates the average current flowing through LEDs by processing switching currents and providing feedback signals to control the switching of a switch on and off, allowing for effective current regulation without direct coupling between isolated circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolated topology is used with a transformer to isolate primary and secondary circuits, then circuit isolation and safety are improved, but the cost increases due to the need for expensive optocouplers for feedback signaling
Solution Approach 1:
The patent introduces an intermediary magnetic coupling mechanism through the transformer's magnetic field to transfer feedback information from the secondary circuit to the primary circuit without requiring direct electrical isolation components like optocouplers. The feedback signal modulates the transformer's magnetic field, enabling communication across the isolation barrier through magnetic induction rather than optical coupling.
Solution Approach 2:
The patent replaces the optical feedback system (optocoupler) with a magnetic field-based feedback system. Instead of using light to transmit feedback signals across the isolation barrier, the system uses magnetic field modulation and induction to achieve the same feedback function, thereby eliminating the need for expensive optocoupler components.
2Device complexity
If a non-isolated topology is used to eliminate the transformer, then cost and complexity are reduced, but direct current sensing becomes infeasible due to high DC voltage across the LEDs
Solution Approach 1:
The patent introduces an intermediary inductive element that couples the high-voltage LED circuit to the low-voltage control circuit. This intermediary enables indirect current sensing by transforming the high-voltage current information into a measurable low-voltage signal through magnetic induction, avoiding direct voltage exposure in the sensing circuit.
Solution Approach 2:
The patent changes the voltage parameter level for sensing purposes. Instead of measuring current directly at the high DC voltage level across the LEDs, the system transforms the measurement to occur at a lower, safer voltage level through the inductive coupling mechanism, making the sensing operation feasible and safe.
3Measurement precision
If direct current sensing is attempted in high voltage circuits, then measurement accuracy may be improved, but safety and feasibility deteriorate due to exposure to high DC voltage
Solution Approach 1:
The patent uses an inductive element as an intermediary to transfer current information from the high-voltage circuit to the low-voltage sensing circuit. This intermediary enables accurate current measurement while keeping the sensing circuit isolated from harmful high-voltage exposure through magnetic coupling.
Solution Approach 2:
The patent replaces direct electrical contact sensing with indirect magnetic field-based sensing. Instead of placing sensing components directly in the high-voltage current path, the system uses magnetic induction to capture current information at a safe distance, eliminating high-voltage exposure risks while maintaining measurement 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 enables cost-effective and efficient regulation of average current through LEDs in both isolated and non-isolated topologies, eliminating the need for expensive optocouplers and allowing for precise control of LED current, thereby improving the overall efficiency and cost-effectiveness of LED driving circuits.
Implementation Method 1
a sensing circuit coupled between the at least one switch and a logic ground, wherein the sensing circuit is configured to sense a switching current flowing through the at least one switch
Implementation Method 2
a switching circuit comprising at least one switch and an inductive element, wherein the switching circuit is configured to receive a DC voltage signal for driving a LED
Data Source
AI summary
A LED driving circuit, a control circuit and associated current sensing circuit. The control circuit has a sensing circuit, an estimation circuit, an amplifying circuit, a comparing circuit, a zero-cross detection circuit and a logic circuit. The sensing circuit is configured to sense a switching current flowing through at least one switch of a switching circuit to provide a first sensing signal. The estimation circuit is configured to process the first sensing signal to provide a feedback signal, wherein the feedback signal is indicative of a average current signal flowing through a LED. An average current flowing through the LED is regulated by sensing a switching current flowing through at least one switch.