Isolated LED Converter Current Sensing Across Wide Load Range
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Solution Overview
Problem
Isolated converters for LED loads face challenges in accurately sensing secondary side current over a wide current range, as optimizing components for high or low output currents leads to signal quality issues or power losses.
Innovation Solution
An isolated converter with a sensing circuit and control unit that adjusts electrical characteristics to dynamically optimize the measurement path for different output currents, using adjustable auxiliary windings and shunt resistors, and internal signal modifications to adapt the feedback signal ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the auxiliary winding or current sense transformer is optimized for high output currents, then power losses at high currents are reduced, but signal quality of the sense signal deteriorates at lower output currents
Solution Approach 1:
The patent applies the dynamics principle by making the measurement path adjustable rather than fixed. The converter can dynamically switch between different measurement paths depending on the operating current level. At high currents, one measurement path is used to minimize power losses, while at low currents, a different measurement path is activated to maintain signal quality. This dynamic adaptation resolves the contradiction between power efficiency and measurement precision across different operating conditions.
Solution Approach 2:
The patent segments the measurement functionality into multiple independent measurement paths. Instead of using a single auxiliary winding or current sense transformer optimized for one condition, the system divides the measurement function into separate paths, each optimized for specific current ranges. This segmentation allows the system to select the appropriate measurement path based on operating conditions, thereby resolving the contradiction between power losses and signal quality.
2Measurement precision
If the auxiliary winding or current sense transformer is optimized for low output currents, then signal quality of the sense signal is improved at lower output currents, but power losses increase at higher output currents
Solution Approach 1:
The system dynamically selects between different measurement paths based on the operating current level. When low currents are detected, the measurement path optimized for signal quality is activated. When high currents are detected, the system switches to a different measurement path that minimizes power losses. This dynamic switching capability resolves the contradiction between maintaining signal quality at low currents and minimizing power losses at high currents.
Solution Approach 2:
The patent changes the electrical parameters of the measurement path based on operating conditions. By adjusting which measurement path is active (changing parameters such as winding turns ratio, resistance, or coupling characteristics), the system optimizes performance for the current operating level. This parameter change allows the system to maintain signal quality at low currents while minimizing power losses at high currents.
3Device complexity
If a single measurement path is used for the feedback signal, then device complexity is reduced, but the converter cannot accurately sense current over a wide current range
Solution Approach 1:
The patent implements multi-functionality by providing multiple measurement paths that can be selectively activated. Each measurement path serves a specific function optimized for particular current ranges. The control unit universally manages these different paths, selecting the appropriate one based on operating conditions. This multi-functional approach allows accurate current sensing over a wide current range while keeping the overall device complexity manageable through intelligent control.
Solution Approach 2:
The system dynamically configures the measurement path based on operating requirements. Rather than using a single static measurement path, the system adapts its measurement configuration in real-time according to the current level. This dynamic adaptation enables accurate sensing across a wide current range while maintaining reasonable device complexity through controlled switching between predefined measurement paths.
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
Enables accurate and efficient current sensing across a wide range, improving signal quality at low currents and reducing power losses at high currents, while maintaining light flicker performance.
Implementation Method 1
a sensing circuit on a primary side of the isolation stage, which is magnetically coupled to a secondary side of the isolation stage
Data Source
AI summary
The invention relates to an isolated converter (100) for providing a current supply to an LED load, comprising: a galvanic isolation stage (101); a sensing circuit (103) on a primary side of the isolation stage (101), which is magnetically coupled to a secondary side of the isolation stage (101); wherein the sensing circuit (103) is configured to receive a feedback signal that is proportional to a secondary side current; and a control unit (105) configured to determine an output current of the converter (100) based on the feedback signal; wherein at least one electrical characteristic of the sensing circuit (103) and/or the control unit (105) is adjustable to convert the feedback signal from a first ratio to a second ratio to the secondary side current.