Primary Side Regulation LED Driver Circuit Simplification
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Solution Overview
Problem
Existing LED driving circuits, particularly those using fly-back converters, are complex, costly, and difficult to miniaturize due to the need for secondary side control circuits and opto couplers, which complicates constant current and voltage control and stability.
Innovation Solution
A primary side regulation method that simplifies the circuit by removing secondary side control circuits and opto couplers, using a transforming unit with an inductor to store and transfer energy and a control unit that calculates and controls secondary side average current based on primary side current and voltage, allowing for constant current control without secondary side feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fly-back converter is used for LED driving, then constant current and voltage control can be achieved, but the circuit structure becomes complicated and costly due to the need for secondary side control circuits and opto couplers
Solution Approach 1:
The patent extracts and removes the secondary side control circuit and opto coupler from the fly-back converter, retaining only the essential primary side components. This extraction eliminates the complicated feedback path while maintaining constant current control capability through direct primary side measurement of the LED current.
Solution Approach 2:
The patent implements self-service by using the LED current itself to generate the feedback signal through a sense resistor, eliminating the need for external opto couplers and secondary side control circuits. The system serves itself by using its own operating parameters for control.
2Reliability
If a fly-back converter with secondary side control is used, then stable LED operation is achieved, but the cost increases due to expensive opto couplers and additional control circuits
Solution Approach 1:
The patent replaces expensive opto couplers with a simple sense resistor that can be easily manufactured and replaced. The sense resistor is a basic electronic component with minimal cost, eliminating the need for expensive optical isolation components while maintaining control functionality.
Solution Approach 2:
By removing the expensive opto coupler and secondary side control circuit, the patent significantly reduces the bill of materials cost while maintaining LED operation stability through primary side current sensing and control.
3Reliability
If a fly-back converter with multiple peripheral elements is used, then protection against overvoltage is achieved, but miniaturization becomes difficult due to the large number of components
Solution Approach 1:
The patent extracts and removes multiple peripheral elements including opto couplers, secondary control circuits, and associated components, significantly reducing the overall circuit footprint and enabling miniaturization while maintaining essential protection functions through simplified primary side control.
4Speed
If peak current is used for feedback in primary side regulation, then the control speed increases, but the stability deteriorates because peak current is a dynamic value that changes instantly
Solution Approach 1:
The patent applies preliminary action by measuring and averaging the current over the complete switching cycle before using it for control decisions. This preliminary processing of the current signal ensures that the control system responds to stable average values rather than transient peak values, maintaining both speed and stability.
Solution Approach 2:
The patent changes the parameter used for feedback from peak current to average current, transforming the control variable from a dynamic instantaneous value to a stable cyclic average value. This parameter change maintains control responsiveness while eliminating the instability caused by peak current variations.
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 approach simplifies the circuit structure, reduces costs, and achieves more stable and precise constant-current control compared to peak current-based methods, improving efficiency and stability for LED operation.
Implementation Method 1
a transforming unit having a transformer for transforming the magnitude of an input voltage output from the first rectifying unit and an inductor connected to a primary side of the transformer in parallel, the transforming unit storing energy in the inductor when the switching element turns on and transferring the energy stored in the inductor to a secondary side when the switching element turns off
Data Source
AI summary
A light driving apparatus includes a first rectifying unit for receiving AC power and rectifying the AC power into DC, a switching element controlled to turn on or off by a control signal, a transforming unit having a transformer and an inductor connected to a primary side of the transformer in parallel, a second rectifying unit for rectifying a secondary side output of the transforming unit and supplying an output voltage thereof to a LED unit, and a control unit provided in the primary side to give a constant-current control function so that a secondary side output is maintained consistently. According to the present disclosure, it is possible to simplify the circuit structure of the secondary side and improve the efficiency by controlling the secondary side current at the primary side without secondary side feedback information.