Secondary-Side Bucking Flyback Converter for LED Current Stabilization
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Solution Overview
Problem
Traditional power converters for LED lamps suffer from low load adjustment precision, strobe issues at 120 Hz frequency, electromagnetic interference (EMI), and large ripple of operating current, along with complex and costly circuit architectures that rely on optical couplers for feedback, which are prone to instability and damage.
Innovation Solution
A secondary-side bucking and current-stabilizing flyback power converter with a dual-stage isolated circuit architecture that uses a primary side flyback circuit for voltage stabilization and a secondary side bucking circuit to maintain constant output current without optical couplers, employing a current stabilizing coil and sensing elements to regulate the duty cycle and reduce ripple amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical couplers are used for feedback control in the circuit architecture, then electrical isolation and secondary electric signal feedback control are achieved, but the circuit becomes complicated, expensive, and the optical coupler performance becomes unstable under temperature change or ageing
Solution Approach 1:
The patent removes the optical coupler from the feedback control circuit, extracting the problematic component that caused instability and complexity. The feedback function is achieved through alternative means (resistive voltage division and direct electrical connection) that eliminate the optical coupler's reliability issues under temperature变化和ageing
Solution Approach 2:
The patent creates a simplified copy of the feedback function using passive components (resistors) instead of the complex optical coupler. The voltage feedback is achieved through resistive voltage division that replicates the isolation and feedback control functions without requiring optical components
2Device complexity
If a single-stage flyback circuit architecture is used, then the circuit is simple and easy to assemble, but the load adjustment precision is low and large current ripple occurs
Solution Approach 1:
The patent divides the power conversion function into two separate stages: a flyback circuit for voltage conversion and isolation, and a buck circuit for precise current regulation. This segmentation allows each stage to optimize for its specific function, achieving both high precision current control and circuit simplicity
3Productivity
If traditional PWM control method is used in single-stage flyback converter, then the circuit operates efficiently, but strobe problems occur at 120 Hz frequency and EMI issues arise
Solution Approach 1:
The patent separates the high-frequency switching function (flyback stage) from the low-frequency current regulation function (buck stage). This segmentation allows the PWM control to operate at optimal high frequency for efficiency while the second stage filters out the harmful 120 Hz strobe effects and EMI
Solution Approach 2:
The patent introduces an intermediate buck circuit stage between the flyback converter and the LED load. This intermediary stage acts as a buffer that filters out harmful frequency components and EMI while maintaining the efficiency benefits of the original PWM-controlled flyback stage
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 achieves a non-strobe effect, improves illumination quality, reduces eye fatigue, and lowers component costs by using existing electronic components, maintaining constant output current with reduced ripple amplitude and eliminating the need for optical couplers, thus enhancing industrial and economic viability.
Implementation Method 1
After the power converter uses the transformer 10 to convert the input voltage rectified and outputted by the bridge rectifier 11
Implementation Method 2
the secondary coil 102 and the output inductor 13 converts and forms an operating voltage required by the LEDs 2
Data Source
AI summary
A secondary-side bucking and current-stabilizing flyback power converter adopts a dual-stage isolated circuit architecture and outputs a constant output current to drive a low-power LED module, and its primary stage adopts a flyback circuit architecture with a primary regulated voltage, and its secondary stage adopts of a buck circuit architecture of the current stabilizer, so that after the primary stage converts the constant voltage, the current stabilizer senses the load effect of the output current at the LED module to regulate the output cycle and maintain the total output of the output current constant and reduce the ripple amplitude, so as to achieve a non-strobe output result and improve the illumination effect of the LED module.