LED Driver Circuit Using Primary Side Regulation to Reduce Flicker
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Solution Overview
Problem
Conventional LED driver circuits with single-stage flyback architecture suffer from high ripple voltage and flickering issues due to non-constant current output, which can be mitigated but at the cost of increased capacitance, power factor reduction, and higher component costs, especially when using optocoupler feedback for regulation.
Innovation Solution
A driver circuit employing a two-stage isolation transformer and primary side regulating architecture, eliminating the need for optocoupler feedback control, utilizes a transformer with input, auxiliary, driving, and dimming coils to maintain constant input voltage and output current, effectively reducing LED flickers when a PWM dimming signal of 1V-10V is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage flyback LED driver circuit is used, then the circuit structure is simple, but the ripple voltage is high and LED flickers occur
Solution Approach 1:
The patent divides the single-stage flyback circuit into two separate stages: a primary side flyback circuit and a secondary side LED driving circuit. This segmentation allows each stage to be optimized independently - the primary side for power conversion and the secondary side for constant current regulation, thereby reducing ripple voltage and eliminating LED flickers while maintaining reasonable circuit complexity.
2Object-generated harmful factors
If the capacitance value of the buffer capacitor is increased to reduce LED flickers, then LED flickers are improved, but the power factor decreases and component cost increases
Solution Approach 1:
The patent extracts the LED current regulation function from the primary side power conversion circuit and implements it independently on the secondary side using a dedicated constant current control circuit. This extraction eliminates the need for large buffer capacitors to suppress flickers, as the secondary side circuit directly regulates the LED current, thereby maintaining high power factor while eliminating LED flickers.
3Object-generated harmful factors
If optocoupler feedback is used to regulate current and eliminate LED flickers, then LED flickers are improved, but the circuit becomes more complicated and component cost increases
Solution Approach 1:
The patent implements self-service regulation where the secondary side circuit autonomously regulates the LED current based on direct sensing of the LED current itself, without requiring feedback from the primary side through optocouplers. The secondary side controller directly adjusts the switching duty cycle to maintain constant LED current, achieving flicker elimination while keeping the circuit simple and cost-effective.
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 simplifies the circuit design, reduces component costs, and improves overall efficiency by maintaining constant voltage and current output, eliminating LED flickers while maintaining a better power factor, as demonstrated by waveform diagrams and performance analysis.
Implementation Method 1
When the power is turned on, electric energy is converted into magnetic energy stored in the transformer, and when the power is turned off, the magnetic energy in the transformer is converted into electric energy which is discharged to a secondary side
Data Source
AI summary
A driver circuit adopting a primary side regulating architecture and an isolation transformer for improving LED flickers includes a transformer, a primary side regulating module, a feedback portion, a driving module and a dimming portion. The transformer includes an input coil, an auxiliary coil, a driving coil, and a dimming coil. The primary side regulating module is electrically coupled to the input coil; the feedback portion is electrically coupled to the auxiliary coil and the primary side regulating module; the driving module is electrically coupled to the driving coil; the dimming portion is electrically coupled to the dimming coil and the driving module. When a dimming signal inputted to the dimming portion has a voltage of 1V-10V, and the driver circuit is applied to a panel light, the LED flicker is improved effectively.