BiFRED LED Driver Primary Side Ripple Control
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Solution Overview
Problem
Existing BiFRED converters face challenges in controlling output current ripple without increasing cost or component count, particularly in achieving low frequency ripple below 4% while maintaining high power factor and low total harmonic distortion.
Innovation Solution
A primary side control mechanism is implemented using current sensing elements to adjust the switching element's on-time duration based on sensed boost and flyback currents, eliminating the need for secondary side isolation and allowing for low-cost, low-component-count circuitry to suppress output current ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a dual-stage topology (AC/DC Boost converter and DC/DC flyback converter) is used, then output current ripple can be reduced below 4%, but cost and component count increase due to duplication of high voltage switches and control circuits
Solution Approach 1:
The patent combines the Boost converter and Flyback converter into a single integrated BiFRED topology, merging two separate conversion stages into one unified circuit. This integration eliminates the need for duplicate high voltage switches and control circuits while maintaining the ability to reduce output current ripple below 4% through coordinated operation of the merged stages.
Solution Approach 2:
The BiFRED converter performs multiple functions within a single stage: it provides AC/DC conversion, DC/DC conversion, power factor correction, and output ripple reduction simultaneously. The circuit topology enables one system to fulfill roles that traditionally required separate dedicated circuits, thereby reducing overall component count while achieving the desired ripple performance.
2Object-generated harmful factors
If a very large output buffer capacitor is used, then output current ripple can be reduced, but cost and device size increase
Solution Approach 1:
The patent implements a control mechanism that monitors the output current and adjusts the switching duty cycle dynamically to maintain ripple below 4%. This feedback control enables the system to achieve low ripple performance without relying on oversized passive components like buffer capacitors, as the active control compensates for ripple variations in real-time.
Solution Approach 2:
The system dynamically adjusts operating parameters such as switching frequency and duty cycle to optimize ripple reduction. By changing these parameters adaptively, the converter achieves low output ripple without requiring a very large output buffer capacitor, thereby reducing both cost and component size.
3Device complexity
If single-stage driver architecture is used, then cost is reduced, but it becomes difficult to achieve low output current ripple
Solution Approach 1:
The patent merges Boost and Flyback conversion functions into a single integrated BiFRED stage, enabling single-stage operation that maintains simplicity and low cost while achieving effective ripple reduction through the coordinated action of the integrated circuit elements.
Solution Approach 2:
The BiFRED topology ensures continuous energy transfer and smooth current waveforms through its integrated architecture, where the Boost inductor and Flyback transformer work in continuous coordination. This continuous operation mode enables the single-stage converter to achieve low ripple performance without requiring complex multi-stage switching sequences.
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 effectively reduces output current ripple to below 4% while maintaining high power factor and low total harmonic distortion, achieving stable output current with a simplified and cost-effective converter circuit.
Implementation Method 1
a current sensing element in series with the energy storage device for sensing an output current from the boost portion when said switching element is switched off and a current discharged from the energy storage device when said switching element is switched on
Implementation Method 2
During the first state, the switch is conductive and the first inductor L1 is charged from rectified mains via the switch S1. The energy in the first inductor L1 is magnetic energy which is proportional to the inductor current.
Implementation Method 3
the second inductor L2 is the primary winding of a transformer T1 which has a secondary winding L3 connected to the second diode D2
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A boost integrated flyback (BiFRED) converter which has a current sensing element (R2) in series with the energy storage device (C1) of the converter for sensing a boost portion current and a discharging flyback portion current. A feedback circuit (54) processes the sensed current to derive a control signal which is then used for adjusting the time duration for which the switching element (S1) of the BiFRED converter is switched on based on the control signal. This arrangement makes use of primary side current sensing to modify standard on-time control so that the current ripple in the output can be suppressed.