Primary Side Ripple Cancellation LED Driver
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Solution Overview
Problem
Existing AC to DC power supplies face challenges in achieving high power factor and eliminating low frequency ripple, particularly in LED lighting applications, where ripple leads to visible flickering, and current solutions either compromise efficiency or increase component costs.
Innovation Solution
The implementation of a primary side controlled isolated ripple cancellation converter that senses and cancels AC voltage or current ripples, either in series or parallel, to provide substantially ripple-free DC output power, using a flyback or isolated boost converter topology, thereby reducing design complexity and component costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If critical conduction mode is used to achieve power factor correction, then power factor is improved, but output voltage ripple increases causing visible flickering
Solution Approach 1:
The patent extracts the harmful second harmonic ripple component from the output voltage and processes it separately through a dedicated ripple cancellation converter, while the main converter continues to provide power factor correction using critical conduction mode.
Solution Approach 2:
The power conversion function is segmented into two independent converters: a main converter for power factor correction and a ripple cancellation converter for eliminating output ripple. This segmentation allows each converter to optimize its specific function without compromising the other.
2Object-generated harmful factors
If a two-stage LED driver is used to achieve flicker-free performance, then output ripple is reduced, but efficiency decreases and component cost increases
Solution Approach 1:
The ripple cancellation converter acts as an intermediary that processes only the ripple component rather than the full power, minimizing energy loss. The main converter handles the bulk power transfer efficiently, while the ripple converter handles only the small ripple cancellation task.
Solution Approach 2:
The ripple cancellation converter processes only the necessary ripple component (partial action) rather than the entire output signal, reducing the energy processing burden and maintaining high overall system efficiency.
3Object-generated harmful factors
If a two-stage LED driver is used to eliminate ripple, then flicker-free performance is achieved, but device complexity increases
Solution Approach 1:
The patent merges the control functions of both converters into a single integrated control system that operates from primary side sensing, unifying the control architecture and reducing the complexity associated with coordinating multiple independent control systems.
Solution Approach 2:
The primary side control system performs multiple functions simultaneously: it controls both the main converter for power factor correction and the ripple cancellation converter for ripple elimination, creating a universal control platform that manages both functions efficiently.
Data Source
AI summary
Described herein are methods and circuits for improving the performance of an AC to DC power supply. The methods and circuits achieve high power factor (PF) at the AC side and at the same time, reduce or substantially eliminate ripple in the DC output power. The methods and circuits provide an isolated topology including primary side voltage and current sensing and primary side ripple cancellation control. The methods and circuits may be used in any application where high power factor and/or low output ripple are required. In particular, the methods and circuits may be used in DC lighting applications, such as in light emitting diode (LED) lighting, wherein suppression of low frequency ripple in the output power eliminates visible flickering.