SEPIC Power Supply Controller for LED Drivers
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Solution Overview
Problem
LED lamps require a power supply that addresses challenges such as power factor correction, longevity of components, electromagnetic compatibility, and operation with variable or AC/DC supplies, as existing buck converters often fail to meet these requirements due to energy storage components and electromagnetic interference.
Innovation Solution
A switched mode power supply using a single-ended primary inductor converter (SEPIC) with a controller that adjusts switching frequency and ON time based on monitored current and supply voltage, incorporating coupled inductors and a digital controller for feedback loop adjustments, ensuring high power factor and reduced electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a buck converter is used to reduce supply voltage for LED lamps, then voltage conversion is achieved, but power factor deteriorates due to energy storage components changing current waveform phase and shape
Solution Approach 1:
The patent implements dynamic control of the switching element where the switching frequency and duty cycle are continuously adjusted based on the instantaneous supply voltage and current. This dynamic operation allows the power supply to adapt to varying input conditions while maintaining a high power factor by ensuring current follows the voltage waveform, resolving the contradiction between voltage conversion and power factor maintenance.
Solution Approach 2:
The patent employs feedback control mechanisms where the controller monitors supply voltage and current, and adjusts switching parameters accordingly. This feedback loop enables the system to maintain optimal power factor by dynamically compensating for the effects of energy storage components, while simultaneously achieving the required voltage conversion for LED operation.
2Stability of the object's composition
If electrolytic capacitors are used for smoothing in buck converters, then voltage stabilization is improved, but device longevity deteriorates due to shorter capacitor lifetime compared to LEDs
Solution Approach 1:
The patent eliminates electrolytic capacitors from the circuit topology, replacing them with inductor-based energy storage elements that have significantly longer lifetimes. This design choice removes the limiting component that would determine overall system longevity, allowing the power supply to match or exceed the lifetime of LED lamps while maintaining adequate voltage stabilization through the switched-mode topology and control circuitry.
3Loss of energy
If switched mode power supply operates at high switching frequency, then power conversion efficiency is improved, but electromagnetic interference increases requiring suppression
Solution Approach 1:
The patent combines the functions of multiple inductors into a single integrated magnetic component with coupled windings. This merging approach reduces the number of discrete switching events and associated EMI-generating components, while maintaining the high-frequency operation needed for efficient power conversion. The coupled inductor structure also provides inherent EMI suppression through magnetic coupling between windings.
4Object-generated harmful factors
If power supply is designed for AC input only, then power factor correction is simplified, but adaptability deteriorates when DC input or variable voltage is required
Solution Approach 1:
The patent designs a universal power supply topology that can accept both AC and DC inputs through the same circuit architecture. The controller automatically detects input type and adjusts switching parameters accordingly, enabling the same hardware to achieve power factor correction for AC inputs while providing efficient voltage conversion for DC inputs. This multi-functional design maintains adaptability across different supply types without sacrificing power factor performance.
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 provides a power supply with improved power factor correction, extended component lifetime, reduced electromagnetic interference, and operation with both AC and DC sources, ensuring efficient and reliable power delivery to LED lamps.
Implementation Method 1
A switched mode power supply in the form of a single ended primary inductor converter (SEPIC) to convert an AC supply voltage, e.g. from a mains supply, to a DC voltage suitable for driving an LED lamp
Implementation Method 2
The inductors L1 and L2 are coupled in the form of a transformer
Data Source
AI summary
The invention concerns a method of controlling a switch in a switched mode power supply, and also a switched mode power supply as such. In one embodiment the supply is driven from an alternating current source. It provides a controlled output which may in principle be bucked or boosted. A switching frequency is controlled by monitoring current in the switched mode power supply and initiating a new switching cycle each time the monitored current falls below a switching threshold, which is variable. The switch is turned ON during each switching cycle for a chosen ON time. The switching threshold is determined bas ed upon the instantaneous supply voltage, Output power is monitored and the ON time is varied to adjust the p ower output toward a required value.