Switched-Capacitor Isolated LED Driver Circuit
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Solution Overview
Problem
Existing LED driver circuits face challenges in achieving high electrical conversion efficiency, power factor, and thermal management while maintaining safety and reliability, particularly in compact LED lamp designs, where space is limited and thermal conductivity is compromised due to the need for galvanic isolation from AC mains.
Innovation Solution
A switched-capacitor galvanically isolated LED driver circuit that provides electrical conversion and current regulation, offering galvanic isolation options to enable close thermal contact between LEDs and heat sinks, while reducing the need for large transformers and electrolytic capacitors, thus enhancing efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal heat sink is used to maximize thermal conductivity, then thermal management is improved, but galvanic isolation from AC mains is compromised creating a safety hazard
Solution Approach 1:
The patent introduces a non-conductive thermal interface material as an intermediary between the metal heat sink and the LED module. This material allows thermal energy to pass through while blocking electrical conduction, thus maintaining both thermal management effectiveness and galvanic isolation safety
Solution Approach 2:
The thermal management system is segmented into distinct functional layers: a metal heat sink for thermal conduction, a non-conductive interface layer for electrical isolation, and an LED module for light generation. This segmentation allows each component to optimize its primary function without compromising safety
2Reliability
If a transformer is used to provide galvanic isolation, then safety isolation is improved, but circuit size and cost significantly increase
Solution Approach 1:
The patent replaces the traditional electromagnetic transformer (mechanical/electromagnetic system) with a capacitive isolation circuit (electrical field system). This substitution achieves galvanic isolation through capacitive coupling, eliminating the need for bulky transformer components while maintaining safety isolation
Solution Approach 2:
The isolation mechanism is changed from low-frequency electromagnetic transformation to high-frequency capacitive coupling. By operating at higher switching frequencies, the isolation circuit achieves the same isolation effect with much smaller component values, reducing overall circuit size
3Quantity of substance
If bulk electrolytic capacitance is used for energy storage, then energy storage capacity is improved, but lifetime and reliability deteriorate while circuit space is consumed
Solution Approach 1:
The patent replaces long-lived but bulky electrolytic capacitors with shorter-lived but compact solid-state capacitors. The solid-state capacitors, while having shorter theoretical lifetimes, provide sufficient reliability for the application while occupying minimal space and enabling the elimination of large electrolytic capacitor components
Solution Approach 2:
The switched-capacitor circuit performs multiple functions simultaneously: energy storage, voltage regulation, and galvanic isolation. By integrating these functions into a single circuit topology, the patent eliminates the need for separate bulk electrolytic capacitors, inductors, and isolation transformers
4Volume of moving object
If circuit components are reduced for compact design, then space efficiency is improved, but electrical conversion efficiency and power factor may deteriorate
Solution Approach 1:
The patent merges the functions of power factor correction, voltage regulation, and galvanic isolation into a single switched-capacitor circuit. By combining these functions, the circuit achieves high efficiency and power factor without requiring separate large components, thus maintaining compact size while optimizing electrical 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 achieves high efficiency and reliability by eliminating large transformers, reducing electrolytic capacitors, and providing effective thermal management, enabling efficient LED lamp operation with improved power factor and extended lifespan.
Implementation Method 1
A switched-capacitor galvanically isolated LED driver circuit which provides electrical conversion and current regulation, offering galvanic isolation options to enable close thermal contact between LEDs and heat sinks
Implementation Method 2
The heat produced by an LED is not directly convected from the front of the LED chip, but instead must be conducted through the back-side of the chip. It is critical to minimize the total thermal resistance from junction to ambient air toward providing adequate cooling of the LED
Implementation Method 3
light emitting diode (LED) lamps
Data Source
AI summary
A switched-capacitor voltage converter which is particularly well-suited for receiving a line voltage from which to drive current through a series of light emitting diodes (LEDs). Input voltage is rectified in a multi-level rectifier network having switched capacitors in an ascending-bank configuration for passing voltages in uniform steps between zero volts up to full received voltage VDC. A regulator section, operating on VDC, comprises switched-capacitor stages of H-bridge switching and flying capacitors. A current controlled oscillator drives the states of the switched-capacitor stages and changes its frequency to maintain a constant current to the load. Embodiments are described for isolating the load from the mains, utilizing an LC tank circuit or a multi-primary-winding transformer.