Non-Isolated Buck LED Driver With PWM Feedback Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LED lighting drivers, particularly those using flyback topology, are costly and bulky, making them unsuitable for compact applications like CFL lamp holders, where a non-isolated solution with reduced component count and improved price/performance ratio is needed.
Innovation Solution
A non-isolated LED driver based on buck topology with a low-cost PWM control circuit and emitter-switched architecture, incorporating a capacitor for output voltage ripple filtering and an output voltage/current control circuit using PNP and NPN transistors with zener diodes for error signal amplification, providing better line/load regulation and short circuit protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flyback topology is used for LED driver, then isolation and constant output control are achieved, but device complexity and cost increase
Solution Approach 1:
The patent removes the isolation transformer and optical coupling elements from the flyback topology, extracting only the essential buck converter components while maintaining the constant output control function through direct feedback to the PWM controller
Solution Approach 2:
The patent replaces expensive isolation components with simpler, cheaper non-isolated circuitry that achieves the same functional goals through alternative design approaches
2Reliability
If flyback SMPS circuit is used, then constant output current or voltage is achieved, but system size increases
Solution Approach 1:
The patent extracts the essential voltage regulation function from the bulky flyback transformer assembly, implementing it through a compact buck converter topology with direct feedback control that maintains constant output without requiring large isolation components
Solution Approach 2:
The patent combines the voltage sensing, error amplification, and feedback control functions into an integrated circuit that directly monitors and regulates the output voltage, eliminating the need for separate isolation and control components
3Reliability
If isolation is implemented in LED driver, then safety is improved, but cost and complexity increase
Solution Approach 1:
The patent removes the isolation barrier while implementing safety through alternative means such as grounded feedback circuits and protected switching configurations that provide adequate protection without requiring galvanic isolation
Solution Approach 2:
The patent uses the PCB ground plane and circuit reference potentials as intermediaries to provide safety references and protection without requiring physical isolation barriers
Data Source
AI summary
The present invention mainly discloses low power non-isolated driver that can be used for LED lighting and other non-isolated power supply appliance, in which the input side is connected to an AC or DC input, a PWM control circuit is connected to the buck converter switch, a capacitor filters the output voltage ripple and an output voltage/current control circuit provides feedback signal to the PWM control circuit. The present invention has such features of less component number, low total cost, high reliability, and better line/load regulation.