AC-Driven LED Ladder Circuit with Asymmetric Bridge Rectifier
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Solution Overview
Problem
Existing LED driving circuits require additional converters to operate with AC power, leading to inefficiencies, increased component count, and vulnerability to reverse voltage, which affects chip efficiency and reliability, especially for LEDs sensitive to ESD.
Innovation Solution
An AC-driven LED driving circuit with a ladder network configuration, where LED devices are arranged in specific sequences to form current loops driven in alternating voltage half cycles, optimizing the number of LEDs used and improving ESD characteristics by controlling the distribution of LED devices across branches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If additional converter circuits are used to convert AC power to DC power for driving LEDs, then LEDs can be driven at normal voltage, but the configuration becomes complicated, efficiency and reliability are reduced, and manufacturing costs and product size increase
Solution Approach 1:
The invention extracts and eliminates the additional converter circuit from the LED driving system. By using AC-driven LEDs directly connected through a bridge rectifier and capacitor network, the complex AC-to-DC conversion apparatus is removed, simplifying the overall configuration while maintaining the ability to operate at normal AC voltage.
Solution Approach 2:
The LED circuit is designed to self-regulate and operate directly from AC power without external conversion equipment. The bridge rectifier and capacitor network automatically perform the necessary voltage regulation and current control, allowing the LEDs to drive themselves from AC power sources.
2Ease of manufacture
If LEDs are arranged in reverse-parallel or bridge configuration to enable AC driving, then LEDs can be driven without additional converters, but only 50-60% of total LEDs emit light continuously, reducing chip efficiency
Solution Approach 1:
The LED array is segmented into multiple independent strings or groups, each with its own current path through the bridge rectifier network. This segmentation allows different LED groups to operate in different half-cycles or simultaneously, ensuring that a higher percentage of LEDs remain active and contributing to light output.
Solution Approach 2:
The invention employs an asymmetric bridge rectifier configuration with unequal arm arrangements, where different numbers of LEDs are placed in different branches. This asymmetric design optimizes the current distribution to maximize the number of actively emitting LEDs while maintaining balanced operation across the AC cycle.
3Illumination intensity
If more LEDs are used to compensate for low efficiency in reverse-parallel arrangement, then desired light output can be achieved, but the number of components and manufacturing complexity increase
Solution Approach 1:
The invention changes the electrical parameters and connection topology of the LED array, using a bridge rectifier configuration with specific capacitor networks to optimize current distribution. This parameter optimization allows achieving the desired illumination intensity with fewer LED components by maximizing the utilization of each LED's light output capability.
4Productivity
If chip efficiency is increased by optimizing LED arrangement, then fewer LEDs are needed for same light output, but reverse voltage exposure increases during non-driven half cycle, reducing reliability
Solution Approach 1:
The invention incorporates protective capacitor networks and voltage distribution circuits that beforehand cushion and limit the reverse voltage exposure to LEDs. The capacitor network is configured to maintain voltage balance and prevent excessive reverse bias during non-conducting half-cycles, protecting the LEDs from damage while maintaining high efficiency operation.
Solution Approach 2:
The bridge rectifier and capacitor network serve as intermediary elements between the AC power source and the LEDs. These intermediaries regulate and buffer the voltage transitions, protecting the LEDs from direct exposure to harmful reverse voltages while still enabling efficient AC-driven operation.
Data Source
AI summary
There is provided an LED driving circuit. The LED driving circuit according to an aspect of the invention may include: at least one ladder circuit including: (n−1) number (here, n is a positive integer satisfying n≧2) of first branches provided between first and second junction points, and connected in-line with each other by n number of first middle junction points, (n−1) number of second branches arranged in parallel with the first branches, and connected in-line with each other by n number of second middle junction points between the first and second junction points, and n number of middle branches connecting m-th first and second middle junction points to each other, wherein at least one LED device is disposed on each of the first, second, and middle branches. Here, the number of LED devices included in each of the first and second branches is greater than the number of LED devices included in each of the middle branches.