AC LED Array Switching Circuit for Extended On-Time
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Solution Overview
Problem
Conventional LED lighting systems powered by AC sources face inefficiencies in light output due to frequent switching off at double the line frequency, leading to uneven usage and potential differences in LED string lifetimes, as they are not optimized to adapt to varying voltage levels effectively.
Innovation Solution
The system employs solid-state switches to dynamically change the connection configuration of LEDs between parallel and series based on the rectified AC voltage level, using a voltage detector to manage the switching between two current drivers, ensuring optimal power utilization and extended light-on time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LEDs are driven directly by AC power source with fixed parallel connection, then circuit design is simple, but LED on-time is limited to about 40% and light output efficiency is low
Solution Approach 1:
The patent applies dynamics by making the LED array configuration switchable between parallel and series connections based on real-time voltage detection. The system dynamically adjusts the connection mode of LED strings (first, second, and third LED strings) according to the instantaneous AC voltage level, allowing the LED on-time to exceed 90% of the cycle while maintaining circuit simplicity through automated switching control
Solution Approach 2:
The patent changes the electrical connection parameter of the LED array by switching between parallel and series configurations. When voltage is high, LED strings are connected in series to withstand higher voltage and extend on-time; when voltage is low, they are connected in parallel to ensure proper current flow. This parameter change enables the LED on-time to reach over 90% while maintaining simple circuit design
2Device complexity
If LED strings are switched on and off at double line frequency, then current regulation is simplified, but uneven usage causes different lifetimes for LED strings
Solution Approach 1:
The patent implements feedback by continuously monitoring the instantaneous AC voltage level and using this information to control the switching of LED string configurations. The voltage detection circuit provides real-time feedback to the switching control circuit, which adjusts the connection mode of LED strings accordingly. This feedback mechanism ensures that all LED strings operate under appropriate conditions, extending their lifetimes uniformly while maintaining simplified current regulation
Solution Approach 2:
The system dynamically adjusts which LED strings are active and in what configuration based on real-time voltage conditions. During high voltage portions of the AC cycle, more LED strings are activated in series; during low voltage portions, fewer strings operate in parallel. This dynamic adaptation ensures even usage across all LED strings, improving reliability and lifetime uniformity while keeping current regulation simple
3Ease of manufacture
If fixed parallel connection is used for LED strings, then manufacturing is easier, but power utilization efficiency is low due to frequent switching off
Solution Approach 1:
The patent makes the LED array configuration dynamic by switching between parallel and series connections based on voltage level. This dynamic reconfiguration allows the system to maximize power utilization efficiency by ensuring LEDs operate during the majority of the AC cycle (over 90% on-time) rather than being frequently switched off, while maintaining ease of manufacture through standardized LED string modules that can be configured in different ways
4Loss of energy
If series connection is used for LED strings, then power utilization increases, but circuit complexity increases due to switching control requirements
Solution Approach 1:
The patent applies self-service by using the AC voltage itself as the control signal for switching. The instantaneous voltage level directly controls the switching action through voltage detection and comparison circuits, eliminating the need for separate complex control signals or microprocessors. This self-service approach maximizes power utilization efficiency through series/parallel switching while keeping the control circuit relatively simple and integrated into the power supply path
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
This approach significantly increases the LED on-time to over 90% by optimizing power distribution across LED strings, reducing wear and tear differences and enhancing overall efficiency.
Implementation Method 1
a voltage detector for comparing the rectified voltage against the sum of the forward bias voltages of the pair of LEDs
Implementation Method 2
three solid state switches configured such that in a first state the pair of LEDs are connected in parallel to the rectified voltage and are driven by the first current driver, and in a second state the pair of LEDs are connected in series to the rectified voltage
Implementation Method 3
when source voltage 202 exceeds the forward voltage of LED string D1, LED string D1 conducts and emits light
Data Source
AI summary
An LED lighting circuit where the configuration of the connection of two or more LEDs are changed from parallel to series through the use of solid state switches depending on whether the voltage level from an AC source measured by a voltage detector exceeds the sum of the forward voltages of the LEDs. Also, a method of activating LEDs in an LED array lighting apparatus involving applying a rectified alternating current to two or more LEDs, each LED having a forward bias voltage; comparing the rectified alternating current to the sum of the forward bias voltages of the two or more LEDs; and changing the circuit configuration of the two or more LEDs between a parallel connection and a series connection with respect to the rectified alternating current depending on whether the rectified alternating current exceeds the sum of the forward bias voltages of the two or more LEDs.