Bi-Level LED Power Supply Using Isolated PWM Dimming
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Solution Overview
Problem
Conventional bi-level dimming control methods for LED lighting systems face challenges in designing a cost-effective solution that can handle high input voltages and provide lower output brightness levels, especially considering lightning surge protection and the specifications of UL 1310 Class 2 for LED power supplies operating below 60 volts.
Innovation Solution
A bi-level dimming method and LED power supply design that incorporates a conversion circuit, a switch, and an oscillation circuit to adjust output voltage based on a dimming signal with a fixed frequency and duty cycle, received from an external detection switch, allowing for 100% and 30% brightness control of LED lamps by converting input voltage to 12 or 24 volts and using PWM technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the control port is connected to the input end (high voltage end) for dimming control, then the dimming control can be achieved, but the design complexity increases due to high input voltage, lightning surge protection requirements
Solution Approach 1:
The patent introduces an isolated control port that uses optical coupling as an intermediary between the high-voltage input side and the low-voltage control circuitry. The isolated control unit receives dimming signals through optically coupled isolation, preventing direct electrical connection and thus eliminating the need for complex lightning surge protection designs while maintaining dimming control functionality.
2Ease of operation
If a standard 0 to 10-volt dimming interface is used for bi-level dimming control, then the dimming function is achieved, but the design cost increases
Solution Approach 1:
The patent implements a self-service dimming control mechanism where the isolated control unit automatically recognizes and adapts to different dimming signal types (including 0-10V, PWM, and other common interfaces) without requiring additional external components or complex configuration. The system internally handles signal conditioning and processing, eliminating the need for expensive external dimming modules while maintaining full bi-level dimming functionality.
3Power
If the LED power supply operates at high voltage to provide sufficient power output, then the power delivery capability is improved, but the compliance with UL 1310 Class 2 specifications (below 60 volts) becomes difficult to achieve
Solution Approach 1:
The patent segments the power supply system into isolated high-voltage power conversion section and low-voltage output section. The isolated control unit manages the power conversion from high voltage input to low voltage output (12V or 24V), ensuring that the output side maintains UL 1310 Class 2 compliance (below 60 volts) while the input side can accept standard mains voltages. The optical isolation boundary clearly separates these two voltage domains.
4Loss of energy
If the dimming control is implemented at the high voltage input end, then the power efficiency is improved, but the safety risks due to high voltage exposure increase
Solution Approach 1:
The patent uses optically coupled isolation as an intermediary barrier that allows efficient power control while physically preventing high voltage exposure. The isolated control unit processes dimming signals and controls the power conversion without exposing the control circuitry or users to high voltage conditions, thus maintaining power efficiency while eliminating safety risks associated with high voltage exposure.
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 effectively achieves bi-level dimming with 100% and 30% brightness output, ensuring compliance with UL 1310 Class 2 specifications and providing a cost-effective, efficient dimming solution for LED lighting systems while protecting against lightning surges.
Implementation Method 1
adjusts the bi-level dimming output of the power supply to realize the PWM dimming technology with built-in oscillation circuit above 1 KHz for constant voltage output
Data Source
AI summary
A LED power supply with bi-level dimming receives an input voltage to supply power to an LED lamp, and adjusts the brightness of the LED lamp according to whether an external detection switch is triggered to be turned on. The LED power supply includes a conversion circuit, a switch, and an oscillation circuit. The conversion circuit converts the input voltage into an output voltage, and provides the output voltage to supply power to the LED lamp so as to control the LED lamp to provide a first brightness. The oscillation circuit provides a dimming signal with a fixed frequency and a duty cycle to the switch when the external detection switch is turned on so as to turn on and turn off the switch. The switch correspondingly adjusts the output voltage according to the dimming signal to control the LED lamp to provide a second brightness.