AC-DC Dual-Use LED Driver Circuit Design
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Solution Overview
Problem
Conventional LED driving circuits require additional components like photocouplers, increasing complexity and manufacturing costs, and often necessitate larger spaces due to the need for multiple elements to adjust duty ratios and control current.
Innovation Solution
An AC-DC dual-use LED driving circuit incorporating a buck-boost converter and a PWM signal controller with a common ground, eliminating the need for external photocouplers by dynamically adjusting the duty ratio and improving power factor with AC inputs, while maintaining constant current with DC inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LED driving circuit uses a transformer, PWM IC, constant-current circuit, and feedback circuit with photocoupler, then the LED can be driven with controlled current, but the circuit complexity increases and manufacturing cost rises
Solution Approach 1:
The patent combines the transformer primary side and secondary side into a single integrated circuit board, eliminating the need for separate photocouplers and multiple discrete components. The feedback signal is transmitted directly through the circuit board trace, merging functions that were previously separated by optical coupling components.
Solution Approach 2:
The integrated circuit board serves multiple functions simultaneously: it acts as the transformer core, provides electrical connections for primary and secondary sides, transmits feedback signals, and replaces the traditional photocoupler. This multi-functional design reduces component count while maintaining current control reliability.
2Ease of operation
If a conventional LED driving circuit employs a photocoupler for feedback coupling, then the duty ratio can be adjusted, but the accommodation space required increases
Solution Approach 1:
The feedback signal transmission path is merged directly into the circuit board trace, eliminating the need for separate photocoupler components and their associated mounting space. The duty ratio adjustment capability is maintained through direct electrical feedback coupling on the same board.
3Reliability
If a conventional LED driving circuit uses multiple discrete components for feedback and control, then the LED current can be regulated, but the manufacturing cost increases
Solution Approach 1:
Multiple discrete components (transformer windings, photocoupler, feedback resistors, and connection elements) are merged into a single integrated circuit board structure. This reduction in component count directly lowers manufacturing costs while maintaining LED current regulation through the integrated feedback path.
4Power
If a conventional LED driving circuit uses a transformer with separate primary and secondary sides, then voltage transformation is achieved, but the device complexity increases
Solution Approach 1:
The primary and secondary sides of the transformer are merged onto a single circuit board, with the feedback signal transmitted through a trace on the same board. This integration maintains voltage transformation capability while simplifying the overall circuit structure by eliminating separate components and optical coupling mechanisms.
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 reduces component count and manufacturing costs, simplifies circuit design, and enhances power efficiency by dynamically adjusting the PWM signal duty ratio and maintaining constant current regardless of input voltage levels, thereby improving power factor and reducing the need for additional filtering.
Implementation Method 1
the high frequency signals in the transformed signal ID which passes through the free-wheeling diode is filtered out by the low pass filter
Implementation Method 2
The PWM signal controller is used to output a PWM signal according to a feedback signal passing through the low pass filter for sequentially turning on and turning off the switching transistor
Data Source
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AI summary
An Alternating-current-Direct-current (AC-DC dual-use) Light Emitting Diode (LED) driving circuit includes an input power circuit, a buck-boost converter, and a Pulse Width Modulation (PWM) signal controller. The buck-boost converter, including a switching transistor, a feedback resistor, a low pass filter and a free-wheeling diode, receives a current signal output from the input power circuit, and drives an LED with a driving signal. The PWM signal controller outputs a PWM signal according to the feedback signal passing through the low pass filter, so as to sequentially turn on and turn off the switching transistor. Two ends of the free-wheeling diode are respectively connected to the low pass filter and the LED. A floating ground terminal of the PWM signal controller is coupled to the switching transistor and the low pass filter. Two ends of the feedback resistor are respectively connected to the floating ground terminal and the low pass filter.