Split LED Driver EMI Reduction via Inter-Trace Capacitance
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Solution Overview
Problem
Retrofit tube lamps with split switched-mode power supply drivers experience high electromagnetic interference due to stray inductances and capacitances along long PCB traces, making it difficult to meet regulatory EMI limits.
Innovation Solution
Incorporating capacitive devices along the conductive traces connecting the two driver parts of the electronic driver, which split stray inductances and shift resonance to higher frequencies, reducing EMI by limiting stray currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the driver is split into two parts and connected via long PCB traces, then the physical size of the driver is reduced and can be arranged in endcaps, but stray inductances and capacitances increase causing voltage fluctuations and EMI
Solution Approach 1:
A capacitor is introduced as an intermediary component connected between the two PCB traces that carry high current peaks. This capacitor acts as a mediator that provides an alternative current path, reducing the current through the stray inductance and thereby reducing voltage fluctuations and EMI generated by the long trace connection between driver parts
2Use of energy by moving object
If high current peaks travel along PCB traces connecting driver parts, then the driver can operate in boundary conduction mode for efficient LED driving, but voltage fluctuations occur due to interaction with stray inductances
Solution Approach 1:
A capacitor is placed beforehand between the PCB traces to cushion or absorb the voltage fluctuations caused by high current peaks interacting with stray inductances. This preemptive measure stabilizes the voltage before the fluctuations can propagate through the circuit, maintaining both efficiency and reliability
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 reduces electromagnetic interference across the frequency range of 9 kHz to 300 MHz, allowing the retrofit lamps to comply with statutory EMI limits.
Implementation Method 1
If a capacitor is connected between the two electrically conductive traces, the capacitor can reduce voltage fluctuations along the traces. The voltage fluctuations may interact with the stray capacitances and cause stray currents through the stray capacitances that end up in the metal element
Data Source
AI summary
A lighting device has a housing, a light engine located in the housing with a printed circuit board (PCB) and one or more light emitting diodes (LEDs) arranged on the PCB, and an electronic driver for controlling the LEDs. The electronic driver includes a first driver part located at a first position in the housing and a second driver part located at a second position in the housing, the first driver part is electrically connected to the second driver part via a pair of electrically conductive traces on the PCB. The lighting device includes one or more capacitive devices arranged along the pair of electrically conductive traces connecting the first driver part and the second driver part. Each capacitive device is connected with a first terminal to a first trace and a second terminal to a second trace.