MCPCB Local Shielding for LED Driver EMI Reduction
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Solution Overview
Problem
High power LEDs mounted on metal core printed circuit boards (MCPCBs) generate significant heat and suffer from unwanted electromagnetic interference (EMI) due to parasitic capacitive coupling, which can lead to failure in electromagnetic compatibility (EMC) tests, especially when the base metal substrate is floating or has a thin dielectric layer for improved thermal performance.
Innovation Solution
A local shielding area of conductive material is formed on the MCPCB directly below the DC voltage node and devices that carry steep slope voltage waveforms, connected via a conductive via to the DC voltage node, effectively reducing parasitic capacitive coupling and EMI by providing a low AC impedance path for high-frequency voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thin dielectric layer is used in the MCPCB to improve thermal performance, then heat dissipation is improved, but parasitic capacitive coupling increases causing EMI problems
Solution Approach 1:
A local shielding area formed from the second patterned metal layer acts as an intermediary element between the first patterned metal layer and the base metal substrate. This shielding area, connected to a DC voltage node, mediates the electromagnetic field interactions and reduces parasitic capacitive coupling while allowing the thin dielectric layer to maintain its thermal performance.
2Device complexity
If the base metal substrate is made floating to reduce complexity, then manufacturing is simplified, but electromagnetic compatibility performance deteriorates
Solution Approach 1:
Rather than making the entire base metal substrate floating or grounded, the invention applies a localized shielding area in specific regions where parasitic capacitive coupling occurs. This local quality approach maintains manufacturing simplicity while improving EMC performance in critical areas through the second patterned metal layer connected to DC voltage nodes.
3Object-affected harmful factors
If conventional PCBs are used instead of MCPCBs, then EMI performance is improved, but thermal performance deteriorates
Solution Approach 1:
The invention merges the advantages of both conventional PCBs and MCPCBs by combining the EMI shielding capability of conventional PCBs with the thermal performance of MCPCBs. The second patterned metal layer and local shielding areas provide conventional PCB-like EMI protection, while the metal core substrate maintains superior heat dissipation.
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 local shielding area significantly reduces EMC problems by isolating parasitic capacitance, allowing the MCPCB to meet EMC standards while maintaining effective heat dissipation, thus ensuring reliable operation of high power LED modules.
Implementation Method 1
unwanted electromagnetic interference (EMI) due to parasitic capacitive coupling
Implementation Method 2
connected via a conductive via to the DC voltage node, effectively reducing parasitic capacitive coupling and EMI by providing a low AC impedance path
Implementation Method 3
The MCPCB may have better thermal performance than other PCBs due to the relative thickness of the metal substrate which may improve lateral heat spreading and heat dissipation to a heat sink
Data Source
AI summary
A light emitting diode (LED) module may include a direct current (DC) voltage node formed on a first layer. The DC voltage node may be configured to sink a first current. One or more devices may be formed on the first layer configured to provide a second current to one or more LEDs. A device of the one or more devices may carry a steep slope voltage waveform. A local shielding area may be formed in a second layer directly below the DC voltage node and the one or more devices. The local shielding area may include a substantially continuous area of conductive material. A conductive via may extend through one or more layers. The conductive via may electrically connect the DC voltage node and the local shielding area.