What Is The Optimal Design Configuration For A 1 MHz Resonant LLC Converter To Achieve High Efficiency (>95%) And Low EMI In A High-power DC-DC Application, Considering The Impact Of Parasitic Inductances And Capacitances On The Resonant Tank, And How Can I Mitigate The Effects Of Magnetizing Inductance Variation Due To Temperature Fluctuations In The Transformer?

To design an optimal 1 MHz resonant LLC converter for high-power DC-DC applications with >95% efficiency and low EMI, consider the following organized approach:

1. Resonant Tank Design

• Component Selection: Choose resonant inductor (L) and capacitor (C) to achieve a resonant frequency of 1 MHz using the formula ${ f_r = \frac{1}{2\pi\sqrt{LC}} }$. Ensure low ESR capacitors and low-resistance inductors to minimize losses.
• Parasitic Mitigation: Use surface-mount components, short PCB traces, and ground planes to reduce parasitic inductances and capacitances. Include these in simulations for accuracy.

2. Transformer Design

• Magnetizing Inductance (L_m): Select core materials with stable permeability over temperature. Design the converter to be less sensitive to L_m variations, possibly using adaptive control strategies.
• Leakage Inductance: Minimize leakage inductance through proper winding techniques to reduce voltage spikes and EMI.

3. Efficiency Optimization

• Loss Reduction: Focus on minimizing switching, conduction, and magnetic losses. Use zero-voltage switching, low-ESR components, and materials with low core losses.
• Thermal Management: Implement heatsinking and consider forced airflow. Place heat-sensitive components away from heat sources.

4. EMI Mitigation

• Layout and Filtering: Use shielding, proper grounding, and EMI filters. Minimize PCB loop areas and keep high-frequency currents localized.
• Harmonic Management: Ensure harmonics are within acceptable EMI standards, possibly using spread spectrum techniques if necessary.

5. Control Strategy

• Adaptive Control: Use digital controllers or specialized ICs that can adapt to component variations, such as changes in L_m due to temperature.

6. Testing and Simulation

• Simulation Tools: Utilize SPICE or power electronics software for pre-build simulations. Post-build, use oscilloscopes and thermal imaging for detailed analysis.
• Iteration and Optimization: Measure losses and iterate on the design to optimize efficiency and thermal performance.

7. Literature and Reference Designs

• Research: Consult design guides from companies like Texas Instruments or Infineon for proven approaches and reference designs.

By integrating these strategies, the converter will achieve high efficiency, low EMI, and robust performance, even with temperature-induced variations.