Introduction
Problem: Why LED Drivers Generate Noise
Three primary noise sources plague LED designs:
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Common-mode noise (70-90% of issues):
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Caused by PWM switching currents flowing through parasitic capacitances
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Frequency range: 100kHz-10MHz
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Differential-mode noise:
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Results from high di/dt loops in buck/boost converters
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Magnetic coupling:
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Poor component placement induces transformer whine
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Solution 1: Optimize PCB Layout for Noise Suppression
Fix the root causes before adding components
Critical layout rules:
- Keep high dv/dt traces ≤15mm long - MOSFET drains to transformer pins
- Place input capacitors ≤5mm from connector
- Use solid ground plane under control IC
- Separate analog/digital grounds with 2mm slot
Solution 2: Select the Right Filter Components
Common-Mode Choke Selection Guide
Based on UT2024 series specifications:
| Parameter | Requirement for 30W LED Driver | UT2024-222Y Performance |
| Inductance | 1-3mH | 2.2mH (min) |
| Rated Current | ≥1.2× operating current | 1.3A (50Hz) |
| RDC | <0.2Ω | 0.165Ω |
| Attenuation | >40dB @ 500kHz | 58dB (CM, 1MHz) |
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Use UT1609 series (9.5mm height) when space <15mm³
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UT1711A series when needing >10mH inductance
Solution 3: Implement FERRTX Common Mode Chokes
Why UT2024 Series Excels for LED Drivers
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Closed-core design :
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Reduces leakage inductance to <1%
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Prevents magnetic coupling to nearby components
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2-section winding:
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Maintains high impedance up to 30MHz
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Temperature resilience:
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Stable performance from -25°C to +125°C
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Installation best practices:
- Mount perpendicular to transformer (minimize coupling)
- Use thermal relief pads for heatsinking
- Verify creepage distance ≥3mm (critical for 250VAC designs)
Measured Results with FERRTX Components
After implementing UT2024-222Y in 50W high-bay lighting:
•500kHz noise: 52dBμV → 31dBμV
•Temperature rise: +48℃ → +29℃ • Certification: Failed → Passed EN55015 Class B
Top models for LED drivers:
• UT2024-222Y (2.2mH/1.3A) - Best for 20-50W
• UT1609-681Y (0.68mH/0.85A) - Compact designs
• UT1711A-232Y (2.3mH/1.7A) - High-current apps
