SQ2516-6R8Y Common Mode Inductor Provides an Efficient Solution for Power Supply EMI Filtering.

In the final stage of product development, few things are more frustrating than confidently sending a prototype to the EMC lab, only to receive a report with "Conducted Emission Exceeded" marked on it. The project schedule is already behind. The launch date is approaching fast. The window for fixes is closing quickly. You have tried adjusting the PCB layout, swapped X capacitors from different suppliers, and even added ferrite cores on the input wires. But those stubborn noise peaks still sit above the limit line, unmoved. This is the "darkest moment" that almost every power supply engineer has experienced.

Exceeding conducted emission limits is one of the most common and troublesome EMI issues in switching power supply and communication equipment designs. The key to solving this problem is often not about trial and error, but about finding the right component – a common mode inductor that can effectively suppress common-mode noise.

1. Root Cause: Common Mode Noise on Power Lines

The root cause of exceeding conducted emission limits is mostly common-mode noise on the power lines.

• In switching power supplies, the high-speed switching of MOSFETs or IGBTs generates very high voltage change rates (dv/dt). These high-frequency signals couple through parasitic capacitance, forming common-mode currents on the input power lines. This current flows to the LISN (Line Impedance Stabilisation Network), and the voltage it generates is the conducted emission noise measured.
• Traditional solutions often use X capacitors and Y capacitors for filtering. But at higher frequencies (above several MHz), the effectiveness of capacitors diminishes. At this point, a common-mode inductor needs to be placed in series with the power line – it presents high impedance to common-mode currents, effectively attenuating the noise. At the input stage of switching power supplies, the common-mode inductor is not an optional component – it is a key element for meeting EMI standards.

2. Solution: SQ2516-6R8Y Common Mode Inductor

• The SQ2516-6R8Y common-mode inductor is specifically designed for common-mode noise suppression in AC/DC and DC/DC power lines. It uses an SMD package, compatible with automated SMT production lines. Its core value lies in two points: providing sufficiently high impedance to common-mode noise while maintaining low impedance to differential-mode signals, without affecting normal power transmission.
• Its optimised core material and winding structure provide stable common-mode attenuation performance across a wide frequency range (from several hundred kHz to tens of MHz). This is particularly important for broadband noise generated by switching power supplies – it does not target a single frequency point, but covers the entire conducted emission test band (150kHz to 30MHz).

Key product performance parameters include:

3. Engineering Practice Advantages: Solving EMI and Simplifying Design

The SQ2516-6R8Y uses an SMD package, allowing direct integration into automated SMT production lines. This reduces manual soldering variations and lowers production costs. Its common-mode and differential-mode characteristics are optimised to effectively suppress common-mode noise without significantly affecting differential-mode signals, simplifying the design and tuning of the filter network.

In practice, the SQ2516-6R8Y is typically placed at the power input – after the fuse, and before or after the X capacitor. Combined with appropriate X capacitors and Y capacitors, it forms a complete EMI filter. Its wideband characteristics cover 150kHz to several tens of MHz, effectively reducing noise at critical frequency points in conducted emission testing.

Conclusion: Accelerate Product Launch, Reduce Compliance Risk

Conducted emission testing is a critical gateway in the power product certification process, and often a major obstacle for many projects. The SQ2516-6R8Y common-mode inductor offers engineers an efficient and reliable solution. It effectively suppresses common-mode noise, helping products pass EMI standard certification. Its SMD package and optimised electrical characteristics also simplify the design process and production workflow.

For engineers currently struggling with EMI fixes, the right common-mode inductor is often more effective than repeatedly trying different capacitor combinations or adjusting PCB layouts. The SQ2516-6R8Y is specifically designed for EMI filtering needs in switching power supplies, communication equipment, and other applications, aiming to help engineers avoid unnecessary detours in EMI troubleshooting.

For more technical details or sample testing support, please feel free to contact our technical team.

📧 Email: sales@shinhom.com
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