Filtering 50/60Hz Mains Voltage Using CLCLC Filter Cascades - Staccatoaudio
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15 June
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staccato studio 33

Filtering 50/60Hz Mains Voltage Using CLCLC Filter Cascades

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Introduction

When dealing with power supplies, audio amplifiers, or any sensitive electronic circuits, filtering the 50/60Hz mains voltage ripple is a critical step to ensure clean and stable DC power. One of the most effective solutions for suppressing mains frequency ripple and higher-order harmonics is the use of cascaded LC filters, often referred to as CLCLC filters.

 

The Basics of Mains Filtering

After rectification of the 50/60Hz mains voltage, ripple and harmonics remain. A simple capacitor filter (C) reduces ripple to some extent but is limited in performance. 

 

Why CLCLC Filters Are Superior

  • Ripple Rejection: CLCLC filters attenuate ripple more effectively, especially at 50Hz and its harmonics.
  • Current Pulses: Inductors reduce peak currents, lowering EMI and stress on components. While many filters focus on smoothing voltage, CLCLC also helps filter current ripple. The inductors limit the rate of current change (di/dt), resulting in a more stable and less noisy current supply — crucial for sensitive analog and digital loads.
  • Output Impedance: Lower and more stable over frequency range compared to single capacitor filters.
  • Noise Filtering: Better suppression of high-frequency interference.
  • Reduced Inrush Current to Large Capacitors: When large-value output capacitors are present, turning on the power can cause a massive inrush current, stressing rectifiers or switching elements. The series inductors in a CLCLC filter naturally limit this charging current, helping protect components and extend their lifespan.

 

Conclusion

A CLCLC filter is more than just a fancy low-pass filter — it’s a complete solution for modern power integrity challenges. By combining capacitive and inductive stages, it not only cleans up voltage rails but also filters current, reduces inrush surges, and shields delicate circuitry from the chaos of modern power supplies.

If you’re building a high-performance audio system, a precision instrument, or any application where noise is the enemy, CLCLC filtering may be the key to unlocking true performance.

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