— The Often Overlooked Side Effects —

Adding capacitors is one of the most widely used methods for noise suppression. By shunting differential-mode noise to ground, they can provide effective noise reduction.

However, in practice, factors such as the following can lead to unintended effects:

• Increased ground impedance
• Increased parasitic capacitance
• Changes in current loops

These effects can often result in the conversion of differential-mode noise into common-mode noise.

Furthermore, additional issues such as the following may be introduced:

• Increased radiated emissions due to increased current loop area
• Higher inrush current
• Increased leakage current
• Startup delays

The Essence of Noise Suppression
This behavior is often described as a “whack-a-mole” phenomenon: even if noise is temporarily suppressed, it may reappear in another form.

 A More Fundamental Solution: Start with a Low-Noise Power Supply

A more effective approach is to use a power supply designed to minimize noise at its source.
Daitron’s ultra-low-noise switching power supplies offer:

• Ripple noise as low as 1 mVp-p (RFS series)
• Compliance with medical standards (LFS and PFS series)
• Low leakage current design

By reducing reliance on external filtering components, these solutions enable simpler and more reliable noise control.