Conducted interference testing for switching power supplies (SPS) is governed by global and regional standards to ensure they do not disrupt the operation of other electronic devices via power lines. The most widely adopted standards include CISPR 22 (International Special Committee on Radio Interference) for information technology equipment, EN 55022 (European adoption of CISPR 22), and FCC Part 15 (U.S. Federal Communications Commission) for unintentional radiators.

These standards define two key test categories: conducted emissions (CE) and conducted susceptibility (CS). For conducted emissions, testing focuses on measuring noise voltages injected into the AC or DC power lines by the SPS, typically in the frequency range of 150 kHz to 30 MHz (for CISPR 22/EN 55022) and 150 kHz to 108 MHz (for FCC Part 15). The test setup uses a line impedance stabilization network (LISN) to provide a standardized impedance (50 Ω) for accurate noise measurement, and a spectrum analyzer to capture voltage levels. Limits are classified into Class A (for industrial environments) and Class B (for residential/commercial environments), with Class B having stricter limits (e.g., ≤40 dBμV for frequencies 150 kHz–500 kHz).

For conducted susceptibility (also called immunity testing), standards like IEC 61000-4-6 specify testing methods to evaluate the SPS’s ability to operate normally when exposed to conducted disturbances. The test injects differential-mode (DM) and common-mode (CM) noise into the power lines using a coupling/decoupling network (CDN), with test levels ranging from 10 V to 40 V (for DM) and 10 V to 20 V (for CM) across frequencies 150 kHz–80 MHz.

Compliance testing requires adherence to strict environmental conditions (e.g., temperature 23°C ±5°C, humidity 45%–75%) and calibration of test equipment (LISN, spectrum analyzer, CDN) to ensure accuracy. Non-compliant SPS may face market access restrictions, making adherence to these standards critical for global commercialization.

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