LED lights flickering may be a symptom of harmonics on a power system.

LED lights flickering may be a symptom of harmonics on a power system.

• A. True
• B. False
• C. Only at night
• D. Only with dimmers

Answer: (A)

Harmonic distortion on the power system can cause LED flicker because the currents and voltages are no longer perfect sine waves. LED drivers are switching power supplies that regulate current to the LEDs, and when the input waveform is distorted by harmonics, the regulator can respond irregularly. This can translate into fluctuations in the LED current or in the DC bus feeding the LEDs, which you perceive as flicker. Sometimes the flicker shows up at particular harmonic frequencies or interacts with the driver’s own switching frequency, making brightness vary noticeably. This isn’t limited to a specific time of day or to using dimmers. While dimmers can introduce their own flicker mechanisms, harmonic distortion can cause flicker even without dimmers, and it can occur at any time depending on the overall electrical load and grid conditions.

Harmonic distortion on the power system can cause LED flicker because the currents and voltages are no longer perfect sine waves. LED drivers are switching power supplies that regulate current to the LEDs, and when the input waveform is distorted by harmonics, the regulator can respond irregularly. This can translate into fluctuations in the LED current or in the DC bus feeding the LEDs, which you perceive as flicker. Sometimes the flicker shows up at particular harmonic frequencies or interacts with the driver’s own switching frequency, making brightness vary noticeably.

This isn’t limited to a specific time of day or to using dimmers. While dimmers can introduce their own flicker mechanisms, harmonic distortion can cause flicker even without dimmers, and it can occur at any time depending on the overall electrical load and grid conditions.