What causes flickering in LED streetlights?

Flickering—rapid, perceptible flashes of light—in LED streetlights is typically caused by issues with the LED driver or power supply. Common causes include:

1. Excessive output ripple: The output current from the driver contains a significant AC component (100Hz or 120Hz), causing the LED brightness to fluctuate in sync with the current. While this flickering may not always be visible to the naked eye, it can often be detected as scrolling bands when viewed through a smartphone camera. Solution: Replace the driver with one that offers better ripple suppression.

2. Low PWM dimming frequency: If PWM (Pulse Width Modulation) dimming is used at a frequency below 100Hz, the human eye will perceive flickering. Ensure the PWM frequency is at least 1000Hz (ideally 3000Hz or higher).

3. Power supply voltage fluctuations: Sharp fluctuations in grid voltage—often caused by the starting or stopping of nearby high-power equipment (such as air conditioners or elevators)—can destabilize the driver's output. Consider installing a voltage stabilizer or providing a dedicated power supply for the streetlights.

4. Incompatibility between the driver and the dimmer: Using an incompatible dimmer (e.g., using a standard dimmer with a 0–10V driver) can lead to flickering. Verify the specifications of the dimmer.

5. Poor electrical contact: Loose terminals or broken internal wiring can cause intermittent power supply. Ensure all connection points are securely fastened.

6. Internal luminaire faults: Loose solder joints on individual LED chips can cause the circuit to connect and disconnect as the components expand and contract due to temperature changes. In such cases, the affected LED chips or modules must be replaced.

Road lighting standards generally require a flicker percentage of ≤5% (≤3% for expressways). Flickering should be addressed promptly, as it not only compromises visual comfort for drivers but can also lead to misjudgment of road conditions.