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LED flickering is almost always a power delivery problem — either the driver, the power supply, or the wiring between them. High-power LEDs driven by a proper constant-current driver should produce rock-steady light with no visible flicker.
Work through this checklist from most common to least common cause.
Checklist
1. Loose or poor connections
The most frequent cause. Check every connection point between the power supply, driver, and LED module. Look for:
- Cold solder joints (shiny but not fully wetted)
- Wire strands touching adjacent pads
- Screw terminals not fully tightened
- Corroded contacts (especially in outdoor or marine installations)
Fix: Reflow solder joints. Strip and re-terminate wires. Clean corroded contacts.
2. Power supply issues
An undersized or failing power supply causes voltage sag under load, which makes the driver drop in and out of regulation.
- Is the supply rated for the load? The supply must deliver at least the driver’s minimum input voltage at full load current, not just at no load.
- Is the supply shared with other equipment? Motors, fans, or other drivers on the same supply can cause voltage dips.
- Is the supply old or damaged? Electrolytic capacitors in power supplies degrade over time, especially in hot environments.
Fix: Measure the supply voltage under load with a multimeter. If it sags below the driver’s minimum input voltage, use a higher-rated supply or a supply with more voltage headroom.
3. Input voltage too close to the minimum
DC buck drivers (BuckPuck, PowerPuck) need input voltage higher than the total LED Forward Voltage plus overhead (2.0V for PowerPuck, 2.5V for BuckPuck). If your supply voltage is right at this threshold, small fluctuations push the driver in and out of regulation.
Fix: Increase supply voltage. A 24V supply driving a string that needs 22.5V minimum is marginal — step up to 28V or 36V.
4. Dimming signal noise
If you are using an externally dimmable driver with a potentiometer or PWM signal:
- A noisy or jittery dimming signal causes the output to fluctuate
- Long dimming signal wires pick up electromagnetic interference
- A loose potentiometer wiper creates intermittent contact
Fix: Keep dimming signal wires short and away from power wiring. Use shielded cable if the run exceeds a few feet. Replace a scratchy potentiometer.
5. PWM dimming at low frequency
If you are dimming via PWM and the frequency is below ~200 Hz, some people can perceive the on-off cycling as flicker, especially in peripheral vision or when objects are moving. This is not a malfunction — it is normal PWM behavior at low frequencies.
Fix: Increase PWM frequency to 1 kHz or higher. Most people cannot perceive flicker above 200 Hz, but 1 kHz eliminates it for everyone.
6. Damaged LED or driver
Rare, but possible. A partially failed LED can cause erratic behavior. A damaged driver may oscillate.
Fix: Swap in a known-good LED module or driver to isolate the faulty component.
Still Flickering?
If none of the above resolves the issue, contact us with a description of your setup — power supply voltage and rating, driver model, LED module, and wiring length. We can help diagnose the problem.
