Introduction
PWM constant-voltage LED drivers, such as those from Ltech, are widely used for controlling 24 V LED strips in architectural, commercial, and residential lighting projects. While these drivers are robust and reliable, the performance and lifetime of the system strongly depend on correct cabling between the driver and the LED load.
In practice, many reported issues are not caused by the driver itself, but by incorrect cable selection, excessive cable length, or poor wiring layout. This article explains how PWM output cabling works, what to consider, and what can go wrong when cables are not designed correctly.
PWM output cables are power cables, not signal cables
The output of a PWM LED driver is switched 24 V power, not a low-level control signal.
Key implications:
High current flows through the cable
Voltage drop increases with distance
Cable resistance, inductance and layout directly affect system behavior
Treating PWM output wiring like “signal wiring” is one of the most common mistakes in LED installations.
Cable length and voltage drop
At 24 V, even small resistance causes noticeable voltage loss. Excessive voltage drop can result in:
Reduced brightness
Uneven light output
Visible color shift (especially white turning pink or green)
Different brightness per channel (RGB imbalance)
Rule of thumb:
Try to keep voltage drop below 5% (≈1.2 V at 24 V).
Longer distances require thicker cables or local power injection near the LED strip.
PWM behavior on long cables
Long cables add inductance and capacitance. In extreme cases this can lead to:
Less stable dimming at very low light levels
Minor shimmer or uneven fades
Increased electrical stress on the driver’s output stage
These effects usually appear after voltage drop issues, but they are real and should be considered for long cable runs.
EMI and “antenna” effects
Because PWM uses fast switching edges, long or poorly routed cables can radiate electromagnetic noise.
Possible symptoms:
Audible noise in nearby audio systems
Interference with sensitive electronics
Increased EMC complaints in professional environments
Cell phone interference is rare, but EMI risk increases when:
Cables are very long
Loop area between supply and return is large
Multiple PWM cables run in parallel
Cables are routed next to data, RF or audio lines
What can go wrong with incorrect cables
Incorrect cable choice or layout can cause:
Overheating of cables
Excessive voltage drop
Flicker or unstable dimming
Color inconsistency
EMI issues
Increased stress on the LED driver
In extreme cases, poor cabling can contribute to premature driver failure, even though the driver itself is operating within its rated specifications.
Best practices for PWM cabling
To ensure reliable operation:
Use adequate cable cross-section (often 1.5–2.5 mm² for longer runs)
Keep PWM cable lengths as short as possible
Place the driver close to the LED strip where feasible
Keep +24 V and channel returns together to minimize loop area
Avoid long parallel runs with data, RF or audio cables
Use power injection for long LED strips
Consider ferrite clamps near the driver in EMI-sensitive installations
Conclusion
Ltech PWM LED drivers are designed for professional lighting systems, but no driver can compensate for poor cabling. Correct cable sizing, routing and distance planning are essential for stable performance, consistent light output and long system lifetime.
If unexpected behavior or failures occur, cabling should always be the first item to check.
This article can serve as a reference when reviewing installations and diagnosing issues related to PWM LED systems.