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When your project needs more than one LED module, you must decide how to connect them to the driver. Series wiring is the standard approach for high-power LEDs and is how all our multi-LED modules (Tri-Stars, Quads, 7-Ups) are internally wired. Parallel wiring is sometimes necessary but requires more care.
Series Wiring
LEDs connected in series share the same current. The voltages add up.
- Current: Same through every LED (e.g., all see 350mA)
- Voltage: Adds up (e.g., 3 LEDs at 3.2V each = 9.6V total)
- Driver requirement: Output current matches the LED rating. Input voltage must exceed total Vf + overhead.
This is the default and preferred wiring method. A single constant-current driver ensures every LED in the string receives identical current, so they all produce the same brightness. Our multi-LED modules (Tri-Star, Quad, 7-Up) use series wiring internally.
Series Limits
The limit on series LEDs is your available voltage. Example with a BuckPuck DC (2.5V overhead):
If you need more LEDs than your supply can drive in series, split into multiple strings with separate drivers.
Parallel Wiring
LEDs connected in parallel share the same voltage. The currents add up.
- Voltage: Same across every LED
- Current: Splits between LEDs (unevenly if Vf varies)
- Driver requirement: Must supply total current for all LEDs
Parallel wiring is problematic for high-power LEDs. Even small differences in Forward Voltage between LEDs cause unequal current sharing. The LED with the lowest Vf draws the most current, runs hotter, which lowers its Vf further, which makes it draw even more current. This is the same thermal runaway risk as running LEDs without a driver — just slower.
When Parallel Is Necessary
If you must exceed the series voltage limit of your supply, you can run multiple series strings in parallel — but each string needs its own driver. This ensures each string gets regulated current regardless of Vf variation.
[Supply] → [Driver 1] → [LED string 1 (series)]
→ [Driver 2] → [LED string 2 (series)]Never connect two series strings to a single driver output in parallel.
Quick Comparison
| Series | Parallel | |
|---|---|---|
| Current sharing | Equal (guaranteed) | Unequal (depends on Vf matching) |
| Voltage | Adds up per LED | Same across all LEDs |
| If one LED fails open | Entire string goes dark | Other LEDs still work (but may overdrive) |
| Driver needed | One per string | One per string (not one shared across strings) |
| Recommended | Yes — default choice | Only with separate drivers per string |
Practical Recommendations
- 1–7 LEDs: Wire in series with a single driver. This covers Star through 7-Up modules on 24–36V supplies.
- 8+ LEDs: Split into multiple series strings, each with its own driver.
- Multi-LED modules: Already wired in series internally. Treat as a single unit — do not parallel two Tri-Stars on one driver.
- Color mixing modules: Internally series-wired. Drive with a single matched-current driver.
