LED Array Designer

This tool calculates total supply current, required supply voltage headroom, total power consumption, and per-string voltage drop for series-parallel LED arrays. It also validates whether the specified supply voltage is sufficient to drive the configured array given the forward voltage (V_f) and string count.

Series-parallel is ideal for balancing efficiency, thermal management, and driver compatibility—especially with fixed-voltage supplies (e.g., 12 V or 24 V DC). All-series requires higher voltage and risks single-point failure; all-parallel demands precise current matching and risks thermal runaway without individual current limiting.

“LEDs per String” is the number of LEDs connected in series within one branch. “Number of Strings” is how many such identical branches are connected in parallel across the supply. Total LEDs = (LEDs per String) × (Number of Strings).

Standard white LEDs typically have V_f = 2.8–3.6 V at I_f = 150–350 mA. High-power LEDs may range up to 4.2 V at 700 mA or more. Always refer to the LED datasheet—V_f varies with temperature and batch, and I_f must not exceed absolute maximum ratings.

This occurs when the supply voltage (V_S) is less than the minimum required: V_S < (LEDs per String × V_f) + V_drop, where V_drop ≥ 1–2 V is needed for current regulation (e.g., resistor or constant-current driver headroom). Increasing V_S or reducing LEDs per string resolves it.

The tool doesn’t auto-calculate resistor values, but you can derive it post-calculation: R = (V_S − N × V_f) / I_f, where N = LEDs per String and I_f is per-string current (in amps). Ensure resistor power rating ≥ (V_S − N × V_f) × I_f — double it for safety margin.

No — the LED Array Designer assumes uniform LEDs (same V_f and I_f) across all strings. Mixing colors or types causes unequal current sharing and potential overdriving. For heterogeneous arrays, design each color group separately and sum total system requirements manually.

LED V_f decreases ~2 mV/°C rise, while I_f capability drops with junction temperature. The tool uses nominal room-temp V_f; for high-ambient or high-density layouts, reduce I_f by 10–20% or increase heatsinking. Always validate with thermal simulation or testing.

Per-string current equals the LED’s rated forward current (I_f). Total current = I_f × Number of Strings — this determines driver capacity, trace sizing, and fuse rating. Never assume per-LED current equals per-string current unless strings contain only one LED.

It’s designed for DC low-voltage systems (e.g., 12 V or 24 V battery or regulated supplies). For AC line-powered designs (e.g., 120 V), use it only for downstream DC sections (e.g., after an AC/DC driver). Always account for driver efficiency and ripple when estimating input power and thermal load.