TOOLS / LED DRIVERS
Constant-Current LED Driver Checker
Match the current. Check the full voltage range. Find how many modules fit in one series string.
Your LED & driver
One string of identical modules. Example values are illustrative.
01 LED MODULE
Target operating current (mA)
Per module. 0.7 A = 700 mA.
Forward voltage per module
Minimum module Vf (V)
Maximum module Vf (V)
Use Vf limits for the intended current, temperature and bin. Typical or reference-only values do not establish guaranteed limits.
Modules in series (pcs)
Count complete modules. The current stays the same along the string.
02 DRIVER OUTPUT
Output type
Set output current (mA)
For adjustable drivers, enter the chosen setting.
CC operating voltage range
Minimum CC voltage (V)
Maximum CC voltage (V)
Use the CC region at the set current, not input AC or open-circuit voltage.
Understanding the check
A constant-current (CC) driver is not a fixed-voltage supply. It holds one current across a stated voltage window (such as 24–48 V). This checker verifies that your whole series string stays inside that window at every point of the Vf range – because that is the only way the driver can actually guarantee its current.
LEDs are current-driven
Forward voltage (Vf) shifts with current, temperature and bin. The driver must hold the current, not the voltage – so you check against the driver’s current and the module’s Vf limits.
The driver CC window
The set current is only guaranteed inside the voltage window. Below the minimum the driver can’t push enough voltage; above the maximum it over-drives or cuts off.
String voltage = n × Vf
Modules in series add their forward voltages. A 4-module string at 9–10.5 V each needs 36–42 V at the intended current.
Load power = current × voltage
At 700 mA a 36–42 V string draws 25.2–29.4 W. Size the driver output power with headroom for the upper load.
Fit = the whole string voltage sits inside the driver window
min 24 Vmax 48 V
Pass only when the minimum string voltage ≥ the driver minimum and the maximum string voltage ≤ the driver maximum. Both extremes must fit, not just one.
Your result · Updates as you type
ENTERED LIMITS FIT
✓
4 modules need 36–42 V at 700 mA. This fits the entered 24–48 V CC window.
String voltage 36–42 V · Load power at target current 25.2–29.4 W
Does the whole range fit?
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Driver CC window 24–48 V · Your module string 36–42 V
12 V above the minimum · 6 V below the maximum.
Current setting
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Voltage window
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Driver power at target current
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Current tolerance
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Series count within entered limits
3–4 modules
Voltage window only, at the set current. Tap a count to try it.
Mathematical fit of user-entered limits for one identical-module string. Source guarantees, operating conditions and hardware compatibility are not verified. Ripple, start-up, dimming and thermal limits still require verification.
Good to know
Why check both voltage limits?
A constant-current driver holds its set current across a voltage window, not at a single point. Your module string must stay inside that window at every point of the Vf range – the lowest voltage with all minimum Vf values, and the highest voltage with all maximum Vf values. Either extreme outside the window means the current cannot be guaranteed.
Can I use a different current?
Only if your modules support it and the driver can be set there. Changing the current changes the Vf of each module (Vf rises with current), so re-check both voltage limits and the load power at the new current before relying on the fit.
Does a passing result guarantee compatibility?
No. This is a numerical check of the limits you entered. Real compatibility still depends on the driver’s guaranteed operating range, ripple and start-up behaviour, dimming performance, thermal limits and the wiring of the installation. Confirm with datasheets before commissioning.
What about dimming and parallel strings?
The checker models one series string. Parallel strings share the total current budget of the driver, and dimming changes the effective current – neither is included here. Plan parallel groups and dimming separately against the driver’s output limits.
What is behind the calculation?
String voltage = modules × module Vf (minimum and maximum). Load power = current × string voltage. The fit is a pass when the minimum string voltage is at or above the driver’s minimum CC voltage and the maximum string voltage is at or below the maximum. The series count is the range that keeps the whole string inside the window.
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