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Some LED fixtures are current controlled (eg. 350mA, 500mA and 700mA). These require a continuous current. To turn the 220-240V
mains voltage into current, you need a separate power supply, a current controlled power supply.
Must be in series circuit
CONNECTING CURRENT CONTROLLED LED LIGHTS:
DO’S AND DON’TS
Setup simulation
Current controlled LEDs can never be connected under voltage! Furthermore, they should always be connected in a series circuit.
In series circuits there’s only one current path. The current enters through the + and leaves the spotlight through the - to continue its
way to the next spotlight. The current travels in one direction through all spotlights to until they are all under current.
Let’s try to simplify the matter with an example. In this setup, we’re going to install three LED spotlights, each with a power of 3,2W.
The spotlights require a continuous current of 350mA.
Calculate required voltage LED spotlight
Starting from the formula for electrical power, we can calculate the voltage needed by every separate spotlight. Power equals volts
times amps.
Formula for electrical power :
P (Watt) = U (Volt) x I (Ampère)
When we turn the formula around, we can calculate the voltage per spotlight:
Every separate LED spotlight needs 9,14V to keep a constant current of 350mA. In total, the three spotlights will need 27,42V (= 3 x
9,14V). The total voltage of the spotlights needs to be within the output reach of the power supply.
So, in this case, a 350mA LED power supply with an output from 17 to 34V, will do just fine. This power supply has a minimal voltage
output of 17V and a maximal voltage output of 34V. The total voltage required for the spotlights can’t be over or under the output level
of the power supply.
The external power supply needs to be adjusted to the number of spotlights and their power. With a constant current, the voltage will
spread equally over the different spots.
Serial connection
OK
NOT OK
Parallel connection
~
power
supply
+
-
+
-
+
-
+
-
~
power
supply
+
-
+
-
+
-
+
-
U(Volt) =
= 9,14 Volt
P(Watt)
I (Ampère)
3,2 Watt
0,35 Ampère (350mA)
~
power
supply
+
-
+
-
+
-
+
-
350mA
3,2W
350mA
Output 6-12W
Output 17-34V
350mA
3,2W
350mA
3,2W
Total voltage : 3 spotlights x 9,14V = 27,42 Volt
U(V) =
= 9,14 Volt per spot
P (W)
I (A)
3,2 W
0,35 A (350mA)
=
OK: within output range
