Powering SMD 5050 strip via LM2596 DC/DC converter

adapterledpowerpower supplywatts

I decided not to order / use the power supply typically sold with SMD 5050 kits.
I heard a lot of explosion stories regarding those dodgy stuff.

I want to make my own (power supply to drive SMD 5050.
Using: a DC adapter found at home hooked up to LM2596 converter.

Facts:

  • From what I gather, LM2596 regulates the voltage AND can supply 1 to 2 amps of power safely (more requires heatsink?).

  • A single SMD 5050 chip uses 0.24 w of power.

  • SMD 5050's run on 12v.

My question:

  • Is it safe to assume that I can connect any number of LED strip blocks (with each block having 3 LEDs each using 0.24w, therefore ~0.75w), as long as total amps do not exceed what LM2596 AND power adapter attached to it can supply (being max 2 amps)?

My calculation:

watt = amps x volts means each LED uses 0.02 amp.

So if I have 30 blocks == 90 LEDs.

90 * 0.02 = 0.6 amps.

  • Would it work fine?

  • And if I just connect a single block needing 0.02 amp, would it still work fine?

  • What would happen if I connect more LEDs and exceed the amps LM2596 can provide?

I don't want my leds burning in day 2 and learn about this subject.

I'd very much appreciate it if all questions were answered.

Thank you!

Best Answer

LED strips work at \$12\, \mathrm{V}\$, but the individual chips do not. They are connected in groups of three with one series resistor. Voltage drop of one LED is around \$3.6\, \mathrm{V}\$, so the current is \$\dfrac{0.24}{3.6}\cong 65\, \mathrm{mA}\$. For 30 blocks, it is \$30\cdot 65 \cong 2\, \mathrm{A}\$.

LM2596 is quite ancient, you could do better with something like TPS54340 or even better, with synchronous buck regulator likeLT8614. Newer chips have higher switching frequecies, which means that you can use smaller inductors with fatter wire and also smaller capacitors.

With only one block attached, it will work just fine (although less advanced regulators will have lower efficiency).

If you connect too much LEDs, you will overload and overheat the regulator and it will employ its overtemperature protection.

Edit: LEDs are grouped by 3 like this:

pic