19V at 5A

I have a 24volt supply that I want to reduce to 19volts, the circuit needs to be able to carry 4A current so I’m using the LM338 which can carry 5A.

What size resistors should I use to get the 19v required and be able to carry the 4 Amps?

by MeElec
May 28, 2019

1 Answer

Answer by wangwg88

Please read the datasheet of LM338 (from digikey.com). You just use its typical application circuit of figure 15. You can assume R1 = 270 ohm, then calculate the R2 from the formula. The current passing resistors is 4.6mA, so the power of resistors can be 0.1W. The 4A will cause the LM338 a large heat: the voltage drop is 24-19 = 5V, P = 5Vx4A = 20W, so you need to add a big cooler for 20W if the current is continuous.

+1 vote
by wangwg88
May 28, 2019

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