[SOLVED] Power resistors for LM2673 Switch Power Supply

jmx66 · Jul 17, 2015

Hi all,

Project: basic swich mode power supply output :2-3 A and 24 -25 V

I only need to know power for resistors R1 and R adjust 1 ( See schematic )

LM26 2673 Datasheet

https://www.ti.com/lit/ds/symlink/lm2673.pdf

RK8012 80VA 2 x 12 V 2 x 1,33 A

https://www.reichelt.de/Ringkerntra...U11a5d5257676d424785d6d96149a4495&LANGUAGE=EN

For R1 = 1 KOhm Vfeedback= 1,21 V so 1,21/1000 = 1mA P= 1,21 mW 0,6 W right math and value ?

For R adjust1, how to compute right power ??
10 KOhm, can't find 8,62 KOhm

As usual, thanks a lot for your help.

jm

KlausST · Jul 18, 2015

Hi,

Your calculation for R1 is correct.

For R_adjust a 0.6W should be ok also.
V_max = sqrt (P x R) = sqrt (10k Ohms x 0.6W) = about 800

Reconsider your connections in the voltage feedback path. In case of disconnected (maybe accidentally) connector next to R1 the output voltage will rise to it's maximum. Try to go the safe side. On interruption --> low output voltage.

Klaus

jmx66 · Jul 18, 2015

KlausST said:
Hi,

Your calculation for R1 is correct.

For R_adjust a 0.6W should be ok also.
V_max = sqrt (P x R) = sqrt (10k Ohms x 0.6W) = about 800

Reconsider your connections in the voltage feedback path. In case of disconnected (maybe accidentally) connector next to R1 the output voltage will rise to it's maximum. Try to go the safe side. On interruption --> low output voltage.

Klaus

Thanks a lot for your help, Klaus.

I'm going to redraw the schematic.

jm

[SOLVED] Power resistors for LM2673 Switch Power Supply

jmx66

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KlausST

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jmx66

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[SOLVED] Power resistors for LM2673 Switch Power Supply

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