Tagarchief: SMPS

LM2576T-5 step down switching regulator

First switching power supply working.

I have an ARM board to be powered, which draws between 0.5 and 1.5 ampere’s on 5 volt. Tried using an standard 7805 (2 ampere spec), but the system would not boot. VOut dropped to 4.5 volts and 7805 was getting to hot with +/- 24 volt VIn.

So i made an circuit based on the LM2576T-5.

Partslist:

Part Price
IC1: LM2576T-5 € 1,60
L1: Inductor 100uH € 1,45
D1: SR504 Recoverd from PC PSU 5.0 Amps Schottky Barrier Rectifier
C1: 470uF 35v Reused from other project
C2: 3300uF 10v Also recovered from PC PSU
F1: Fuse holder and 400mA Stock, price n/a

lm2576t-5-schemaInput voltage is an battery+solar power supply that varies between 23-24 to 29 volts.

Working power supply (left) with active load.
img_20160925_184405_edit

Bad output: (spikes)
What happens if an normal (or to slow) diode is used:
Yellow is regulator V-OUT.
Blue line represents voltage output for load (feedback signal).

img_20160924_194739_edit

Good output:
No load:

noload

100mA load

100ma_load

 

Borrowed lm2576 library for Eagle PCB Design from eaglecentral.ca | LM2576 circuit