A problem about my switch mode Power supply - Page 1
Forum section: electronics / projects

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 03, 2019, 05:12:52 am
content: i made a 24V switch mode power and it is suppoed to output the current of 2A ,but ,after i did some experiments,i found the Volt drop down to 22V when the LOAD is 12ohm. (there is weird sound -ZiZi) (pdf 's left top part is the power supply)My problem 's video :https://www.youtube.com/watch?v=oZOkMZSDCR8&feature=youtu.be

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 03, 2019, 05:18:05 am
content: my SchDoc Pdf

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 03, 2019, 05:20:24 am
content: my PCB Doc ， hope the problem solved

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 03, 2019, 11:42:52 am
content: sorry,i forget to mention that the PSU part is in the left upon of the SCHDoc ,and i think the circuit around OPA or tl431 is the key ,however, i just cant adjust it properly.

author: xavier60
author_rank: Super Contributor
timestamp: November 03, 2019, 01:22:51 pm
content: I think R19 should connect to the rail being regulated, 24V.

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 03, 2019, 02:18:48 pm
content: it is a restrict current res , the Res change the volt is r10 r12 ,and i think the problem is relate to the current loop because the volt is accuracy with no load or larger than 20ohm

author: xavier60
author_rank: Super Contributor
timestamp: November 03, 2019, 02:38:57 pm
content: Look for "slow lane" and "fast lane"https://www.onsemi.com/pub/Collateral/TND381-D.PDF

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 03, 2019, 02:53:39 pm
content: thankyou for your book really, i found i know nothing about tl431...im so stupid...

author: xavier60
author_rank: Super Contributor
timestamp: November 03, 2019, 02:53:46 pm
content: Quote from: China NewBoy on November 03, 2019, 02:18:48 pmIs there activity at the comparator output pins?

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 03, 2019, 03:05:23 pm
content: Quote from: xavier60 on November 03, 2019, 02:53:46 pmi measured by multimeter, it has output ,and i increase the r28 r31 several times.. and then the problem is still there .after that i dont measure the amp anymore(in order to let the current limit larger i take r25 away)

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 03, 2019, 03:12:28 pm
content: Quote from: xavier60 on November 03, 2019, 02:53:46 pmit is late in china, i will try to figure out your datesheet tomorrow.thank you for your reply

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 04, 2019, 01:01:12 pm
content: Quote from: xavier60 on November 03, 2019, 01:22:51 pmI increase the value of R19 to 2.7K and the output volt seems no difference.

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 04, 2019, 01:05:32 pm
content: Quote from: China NewBoy on November 04, 2019, 01:01:12 pmi think what casue my problem is the current checking loop is too sensitive.

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 04, 2019, 01:13:37 pm
content: Quote from: China NewBoy on November 04, 2019, 01:01:12 pmsorry about my typing mistake (lack a no.....)..sorry

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 04, 2019, 01:28:13 pm
content: https://www.youtube.com/watch?v=oZOkMZSDCR8&feature=youtu.beMy problem Video

author: ocset
author_rank: Super Contributor
timestamp: November 16, 2019, 09:10:49 pm
content: your transformer is not phased correctly for it to be a flyback.(The dots are in the wrong place)

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 19, 2019, 10:36:20 am
content: thank you , i knew that my sch have the transformer mistake but my PCB doc is not wrong .....just too lazy to correct the sch

author: China NewBoy
author_rank: Regular Contributor
timestamp: November 19, 2019, 10:40:06 am
content: Quote from: China NewBoy on November 19, 2019, 10:36:20 amand the problem have been solved ,its c2_cha..... my stupid mistake, i take a 1uf cap to solder on c2_cha's place.and it cause the feedback volt too low