Author Topic: A problem about my switch mode Power supply  (Read 1863 times)

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Offline China NewBoyTopic starter

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A problem about my switch mode Power supply
« on: November 03, 2019, 05:12:52 am »
 :-// 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
« Last Edit: November 04, 2019, 02:08:57 pm by China NewBoy »
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #1 on: November 03, 2019, 05:18:05 am »
my SchDoc Pdf
« Last Edit: November 03, 2019, 05:26:20 am by China NewBoy »
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #2 on: November 03, 2019, 05:20:24 am »
my PCB Doc , hope the problem solved :-+
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #3 on: November 03, 2019, 11:42:52 am »
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.
 

Offline xavier60

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Re: A problem about my switch mode Power supply
« Reply #4 on: November 03, 2019, 01:22:51 pm »
I think R19 should connect to the rail being  regulated, 24V.
HP 54645A dso, Fluke 87V dmm,  Agilent U8002A psu,  FY6600 function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.
 
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Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #5 on: November 03, 2019, 02:18:48 pm »
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
 

Offline xavier60

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Re: A problem about my switch mode Power supply
« Reply #6 on: November 03, 2019, 02:38:57 pm »
Look for "slow lane" and "fast lane"
https://www.onsemi.com/pub/Collateral/TND381-D.PDF
HP 54645A dso, Fluke 87V dmm,  Agilent U8002A psu,  FY6600 function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #7 on: November 03, 2019, 02:53:39 pm »
thankyou for your book really, i found i know nothing about tl431...im so stupid...
 

Offline xavier60

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Re: A problem about my switch mode Power supply
« Reply #8 on: November 03, 2019, 02:53:46 pm »
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
Is there activity at the comparator output pins?
HP 54645A dso, Fluke 87V dmm,  Agilent U8002A psu,  FY6600 function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #9 on: November 03, 2019, 03:05:23 pm »
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
Is there activity at the comparator output pins?
i 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 :-X  (in order to let the current limit larger i take r25 away)
« Last Edit: November 03, 2019, 03:08:52 pm by China NewBoy »
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #10 on: November 03, 2019, 03:12:28 pm »
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
Is there activity at the comparator output pins?
it is late in china, i will try to figure out your datesheet tomorrow.thank you for your reply
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #11 on: November 04, 2019, 01:01:12 pm »
I think R19 should connect to the rail being  regulated, 24V.
I increase the value of R19 to 2.7K and the output volt seems no difference.
« Last Edit: November 04, 2019, 01:09:58 pm by China NewBoy »
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #12 on: November 04, 2019, 01:05:32 pm »
I think R19 should connect to the rail being  regulated, 24V.
I increase the value of R19 to 2.7K and the output volt seems difference.
i think what casue my problem is the current checking loop is too sensitive.
« Last Edit: November 04, 2019, 01:09:22 pm by China NewBoy »
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #13 on: November 04, 2019, 01:13:37 pm »
I think R19 should connect to the rail being  regulated, 24V.
I increase the value of R19 to 2.7K and the output volt seems no difference.
sorry about my typing mistake (lack a no.....)..sorry
 

Offline China NewBoyTopic starter

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Offline ocset

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Re: A problem about my switch mode Power supply
« Reply #15 on: November 16, 2019, 09:10:49 pm »
your transformer is not phased correctly for it to be a flyback.
(The  dots are in the wrong place)
 
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Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #16 on: November 19, 2019, 10:36:20 am »
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
 

Offline China NewBoyTopic starter

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Re: A problem about my switch mode Power supply
« Reply #17 on: November 19, 2019, 10:40:06 am »
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
and 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
« Last Edit: November 19, 2019, 10:41:37 am by China NewBoy »
 


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