Author Topic: Replacing a off-line switcher IC to a higher switching frequency IC  (Read 3049 times)

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Offline YaminTopic starter

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I've got a power supply which came into repair with a blown TOP258MG IC. There were couple of diode shorted and leaky caps. I have replaced them all.
The issue is I have only got TOP258MN, everything is identical except the switching frequency.
TOP258MG = 66kHz
TOP258MN = 132kHz (the one I have)
My question is could it be replaced, and if there would be any side effects
Thanks
 

Offline coromonadalix

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Re: Replacing a off-line switcher IC to a higher switching frequency IC
« Reply #1 on: November 11, 2022, 11:58:19 am »
normally  the xformers or coils are calculated for the "normal" 66khz working frequency,  not the higher one
 

Offline YaminTopic starter

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Re: Replacing a off-line switcher IC to a higher switching frequency IC
« Reply #2 on: November 11, 2022, 12:01:31 pm »
Thanks, I wonder what would happen if the switching frequency is higher. (higher freq should result in less switching losses right?)
Would the PS work as it should though?
Also what might happen to the output voltage of the ps
« Last Edit: November 11, 2022, 12:04:26 pm by Yamin »
 

Offline ingalopez

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Re: Replacing a off-line switcher IC to a higher switching frequency IC
« Reply #3 on: November 14, 2022, 06:48:10 pm »
Probably bad things may happen!
As previos post remarks, the filters Transformer, etc has been calculated for a much lower frequency.
 In the best case something may get very hot , and prone to fail unexpectedly.
 

Offline YaminTopic starter

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Re: Replacing a off-line switcher IC to a higher switching frequency IC
« Reply #4 on: November 14, 2022, 10:58:53 pm »
Thanks for the insights, I am a bit confused regarding the two ICs. From the datasheet of the TOP ICs there is no mention of a TOP258MG. It talks about only MN.
Only a google search shows these two as different IC, but the datasheet link goes to datasheet I mentioned.
Any idea on how to double check this?
 

Offline Audiorepair

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Re: Replacing a off-line switcher IC to a higher switching frequency IC
« Reply #5 on: November 14, 2022, 11:32:13 pm »
The data sheet says:

In the M, P and G packages and the TOP259-261 Y package option, the full frequency PWM mode is set at 66 kHz, for higher efficiency and increased output power in all applications.


From this data sheet:
https://www.mouser.co.uk/datasheet/2/328/tophx_family_datasheet-1511305.pdf
 

Offline YaminTopic starter

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Re: Replacing a off-line switcher IC to a higher switching frequency IC
« Reply #6 on: November 14, 2022, 11:44:15 pm »
The data sheet says:

In the M, P and G packages and the TOP259-261 Y package option, the full frequency PWM mode is set at 66 kHz, for higher efficiency and increased output power in all applications.


From this data sheet:
https://www.mouser.co.uk/datasheet/2/328/tophx_family_datasheet-1511305.pdf
Yes exactly that's what I mean, the datasheet does not mention about the last letter (N or a G or any significance of that). But a google search of TOP258MG vs TOP258MN yields a result showing that it has got two different switching frequency with everything else the same. The same parameters are displayed on mouser but when I click the datasheet link it directs to the one you also have attached for both the ICS
 

Online fzabkar

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Re: Replacing a off-line switcher IC to a higher switching frequency IC
« Reply #7 on: November 15, 2022, 12:00:47 am »
The E and Y packages for the TOP258 have an F pin (pin #4) which sets the frequency to 66kHz or 132kHz. This pin is missing from the M package.

Quote
FREQUENCY (F) Pin (TOP254-258Y, and all E and L packages):

Input pin for selecting switching frequency 132 kHz if connected to SOURCE pin and 66 kHz if connected to CONTROL pin.

The switching frequency is internally set for fixed 66 kHz operation in the P, G, M package and TOP259YN, TOP260YN and TOP261YN.

I wonder if TOP258MG and TOP258MN differ in pin#4, ie perhaps the 132kHz version retains pin #4 rather cutting it off.

Edit:

I just answered my own question (pin #4 is missing in both):

https://www.google.com/search?q=TOP258MN&tbs=isz:m,itp:photo&tbm=isch
https://www.google.com/search?q=TOP258MG&tbs=isz:m,itp:photo&tbm=isch


Edit #2:

The manufacturer's web page for the TOP258MN specifies Switching Frequency (max) = 66kHz.
https://www.power.com/products/topswitch/topswitch-hx/top258mn

There is no TOP258MG part on the web site:

https://www.power.com/products/topswitch/topswitch-hx
« Last Edit: November 15, 2022, 12:13:21 am by fzabkar »
 

Offline Audiorepair

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Re: Replacing a off-line switcher IC to a higher switching frequency IC
« Reply #8 on: November 15, 2022, 07:55:38 am »
Digikey show it as a 66kHz device.

https://www.digikey.co.uk/en/products/detail/power-integrations/TOP258MN/1657675


Perhaps the AiPCBA data is incorrect, or they sell a clone not made by Power Integrations.
 


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