Author Topic: PWM Switch Replacement (Switched Mode PSU)  (Read 2083 times)

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Offline Dipski

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PWM Switch Replacement (Switched Mode PSU)
« on: April 16, 2015, 02:08:22 pm »
Hi Folks, I've got some power supplies I'm repairing that have faulty PWM switches (TOP202YAI). Replacements weren't readily available and I was recommended TOP224YN as better replacements in this PSU. I have found the TOP224YN's to be failing so I thought I'd see if I've been recommended the wrong IC as I'm not familiar with PWM switches and the specifications are different between the two switch series.

Reading the data sheets the TOP202YAI has an output power range of 15-30 watts (Flyback) and 30-75 watts (PFC/Boost), while the TOP224YAI lists 45 watts output.

Is the 45 watt rating for the TOP224YAI its maximum PFC/Boost rating or its maximum Flyback rating (or both)?

Could anyone recommend a suitable modern day replacement for the TOP202YAI?
 

Online wraper

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Re: PWM Switch Replacement (Switched Mode PSU)
« Reply #1 on: April 16, 2015, 05:05:57 pm »
Should work. Probably something else failed. Maybe snubber circuit across transformer primary winding. Does it work for some time at all? If not at all, could be shorted diode on secondary side too.
 

Offline Dipski

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Re: PWM Switch Replacement (Switched Mode PSU)
« Reply #2 on: April 16, 2015, 05:37:24 pm »
Yes, it did work - first instance was in a known working PSU and the TOP224YN ruptured and shorted after 5 minutes of operation. This machine originally had a TOP202YAI suspect of causing under supply at high temperature, >70 degC

I installed another into another known working PSU which seems to run fine on the workbench - I monitored temperature on the chip and it doesn't overheat or get hot, around 40 degC was the highest temperature measured.

Third install of a TOP224YN has resulted in a PSU failure - I'm awaiting return of the unit to inspect. This PSU originally had a TOP202YAI failing at >50 degC and after replacing with TOP224YN was working and tested at 60 degC for 10 minutes.
 

Online wraper

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Re: PWM Switch Replacement (Switched Mode PSU)
« Reply #3 on: April 16, 2015, 05:49:42 pm »
Where have you bought those TOP224YN?
« Last Edit: April 17, 2015, 09:36:31 pm by wraper »
 


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