DC DC converter keep firing

[MAGICPIE3FOCUSPOWER]

Well I have 5 pieces of LMXXXXX DC DC 60V to ...volts converter.
But When I switched the the converter on, the LMxxxx chip keep blowing.

The converter chip can't handle 50V?

Thank in advance.

 

[dnmun]

i have never heard of a LMXXXX so it is hard to answer your question.

the 2596 has a version that is purported to work up to 60V but if it is then it would be labeled 2596hv

 

[MAGICPIE3FOCUSPOWER]

Yes you are right the chip is 2596HVS.
But do you know why the chip will blow when connecting to 50V pack?

Thank you

 

[heathyoung]

Because your pack isn't 50V when hot off the charger?

Or counterfeit components? I've had some bad luck running these on the edge as well, took one out with a 13S pack (~54V)

 

[wesnewell]

Probably because it's only rated to 40V.
http://www.ti.com/product/lm2596

 

[MAGICPIE3FOCUSPOWER]

Thanks for help.

Yes maybe it's just fake.
I don't trust it anymore to use at 60V.
So I am looking for a real one, anyone has a link for a decent DC DC converter?

 

[heathyoung]

Probably because it's only rated to 40V.
http://www.ti.com/product/lm2596

The HV part is rated to 60V.

 

[izeman]

Thanks for help.

Yes maybe it's just fake.
I don't trust it anymore to use at 60V.
So I am looking for a real one, anyone has a link for a decent DC DC converter?

paul/cellmann em3ev.com sells them.

 

[MAGICPIE3FOCUSPOWER]

Thanks for help all!

Yes I had one of those.
It has been working for one year 8)

So it died and bought these new LM2596HVS converter 8) .

So I think I have to buy old one again, more reliable...

 

[dnmun]

the lm2596hvs you have is not a texas instrument or national part. it is probably a design pushed to higher voltages than it can handle and sold in china in the secondary market.

 

[MAGICPIE3FOCUSPOWER]

Thanks, so I can say it is fake Texas Instruments chip?
I have three more LM2596HVS converters laying, but I am afraid it will fried again at 53V.

 

[wesnewell]

If you're trying to go from 53V to 12V, that's beyond its limits. Put 2 in series. Say 53V to 32V on the first and then 32V to 12V on the second.

 

[MAGICPIE3FOCUSPOWER]

Thanks.
So what is the max. difference voltage between input and output?

 

[dnmun]

how do you know you have 53V DC? the problem with the IC failing may not be related to the IC having a high voltage limit. something else in the circuit may be causing it to fail. that seems more likely imo.

 

[MAGICPIE3FOCUSPOWER]

I have a 48V pack and after full charged the voltage is 53V.
For the first time switching on everything works fine.
Second time switching on the chip blew.

So to make it sure the lamp is not short circuit, tested separate on lab psu light is working fine.

But I can use 53V and adjust it to 4.2V?

 

[izeman]

...But I can use 53V and adjust it to 4.2V?

at least i hope they can do it. that's what i bought them for. 44v (51v hoc) input and 5v output to drive a xm-l led light @2a.
paul's dcdc specs say:

Input Voltage - 4.5-60V
Output Voltage - 1.2-30V
Output Power - 15W
Output Current - 3A

 

[DAND214]

I have a 48V pack and after full charged the voltage is 53V.
For the first time switching on everything works fine.
Second time switching on the chip blew.

So to make it sure the lamp is not short circuit, tested separate on lab psu light is working fine.

But I can use 53V and adjust it to 4.2V?

What 48v battery peaks at 53v, SLA's? Or is it something else?

Dan

 

[wesnewell]

Look at the specs again.
http://www.ti.com/product/lm2596
vin max 40. vout max 40. max difference 37V. I'm no expert on buck converts, but all I've read say max difference is <40V on them. You might get it to take 53V, but it's not going to perform for long going down to 12V. All the ones I looked at on ebay say 35V max. There's lot of 63V buck convertors on ebay, but they warn not to try and exceed a 40V drop or pop. the ones I saw are using LM317's.
http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1311.R1.TR12.TRC2.A0.Xlm2596&_nkw=lm2596&_sacat=0&_from=R40
http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.Xlm317+buck+convertor&_nkw=lm317+buck+convertor&_sacat=0&_from=R40

 

[MAGICPIE3FOCUSPOWER]

I have lifepo4 pack.

Yes you are right today I tried again at 53V and I was not able to adjust the output >>> the chip blew

 

[carl-pedal]

The most easy way is to look for a AC adapter with 4.2v output. They work with dc if its not a transformator inside. I have it on my bike - 48 to 8.4v.

 

[MAGICPIE3FOCUSPOWER]

Any link?

I have many AC adapters with 4,2V output.
But current is max. 1A so not suitable for my project.

 

[izeman]

Any link?

I have many AC adapters with 4,2V output.
But current is max. 1A so not suitable for my project.

shouldn't 5v output work as well? i don't think that the led driver will have a problem with 5v input. at least i will try that.

 

[MAGICPIE3FOCUSPOWER]

Yes I have also many AC adapters with 5V output.
But I was afraid it will fried..., thanks for your tip I will looking for some AC 5V adapters with 2A or more output.

 

[heathyoung]

Interesting.

National Semiconductor USED to make the LM2596HV BEFORE they were taken over by TI - I have some genuine ones lying around somewhere.

Specs were 60V max.

Looks like TI dumped the HV variant, and someone is making the wafers for them somewhere and packing them - definitely counterfeit or old stock.

They were based on the 'simple switcher' chipset, and the transistor in them was rated to 60V (both in step-up and step-down - ie boost or buck).

You can still get at LM117K/317HV at 60V, and use it (linear reg) for switchmode - have a look at page 13 of http://www.ti.com/lit/ds/symlink/lm317hv.pdf