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Power Supply Problem

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m.muzammil

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I have used 48V to 12V power module but it starts heating after some time where end device current consumption is around 200mA. Anyone, please help me to find the perfect circuit of power supply of 48V to 12V?
 

KlausST

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Hi,

ebay, Amazon, internet is full of them. Just do a search. We had to do the same.

But to find a suitable one .. you need to know the requirements.
Like
* min/max input voltage
* max load current,
* allowed ripple voltage
* max allowed temperature
* and so on...

Klaus
 

m.muzammil

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Hi,

I did the research and found the converter named LM2596HVS it has 5V-60V input support with 3A but when I connect it with Forklift battery which has 48V, but LM2596HVS got damaged.
 

KlausST

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Hi,

from my experience: It´s not the LM2596´s fault.
As long as you run it within the specifications it will work reliably.

I neither know the forklift nor the battery. But it´s quite possible that there are voltage spikes on the 48V cables that kill the LM2596 ... if so, the spikes will also kill other devices.

So you have to find out the fault, maybe by checking the battery voltage during normal operation.

Klaus
 

c_mitra

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Hi,
when I connect it with Forklift battery which has 48V, but LM2596HVS got damaged.
The 48V is the nominal voltage of the battery. Most common forklift batteries are lead acid type. Each cell is nominal 2V and there will be 24 cells in series. More commonly four 12V units are put in series.

Each cell, fully charged, can be 2.4V; the fully charged battery will then be 24x2.4=58V. Too close to the max spec.

If you connect it to the charger, the voltage applied to the battery will be about 10V higher (often 15V): charging voltage will be 70V and higher.

The forklift also uses the battery to move around and do other things. These motors produce lots of spike voltages.

Sorry that the LM2596HVS came to an untimely end. But it could not handle the input voltage.
 

c_mitra

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Can I use a TVS diode of rating 60v at the input of the LM2596HVS converter?
I did a quick lookup of the LM2596 datasheet. The one I looked up is here: https://www.ti.com/lit/ds/symlink/lm2596.pdf

Under "Absolute Maximum Ratings" it says that the max input voltage is 45V

Under operating conditions, it says the input voltage is 40V max.

As a conservative designer, you should not use more than 35-38V at the input. That will keep some margin for noise.

Hence the answer is NO!

Better to look for different chips or modules.
--- Updated ---

But you can try with a power zener diode in series with the input. The zener may be at lest 9-12V and rated for 1W or more.
 
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owais.akhlaq

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I did a quick lookup of the LM2596 datasheet. The one I looked up is here: https://www.ti.com/lit/ds/symlink/lm2596.pdf

Under "Absolute Maximum Ratings" it says that the max input voltage is 45V

Under operating conditions, it says the input voltage is 40V max.

As a conservative designer, you should not use more than 35-38V at the input. That will keep some margin for noise.

Hence the answer is NO!

Better to look for different chips or modules.
--- Updated ---

But you can try with a power zener diode in series with the input. The zener may be at lest 9-12V and rated for 1W or more.
LM2596HV has the ratings of 63Volts, almost 10volts above the input voltage i.e. 53volts(for full charge batteries). Still it burned out. the only thing now left is the spike voltages that might be generating because of the movement of fork lifter.
 

BigBoss

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An Appropriate Power Resistor at the Input of the Regulator will solve your problem.
It will decrease the Input Voltage and protect the Regulator against transients.
 

KlausST

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Hi,

About 60V TVS:
I don't know which one you refer to...but you should read the datasheet:
* nominal operating voltage
* peak voltage at rated (or expected) current, max clamping voltage..


It's not unusual for a 60V rated TVS
* have a starting breakdown voltage of more than 73V
* have a max clamping voltage above 120V

It's not the case that a 60V rated TVS is able to limit the voltage to 60V.

Klaus
 

Taihung

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I know few solution for 48V to 12V 3A.
And I would like to know how "perfect" in your request.
Each solution is most suitable for its application like: home, automotive, medical, space, military.
Your testing with LM2596 was failed, that is truly. Becasue IC LM2596 did not fit your requirement.
Known that LM2596 is quite cheaper than other but it is very old type, it don't have soft-start, whick will spoil if input is high as 48V.
If you still want it run properly under 48V, I have a trick like this (worked in some my project):
Add a few ohm resistor 3W/5W before input capacitor of LM2596. The better is use NTC.
This option make input of LM2596 rising slowly and charge current to output capacitor in limit range.
If input voltage apply rise to fast, LM2596 will open nearly 100%, the current through IC is (48V-0V)/(ZL+RL).
This high current make surge dissipation power on high side valve in LM2596, which drop over 2V and spoild IC.
Some IC faked from unauthoried saler have max input is 40V then remarking to HS to sale for higher price, also make spoil.
But with this option can work with output 12V1A is suggested.
If you need 3A output at 12V, you should use other solution.
Why ?
You read datasheet which claim can support 3A continous output current is right, but it is only half truly story.
3A output with 3.3V is ok, that is 3Ax 3.3V = ~10W.
If 12V x 3A = 36W, the story if different.
The problem is efficency of solution.
The high side switch is transistor, which have 2V drop voltage, this is make high lost power when switching or conduct.
Normally eff of solution is 80%, so the rest lost power is most on IC arround 20% x 36W = ~7W.
The package of IC is not feed to release this power, so the temperature of IC rise up and burn IC.
So, before you select solution with monolithic IC, you must check eff of operation point, maximum dissipation power, temperature rise over each W lost power.
After that you have to take care output ripple, eff of system, step load responde, noise radiate, life time of capacitor, switching frequency, inductor & capacitor, compesation loop, layout, protection, temperature, efficency, cost.
LM2596 also don't have external compensation loop to optimize for each configuration.
You can consider TPS54360 IC.
 

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