From rectififer output of telecom equipments, 48V DC, I want to convert it to 12V DC. I'm considering this schematic:
Can this schematic convert 48V DC to 12V DC? Please recommend me for corrections.
- How much current will you be drawing ?
Have you considered a buck converter? Here's one that will take up to 75V in and deliver 12V @ 2.5A:
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1-2 A maximum.
You will burn 36V × 2A= 72W in that tip...
That is a lot.
If it can handle that (I did not check the data sheet), it will need a serious heat sink. It is also pretty wasteful.
And your base resistor is too small. (My guess is that your tip does not have a factor > 1000 current amplification)
I have had success connecting 48VDC to the input of a 'wall wart', well, the innards of one anyway, after the bridge rectifier on the input. I suggest you try a 12V wall wart, at worst it won't work. If it does work then you have a cheap way to get 12VDC from 48V.
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I did check the datasheet: it can disdipate 100W...
Current gain is max. 50...
Can you also keep the rectifier in place (accept the 1.2V loss)?
Then you can keep the housing intact...
First, max input voltage for the 7812 is 35V.
Even if it could handle 48V, you're burning off a lot of power, which is going to be heat.
Please don't spam the forum and post the same question in multiple categories.
Yes, I bypassed the rectifier to avoid the 1V2 loss, the thing is already being powered with a voltage below what it's designed for, no need to make it worse.
Should work up to 360V...
You should use a buck converter as suggested in post #3
Otherwise from 96 W you will waste 76 W in heat.
(48V x 2A = 96 W, 36V x 2 = 72 W )
So 80% wasted and a lot of heat, regardless of the LDO's or TIP's that you use. And regardless of the current.
The solution is to use a single a buck converter.
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Indeed, or more perhaps, but in this case we are talking about below its lower design input voltage.
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I want to convert the -48V from rectifier output of telecom equipment to +12V DC.
I'm considering the following schematic for that purpose:
The rectifier controller has -48V DC and +VE DC bus bar, the layout is pictured below:
How can I connect from busbar as an input to LM2576HV?
The 12V DC will be used to run microcontroller, sensor and boolean output (+5V)
I am sure that @PerryBebbington will know this. This will alert him to look at this post.
Indeed @Grumpy_Mike ,
I alread answered this question for the OP.
@mnhpias ,
Your two or more topics on the same or similar subject have been merged.
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Thank you.
@mnhpias ,
Your question in post #15 refers to -48V output from the power supply, which is correct for a telecoms power supply. Your schematic shows a +48V output, which is wrong for a telecoms power supply. What do you actually have?
The reply I gave you in post #6 will do what you are asking , including providing the necessary isolation to go for positive to negative earth. I had no difficulty finding a wall wart that would work with 48V input.
Do you really have a 20kW power supply with a 3 phase input? That's the kind of supply found in a public telephone exchange when they were electromechanical.
Basically I want to use LM2576HV or similar type switch converter, hence in schematic, 48V,but it's wrong. Input will be supplied from -48V power rail.
Yes the power supply is 20kW with a 3 phase input.
Is there any way to get input from -48V for LM2576HV? or any other recommendation for this purpose.
There are many switching type voltage regulators that will convert the voltages you desire, that have the footprint of a 7812 (SIP3). They are switching so they generate little heat. No heat-sink required. Most are greater than 90% efficient. Even the buck converter is a better choice. Look at the Traco Power TSR 0.6-48120WI. I have these on hundreds of projects and not one failure in 10 years.