Voltage regulator that can deal with 80V DC in

Thread Starter

Robert Labrie

Joined Feb 15, 2019
1
I might get flamed to death for this, but google is turning up nothing. Because reasons, I want to be able to charge my phone off a greenworks 80V battery. The LM317 seemed obvious, but it's max differential is 40V. Anyway, I tried googling for something that'll deal with an 80V spread and run 2100 ma.

If anyone has any suggestions, I'd love to hear them. It's been a long time since I did analog circuits and I was bad at it then too.

Thanks
 

be80be

Joined Jul 5, 2008
1,961
The usb charging spec is 4.40 to 5.25 volts I'd shoot for 4.9 to 5.1 if it was me.

Here something to try the find you a 2 amp phone charger hook the wall side to your 80 volt DC bypass any line filtering first - and the rectifier
 
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dl324

Joined Mar 30, 2015
9,332
Missed the part where you wanted to charge a 5V device.

Besides being an inappropriate input voltage, you're going to have to dissipate a lot of power somewhere with a linear regulator. 75V @ 2A is 150W!!!!

You'd better use a switching regulator. You can use a power transistor and a zener diode to drop the input voltage to something whatever regulator you use can tolerate.
 

AnalogKid

Joined Aug 1, 2013
8,226
As above, a linear regulator would produce an impractical amount of heat. Also, an isolated switching power supply, even on making only 11 W output, is a significant design effort. The problem is that an 80 Vdc input is significantly lower than most small switcher designs in app notes, the ones that have transformers already designed and produced on the shelf. Better to purchase a commercial DC/DC module and put it in a suitable enclosure with all of the right cables and connectors.

https://www.ebay.com/itm/DC-DC-Buck-Step-Down-Module-Volt-Converter-6-80V-24V-36V-48V-72V-to-5V-6V-9V-12V/253496668342?hash=item3b059430b6:g:3vkAAOSwuxFYyQyb:rk:4:pf:1&frcectupt=true

ak
 

sparky 1

Joined Nov 3, 2018
32
I might get flamed to death for this, but google is turning up nothing. Because reasons, I want to be able to charge my phone off a greenworks 80V battery. The LM317 seemed obvious, but it's max differential is 40V. Anyway, I tried googling for something that'll deal with an 80V spread and run 2100 ma.

If anyone has any suggestions, I'd love to hear them. It's been a long time since I did analog circuits and I was bad at it then too.

Thanks
The question is good.
My suggestion is to improve the wording of your question.
A DC to DC step down converter with high efficiency, high voltage input of 80V and an output of 2A at 5V.
This search is done at a semiconductor website. The words translate into a parametric search.
The semiconductor parametric search allows sorting of the search results. The terminology has a steep learning curve
however it begins with familiarization and making logical choice based on evidence supporting your goals based on data sheets. Reduction of electrical noise over efficiency is my own personal choice for priorities in buying a step down.

https://www.design-reuse.com/articles/39498/choosing-the-best-dcdc-converter.html
 
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Papabravo

Joined Feb 24, 2006
12,695
@sparky 1 gives you a pathway to finding a module you can purchase. He mentions a learning curve for the terminology. I can tell from long experience, that curve is even steeper if you want to design and build your own modules. The requirements suggest that will will have to do some experimentation to find a suitable design. These circuits do not function well with prototype construction methods. They need to be put on a well designed PCB. Learning how to do this kind of layout and fabrication is a second learning curve. Seems like a great deal of aggravation for such a seemingly trivial application. If you want something to work while you are traveling then a charger that works in your vehicle is the way to go.
 

ian field

Joined Oct 27, 2012
6,539
I might get flamed to death for this, but google is turning up nothing. Because reasons, I want to be able to charge my phone off a greenworks 80V battery. The LM317 seemed obvious, but it's max differential is 40V. Anyway, I tried googling for something that'll deal with an 80V spread and run 2100 ma.

If anyone has any suggestions, I'd love to hear them. It's been a long time since I did analog circuits and I was bad at it then too.

Thanks
There is (or was) a high voltage 3 terminal regulator which is pretty much a 317 with a much higher voltage differential (can't remember the number though).

That voltage differential at any worthwhile current would be a fair bit of dissipation. Switch mode is well worth considering, there is a non isolated mains buck that will probably work down to 80V. some LED bulbs use non isolating buck - but the configuration options are limited.
 

ian field

Joined Oct 27, 2012
6,539
There is (or was) a high voltage 3 terminal regulator which is pretty much a 317 with a much higher voltage differential (can't remember the number though).

That voltage differential at any worthwhile current would be a fair bit of dissipation. Switch mode is well worth considering, there is a non isolated mains buck that will probably work down to 80V. some LED bulbs use non isolating buck - but the configuration options are limited.
I'm aware of that, and it might still be available - the number of the one I'm on about isn't even vaguely similar to; "317".
 

be80be

Joined Jul 5, 2008
1,961
What I told him in my post is laying around most homes its a phone charger.
has similar chip as XL7056 just bypass the bridge.

These things take the supply voltage and change it to DC with 4 diodes and 3 caps
If you bypassed that and gave it raw DC it looks like it would work.
 
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ian field

Joined Oct 27, 2012
6,539
What I told him in my post is laying around most homes its a phone charger.
has similar chip as XL7056 just bypass the bridge.

These things take the supply voltage and change it to DC with 4 diodes and 3 caps
If you bypassed that and gave it raw DC it looks like it would work.
I'd leave the bridge in - it probably won't do any harm. getting the wires wrong way round without it might though.
 

danadak

Joined Mar 10, 2018
3,701
Use a 20V - 30V zener in series with input to a LM317HV ?

Calc zener dissipation to make sure it operating within its Tjmax specifications.

But this approach, albeit simple, wastes a lot of energy. Switching approach is
the way to go. Design green, the planet will benefit.


Regards, Dana.
 
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