# Step down DC voltage with big current

#### meowsoft

Joined Feb 27, 2021
353
How to step down DC voltage from 48v to 36v with big current efficiently ?, for about 40a and more

#### Papabravo

Joined Feb 24, 2006
15,750
How to step down DC voltage from 48v to 36v with big current efficiently ?, for about 40a and more
Is that the input current or the output current? If the input is 48 V @ 40 A, There will be more current available on the output, but the price you will pay for this is the the output power will be less than the input power. If you are not careful it could be much less. Assuming a conversion efficiency of 85% you would get 1.632 kW of output power at 36 volts which would be a bit in excess of 45 Amperes. Is that what you had in mind? If so be prepared to open your wallet.

A quick check reveals that you might have to use 4 or 5 units @ $300.00 ea., in parallel to achieve that objective Last edited: #### Ian0 Joined Aug 7, 2020 1,891 Four 10A converters running in parallel. If you can offset the clocks by 90°, you can virtually eliminate the ripple on the 48V supply. #### ronsimpson Joined Oct 7, 2019 1,180 There a number of 36 - 48V to 12V at high current supplies used in electric carts to power 12V lights and radio etc. I know it is not what you want. Thread Starter #### meowsoft Joined Feb 27, 2021 353 Is that the input current or the output current? If the input is 48 V @ 40 A, There will be more current available on the output, but the price you will pay for this is the the output power will be less than the input power. If you are not careful it could be much less. Assuming a conversion efficiency of 85% you would get 1.632 kW of output power at 36 volts which would be a bit in excess of 45 Amperes. Is that what you had in mind? If so be prepared to open your wallet. A quick check reveals that you might have to use 4 or 5 units @$300.00 ea., in parallel to achieve that objective
It is possible to make step down module DIY ?, can you give some reference

#### Papabravo

Joined Feb 24, 2006
15,750
It is possible to make step down module DIY ?, can you give some reference
You want to design and build this thing as opposed to buying one. Do I have that correct? So have you ever done anything like this before?

#### crutschow

Joined Mar 14, 2008
26,992
What is the nature of the load?
If it's resistive, like a heater, you might be able to use PWM driving some MOSFETs.

#### meowsoft

Joined Feb 27, 2021
353
You want to design and build this thing as opposed to buying one. Do I have that correct? So have you ever done anything like this before?
Yes... I was made simple SMPS 12v 10a
also I was made inverter, using relay to turn on and off 120 times per second, just for fun

#### meowsoft

Joined Feb 27, 2021
353
What is the nature of the load?
If it's resistive, like a heater, you might be able to use PWM driving some MOSFETs.
No, it is for smart home system, load is LED lamp, phone charger, solenoid lock, etc
48v is for distribution, then stepped down at load points

#### meowsoft

Joined Feb 27, 2021
353
No, it is for smart home system, load is LED lamp, phone charger, solenoid lock, etc
48v is for distribution, then stepped down at load points
Also it is backed up with 48v solar panel and 48v battery, previously we use 36v, but no we decided moved to 48v system

#### crutschow

Joined Mar 14, 2008
26,992
48v is for distribution, then stepped down at load points
40A seems to be a lot of power for a Smart Home load point.

#### meowsoft

Joined Feb 27, 2021
353

#### meowsoft

Joined Feb 27, 2021
353
40A seems to be a lot of power for a Smart Home load point.
Also there is a 3D printer and laser cut at load point, so... 40a isn't really enough, meaybe we can upgrade to 50a later

#### andrewmm

Joined Feb 25, 2011
1,237
No, it is for smart home system, load is LED lamp, phone charger, solenoid lock, etc
48v is for distribution, then stepped down at load points
Good day

An interesting idea,

48V systems are around for house usage,
POE ethernet might be a good place to look.

The disadvantage of a 48 V DC system around a large area such as a house, is the power loss in the cables / the size of the cables needed.

if you have the same cable , if you half the voltage you end up with 4 times the power loss in the cables.
That's why most distribution systems use a relatively high voltage, to keep the resistance losses down.

For small loads then the cable loss is not to significant,

regarding DCDC convertors,

there are plenty around such as these
https://www.digikey.co.uk/product-d...s-inc/I6A4W020A033V-001-R/285-2503-ND/5878834

Alternatively , if you want to build your own,

look on the Ti.com or analog,com web sites, they have plenty of designs

Good luck

#### jlawley97

Joined Oct 5, 2019
15
Im just curious what your application is, solar panels?

#### Papabravo

Joined Feb 24, 2006
15,750
So you don't need a huge current at each load point. That makes a commercial solution easier to find. For your application I would recommend going this way.

#### meowsoft

Joined Feb 27, 2021
353
So you don't need a huge current at each load point. That makes a commercial solution easier to find. For your application I would recommend going this way.
Yes... but I mandatory need big current capacity to sychronize with solar panel that is 36v also wind turbines is 36v, and 36v battery bank

#### meowsoft

Joined Feb 27, 2021
353
So you don't need a huge current at each load point. That makes a commercial solution easier to find. For your application I would recommend going this way.
Do you know some efficient way ?, it is Chinese generic step down a good idea ?, it's 15a capacity with only about $60, input is 8v-70v DC and output is 10v-60v DC #### Papabravo Joined Feb 24, 2006 15,750 Do you know some efficient way ?, it is Chinese generic step down a good idea ?, it's 15a capacity with only about$60, input is 8v-70v DC and output is 10v-60v DC
It is basically the same technique used in early backplane computers run on +5 VDC. It was not uncommon for large numbers of original TTL circuit boards to require many 10's of Amperes from the 5 Volt supply. Some bright guys figured out that you could distribute +8VDC and put +5 Volt regulators on each board. Each regulator on a heatsink on the individual boards would do 1.5 Amperes. That is a way to do DC power distribution.