# How to unregulated change 48vdc to 12vdc, when 52vdc input 13.5vdc output

#### benderbanana

Joined Jul 8, 2015
3
I have a battery bank, 4 off 12 volt nominal. The battery voltage varies between 50 - 55 v. I am seeking a way to transform this voltage to 1/4 of the input.
All the buck converters have a (when set) fixed output. I want the output to vary with the input i.e. input 54 v output 13.5v.
I will be very please with any help.
cheers
jn

Joined Dec 11, 2013
54
what is the ampere rating of the low voltage?
you can use uc 3844 / uc 3843 chip based converter .do change voltage feed back to get your need.usually when it is set to a voltage then the chopper will correct for that. in your case the input and output must sampled simultaneously.
https://www.fairchildsemi.com/datasheets/UC/UC3843.pdf

you can also use series regulator along with an op amp and a high current transistor 2N3055 OR 2N 3773.

#### benderbanana

Joined Jul 8, 2015
3
I have a battery bank, 4 off 12 volt nominal. The battery voltage varies between 50 - 55 v. I am seeking a way to transform this voltage to 1/4 of the input.
All the buck converters have a (when set) fixed output. I want the output to vary with the input i.e. input 54 v output 13.5v.
I will be very please with any help.
cheers
jn
Thanks,I need about 300 mA. I am interested in any way I can solve this problem and if I can have a schematic, I will be pleased.
thanks

#### Dodgydave

Joined Jun 22, 2012
10,946
Can you be more accurate, what voltage input range is it, and what voltage output range do you need,?

#### benderbanana

Joined Jul 8, 2015
3
what is the ampere rating of the low voltage?
you can use uc 3844 / uc 3843 chip based converter .do change voltage feed back to get your need.usually when it is set to a voltage then the chopper will correct for that. in your case the input and output must sampled simultaneously.
https://www.fairchildsemi.com/datasheets/UC/UC3843.pdf

you can also use se
Can you be more accurate, what voltage input range is it, and what voltage output range do you need,?
ries regulator along with an op amp and a high current transistor 2N3055 OR 2N 3773.
Input voltage between 50 to 55 vdc, output 1/4 of the input voltage. i.e. when battery voltage is 50 v I would like output to be 12.5 v and
when input voltage is 53 v I would like the output voltage to be 53/4 = 13.25 v
I would like the output voltage to be proportional to the input to a ration of 1:4.
I need about 500 mA on the output.
The output voltage is an input to a relay driver which has 4 output ports which are set to different thresholds for drivinng
different micro relays to control different switches.
The relay driver I use can read voltages to two decimals.
Cheers, and thanks
jn

#### Dodgydave

Joined Jun 22, 2012
10,946
You can use a resistor divider and op amp buffer to feed a transistor output..