Input 8-15V output clean 12Volts low ripple for sensor excitation

[Tedi]

Hello to all,

i think this is my first post to the community. I am sort of new member and I like this site a lot.
I am a student and electronics hobbist. Now to the point....

I need a low power, power supply with 12V output with low ripple.
The input is a lead acid battery 8-14Volts( with cut-off voltage at 10 volts ).
The 12Volts go to ina125p adc who reads a load cell.

Also in my project there is a microcontroller and GSM module and some other ICs that operate at 3.8V so there is already a LM2596 based power supply.
I want to control the new power supply from the microcontroller.
It is a free project so I can make any modifications I want. But my experience is limited in Power Electronics.

I need some boost help to continue.

 

[aliraza786]

you can use simple boost converter if your load is resistive then making a boost converter is really easy or you can find some dedicated IC like LM2596(this is actually buck) which can boost the voltage to the desired level.

 

[thylacine1975]

An inefficient and (comparatively expensive) solution is a small DC/DC converter followed by a linear regulator... (but it has the advantage of being tiny, foolproof and fast for a one-off project!)

If your design happens to have a convenient source of +5V, perhaps something like a 1 watt NMA05xx (https://www.digikey.com.au/product-search/en?x=0&y=0&lang=en&site=au&KeyWords=nma05) switcher followed by an low-power 78xx derivative linear regulator? (The NMAxx series are nifty, but suffer from 100's mV output ripple).

If you use a DC/DC converter with isolated bipolar outputs, you can connect the -ve output to the main ground and then linearly regulate the +ve output. This lets you use a lower voltage device (with correspondingly greater output current capability) than if you were to use only one side of the bipolar output [and ignore the other]. e.g. +5 -> [NMA0509] -> +18V -> [linear reg] -> +12V

 

[Tedi]

you can use simple boost converter

I think it is not good for this case senario. The battery is 14Volts( max voltage when fully charged ) and I want 12Volts. It is buck.

...find some dedicated IC like LM2596

If you read again my previous post I say that I already use it as a 3,8V regulator for the same project.
LM2596 is a step down converter.

What I look is a chip basically that can step up and down and have low ripple. Is it possible. Because I read in google that step up/down converters do not do that. I am not sure.

 

[D.A.(Tony)Stewart]

You can run the IA125P off 3.7 or battery directly.
The Power Supply Rejection Ratio or PSRR is 100dB in the audio range, so no additional regulator is needed. The IA also has a precision 2.5 V ref builtin. For RF noise on cable to load cell, you may need ferrite choke around cable. If using 12V, you can scale output down to ADC input range with offset to get precision in middle of range due to bandgap precision ref in IA.

For additional noise filter on the IA only uses 0.5 mA quiescent, so a series R of a few hundred Ohms and low ESR cap will filter and transient noise on Vbat> 100kHz. Where RC> 1ms.

 

[Tedi]

You can run the IA125P off 3.7 or battery directly.
The Power Supply Rejection Ratio or PSRR is 100dB in the audio range, so no additional regulator is needed. The IA also has a precision 2.5 V ref builtin.

I need 12V on ina125p because I use the built in 10V voltage reference. Load cell is 9-12Volts.

 

[KlausST]

Hi,

look for SEPIC DCDC converters.
maybe at www.linear.com.
They have an interactive search tool.
Other manufacturers also have interactive selection tools.

You don´t write how much mA is "low power".
Therfore i con only guess...

Maybe a SEPIC needs a minimum load current to operate in continous mode instead of burst mode or pulse skipping mode.
Continous mode is what you needfor low ripple / low noise. An additional post RC or LC filter may give you the desired result.

A linear post regulator is even better.
Maybe the sensor supply can be handled by an OPAMP.

**********

Besides the inductor regulators there are capacitive voltage doublers with integrated post linear regualtors. Maybe worth a look.


Klaus