Inverting Dc

Airskout · Mar 26, 2020

Hello all , I am working on a project and i've come to a roadblock. I am( just finishing university so please don't hate me ) looking for a component that can "invert" +5V to -5V . The numbers are examples but i am working with similar voltages. I haven't tried logical gates yet but might resort to . Any ideas welcome . The project is in smt so not huge components.

rjenkinsgb · Mar 26, 2020

Look at the MAX660 or ICL7660

Those are 8 pin ICs that work as capacitor charge pumps, and are designed to create low current negative supplies.

For a basic +5 to -5 converter you just need the IC and a couple of capacitors.
Data here:

https://www.ti.com/lit/ds/symlink/max660.pdf

dr pepper · Mar 26, 2020

If you want to be really basic you could even use a 555 charge pump circuit.

Diver300 · Mar 26, 2020

Are you wanting to transfer power like this?

Alternatively is it just a signal? That would be where you have for example as signal that might be 1 to 5 V and you want to make 1 volt in give -1 V out, and 5 V in give -5 V out, and you already have any supply voltage that you want.

Airskout · Mar 26, 2020

dr pepper said:
If you want to be really basic you could even use a 555 charge pump circuit.

This looks promising ill check it

Airskout · Mar 26, 2020

So small miscalculation i need it to run up to 12V cause of some displays i need to power
Ultimately i would like it to return the whole input voltage negative and to help with the answers atm i am using an LM317L capping the voltage to 10-12 V using a potentiometer with a variable input from 12-24 V and i want to be able to invert the output of the microchip to power other components

Airskout · Mar 26, 2020

Diver300 said:
Are you wanting to transfer power like this?

Alternatively is it just a signal? That would be where you have for example as signal that might be 1 to 5 V and you want to make 1 volt in give -1 V out, and 5 V in give -5 V out, and you already have any supply voltage that you want.

Ultimately i would like it to return the whole input voltage negative and to help with the answers atm i am using an LM317L capping the voltage to 10-12 V using a potentiometer with a variable input from 12-24 V and i want to be able to invert the output of the microchip to power other components

MaxHeadRoom78 · Mar 26, 2020

Will simply using a full wave bridge work?
I have used it for 'steering' bi-polar DC to a uni-polar source as well as AC as a universal interface.
Max.

crutschow · Mar 26, 2020

If you need any significant power, then you could use a switching regulator to get a negative voltage from a positive.
How much power do you need?

atferrari · Mar 26, 2020

Is it a signal or is it power?

MaxHeadRoom78 · Mar 26, 2020

Airskout said:
i want to be able to invert the output of the microchip to power other components

Invert is not always the same as reversing polarity!
Max.

Airskout · Mar 26, 2020

MaxHeadRoom78 said:
Invert is not always the same as reversing polarity!
Max.

Ok my bad on that one reversing polarity is what i meant

Airskout · Mar 26, 2020

atferrari said:
Is it a signal or is it power?

It's power maximum current about 100mA

MaxHeadRoom78 · Mar 26, 2020

So the bridge will do that.
What are the circuit details?
Max.

rjenkinsgb · Mar 26, 2020

A TC962 may do the job - it's a cross between a max660 and icl7662, up to 18V input and 80mA out?

Dynamic Product Page | Microchip Technology

That's the nearest I can find so far in a simple device..

Nigel Goodwin · Mar 26, 2020

I would suggest you post EXACTLY what you're trying to do, and why, and post some schematics - I don't have the faintest clue what you're after, and every one is just making wild guesses.

dr pepper · Mar 26, 2020

Some info:
**broken link removed**
100ma is on the high end current wise.
From what you said I'd be putting a simple smps together, however thats a reasonably demanding task.
This circuit generates a negative o/p:

https://www.electronoobs.com/eng_circuitos_tut10_2.php

Again not reccomended unless you have some experience.
As Nige says more info will lead to a better answer.

shortbus= · Mar 26, 2020

rjenkinsgb said:
A TC962 may do the job - it's a cross between a max660 and icl7662, up to 18V input and 80mA out?

Dynamic Product Page | Microchip Technology

That's the nearest I can find so far in a simple device..

Hi, would that chip work to keep a high side mosfet on continuous? Looks simpler than the normal charge pump to do that.

rjenkinsgb · Mar 26, 2020

shortbus= said:
would that chip work to keep a high side mosfet on continuous?

To keep a high side N-Channel FET on?

If the voltages are appropriate and you configure it in voltage doubler mode, it should be suitable - you could generate eg. 15V above the main circuit positive supply.

If the supply is higher than 18V, possibly put a 15V zener across the IC with positive direct and a resistor for the negative input?

Airskout · Mar 26, 2020

Nigel Goodwin said:
I would suggest you post EXACTLY what you're trying to do, and why, and post some schematics - I don't have the faintest clue what you're after, and every one is just making wild guesses.

Alright tomorrow i will post more info of the project so you can help me more i guess but you are already helping guys

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