High current Negative rail generator

[Kdent]

Hello

I am trying to design a circuit that runs off the 5v bus power of a USB port. In order to achieve more then +/-2.5 volts I figured a negative rail generator would be the most adequate solution.

After some research more IC can do this very easily with minimal external components, however current is limited to 10-30mA. My circuit needs around 100-150.

One product that I know does this is the Schiit Fulla headphone amplifier. It generates +/-5v from a USB port.

Any suggestions are greatly appreciated

 

[Kdent]

bump

 

[rayma]

This is a good but more complex circuit, non-isolated.
Low Noise LT1614 DC/DC Converter Delivers –5V at 200mA from 5V Input | Analog Devices

This one is unregulated but isolated, so it can be used in either polarity.
Blocked

 

[indra1]

MC34063 dataheet fig. 11 shows a voltage inverting schematic. Need to recalculate R1.

 

[Kdent]

MC34063 dataheet fig. 11 shows a voltage inverting schematic. Need to recalculate R1.

Datasheet by which manufacturer? The two I see is On Semiconductor and TI.



Thanks,


Kaden

 

[mchambin]

Hello

I am trying to design a circuit that runs off the 5v bus power of a USB port. In order to achieve more then +/-2.5 volts I figured a negative rail generator would be the most adequate solution.

After some research more IC can do this very easily with minimal external components, however current is limited to 10-30mA. My circuit needs around 100-150.

One product that I know does this is the Schiit Fulla headphone amplifier. It generates +/-5v from a USB port.

Any suggestions are greatly appreciated

I have seen using a powerful op amp to create a virtual ground at V/2 to give a dual voltage +V/2 and - V/2.

 

[as_audio]

But OP wanted "to achieve more then +/-2.5 volts", in other
words more than "a dual voltage +V/2 and - V/2" ..

 

[mchambin]

If strictly more than 2.5V, not equal......
Then he needs a DC DC converter.

 

[as_audio]

Yes, according to post 1.

 

[steveu]

inverting switches

There are many "inverting" switchmode regulators but most buck regulators can be wired to invert the voltage by making the normal output ground and the original "ground" the negative output. Some chips don't do this well and other do. There some chips designed for this purpose but the ones I have tried were very noisy. They were CMOS charge pumps like that used for 5V RS232 drivers, ie +/-10V from 5V. The attraction of the charge pumps is no inductor but I don't think it's worth it since charge pumps have a problem with current spikes. Attached is a buck mode regulator used for +5 to -5 conversion.

 

[astouffer]

You could go with a ready made module like this Cookies Required. Only $8.

 

[DUG]

nme0505dc to create -5V then regulate usb 5 to 2.5 and regulate the -5 to -2.5

Blocked

 

[indra1]

Datasheet by which manufacturer?

Sorry my datasheet is Motorola 1996 Rev 5. Simply look for a figure that says "Voltage Inverting Converter" on On Semi datasheet you can find.

 

[steveu]

The LM2596 can be used as I described in post #10 and the data sheet includes the schematic figure 18. This part is available on a completed buck converter module from several Amazon vendors very cheap. Converting these modules for voltage inversion will be easy, probably just connect the input ground to +out and take -5V from "ground".
https://www.ti.com/lit/ds/symlink/lm2596.pdf

https://www.amazon.com/DZS-Elec-Adj...ords=buck+regulator+ic&qid=1608164087&sr=8-34

 

[dgta]

Go to eBay and look through the many Chinese boost regulators. You can get almost any +/- voltage you want from 5V.

+-5V6V9V12V15V24V Boost Converter Module Positive Negative Durable Dual DC | eBay