I am building a +/-15V Power supply to power a sensor, the sensor draws 25mA. Unfortunately, I'm having some difficulty with it. The design is as follows:
- 6V AAA battery pack plugged into a DC/DC Boost Converter
- Boost Converter set to output 30V from the regulated output
- Output is split into +/-15V using Linear regulators (LM7815/LM7915 pairs)
- +/-15V and Ground is plugged into sensor
The boost converter I am using is rated for output voltages up to 37V:
https://www.jaycar.com.au/arduino-compatible-dc-dc-boost-module-with-display/p/XC4609
The 'data sheet' (if you can even call it that) can be viewed at: https://www.jaycar.com.au/medias/sys_master/images/9004196134942/XC4609-dataSheetMain.pdf
The circuit to split the 30V into +/- 15V has been adapted slightly from https://www.head-fi.org/threads/virtual-ground-regulated-and-rail-splitter-circuits.654485/
I have not included an LD1085 because the output of the boost converter is regulated.
The schematic is:
simulate this circuit – Schematic created using CircuitLab
I have used an LM317 regulator instead of the LD1085 Low drop out regulator. This was mainly due to price and what I had available. I have also used smaller capacitor values than what was quoted.
Simulating the circuit shows the correct values. However after building the circuit its not working properly.
But when I plug in the rest of the circuit the DC boost converter the screen turns off, I think its due to a short. The LM7815 gets proceeds to heat up, I think that it's trying to regulate from 15V to 30V.
The circuit itself is built on perfboard, and I ensured all connections were correct using a program called Fritzing. http://fritzing.org/download/
The circuit can be seen below
Best Answer
If you set your boost converter to produce precisely 30 volts (not 33 volts) then you have achieved the outer rails but not the mid rail. The mid-rail can be made with a single 15 volt regulator. I would choose a buck regulator for doing this because it will generate very little heat.
So, your isolated 30 volt output becomes +15 volts. Your isolated 0 volts becomes -15 volts and the buck regulator would produce a mid-rail of 0 volts.
It makes no difference if you regard these three voltage as 0, +15 and +30 OR -15, 0 and +15 - your circuit will not perform any differently.
Buck regulator idea. This one shows a 12 volt output but can be adjusted to provide 15 volts by altering R1 or R2: -
There are plenty to choose from.