I want to make a Bench power supply unit based on:
For initial AC to DC conversion - ATX PSU (Enermax EG365AX-VE 350W) capable of providing 12V 26A
Internally Step up module for powering the below - one of below:
PSU output adjustable and provided by RD DPS5020 (input 6-60V, output 0-50V 0-20A)
For up to 10V application I would like to omit the step up module and power the DPS5020 directly from ATX. For higher voltages I want to manually switch to use step up module.
My first idea was to use 3P3T switch, but I could not find one that can safely handle 12V DC and 26A. Then I wanted to use the switch that would control 2 relays, but high current relays are very expensive. The third idea was to use high side switching with two Power MOSFETs.
N-channel MOSFET configuration: Link to the editable source
or alternatively P-channel MOSFET configuration: Link to the editable source
What MOSFETs should I choose? Are the following criteria safe:
Vds = min
75V 24V (12*2) (or should it be much higher?)
Id= min 30A (what if the mosfet would become warmer)
Vgs = +/-20V (I will ensure that the mosfet is fully open with Vgs=12V) - However as I have the ATX psu, I could easily use 5V or even -12V, - 5V.
To minimize the power loss (heat) the Rdson should be low.
Each mosfet won't switch frequently (and most probably not under load), as it would switch its state only when SW1 is flipped. Can I disregard then the switching power losses, so I should care only about conduction losses, witch would be P=IIR_dson.
IRLB8314PbF (30V, 130A, 2.4mOhm, 125W)
IRFB3607PBF (75V, 80A, 9mOhm, 140W)
IRFB4410ZPBF (100V 97A, 9mOhm, 230W)
How about the power dissipation and safe operation area? The conduction losses even for 26A would be max 6-7W.
To make sure that when then M2 is providing the 12V and the Step up converter is off there is no voltage on the + output pin I added the D1 diode, is it sufficient protection?