Designing 0-30V half-bridge PSU from scratch - need guidance - Page 1
Forum section: electronics / projects

author: FilipCichowski
author_rank: Newbie
timestamp: April 25, 2025, 10:29:30 am
content: I decided to design symmetrical 0-30V 10A power supply for the sake of learning.My experience in power electronics is limited - I successfully designed working SCR rectifier controlled by Arduino & repaired tens of UPSs and inverters.I know this process will require a lot of calculations so I'm going to include Mathematica notebooks. Everybody will be able to reuse them just by changing variables values. It will by my gift for this awesome communityI chose half-bridge topology because it seems reasonable for 300W PSU.I would like to use SG3525 PWM controller because it's well understood and I consider it to be good starting point.My current topology block diagram is included as an attachment.I've got a few questions.1. Are there any disadvantages of using common rectifier for both main & auxiliary power supplies?2. Should I rather use Arduino for sending over current signal to SG3525 or choose analog comparator controlled by digital potentiometer? How can I prevent this circuit in case of Arduino failure?3. Should I control voltage directly from Arduino or use digital potentiometer for doing so like on my diagram?After receiving your responses I will design auxiliary PSU.Thank you in advance for your help.

author: FilipCichowski
author_rank: Newbie
timestamp: April 25, 2025, 11:04:40 am
content: I actually have an idea how to trigger OCP in case of Arduino failure.I can just use pull up resistor connected between Vref of SG3525 and pin 10. Arduino need to pull down pin 10 through any BJT. If Arduino is OK - the circuit works. If it fails - the circuit stops working.

author: moffy
author_rank: Super Contributor
timestamp: April 25, 2025, 11:15:00 am
content: You show the Arduino connected to the live side, that's generally not desireable because switches etc which are connected to the Arduino will also be connected to the live side. Better to have the Arduino working from an isolated supply and use isolation ICs to talk to the live side.

author: FilipCichowski
author_rank: Newbie
timestamp: April 25, 2025, 01:04:12 pm
content: Good catch, so I will use opto's for isolating digital potentiometer and switching SG.Power supply is isolated.

author: FilipCichowski
author_rank: Newbie
timestamp: April 28, 2025, 05:59:55 am
content: I started working on those Mathematica notebooks mentioned earlier.Here's what I created so far. Notebook for flyback is almost done.https://github.com/FilipCichowski/PowerElectronicsMathematicaNotebooks

author: moffy
author_rank: Super Contributor
timestamp: April 28, 2025, 10:11:53 am
content: It looks like you are monitoring the half bridge current into the Tx, normally one monitors the output current of the supply and limits that, perhaps you should look at the schematics of some switch mode supplies and see how they do things.

author: David Hess
author_rank: Super Contributor
timestamp: May 02, 2025, 09:04:36 am
content: You have drawn a half-bridge inverter rather than switching regulator. Where are the output inductors?I would never implement the current limit through the digital control. If the Arduino fails, so does the current limit.