Inspired by Dave's mini lab power supply project, I designed my own one.
It is going to be an open source project.
Since I'm not ready to prepare and publish all my design files, and the software part has not started yet, I posted this design here, rather than open source hardware section.
The design philosophy is simple, I just want to have something to convert USB 5V to any voltage from 0V to 15V.
Maximum output power is 5W, while maximum output current is 2A.
The design should be as small as possible, so that it can be used as a programmable lab power MODULE that fits in any projects.
Unlike Dave's LED display interface, I want it to be an OLED and USB dual mode device. It should be able to be controlled by CapSense Keys with OLED, or simply PC software.
Also, full isolation is required. Ideally it should be designed to meet UL/IEC60950-1 spec, but only functional isolation is acceptable.
My current design is a 3 stage converter. The first stage is a flyback isolator, and the second stage is a synchronous buck.
The third stage is a LDO, to provide a very clean output. This buck+LDO topology is both high efficiency and low ripple, if control loop is properly designed.
To make the design process more challenging, I designed my own primary stage gate driver and I decided to use full digital controller on all SMPS.
The first stage uses a voltage mode and current mode hybrid control algorithm, the second stage uses simple voltage mode algorithm, and the third stage is controlled by an opamp.
The attached is the schematic, in PDF and SchDoc generated by AD14.3.16. I'm now working on its PCB layout. Please give me some suggestions on this design.