Programmable power supply.
The iOS Power Supply is intended for use by electrical engineering students to bring their creations to life. We have designed a two-channel, electrically isolated, programmable power supply with an output range from 0V to 24V @ 0A to 3A, and two dedicated USB charge port controllers. With our dependency on smart phones these days, we focused on the ability to drive our electronics from our mobile devices through an iOS app with Bluetooth connectivity. There is also an onboard TFT (touch screen) display that can be used to drive the outputs. The design features a robust enclosure built with user safety in mind and US standard plugs for all external connections.
Many of our devices are sensitive to noise. To deal with this requirement, we chose a sophisticated hybrid switching-linear topology to drive the output lugs. The design first processes 120VAC mains through a high efficiency torroidal transformer and full bridge rectification circuit with an RC low pass filter. The main current path, and the control current path are fed through two parallel channels from there.
The main current path undergoes DC-DC step down through a 95% efficient buck regulator before being channeled through a bank of three linear regulators and then to the output terminals. The Buck regulator leads the output set point by 1.6 volts in order to minimize the power losses and heat gain generated by the linear voltage regulators. It does this through a complex network of CMOS circuitry that provides the needed stability and accuracy to the back feed pins on the buck regulator IC.
The control current path is fed through three channels of DC-DC 95% efficient buck regulators. One channel is dedicated a raspberry pi microcontroller and all sensor and logic circuitry, while the other two channels drive separate USB DCP outputs. These dedicated charge port controllers can drive up to 2100mA and feature an adaptive overdrive to produce additional current for power hungry devices like tablets that require more than the typical 500mA.
Some minor bugs exist in the design to date. However, one channel is completely functional and can be driven with the raspberry pi controller. The raspberry pi functionality was implemented flawlessly and all expected functionality through its outputs and ability to communicate with external devices and system are as expected.
We have hopes of perfecting this design before the start of fall term 2020 with some extra icing on top. We will implement a bridgeable connection that will allow the user to drive the outputs to 48V @ 3A or 24V @ 6A with CMOS circuitry driven by logic that is already programmed into the pi.