Ampere

Ampere

Ampere is a 4 channel variable bench supply that is designed to be as minimal as possible while also providing high precision voltage and current regulation. This design encompasses a 140W USBC-PD power input, 2 buck-boost converters and 2 LDOs to provide options for smooth and quiet output voltages and currents as well as raw power to whatever is downstream.

This board was created with the intention of streamlining PCB workflows at home without spending that much money on a laboratory grade power supply. It adds features such as USB communication so that a standard PC can talk to this board and monitor outputs while also changing them and providing some waveform generation.

How does it work?

Ampere relies on a STM32G474 chip to orchestrate and control all the power path devices via I2C. This is very useful because it allows a single pair of traces to practically talk with the entire board. However, Ampere does use 3 I2C channels for increased reliability and just ease of routing. The STM32 is able to control 2 buck boost converters, the TPS55289s over I2C to output a voltage up to 22V and an amperage up to 8 amps. This is achieved by stepping the voltage up by 10mV (which is internally supported by the TPS55289). For further precision, each buck-boost converter has a secondary current and voltage sensor chip, in the form the INA238. The INA238 is a 16 bit ADC that also communicates over I2C, offering very high precisions for current and voltage monitoring. This is used in conjunction with 10 milli-ohm current sense resistors, which let the board accurately tell if the output voltage and current is what we think it is. This info will then be run into a PID loop for more dynamic control over the outputs of the buck-boosts.

The MIC29302s that are used branch off of the 2nd TPS55289 and are able to dynamically control their outputs as well. They also use a INA238 on the output and a I2C DAC to vary the feedback that goes into their internal logic circuitry, tricking it into trying to regulate their output to the reference voltage and thus resulting in a voltage that can be altered.