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P31u Functionality

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This document contains confidential data and is not intended to be shared outside of SAGE!

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🚧 This document is still being actively worked on and is subject to change. 🚧

Authors
  • Kai Berszin
Responsible
  • Gianluca Ielpo
  • Kai Berszin
Last Updated10/12/2025, 12:48:54 PM
Last AuthorKai Berszin

Scope​

This page describes the functionality of the GomSpace P31u power conditioning unit.

Block Diagram​

P31u Block Diagram

MPPT​

The P31u contains three individual photo-voltaic input channels each having its own power-point setting.

  • Channel 1: P6 and P5
  • Channel 2: P4 and P3
  • Channel 3: P2 and P1

To capture the exact maxium power-point at all illuminated cells when MPPT is employed, each of the three solar panels of the SAGE CubeSat is to connected to a seperate channel.

The photo-voltaic input converter is designed to handle up to 2 A input current. Each series string must have a protection diode in series in order to avoid non-illuminated cells from drawing current from illuminated ones.

Overcurrent Detection​

System wide​

The overcurrent detector for the system has a time before latch-off depending on the current system load IsysI_{sys}.
The full load of Isys,max=I_{sys,max}=???

P31u Time Before Latchoff

Load specific​

The output switch shuts off the power to a load when an OCD occurs.
A fault condition is asserted whenever the output current exceeds current limit for more than 28ms.
Once the output shuts off, it remains off until either the faul load is removed from VOUT or until the p31u cycles automatically after 500ms.
If the fault is still present, the cycle will repeat.

Software Latch-up Protection​

It is possible to enable software latch-up protection for the 6 user controllable output channels.
If a channel consumes more than the set current limit, it will be turned off. After 5 seconds, it will automatically be turned on again.
The current limit is a "soft" limit, meaning that the current limit is compared to the average current consumption over time calculated as an Exponential Moving Average (EMA).
The gain parameter α\alpha for the EMA algorithm is configurable:

s0=x0st=αxt+(1−α)st−1,t>0\begin{align*} s_0 &= x_0 \\ s_t &= \alpha x_t + (1-\alpha)s_{t-1}, \quad t>0 \end{align*}