Power Supply Unit
The main purpose of the PSU is to take power from the solar cells on the sides of the satellite and store it in the batteries as well as deliver it to the other subsystems of the satellite on a 5V power-bus and protect these users from latch-ups caused by radiation. At the picture below the basic architecture of the PSU is shown, however without the MCU (PIC 16c774) that controls the PSU.
The solar cells: The solar cells are triple junction GaAs cells from EMCORE with a efficiency of 28% and a maximum power point of at about 4.2 V.
The batteries: The batteries are 4 Lithium-Ion polymer cells
with a capacity of 940mAh each, giving a total capacity of almost
4Ah. The batteries are connected 2 and 2 is series and each string has
got a protection circuit (UCC3911) to ensure that the batteries does no become over or under charged.
The converters: For the step up in voltage from the solar cells to the batteries a standart boots-converter is used and it is controlled by the MCU which runs maximum power point tracking (MPPT) on it. For the step down from the batteries to the power bus a buck converter from Maxim (MAX1744) is used.
Design space (click to enlarge):
- New Documentation -
By 02gr733 - a updated worksheet:
- Old Documentation -
Please notice that both the follwing reports are outdated and both contains some minor and major errors.
By PED9-17c - the complete report divided into chapters:
Analog Power Supply.pdf
By 01gr509 - the complete report in one file: