Smart and flexible capacitor charger for warm environments
A studio camera flash system being developed by Eascal AB needs a capacitor
charging power supply (CCPS) that can work in a hot environment without
problems and also not emit too much heat itself. The CCPS needs to be able to
operate from battery power as well as net power, so called off-line, and to
charge a capacitor to between 0-400 V.
Most power supplies do not act upon a rise in temperature until it overheats
and shuts down or goes into fail-safe mode where they stop delivering power.
The aim of this thesis is to investigate how a smart power supply which
features a micro-controller can change the behaviour of the unit or the user
so that heat emission is reduced if needed in order to avoid overheating. The
unit will be allowed to deliver less power in this mode.
Starting the project was the information gathering phase where a lot of
different kinds of power supply topologies were investigated and evaluated to
find the most suitable. A flyback converter was chosen for the battery driven
charger and a non-inverting buck-boost converter was chosen for off-line
Following the final choice of topology, simulations were made to ensure that
the power supply of choice would live up to the expectations and to specify
the ingoing components.
After the simulations were to satisfaction the prototypes were built to
verify the simulations, for testing and evaluating proposed techniques for
regulating the heat emission of the unit.
The sought after performance of the prototypes was never reached due to lack
of time and a need for better components that was not available. However the
simulations showed that the wanted performance was within reach and this was
verified by the worse performing prototypes living up to their simulated
counterparts. No actual physical work was done with the heat control, this
was conducted by theoretical reasoning and calculations. Results showed that
with a micro-controller the suggested chargers would be able to regulate
their heat emission by making changes to the charging profile or increase
dead-time between charge cycles.
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