Switching supply units used today are of light weight and compact design, but also susceptible to errors due to the incorporated electrolyte capacitors. Film capacitors would have much longer service lives. However, they need up to ten times more space. Scientists of KIT's[*] Light Technology Institute (LTI) have now developed a digital control method for use of film capacitors that need slightly more space only.
The control method runs on a microprocessor integrated in the supply unit and detects disturbing environmental impacts, such that e.g. higher voltage fluctuations can be balanced. Hence, storage capacitors of reduced capacity are sufficient. Michael Heidinger, LTI, summarizes the advantages: "Use of these film capacitors eliminates the main cause of failure of power supplies, i.e. electrolyte capacitors. Depending on the design, service life may be increased by a factor of up to three." The result is a much reduced maintenance expenditure.
This one is digital.
[*] Karlsruhe Institute of Technology.
(Score: 2) by RS3 on Friday May 17 2019, @12:25AM
Great post! Way back in the day (80s) I had gotten a little involved with 4-phase step (stepper) motors. Very simple drive circuits, torque dropped off quickly as RPM rose, etc. Then mid-90s was asked to evaluate and implement a Parker-Hanfin (sp?) "CompuMotor" step motor controller. They used very high voltage (200+) but pulse-width modulated, to drive the motor to insane speeds, rock-solid torque, no missed steps, and "micro-stepping" - holding armature between magnets by varying coil currents. All done by microprocessor control, sensing and analyzing winding amps, back-EMF, etc. Geeky, but I was quite impressed. (To get the really insane speeds you had to run an "autotune" routine, and they warned you it might tear up an attached mechanism.)
Much more recently I installed some industrial motor controllers (slang term: "freq drive" or just "drive"). They take 120 VAC, voltage-double rectify, filter, and 3-phase "H-bridge" drive 3-phase AC motors, all using a microprocessor, sensing winding current, back-EMF, etc. These were for 3 HP pumps. By default they'll only drive the motor up to 60 Hz (USA), but you can easily reprogram them to go much higher and run the motor much faster than stock, if the load can take it. I was stunned at the size of the thing- maybe 2" x 3" x 6", and no discernible heat. So it's not a stretch to control a switching supply transformer this way too.
And they're using this for residential water well pump motors- doing away with the storage tanks (big wet storage capacitor!) and maintaining pressure. (I'm not sure I like it- gotta see the power used in standby / maintain pressure...)