There are several sites for SMPS design to find every details, from schemctics design to EMI/EMC considerations, but there are very few sites about UPS!
I would like to know some details about UPS control circuity, especially the off-line type and the autoshutdown scheme via COM port when the battery is low.
Can anybody know any direct link?
Regards
The off-line type switches between the mains and the backed up supply with a relay or something when the mains goes out.
As to the autoshutdown schemes, google for linux drivers to see how they work.
This is the easy bit of the UPS.
Designing a UPS that will drive a resistive load is almost trivial.
A 12V-several hundred v inverter, and then a full bridge, for example, driven with a modified sine-wave.
This is simple - you get current only flowing out of your drivers, and it all just works.
The horribly complex bit is when you connect it to real-world loads.
Simple filliment bulbs will draw a large surge on switch-on.
99% of power supplies have capacitors in, and will also draw large surges on switch-on. Many will also have EMI suppression components that you have to charge on each voltage step, and not kill due to overcurrent.Then you've got motors. Large surge currents, inductance, meaning that when you switch off, you get current going the wrong way. Not to mention that in some cases, you can get the motor feeding back the current in the wrong direction at the wrong time, causing things to explode...
Making an efficiant UPS is near trivial. Making a UPS that can drive any load is trivial. Making a simple UPS is trivial. Making a cheap UPS is trivial. Making a reliable UPS is trivial.
Making one that does more than 2 of the above is hard. Doing 4 is really hard, 5 is really really hard.
So a laptop + drill scenario might kill the laptop .. ?
Anyway, how does one feed back-emf into the battery..?
It has to be designed to work with the 4 quadrants. Meaning voltage an current have to have any sign with respect to each other.
Rene
yes.
Probably as well as the UPS.
Not into the battery - that is the nicest option - if your circuit is smart enough if the load is trying to force the voltage higher than the specified voltage, it downconverts it and feeds it back into the battery. It can also just simply dump the charge back into the high voltage resovoir, or use voltage limiters of some sort.
To the best of my limited knowledge, all this stuff is considered trade secrets by the various manufacturers. not casually pried loose either.
How come does the nature of information these two applications in Power Electronics is different, one has a great deal of infomration in details while the other has very few?
Regards
joseph2k wrote:
Have something to add? Share your thoughts — no account required.
Ask the community — no account required