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What does mean "over voltage protection" in AC/DC

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VladZ

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Pease explain me what does mean "over voltage protection" in in AC/DC switching adapter characteristics ?
For example I see the following characteristics:

VOLTAGE : AC INPUT 90Vac TO 264Vac, FULL RANGE
OUTPUT REQUIREMENTS:+15 V, RATE LOAD 2.2 A
PROTECTION :
OVER LOAD PROTECTION : AROUND 150 % RATE LOAD AT 115Vac (230Vac).
OVER VOLTAGE PROTECTION : RANGE FROM 16.5 TO 19.5VDC.

As I know switching adapters can drive hard loads. Does mentioned above
mean that on weak loads I will abtain 16.5 TO 19.5VDC, although the nominal output is +15V?

Thanks in advance
vladz
 

goodboy_pl

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About over voltage protection:
there are two type of it; primary side and secondary side.
in primary side, it is necessary to check input voltage of the SMPS (after rectifier and input Cap.) and turn off the SMPS if voltage is over a predefined voltage level (for example 370VDC or 265VAC for mains voltage) to protect the switches against over stressing or permanent damage!
in secondary side, normally the output voltage is determined by feedback network (15VDC for your application) but what happens if the feedback does not work truely? (for example due to aging opto coupler opens the loop and does not transfer the error signal to primary side), in this case the output voltage will go higher than wanted one, which may damage your load. thus it is necessary to use a circuit to monitor the output voltage and if it is higher than a threshold, short it to ground to protect the load. there are several solution for it from integrated to discrete. in discrete realization of circuit, the output voltage is compared with a zener, if it is greater than an SCR is trigged to short output.(remember that for doing this it is necessary to include a current limiter in circuit to protect SCR itself!)
also there are other protection against undervoltage in primary and secondary.
in primary for controlling peak current of switches and in secondary for protecting the load from malfunction(in logic circuit specially)

for more info refer to following page 97:

http://www.onsemi.com/pub/Collateral/HB206-D.PDF

BEST!
 

VladZ

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Thank you very much !
Your link is very useful

best regards
vladz
 

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