emergency supply

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Valvepayal8

Joined Dec 17, 2019
5
I want to design circuit which automatically switch the load from SMPS output to battery which is also charged though SMPS output using charge controller when SMPS mains input is off.please find attached Block diagram.i have a circuit of AC Zero crossing detection.can i use that circuit for this application and if yes then how?
 

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AlbertHall

Joined Jun 4, 2014
10,400
Looking for a missing zero crossing pulse would be a useful way of signalling that the mains supply has failed then use that to switch supplies using either MOSFETs or a relay. With a relay there will be a short time when there is no supply to the load. Depending on the current required, that could be covered by a capacitor on the load input which could support the load current until the relay has finished switching.
 

Reloadron

Joined Jan 15, 2015
5,646
I assume a 24 VDC system including a 24 V battery. What you don't mention is the current? Consider the load current and allow some overhead. Then decide how long your load needs to be supported on the battery? Are you looking to build or buy a turn key solution?

Ron
 

Tonyr1084

Joined Sep 24, 2015
5,080
Either way, a 240VAC relay on the 230V line OR a 24VDC relay on the SMPS line. This shows a 24VDC relay.
1600872188698.png
With a relay there will be a short time when there is no supply to the load. Depending on the current required, that could be covered by a capacitor on the load input which could support the load current until the relay has finished switching.
That's a good idea. A cap across the load input should carry it through the switching of the relay.
 
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