Selecting IC for auto-switch to battery, in case of mains(dc) absent

Thread Starter

Vindhyachal Takniki

Joined Nov 3, 2014
558
1. I have a system, where:
a) Input SMPS is 11-14V, where it is used to charge battery with 2.5Amps and supply 12.5Amps to load also.
b) SMPS is used to charge lithium battery via LM3478 and dedicated charging IC.
c) When SMPS is present, it should supply to both load(12.5Amps) & charge battery. Battery should not be connected to load.
d) In case SMPS is absent, emergency , then load should shift to battery in that case only.

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2. Buck-boost LM3478 is for maintiaing voltage 12.6V & boost LM5155 for load voltage 12.3V/12.5Amps.

3. Precondition is:
a) Shift battery to load in case of smps absent only.
b) GND need to be common for all, so high side fet need to be chosen.

4. I checked Linear Technology LTC4414, it supply this diagram:
a) Can i avoid diode UPS840(or whatever equiavalent of 12.5A), since SMPS will not allow reverse current in any case?
b) It has P-channel mosfet for drive, my laod current is 12.5Amps, so is there any other IC or way where I can use N-channel on high side?
c) Any other better solution for this?


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crutschow

Joined Mar 14, 2008
25,392
a) Can i avoid diode UPS840(or whatever equiavalent of 12.5A), since SMPS will not allow reverse current in any case?
Yes.
b) It has P-channel mosfet for drive, my laod current is 12.5Amps, so is there any other IC or way where I can use N-channel on high side?
You could use a high-side N-MOSFET driver with a charge-pump to generate the gate voltage but that would require additional circuitry to control the switch-over.
What's the problem with using a P-MOSFET? They are not that more expensive than an equivalent N-MOSFET to handle that current.
 
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