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MOSFET Power Rail (Need second opinion)

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rolupusoru

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Hi,

I would like a second opinion on the design of the folowing power rail.



The logic behind this circuit is that during day time power from the Solar Cell is stored into the battery.Some of this power is also used to power the MCU and other power and battery management circuits.During night time power is supplyed from the battery to light an LED.For simplicity, management circuit and voltage probes are not included.

Because i need high efficiency due to limited solar power i used MOSFETS because of their low rDS.

My concern is PMOS Q1 that is connected with its body diode in the power path,something that is not very documented except here .This way the diode will provide reverse current protection when battery power is used.Management will then activate Q1 if enough sun power is supplied, shunting the diode and maximizing sun power efficiency. C/B PWR signal is what switches power source, so when night comes battery will keep the circuit alive.

I would like a second opinion if Q1 will work as expected(simulation says yes),no glitches or high resistance, though i read somewhere that if MOSFET current flows in reverse rDS will be much higher than rated value.


Thanks
 

RAJAT AGGARWAAL

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hey frn , one time i developed automated thing like this
and you have also mentioned that you are using mcu
so
1.you get solar cell's____ adc val
2.you get battery_____ adc val (use reference voltage)
3.add a big cap directly on solar cell, then make your mosfet switches your
solar cell current to your battery in appropriate duty cycle with a inductor
it can be bucking or boosting,,[helped me about 20 to 30 %in charging time]
according to your battery type(3v 4v 6v etc)
===now in this way you get control over your battery in right charge of voltage

and you can add tickle charging too,
and big cap helps when you have low lightnings
mcu check the voltage on cap
when sufficient it triggers the mosfet
inductor induces the current
and charges the battery even when your solar cell voltage <your battery voltage
:-D:-D:-D:-D:-D:-D:-D:-D:-D hope it helps
 

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