T
treez
Guest
Hello,
I am designing a 3W boost converter to drive LEDs. (its an emergency LED light, which comes on when the primary power source fails)
Vin is a 3V6 battery. (three 1V2 NiCd cells)
It must have output short circuit protection.
Do you know of a very quick way to turn off a series PFET in the 3V6 rail, when a short circuit is detected?
There is also a 10V internal rail which i could use to power such short circuit protection circuitry. (the 10V rail comes from a micro boost converter which draws from the 3V6 battery)
I am thinking of doing something like a series sense resistor in the 3V6 rail, and "reading" this with a differential opamp (powered from the 10V rail) , and then the output of this feeding into a comparator which somehow switches off the series PFET, so that the short doesnt drain down the battery.
I am thinking that if the short draws say a 1ms, 40A spike out of the battery before the PFET gets switched off, then thats bad but not too bad?
...anyway, the differential opamp will be inaccurate due to common mode issues....but then who cares?......i am not looking for accuracy, i am just looking to detect dirty great big currents........am i on the right tracks here?
I am designing a 3W boost converter to drive LEDs. (its an emergency LED light, which comes on when the primary power source fails)
Vin is a 3V6 battery. (three 1V2 NiCd cells)
It must have output short circuit protection.
Do you know of a very quick way to turn off a series PFET in the 3V6 rail, when a short circuit is detected?
There is also a 10V internal rail which i could use to power such short circuit protection circuitry. (the 10V rail comes from a micro boost converter which draws from the 3V6 battery)
I am thinking of doing something like a series sense resistor in the 3V6 rail, and "reading" this with a differential opamp (powered from the 10V rail) , and then the output of this feeding into a comparator which somehow switches off the series PFET, so that the short doesnt drain down the battery.
I am thinking that if the short draws say a 1ms, 40A spike out of the battery before the PFET gets switched off, then thats bad but not too bad?
...anyway, the differential opamp will be inaccurate due to common mode issues....but then who cares?......i am not looking for accuracy, i am just looking to detect dirty great big currents........am i on the right tracks here?