I have a project (hobby not commercial) where I am trying to replace a pair of 18650 cells in series with a 12v power input socket and a voltage regulator circuit.
Requirements:
- Input: 12v (probably a laptop inline power supply)
- Load: black box heating circuit that requires 8.4 V and 6 A (would prefer to design for 8 A for safety) input
- Load pattern: Device pulses on for 30 seconds at a time, running no more than 2 minutes out of 5 (mentioning this because it leaves time for heat dissipation)
- Build Space: Entire regulation circuit with power socket needs to fit in battery cell space, 18mm by 65mm long with near zero air flow.
- Cost: under $15 (there is flexibility here)
I expected to find an existing regulator, similar to an LM338, that would support this but I can't find one on Digikey that supports > 5A. Can you point me to a single chip regulator that would work in this tight space? Would greatly prefer through hole for ease of building. I am considering whether I can push a single LM338 this hard. If it reliably self protects and only shuts off occasionally I can live with that.
I considered MOSFET options but I worry they will generate too much heat in this tight space.
I've seen circuits for paralleling two LM338's with 0.3 Ohm series output resistors and a current regulating feedback opamp to balance. Again I'm worried about the heat and inefficiency with pumping 6 amps through those resistors.
Any suggestions greatly appreciated. There has to be a chip out there I haven't found...
Requirements:
- Input: 12v (probably a laptop inline power supply)
- Load: black box heating circuit that requires 8.4 V and 6 A (would prefer to design for 8 A for safety) input
- Load pattern: Device pulses on for 30 seconds at a time, running no more than 2 minutes out of 5 (mentioning this because it leaves time for heat dissipation)
- Build Space: Entire regulation circuit with power socket needs to fit in battery cell space, 18mm by 65mm long with near zero air flow.
- Cost: under $15 (there is flexibility here)
I expected to find an existing regulator, similar to an LM338, that would support this but I can't find one on Digikey that supports > 5A. Can you point me to a single chip regulator that would work in this tight space? Would greatly prefer through hole for ease of building. I am considering whether I can push a single LM338 this hard. If it reliably self protects and only shuts off occasionally I can live with that.
I considered MOSFET options but I worry they will generate too much heat in this tight space.
I've seen circuits for paralleling two LM338's with 0.3 Ohm series output resistors and a current regulating feedback opamp to balance. Again I'm worried about the heat and inefficiency with pumping 6 amps through those resistors.
Any suggestions greatly appreciated. There has to be a chip out there I haven't found...