Best way to convert 6V to 5.5V
my goal is to design USB charger for my phone/tablet when I'm not around power grid. I've used LM317 setup with 12V 5Ah SLA battery but it does not provide enough capacity due to the power dissipation of LM317.
*12V - 5.5V = 6.5V * 700mA = 4.55W ~ 5Watts are being lost to heat.*
I need to convert 6V voltage from battery to around 5.5~5.6V (AC USB charger voltage at 0.5A load) to get much more efficient charging and to decrease battery weight as half voltage at same capacity means half the weight.
I've tried designing a OP-Amp regulator with MOSFET but the Vgs threshold is just too high for opamp to turn it on and it's only working on Vcc >= 8V thus increasing heat losses again.
my goal is to design USB charger for my phone/tablet when I'm not around power grid. I've used LM317 setup with 12V 5Ah SLA battery but it does not provide enough capacity due to the power dissipation of LM317.
*12V - 5.5V = 6.5V * 700mA = 4.55W ~ 5Watts are being lost to heat.*
I need to convert 6V voltage from battery to around 5.5~5.6V (AC USB charger voltage at 0.5A load) to get much more efficient charging and to decrease battery weight as half voltage at same capacity means half the weight.
I've tried designing a OP-Amp regulator with MOSFET but the Vgs threshold is just too high for opamp to turn it on and it's only working on Vcc >= 8V thus increasing heat losses again.
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