I'm trying to replace a LM7805 fixed 5v linear voltage regulator and the two caps which support it on a PCB, with a switch mode regulator. This regulator will have to drop multiple volts (3s Li-Ion or 9s NiMH mostly) down to 5v. Current demands are small, around 110-140ma (drawn from the battery, using the LM7805). The LM7805's get way too hot for me and are inefficient so need to go.
I can build the LM2595T-5.0 circuit on national's datasheet, 5v, 1a switching reg. Parts cost is about £7 ($11US)
but i can buy a 5v UBEC (switching regulator for RC models) based on the LM2596T-5.0 for $6 shipped free.
My problem is, that's a 3 amp regulator - national's datasheet says the ICs have no minimum current demand, but is it efficient to use a 3 amp reg to power 75ma? would a 1a be more efficient? it makes it a little easier using the bought in UBEC in one sense but harder in another so it's a question of which is better electronically considering the small demand.
I've googled for this before signing up here (hi, by the way lol ) and on one site it seemed to be suggested that the 12v-USB or mains AC-USB charging adaptors that have a usb socket on the front might be a cheap source of 1a switching regulators.. thoughts?
I can build the LM2595T-5.0 circuit on national's datasheet, 5v, 1a switching reg. Parts cost is about £7 ($11US)
but i can buy a 5v UBEC (switching regulator for RC models) based on the LM2596T-5.0 for $6 shipped free.
My problem is, that's a 3 amp regulator - national's datasheet says the ICs have no minimum current demand, but is it efficient to use a 3 amp reg to power 75ma? would a 1a be more efficient? it makes it a little easier using the bought in UBEC in one sense but harder in another so it's a question of which is better electronically considering the small demand.
I've googled for this before signing up here (hi, by the way lol ) and on one site it seemed to be suggested that the 12v-USB or mains AC-USB charging adaptors that have a usb socket on the front might be a cheap source of 1a switching regulators.. thoughts?
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