Sometimes you come across a circuit that is just cool. This is a switching regulator for a 7805 that uses components that cost not much more than a 7805. But allow for the fact that it doesn't get hot and so doesn't need a heatsink, and it costs less.
All credit to the author Roman Black http://www.romanblack.com/smps/smps.htm
It is so simple I just had to build one. In fact, I needed something like this anyway because solar power is expensive and it seems crazy to throw it away as heat. SMPS are great - feed in 18V at 20mA and you magically get 5V at 60mA.
I have just completed one on the protoboard and it works just as described. Regulation varied about 0.2V depending on the load. There is no ripple at all I could see on the scope trace.
This could be perfect with a 5V supercap because the solar volts are not critical and can vary over a wide range. The quiescent current is going to be at least the current drain through the 8k2 but there might be scope to use a 78L05 equivalent for the reference.
I'm still working through Mr Black's website but he has some other nifty circuits, including a self turn off circuit for a pic/picaxe.
All credit to the author Roman Black http://www.romanblack.com/smps/smps.htm
It is so simple I just had to build one. In fact, I needed something like this anyway because solar power is expensive and it seems crazy to throw it away as heat. SMPS are great - feed in 18V at 20mA and you magically get 5V at 60mA.
I have just completed one on the protoboard and it works just as described. Regulation varied about 0.2V depending on the load. There is no ripple at all I could see on the scope trace.
This could be perfect with a 5V supercap because the solar volts are not critical and can vary over a wide range. The quiescent current is going to be at least the current drain through the 8k2 but there might be scope to use a 78L05 equivalent for the reference.
I'm still working through Mr Black's website but he has some other nifty circuits, including a self turn off circuit for a pic/picaxe.
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