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If you need low cost switching regulator then try thisConsider discreet circuits like "The Black Regulator" Input: 10v to 18v output +5V, +12v 70mA to 300mAhttp://www.romanblack.com/smps/smps.htmThe input voltage can go higher by changing some parts in the circuit.
High voltage use I have had some inquiries re using the Black regulator for high voltages, ie 40v up to maybe 120v or so. High voltage input is one area where this circuit can really beat the dedicated smps chips (or 78xx regulator chips) as these chips rarely accept input voltages over 30v or 40v. If you want to use the Black regulator for high voltage circuits I suggest the following: Make sure Vce of Q1 and Q2 is rated 50% higher than input voltage Use a darlington for Q1, so you can use a high value resistor for R2 to keep R2 dissipation low D1 must be Vr rated at 50% higher than input voltage, a schottky probably won't do. Try a 1N4937; 600v 1A fast switching diode Increase RZ resistance Reduce C1 and C2 as RZ was increased A resistor in series with C2 may be needed Retuning of the C1:C2 ratio will be needed, use a much smaller C2 R2 and RZ may need to be 0.5w or 1w types - check heat Use a fuse on circuit input!
the datasheet says the 7805 can take a maximum input voltage of 35-40v... wow, thats heaps of wasted energy!