Design, on paper, a transformerless 300V power supply with a ripple of 1% or les

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a rectifier in serie with a zener (even better a transil) > used to drop the voltage so that only the peaks of the AC top waveform > come through, and lessed by ~300 volts. Care must be taken because if the > (230VAC case) RMS voltage can be anywhere from 210V to 250V, then it means > that the DC coming out of this circuit will have the same offset range > (eventually a fuse will be blown or, better, I'll use a polyswitch). > 100mA will have to be multiplied by the zener/transil drop > voltage, which (again, 230VAC case) will be, say, 300V: 30W! But anyway > this will only happen for a fraction of the 50Hz waveform, when the diode > conducts (probably much, charging a low voltage capacitor), so the average > power dissipation of this diode hopefully should still be acceptable.

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