There is one important difference between your schematic and the one in the data sheet - you show a ground connection, the data sheet doesn't. Also note that the supply is intended to be used to power line metering circuits which are by design completely isolated from any outside circuitry. They typically reside inside the box of the electricity meter which in turn is secure and isolated from outside contact. It is NOT intended for general use and you can NOT connect a ground to it. The circuit does not, and can not isolate you from the line voltage so please treat it with extreme care and never use it to power anything you can touch.
Brian.
Not only is your version wrong but your input cap is in pF instead of nF, and it is NEUTRAL not NULL.
I found the half wave schematic in the PDF too.
Thanks.
The ST design is untested as shown because Vbe negative AC swing would be excessive(>|-300Vp|) . THis can easily be corrected with a 500V series silicon diode but the 15k base resistor will dissipate less than 5 watts, so must be selected appropriately. All caps xxx nF caps are plastic hi V types. THe programmable Zener is set to 3.7V for float charging a LiPo battery or an LDO as shown and it pumps up to +3.7 in less than 1 second.
Otherwise it is a good design. I'm just surprised that ST released it, as it is.
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THe 15k resistor can be increased to 100k,1W and reduced power if a 1nF film cap is put in parallel., However the Vce must also be rated for 400V so the transistor must be changed .
Design is not looking so great now. with 3mA out at 3.7 from Zener with 30mA in at 230Vac 50Hz. Watt's that? 10mW out for about 5 VAR input?
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Unless you have a lot of experience, I would avoid of offline regulator DIY designs. There are many pitfalls with line transients and overvoltage.
For $2 it isn't worth the challenge unless you have some other motive.
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TO answer your original question;
THe Maxim design is not reversed but rather the output common ground is 3.3V below the Line voltage . THis might? be ok for low frequency Teridian meters but terrible for microwave radios built into meter as the local ground voltage modulates the stray capacitance at microwave frequencies and implies an antenna load current if there is a radio link with any proximity to the earth grounded meter structure.
Not only is your version wrong but your input cap is in pF instead of nF, and it is NEUTRAL not NULL.
I have 5 yrs experience with Power Meters , automated meter reading with ISM 1GHz radios.
The worst meters were only one ancient style of Westinghouse meters that used a plastic in the magnetic air bearing called Meltric? that was lossy and high K and whenever the disk rotated , energy at 1GHz was reflected and amplitude modulated by the resonant structure of the disk coupled by a tiny piece of plastic, about 50pF in the bottom of the magnetic air bearing spindle. It took me a year to figure that out in my spare time as Op Mgr, while the RF Engineers could not including my boss who had a PhD and much more experience than I. (actual R&D time 8 hrs)
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