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230VAC -> 2mA@11VDC 1MHz@3.3Vcc 1mA MPU to drive 50Wmax AC mosfet switch

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szan:
Hello,
I need to drive 50W 230VAC IR light bulb by using AC mosfet switch controlled by small 8bit MPU 1MHz@3.3Vcc*1mA.
I've designed such simply 230VAC -> 2mA@11VDC PSU where one of 3.9Vz diodes will be used also as source of true randomness coming from Zener diode avalanche noise ~2V input to ADC MPU pin.
MPU will have another one 100nF capacitor and fixed 3.3Vcc with BOD enabled.
It looks good in this simple http://www.falstad.com simulation.

What do you think ?  ::)
PS: Of course do NOT try this at home unless you know what you are doing.

moffy:
A simple low current PSU from mains that avoids the dissipation of the 100k dropper resistors and uses an X type (Mains self healing) cap instead. It avoids the dissipation and is compact, simple and widely used. Please note components were chosen for convenience of sim not necessarily final design values.

szan:

--- Quote from: moffy on December 03, 2022, 11:18:32 pm ---It avoids the dissipation and is compact, simple and widely used.

--- End quote ---
Yep, I know, but when this high voltage capacitor fails in your design, it will be disaster  :-BROKE
Small power dissipation shouldn't be a problem, since it is expected to be less than 1W in my design.

moffy:

--- Quote from: szan on December 04, 2022, 12:34:56 am ---
--- Quote from: moffy on December 03, 2022, 11:18:32 pm ---It avoids the dissipation and is compact, simple and widely used.

--- End quote ---
Yep, I know, but when this high voltage capacitor fails in your design, it will be disaster  :-BROKE
Small power dissipation shouldn't be a problem, since it is expected to be less than 1W in my design.

--- End quote ---

The 100 ohm resistor acts as a fuse, so if the cap fails the resistor goes open circuit, no problems.

szan:

--- Quote from: moffy on December 04, 2022, 12:45:03 am ---The 100 ohm resistor acts as a fuse, so if the cap fails the resistor goes open circuit, no problems.

--- End quote ---
It will depend on the size of this 100R resistor - if it will be too small/short than you can have current flow with corona discharge in the air, so my idea is to immerse this circuit in black hot glue or paraffin inside concrete bottom base to avoid any air under/above  PCB and it will help additionally to dissipate heat from those current limiting resistors.
It could be better to add glass fuse instead of resistor as a circuit breaker  :o

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