I need the smallest power source possible to get 5V to power ATTINY402 and one 100K pullup and turn ON a MOSFET with a 2K resistor for 5 seconds once a day (to switch ON 1W LEDs run by a dedicated LED driver like AL5890)
So the continuous power consumption will be around 0.5mA with peak of 3mA for 5 seconds.
The power supply does not needs to be an isolated one as it will be enclosed in a sealed container and requires no user interactions.
The power supply needs to be inductor less and should not require an EMI filtering cap.
Since the current consumption is so low the Power Factor and Efficiency should not matter that much right? So its OK if the they are low.
The preferred size is less then or equal to SOP8 package. If there are no external components then that is preferable.
If this power supply requires a DC source like a bridge rectifier then it is already in our circuit so that should not be calculated in the size consideration.
What I have considered so far:
Capacitor dropper circuit:
The reason I did not choose this is because the capacitor needs to mains rated and they are pretty big so I have discarded that thought.
Resistor dropper Circuit:
Placed as the last resort if nothing else is available.
SR086 Based power Supply:
Requires a lot of external components and pretty big 470uF electrolytic capacitor at the output.
- Small Transformer: I could not find a very small mains rated 60Hz transformer that could fulfill my requirements.
This looks promising but it requires an X capacitor at the mains to keep the EMI under Class B (Which is the requirements).
- SMJR-N-1-24: I used this LED driver in my previous circuit and it provides 5V for my ATTINY as it has an internal 5V auxilary supply inside. So I was thinking maybe there is a chip that has only the 5V power supply circuitry inside.
Ideally I need a small chip that can give me 5V 2.5mA power from 120VAC. With minimal external components.