• Supply: AC 100 kHz, 10V
• Output: DC 5V @ 30 mA, isolated, continuous
• Footprint: L 10mm x W 10mm x H 5mm
• Budget: $1 (preferably $0.50)
• Load:
  • ATTINY10, 200µA max, https://ww1.microchip.com/downloads/en/DeviceDoc/ATtiny4-5-9-10-Data-Sheet-DS40002060A.pdf
  • ACS711 Current sensor, 6mA, https://www.allegromicro.com/~/media/Files/Datasheets/ACS711-Datasheet.ashx

in a relatively small package, silent, low-cost, PCB-based.

What other details will help?

Could i use an SCR with a 555? This one is $0.13
https://www.digikey.com/short/nnzcdd3f


SCR Voltage Regulator Circuit
https://www.homemade-circuits.com/scr-voltage-regulator-circuit/

I'm also curious about a 3 amp version, which is discussed later in the thread.

----
Moderator's note:
You created this, a new thread, to continue your discussion about the power supply. The new thread is here:
https://forum.allaboutcircuits.com/threads/isolated-150mw-ac-to-dc-regulator.202896/

The earlier thread is: https://forum.allaboutcircuits.com/...-low-power-supply-without-transformer.202878/ and it has been locked -you have made this confusing enough. Only one thread per topic please.

 

What determines the output voltage? How tight is the regulation? Is that good enough for the processor?

 

The SCRs are slooooooow devices. They are designed to switch at twice the powerline frequencies, 100/120 Hz.
Many moons ago, there were inverter grade SCRs, good to a couple of KHz, but were discontinued when high power IGBTs were introduced.

 

What determines the output voltage? How tight is the regulation? Is that good enough for the processor?

ATTiny10 datasheet says "Operating Voltage: – 1.8 – 5.5V" (pg 2). But the sampler section says "Supply Voltage Range: 2.5V – 5.5V" (pg 91). I'm not sure how to interpret that. Maybe it means i need at least 2.5V to use the sampler? (i'm using the sampler)

I don't know how tight is needed for correct operation, but variation in ADC sample rate is fine for my purpose. Says "Internal reference voltage of VCC is provided on-chip" (pg 91), so i assume that will immunize the ADC from Vsupply variations.

But I'm a bit confused about current requirement. I'm not sure how to interpret this, but maybe to do with usage and Vsupply?

Low Power Consumption – Active Mode: • 200µA at 1MHz and 1.8V (pg 2)
DC Current VCC and GND Pins ............................... 200.0 mA (pg 123)
Icc Power Supply Current(6 "with external clock", but i'll use the internal clock), Active, 8MHz, VCC = 5V Max 4 mA (pg 125)

I won't be driving this chip hard. I can operate at low clock freq and relatively slow sample rate (hundreds or a few kSPS).

My supply will be mains, so no worry about draining a battery. I don't care about heat, as long as the components don't care.

The ACS711 wants a Vsupply of 3 to 5.5V, with 7V absolute max. We prolly do need pretty tight supply regulation for the current sensor, since the sensor output is proportional to Vsupply, i think. Says "maximum accuracy at 3.3 V VCC".

I think i should change the whole requirement to 3.3V instead of 5V, since the ATTiny10 also works at 3.3V.

 

For a load of only 6.2 mA, non-isolated, the cheapest and simplest solution would be a 78L05.

 

For a load of only 6.2 mA, non-isolated, the cheapest and simplest solution would be a 78L05.

Thx for that!
But isn't that DC/DC? My supply is AC.
Can i use a very simple, cheap, ripple-y, low-current rectifier on my AC, then feed to the 78L05?

The 78L05 is $0.07 @ 1,000 on Digikey. This one is half the price. Is this a clone?
https://www.digikey.com/short/1qwm9418

 

Use a small, 1W transformer, sourced from a Chinese vendor.
Or, if you don’t need insulation from the powerline, use a capacitive dropper.

 

Use a small, 1W transformer, sourced from a Chinese vendor.
Or, if you don’t need insulation from the powerline, use a capacitive dropper.

Don't need insulation. But why 1W? Isn't that oversized for a 6.2 mA supply?

Why capacitive dropper? As i understand, a capacitive dropper is used to limit inrush current from mains. I'm not working with mains. My AC is already current-limited.

I think we just need a rectifier and filter to convert the AC into DC for the regulator, right? Here's a full bridge rectifier for $0.05
https://www.digikey.com/short/z99wzfcd

Here's a 3.3V, 300mA regulator for $0.06
https://www.digikey.com/en/products/detail/skyworks-solutions-inc/AAT3258ITS-3-3-R/3789811

 

Have a read of the following, and please also google the term, there are many more examples on the web.

https://en.m.wikipedia.org/wiki/Capacitive_power_supply

 

Have a read of the following, and please also google the term, there are many more examples on the web.
https://en.m.wikipedia.org/wiki/Capacitive_power_supply

Thx, this is very interesting. Since my AC source is already at reduced current (say 200 mA) and reduced voltage (say 10V), I'll have to calculate different component values. But looks promising! Also have to compare stability vs a linear 3.3v regulator and ease-of-use.

Confused about something, they say to use a Zener Shunt Regulator for voltage regulation. Isn't a Shunt Regulator a current limiting device?



Here's a really good article.
https://www.st.com/resource/en/appl...ower-supply-from-mains-stmicroelectronics.pdf

Their capacitive supply doesn't seem to require a rectifier:



There's also Resistive power supply, but resistor eats a lot of power:

 

The UCC12050 has a transformer inside.


The silicon inside is probably a SN6501 and a verry small transformer. The SN6501 and SN6505 have a max input voltage of 5.5V.

If you have a higher input voltage, try the SN6507. Looks good to me.

 

The UCC12050 has a transformer inside.
The silicon inside is probably a SN6501 and a verry small transformer. The SN6501 and SN6505 have a max input voltage of 5.5V. If you have a higher input voltage, try the SN6507.

Thx for that! But those are expensive, and higher voltage or power than i need.
I think i found the solution


from @crutschow

 

I think i found the solution

Do you need isolation from the AC source? How much? (voltage)

 

Whether or not it works depends in why you need isolation. Why not tell us why? Many people come here thinking they need isolation when they don’t.

 

Many people come here thinking they need isolation when they don’t.

And people need certain kinds of isolation. Connecting two 1uF caps across the isolation gives DC isolation but at 100khz there is no isolation.

 

I misspoke earlier when I said I don't need isolation. I do need isolation. I revised my question.

people come here thinking they need isolation when they don’t

Take my word for it.

at 100khz there is no isolation.

Are you saying this circuit will not provide isolation at 100 kHz?

 

Are you saying this circuit will not provide isolation at 100 kHz?

If there were a 100kHz voltage between the two commons, it wouldn't be isolated by the capacitors.
Can you tell us approximately what the AC or/or DC electric voltage difference will be between the two isolated commons so we can better understand what you a trying to accomplish with this isolation?

 

If there were a 100kHz voltage between the two commons, it wouldn't be isolated by the capacitors.
Can you tell us approximately what the AC or/or DC electric voltage difference will be between the two isolated commons so we can better understand what you a trying to accomplish with this isolation?

If you're asking how much isolation I need, the answer is 200 volts.

Why is 100 kilohertz a problem? Can we fix that by changing the capacitance of the isolation caps? I'd like the freedom to keep my frequency anywhere from 100 kilohertz to 400 kHz.

 

I'd like the freedom to keep my frequency anywhere from 100 kilohertz to 400 kHz.

Still giving us bits and pieces of what you have.
What is "my frequency"?

 

Still giving us bits and pieces of what you have.
What is "my frequency"?

"My frequency" , meaning the frequency of this converter. At what frequencies does the circuit offer AC isolation? I thought it was isolated. Maybe it's only isolated from the DC supply of the 555 that you showed in the other circuit.
Isn't this one isolated from the AC?

.

You've said that the usage in unimportant to those replying, but that's incorrect. Without knowing exactly what you're trying to achieve we are in the dark.

An IC data sheet doesn't say "What are you making?" It simply provides the information about the IC, and sample applications schematics.

A textbook doesn't say "What are you making?" It explains concepts, and provides sample schematics.

The appropriate response isn't "what are you making?" the appropriate response is "What are the requirements? Current, voltage, isolation, etc."

The question "what are you making implies maybe you don't need this thing you think you need." As mentioned, I've already validated the need with professional EE's. If that's not good enough for you, I understand, and thank you for your time.