Transformerless 85-260V-AC to 12V-DC Power Supply

[hesam.moshiri]

Whenever you hear the transformerless (ac to dc converter without transformer) supply term, you initially imagine the capacitor-based solution: a high-voltage non-polarized capacitor in series with the mains line, a bridge rectifier, a Zener diode, and a filtering electrolytic capacitor. Such a circuit is not only unable to deliver sufficient current for many applications, it is also not a reliable solution for the industry. However, you might see such circuits in some cheap products. This design uses a different method.

CAD: Altium Designer, Altium-365
PCB Fabrication: PCBX.com
Tools: Siglent SDL1020 DC Load, Siglent SDS1104X-E Oscilloscope, VEVOR SC240M Thermal Camera

[hesam.moshiri]

[PCB Update] AC to DC Transformerless Power Supply

[temperance]

That's nothing new.

Regarding a cap dropper you state:

it is also not a reliable solution for the industry

How did you conclude they are not reliable?

[hesam.moshiri]

How did you conclude they are not reliable?

The clearance between the bottom polygon and capacitor pins was low. I increased it to 1.8mm

[temperance]

a high-voltage non-polarized capacitor in series with the mains line, a bridge rectifier, a Zener diode, and a filtering electrolytic capacitor. Such a circuit is not only unable to deliver sufficient current for many applications, it is also not a reliable solution for the industry

I'm referring to the bolt part of your statement.

[Psi]

Nothing wrong with a capacitive dropper psu for consumer products.
It just has to be designed and used safely.
But it is true that they are low current, under 50mA. However since the voltage is only set by a zener if you want you can have your 50mA at 48V and then have a little DCDC to get 500mA at 3.3V

[DavidAlfa]

it is also not a reliable solution for the industry

Hah! Capacitor droppers are EVERYWHERE in commercial products.

[temperance]

Hah! Capacitor droppers are EVERYWHERE in commercial products.

And also industrial products. They are reliable when properly designed. That is: correct type of capacitor with proper surge and transient protection.

But what I wonder is why the OP must list the CAD and PCB supplier used for this project... As if mentioning those made any improvement to the power supply. Oh, I see, it is all about promoting your video blog and your sponsors who seem to be happy with the things you present.

I watched a few of your videos and they contain a lot of mistakes.

[boB]

When I think about a transformer-less (non-isolated) converter, I normally think of a buck converter for an application like this.

Quite a range but can be done.  Probably better to use a transformer.  You could use a flyback which is not technically a transformer.

boB

[Xena E]

Nothing wrong with a capacitive dropper psu for consumer products.
It just has to be designed and used safely.
But it is true that they are low current, under 50mA. However since the voltage is only set by a zener if you want you can have your 50mA at 48V and then have a little DCDC to get 500mA at 3.3V

Why limited to 50mA ?

 

[temperance]

The OP is only abusing this forum for promoting his crappy video blog.

[Psi]

Nothing wrong with a capacitive dropper psu for consumer products.
It just has to be designed and used safely.
But it is true that they are low current, under 50mA. However since the voltage is only set by a zener if you want you can have your 50mA at 48V and then have a little DCDC to get 500mA at 3.3V

Why limited to 50mA ?

 

There's no hard limit, it's more a practicality limit in most application.
Normally devices that use capacitive dropper power supplies do so because they are physical size constrained.
The higher max current you need the bigger the capacitor becomes. Once you get to around 50mA the X2 mains film capacitor is so big that you have enough room to use a different/better power supply type.

Also capacitive droppers are shit in terms of efficiency. If your circuit needs up to 50mA periodically (like for a relay) but normally only needs 1mA to run a MCU you must design your capacitive dropper so it can produce 50mA. However that means it's always drawing 50mA 24/7 whether you need it or not. Either the 50mA goes into your circuit or, if not, the remainder is all burnt off as heat in the zeners and you have to deal with the heat dissipation, which gets worse at higher currents.

[Xena E]

Nothing wrong with a capacitive dropper psu for consumer products.
It just has to be designed and used safely.
But it is true that they are low current, under 50mA. However since the voltage is only set by a zener if you want you can have your 50mA at 48V and then have a little DCDC to get 500mA at 3.3V

Why limited to 50mA ?

 

There's no hard limit, it's more a practicality limit in most application.
Normally devices that use capacitive dropper power supplies do so because they are physical size constrained.
The higher max current you need the bigger the capacitor becomes. Once you get to around 50mA the X2 mains film capacitor is so big that you have enough room to use a different/better power supply type.

Also capacitive droppers are shit in terms of efficiency. If your circuit needs up to 50mA periodically (like for a relay) but normally only needs 1mA to run a MCU you must design your capacitive dropper so it can produce 50mA. However that means it's always drawing 50mA 24/7 whether you need it or not. Either the 50mA goes into your circuit or, if not, the remainder is all burnt off as heat in the zeners and you have to deal with the heat dissipation, which gets worse at higher currents.

Thanks.

I just commented as I've just done one for 1 amp on a 50Hz supply! It's for an approximate constant current in a device that has to have no magnetic radiated fields: it's dopper capacitor is 15μF.

The design is customer led so inevitable it would be quirky but works it does!

Regards,
X

[ArdWar]

When I think about a transformer-less (non-isolated) converter, I normally think of a buck converter for an application like this.

Quite a range but can be done.  Probably better to use a transformer.  You could use a flyback which is not technically a transformer.

boB

Transformers are neat way to keep duty cycle within sane value.

You can also use tapped inductor (a.k.a. autotransformer) to do that, which I guess even closer to "not a transformer" than a flyback. Depending on if you're function purist or construction purist.