Electrical – How is the transformer like component called on cellphone chargers?

power supply

Simple 5V power supplys use a transformer and a diode bridge followed by a linear regulator like in the picture. You get these for about/under 1$ from china. I wanted to integrate such a circuit into an PCB, but I am not able to find an transformer as cheap as these 5 supplys (I don't want to solder on one of these crap PCBs). All transformers I found cost over 1$. So I wanted to ask if this transformer like component is really called transformer since I'm not an native english speaker and don't find anything relevant.

EDIT: cause in the comments high currents are often mention I wanted to say that I only need some mA for low Power µController.
Also corrected the wrong circuit description (phone charger to simple power supply)

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Best Answer

The loathsome and dangerous pieces of c**p that you can buy for $1 from China are always going to be cheaper than what you can assemble from safe, reliable parts purchased through distribution chains in small quantities.

I've taken a couple samples apart- they were designed by people without any appreciation of value of life- clearances of a mm or so between the mains and output and conductive debris rattling around inside. No doubt the transformers are also made without proper pedigreed materials (for approvals, all the safety critical material specifications and sources have to be submitted to the safety agency, inspections take place, etc.)

If you want to make the circuit you show- 50/60Hz transformer and linear regulator, it will probably cost around $5-10 in smallish quantity and will be capable of maybe 300mA not 2A. If you need 2A, a switching supply is going to be the most practical- but it will cost a bit more, have many more components and will be a bit harder to design (see Power Integrations website for one-chip devices) and a lot harder to get safety and EMI approved.

If you want to avoid this, power your device from a proper approved external adapter from a major manufacturer, or suck it up and spend the money to get something safe internally. Few may care if your circuit doesn't work quite right, but a lot of attention will be drawn to you if it kills someone.