This circuit board was inside a cell phone USB charger, Im curious as too why an old cell phone charger would have an R.F circuit board? can anybody tell me more about this...

The letter G and U on the top part of board is what exactly??? I assumed the brand/company logo but i cant find any info...

the smaller writing on bottom part of board says

R.F.TECH
12/01/06
ETAOU61
REV:1.0

 

The charger is a Switch Mode type power supply.
They operate at high (radio) frequency and their design is not much unlike other RF designing.
No surprise a company specializing in radio frequency would do the board design.

 

This circuit board was inside a cell phone USB charger, Im curious as too why an old cell phone charger would have an R.F circuit board? can anybody tell me more about this...

The letter G and U on the top part of board is what exactly??? I assumed the brand/company logo but i cant find any info...

the smaller writing on bottom part of board says

R.F.TECH
12/01/06
ETAOU61
REV:1.0

The; "RF Tech" is probably the name of the manufacturer.

A few specialist SMPSU manufacturers go to a couple of MHz because they can use smaller cheaper inductors and capacitors, but it can be a case of diminishing returns as eddy current losses rise in the ferrites. rectifier recovery time imposes limits and fast power transistors/MOSFETs cost more.

About 50 - 100kHz isn't "pushing the envelope", so a cheap PSU is more likely to be in that range.