I just got my hand on some chargers (0.6$ pcs), witch are actually small switchers.
I couldn't buy the comps ot the little housing for that money. And the opamp seems nice , if i can unsolder it wo. damaging it.
There is a small DC-Jack , and it says 9v AC
There is also a USB Jack (The square one like on the back of printrs), and i think it might be used as an "Input" , instead of 9v AC.
There is a schematic , but a lot of component values are missing , so i have listed my findings/measurements below (values have been measured on components mounted on the pcb).
I have been told it's a charger , and that it could be used for LI-PO cells.
My guess (remember im an analog noob) , is that the Opamp is somehow measuring the current or voltage of the 4 1R's in parallel , and is "twiddeling" with the LM2575 FB (Feedback) , and maybe even adjusting the voltage or ??
Question 1: If i Lift the LM2575 FB (or unsolder the BAV70) , and connect FB directly to C104. Wouldnt that make a "normal 5v 1A" switcher out of it ?
Question 2: If someone could explain the "magic" in this circuit , i might even modify the resistors to so other usefull things. I promise ... I'll start reading about opamps :oops:
Comp Mark Value Measured R103 182 1800 R104 182 1800 R102 01D 100K 101K Think i can read (Links bwlow) that 01 = 100 and D = 1000 in Mult Factor R105 01D 100K 23K R106 01Y 1 0,4 Ohm 01 = 100 & Y = 0.01 in mult factor, R107 01Y 1 R108 01Y 1 R109 01Y 1 0,3 Ohm L101 331 330 uH NA I think 330uH , its a "Square SMD inductor in a Ferrite core, quite big" L102 NA ?? NA Grey , about twice the length & height of a 1206 Cap L100 NA ?? NA Grey , about twice the length & height of a 1206 Cap D105 EC61 Quad-Transil ESDA6V1SC5 (SOT23-5L) http://www.st.com/stonline/products/literature/ds/7056.pdf U100 LM2575 http://www.national.com/ds/LM/LM1575.pdf U101 LM8261M5 http://www.national.com/ds/LM/LM8261.pdf http://www.talkingelectronics.com/ChipDataEbook-1d/html/SM-Resistors.html http://talkingelectronics.com/projects/ResistorsMadeEasy/SMD-Resistors-EIA-Markings.html
Edit: Added D105 a "Quad-Transil"
Measured Vout across C10 5.67v , Vfb is 5.06v