Monday, September 8, 2014

3A USB device charger (LM2576) (Updated)

My new project: USB devices charger.


  • LM2576T-ADJ (better LM2576T-5.0, but I have a bunch of ADJ version IC's, so i use them)
  • Heatsink for IC (Heatsink on photos taken from dead UPS).
  • Capacitor 470-220μFx35V for input (low ESR preferred)
  • 1N5822 freewheeling diode
  • 50μH inductor (from dead ATX PSU). 100-150μH is better, but 50μH works fine too.
  • Resistor 750Ω/2W as dummy load
  • Output capacitors. I've used 2200μF/10V from ATX PSU and 1500μF/6.3V from dead PC motherboard.
  • Output filter. ~16μH from ATX PSU
  • 2pcs 0805 resistors (1.5KΩ and 4.7KΩ) and 1KΩ 3303-W3 pot (not needed for LM2576T-5.0)
  • Dual USB-AF socket (taken from PC motherboard)

Assembled DC-DC converter

Charging cellphone and bluetooth headset

  • Device tested at 2Ω load. Output voltage - 4.91V at ~2.5Amp load.
  • Input voltage - 12-24V (tested). LM2576T allows up to 40V input (60V for HV version, see datasheet)
  • Converter may be used as USB car charger. Note: add P6KE27 at input.
  • Converter may be changed for any output voltage supported by IC.


Converter circuit schematics

Universal USB socket PCB
Notes: N/F - do not fit, 0 - jumper. All resistors SMD 1206, except R1-1 and R1-2 (0805)

Files (DipTrace v2.4):

Update 1

Charger now assembled in ATX PSU case.

USB socket PCB with fixtures

Case layout

Charging devices

1 comment:

  1. I was after something like this as part of a bigger design for a mobile device charging station.

    it involves a variable DC input of about 10v-40v which could be any of solar, battery, or AC->DC to a standard USB charging hub capable of detecting device according to current needs etc

    I like to contact you on itt if possible.