When I use it charging it turns off using a DIY usb charger. why?

I am assuming from your post you have a 1001 or 1000 series PSP.

the 1000 series (Fat), 2000 series (old slim), 3000 series (new Slim) or the PSP Go varies in design.

I also assume your charging from the charge port on the bottom right of the PSP.

I would double check the wiring in the charge cable, check your PSP battery's level and try other USB ports on what ever computer or device your trying to charge from. Trying a different PSP battery to see that its not your PSP battery, also clean any contacts with rubbing alcohol.

In USB cords, Red is usually the 5 volt line, black is ground, and the white and green are data lines, you will not need the data lines. You only want the Red and Black Wires.

The other end of the charger should also have a 5v and ground wires, usually also Red for 5 v black for ground.

You would also want to check the polarity of your Charger Cable, to make sure you connect the correct wire to the correct part of the plug.

For future reference, I would put a diode on the 5v line, as a extra safety measure for both the PSP and the USB enabled device, like a computer.