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I designed an AC-DC converter circuit(220VAC to 5VDC@700mA) to create a smart phone USB charger.

The Transformer that I used in my design can supply only 700mA current.

I searched the Web and noticed that the specification for the USB 1.0 and USB 2.0 says that they can provide 500mA which in my case is just fine, but on the other hand the USB charger of the most of the SmartPhones support 1A current.

I'm wondering if there is any way to inform the USB Device (in my case smart-phones)to drain up to 500mA current?

Perhaps some specific configuration on the D+ and D- pins.

I'm afraid that if the USB Device drains current up to 1A, in some cases it will damage the circuit and USB device.

The attachment contains the schematic

AC-DC Converter (220VAC to 5VDC)

Mehdi Hafezi
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    There are several standards for doing this. The simplest is just to connect D+ to D-. Take a good google around the net, you'll find several suggested methods that work for some devices and others that work for other devices. – JRE Dec 23 '16 at 17:28
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    See this answer: http://electronics.stackexchange.com/questions/123172/what-is-the-ideal-way-to-handle-data-pins-d-and-d-on-a-usb-power-adapter-to-be. – Ken Shirriff Dec 23 '16 at 17:45

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