|
I agree, from the computer side of things a USB port is exactly as described. But you are missing the point. A USB charger, and I have many of them, can supply only 500mA but many of them are rated at 800 mA or more. I have some that can supply 1 Amp, all at 5 Volts or there about. I worked, before my retirement, for a PDA company that used such a charger. Now why would you design a charger that uses a USB connector that can supply 1 AMP of current? Why make it more expensive when you only need to output 500 mA.
The reason is simple. A eBook reader is a smart device as is a PDA. They can decide if they are plugged into a computer or plugged into a charger. Haven't you ever noticed when you plugged in your device to a computer a message appeared saying do you want to charge, or attach to the computer for data transfer.
My Hanlin says: To connect press OK. To charge press any other key. How does it know? Well, technically I could get into handshaking but that is un-important. The important thing is that is does know. A it takes 6 hours to charge my eBook Reader. However, if I plug into my charger it will charge in 3 hours. How come? Because it uses more current. The eBook reader knows it can yank 1 AMP out of my charger and does so. But it I were to use my poor little cell phone charger I would probably blow it up.
Dale
|