Most of our discussions in forum are about best performance. But engineering is also a lot about reliability and safety to user. There was news this week that someone had died in China from an "Apple" charger on iPhone 4. Latest news seems to indicate the charger in use was a counterfeit charger. It is remarkable how far they go in making the units look the same. But the guts inside are a different story.
This video is from Dave Jones whose video blogs are a jewel for electronic engineers/hobbyist where he takes apart these chargers. So it may be a bit too technical as far as the points he makes but it is still a very good watch given the latest news on this front:
Safety is a big issue here since to make these chargers small, they use a switching power supply. A switching power supply converts the input AC to DC, converts it to high-frequency AC as to make stepping it down in voltage much smaller. Otherwise, you would need the large, heavy traditional transformers. The transformers are great because they provide high isolation so even cheap ones aren't so bad. Cheap switching power supply is another matter since DC high voltage is so close to the USB output. Watch the video above which should scare the pants off of anyone using knock off chargers.
This video is from Dave Jones whose video blogs are a jewel for electronic engineers/hobbyist where he takes apart these chargers. So it may be a bit too technical as far as the points he makes but it is still a very good watch given the latest news on this front:
Safety is a big issue here since to make these chargers small, they use a switching power supply. A switching power supply converts the input AC to DC, converts it to high-frequency AC as to make stepping it down in voltage much smaller. Otherwise, you would need the large, heavy traditional transformers. The transformers are great because they provide high isolation so even cheap ones aren't so bad. Cheap switching power supply is another matter since DC high voltage is so close to the USB output. Watch the video above which should scare the pants off of anyone using knock off chargers.