The imitation charger has about half the components of the genuine charger and a lot of blank space on the circuit board. While the genuine Apple charger is crammed full of components, the imitation leaves out a lot of filtering and regulation as well as the entire PFC circuit. The transformer in the imitation charger (big yellow rectangle) is much bulkier than in Apple’s charger; the higher frequency of Apple’s more advanced resonant converter allows a smaller transformer to be used.
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