| 摘要 |
A universal USB charger connected to an electronic device stored with a set of preset voltage values has a power supply circuit, a USB interface having a VBUS terminal and a ground terminal respectively connected to a positive DC power terminal and a ground terminal of the power supply circuit, and an output voltage switching module having multiple preset voltage units corresponding to electronic devices of multiple brands and a switching interface connected between the preset voltage units and a D+ terminal and a D- terminal of the USB interface. Each preset voltage unit outputs a D+ voltage and a D- voltage. The switching interface is operated to output the D+ and D- voltages associated with the electronic device through the D+ and D- terminals. After determining that the D+ and D- voltages match the set of preset voltage values, the electronic device allows itself to be charged by the charger.
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