Abstract: 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.

Abstract: A universal series bus (USB) power supply has a DC power source, a USB power interface and a voltage modulation module. The USB power interface is for connecting to an electronic device that stores a default D+ voltage and a default D? voltage. The voltage modulation module connects to and outputs signals to the D+ and D? terminals of the USB power interface. If voltage levels of the output signals are not respectively identical to the default D+ and D? voltages, the voltage modulation module changes the voltage levels of the signals output to the D+ and D? terminals of the USB power interface until the voltage levels of the output signals are respectively identical to the default D+ and D? voltages. Therefore, the USB power supply may be applied to any kind of electronic device that is charged over a USB interface.

Abstract: A universal series bus (USB) power supply has a DC power source, a USB power interface and a voltage modulation module. The USB power interface is for connecting to an electronic device that stores a default D+ voltage and a default D? voltage. The voltage modulation module connects to and outputs signals to the D+ and D? terminals of the USB power interface. If voltage levels of the output signals are not respectively identical to the default D+ and D? voltages, the voltage modulation module changes the voltage levels of the signals output to the D+ and D? terminals of the USB power interface until the voltage levels of the output signals are respectively identical to the default D+ and D? voltages. Therefore, the USB power supply may be applied to any kind of electronic device that is charged over a USB interface.