Linear charging method and device combined with PD protocol and charging circuit

The invention relates to the technical field of charging devices, in particular to a linear charging method and device combined with a PD protocol and a charging circuit. The device comprises a USB PD decoy module, a constant-current and constant-voltage charging module, a charging current sensing module and a power supply voltage adjusting module. A PPS protocol of a USB PD standard is utilized, a PD decoy module is integrated in a charging chip to judge whether a USB PD charger exists or not and adjust the output voltage of the USB PD charger, a 1/N ICHRG current source of a linear charging constant-voltage constant-current current mirror charging module is utilized to sense the actual charging current, the current flows through a resistor, and the current flows through the resistor. The voltages at the two ends of the resistor are compared with a preset charging current small level and a preset charging current standard level, and signals that the charging current is small and the charging current reaches