Wireless input device and power management method of the same

A wireless input device, comprising:

• a primary battery set, providing electricity to the wireless input device;
• a backup battery, providing electricity to the wireless input device when the primary battery set does not have sufficient electricity to supply the wireless input device;
• an electricity generating device, generating electricity in response to clicking/pressing operations to the wireless input device;
• an energy-storage/charging device, coupled to the backup battery and the electricity generating device, storing the electricity generated by the electricity generating device, and charging the backup battery when the stored electricity reaches a predetermined value, wherein the energy-storage/charging device comprises an integrator and a control logic, a capacitor of the integrator stores the electricity generated by the electricity generating device, and the control logic determines whether the capacitor has finished discharging;
• and
• a switching device, coupled to the primary battery set and the backup battery, selecting the primary battery set or the backup battery to provide electricity to the wireless input device.