Power supply system and protection method

A protection method for a power supply system capable of selectively providing either a first power source or a second rechargeable power source connected to the power supply system, the power supply system comprising a switch and a controller, the switch comprising a bipolar junction transistor with the base connected to the controller through a resistor, the collector being connected to the first power source through a resistor, and the emitter connecting to ground;

• and an insulated gate bipolar transistor with the source connecting to the first power source, the drain connecting to the second power source, and the gate connecting to the collector of the bipolar junction transistor, the protection method comprising:
• the controller detecting a presence of the first power source;
• the controller detecting a presence of the second power source at the presence of the first power source;
• and
• the controller controlling the bipolar junction transistor and the insulated gate bipolar transistor of the switch periodically establishing a connection between the first power source and the second power source at an absence of the second power source.

An electronic device, comprising:

• a first power source;
• a second power source;
• a switch for establishing a connection between the first power source and the second power source so as to allow the first power source to charge the second power source, wherein the switch comprising a bipolar junction transistor with the base connected to the controller through a resistor, the collector being connected to the first power source through a resistor, and the emitter connecting to ground;
• and an insulated gate bipolar transistor with the source connecting to the first power source, the drain connecting to the second power source, and the gate connecting to the collector of the bipolar junction transistor;
• and
• a controller for detecting a presence of the first power source and the second power source, and controlling the bipolar junction transistor and the insulated gate bipolar transistor of the switch to periodically establish the connection at the absence of the second power source, and to continuously establish the connection at the presence of the second power source.