Fan driving system with safe driving current switching

A fan driving system for driving a fan, the fan comprising a first terminal and a second terminal, the fan driving system comprising:

• a driving device configured for receiving Hall sensing signals N+ and N− outputted from the fan, the driving device comprising:
• a first driving signal output terminal, a second driving signal output terminal, a third driving signal output terminal, a fourth driving signal terminal;
• and
• a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) group, comprising a first N-type MOSFET, a second N-type MOSFET, a third P-type MOSFET, a fourth P-type MOSFET, a first diode, a second diode, a third diode, and a fourth diode,
• wherein a drain of the first N-type MOSFET and a drain of the third P-type MOSFET are connected to the first terminal of the fan, a drain of the second N-type MOSFET and a drain of the fourth P-type MOSFET are connected to the second terminal of the fan, gates of the first N-type MOSFET, the second N-type MOSFET, the third P-type MOSFET and the fourth P-type MOSFET are respectively connected to the first driving signal output terminal, the second driving signal output terminal, the third driving signal output terminal and the fourth driving signal terminal, on-off states of the first N-type MOSFET are respectively synchronous with on-off states of the fourth P-type MOSFET, on-off states of the second N-type MOSFET are respectively synchronous with on-off states of the third P-type MOSFET, the on-off states of the first N-type and fourth P-type MOSFETs are synchronous with but the reverse of the on-off states of the second N-type and third P-type MOSFETs, an anode of the first diode and a cathode of the third diode are configured to be connected to the first terminal of the fan, an anode of the second diode and a cathode of the fourth diode are configured to be connected to the second terminal of the fan, a cathode of the first diode and a cathode of the second diode are configured to connect to a power supply, and an anode of the third diode and an anode of the fourth diode are configured to be grounded.