Switch power supply and electronic device having same

An electronic device comprising:

• a motherboard;
• a battery;
• and
• a switch power supply electrically connected to a utility power source, the motherboard and the battery, and comprising:
• an AC/DC converter for receiving an input AC voltage issued by the utility power source and converting the input AC voltage into a DC voltage;
• a DC/DC converter electrically connected to the AC/DC converter for converting the DC voltage into several working voltages required for operating the electronic device;
• a battery charge-discharge switching circuit having a first terminal selectively connected to the AC/DC converter or the DC/DC converter and a second terminal connected to the battery;
• and
• a detecting and controlling circuit for detecting the input AC voltage, wherein if the input AC voltage is abnormal, the detecting and controlling circuit issues a control signal to the battery charge-discharge switching circuit, and in response to the control signal, the battery charge-discharge switching circuit is switched to a discharge state such that the battery issues a discharge voltage to the DC/DC converter and the discharge voltage is converted into the working voltages by the DC/DC converter.