The present invention relates to a switch mode power supply and a driving method for reducing switching loss and audible
noise in the burst mode. The switch mode power supply includes a main switch, a power supply, an output unit, and a switch controller. The power supply includes a
transformer having a primary coil connected to the main switch, and supplies power to a secondary coil of the
transformer according to the operation of the main switch. The output unit is connected to the secondary coil of the
transformer and outputs power supplied to the secondary coil of the transformer. The switch controller receives a feedback
signal corresponding to the output
voltage of the output unit, a sense
signal corresponding to the current flowing to the main switch, and a
sync signal corresponding to the
voltage difference at the main switch, controls the on / off of the main switch, and determines whether to start the burst mode by using the feedback signal, and maintains the switching operation forcibly off period in the burst mode so that the reference frequency of
burst switching may be less than a predetermined value.