A switching power converter for converting an AC power into a DC power. The converter includes a transformer, a charge storage unit, a synchronization signal generator, and a switch element. The transformer includes a primary side coil and a secondary side coil, and the primary side coil generates an induced voltage at the secondary side coil according to AC power. The charge storage unit charges according to the induced voltage and outputs a DC power. The synchronization signal generator generates a synchronization signal according to the induced voltage. The synchronization signal is the first value when the induced voltage is positive and is the second value when the induced voltage is negative. The switch element, serially connected to the secondary side coil and controlled by the synchronization signal, is turned on when the synchronization signal is the first value and is turned off when otherwise.