A flyback power converter includes a transformer, a power switch, a power switch control circuit, a synchronous rectification (SR) switch, an SR switch control circuit, and a signal coupler circuit. The signal coupler circuit includes a primary port and a secondary port, wherein the primary port is electrically connected to the power switch control circuit, and the secondary port is electrically connected to the SR switch control circuit. The primary port and the secondary port receive different signals generated by the power switch control circuit and the SR switch control circuit respectively, and the signal coupler circuit senses and converts the different signals to generate corresponding converted signals at the secondary port and the primary port respectively in different and non-overlapping time periods, without direct contact or direct connection between the primary side and the secondary side of the transformer.