Taking the Cuk power factor correction (PFC) converter working in the discontinuous capacitor voltage mode as an example, the phenomenon of slow scale bifurcation when the system load increases is described. In this paper, the characteristics and causes of slow scale bifurcations are analyzed, the harmonic balance solution of the system is derived based on the principle of power balance, and the theory is verified by simulation. The simulation results show that with the increase of the load resistance, the system will enter the period doubling bifurcation and then enter the chaos state, and the circuit is prone to bifurcate under light load. This kind of slow scale bifurcation phenomenon and related analysis have been verified experimentally.
