This is the basic illustration of the PFC circuit set up in Transition Mode operation. The waveform on the right shows the current in the inductor. Note how the ripple current excursions go down to the 0 Amp axis, and goes back up where the peaks form a 60 Hz envelope. The terms “Transition” or “Critical” comes from the fact that when the current goes down close to 0 A, the inductor is at the transition or critical point where all of its energy is near zero but then comes another PWM cycle to re-energize the inductor. Transition mode operation is capable of achieving power factors of 0.9, a fairly good power factor and can meet agency mandates, however, it is limited by the power range, usually below 600 W. It is also a lower cost implementation as component cost and complexity are significantly reduced. Applications for transition mode include, lighting ballasts, LED lighting, and consumer electronics.