KP

For a waveform with ripple current IR and a peak current IP, a parameter KRP can be defined as follows:

(Refer to figure below). For a power supply operating in the Continuous conduction mode, KRP can be used to exactly define the degree of continuous operation. KRP can range from zero to one, with a lower KRP value indicating a smaller ripple current IR and hence a more continuous operation. KRP is 1.0 for the borderline between continuous and discontinuous mode operation.

Minimum recommended KRP is 0.4 for TOPSwitch designs with 110/115 VAC input voltage or universal input voltage range. Minimum recommended KRP for TOPSwitch designs with 110/115 VAC doubled mains input or 230 VAC input voltage is 0.6.

Figure above shows waveforms for KRP of 1.0 (borderline between CCM and DCM) and a KRP of 0.4 (deeply Continuous design).

For power supply running in Discontinuous mode, a parameter KDP is defined as follows:

, is essentially (refer to figure below) the ratio of the off time of the primary switch TOFF to the time required to completely discharge the energy stored in the transformer TDIS into the secondary load. A useful range of KDP is . The upper range of KDP is generally encountered in power supplies with very low output power.

Figure above shows waveforms to explain definition of KDP (for Discontinuous conduction mode).