output inductor current i l is continuous the converter works in ccm and it is in any load fig1 b shows that under the condition of the minimum of i l being equal to i switch the output inductor current i l is boundary continuous the converter works in bcm and it is in any load fig1 c shows that under the condition of the minimum of i l being less than i switch the output inductor current i l is discontinuous the converter works in dcm and it is in light load or no load therefore selecting i switch lt 0 is better to avoid the diode rectification mode when i switch is close to zero there is little or no sink current thus realizing converters in parallel and pre bias start well when i l approaches i switch the secondary side mosfets have overstress issues at the moment of turning off the mosfets for the inductor current i l changing from negative value to zero suddenly otherwise due to the negative current the rms value of inductor current i l is not decreased obviously and the power loss is still high in light load and no load as shown above.