Continuous Conduction

The analysis thus far is based on the assumption that the current through the inductor is continuous. The inductor current varies over a cycle, varying between a minimum value and a maximum value. The minimum and maximum values can be expressed in terms of its mean value and its change as expressed in equation (3). That is,

and

It is shown in Fig. 6 how the maximum and the minimum inductor current can be obtained. It is also shown that as the load resistor becomes greater, the average inductor current reduces, but the peak-to-peak ripple in inductor current does not change. It has to be so and expression for DI_L in equation (3) does not indicate any term reflecting the load resistor.

For continuous conduction,

At the boundary of continuous and discontinuous conduction,

Another expression for I_L is now obtained. Substituting for V_o in equation (15) the expression in equation (8), we obtain that

Substituting for I_L from the equation above and for )i_L from equation (3), equation (18) becomes:

and

From equations (23) and (24), the condition for continuous conduction is:

Equation (25) can be interpreted as follows, assuming that only one of the four parameters is varied at a given time with the other three parameters remaining unchanged.

The circuit tends to become discontinuous,

1. if the switching frequency f is decreased, or
2. if the duty cycle D is reduced, or
3. if the load resistance increases, or
4. if the inductance used has lower value.