This conversion is necessary because if the capacitor were connected directly to the voltage source, the current would be limited only by the parasitic resistance, resulting in high energy loss. At a short time scale, an inductor can be considered as a current source as it maintains a constant current. The two inductors L 1 and L 2 are used to convert respectively the input voltage source ( V s) and the output voltage source ( V o) into current sources. It is connected alternately to the input and to the output of the converter via the commutation of the transistor and the diode (see figures 2 and 3).

The capacitor C 1 is used to transfer energy. The main disadvantage is the high current stress on the switch. The main advantage of this converter is the continuous currents at the input and output of the converter. It is an inverting converter, so the output voltage is negative with respect to the input voltage. The Д†uk converter allows energy to flow bidirectionally by using a diode and a switch.ДЄ non-isolated Д†uk converter comprises two inductors, two capacitors, a switch (usually a transistor), and a diode. Because the power transfer flows continuously via the capacitor, this type of switcher has minimized EMI radiation.

For example, the coils may share single magnetic core, which drops the output ripple, and adds efficiency. There are variations on the basic Д†uk converter.

3.3 Single-ended primary-inductance converter (SEPIC).

Cuk converter waveforms