Sepic Converter Design and Operation. Fig 4.1 Graph of Triangle wave and Sinusoidal control wave 12 Fig 4.2 Graph of controlled square wave 12. The SEPIC converter is able to either increase or decrease an input voltage by controlling the Duty Cycle of a pulse to the MOSFET. One way to do that is to directly control the Duty. The ripple current in the load is greater for Cuk and ZETA converters than SEPIC, because the SEPIC converter has an inductor L2 that smooth the current spikes. The switch of SEPIC and Cuk converters is a N channel MOS transistor that needs a Low Side driver when the ZETA converter has a P channel MOS transistor that needs a High Side driver.
DescriptionThe non-isolated Cuk converter is a DC/DC power converter that, like a buck-boost converter, can produce an output voltage (Vout) magnitude that is either greater or less than the input voltage (Vin) magnitude. However, it is an inverter converter, so the output voltage is of opposite polarity with respect to the input voltage. In the Cuk converter topology, the capacitor C1 acts as the primary means of storing and transferring energy from the input to the output.
The advantage of this converter is that both the input current (IL1) and the current feeding the output stage (IL2) are reasonably ripple-free (unlike the buck-boost converter where both these currents are highly discontinuous). Assuming a constant voltage across C1, the theoretical transfer function of the Cuk converter is.