Single-ended primary-inductor converter
The single-ended primary-inductor converter (SEPIC) is a type of DC-to-DC converter that allows the voltage at its output to be greater than, less than, or equal to the input voltage. The output of a SEPIC is controlled by the duty cycle of the electronic switch (S1).
Source: Wikipedia — Single-ended primary-inductor converter (CC BY-SA 4.0)