A DC-to-DC converting circuit includes a power switch unit, a second power switch, a phase node, a boosted circuit and a sensing circuit. The power switch unit includes a first power switch, a sensing element, a first end, a second end and a sensing end. The sensing element is connected to the sensing end and the first end. The first end is connected to an input voltage. The second power switch is connected to the first power switch. The phase node is located between the power switch unit and the second power switch and is connected to the second end. The boosted circuit boosts the input voltage to a first operation voltage and provides the first operation voltage to the sensing end. The first operation voltage is higher than the input voltage. The sensing circuit is connected to the boosted circuit and the sensing end to obtain a sensing voltage.
