A Novel Soft-Start Circuit for Buck DC-DC Switching Regulator

Aiming at the problem that DC-DC switching power supply chips are prone to large inrush currents at the power-on moment and thus damage the circuit, as well as the large area of the soft-start circuit, a new type of soft-start circuit has been designed. The core of the soft-start circuit is a soft-start circuit with a capacitance doubling structure, which is simple and easy to implement, and adopts the Miller capacitance doubling technology, which greatly reduces the size of the required capacitance, and then significantly reduces the circuit layout area. The soft-start circuit has been implemented and verified in a DC-DC switching power supply chip designed based on 0.18μm BCD process. The test results show that the soft-start circuit occupies only $0.004 \mathrm{~mm}^{2}$, the output voltage of the DC-DC switching power supply chip rises gradually, and the chip completes the start-up and starts normal operation in about 0.73ms.