SIDO BUCK Converter With Self-Adapted PCCM Method

In recent years, DC-DC converters are more widely applied to electronic products. As the complexity of these products increases, more modules are necessary for them. As an effective solution, switching power supply with multiple outputs reduces the PCB size as well as the volume of products effectively. Therefore, the research on it is meaningful.This thesis proposed a single inductor duel outputs (SIDO) BUCK converter. To avoid the cross regulation, conventional SIDO converters usually adopt time-multiplexing control scheme in discontinuous current mode (DCM). Different from them, the proposed converter introduced a pseudo continual current mode (PCCM), the advantage of which is that besides the immunity of cross regulation, it enhances its driver capability with the same inductor peak current.The DC levels supplied by the converter could be set separately as required. In addition, they will be dynamically adjusted by their loads, which extend the range of load and makes the chip application more flexible. The function of cover-current limitation is used for circuit protection as well as for cross regulation suppression with a rational pre-set upper limit. The DC level isolation and peak current limitation guarantee a good isolation between two loads, which simplifies the design greatly due to that the load loops can be treated independently in feedback loop analysis.The inner oscillator outputs 500kHz clock signal. And the voltage feedback loop is adopted. The system and blocks were simulated and verified by Cadence Spectre and results showed that all expectations were well achieved.The chip was fabricated in 1.5um BCD process and tested in self-designed PCB. The test results showed that the converter converted an input voltage into two stable outputs with one inductor. While loads change, the system kept stable and no cross regulation was detected. The test results are consistent with the design specifications.