A Piece Of Internal Power Supply Of Monolithic Ac/dc Switching Power Supply Chip Design

This subject is supported by National Key Projects-Automotive electronics and energy-saving chip. A monolithic AC/DC switching power supply with internal power source is designed on the CSMC700V BCD process. The control circuit, protection circuit and700V power MOSFET are integrated in the single silicon die to form a whole power system. Therefore, the chip has advantages of high integration, high efficiency, simple application circuits, lower EMI noise and so on. In this thesis, the internal power circuit, the control circuit and the protection circuit are analyzed and designed in detail.Firstly, the high voltage JFET is not only used to sample the current of the power switch but also to charge the internal power circuit. This kind of design makes the chip structure more ingenuity.Secondly, the novel double modulation mode is used in the control circuit design, which combines the current PWM modulation and the PSM modulation. This control strategy makes the switching power supply more efficient in any application.In the process of layout design, the problems of resistance network match, differential pair match, high voltage and low voltage isolation, ESD protection are considered carefully to make sure that the layout meets the design requirements.Finally, the chip is tested. According to the test report, this monolithic AC/DC switching power supply is fit for the design requirements.