A Cross-cycle Modulation Mode Chip Switching Power Supply Design

Monolithic switching power supply has many advantages, such as high efficiency, high quality with low price, small size and simple peripheral circuit etc. It has already been the preferred choice for power supply equipments.At first, the development and fundamental of monolithic switching power supply are presented in this thesis. Then a novel monolithic switching power supply circuit only with four terminals is analyzed at detail. It uses Pulse Skip Modulation and current-mode topology. Low voltage control circuits and high voltage LDMOS whose breakdown voltage is around 600V are integrated on this monolithic switching power supply chip. The limited current of high voltage LDMOS is 250mA. Output power of the whole circuit is less than 9W. Flyback topology can be applied in the switching power supply design. It is going to be fabricated in The 24th Institution of China Electronic technology company with developing BCD technology.The following sub-blocks are analyzed in this thesis: reference circuit, current-limited comparator, current-limited statemachine, leading edge circuit and trimming circuit. The reference circuit adopts bandgap structure. The temperature coefficients of voltage reference and current reference circuits are 18ppm/℃and 36.2ppm/℃respectively. The combination of current-limited comparator and current-limited statemachine reduces the noises generated by transformer. The leading edge circuit could avoid LDMOS premature shutdown. Trimming circuit could adjust the key parameters of this switching power supply chip after packaging and the product rate can be increased. The fundamentals of blocks above are analyzed in this thesis. Simulation waves and key parameters that are got with EDA tool HSPICE are presented. Finally the simulation results are fulfilled the requirement.The linear compensation bandgap reference adopted in this thesis has limited temperature stability for ignoring the influence of VBE high order items. For improving the temperature stability, a voltage reference circuit that adopts high-order compensations technology with the exponential relationship between diode reverse current and temperature is presented in this thesis. The simulation result shows that the...