A Flyback Type Single-chip Switching Power Supply Chip Computer Simulation

Monolithic switching power supply is characterized by its high efficiency, high performance, high density integration, small size, light weight, etc. As the first choice for design scheme concerning switching power supply, monolithic switching power supply enjoys weighty research significance as well as broad market prospect.Careful analysis on circuit principles is conducted before circuit simulation is performed through applying simulation tools HSPICE. Related simulation results are presented to testify the validity and feasibility of this circuit. It turns out that all the simulation results of circuit submodule meet predetermined requirements.This master’s thesis starts with the introduction of the overview and development trend of monolithic switching power supply, and then proceed with fundamental principles regarding switching power supply, followed by detailed illustration of simulated fly-back topology switching power supply circuit designed in this thesis. This circuit adopts combined modulation mode integrating Pulse Wide Modulation (PWM) with Pulse Skip Modulation (PSM) and current-mode topology is employed in the whole control circuit. Internal integrated circuit applies high voltage LDMOS whose breakdown voltage is around700V, with operating frequency of132KHz and maximum operating current of250mA. The chip features a wide range of working temperature, since over-current and over-heat protecting circuits are installed inside; the inner dynamic self power supply system provides working power supply to inner low-voltage circuit via external capacitor; moreover, PSM doesn’t require compensation circuit, which enhances work efficiency to a great extent. Grounded on mono-crystalline silicon, this circuit adopts simulation design featuring high-low voltage compatible technology and high-voltage power devices are integrated with low-voltage control circuits on the same chip.Key emphasis is laid on reference circuit, current-limited comparator circuit, current-limited statemachine circuit and current-sensing circuit in monolithic switching power supply chip. The reference circuit adopts bandgap structure; the combined work of current-limited comparator and current-limited statemachine effectively improves load regulation and lowers the noises made by transformer; the adoption of SenseFET current sampling guarantees high accuracy and low power consumption.BCD technology is involved in this chip. A brief introduction of basic IC process and the layout design rules is made before the author of this thesis presents the structural drawing of electronic devices within the simulation circuit as well as related simulation results.