Chip Switching Power Supply Current Sampling And Self-powered Technology

A novel monolithic Switching Regulator with peak current control mode is analyzed in this thesis. The chip can be assembled to an only four pins package by integrated the supply, sensor, control and driver. It is suit for the Flyback converter topology application which has lower system cost than other integrated/hybrid solutions, and is ideal for cell-phone charger and PC, TV standby power supply applications.In this paper, a system of current-sensing and self power supply technology used in monolithic switching power supply IC is discussed. This system can sense the current of the power device exactly and quickly, meanwhile, it also realizes the self power supply function in this system. Compared to the normal power supply methods, the technology addressed in this paper can change the current sensing ratio neatly according to the different load conditions. An outside 0.1μFcapacitance is used to store the energy for the supply of the IC chip itself the difficulty and cost for designing a Flyback switching power supply is depressed greatly by using this method.Based on the normal current sensing and power supply technology, a designed current sensing and self power supply method is expounded in this thesis and analyzed exactly according to its theory and work flow. The system which is made up of several subcircuits such as Power MOSFET, SensorFET, Line Under-Voltage, Over-Voltage and Under-Voltage circuit, 5.8V Regulator fulfills the function of current sensing and dynamic system power supply. In this paper all the subcircuits above are well analyzed and simulated clearly, which validate the correct of the whole system designed.The current sensing ratio can be adjusted easily by the change of the W/L of the SensorFET and the resistor net which is the part of the current limit comparator subcircuit. In this item, the sensing ratio is set to 1000:1.A external capacitor is connected to the BP pin and provides the energy for the operation of the chip when the Power MOSFET is on. The capacitor charge current comes from the external UV Resistor connected to the DC line. By the aid of the OV/UV cell, the operation voltage of the chip is between 4.8V and 5.8V.The current sensing and dynamic self power supply system have a good ability of universal use. In the design of Flyback topology switching power supply system, it could have a good performance.