The Design Of PFM Power Management IC Using The Minimum Off Time Control Theory

The switching power supply with small volume and weight as well as high efficiency and low power waste have been widely used in domain of electronic computer,communicate facility,electronic apparatus,domestic electric appliances. the present paper based on the use battery power supply portable electronic products application background, has studied the boost stage switching power supply chip with pulse frequency modulation mode control. The traditional PWM switch voltage-stabilized supply uses the voltage control pattern, takes the feedback signal realizes closed-loop control of the output voltage sampling to stable output voltage only. circuit inductance has not participated in the control, it is the independent variable. the switch converter is the second order system with two state variable, namely output filter capacity voltage and output filter inductance current. The second-order system is one has the condition stable system, only then carries on the careful design and the computation to the control circuit, satisfies the controlled condition, the closed-loop system can be stable. Therefore, this article uses the current control mode and adds the current feedback loop for inductance current no longer is an independent variable, the switch converter to become a first-order unconditional stable system.This chip integrates NMOS power tube, has the low resistance. the bigger of the switch, the smaller the on-state resistance is. Considering the area that the actual chip takes up, it is impossible to enlarge the aspect ratio of the switch infinitely. Therefore according to the situation that the chip takes the circumstance of the load normally, it was carried on compromised. And the increasing of the size of switch must cause the big parasitic capacitance. This will effect the speed of MOSFET switch, so the paper designs the drivers for both switches respectively. Using the PMOS isolator to be possible to separate the power source and the inductance connection, the current will decrease to...