A Voltage Mode Control Of Pwm Switching Power Supply

Single-chip switching power supply management Integrated Circuit (IC) is the inevitable orientation of the switching power supply management, it is famous by the virtues of high integration level, high cost-effective, lowest component circuit, high performance, easy to form high efficiency power supply and so on. It has been widely applied over the world. It takes up more important role especially in the portable digital device, which is hot recently. Since color LCD screen is applied in the cellphone and portable Gamebox, there are abundant demands for high light brightness and solid color backlight source. White LED is considered as the best source in current situation. This paper is to design such a single chip IC working at high frequency and high efficiency and accuracy with pulse width modulation (PWM) mode, which is using the software of Cadence and HSPICE, basing on the 1μ40V high Voltage CMOS Technics.The features of this circuit are designed as: the input voltage ranged from 2.5V to 7V, and the working frequency is fixed at 1.0MHz, PWM maximum Duty Cycle is 87%.This IC chip can be used to drive white LED displays in cellphone, digital camera, Mp3 player, PDA and other portable digital devices. This chip can drive up to 4LEDs from a 3.6V supply, and drive up to 6LEDs from a 5V supply.In the circuit designing section, the basic theories of White LED drivers, Pulse Width Modulation (PWM) mode and DC/DC Converter are given first. Then the general structure of the IC is designed based on its functional requirement. Combined with its application condition, the working course is showed. Subcircuit models are designed and simulated, which includes Bias Current Source, Voltage Reference, Error Amplifier, PWM Comparator, Driver Circuit, Protection Circuits for Over-temperature, Over-current. At last, combined with periphery component, the circuit is simulated, and the result meets the anticipant requirement. Then the reason of Peak pulse voltage is analyzed and the optimization is come up with.Finally, the conclusion is summarized.