The Design Of The Circuit Of DC-DC Mode PWM/PFM Boost Converter

The power supply can be divided into linear regulated power supply and a switching power supply, their purpose is to transform electrical energy. Switching power supply is the use of modern power electronics technology and microelectronics technology, the control of semiconductor power switch device on and off time ratio, to maintain a stable output voltage of a power supply. It represents the development direction of the power supply, has now become the mainstream products in the field of power. In this paper, the basic knowledge of switching power supply based on the design of a DC/DC boost converter chip. The input voltage is 3V, output voltage is 5V, the frequency of 700 kHz, the conversion efficiency reached 86.8%. Chip control method using modulation method of mixed type PWM and PFM, enhanced the conversion efficiency and the use scope. At the same time, the soft start circuit is added to ensure the stability of the chip.This paper first describes the development of switching power supply and basic theoretical knowledge. And then introduces the boost converter circuit structure and working principle of the process. Finally focus on the design and simulation of the working principle of DC/DC circuit and its various modules. The main research work is as follows:1, In the basic principle and design method of DC/DC boost circuit, through experiments and analysis, designed by DC/DC PWM/PFM mixed type boost conversion chip control. The chip consists of a band-gap reference voltage module, PWM/PFM modulation module, error amplifier,oscillator module, soft start module, driver module etc..2, Analysis and improve the instability of the output circuit, design temperature coefficient better band-gap reference circuit, effective the circuit of each module can reduce the temperature effect, makes the output to maintain a good state.3, The use of simulation and verification of the chip circuit by Cadence software. The results show that the circuit realization input 3V to boost to output 5V, meet the design requirements of the chip. Finally, the size of the chip using 5.0?m CMOS technology to achieve.