| Nowadays,the rapid development of electronic technology today, from our normal daily lives to the most cutting-edge science and technology can not do without a reliable power supply. Power management chips in portable electronic products, play a very important role. Currently, a variety of portable electronic devices such as mobile phones, laptops, MP4, digital cameras, camcorders, VCRs, etc., have been widely used power management chip. Power management chip is becoming a major trend. Power supply directly affects the quality of the performance of electronic equipment. In almost all portable electronic devices, all of the power management technology has different requirements. For example, commonly used in microprocessor (CPU) of the power supply is 1.1V, commonly used power supply is 2.5V and the memory of 3.0V, Compact Flash or USB interfaces such as expansion requires 5V power supply, while the LCD bias circuit or a white LED display 20V-30V backlight circuit requirements of power supply. To maintain the system in each circuit to work, it must be applied to the power management chip technology to provide stable power supply for the device. From the power management chip development, the small size, high efficiency, high reliability and long life of power equipment has become the main direction we designed a power management chip.Based on the present development trend of power management chip, a synchronous rectification design of the step-up DC-DC converter for portable electronics provides a stable DC voltage. This paper is to design a DC-DC converter using synchronous rectification circuit model, the Schottky diode replaced by a power MOSFET, greatly improve the efficiency of the converter, synchronous rectification is not used by the model before the efficiency of 87.4% increased to 93.7%. And after the addition of synchronous rectification, power MOSFET structure for the chip, also saves the board area of the PCB. In the boost converter of this thesis, the input voltage range is 2-4 V, the output voltage range is 3-5V. Load current range is 50mA-200mA. Output voltage ripple is 8mV. Operating frequency is 1MHz.First, this paper identified the DC-DC converter models and the overall structure and feedback control method, designed a model of the synchronous rectification type PWM boost converter. The internal circuit includes resistance sampling, error amplifier, bandgap reference, summing comparator, soft start circuit, the slope compensation circuit, oscillator and current-sense circuit. The paper joined the synchronous rectifier circuit, because Schottky diode will have 0.3-0.6V voltage drop, resulting in a large conduction loss, a serious impact on converter efficiency, we apply a power MOSFET to replace the Schottky diodes. Power control is voltage-controlled MOS devices, the turn-voltage characteristics when the linear relationship. Synchronous rectification increases converter efficiency and reduces the cost of the entire power system. After adding the synchronous rectifier, converter efficiency is improved by 6%. Finally, how to draw the layout and design layout Precautions were introduced, designed each module of the converter and drew a map of the final overall boost converter to up the overall layout. This paper uses a 0.35um CMOS technology library, used the software Cadence Spectre for circuit simulation and Cadence Virtusuo for layout.
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