Power Supply IC Design For Smartphone Screen

A Boost DC/DC converters chip was studied in this paper. The chip is a step-up DC/DC converter designed for driving up output voltage to 36 V from a single cell Lithium Ion battery. Thus, this chip is mainly used in handheld electronic devices and TFT-LCD/OLED bias supplies. The research status and development trend of Power Management were first discussed in this paper, and then the different switching converter of topologies basic work manner and several work mode, modulation mode and control mode were studied in this paper. The parameters to be analyzed in the second, and according to the functional requirements and the based parameters of the chip began to chip design. Peak current control mode was used in this chip, and the system can switch between the PWM and the PSM to improve the efficiency depending on the load. The key modules, such as Bandgap, EA, OSC, Current Sense, Current Limit, UVLO, OTP and Soft Start etc., were designed and simulated in this paper. The main advantage of the chip designed in this paper as follows:a). The chip switches at 1.25 MHz, allowing the use of tiny, low cost and low height inductors and capacitors. A constant frequency internally compensated current mode PWM and PSM architecture results in low, predictable output noise that is easy to filter. Low ESR ceramic capacitors can be used at the output, further reducing noise to millivolt level.b). Conversion efficiency up to 93%, therefor, power supply efficiency was improved and the battery life was extended.c). The chip precision and yield of the chip is greatly improved, because the zero temperature coefficient current circuit.d). Due to the current limit up to 1A, the chip can support larger power loads. Not only can be used for smart phone screen, and on the big screen tablet PC also be widely used.e). Join the UVLO, OTP, Soft Start and Glitch Shielding to improve the reliability of the chip.f). The high voltage switch on the chip is rated at 36 V, therefore this chip has a strong competitiveness in the market. The chip is a 0.8um BCD CSMC technology, and using Cadence simulation tools for system simulation. The simulation results show that the chip can stable 36 V output voltage in 2.7V to 5.5V input voltage range and the conversion efficiency as high as 90%. The function and performance of the whole chip have met the entire specification.