Design And Research Of Protable Digital Product Power Management System Based On Ultra-Low Power Supply

Recently,energy shortage makes research on energy-saving and new energy resourse gather more attentions.At the same time,the rapid development of portable electronic products and the trends of their function strengthening challenge the power supply technology including the operation capability under lower voltage with lower power dissipation.In addition,it should be easy to "recharged",which makes the new energe resourses like solar cell and micro fuel cell come into sight,However, since they features very low output voltage,the key problem to implement their applications in portable products is the capability under very low output voltage as well as the drver capability of such a system.Based on the above application,this thesis proposed a power management system for portable electronic products,which is applicable to ultra-low-voltage power supply.Taking an ultra low voltage source like solar cell or micro-fuel cell as input,the system changes its low and unstable input voltage into an appropriate and stable level.Thus it can provide power for portable product's charger through the common interface to recharge its lithium betteries.Otherwise,,with USB interface or an external voltage source,it can derectly recharge the lithium battery for portable devices where covered by power grid.In this case the system could be used as a general charger..The proposed system is mainly composed of two sub-systems.The first one is an ultra-low-voltage BOOST converter that converts a relatively low and unstable voltage provided by solar cells or fuel cells into a stable supply voltage.The second one is a lithium battery charger for portable digital products.Both they can work independently.If put them into a system and make them work in cooperation,they can form a multi-function charge management system.To meet the low input voltage condition,a multi-period double-ended supplied low voltage BOOST system control scheme was proposed.Different from traditional BOOST systems,a low voltage startup module was added to this system to realize low input voltage startup working.Peak current control was adopted in loop control strategy design.An appropriate loop compensation was applied to the BOOST system to achieve fast response and high control precision.Meanwhile,a linear lithium battery charger controller was designed based on multiple control parameter competition method in this thesis.The battery charger controller can take the output of the low voltage BOOST system as an input to form a low voltage charger management system.It is also compatible with other DC inputs such as USB interfaces.Through monitoring the temperature,charging current and charging voltage at the same time,the multiple control parameter competition method controls the charge process according to real-time state of the system,which optimizes the charge efficiency and realizes the bettery protection.In addition,the proposed charger controller features its easy application,reliable temperature protection for both chip and battery and programmable charging time and current function.The low voltage BOOST system was designed and simulated in 0.35μm TSMC technology.And the linear lithium battery charger was simulated and implemented in 1.5μm BCD technology.The simulation and test results are consistent with theoretical design well.It is verified that the system can work in ultra-low input voltage and the charger can perform precise control and fine battery protection.