Research And Design Of Low Power Super Capacitor Independent Power Supply

With the development of mobile communication technology, mobile phone has become an indispensable tool in our daily life. The battery is an energy storage device which provides electric for mobile phone. And its quality directly affects the use effect and the lifetime of mobile phone. But common mobile phone batteries have the shortcomings of long charging time and short service life, which will seriously affect the user experience of mobile phone. Therefore, how to find a more efficient, more stable and faster independent power as mobile phone battery has become a research focus in recent years.Performances and technical index of super capacitor and lithium batteries, nickel hydrogen batteries have been compared in this paper. And the advantages of small volume, light weight,"zero" memory effect and advantages of high current fast charge have been found in super capacitor. Based on above, a assumption is put forward that the super capacitor works as an independent power supply, replaces the mobile phone batteries and used in mobile phone load.Based on the above ideas, a circuit with constant voltage and high current is designed, which is based on LM317three terminal regulator and a NPN type high power triode D880. By building up practical hardware circuit, the charging circuit is tested. The test results show that there is a4.5A direct current output in this circuit. And the output voltage can be stabilized at2.7V, which satisfies the charging characteristics of super capacitor. The feasibility and effectiveness of this circuit are proved.At the same time, in order to verify the assumption that super capacitor can be envisaged as an independent power supply used in mobile phone, by studying the relevant technical requirements of mobile phone load and according to the characteristics of mobile phone’s working voltage of3.7V and super capacitor’s voltage of2.7V, a circuit is designed.After comprehensive analysis of various circuit schemes, boost circuit is selected as the main circuit of super capacitor independent power circuit. In order to get a continuous and stable output of3.7V voltage, a voltage stabilizing circuit is designed. The circuit is based on QX2304chip and STM8L152MCU. The output voltage of super capacitor is raised up from2.7V to3.3V by QX2304chip, and the power of STM8L152MCU will be obtained from the output of QX2304chip. Output voltage of boost circuit is detected by STM8L152MCU. The output voltage of boost circuit will be compared with the setting values of3.7v, and the PID control algorithm will output a certain proportion duty of PWM wave to adjust the on and off of IGBT in boost circuit. Through the on and off of IGBT, the output of boost circuit is stabilized at3.7v.Based on the circuit, a Matlab/Simulink simulation circuit is established in this paper. The feasibility of the circuit is verified. Meanwhile, an actual hardware circuit is built up in this paper. Through the test of the actual hardware circuit, a constant and stable output voltage of3.7V is detected. The result is in accordance with the original intention of the design. The assumption that the super capacitor works as an independent power supply, replaces the mobile phone batteries and used in mobile phone load is proved.