Design of the Power Management ICs for Portable Devices

Abstract

With the rapid development of portable devices how to extend the usage time of these devices and reduce the volume of the power conversion circuits has become an important research topic In this dissertation several power management integrated circuits (ICs) are implemented to improve the efficiency and more external components are integrated In the designed light-emitting diode (LED) driver an ambient light sensor and its readout circuit are integrated in a LED driver for the liquid crystal display (LCD) backlight module By sensing the surrounding light level the LED driver can automatically adjusts the LED current and hence the power dissipation of LED backlight module can be effectively reduced A boost-type LED driver is proposed in this dissertation to verify this function The input voltage is 3 to 5 V and it can drive 2 to 15 LEDs In the designed noninverting buck-boost dc-dc converter the proposed hysteretic-current -mode control method can improve the efficiency in the mode transition region and smoothly switch its operating mode when the input and output voltages are close The input voltage may range from 2 5 to 5 V the output voltage is 3 3 V and the maximum output current is 400 mA According to the measured results the maximum frequency reaches 98 1% and the efficiencies measured in the entire input range and loading range are all above 80% In the designed Li-ion battery charger the proposed sharp mode transition eliminates the transition region between constant current (CC) and constant voltage (CV) stages in traditional Li-ion battery chargers This technique reduces the charging time and simplifies the compensator design Furthermore by adopting the HV partial current control technique the charging current at the CC stage can be regulated only by sensing part of inductor current and no external sensing resistor is required With a 25-V input voltage the output voltage range of this chip is 6 to 22 V The maximum charging current is 2 5 A The peak efficiency reaches 97% occurring at 1-A charging current

Date of Award	2019
Original language	English
Supervisor	Chia-Ling Wei (Supervisor)