Highly Power-Efficient Power Management ICs for Display and Mobile Applications

Abstract

Recently, power management integrated circuits (PMICs) is being highlighted in various applications. In particular, the market of display products and mobile applications is growing exponentially, and PMICs for display and mobile applications are growing together by leaps and bounds together with progress of electronics. To make successful progress in PMIC technology, fundamental analysis for various aspects of PMIC technologies and technical experiences is required. This dissertation presents various technologies required for development of smart PMIC. In this dissertation, accurate device models for high voltage LDMOSFETs and distinguished design ability for two types of PMICs are proposed. The performances of the proposed model and PMICs are verified by measurements, and the experimental results demonstrate the superiority of the proposed model and PMICs. In chapter 2, an accurate model of lateral double-diffused MOSFETs (LDMOSFETs) is proposed. To analyze characteristics of LDMOSFET, various process and device simulations are performed. In the proposed model, various physical phenomena are represented by considering device simulations and experimental results, and DC, AC, and thermal characteristics are included. Especially, the depleted length in drift region and the accumulated carrier in accumulation region are analyzed to improve accuracy of the proposed model. A comparison between the measurement results and the simulation results of proposed model show that the accuracy for DC and AC characteristics of the proposed model are 9.5% and 6.8%, respectively. The experimental results show that the proposed model is suitable for development of smart PMICs. In chapter 3, two PMICs which have high power efficiency are proposed for display and mobile applications. First is a highly power-efficient LED backlight driving system for LCD TVs. In the proposed system, the output voltage of a boost converter is optimized considering the forward voltage of each LED channel. To optimize the output voltage, turn-on sequence of LED channels is rearranged according to the forward voltages of LED channels, and the output voltage tracks the required output voltage to drive target current in each LED channel. The PMICs in the proposed system were fabricated using a 0.35 μm BCD process with maximum drain voltage of 60 V. In experimental results, the proposed system improves power efficiency to 3.8%. The second proposed system is a highly power-efficient single-inductor multiple-outputs (SIMO) DC-DC converter with gate charge sharing method for mobile application. The proposed converter uses a single inductor to generate five outputs. The gate charges of output switches are shared to improve power efficiency and to reduce switching power loss. The proposed converter was fabricated using a 0.18 μm CMOS process with high voltage devices of 5 V. In experimental results, the proposed converter improves power efficiency to 2.1%. The experimental results show that the proposed PMICs are suitable for display and mobile applications. |최근에 전력 관리 집적 회로는 다양한 응용분야에서 각광을 받고 있다. 특히, 디스플레이 및 휴대용 장치 산업이 발달함에 따라 이들 장치를 위한 전력 관리 집적 회로는 급속히 성장하고 있다. 전력 관리 집적 회로 기술의 발전을 위해서는 해당 기술의 다양한 측면에 대한 근본적인 분석과 기술적인 경험이 요구된다. 본 학위논문에서는 차세대 전력 관리 집적 회로의 개발을 위해 요구되는 다양한 기술들을 제시한다. 2장에서는 lateral double-diffused MOSFETs (LDMOSFETs)에 대한 정확도 높은 모델이 제안되었다. LDMOSFET의 특성을 분석하기 위하여 해당 공정 및 소자에 대한 다양한 모의 실험을 진행하였다. 모의 실험 및 측정 결과를 바탕으로 다양한 물리적 현상을 제안된 모델에 표현하였고, 이를 바탕으로 제안된 모델은 DC, AC, 열적 특성들을 포함하였다. 제안된 모델을 이용한 모의 실험 결과와 측정 결과와의 비교를 통하여 제안된 모델의 정확도를 평가하였으며, DC 특성 및 AC 특성에 대한 최대 오차는 각각 9.5% 및 6.8%이다. 다양한 실험 결과를 통하여 제안된 모델이 차세대 전력 관리 집적 회로의 개발에 매우 적합함을 확인하였다. 3장에서는 디스플레이 및 휴대용 응용분야에 요구되는 두 종류의 고효율 전력 관리 집적 회로를 제안하였다. 첫 번째 전력 관리 집적 회로는 LCD TV용 고효율 LED backlight 구동 시스템이다. 제안된 시스템에서는 각 LED 채널의 순전압 특성을 고려하여 boost converter의 출력 전압을 최적화 하였다. 출력 전압을 최적화 하기 위하여, LED 채널의 순전압 특성에 따라 각 LED 채널의 동작 순서를 재배열 하였으며, 출력 전압이 각 LED 채널을 구동하기 위하여 요구되는 최적 전압을 추적하도록 개발하였다. 제안된 시스템의 전력 관리 집적 회로는 60 V급 0.35 μm BCD 공정을 이용하여 제작하였으며, 제안한 아이디어를 통하여 3.8%의 전력 효율이 개선되었다. 두 번째 전력 관리 집적 회는 휴대용 기기를 위한 고효율 DC-DC converter이다. 제안된 converter는 한 개의 인덕터를 사용하여 다섯 개의 출력 전압을 형성하며, 제안된 converter의 전력 효율을 높이고 스위칭 동작에 따른 전력 손실을 줄이기 위하여 출력단 스위치의 게이트 전하를 공유하는 게이트 전하 공유 방법을 새롭게 제안하였다. 제안된 converter는 5 V급0.18 μm CMOS 공정을 이용하여 제작하였으며, 제안된 게이트 전하 공유 방법을 통하여 2.1%의 전력 효율이 개선되었다. 다양한 실험 결과를 통하여, 제안된 전력 관리 집적 회로 기술이 차세대 전력 관리 집적 회로의 개발에 매우 적합함을 확인하였다.; Recently, power management integrated circuits (PMICs) is being highlighted in various applications. In particular, the market of display products and mobile applications is growing exponentially, and PMICs for display and mobile applications are growing together by leaps and bounds together with progress of electronics. To make successful progress in PMIC technology, fundamental analysis for various aspects of PMIC technologies and technical experiences is required. This dissertation presents various technologies required for development of smart PMIC. In this dissertation, accurate device models for high voltage LDMOSFETs and distinguished design ability for two types of PMICs are proposed. The performances of the proposed model and PMICs are verified by measurements, and the experimental results demonstrate the superiority of the proposed model and PMICs. In chapter 2, an accurate model of lateral double-diffused MOSFETs (LDMOSFETs) is proposed. To analyze characteristics of LDMOSFET, various process and device simulations are performed. In the proposed model, various physical phenomena are represented by considering device simulations and experimental results, and DC, AC, and thermal characteristics are included. Especially, the depleted length in drift region and the accumulated carrier in accumulation region are analyzed to improve accuracy of the proposed model. A comparison between the measurement results and the simulation results of proposed model show that the accuracy for DC and AC characteristics of the proposed model are 9.5% and 6.8%, respectively. The experimental results show that the proposed model is suitable for development of smart PMICs. In chapter 3, two PMICs which have high power efficiency are proposed for display and mobile applications. First is a highly power-efficient LED backlight driving system for LCD TVs. In the proposed system, the output voltage of a boost converter is optimized considering the forward voltage of each LED channel. To optimize the output voltage, turn-on sequence of LED channels is rearranged according to the forward voltages of LED channels, and the output voltage tracks the required output voltage to drive target current in each LED channel. The PMICs in the proposed system were fabricated using a 0.35 μm BCD process with maximum drain voltage of 60 V. In experimental results, the proposed system improves power efficiency to 3.8%. The second proposed system is a highly power-efficient single-inductor multiple-outputs (SIMO) DC-DC converter with gate charge sharing method for mobile application. The proposed converter uses a single inductor to generate five outputs. The gate charges of output switches are shared to improve power efficiency and to reduce switching power loss. The proposed converter was fabricated using a 0.18 μm CMOS process with high voltage devices of 5 V. In experimental results, the proposed converter improves power efficiency to 2.1%. The experimental results show that the proposed PMICs are suitable for display and mobile applications.