학술논문
벅 컨버터의 부하 과도 응답을 개선하기 위한 소프트 스위칭 보조 전류 주입 및 추출 제어 기법 / Soft-Switching Auxiliary Current Injection and Extraction Control for Improving Load Transient Response of Buck Converter
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
Korean
Abstract
마이크로프로세서 및 디지털 신호 프로세서 등에 스위치 모드 전원 공급 장치로 사용되는 POL (point-of-load) 컨버터는 구조와 제어가 간단한 벅 컨버터가 많이 사용된다. POL 컨버터는 부하 과도 상태에서도 출력 전압을 일정하게 유지하기 위해 우수한 동적 응답이 요구된다.제안하는 보조 전류 주입 및 추출(auxiliary current injection and extraction, ACIE) 제어 기법은 벅 컨버터의 부하 과도 응답을 개선하기 위해 보조 벅/부스트 컨버터 회로를 사용하여 설계 및 구현된다. 보조 벅/부스트 컨버터 회로는 보조 인덕터 전류를 임계 전도 모드(critical conduction mode, CRM)로 피크 전류 모드(peak current mode, PCM) 제어한다. 보조 스위치들의 소프트 스위칭 동작은 전력 손실을 최소화하여 보조 벅/부스트 컨버터의 효율을 높인다. 최적 동적 응답을 위한 설계 고려사항과 예상 전력 손실은 제안하는 ACIE 제어 기법의 성능을 입증하기 위해 제시하였다. 아날로그 소자만을 사용한 입력 전압, 출력 전압, 스위칭 주파수가 각각 15 V, 3.3 V, 200 kHz인 시작품 벅 컨버터를 통해 제안하는 ACIE 제어 기법을 증명하였다. 실험 결과, 부하 상승 과도 시 ∆vO와 ts는 각각 45 mV와 14 μs였고 부하 하강 과도 시 ∆vO와 ts는 각각 48 mV와 27 μs였다. 반면 기존의 VMC 기법은 부하 상승 과도 시 ∆vO와 ts가 각각 380 mV와 68 μs였고 부하 하강 과도 시 ∆vO와 ts가 각각 530 mV와 70 μs였다. 제안하는 ACIE 제어 기법의 전력 손실은 기존의 비교군에 비해 45-60%밖에 되지 않는다.제안하는 ACIE 제어 기법은 부하 과도 현상이 빈번하고 시비율이 낮은 병렬 연결된 벅 컨버터나 다상 벅 컨버터 시스템에 적용하기 적합하다.
Point-of-load (POL) converter which is used as a switch-mode power supply for microprocessors and digital signal processors, is mainly implemented by buck converter that are simple in scheme and control. POL converter is required to regulate the output voltage tightly during the load transient.The auxiliary current injection and extraction (ACIE) control circuit for the auxiliary buck/boost converter is proposed and implemented to improve the load transient response of the buck converter. The circuit shapes the auxiliary inductor current in critical conduction mode by peak current mode control. The soft-switching operation of the auxiliary switches minimizes the power loss and thus increases the efficiency of the auxiliary converter. The design guidelines for optimal dynamic response and estimated power loss are shown to prove the outperformance of the implemented circuit. The proposed ACIE control circuit was implemented with a prototype buck converter of which input voltage, output voltage, and switching frequency are 15 V, 3.3 V, and 200 kHz, respectively, using the analog components. The experiment results revealed that the output voltage undershoot and settling time during load step-up transient were 45 mV and 14 μs, respectively; however, in the case of conventional voltage-mode-controller (VMC), these values were 380 mV and 68 μs, respectively. When the load was stepped-down, the output voltage overshoot and settling time were 48 mV and 27 μs, while those of VMC were 530 mV and 70 μs, under the same condition. The power loss of the proposed ACIE control scheme was only 45-60% of those of conventional counterparts.The proposed ACIE control technique is suitable for low-duty-ratio buck converters in parallel or multi-phase buck converter systems with frequent load change.
Point-of-load (POL) converter which is used as a switch-mode power supply for microprocessors and digital signal processors, is mainly implemented by buck converter that are simple in scheme and control. POL converter is required to regulate the output voltage tightly during the load transient.The auxiliary current injection and extraction (ACIE) control circuit for the auxiliary buck/boost converter is proposed and implemented to improve the load transient response of the buck converter. The circuit shapes the auxiliary inductor current in critical conduction mode by peak current mode control. The soft-switching operation of the auxiliary switches minimizes the power loss and thus increases the efficiency of the auxiliary converter. The design guidelines for optimal dynamic response and estimated power loss are shown to prove the outperformance of the implemented circuit. The proposed ACIE control circuit was implemented with a prototype buck converter of which input voltage, output voltage, and switching frequency are 15 V, 3.3 V, and 200 kHz, respectively, using the analog components. The experiment results revealed that the output voltage undershoot and settling time during load step-up transient were 45 mV and 14 μs, respectively; however, in the case of conventional voltage-mode-controller (VMC), these values were 380 mV and 68 μs, respectively. When the load was stepped-down, the output voltage overshoot and settling time were 48 mV and 27 μs, while those of VMC were 530 mV and 70 μs, under the same condition. The power loss of the proposed ACIE control scheme was only 45-60% of those of conventional counterparts.The proposed ACIE control technique is suitable for low-duty-ratio buck converters in parallel or multi-phase buck converter systems with frequent load change.