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F C Lee - One of the best experts on this subject based on the ideXlab platform.

  • digital implementation of light load efficiency improvement for high frequency llc converters with simplified optimal Trajectory Control
    IEEE Journal of Emerging and Selected Topics in Power Electronics, 2018
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    The light-load efficiency has drawn more and more attention for the LLC resonant converters in information technology industry. Burst mode is an effective and popular method to improve the light-load efficiency. The conventional burst-mode Control has limited efficiency improvement on LLC converter due to the dynamics of the resonant tank. The simplified optimal Trajectory Control (SOTC) for burst mode can solve this issue by using optimal switching pattern for burst-on time. High-frequency LLC converters are emerging in recent years, thanks to the high power density and integrated magnetics. In this paper, the digital implementation of SOTC for burst mode and its limitation in high-frequency LLC converter are investigated. SOTC for adaptive burst mode is proposed and implemented by low-cost microControllers (MCUs) for high-frequency LLC converters. Furthermore, the digital implementation of SOTC for fast transient response between burst mode and normal operation of high-frequency LLC converter is proposed. The experimental results are demonstrated on a 500-kHz 1-kW 400 V/12 V LLC converter with a 60-MHz MCU, and the proposed Control can achieve burst-mode operation from no load up to 26% load, 92.5% efficiency at 10% load, 91.8% efficiency at 2.4% load, and fast transient response between burst mode and normal operation.

  • digital implementation of soft start up and short circuit protection for high frequency llc converters with optimal Trajectory Control otc
    IEEE Transactions on Power Electronics, 2017
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    Achieving soft start-up and short-circuit protection have always been challenging for resonant converters due to severe stresses in the resonant tank. Optimal Trajectory Control (OTC) has been proven to be the most effective Control method to optimize energy delivery with given stresses. This paper proposes a method to implement soft start-up and short-circuit protection for LLC converters by using low-cost microControllers (MCUs) with minimum stresses and optimal energy delivery. Our current understanding of the relationship between the switching frequency and the output voltage is based on the state-plane analysis, and the requirement for the Controllers is significantly reduced when using the lookup table. Further improvement enables the application of the proposed Control method to high-frequency LLC converters without increasing the cost for the Controllers. This paper proposes a method to protect the LLC converter from abrupt short-circuit with low-cost MCUs, which improves transient response to short-circuit significantly, and investigates limitations when operating the high-frequency LLC converter under short-circuit conditions. The proposed methods minimize the CPU resource requirement and can be further integrated with other state-Trajectory Control functions within one MCU. Experimental results are demonstrated on a 500-kHz 1-kW 400-V/12-V LLC converter with 60-MHz MCU TMS320F28027.

  • multi step simplified optimal Trajectory Control sotc for fast transient response of high frequency llc converters
    European Conference on Cognitive Ergonomics, 2015
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    This paper proposes Multi-step Simplified Optimal Trajectory Control (SOTC) for the high frequency LLC converters. SOTC can improve the transient performance of the LLC converters by immediately changing the pulse width of the primary driving signal during the load transient. However, the implementation of SOTC requires high-performance digital Controllers. The proposed Multi-step SOTC calculates the Trajectory based on only the output voltage and the load current, and settles the resonant tank within multi steps. With the proposed Multi-step SOTC, low-cost Controllers can be used to Control the high frequency LLC converters with the state-Trajectory Control concept. The number of steps in multi-step SOTC is selected based on the speed of the Controller and the switching frequency of the LLC converters. Experimental results are demonstrated on a 500kHz 1kW 400V/12V LLC converter.

  • light load efficiency improvement for high frequency llc converters with simplified optimal Trajectory Control sotc
    European Conference on Cognitive Ergonomics, 2015
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    The light load efficiency has drawn more and more attention for the LLC resonant converters. And the high frequency LLC converters are emerging in recent years. The conventional burst mode Control cannot fix to the efficiency-optimal state during the burst-on time. Optimal Trajectory Control (OTC) for burst mode can solve this problem by using fixed 3-pulse pattern; however, the burst operation range of OTC is limited when it is applied to the high frequency LLC converters due to the fixed 3-pulse pattern and digital delay. To extend the burst operation range for the high frequency LLC converters, Simplified Optimal Trajectory Control (SOTC) for burst mode with adaptive burst on-power and adaptive multi-step are proposed in this paper. The burst mode operation range can be extended by increasing either the burst on-power or the burst on-time. The experimental results are demonstrated on a 500kHz 1kW 400V/12V LLC converter with 92.5% efficiency at 10% load and 91.8% efficiency at 2.4% load.

  • soft start up for high frequency llc resonant converter with optimal Trajectory Control
    Applied Power Electronics Conference, 2015
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    This paper investigates the soft start-up for high frequency LLC resonant converter with optimal Trajectory Control. Two methods are proposed to realize soft start-up for high frequency LLC converter by commercial low-cost microControllers (MCU). Both methods can achieve soft start-up with minimum stress and optimal energy delivery. One method is mixed-signal implementation by sensing resonant tank to minimize the digital delay. Another method is digital implementation with look-up table. Experimental results are demonstrated on 500kHz 1kW 400V/12V LLC converter.

Chao Fei - One of the best experts on this subject based on the ideXlab platform.

  • digital implementation of light load efficiency improvement for high frequency llc converters with simplified optimal Trajectory Control
    IEEE Journal of Emerging and Selected Topics in Power Electronics, 2018
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    The light-load efficiency has drawn more and more attention for the LLC resonant converters in information technology industry. Burst mode is an effective and popular method to improve the light-load efficiency. The conventional burst-mode Control has limited efficiency improvement on LLC converter due to the dynamics of the resonant tank. The simplified optimal Trajectory Control (SOTC) for burst mode can solve this issue by using optimal switching pattern for burst-on time. High-frequency LLC converters are emerging in recent years, thanks to the high power density and integrated magnetics. In this paper, the digital implementation of SOTC for burst mode and its limitation in high-frequency LLC converter are investigated. SOTC for adaptive burst mode is proposed and implemented by low-cost microControllers (MCUs) for high-frequency LLC converters. Furthermore, the digital implementation of SOTC for fast transient response between burst mode and normal operation of high-frequency LLC converter is proposed. The experimental results are demonstrated on a 500-kHz 1-kW 400 V/12 V LLC converter with a 60-MHz MCU, and the proposed Control can achieve burst-mode operation from no load up to 26% load, 92.5% efficiency at 10% load, 91.8% efficiency at 2.4% load, and fast transient response between burst mode and normal operation.

  • digital implementation of soft start up and short circuit protection for high frequency llc converters with optimal Trajectory Control otc
    IEEE Transactions on Power Electronics, 2017
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    Achieving soft start-up and short-circuit protection have always been challenging for resonant converters due to severe stresses in the resonant tank. Optimal Trajectory Control (OTC) has been proven to be the most effective Control method to optimize energy delivery with given stresses. This paper proposes a method to implement soft start-up and short-circuit protection for LLC converters by using low-cost microControllers (MCUs) with minimum stresses and optimal energy delivery. Our current understanding of the relationship between the switching frequency and the output voltage is based on the state-plane analysis, and the requirement for the Controllers is significantly reduced when using the lookup table. Further improvement enables the application of the proposed Control method to high-frequency LLC converters without increasing the cost for the Controllers. This paper proposes a method to protect the LLC converter from abrupt short-circuit with low-cost MCUs, which improves transient response to short-circuit significantly, and investigates limitations when operating the high-frequency LLC converter under short-circuit conditions. The proposed methods minimize the CPU resource requirement and can be further integrated with other state-Trajectory Control functions within one MCU. Experimental results are demonstrated on a 500-kHz 1-kW 400-V/12-V LLC converter with 60-MHz MCU TMS320F28027.

  • multi step simplified optimal Trajectory Control sotc for fast transient response of high frequency llc converters
    European Conference on Cognitive Ergonomics, 2015
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    This paper proposes Multi-step Simplified Optimal Trajectory Control (SOTC) for the high frequency LLC converters. SOTC can improve the transient performance of the LLC converters by immediately changing the pulse width of the primary driving signal during the load transient. However, the implementation of SOTC requires high-performance digital Controllers. The proposed Multi-step SOTC calculates the Trajectory based on only the output voltage and the load current, and settles the resonant tank within multi steps. With the proposed Multi-step SOTC, low-cost Controllers can be used to Control the high frequency LLC converters with the state-Trajectory Control concept. The number of steps in multi-step SOTC is selected based on the speed of the Controller and the switching frequency of the LLC converters. Experimental results are demonstrated on a 500kHz 1kW 400V/12V LLC converter.

  • light load efficiency improvement for high frequency llc converters with simplified optimal Trajectory Control sotc
    European Conference on Cognitive Ergonomics, 2015
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    The light load efficiency has drawn more and more attention for the LLC resonant converters. And the high frequency LLC converters are emerging in recent years. The conventional burst mode Control cannot fix to the efficiency-optimal state during the burst-on time. Optimal Trajectory Control (OTC) for burst mode can solve this problem by using fixed 3-pulse pattern; however, the burst operation range of OTC is limited when it is applied to the high frequency LLC converters due to the fixed 3-pulse pattern and digital delay. To extend the burst operation range for the high frequency LLC converters, Simplified Optimal Trajectory Control (SOTC) for burst mode with adaptive burst on-power and adaptive multi-step are proposed in this paper. The burst mode operation range can be extended by increasing either the burst on-power or the burst on-time. The experimental results are demonstrated on a 500kHz 1kW 400V/12V LLC converter with 92.5% efficiency at 10% load and 91.8% efficiency at 2.4% load.

  • soft start up for high frequency llc resonant converter with optimal Trajectory Control
    Applied Power Electronics Conference, 2015
    Co-Authors: Chao Fei, F C Lee
    Abstract:

    This paper investigates the soft start-up for high frequency LLC resonant converter with optimal Trajectory Control. Two methods are proposed to realize soft start-up for high frequency LLC converter by commercial low-cost microControllers (MCU). Both methods can achieve soft start-up with minimum stress and optimal energy delivery. One method is mixed-signal implementation by sensing resonant tank to minimize the digital delay. Another method is digital implementation with look-up table. Experimental results are demonstrated on 500kHz 1kW 400V/12V LLC converter.

K J Tseng - One of the best experts on this subject based on the ideXlab platform.

  • generalized optimal Trajectory Control for closed loop Control of series parallel resonant converter
    IEEE Transactions on Power Electronics, 2006
    Co-Authors: Hao Chen, E K K Sng, K J Tseng
    Abstract:

    The series parallel resonant converter (SPRC) is known to have combined the merits of the series resonant converter (SRC) and the parallel resonant converter (PRC). However, the series PRC (SPRC) has a three-element LCC structure with complex transient dynamics and without Control of the resonant circuit's dynamics, the converter's closed loop bandwidth to switching frequency ratio will be much reduced compared to that of pulsewidth modulation converters. In this paper, the generalized optimal Trajectory Control (GOTC) for the SPRC is presented. It allows the nonlinear resonant circuit of the SPRC having an arbitrary starting state to reach a desired steady state in one cycle with two optimally Controlled switching instances. It is a generalized form of optimal Trajectory Control (OTC) which is restricted to transitions between steady states. Based on GOTC, a traditional Controller with inner current and outer voltage state-feedback is designed for an SPRC based dc-dc converter. The GOTC based feedback Controller allows use of higher feedback gains compared with one using OTC or frequency Control and gives higher closed loop bandwidth. This results in either better disturbance rejection for the converter or the possibility of reducing output filter sizing. Experimental results confirm the theoretical claims

  • generalized optimal Trajectory Control for closed loop Control of series parallel resonant converters
    Power Electronics Specialists Conference, 2004
    Co-Authors: Hao Chen, E K K Sng, K J Tseng
    Abstract:

    In this paper, the generalized optimal Trajectory Control (GOTC) for the series-parallel resonant converter (SPRC) is presented. It allows the nonlinear resonant circuit of the SPRC having an arbitrary starting state to reach a desired steady state in the shortest possible time. Based on GOTC, a traditional feedback Controller with inner current and outer voltage state-feedback is designed for an SPRC based DC-DC converter. The GOTC based feedback Controller allows higher feedback loop gains to be used compared with simple frequency Control of the resonant circuit. This results in either better disturbance rejection for the converter or the possibility of reducing output filter sizing. Simulation results are used to verify the theoretical claims at this stage.

Lingyang Song - One of the best experts on this subject based on the ideXlab platform.

  • reinforcement learning for a cellular internet of uavs protocol design Trajectory Control and resource management
    IEEE Wireless Communications, 2020
    Co-Authors: Hongliang Zhang, Lingyang Song, Zhu Han, Vincent H Poor
    Abstract:

    Unmanned aerial vehicles (UAVs) can be powerful Internet of Things components to execute sensing tasks over the next-generation cellular networks, which are generally referred to as the cellular Internet of UAVs. However, due to the high mobility of UAVs and shadowing in airto- ground channels, UAVs operate in a dynamic and uncertain environment. Therefore, UAVs need to improve the quality of service of sensing and communication without complete information, which makes reinforcement learning suitable for use in the cellular Internet of UAVs. In this article, we propose a distributed sense-and-send protocol to coordinate UAVs for sensing and transmission. Then we apply reinforcement learning in the cellular Internet of UAVs to solve key problems such as Trajectory Control and resource management. Finally, we point out several potential future research directions.

  • reinforcement learning for a cellular internet of uavs protocol design Trajectory Control and resource management
    arXiv: Signal Processing, 2019
    Co-Authors: Hongliang Zhang, Lingyang Song, Zhu Han, Vincent H Poor
    Abstract:

    Unmanned aerial vehicles (UAVs) can be powerful Internet-of-Things components to execute sensing tasks over the next-generation cellular networks, which are generally referred to as the cellular Internet of UAVs. However, due to the high mobility of UAVs and the shadowing in the air-to-ground channels, UAVs operate in an environment with dynamics and uncertainties. Therefore, UAVs need to improve the quality of service (QoS) of sensing and communication without complete information, which makes reinforcement learning suitable to be employed in the cellular Internet of UAVs. In this article, we propose a distributed sense-and-send protocol to coordinate the UAVs for sensing and transmission. Then, we apply reinforcement learning in the cellular Internet of UAVs to solve key problems such as Trajectory Control and resource management. Finally, we point out several potential future research directions.

  • cellular uav to x communications design and optimization for multi uav networks in 5g
    arXiv: Signal Processing, 2018
    Co-Authors: Shuhang Zhang, Boya Di, Hongliang Zhang, Lingyang Song
    Abstract:

    In this paper, we consider a single-cell cellular network with a number of cellular users~(CUs) and unmanned aerial vehicles~(UAVs), in which multiple UAVs upload their collected data to the base station (BS). Two transmission modes are considered to support the multi-UAV communications, i.e., UAV-to-infrastructure (U2I) and UAV-to-UAV~(U2U) transmissions. Specifically, a UAV either uploads its collected data to the BS through U2I overlay transmission or offloads the data to a neighboring UAV through U2U underlay transmission when facing on-board battery outage. We formulate the subcarrier allocation and Trajectory Control problem to maximize the uplink sum-rate taking the delay of sensing tasks into consideration. To solve this NP-hard problem efficiently, we decouple it into three sub-problems: U2I and cellular user (CU) subcarrier allocation, U2U subcarrier allocation, and UAV Trajectory Control. An iterative subcarrier allocation and Trajectory Control algorithm (ISATCA) is proposed to solve these sub-problems jointly. Simulation results show that the proposed ISATCA can upload 20\% more data than the one without U2U offloading, and 10\% more than that obtained by the random algorithm.

Hao Chen - One of the best experts on this subject based on the ideXlab platform.

  • generalized optimal Trajectory Control for closed loop Control of series parallel resonant converter
    IEEE Transactions on Power Electronics, 2006
    Co-Authors: Hao Chen, E K K Sng, K J Tseng
    Abstract:

    The series parallel resonant converter (SPRC) is known to have combined the merits of the series resonant converter (SRC) and the parallel resonant converter (PRC). However, the series PRC (SPRC) has a three-element LCC structure with complex transient dynamics and without Control of the resonant circuit's dynamics, the converter's closed loop bandwidth to switching frequency ratio will be much reduced compared to that of pulsewidth modulation converters. In this paper, the generalized optimal Trajectory Control (GOTC) for the SPRC is presented. It allows the nonlinear resonant circuit of the SPRC having an arbitrary starting state to reach a desired steady state in one cycle with two optimally Controlled switching instances. It is a generalized form of optimal Trajectory Control (OTC) which is restricted to transitions between steady states. Based on GOTC, a traditional Controller with inner current and outer voltage state-feedback is designed for an SPRC based dc-dc converter. The GOTC based feedback Controller allows use of higher feedback gains compared with one using OTC or frequency Control and gives higher closed loop bandwidth. This results in either better disturbance rejection for the converter or the possibility of reducing output filter sizing. Experimental results confirm the theoretical claims

  • generalized optimal Trajectory Control for closed loop Control of series parallel resonant converters
    Power Electronics Specialists Conference, 2004
    Co-Authors: Hao Chen, E K K Sng, K J Tseng
    Abstract:

    In this paper, the generalized optimal Trajectory Control (GOTC) for the series-parallel resonant converter (SPRC) is presented. It allows the nonlinear resonant circuit of the SPRC having an arbitrary starting state to reach a desired steady state in the shortest possible time. Based on GOTC, a traditional feedback Controller with inner current and outer voltage state-feedback is designed for an SPRC based DC-DC converter. The GOTC based feedback Controller allows higher feedback loop gains to be used compared with simple frequency Control of the resonant circuit. This results in either better disturbance rejection for the converter or the possibility of reducing output filter sizing. Simulation results are used to verify the theoretical claims at this stage.