Jung-Kyu Han

With the growing complexity of satellite missions, research on electric propulsion (EP) systems is becoming more important due to their high energy efficiency and longer operational lifespans. In addition, as satellite bus voltages rise from 50 to 300–400 V to support high-power EP systems, the development of high-power and high-efficiency power systems has become essential. Among the various power processing units in EP systems, heater power converters play a crucial role in regulating temperature for propellant vaporization and plasma ignition processes. The half-bridge type topologies are generally considered to handle the high input bus voltage of the heater power system. However, the half-bridge LLC converter has drawbacks related to performance degradation under large temperature fluctuations and reduced efficiency under wide input voltage variations in space environments, and the asymmetrical half-bridge (AHB) converter suffers from insufficient zero-voltage switching (ZVS) energy under light load conditions, resulting in low efficiency. Therefore, this article proposes a frequency control scheme for the AHB converter to enhance efficiency under light load conditions in EP heater power applications. By decreasing the switching frequency under light load conditions, the proposed control scheme secures sufficient ZVS energy, resulting in high efficiency without requiring additional components or redesign of magnetic components. A prototype with the proposed control scheme is implemented to validate its effectiveness and feasibility under 250–400 V input and 12 V/20 A output specifications.

As the complexity of satellite missions grows, their overall power demands continue to increase. Consequently, efficiently managing Li-ion batteries through a battery management system has become crucial. In particular, achieving a high cell balancing speed is critical because low-Earth-orbit satellites must complete both battery charging and cell balancing within a limited Sun period. However, as the number of battery cells increases, conventional balancing methods exhibit various limitations, such as the requirement of a large number of components and low balancing speed between distant cells. Therefore, this paper proposes a cell balancing circuit to achieve a high cell balancing speed with fewer components. The proposed circuit employs a chain structure by adopting a coupled inductor into a conventional buck-boost Cuk (BBC) circuit. As a result, it has a small number of components with the inherent simple structure of the BBC circuit and enables fast balancing between distant cells. In addition, the proposed circuit achieves additional reduction of components with an integration of cell balancing modules. The practicality and effectiveness of the proposed circuit were demonstrated through experimental comparisons with an eight-cell Li-ion battery string.

A narrow plasma ion energy distribution (IED) is an important for improving the precision of plasma processes in semiconductor manufacturing. The tailored voltage waveform (TVW) based plasma processing has attracted significant attention as a monoenergetic IED can be achieved. Conventional TVW modulators need separate circuits to implement bias voltage and slope voltage, which results in a larger volume and the use of numerous switching components. In this article, a new high power-density TVW modulator is proposed, which reduces the volume and switching components by integrating the bias voltage modulator and the slope voltage modulator. The proposed modulator simplifies the circuit by integrating switches and offers an inherent inductor current bypass in case of fault situations, which removes the additional circuit. Furthermore, even when scaling up to a multimodal IED system using two or more negative bias voltages, inductor voltage swings due to bias voltage variations do not occur, resulting in a significant reduction in inductor volume. The feasibility of the proposed modulator was verified through a prototype targeting a total of 1.2 kV tailored voltage waveforms at 100 kHz, positive voltage bias of 400 V, negative voltage biases of -100 V/-500 V, and slope voltage of -300 V.

A totem-pole bridgeless boost converter is one of the most promising topologies for the power factor correction (PFC) stage in high-power applications due to its high efficiency and small number of components. However, due to the totem-pole structure of the field-effect transistor (FET), very high switching loss occurs via the reverse recovery current of the body diode. To solve these problems, critical mode (CRM) control is a good solution to achieve the valley switching technique. With valley switching of CRM control, the switching loss decreases drastically with decreasing turn-on voltage. But, although the CRM control enables valley switching, it is hard to make an exact valley switching control with general zero-voltage detection circuits. In addition, when a frequency limitation scheme is applied to prevent a very high frequency, the switch can operate with hard switching at the boundary of the frequency limitation. Furthermore, the CRM boost PFC has a low PF and high total harmonic distortion (THD) under light-load conditions due to the large negative current resulting from resonance between the inductor and parasitic capacitance. It becomes worse at near-zero input voltage since the resonance current becomes larger near zero-input voltage. Therefore, in this paper, a totem-pole bridgeless boost PFC converter with high efficiency, high PF, and low THD is developed using TMS320F28377 by Texas Instruments. Based on the basic digital structure of the totem-pole bridgeless converter, the proposed controls help with exact valley switching, PF and THD improvement, and frequency limitation. The prototype converter is verified using 90–264 VAC input voltages and 450 V/3.3 kW output specifications.

This study proposes a novel frequency modulation scheme for a continuous conduction mode (CCM) boost power factor correction (PFC) converter. The aim is to improve the total harmonic distortion (THD) under light-load conditions. Boost converters are widely utilized with CCM control for the PFC stage owing to their ability to achieve high efficiency with minimal components. In addition, they have a high power factor (PF) and low THD. However, despite being designed for CCM operation, the boost PFC converter transitions into discontinuous conduction mode (DCM) as the output load decreases. This mode, known as mixed conduction mode, degrades the PF and THD of the PFC converter. To address these issues, we propose a novel frequency modulation scheme. The CCM boost PFC converter adopts frequency variation to reduce the DCM region. To validate the feasibility of the proposed concept, a prototype with a 60 Hz/230 V_ac input and 850 W/380 V output was utilized. Consequently, the boost PFC converter attains a high PF and low THD with simplified circuits.

Server power supply has to maintain output power even under abnormal input voltage conditions for stable operation of the server. Input-voltage-based current reference control has been widely used for power factor correction converter in server power supply because it can instantly generate a current reference and maintain a stable output. However, because harmonics and noise in the input voltage directly influence the current reference, the input current total harmonic distortion (THD) increases. On the other hand, phase-locked loop (PLL) based control can achieve lower current THD due to its excellent noise and harmonic filtering capabilities, but it cannot respond to sudden changes in the input voltage. In this letter, a hybrid current reference control method is proposed to achieve stable operation of the server power supply. The proposed method ensures continuous operation under abnormal input voltages by utilizing input-voltage-based control. Therefore, in normal input condition, the PLL bandwidth design can be alleviated to achieve a lower current THD. To determine the effectiveness of the proposed control method, steady-state operation and abnormal input condition operation were confirmed through a 47–64 Hz/90–264 V _rms 3-kW prototype converter.

For the power systems in electric vehicle, a weight and efficiency are very important since it is directly related with driving range. Many previous researches proposed new systems to reduce a weight or to increase efficiency. However, although they improved the weight or efficiency, they usually degrade the other side. Therefore, this paper proposes a new power system which achieves high efficiency while don't degrade the weight of the power system by adopting frequency modulation control. The proposed idea is implemented for 48V-to-12V DC-DC converter of mild hybrid electric vehicle using buck converter.

With rapid developments in the satellite data services market, the demand for low Earth orbit (LEO) satellites is increasing. Advancements in designing lightweight satellites are essential to maximize profits from the mass production of LEO satellites in private companies. This paper proposes a new direct charging control suitable for electrical power systems for lightweight and highly reliable LEO satellites. Moreover, an analysis of the proposed solar array regulator (SAR) in terms of weight, efficiency, and reliability is presented. Additionally, the advantages of the proposed SAR in terms of lifespan and state of health (SOH) of Li-ion batteries are presented because the peak value of the battery charging current and the temperature changes during the battery charging operation are relatively small.

As satellite missions become increasingly diverse, the power capacity of satellites continues to increase. Accordingly, the weight and loss of the electrical power system of the satellite must be reduced. Thus, a high bus voltage is required for the electrical power system of the satellite. However, most high-power dc/dc converter topologies, such as half-bridge and full-bridge dc/dc converters have leg-structures, which violate the heritage design characteristics of the dc/dc converters for satellites. To solve these problems, a two-switch forward converter with an integrated buck converter is proposed in this article. By integrating the buck converter into the two-switch forward converter, one switch and one diode are eliminated in the proposed converter, and consequently, its cost, weight, and volume can be greatly reduced. Moreover, the zero-voltage switching of the low-side switch can be achieved. Therefore, the proposed converter achieves a high efficiency under the entire load condition compared with conventional converters. The effectiveness and feasibility of the proposed converter were verified with a prototype of 300–330 V input and 600 W (150 V/100 V) output.