Hee-Jun Kim

A Study on Development of Independent Low Power IoT Sensor Module for Zero Energy Buildings

The Journal of Korea Institute of Information, Electronics, and Communication Technology, 2019

The energy consumed by buildings among the total national energy consumption is more than 10% of ... more The energy consumed by buildings among the total national energy consumption is more than 10% of the total. For this reason, Korea has adopted the zero energy building policy since 2025, and research on the energy saving technology of buildings has been demanded. Analysis of buildings' energy consumption patterns shows that lighting, heating and cooling energy account for more than 60% of total energy consumption, which is directly related to solar power acquisition and window opening and closing operation. In this paper, we have developed a low -power IoT sensor module for window system to transfer acquired information to building energy management system. This module transmits the external environment and window opening / closing status information to the building energy management system in real time, and constructs the network to actively take energy saving measures. The power used in the module is designed as an independent power source using solar power among the harvest energy. The topology of the power supply is a Buck converter, which is charged at 4V to the lithium ion battery through MPPT control, and the efficiency is about 85.87%. Communication is configured to be able to transmit in real time by applying WiFi. In order to reduce the power consumption of the module, we analyzed the hardware and software aspects and implemented a low power IoT sensor module.

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A single stage flyback power supply unit for LED lighting applications

International Conference on Electrical and Electronics Engineering, Dec 18, 2009

This paper presents a 75W single-stage power supply unit for LED lighting. The proposed power sup... more This paper presents a 75W single-stage power supply unit for LED lighting. The proposed power supply designed using flyback converter topology that is controlled by the critical conduction mode control. The secondary side of main transformer is directly connected to LED strings. By a constant current feedback circuit, this flyback converter directly regulates LED current. Although the proposed circuit doesn't need input current-sensing and input voltage feed-forward, it can achieve high power factor for wide input range. A prototype experimental set-up has been built and tested. Through this experiment with a prototype set-up, the validity of the proposed circuit is verified.

format_quoteConstant current feedback regulation is utilized to maintain LED output, addressing overload and thermal effects effectively.format_quote

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Capacitance deviation-to-time interval converter using current-tunable Schmitt triggers

IEICE Electronics Express, 2011

A capacitance deviation-to-time interval converter is presented for interfacing capacitive sensor... more A capacitance deviation-to-time interval converter is presented for interfacing capacitive sensors. It consists of two ramp integrators, two current-tunable Schmitt triggers, and two logic gates. A prototype circuit built using discrete components exhibits a resolution as high as 13 bits and a linearity error less than ±0.2% when the output pulse width is counted by a 20 MHz clock signal. Its application to a humidity sensor is also presented.

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Control of multi stand alone solar power systems using digital controller

Proceedings of the KIEE Conference, 2009

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A Study on Development of Independent Low Power IoT Sensor Module for Zero Energy Buildings

The energy consumed by buildings among the total national energy consumption is more than 10% of ... more The energy consumed by buildings among the total national energy consumption is more than 10% of the total. For this reason, Korea has adopted the zero energy building policy since 2025, and research on the energy saving technology of buildings has been demanded. Analysis of buildings' energy consumption patterns shows that lighting, heating and cooling energy account for more than 60% of total energy consumption, which is directly related to solar power acquisition and window opening and closing operation. In this paper, we have developed a low -power IoT sensor module for window system to transfer acquired information to building energy management system. This module transmits the external environment and window opening / closing status information to the building energy management system in real time, and constructs the network to actively take energy saving measures. The power used in the module is designed as an independent power source using solar power among the harvest energy. The topology of the power supply is a Buck converter, which is charged at 4V to the lithium ion battery through MPPT control, and the efficiency is about 85.87%. Communication is configured to be able to transmit in real time by applying WiFi. In order to reduce the power consumption of the module, we analyzed the hardware and software aspects and implemented a low power IoT sensor module.

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Improved Bridgeless Interleaved Boost PFC Rectifier with Optimized Magnetic Utilization and Reduced Sensing Noise

Journal of Power Electronics, Sep 20, 2014

An improved bridgeless interleaved boost power factor correction (PFC) rectifier to improve power... more An improved bridgeless interleaved boost power factor correction (PFC) rectifier to improve power efficiency and component utilization is proposed in this study. With combined conventional bridgeless PFC circuit and interleaved technology, the proposed rectifier consists of two interleaved and magnetic inter-coupling boost bridgeless converter cells. Each cell operates alternatively in the critical conduction mode, which can achieve the soft-switching characteristics of the switches and increase power capacity. Auxiliary blocking diodes are employed to eliminate undesired circulating loops and reduce current-sensing noise, which are among the serious drawbacks of a dual-boost PFC rectifier. Magnetic component utilization is improved by symmetrically coupling two inductors on a unique core, which can achieve independence from each other based on the auxiliary diodes. Through the interleaved approach, each switch can operate in the whole line cycle. A simple control scheme is employed in the circuit by using a conventional interleaved controller. The operation principle and theoretical analysis of the converter are presented. A 600 W experimental prototype is built to verify the theoretical analysis and feasibility of the proposed rectifier. System efficiency reaches 97.3% with low total harmonic distortion at full load.

A Study on OBC Integrated 1.5kW LDC Converter for Electric Vehicle

The Journal of Korea Institute of Information, Electronics, and Communication Technology, 2019

PHEV(Plug in Hybrid Electric Vehicle) and BEV(Battery Electric Vehicle) equip high voltage batter... more PHEV(Plug in Hybrid Electric Vehicle) and BEV(Battery Electric Vehicle) equip high voltage batteries to drive motor and vehicle electric system. Those vehicle require OBC(On-Board Charger) for charging batteries and LDC(Low DC/DC Converter) for converting from high voltage to low voltage. Since the charger and the converter actually separate each other in electrical vehicles, there is a margin to reduce the vehicle weight and area of installation by integration two systems. This paper studies a 1.5kW LDC converter that can be integrated into an OBC using an isolated current-fed converter by simplifying the design of LDC transformers. The proposed LDC can control the final output voltage of the LDC by using a fixed arbitrary output voltage of the bidirectional buck-boost converter, so that Compared to the existing OBC-LDC integrated system, it has the advantage of simplifying the transformer design considering the battery voltage range, converter duty ratio and OBC output turn ratio. Prototype of the proposed LDC was made to confirm normal operation at 200V ~ 400V input voltage and maximum efficiency of 91.885% was achieved at rated load condition. In addition, the OBC-LDC integrated system achieved a volume of about 6.51L and reduced the space by 15.6% compared to the existing independent system.

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Electronic ballast of the electrode-less lamp for the group lighting system

International Conference on Electrical and Electronics Engineering, Dec 18, 2009

This Paper presents RF modem based remote controlled electronic ballast for electrode-less lamps.... more This Paper presents RF modem based remote controlled electronic ballast for electrode-less lamps. In order to control the power of lamp driven by high-frequency electronic ballast, remote control is necessary. For the group lighting system, especially, wireless remote control using RF modem is proper. In this paper, 2.4-GHz ISM band RF modem based remote controlled electronic ballast is proposed. However, the cost of RF modem is relatively expensive as compare with the cost of electronic ballast. For the economic realization, one-ballast two-lamps system is proposed. And the proposed control circuit of the ballast is implemented with fully digital circuit using low cost 16-bit DSP and small size EPLD. Detailed algorithms for the power control and protections for the commercial electronic ballast are described. Finally, the wire and wireless linked group lighting system using the proposed ballast is introduced.

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Field stop shorted anode trench IGBT for induction heating appliances

IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society, 2012

This paper introduces a newly developed field stop shorted anode trench IGBT with intrinsic body ... more This paper introduces a newly developed field stop shorted anode trench IGBT with intrinsic body diode like power MOSFETs, and presents its effectiveness for the single ended resonant inverter in induction heating applications. Although the new device combines both IGBT and body diode functions it can provide better performances by means of an advanced fieid stop trench IGBT technology. The effectiveness of the new device is validated in an experiment using 1.8kW single-ended induction heating resonant inverter.

format_quoteThe saturation current of the new device is over twice that of the previous version, indicating significant enhancements in its operating capabilities.format_quote

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Papers by Hee-Jun Kim