• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.118-120
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• 2002

Voltage drop of low voltage distribution line is closely related with proper voltage regulation. It depends on the voltage drop of pole transformer, low voltage distribution line, and low voltage customer entrance line. Using above voltage drop factors, we proposes an estimation method of voltage drop in low voltage distribution line. Proposed method has been applied to a 22.9kV practical distribution system.

• ETRI Journal
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• 제32권4호
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• pp.520-529
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• 2010

In this paper, we present a low-voltage low-dropout voltage regulator (LDO) for a system-on-chip (SoC) application which, exploiting the multiplication of the Miller effect through the use of a current amplifier, is frequency compensated up to 1-nF capacitive load. The topology and the strategy adopted to design the LDO and the related compensation frequency network are described in detail. The LDO works with a supply voltage as low as 1.2 V and provides a maximum load current of 50 mA with a drop-out voltage of 200 mV: the total integrated compensation capacitance is about 40 pF. Measurement results as well as comparison with other SoC LDOs demonstrate the advantage of the proposed topology.

• 전력전자학회논문지
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• 제25권3호
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• pp.157-161
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• 2020

High voltage gain converters are essential for distributed power generation systems with renewable energy sources, such as fuel cells and solar cells, because of their low voltage characteristics. This paper introduces a novel nonisolated DC-DC converter topology developed by combining an inverting buck-boost converter and voltage multipliers. In the proposed converter, the input voltage is connected in series with the output, and the majority of the input power is directly delivered to the load. The voltage multipliers are stacked in series to achieve high step-up voltage gain. The voltage stress across all of the switches and capacitors can be significantly reduced. As a result, the switches with low voltage ratings can be used to achieve high efficiency and low cost. To verify the validity of the proposed topology, a 360-W prototype converter is built to obtain the experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.505-507
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• 2008

A conventional active-clamp forward (ACF) converter is a favorable candidate in low-to-medium power applications. However, the switches suffer from high voltage stress, i.e., sum of the input voltage and the reset capacitor voltage. Therefore, it is not suitable for high input voltage applications such as a front-end converter of which the input voltage is about 400-$V_{dc}$. To solve this problem, three-switch ACF (TS-ACF) converter, which employs two main switches and one auxiliary switch with low voltage stress, is proposed. Utilizing low-voltage rated switches, the proposed converter is promising for high input voltage applications with high efficiency and low cost.

• ETRI Journal
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• 제37권5호
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• pp.961-971
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• 2015

This paper proposes a 250 mV supply voltage digital low-dropout (LDO) regulator. The proposed LDO regulator reduces the supply voltage to 250 mV by implementing with all digital circuits in a$0.11{\mu}m$ CMOS process. The fast current tracking scheme achieves the fast settling time of the output voltage by eliminating the ringing problem. The over-voltage and under-voltage detection circuits decrease the overshoot and undershoot voltages by changing the switch array current rapidly. The switch bias circuit reduces the size of the current switch array to 1/3, which applies a forward body bias voltage at low supply voltage. The fabricated LDO regulator worked at 0.25 V to 1.2 V supply voltage. It achieved 250 mV supply voltage and 220 mV output voltage with 99.5% current efficiency and 8 mV ripple voltage at $20{\mu}A$ to $200{\mu}A$ load current.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.228-230
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• 2008

The response time characteristic of low voltage liquid crystals (LCs) is investigated and a new simulator for low voltage LCs is proposed. In order to enable low voltage operation, it is important to minimize Vth of LCs and variation of pixel voltage caused by dynamic capacitance operation of LC Display. Because dynamic capacitance variation is much larger for low voltage LC operation compared to that of conventional LC material, it is necessary to make a better model for dynamic capacitance operation. A proposed minimizing Vth of LCs and variation of pixel voltage study results through a new constant charge model improve response characteristics for low voltage LCs operation.

• 한국전기전자재료학회논문지
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• 제29권11호
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• pp.676-680
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• 2016

This paper describes a low voltage detection circuit used in the semiconductor chips. The circuit was composed of a detection part of the CMOS structure as three stages and two inverters. The output of the low voltage detection circuit become to 'high' from 'low', when the power supply voltage falls below 80%. When the power supply voltage is 5 V, it was detected at 4 V point. The proposed low voltage detection circuit can be easily applied only by changing the resister and the capacitor without structural change in a wide range of power supply voltage.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.83-85
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• 2019

The use of high voltage gain converters is essential for the distributed power generation systems with renewable energy sources such as the fuel cells and solar cells due to their low voltage characteristics. In this paper, a high voltage gain topology combining cascode Inverting Buck-Boost converter and voltage multiplier structure is introduced. In proposed converter, the input voltage is connected in series at the output, the portion of input power is directly delivered to the load which results in continuous input current. In addition, the voltage multiplier stage stacked in proper manner is not only enhance high step-up voltage gain ratio but also significantly reduce the voltage stress across all semiconductor devices and capacitors. As a result, the high current-low voltage switches can be employed for higher efficiency and lower cost. In order to show the feasibility of the proposed topology, the operation principle is presented and the steady-state characteristic is analyzed in detail. A 380W-40/380V prototype converter was built to validate the effectiveness of proposed converter.

• Journal of Power Electronics
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• 제15권3호
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• pp.806-818
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• 2015

Based on the inherent relationship between dc-bus voltage and grid feeding active power, two dc-bus voltage regulators with different references are adopted for a grid-connected PV inverter operating in both normal grid voltage mode and low grid voltage mode. In the proposed scheme, an additional dc-bus voltage regulator paralleled with maximum power point tracking controller is used to guarantee the reliability of the low voltage ride-through (LVRT) of the inverter. Unlike conventional LVRT strategies, the proposed strategy does not require detecting grid voltage sag fault in terms of realizing LVRT. Moreover, the developed method does not have switching operations. The proposed technique can also enhance the stability of a power system in case of varying environmental conditions during a low grid voltage period. The operation principle of the presented LVRT control strategy is presented in detail, together with the design guidelines for the key parameters. Finally, a 3 kW prototype is built to validate the feasibility of the proposed LVRT strategy.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1471-1483
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• 2017

The low-frequency characteristics of four-switch three-phase (FSTP) inverter are investigated in this paper. Firstly, a general space vector pulse width modulation (SVPWM) directly involved the neutral point voltage of DC-link is proposed, where no sector identifications and trigonometric function calculations are needed. Subsequently, to suppress the DC offset in the neutral point voltage, the relationship between the neutral point voltage and the ${\beta}-axis$ component of the load current is derived, and then a new neutral point voltage control scheme is proposed where no low pass filter is adopted. Finally, the relationship between the load power factor and the maximum linear modulation index of the FSTP inverter is revealed. Since the operational region for the FSTP inverter in low frequency is reduced by the enlarged amplitude of the neutral point voltage, a linear modulation range enlargement scheme is proposed. A permanent magnet synchronous motor with preset rotary speed serves as the low-frequency load of the FSTP inverter. Experimental results verify that the new neutral point voltage control scheme is effective in the deviation suppression of the neutral point voltage, and the proposed scheme is able to provide a larger linear operational region in low frequency.