• 대한임베디드공학회논문지
• /
• 제18권1호
• /
• pp.9-17
• /
• 2023

This paper relates to the development of a device for measuring the efficiency of a solar panel based on a variable constant current, and proposed a standard for reuse of the solar panel. By applying a variable constant current circuit to a solar panel efficiency measuring device, it was easy to apply a maximum power point tracking (MPPT) algorithm. In addition, a load dispersion method was applied to measure the efficiency of a high-capacity solar panel. and it is possible to solve a problematic thermal runaway during a MOSFET parallel operation by applying the load dispersion method. As a result of the experiment, the solar panel efficiency measuring device was able to accommodate a large solar panel of 350W, which is the maximum measurement goal. In this paper, the validity was confirmed through the 310W solar panel efficiency measurement experiment collected after removal.

• 전자공학회논문지
• /
• 제52권3호
• /
• pp.59-66
• /
• 2015

본 논문에서는 4bit SAR-ADC(Successive Approximation ADC) 기반의 LDO(Low Drop-Out Regulator)와 파워 트랜지스터의 사이즈 선택을 통하여 DC-DC 벅 컨버터의 효율을 개선하는 방법을 제안한다. 제안하는 회로는 부하 전류에 따라서 파워 트랜지스터 사이즈를 선택하여 DC-DC 벅 컨버터의 효율을 개선한다. 이를 위해, 우리는 스위칭 손실과 전도 손실이 교차하는 지점을 파워 트랜지스터의 적절한 사이즈로 선택하였다. 또한, standby mode 또는 sleep mode로 동작 시에는 효율을 개선하기 위해 LDO로 동작하도록 하였다. 제안하는 회로는 4bit로 파워 트랜지스터 사이즈(X1, X2, X4, X8)를 선택하였고, 저부하에서 단일 사이즈를 이용한 기존의 방식보다 최대 25%의 효율 개선을 얻을 수 있었다. 입력 전압은 5V, 출력 전압은 3.3V, 최대 부하 전류는 500mA이다.

• Journal of Power Electronics
• /
• 제16권6호
• /
• pp.2024-2034
• /
• 2016

This paper presents a DC-DC buck converter with a Phase-Locked Loop (PLL) that can compensates for power efficiency degradation over a wide input range. Its switching frequency is kept at 2 MHz and the delay difference between the High side driver and the Low side driver can be minimized with respect to Process, Voltage and Temperature (PVT) variations by adopting the PLL. The operation mode of the proposed DC-DC buck converter is automatically changed to Pulse Width Modulation (PWM) or PWM frequency modes according to the load condition (heavy load or light load) while supporting a maximum load current of up to 1.2 A. The PWM frequency mode is used to extend the CCM region under the light load condition for the PWM operation. As a result, high efficiency can be achieved under the light load condition by the PWM frequency mode and the delay compensation with the PLL. The proposed DC-DC buck converter is fabricated with a $0.18{\mu}m$ BCD process, and the die area is $3.96mm^2$. It is implemented to have over a 90 % efficiency at an output voltage of 5 V when the input range is between 8 V and 20 V. As a result, the variation in the power efficiency is less than 1 % and the maximum efficiency of the proposed DC-DC buck converter with the PLL is 95.4 %.

• Journal of Mechanical Science and Technology
• /
• 제20권9호
• /
• pp.1502-1513
• /
• 2006

This study analyzes the design and part load performance of a power generation system combining a micro gas turbine (MGT) and an organic Rankine cycle (ORC). Design performances of cycles adopting several different organic fluids are analyzed and compared with performance of the steam based cycle. All of the organic fluids recover greater MGT exhaust heat than the steam cycle (much lower stack temperature), but their bottoming cycle efficiencies are lower. R123 provides higher combined cycle efficiency than steam does. The efficiencies of the combined cycle with organic fluids are maximized when the turbine exhaust heat of the MGT is fully recovered at the MGT recuperator, whereas the efficiency of the combined cycle with steam shows an almost reverse trend. Since organic fluids have much higher density than steam, they allow more compact systems. The efficiency of the combined cycle, based on a MGT with 30 percent efficiency, can reach almost 40 percent. hlso, the part load operation of the combined system is analyzed. Two representative power control methods are considered and their performances are compared. The variable speed control of the MGT exhibits far better combined cycle part load efficiency than the fuel only control despite slightly lower bottoming cycle performance.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2006년도 전력전자학술대회 논문집
• /
• pp.131-133
• /
• 2006

A high efficiency half bridge converter for PDP in whole operation load range is proposed in this paper. The ZVS(Zero Voltage Switching) in whole load range and high efficiency in low load range is achieved because the proposed converter is switched by fixed frequency asymmetrical duty ratio and resonant operation.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
• /
• pp.288-290
• /
• 2006

An efficiency improving method for Uninterruptible Power Supply System(UPS) was developed by using OP-AMP based application circuits such as voltage detection device, current detection device and static switch control device. The efficiency improving algorithm was made by mixing the operating concepts of On-Line type UPS with the operating concepts of Off-Line type UPS. The UPS' inverter does not work if the UPS' output load current is not higher than the low load operating current which is about 0-30(%) of the UPS' output load capacity. The low load operating current is adjustable within the half of the UPS' output load capacity. If the UPS' output load current is rising over than the low load operating current, the UPS' inverter starts working and the inverter output power feeds to the loads of UPS. If UPS' input power breaks out while UPS' inverter does not operate because the load current is low, the inverter starts working within 4(ms) with excessive output voltage which is ${\pm}$8(%) of normal UPS' output voltage. Like these. UPS can continuously feeds power to it's load device and reduce power consumptions.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2012년도 전력전자학술대회 논문집
• /
• pp.29-30
• /
• 2012

In this paper, a performance of bi-directional DC/DC converter using PFM control at whole load range is analyzed. A bi-directional DC/DC converter using PFM control in this paper can be soft switching operation with LC series resonant circuit. It's difficult to expect a high efficiency at whole load range in general resonant converter because of limitation of soft switching area. Therefore converter used in this paper has a variable frequency PFM control to overcome a limitation of soft switching area and it makes a high efficiency at whole load range by implementing a soft switching at light load area of restricted soft switching. The high efficiency at whole load range is verified by simulation and experimental result.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1998년도 하계종합학술대회논문집
• /
• pp.189-192
• /
• 1998

In this paper, we analyzed Microwave-DC conversion efficiency for the rectennas and it's position change. Rectenna consist of a two major parts, receiveing antenna and rectifying circuits. We made two types of 2.45C rectennas which the dipole and the patch antenna. Rectifying circuit is a GaAs-schottky diode with a large forward current and reverse breakdown voltage. The results of RF-DC conversion efficiency for two rectennas, patch type has 75.6% efficiency with 400$\Omega$ load resistor and dipole type has 69.75% efficiency with 360$\Omega$ load resistor. When the rectennas has optimal load resistor, Rectenna efficiency shows of $\pm10%$ at $70^{\circ}$~$110^{\circ}$ position.

• 전기학회논문지P
• /
• 제62권4호
• /
• pp.175-180
• /
• 2013

This paper presents the design and implementation of a Bicycle Locker System. Generally DC motor has been used to control a Bicycle Locker System, but DC motor system requires frequent maintenances and its power efficiency is comparatively poor especially under heavy load conditions. In order to improve this difficulties, this paper adopts BLDC motor for a Bicycle Locker System and its motor controller is developed. The performances of locker units are compared between DC motor unit and BLDC motor unit. The motor power consumptions between two motors are discussed. Test results verify that power efficiency of the suggested BLDC drive unit is considerably improved compared to the DC drive unit with load condition.

• 환경위생공학
• /
• 제5권1호
• /
• pp.83-92
• /
• 1990

Adapting two step aeration system to a waste water treatment of W-paper manufactory as Full-Scale Plants, we drew a following conclusion from its practical working. 1. Because BOD removal efficiency was 20% in A-Stage, 90% in B-Stage and total removal efficiency was 97%. It worked treatment plant well and was suitable for effluent water standard as well. Because COD removal efficiency was 42% in A-stage, 71% in B-stage and the total removal efficiency was 94% COD control was possible in effluent water quality. 2. Treatment efficiency according to a load capacity was average 20% in 1.401 BOD kg/m3/d load of A-Stage and average 90% in 0.273 BOD kg/$\textrm {m}^3$ / d load of B-Stage. 3. Treatment efficiency according to a ratio of F/M was 2.657--5.024 kg BOD/kg MLSS/d in A-Stage and BOD removal efficiency was 16-261 in the same stage. The ratio of F/M was 0.068-0.094 kg BOD /kg MLSS/d and BOD removal efficiency ratio was 85-94%. Therefore treatment efficiency could be kept stably and volume of aeration tank could be reduced wholly. 4. Treatment efficiency according to MLSS appeared BOD 20%. COD 42%, in A-Stage and removal efficiency appeared BOD 90%, COD 71% in B-Stage. They were suitable for plan condition. 5. Because of working of complemented treatment plant by AB-Process. 20,000,000 Won a month was saved than the ordinary working cost. Therefore, it was assumed that invested cost could be recollected in 19 months or so consequently.