• Journal of Power Electronics
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• 제17권3호
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• pp.632-640
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• 2017

Input series output independent (ISOI) dc-dc converter systems are suitable for high voltage input and multiple output applications with low voltage rating switches. This paper proposes a novel control strategy consisting of one output voltage regulating (OVR) control loop and n-1 (n is the number of modules in the ISOI system) input voltage sharing (IVS) control loops. An ISOI system with the proposed control strategy can be applied to applications where the output loads of each module are the same. Under these conditions, IVS can be achieved and output voltages copying can be realized in an ISOI system. In this control strategy there is only one controller for each module and the design process of the control loops is simple. Since no central controller is needed in the system, modularity of the system is improved. The operation principle of the new control strategy is introduced and the control effect is simulated. Then the output power and voltage characteristics of an ISOI system under this new control strategy are analyzed. The stability of the proposed control strategy is explored base on a Hurwitz criterion, and the design guide line of the control strategy is given. A two module ISOI system prototype is fabricated and tested in the laboratory. Experimental results verify the effectiveness of the proposed control strategy.

• 한국멀티미디어학회논문지
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• 제25권8호
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• pp.1022-1037
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• 2022

It is important to develop a transducer that generates uniform output power through frequency control of the HIFU at 4 MHz frequency for the high intensity focused ultrasound (HIFU) skin diseases treatment. In this paper, a 4 MHz frequency band HIFU system for skin disease treatment was designed, manufactured and developed. In HIFU, even for the ultrasonic vibrator in the 4 MHz frequency band, the characteristics of the output power of the HIFU are different depending on the difference in the thickness of the PZT material. Through the development of a system amplifier, the sound output of the HIFU transducer was improved to more than 48 W and uniform output power control was possible. And, it is possible to control the output power even in a frequency band of 4.0 to 4.7 MHz, which is wider than 4.0 MHz, and shows the resonance frequency of the transducer. The maximum output power for each frequency was 49.969 W and the minimum value was 48.018 W. The maximum output power compared to the minimum output power is 49.969 W, which is uniform within 4.1%. It was confirmed that the output power of the HIFU through the amplifier can be uniformly controlled in the 4 MHz frequency band.

• 한국광학회지
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• 제10권1호
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• pp.53-57
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• 1999

국재에서 성장 가공시킨 Nd:YAG 결정을 사용한 발진기를 설계제작하였다. 이로부터 발진동작, Q-스위칭, 출력광속의 위상파면 등을 조사하였으며, 다음으로 단일 경로 이득을 측정하였다. 츨력경의 반사율의 변화에 따르는 문턱 입력에너지를 결정하고 이로부터 단일 경로 이득을 계산하였다. 한편 레이저와 발진기 증폭기를 사용하는 보편적인 방법에 의하여 단일 경로 이득을 측정하여 비교 검증하였다. Q-스위칭 레이칭 레이저 최대출력은 1.5MW이고, 펄스폭은 30ns이었으며, 문턱 에너지에서 이득은 0.0958 cm-1 이었다. 실험과정에서 똑같은 사양의 외국산 Nd:YAG 결정에 의한 비교실험을 동시에 수행하였으며, 이로부터 국산 레이저 Nd3+:YAG결정의 레이저 발진 특성이 우수함을 확신할 수 있었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.47-51
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• 2001

In this paper, we have explained electrical characteristics of a step-down Rosen type piezoelectric transformer for AC-adapter. When the electric voltage is applied to the driving piezoelectric vibrator polarized in the longitudinal direction, then output voltage is generated at the generating piezoelectric vibrator polarized in the thickness direction due to the piezoelectric effects. From the piezoelectric direct and converse effects, symbolic expressions between the electric inputs and outputs of the step-down piezoelectric transformer have derived with an equivalent circuit model. With the symbolic expressions, load and frequency characteristics have discussed through simulation. Output voltage and current from a 11-layered and a 13-layered piezoelectric transformers were measured under the various conditions of loads and frequencies. First we measured resonant frequency from impedance curve and got equivalent impedance value of the piezoelectric transformer from admittance plot. It was shown from experiments that output voltage has increased and resonant frequency has changed according to various resistor loads. Output current has decreased inversely proportional to changing of loads. Moreover, the measured values of output voltage and current are well agreed with the simulated values of the proposed equivalent circuit model.

• 기술혁신연구
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• 제15권1호
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• pp.203-233
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• 2007

This study investigates how characteristics in the value-chain industrial cluster affect the R&D investment and the output of firms in each industries. For this, we try to extract the inter-industrial networking structure from the input-output table in which 17 manufacturing sectors are included. In particular, we will give shape to the "unit structure" which shows the intermediary flows of goods and services between industries in order to get an unit of final demand in a certain industry. Using this "unit structure", we can try the inter-industrial networking analysis and get some indices of centrality and centralization related to the characteristics of each industries in the value-chain industrial cluster. The results show that the centrality in the value-chain industrial cluster does not have any consequence for the R&D investment and the output in each industries. However, there is a correlation between the centralization in the value-chain industrial cluster and the R&D investment and the output of firms in each industries. These results may be very suggestive in bringing up a new frame of industrial cluster policy in a macro level.

• 조명전기설비학회논문지
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• 제25권10호
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• pp.47-58
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• 2011

This paper proposes the optimal current detect(OCD) maximum power point tracking(MPPT) control of photovoltaic(PV) system for robust with environment changing. The output characteristics of the solar cell is a nonlinear and affected by a temperature, the solar radiation and temperature. Conventional MPPT control methods are tracked the maximum power point by constant incremental value. So these methods are slow the response speed and generated the vibration in steady state and cannot track the MPP in environment condition changing. And power loss is generated because of the self-excitation vibration in MPP region. To solve this problem, this paper proposes the novel control algorithm. Proposed algorithm is detected the optimal current in two control region using the output power and current curve. Detected current is used the converter switching for tracking the MPP. Proposed algorithm is compared output power error to conventional algorithm with radiation and temperature changing. In addition, the validity of the algorithm is proved through the output error response characteristics.

• 한국광학회지
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• 제11권4호
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• pp.289-293
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• 2000

다이오드 레이저 뒷면 여기 방식을 이용하여 발진 파장이 $2.02\mu\textrm{m}$인 중적외선 Tm:YAG 레이저를 제작하고, 출력 특성을 조사하였다. 레이저의 출력은 Tm:YAG 결정의 온도에 민감하게 변화하였으며, 레이저의 출력경이 곡면경인 경우에 평면적인 격우보다 더 큰 출력을 얻을 수 있었다. 곡면경을 사용하고 Tm:YAG 결정을 지지하는 구리 지지대의 온도를 $6^{\circ}C$로 낮추었을 때, 최고 1.2W의 출력을 얻을 수 있었다. 이 때, 문턱 여기 출력은 약 1.6W이었고, 기울기 효율(slope efficiency) 및 광학 효율(optical to optical efficiency)은 각각 29%와 20%이었다.

• 전력전자학회논문지
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• 제23권3호
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• pp.208-216
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• 2018

In this paper, an LLC resonant converter employing two coupled inductors on the secondary side of the converter is proposed. The conventional LLC converter exhibits serious power loss during secondary winding of the transformer because of generation of tremendous output current ripples. To overcome this problem, an LLC resonant converter with a current doubler as a rectifying circuit was recently proposed. However, the current-doubler rectifying circuit requires coupled inductors with a high coupling ratio to retain the designed resonance characteristics. Therefore, an additional hardware filter is required at the output stage to address large output current ripples. Additional design procedures are also necessary because the inductance component of the added filter affects the designed resonant network. To solve this issue, an LLC resonant converter employing two coupled inductors is proposed in this paper. Mathematical analysis shows that the proposed secondary-side current-doubler circuit does not affect the designed resonance characteristics. The operating principles and theoretical analyses are proven through a simulation and experiments with a 54 V/28 A prototype.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.999-1002
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• 1997

In this study, in order to set ELID conditions in the internal grinding wheel, the characteristics with the variations of grit size, output voltage and peak current were examined by using conventional machining center(M/C) equipped with electrolytic in-process dressing(EL1D). The initial working voltage was lowered and the working current was high with increasing grit size. The insulating layer thickness increased, as the final voltage increased with the output voltage and peak current. The initial wear rate of the wheel machined with ELID were measured indirectly by using surface roughness tracer. The initial wear rate of the wheel with ELID increased along with high grit size. In case that the grit size with ELID was low, the output voltage and peak current had to be increased to increase the insulating layer thickness. In case of the high grit size, the output voltage and the peak current were established low, which made the insulating layer thickness decreased.

• 전자공학회논문지D
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• 제35D권2호
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• pp.33-39
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• 1998

A six-beam accelerometer with self-compensated off-axis sensitivity was fabricated onthe selectively diffused (111)-oriented n/n$^{+}$/n silicon substrates by a unique porous silicon micromachining technique, which has self-stip characteristics and highly seletive formation of porous silicon layer during anodic reaction. Also, the characteristics of the fabricated accelerometer were investigated. The sensitivity of the acceleormeter added up outputs of three bridges through a summing circuit was 0.68 mV/g and the nonlinearity was less than 2% of the full scale output. The measured first resonant frequency was 4.236 kHz. When the outputs of three bridges were compared to summing output of bridges obtained through summing circuit, the normal output for Z-axis acceleration exhibited the same value s summing outputs of three bridges without reduction of sensitivity and thus the sensitivity decrease due to additional beam was compensated. Although a maximum off-axis sensitivity in one bridge of the accelerometer showed 17% of normal sensitivity, the off axis sensitivity obtained from summing output of three bridges decreased to 1.0%. Therefore, the self-elimination of off-axis sensitivity can be simply realized by obtaining the output of the sensor through summing circuit.t.