• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.363-366
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• 2007

A new current control technique called Amplitude Shift Modulation (ASM) for cold cathode fluorescent lamps (CCFL) has been developed. This new technique sets and continuously controls the current of each individual CCFL in an LCD backlight lamp array.

• Journal of Power Electronics
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• v.8 no.4
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• pp.332-344
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• 2008

High frequency AC (HFAC) power distribution systems delivering power through a high frequency AC link with sinusoidal voltage have the advantages of simple structure and high efficiency. In a multiple module system, where multiple resonant inverters are paralleled to the high frequency AC bus through connection inductors, it is necessary for the output voltage phase angles of the inverters be controlled so that the circulating current among the inverters be minimized. However, the phase angle of the resonant inverters output voltage can not be controlled with conventional phase shift modulation or pulse width modulation. The phase angle is a function of both the phase of the gating signals and the impedance of the resonant tank. In this paper, we proposed a pulse phase modulation (PPM) concept for the resonant inverters, so that the phase angle of the output voltage can be regulated. The PPM can be used to minimize the circulating current between the resonant inverters. The mechanisms of the phase angle control and the PPM were explained. The small signal model of a PPM controlled half-bridge resonant inverter was analyzed. The concept was verified in a half bridge resonant inverter with a series-parallel resonant tank. An HFAC power distribution system with two resonant inverters connected in parallel to a 500kHz, 28V AC bus was presented to demonstrate the applicability of the concept in a high frequency power distribution system.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2129-2138
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• 2016

The full-bridge inverter, widely used for single-phase photovoltaic grid-connected applications, presents a leakage current issue. Therefore, an AC bypass branch is introduced to overcome this challenge. Nevertheless, existing modulation strategies entail drawbacks that should be addressed. One is the zero-crossing distortion (ZCD) of the AC current caused by neglecting the AC filter inductor voltage. Another is that the system cannot deliver reactive power because the AC bypass branch switches at the power frequency. To address these problems, this work proposes an optimized hybrid modulation strategy. To reduce ZCD, the phase angle of the inverter output voltage reference is shifted, thereby compensating for the neglected leading angle. To generate the reactive power, the interval of the negative power output is calculated using the power factor. In addition, the freewheeling switch is kept on when power is flowing into the grid and commutates at a high frequency when power is fed back to the DC side. In this manner, the dead-time insertion in the high-frequency switching area is minimized. Finally, the performances of the proposed modulation strategy and traditional strategies are compared on a universal prototype inverter. Experimental results validate the theoretical analysis.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.400-402
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• 1994

This paper presents a digital implementation of delta modulation Technique for Active Power Filters. Delta modulated scheme is to control the harmonic-compensating current indirectly by adjusting the capacitor voltage to be sinusoidal. The overall control system has two feedback loops. One is the outer propotional feedback for loop regulating the dc current of active filters and the other is the inner feedback loop for maintaining the ac current waveform to be sinusoidal, and have zero power factor angle(i.e. unity power factor). The characteristics of the proposed is investigated by digital simulation using ACSL and experimental results are obtained by TMS370C756 Single-Chip Microprocessor relative to analog delta modulation technique.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1021-1026
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• 1990

Accuracy improvement of a self-mixing semiconductor laser range finder is predicted by simulation, in which the laser modulation current is reshaped to give an ideal triangular waveform of the optical frequency change. The maximum range measurement error of less than 0.1% in a wide range of O.1m to 1m is expected by the reshaping of the modulation current. Experimental verification of the effect of current reshaping on the linearization of the derivative of the optical frequency change curve is given.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.9
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• pp.1239-1246
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• 1995

A forced commutated cycloconverter (FCC) is a direct ac-ac converter capable of providing simultaneous voltage and frequency transformations. In this paper, vector control of an induction motor controlling stator current with forced commutated cycloconverter is presented. The advantage of current control is that the stator dynamics are eliminated and high performance vector control can be achieved. A novel modulation method based on dq transformation techniques is presented. Proposed modulation strategy generates the low frequency modulation function by the instantaneous value of the desired output voltages not by the steady state values of output magnitude and output frequency. PI control and predictive control algorithm for current control are applied, and the validity of proposed method is confirmed through digital simulations. Simulation results of step response and torque distubance and current control are presented.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.8
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• pp.440-447
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• 1999

This paper proposes a control method for three-phase PWM rectifier with only single current sensor in DC link side. A PWM modulation strategy for reconstructing three phase currents from the DC link current is given. The states of the retifier switch are modified so that all phase currents can be reconstructed in a switching period although one or two of active vectors is applied only for a short time. Therefore, a new current control using an adjustment scheme of the modulation signal for three-phase PWM rectifier will be discussed, and verified the experimental results.

• Journal of Power Electronics
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• v.16 no.1
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• pp.153-162
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• 2016

Given their structural arrangement, photovoltaic (PV) modules exhibit parasitic capacitance, which creates a path for high-frequency current during zero-state switching of the converter in transformerless systems. This current has to be limited to ensure safety and electromagnetic compatibility. Many solutions that can minimize or completely avoid this phenomenon, are available. However, most of these solutions are patented because they rely on specific and often complex converter topologies. This study aims to solve this problem by introducing a solution based on a classic converter topology with an appropriate modulation technique and passive filtering. A 5.5 kW single-phase residential PV system that consists of DC-DC boost stage and DC-AC H-bridge converter is considered. Control schemes for both converter stages are presented. An overview of existing modulation techniques for H-bridge converter is provided, and a modification of hybrid modulation is proposed. A system prototype is built for the experimental verification. As shown in the study, with simple filtering and proper selection of switching states, achieving low leakage current level is possible while maintaining high converter efficiency and required energy quality.

• The Journal of Korean Medicine
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• v.24 no.4
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• pp.34-42
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• 2003

This study was designed to investigate the modulation of the Corydalis tuber on glycine-activated ion current in rat periaqueductal gray (PAG) neurons. Aqueous extract from Corydalis tuber has been widely used for pain control such as dysmenorrhea, irregular menstruation or amenorrhea with abdominal cramping, neuralgia, headache and gastrointestinal spasm. The PAG region of the brain is known to be involved heavily with nociception. Modulation of the Corydalis tuber on glycine-induced ion current in rat periaqueductal gray (PAG) neurons was studied by a nystatin-perforated patch-clamp technique. High concentrations of Corydalis tuber elicited ion current, which was suppressed by strychnine application. Low concentrations of Corydalis tuber reduced glycine-induced ion currents in the PAG neurons. Inhibitory action of Corydalis tuber on glycine-activated ion current was reduced by treatment with naltrexone, a non- selective opioid antagonist. Application of N-methylmalemide (NEM), a sulfhydryl alkylating agent, also reduced the inhibitory action of Corydalis tuber on glycine-activated ion current in the PAG neurons. These results suggest that the inhibitory effect of Corydalis tuber on glycine-activated ion current in the PAG neurons is one of the analgesic mechanisms of the Corydalis tuber, which may activate descending pain control system in PAG neurons.

• Journal of the Korean Society of Radiology
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• v.9 no.5
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• pp.279-285
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• 2015

The eye of human is a radiation sensitive organ and this organ should be shielded from radiation exposure during brain CT procedures. In the brain CT procedures, bismuth protector using to reduce the radiation exposure dose for eye. But protecting the bismuth always accompanies problem of the image quality reduction including artifact. This study aim is the eye radiation exposure dose and image quality evaluation of the new tube current modulation such as new organ based-tube current modulation, longitudinal-TCM, angular-TCM between shielding scan technique using bismuth and lead glasses. As a result, radiation dose of eye is reduced 25.88% in new OB TCM technique then reference scan technique and SNR new OB TCM is 6.05 higher than bismuth shielding scan technique and lower than reference scan technique. In clinical brain CT, new OB TCM technique will contribute to reduction of radiation dose for eye without decrease of image quality.