• IEIE Transactions on Smart Processing and Computing
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• v.4 no.3
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• pp.141-144
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• 2015

A broadband radio frequency synthesizer for multi-band, multi-standard mobile DTV tuners is proposed, it's loop bandwidth can be calibrated to optimize integrated phase noise performance without the problem of phase noise peaking. For this purpose, we proposed a new third-order scalable loop filter and a scalable charge pump circuit to minimize the variation in phase margin during calibration. The prototype phase-lock loop is fabricated in 180nm complementary metal-oxide semiconductor shows that it effectively prevents phase noise peaking from growing while the loop bandwidth increases by up to three times.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.968-970
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• 2001

Recently, the power supply equipments have tendency to take multiple feedback loop paths. In this paper the state space averaging technique is applied for the analysis of flyback type current mode control circuit. We made real converter for the gurantee of stable output characteristic and proper design of feedback circuit. The validity of proposed method is verified from test results. The improvement of stability is confirmed by sinusoidal signal injection method with isolated transformer. It is known that phase margin is sufficient and gain crossover frequency $f_c$ is nearly 1/5 of switching frequency $f_s$, from the experimental result with frequency response analyzer.

• Proceedings of the IEEK Conference
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• 2003.11b
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• pp.7-10
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• 2003

In this paper, we present a new echo kernel, which is a modification of polar echo kernel. to improve the detection performance and robustness against attacks. Polar echo kernel may take advantage of large detection margin from the polarity of inserted echo signal, but its poor frequency response in low frequency band degrades sound quality. To solve this problem, we applied bipolar echo pulses to the polar echo kernel. Using the proposed echo kernel the distributions of autocepstrum peaks fur data ‘0’ and ‘1’ are located more distant and improvement of detection performance is achieved. It also makes the low frequency band flat so that the timbre difference in the polar echo kernel can be removed to reproduce the imperceptible sound qualify. Informal listening tests as well as robustness test against attacks were performed to evaluate the proposed echo kernel. Experimental results demonstrated the superiority of the proposed echo kernel to both conventional unipolar and polar echo kernels

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.239-241
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• 2001

Recently the power supply equipments have tendency to take multiple feedback loop paths. In this paper, the state space averaging technique is applied for the analysis of flyback type current mode control circuit. We made real converter for the gurantee of stable output characteristic and proper design of feedback circuit. The validity of proposed method is verified from test results. The improvement of stability is confirmed by sinusoidal signal injection method with isolated transformer. It is known that phase margin is sufficient and gain crossover frequency $f_c$, is nearly 1/5 of switching frequency $f_s$, from the experimental result with frequency response analyzer.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.365-367
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• 2000

Recently, the power supply equipments have tendency to take multiple feedback loop paths. In this paper, the state space averaging technique is applied for the analysis of flyback type current mode control circuit. We made real converter for the gurantee of stable output characteristic and proper design of feedback circuit. The validity of proposed method is verified from test results. The improvement of stability is confirmed by sinusoidal signal injection method with isolated transformer. It is known that phase margin is sufficient and gain crossover frequency $f_c$ is nearly 1/5 of switching frequency $f_s$ from the experimental result with frequency response analyzer.

• ETRI Journal
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• v.45 no.4
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• pp.690-703
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• 2023

Multistage amplifiers have become appropriate choices for high-speed electronics and data conversion. Because of the large number of high-impedance nodes, frequency compensation has become the biggest challenge in the design of multistage amplifiers. The new compensation technique in this study uses two differential stages to organize feedforward and feedback paths. Five Miller loops and a 500-pF load capacitor are driven by just two tiny compensating capacitors, each with a capacitance of less than 10 pF. The symbolic transfer function is calculated to estimate the circuit dynamics and HSPICE and TSMC 0.18 ㎛. CMOS technology is used to simulate the proposed five-stage amplifier. A straightforward iterative approach is also used to optimize the circuit parameters given a known cost function. According to simulation and mathematical results, the proposed structure has a DC gain of 190 dB, a gain bandwidth product of 15 MHz, a phase margin of 89°, and a power dissipation of 590 ㎼.

• Journal of Power Electronics
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• v.16 no.3
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• pp.849-860
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• 2016

The high-switching-frequency operation of power converters can achieve high power density through size reduction of passive components, such as capacitors, inductors, and transformers. However, a small-output capacitor that has small capacitance and low effective series resistance changes the small-signal model of the converter power stage. Such a capacitor can make the converter unstable by increasing the crossover frequency in the transfer function of the small-signal model. In this paper, the design and implementation of a high-frequency LLC resonant converter are presented to verify the power density enhancement achieved by decreasing the size of passive components. The effect of small output capacitance is analyzed for stability by using a proper small-signal model of the LLC resonant converter. Finally, proper design methods of a feedback compensator are proposed to obtain a sufficient phase margin in the Bode plot of the loop gain of the converter for stable operation at 500 kHz switching frequency. A theoretical approach using MATLAB, a simulation approach using PSIM, and experimental results are presented to show the validity of the proposed analysis and design methods with 100 and 500 kHz prototype converters.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.5
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• pp.338-344
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• 2000

This paper proposes a field-oriented control strategy without speed sensor in overall speed range. At low speed region including zero speed, the electrical saliency which is due to the main flux saturation is used in order to estimate an instantaneous flux position. This electrical saliency can be obtained from the difference of high frequency impedance by the high frequency signal injection. This method enables the stable operation at zero speed or stator frequency even under heavily loaded condition. However, because of the high frequency signal injection the loss and noise in motor increase and the voltage margin is reduced as the motor speed increases. Therefore, this algorithm must be supplemented with the algorithm based on the electrical model of motor, which is conventionally used in the region except the low speed. This paper proposes the combination algorithm between the high frequency signal infection method and the adaptive observer, in which the rotor flux and motor speed can be simultaneously estimated by the adaptive control theory. This combination algorithm enables the stable operation of field-oriented speed control without speed sensor in overall speed range. This is verified by experimental results.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.242-246
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• 2001

The alternated forward multi resonant converter (AT forward MRC) is studied on the transient response and the measured loop gain for stability. The compensator is composed of the error amplifier with 3 poles and 2 zeros. This is optimized through the experiment with HP4194A network analyzer. We are initiated by the thinking of how to make the stabilization from the experimental results of loop gain curves. The loop gain, low frequency gain and gain margin are more improved through the experimental considerations. Also, the transient response is more enhanced effectively.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.7
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• pp.32-39
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• 1998

This paper presents the experimental results on the 3-electrode DC-PDP which has a common electrode to improve the PDP life cycle. The measured DC characteristic proves the effectiveness of common electrode absorbing about half of discharge currents. The waveforms for pulse memory operation of3-electrode PDP without crosstalk could also be determined from the I-V characteristics. The pulse memory drives of 8*8 cell array show the frequency response fo memory margin and the luminance efficiency of 3-electrode PDP are quite different from genrally known characteristics of 2-electrode DC-PDP.