• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1155-1161
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• 2014

This paper proposes a start-up voltage generator for reducing the minimum input supply voltage of DC-DC boost converters to 250mV. The proposed start-up voltage generator boosts 250mV input voltage to over 500mV to charge the capacitor for starting the boost converter. After the boost converter operates initially with the supply voltage charged in the capacitor, it uses its boosted output voltage for the supply voltage. Therefore, after the start-up operation, the proposed DC-DC boost converter works as the same as the conventional one. The proposed start-up voltage generator reduces the threshold voltage of the transistors by adjusting the body voltage at a low input voltage. This causes the higher clock frequency and the larger current to a Dickson charge-pump for boosting the input voltage. The proposed start-up voltage generator was implemented with a $0.18{\mu}m$ CMOS process. Its clock frequency and output voltage were 34.5kHz and 522mV at 250mV input voltage, respectively.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.201-205
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• 1998

In this paper, the charge control with the input voltage feed forward is proposed for the input series-output parallel connected converter configuration for high voltage power conversion applications. This control scheme accomplishes the output current sharing for the output-parallel connected modules as well as the input voltage sharing for the input-series connected modules for all operating conditions including the transients. It also offers the robustness for the component value mismatches among the modules.

• Journal of Power Electronics
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• v.11 no.5
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• pp.655-661
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• 2011

This paper presents two topologies for single-stage single-phase double-buck type PFC converters, designed to operate at high power factor, near sinusoidal input currents and adjustable output voltage. Unlike the known buck type PFC topologies, in which the output voltage is always lower than the maximum input voltage, the proposed converters can operate at output voltages higher than the ac input peak voltage. A reduced number of switches on the main path of the current are another characteristic of the two proposed topologies. To shape the input line currents, a fast and robust controller based on a sliding mode approach is proposed. This active non-linear control strategy, applied to these converters allows high quality input currents. A Proportional Integral (PI) controller is adopted to regulate the output voltage of the converters. This external voltage controller modulates the amplitude of the sinusoidal input current references. The performances of the presented rectifiers are verified with experimental results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.6
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• pp.16-28
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• 2012

This paper proposes a quasi Z-source converter(QZSC) with a diode-capacitor output filter to improve the output DC voltage boost ability. The proposed converter has the same quasi Z-source network topology compared with the conventional converter. But the proposed method is adopted a diode-capacitor filter as its output filter, since the conventional method is used an inductor-capacitor as its output filter. Under the condition of the same input-output DC voltage, the proposed method has more lower shoot-through duty ratio than the conventional method. Also, because the proposed converter has same voltage boost factor under lower shoot-through duty ratio compared with the conventional converter, the proposed converter can be operated with the lower capacitor voltage of Z-source network and the lower input current. To confirm the validity of the proposed method, PSIM simulation and a DSP based experiment were performed to acquire the output DC voltage 120[V] under the input DC voltage 80[V]. And the capacitor voltage and inductor current in Z-source network, the output voltage of each converter were compared and discussed.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.472-476
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• 2012

In this paper, a sensorless control scheme for a three-phase bi-directional voltage-type PWM rectifier in wind power generation system that operates without the input AC voltage sensors (generator side) is described. The basic principles and classification of the PWM rectifier are analyzed, and then the three-phase mathematical model of the input AC voltage sensorless PWM rectifier control system is established. The proposed scheme has been developed in order to lower the cost of the three-phase PWM rectifier but still achieve excellent output voltage regulation, limited current harmonic content, and unity input power factor.

• Proceedings of the KIPE Conference
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• 2008.06a
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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.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.102-110
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• 2016

In this paper, a high-frequency dual mode control LLC resonant converter with wide input voltage range is proposed through zero voltage switching (ZVS) under the universal line input voltage and every load conditions. Conventional small power adapter driving should be satisfied with universal line input voltage because it has no power factor correction circuit regulation. The conventional LLC resonant converter for an adapter can reduce the size of transformer in terms of high-frequency driving and ZVS. However, this converter has a disadvantage in terms of design of resonant tank under various input voltages because the frequency modulation range is very wide to satisfy voltage conversion gain. Compared with the conventional one, the proposed LLC converter can be adapted to universal line input voltage and high-frequency driving because it is controlled by pulse width modulation and pulse frequency modulation with control voltage. The validity of the proposed LLC converter is proved through the 60 W prototype.

• Journal of Power Electronics
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• v.15 no.1
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• pp.10-17
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• 2015

A quasi-constant on-time controlled buck front end in combined discontinuous conduction mode and boundary conduction mode is proposed to improve power factor (PF).When instantaneous AC input voltage is lower than the output bus voltage per period, the buck converter turns into buck-boost converter with the addition of a level comparator to compare input voltage and output voltage. The gate drive voltage is provided by an additional oscillator during distortion time to eliminate the cross-over distortion of the input current. This high PF comes from the avoidance of the input current distortion, thereby enabling energy to be delivered constantly. This paper presents a series analysis of controlling techniques and efficiency, PF, and total harmonic distortion. A comparison in terms of efficiency and PF between the proposed converter and a previous work is performed. The specifications of the converter include the following: input AC voltage is from 90V to 264V, output DC voltage is 80V, and output power is 94W.This converter can achieve PF of 98.74% and efficiency of 97.21% in 220V AC input voltage process.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.3
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• pp.114-123
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• 1998

The multi-resonant converter(MRC) minimizes a parasitic oscillation by using the resonant tank circuit absorbed parasitic reactances existing in a converter circuit. So it si possible that the converter operated at a high frequency has a high efficiency because the losses are reduced. Such a MHz high frequency applications provide a high power density [W/inch3] of the converter. But the resonant voltage stress across a switch of the resonant tank circuit is 4~5 times a input voltage. This h호 voltage stress increases the conduction loss because of on-resistance of a MOSFET with higher rating. Thus, in this paper we proposed the alternated multi-resonant converter (AT MRC) differ from the clamp mode multi-resonant converter and applicated it to the forward MRC. The AT forward MRC can reduce the voltage stress to 2~3 times a input voltage by using two series input capacitor. The control circuit is simple because tow resonant switches are driven directly by the output pulse of the voltage controled oscillator. This circuit type is verified through the experimental converter with 48V input voltage, 5V/50W output voltage/power and PSpice simulation. the measured maximum voltage stress is 170V of 2.9 times the input voltage and the maximum efficiency of 81.66% is measured.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.4
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• pp.39-47
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• 2000

This paper presents the sinusoidal tracking controller in error to eliminate the steady state control error and to improve the transient characteristics for input current in voltage source PWM converter with input current estimation. The estimation method of input current values and configuration of controller are described. DC output voltage is controlled by PI controller, and sinusoidal tracking current controller which tracks directly AC input current is used as input current controller. The sinusoidal tracking current controller can be used without any coordinate transformation algorithms.It is proved that the steady state deviation of input current reduces to zero and the proposed control system is not affected by input voltage from transfer functions of input current control system. The validity of proposed scheme is verified by simulations and experimental results for load resister and input voltage variation.