• Journal of Power Electronics
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• v.10 no.6
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• pp.673-679
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• 2010

Input-series-output-parallel (ISOP) connected DC-DC converters enable low voltage rating switches to be used in high voltage input applications. In this paper, a DSP is adopted to generate digital phase-shifted PWM signals and to fulfill the closed-loop control function for ISOP connected two full-bridge DC-DC converters. Moreover, a stable output current sharing control strategy is proposed for the system, with which equal sharing of the input voltage and the load current can be achieved without any input voltage control loops. Based on small signal analysis with the state space average method, a loop gain design with the proposed scheme is made. Compared with the conventional IVS scheme, the proposed strategy leads to simplification of the output voltage regulator design and better static and dynamic responses. The effectiveness of the proposed control strategy is verified by the simulation and experimental results of an ISOP system made up of two full-bridge DC-DC converters.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.288-290
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• 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.

• Journal of Power Electronics
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• v.13 no.1
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• pp.20-30
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• 2013

This paper presents a soft switching DC/DC converter for high voltage application. The interleaved pulse-width modulation (PWM) scheme is used to reduce the ripple current at the output capacitor and the size of output inductors. Two converter cells are connected in series at the high voltage side to reduce the voltage stresses of the active switches. Thus, the voltage stress of each switch is clamped at one half of the input voltage. On the other hand, the output sides of two converter cells are connected in parallel to achieve the load current sharing and reduce the current stress of output inductors. In each converter cell, a half-bridge converter with the asymmetrical PWM scheme is adopted to control power switches and to regulate the output voltage at a desired voltage level. Based on the resonant behavior by the output capacitance of power switches and the transformer leakage inductance, active switches can be turned on at zero voltage switching (ZVS) during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The current doubler rectifier is used at the secondary side to partially cancel ripple current. Therefore, the root-mean-square (rms) current at output capacitor is reduced. The proposed converter can be applied for high input voltage applications such as a three-phase 380V utility system. Finally, experiments based on a laboratory prototype with 960W (24V/40A) rated power are provided to demonstrate the performance of proposed converter.

• Journal of Power Electronics
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• v.12 no.1
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• pp.83-87
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• 2012

Input-series-output-parallel (ISOP) modular converters consisting of multiple modular DC/DC converters can enable low voltage rating switches for use in high voltage input applications. In this paper, an input voltage sharing control strategy for input-series-output-parallel (ISOP) full-bridge (FB) DC/DC converters is proposed. By sensing the difference in the input current of two modules, the system can achieve input voltage sharing for DC-DC modules. The effectiveness of the proposed control strategy is verified by simulation and experimental results obtained with a 200w-50kHz prototype.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1178-1180
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• 2003

The continuing need for more compact and reliable switching power supplies have aroused a renewed interest in a well founded control technique the Magnetic Amplifier(Magamp). Magamp have some advantages of higher power density, simple control circuit, good regulation, high frequency and high performance. The control method with magamp become attractive solutions for high current post regulated output applications. In this study, it is proposed that the magamp technique in flyback converters with multiple output windings. Operation principle of the proposed approach is described and design guidelines are provided. Experimental verifications on 50W multiple output flyback converter are conducted. Simulations and experimental results show that the proposed approach is high efficiency and voltage regulation of the auxiliary output is excellent.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.141-146
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• 2009

In this paper, a novel harmonic control circuit has been proposed for the design of high-efficiency power amplifier with Si LDMOSFET. The proposed harmonic control circuit haying the short impedances for the second- and third-harmonic components has been used to design the in/output matching network. The efficiency enhancement effect of the proposed harmonic control circuit is superior to the class-F or inverse class-F harmonic control circuit. Also, when the proposed harmonic control circuit has been adapted to the input matching network as well as the output matching network, the of ficiency enhancement effect of the proposed power amplifier has increased all the more. The measured maximum power added efficiency (PAE) of the proposed power amplifier is 82.68% at 1.71GHz band. Compared with class-F and inverse class-F amplifiers, the measured maximum PAE of the proposed power amplifier has increased in $5.08{\sim}9.91%$.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.67-70
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• 1996

This paper presents SVC which use PAM method and eliminate harmonics. Inverter is connected directly so that SVC improve output voltage waveform into 24 steps. Inverter output waveform THD is reduced to 6.89%. Leading control of reactive power generated in power system is possible. Snubber is added to reduce switching loss.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.455-459
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• 1998

In this paper input Series-Output Parallel connected converter configuration for high voltage power conversion applications is proposed and a control method to solve the problems of Input Series-Output Paralles connected converter configuration is introduced. In this configuration snubber circuit or voltage balancing controller that is necessary for the series connection of switching devices is not needed. The effectiveness of this proposed configuration is verified by simulation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.4
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• pp.289-295
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• 2008

In this paper, we designed the off-line PWM(Pulse width modulation) control IC for flyback type power converter to reduce the standby power consumption. In normal state, this off-line PWM IC generates the output pulse with $40\sim60kHz$ frequency and duty ratio of $20\sim88%$. When SMPS operates in standby mode, this IC generates the output pulse with 33kHz frequency and duty ratio of 1 %. SPICE simulation was performed to verify the standby power consumption of the power converter with designed of-line PWM IC. Power converter with designed off-line PWM IC consumes less than 0.3W when it operates in standby mode condition.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.345-348
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• 2000

In this paper, A Feedforward Linear Power Amplifier for IMT-2000 which IMD characteristics was improved was designed and fabricated. To improve the main power amplifier IMD characteristics, the Feedback loop was added to basic Feedforward Power Amplifier structure. Therefore, the output power of error amplifier can be reduced, and it is easy to control the linearization circuit to cancel total IMD. The designed power amplifier represented the 40㏈m(l0W) output power and -55㏈C 3rd IMD at Center frequency 2.14㎓ (@5㎒).