• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.399-400
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• 2012

The proposed battery charger presented in this paper is suitable for Lead-Acid Battery and the dc/dc buck converter topology is applied as a charger circuit. The technique adopted in this charger is constant current & constant voltage dual mode, which is decided by the value of voltage of proposed battery. Automatic mode change function is detected by the percentage value of level of battery charging. CC Mode (Constant Current Mode) is operated when charging level is below 80% of the total charging of Battery voltage and above 80% of battery voltage charging, CV Mode (Constant Voltage Mode) is automatically operated. As the charging level exceeds 120%, it automatically terminates charging. The feedback signal to the PWM generator for charging the battery is controlled by using the current and voltage measurement circuits simultaneously. This technique will degrade the damage of proposed type of battery and improve the power efficiency of charger. Finally, a prototype charger circuit designed for a 12-V 7-Ah lead acid battery is constructed and tested to confirm the theoretical predictions. Satisfactory performance is obtained from simulation and the experimental results.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.143-149
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• 2016

The two-stage converter is widely used in traditional DC/AC inverter. It has several disadvantages such as complex topology, large volume and high loss. In order to overcome these shortcomings, a novel half load-cycle worked dual SEPIC single-stage inverter, which is based on the analysis of the relationship between input and output voltages of SEPIC converters operating in the discontinuous conduction mode (DCM), is presented in this paper. The traditional single-stage inverter has remarkable advantages in small and medium power applications, but it can’t realize boost DC/AC output directly. Besides one pre-boost DC/DC converter is needed between the DC source and the traditional single-stage inverter. A novel DC/AC inverter without pre-boost DC/DC converter, which is comprised of two SEPIC converters, is studied. The output of dual SEPIC converters is connected with anti-parallel and half load-cycle control is used to realize boost and buck DC/AC output directly and work properly, whatever the DC input voltage is higher or lower than the AC output voltage. The working principle, parameter selection and the control strategy of the inverters are analyzed in this paper. Simulation and experiment results verify the feasibility of the new inverter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.21-26
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• 2016

This paper presents a step-down DC-DC buck converter with a CCM/DCM dual-mode function for the internal power stage of portable electronic device. The proposed converter that is operated with a high frequency of 1 MHz consists of a power stage and a control block. The power stage has a power MOS transistor, inductor, capacitor, and feedback resistors for the control loop. The control part has a pulse width modulation (PWM) block, error amplifier, ramp generator, and oscillator. In this paper, an external capacitor for compensation has been replaced with a multiplier equivalent CMOS circuit for area reduction of integrated circuits. In addition, the circuit includes protection block, such as over voltage protection (OVP), under voltage lock out (UVLO), and thermal shutdown (TSD) block. The proposed circuit was designed and verified using a $0.18{\mu}m$ CMOS process parameter by Cadence Spectra circuit design program. The SPICE simulation results showed a peak efficiency of 94.8 %, a ripple voltage of 3.29 mV ripple, and a 1.8 V output voltage with supply voltages ranging from 2.7 to 3.3 V.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.226-239
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• 2018

In this paper, design and control method ZVT Interleaved Bidirectional LDC(IB-LDC) for mild-hybrid electric vehicle is proposed. The IB-LDC is composed of interleaved buck and boost converters employing an auxiliary inductor and auxiliary capacitors to achieve zero-voltage-transition. Operating principle of IB-LDC according to operation mode is introduced and mathematically analyzed in buck and boost mode. Moreover, PFM and phase control are proposed to reduce circulating current for low power range. Passive components design such as main inductor, auxiliary inductor and capacitors is suggested, considering ZVT condition and maximizing efficiency. Furthermore, a 600W prototype of ZVT IB-LDC for MHEVs is built and tested to verify validity.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.1
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• pp.82-91
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• 2017

This paper is a study on the bi-directional DC-DC converter, one of the key elements of 48V-12V dual systems in mild hybrid electric vehicles. Mild hybrid electric vehicles require a bi-directional DC-DC converter that can efficiently transmit power in two directions between a 48V battery and a 12V battery. To develop a bi-directional DC-DC converter with better price competitiveness, upgraded fuel economy, excellent performance and smaller size, this study designed, produced and presented a circuit that improved on the existing one. In the proposed 8-phase bi-directional DC-DC converter, the size of the passive element was reduced through the 8-phase interleaved topology, whereas downscaling had previously posed a difficulty. This study also designed and produced a 2.5kW class prototype. Based on the proposed 8-phase interleaved topology, a size of 227.5 (W) * 172 (L) * 64.35 (H) was achieved. In the boost mode operation and buck operation modes, the maximum efficiency was recorded at 94.04 % and 95.78 %, respectively.