• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.2
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• pp.160-166
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• 2015

This study proposes an improved cell balancing circuit for fast equalization among lithium-ion (Li-ion) batteries. A simple voltage sensorless charge balancing circuit has been proposed in the past. This cell balancing circuit automatically transfers energy from high-to low-voltage battery cells. However, the circuit requires a switch with low on-resistance because the balancing speed is limited by the on-resistance of the switch. Balancing speed decreases as the voltage difference among the battery cells decrease. In this study, the balancing speed of the cell balancing circuit is enhanced by using the auxiliary circuit, which boosts the balancing current. The charging current is determined by the nominal battery cell voltage and thus, the balancing speed is almost constant despite the very small voltage differences among the batteries. Simulation results are provided to verify the validity of the proposed cell balancing circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.4
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• pp.279-285
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• 2019

This study proposes an enhanced switching pattern that can improve energy transfer efficiency in an active cell-balancing circuit using a multiwinding transformer. This balancing circuit performs cell balancing by transferring energy stored in a specific cell with high energy to another cell containing low energy through a multiwinding transformer. The circuit operates in flyback and buck-boost modes in accordance with the energy transfer path. In the conventional flyback mode, the leakage inductance of the transformer and the stray inductance component of winding can transfer energy to an undesired path during the balancing operation. This case results in cell imbalance during the cell-balancing process, which reduces the energy transfer efficiency. An enhanced switching pattern that can effectively perform cell balancing by minimizing the amount of energy transferred to the nontarget cells due to the leakage inductance components in the flyback mode is proposed. Energy transfer efficiency and balancing speed can be significantly improved using the proposed switching pattern compared with that using the conventional switching pattern. The performance improvements are verified by experiments using a 1 W prototype cell-balancing circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.5
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• pp.389-394
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• 2015

This paper proposes a series-connected power conversion system that integrates a photovoltaic power conditioner and a charge-balancing circuit. In conventional methods, a photovoltaic power conditioner and a cell-balancing circuit are needed for photovoltaic systems with energy storage devices, which results in a complex configuration and high cost. To overcome these problems, a series-connected DC-DC power conditioning system that integrates a photovoltaic power conditioner with a charge-balancing circuit is proposed. During the generation, the system operates as power conditioner only, whereas it operates as a cell balancing circuit during the rest time. For the analysis, the operating principle of the circuit and the controller design are done by PSIM simulation. For verification, a hardware prototype with 48-W photovoltaic modules has been implemented. Results verified that the modularized photovoltaic power conversion system with a series-connected storage successfully works with the proposed method.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1812-1820
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• 2017

This paper analyzes a symmetric active cell balancer for a battery management system. The considered cell balancer uses a forward converter in which the circuit structure is symmetric. This cell-balancing method uses fewer switches and is simpler than the previously proposed active cell-balancing circuits. Active power switches of this cell-balancing circuit operate simultaneously with the same pulse width modulation signals. Therefore, this cell-balancing circuit requires less time to be balanced than a previous bidirectional-forward-converter-based cell balancer. This paper analyzes the operational principles and modes of this cell balancer with computer-based circuit simulation results as well as experimental results in which each unbalanced cell is equalized with this cell balancer. The maximum power transfer efficiency of the investigated cell balancer was 87.5% from the experimental results. In addition to the experimental and analytical results, this paper presents the performance of this symmetric active cell-balancing method.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1992.04b
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• pp.159-168
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• 1992

생산라인의 line balancing이 흐름생산에 있어서 일관된 생산을 하기 위한 필수조건이다. 여러 다양한 제품을 생산하는 printed circuit board(PCB) 공장에서의 line balancing을 얻기 위해서는 mixed model line balancing절차를 설명하고자 한다.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.7-8
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• 2015

In this paper a cell-to-cell fast charge balancing circuit for the Lithium-Ion battery module is proposed. In the proposed topology the energy in a high voltage cell is transferred directly to a low voltage cell through the operation of the dc-dc converter. Furthermore, the charge balancing can be performed regardless of the battery operation whether it is being charged, discharged or relaxed. The monitoring circuit composed of a DSP and a battery monitoring IC is designed to monitor the cell voltage and detect the inferior cell thereby protecting the battery module from failure. In order to demonstrate the performance of the proposed topology, a prototype circuit was designed and applied to 12 Lithium-Ion battery module. It has been verified with the experiments that the charge equalization time of the proposed method was shorter compared with those of other methods.

• Journal of Sensor Science and Technology
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• v.21 no.5
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• pp.379-384
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• 2012

This paper presents the power source of wireless sensor node (WSN) using supercapacitors and a solar cell. Supercapacitors have high lifetime cycling compared to that of batteries. Supercapacitors are connected in series to achieve higher voltage and a voltage balancing circuit is required to ensure that no individual cell goes overvoltage. We employ an active balancing circuit that draws minimal current by using transistors. A diode is connected in series with each supercapacitor. A new balancing circuit that equalize the cells-voltage reduces energy consumption of supercapacitors. Voltage of operating WSN is applied 2.2-3.3V by DC/DC converter and supercapacitor voltage 2.2-5.1V. Maximum operating time of wireless sensor node is about 16 hours in full charging.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.6
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• pp.732-741
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• 2018

In order to maximize the usable capacity of a BMS (battery management system) that uses several battery cells connected in series, a cell balancing technique that equips each cell with the same voltage is needed. In the active cell balancing circuit using a multi-winding transformer, a balancing circuit that transfers energy directly to the cell (cell-to-cell) is composed of a PMOS switch and a gate driving chip for driving the NMOS switch. The TLP2748 photocoupler and the TLP2745 photocoupler are required, resulting in increased cost and reduced integration. In this paper, instead of driving PMOS and NMOS switching devices by using photocoupler, we proposed 70V BCD process based PMOS gate driving circuit, NMOS gate driving circuit, PMOS gate driving circuit and NMOS gate driving circuit with improved switching time. ${\Delta}t$ of the PMOS gate drive switch with improved switching time was 8.9 ns and ${\Delta}t$ of the NMOS gate drive switch was 9.9 ns.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.4
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• pp.247-255
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• 2018

This paper proposes a transformer design of a direct cell-to-cell active cell balancing circuit with a multi-winding transformer for battery management system (BMS) applications. The coupling coefficient of the multi-winding transformer and the output capacitance of MOSFETs significantly affect the balancing current transfer efficiency of the cell balancing operation. During the operation, the multi-winding transformer stores the energy charged in a specific source cell and subsequently transfers this energy to the target cell. However, the leakage inductance of the multi-winding transformer and the output capacitance of the MOSFET induce an abnormal energy transfer to the non-target cells, thereby degrading the transfer efficiency of the balancing current in each cell balancing operation. The impacts of the balancing current transfer efficiency deterioration are analyzed and a transformer design methodology that considers the coupling coefficient is proposed to enhance the transfer efficiency of the balancing current. The efficiency improvements resulting from the selection of an appropriate coupling coefficient are verified by conducting a simulation and experiment with a 1 W prototype cell balancing circuit.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1881-1884
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• 2003

In some requirements of dc motor drive circuit applications are high quality output with generation of low internal conducted EMI. However the conventional dc motor drive circuits have been usually using unbalanced circuit which generates the high conducted EMI to the frame ground. This paper presents a balanced dc motor drive circuit which is effective way to reduce the common-mode noise. The circuit balancing is to make the noise pick up or occurring in both conductor lines, signal path and return path is equal in amplitude and opposite phase so that it will cancel out in the frame ground. The common-mode conducted noise reduction of this proposed dc motor drive is confirmed by experimental results.