• 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.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.206-209
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• 1999

There exists an acute need for high voltage solid-state-switches in a broad area of applications. With the proposed method using simple voltage balancing circuit with series connected IGBTs, it is realized high voltage semiconductor switches with working voltages of several order kilo-volts. The operation principle of the proposed circuit is explained and analyzed. Transient and static voltage-balancing is tested on a experimenta 3kV/45A switch with four series-connected IGBTs.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.701-710
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• 2017

This paper presents a five-level PWM inverter using series and parallel connection of voltage sources. The alternative connection is done by an auxiliary circuit consisted of a switch, three diodes, and two batteries. The auxiliary circuit is located between input dc voltage source and H-bridge cell. Thanks to the auxiliary circuit, the proposed inverter synthesizes five-level output voltage in an effective way. Topologically both batteries are charged and discharged in the same rate, so it does not need to apply battery voltage balancing control method. Theoretical analysis of the proposed inverter is verified by computer-aided simulation and experiment based on a prototype of 1kW.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.1
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• pp.39-45
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• 2000

최근에 전력용 반도체 스위치의 정격이 커지면서 IGBT와 같은 소자는 그 편리성과 대용량화로 점차 많은 응용분야에 이용되고 있다. 특히 보다 높은 전압 정격을 용구하는 중·대용량 분야, 소용량이면서 고압 정격을 요구하는 분야의 저가의 전력용 반도체 고압 스위치가 요구되는 분야 등에서 높은 정격을 가지는 IGBT스위치를 구현하기 위하여 그 소자들간의 직렬로 연결하는 것이 필수적이다. 본 논문에서는 수 kV의 동작전압을 가지는 스위치를 실현하기 위하여 기존의 직렬 연결된 IGBT에 제안된 보조회로를 삽입하였다. 본 논문에서는 IGBT를 이용한 고압스위칭 동작원리와 그 기능을 검증하기 위해 4개의 IGBT를 직렬연결한 3kV/45A급 스위치를 제작하여 과도상태 및 정상상태에서의 전압 분배를 실험하였다.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.26-27
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• 2011

This paper focuses on the zero-voltage/zero current transition voltage equalization circuit for the series connected battery cell. By adding auxiliary resonant cells at the main switching devices such as MOSFET or IGBT, zero current switching is achieved and turned off loss of switching elements is eliminated and by the voltage/second balancing of the inductor, zero voltage switching can be applied to switching element. Transformer coupling between battery cells and ZVZCT (Zero Voltage Zero Current Transition) switching method allow the fast balancing speed and high frequency operation, which reduces the size and weight of the circuit. The validity of the battery equalization is further verified using simulation involving four lithium-ion battery cell models.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1474-1480
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• 2017

This paper presents a new LED current balancing scheme using double-step-down dc-dc converter. With the proposed structure, the two channel LED currents are automatically balanced without using any dedicated control or auxiliary circuit. In addition, switching loss of the switching devices in the proposed LED driver is lower than that of the conventional buck LED driver. To verify the operation of the proposed LED driver, a hardware prototype is built and tested with different number of LED.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1187-1194
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• 2017

In this paper, a high step-up DC-DC PWM converter with continuous input current and low voltage stress is presented for renewable energy application. The proposed converter is composed of a boost converter integrated with an auxiliary step-up circuit. The auxiliary circuit uses an additional coupled inductor and a balancing capacitor with voltage doubler and switching capacitor technique to achieve high step-up voltage gain with an appropriate switch duty cycle. The switched capacitors are charged in parallel and discharged in series by the coupled inductor, stacking on the output capacitor. In the proposed converter, the voltage stress on the main switch is clamped, so a low voltage switch with low ON resistance can be used to reduce the conduction loss which results in the efficiency improvement. A detailed discussion on the operating principle and steady-state analyses are presented in the paper. To justify the theoretical analysis, experimental results of a 200W 40/400V prototype is presented. In addition, the conducted electromagnetic emissions are measured which shows a good EMC performance.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.337-338
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• 2014

본 논문에서는 배터리 셀 간의 빠른 전하 균일화를 위한 새로운 셀 밸런싱 회로를 제안한다. 대칭적인 다권선 변압기를 이용하는 밸런싱 회로의 경우 셀들 간의 밸런싱 전류의 크기가 회로 내부 저항 및 변압기의 누설 인덕턴스에 의해 크게 제약 받고, 배터리 셀 간의 밸런싱이 이루어짐에 따라 충방전 전류가 감소한다는 단점이 있다. 본 논문에서는 보조 회로를 이용하여 밸런싱 전류를 부스트 업 시켜 빠르게 셀 간의 전하 밸런싱을 맞추어주는 회로를 제안한다. 이를 통해 회로 내부 저항의 영향을 줄이고 일정한 충방전 전류를 흘려보냄으로 빠르게 셀 전하들의 밸런싱을 맞출 수 있다.