• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.277-284
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• 2017

For passive power factor correction, the valley fill circuit approach is attractive for low power applications because of low cost, high efficiency, and simple circuit design. However, to vouch for the product quality, two dc-link capacitors in the valley fill circuit should be selected to withstand the peak rectified ac input voltage. The common mode (CM) and differential mode (DM) choke should be used to suppress the electromagnetic interference (EMI) noise, thereby resulting in large size volume product. This paper presents the practical design and implementation of a valley fill flyback converter with reduced dc link capacitors and EMI magnetic volumes. By using the proposed over voltage protection circuit, dc-link capacitors in the valley fill circuit can be selected to withstand half the peak rectified ac input voltage, and the proposed CM/DM choke can be successfully adopted. The proposed circuit effectiveness is shown by simulation and experimentally verified by a 78W prototype.

• Journal of Industrial Technology
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• v.31 no.A
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• pp.103-107
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• 2011

In this paper, a method is proposed to improve power factor and the input current THD in LED driver circuit. The researched circuit consists of a valley-fill circuit and boosting inductor and a Buck converter. Valley-fill circuit is a passive PFC and simplified structure, the buck converter is operated with current feedback. The switching frequency is 50KHz in LED driver circuit and LED forward current is constant. A valley-fill type PFC circuit for LED driver(15Watt) has been implemented, and the validity of proposed method is shown by is simulation and experimental result.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2935-2938
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• 2003

A new Valley-fill circuit for improving PF(power factor) is proposed in this paper. The proposed topology combines Valley-fill rectifier and an additional inductor for boosting. In the proposed circuit, a shapc of input current is related to the PWM duty cycle. The boosting inductor makes improve PF by the electric charge transfer action. The operation principle and the shape of input current arc analyzed as applied the boosting inductor. The optimum value of boosting inductor is determined. A 100W single-stage converter has been designed and tested. Experimental results are presented to verify the validity of the proposed converter.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.109-114
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• 2012

In this paper, We studied LED(Light Emitted Diode) sensor lights system using PIR(Pyroelectric Infrared Ray) sensor, CdS and MCU(Micro Controller Unit). And applied the valley fill circuit to improve the power factor. We designed the amplifier for each sensor and the LED driver for constant current which is the buck converter. Also, we proposed the algorithm of LED control by each sensors using MCU. Experimental results showed that power factor is 92% with valley fill circuit.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1361-1363
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• 2005

THD's effects on electronic ballast for fluorescent lamp and ways to improve. To design AC/DC converter in order to enhance current THD. valley-fill circuit and charge pump circuit which has improved valley-fill circuit.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2798-2800
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• 1999

A new circuit, modified valley fill (MVF) combined with resonant inductor of the self-excited resonant inverter and charge pump capacitors(CPCs), is presented to achieve high PF electronic ballast providing sufficient preheat current to lamp filaments for soft start maintaining low DC bus voltage. The MVF can adjust the valley voltage higher than half the peak line voltage. The CPCs draw the current from the input line to make up the current waveform during the valley interval. The measured PF and THD are 0.99 and 12%, respectively. The lamp current CF is also acceptable in the proposed circuit. The proposed circuit is suitable for implementing cost-effective electronic ballast.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.297-302
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• 2014

In this paper, a LED driver compatible with TRIAC-dimmer applying active bleeder is proposed. If TRIAC-dimmer is connected with LED driver, flicker phenomenon occurs by TRIAC malfunction. In order to prevent this problem, a current over holding current must flow into TRIAC. Therefore, additional circuit compatible with TRIAC-dimmer is required to provide enough current. Passive bleeder has power loss in whole operation period. The proposed circuit apply a valley-fill circuit for power-factor-correction and a novel active bleeder detecting malfunction point of TRIAC. Therefore, it prevent malfunction of TRIAC-dimmer and have advantage of higher efficiency than passive bleeder. To verify the validity of proposed circuit, 13W-lighting LED driver prototype has been proposed.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.3
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• pp.485-490
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• 2012

In this paper, driver circuit of LED lights for ships is designed and implemented to replace conventional lights with filament which have short life time due to vibration of ships. The driver of LED module is switching circuit without transformer to reduce volume and cost. As switch circuit controls input 220 VAC with PWM, LED module is reliably driven. Power factor is improved by using valley-fill PFC compensation circuit which is handled to pulse current of switching circuit. Serial-parallel LED circuit is applied to reduce change period of lights of long-term navigation ships. Array of serial-parallel can operate even if some of LEDs is damaged. It is suitable for ships that power consumption and power factor of lights including developed drive circuit have 39Watt and 0.925 respectively.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.311-314
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• 2002

In recent years, various power factor correction(PFC) circuits for the electronic ballasts have been proposed. In this paper, we have studied several passive PFC and compared with their characteristics, used in the electronic ballast for fluorescent. Especially, Improved Valley Fill Circuit (IVF) and the circuit IVF PFC combined with Charge Pumping Capacitors(CPCs) have been reaserched for High Power Factor. In conclusion, we have researched characteristics of Passive PFC and proposed the most effective PFC method.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2795-2797
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• 1999

Several power factor correction(PFC) circuits are presented to achieve high PF electronic ballast for both voltage-fed and current-fed electronic ballast. The proposed PFC circuits use valley-fill(VF) type DC-link stages modified from the conventional VF circuit to adopt the charge pumping method for PFC operations during the valley intervals. In voltage-fed ballast, charge pump capacitors are connected with the resonant capacitors. In current-fed type, the charge pump capacitors are connected with the additional secondary-side of the power transformer. The measured PF and THD are higher than 0.99 and 15% for all proposed PFC circuits. The lamp current CF is also acceptable in the proposed circuits. The proposed circuit is suitable for implementing cost-effective electronic ballast.