@inproceedings{liang_guo_huang_2011, title={A high efficiency DC MIC for PV energy harvest in FREEDM systems}, DOI={10.1109/apec.2011.5744612}, abstractNote={The future renewable electric energy delivery and management (FREEDM) system provides a DC interface for alternative energy sources. As a result, photovoltaic (PV) energy can be easily delivered through a DC/DC converter to the FREEDM system's DC bus, without the requirement of an additional DC/AC inverter. For this PV converter, the module integrated converter (MIC) is a good candidate. In this paper, two types of DC MIC structures, parallel connected MICs and series connected MICs, have been compared; the parallel connected MICs have been shown to have more advantages. Then a high efficiency dual mode resonant converter topology is proposed for parallel connected DC MICs. The new resonant converter can change resonant modes adaptively depending on the panel voltage and generated power level. The operation principle of the proposed converter is explained and a DC gain analysis is performed based on the fundamental harmonic analysis (FHA) method. For performance evaluation, a 240W prototype has been built. Compared to LLC converter, the light load to medium load efficiency has been improved greatly and the maximum efficiency reaches 96.5% in the experiment.}, booktitle={Annual ieee conference on applied power electronics conference and}, author={Liang, Z. G. and Guo, R. and Huang, A. Q.}, year={2011}, pages={301–308} }
 @inproceedings{guo_liang_huang_2011, title={A high efficiency transformerless step-up DC-DC converter with high voltage gain for LED backlighting applications}, DOI={10.1109/apec.2011.5744767}, abstractNote={Single Boost converter has several limitations in driving a long LED string although it can have perfect current match between each LED. Extreme duty cycle and low efficiency are the two major drawbacks. In this paper, a high efficiency step-up DC-DC converter with high voltage gain for LED backlighting applications is proposed. Without using a transformer, a multi-modes charge-pump is cascaded with a Boost converter to achieve high gain. The charge-pump is unregulated and can switch between 1x, 2x, and 3x mode according to the output requirement. The LED current is regulated by controlling the duty cycle of the Boost converter. The charge pump is located at the low current side therefore can have very high efficiency. The Boost converter is located at the low voltage side and can operate at a relatively low duty cycle, thus the efficiency is improved. The proposed solution can achieve high voltage gain as well as high overall efficiency. The control will also be benefited by the two stage solution. Theoretical efficiency derivations are given in this paper. A prototype is built and the experiment shows a maximum 10.5% efficiency improvement when driving 11 LEDs from 2.7V input voltage.}, booktitle={Annual ieee conference on applied power electronics conference and}, author={Guo, R. and Liang, Z. G. and Huang, A. Q.}, year={2011}, pages={1350–1356} }
 @article{guo_yang_huang_endredy_2010, title={A High Efficiency Regulated Charge Pump over Wide Input and Load Range}, ISSN={["1048-2334"]}, DOI={10.1109/apec.2010.5433355}, abstractNote={A multi-modes regulated charge pump with improved efficiency over wide input and load range is proposed in this paper. The output voltage is regulated to 5V when input is 4.5–2.7V. By alternating the switch network, it can realize 2x, 1.5x, and 1.33x conversion modes, which improves the efficiency over wide input range. During each mode, the output voltage is regulated by a controlled current source. The regulated charge pump is designed for a very wide load range (10mA to 500mA). A hybrid control scheme is proposed and analyzed to achieve a high efficiency over desired load range. Both of the simulation and test results are provided to verify the control scheme. The results show that the total loss at light load can be reduced by 56% to 83%.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Guo, Rong and Yang, Liyu and Huang, Alex and Endredy, John}, year={2010}, pages={1172–1176} }
 @article{wang_zhou_park_guo_huang_2010, title={Analysis of Process-Dependent Maximal Switching Frequency, Choke Effect, and Its Relaxed Solution in High-Resolution DPWM}, volume={25}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2009.2025272}, abstractNote={This letter uses the fanout-of-4 (FO4) metric to analyze the semiconductor process (SP) dependent maximal switching frequency (MSF) of a digital pulsewidth modulator (DPWM). After discussing the choke effect in a self-oscillating hybrid (SOH) DPWM and its impact on MSF, this letter further shows that separating the voltage-controlled oscillator (VCO) and the delay mux line is an effective way to relax the choke effect so that the MSF in the SOH could be almost doubled, together with 10%-20% power saving. Taking a low-cost AMI06 SP and 9-bit-resolution specification as an example, this letter predicts that 8 MHz switching frequency could be achieved with the proposed SOH. The SOH chip was custom-designed and fabricated in a 0.703 mm2 die via the metal oxide semiconductor implementation service (MOSIS) educational program. The chip test demonstrated that the MSF is 7.4 MHz with 1.07 mA power consumption, and the adjustable switching frequency range is from 1.8 to 7.4 MHz.}, number={1}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Wang, Xiaopeng and Zhou, Xin and Park, Jinseok and Guo, Rong and Huang, Alex Q.}, year={2010}, month={Jan}, pages={152–157} }
 @article{guo_chen_qian_2007, title={Study of igniter in low-frequency square wave electronic ballasts for metal halide lamps}, volume={22}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2007.900450}, abstractNote={Metal halide lamps (MHLs) have serious acoustic resonance problem. The most widely used method to achieve acoustic-resonance free is to use low-frequency square wave (LFSW) electronic ballasts. There are two ignition methods commonly used in LFSW electronic ballast: high-frequency resonance ignition and additional pulse igniter. This paper analyzed the problems during ignition while using the conventional additional pulse igniter and proposed some solutions. A novel high-frequency resonance igniter is also proposed, where no extra semiconductors and feedback control circuit are needed to perform the ignition. High-voltage ignition pulses are obtained by utilizing the fast polarity inversion of the output voltage of full-bridge inverter. Theoretical analysis, simulation, and experiment results of a prototype for 70-W MHLs verified the effectiveness of both the proposed solutions and the igniter.}, number={4}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Guo, Rong and Chen, Min and Qian, Zhaoming}, year={2007}, month={Jul}, pages={1098–1106} }