• Journal of Power Electronics
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• v.18 no.6
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• pp.1708-1719
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• 2018

A complete current loop decoupling control strategy based on a sliding mode observer (SMO) is proposed to eliminate the influence of current dynamic coupling and back electromotive force (EMF) in the vector control of permanent magnet synchronous motors. With this strategy, current dynamic decoupling and back EMF compensation can be simultaneously achieved. Unlike conventional methods, the proposed strategy can avoid the disturbances caused by the parametric variations of motor systems and maintain the advantages of proportional integral (PI) controllers, which are robust and easy to operate. An improved SMO, which uses a special PI regulator other than a linear saturation function as the equivalent control law in the boundary layer of a sliding surface, is proposed to eliminate the estimated errors caused by the quasi-sliding mode and obtain a satisfactory decoupling performance. The stability and parameter robustness of the proposed strategy are also analyzed. Physical experimental results are presented to verify the validity of the method.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.2
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• pp.85-91
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• 2022

This study proposes a high efficiency bridgeless Power Factor Correction (PFC) converter with improved common mode noise characteristics. Conventional PFC has limitations due to low efficiency and enlarged heat sink from considerable conduction loss of bridge diode. By applying a Common Mode (CM) coupled inductor, the proposed bridgeless PFC converter generates less conduction loss as only a small magnetizing current of the CM coupled inductor flows through the input diode, thereby reducing or removing heat sink. The input diode is alternately conducted every half cycle of 60 Hz AC input voltage while a negative node of AC input voltage is always connected to the ground, thus improving common mode noise characteristics. With the aim to improve switching loss and reverse recovery of output diode, the proposed circuit employs Critical Conduction Mode (CrM) operation and it features a simple Zero Current Detection (ZCD) circuit for the CrM. In addition, the input current sensing is possible with the shunt resistor instead of the expensive current sensor. Experimental results through 480 W prototype are presented to verify the validity of the proposed circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.1
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• pp.27-33
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• 2016

A pulse-width modulation (PWM) method for common mode noise reduction in a PWM inverter connected to a single-phase grid is proposed in this study. The extensively used conventional switching method may experience common mode voltage problems, which generate current leakage and electromagnetic induction problems. In the proposed switching method, the neutral point of the output voltage is always fixed at both ends of the input voltage to reduce common mode noise. The validity of the proposed method is proven through simulation and experimental results.

• Journal of Power Electronics
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• v.14 no.1
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• pp.40-47
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• 2014

An average current mode control scheme that consistently offers good dynamic performance for LLC series resonant DC-to-DC converters irrespective of the changes in the operational conditions is presented in this paper. The proposed control scheme employs current feedback from the resonant tank circuit through an integrator-type compensation amplifier to improve the dynamic performance and enhance the noise immunity and reliability of the feedback controller. Design guidelines are provided for both current feedback and voltage feedback compensation. The performance of the new control scheme is demonstrated through an experimental 150 W converter operating with 340 V to 390 V input voltage to provide a 24 V output voltage.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1052-1054
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• 2001

This paper describes a boost converter to be operated at the boundary of continuous current mode(CCM) and discontinuous current mode(DCM) for power factor correction and low cost. A control method to be utilized in simulation is a average-current mode method in case of operating in CCM. The simulation results show that Better is the CCM converter then the DCM converter in harmonic content and input current waveform. And A Double-boost converter is superior to single-boost converter for input-current harmonic.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.72-75
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• 2001

The persistent current mode operation of HTS coils is one of the key technologies required for very high-field MRI magnets composed of LTS and HTS coils. But to date, the fabrication of persistent current mode system using HTS is not investigated well. In this paper, we fabricated the magnet and PCS using by BSCCO-2223 tape and jointed them with solder. The current decay behavior of the circuit was measured in liquid nitrogen by monitoring the magnetic field in the centre of magnet with a Hall sensor. To enhance the characteristic of persistent current mode system, superconducting joint method should be investigated.

• Proceedings of the KIEE Conference
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• 2004.07e
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• pp.14-16
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• 2004

This paper describes a boost converter to be operated at the boundary of continuous current mode(CCM) and discontinuous current mode(DCM) for power factor correction and low cost. A control method to be utilized in simulation is a average Current mode method in case of operating in CCM. The simulation results show that Better is the CCM converter then the DCM converter in harmonic content and input current waveform. And A Double-boost converter is superior to single-boost converter for input-current harmonic.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.90-94
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• 2003

Recently, many nations have released standard such as IEC 1000-3-2 and IEEE 519 which impose a limit on the harmonic current drawn by equipment connected to AC line in order to prevent the distortion of an AC line. Among the wide variety of active methods for improving power factor and harmonic distortion, the boost converter is very effective because it has a continuous line current , small choke filter and high power factor. In high power application, however, the bridge diode loss in the boost converter has made the efficiency lower and the temperature of the board higher. A new approach without bridge diode to make the same characteristics of the conventional boost converter has also been developed. This paper present the comparisons between the continuous current mode(CCM) operated conventional boost converter and the boundary current mode(BCM) operated the bridgeless boost converter for high efficiency and high power factor.

• Journal of Power Electronics
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• v.12 no.2
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• pp.242-248
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• 2012

Self oscillating current fed push pull resonant inverters can be controlled without using special drivers. Dc current flows through the choke coil and the power switches, although the driving signals of the power switches are sinusoidal. When the base current is near zero, the transistors cannot be operated in switching mode. Hence higher switching power losses and instantaneous peak power during off transitions are observed. In this study, an alternative design has been proposed to overcome this problem. A prototype circuit has been built which provides dc bias current to the base of the transistors. Experimental results are compared with theoretical calculations to demonstrate the validity of the design. The proposed design decreases the peak and average power losses by about 8 times, when compared to conventional designs.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.275-278
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• 2003

This paper presents a full-adder using current-mode multiple valued logic CMOS circuits. This paper compares propagation delay, power consumption, and PDP(Power Delay Product) compared with conventional circuit. This circuit is designed with a samsung 0.35um n-well 2-poly 3-metal CMOS technology. Designed circuits are simulated and verified by HSPICE. Proposed full-adder has 2.25 ns of propagation delay and 0.21 mW of power consumption.