Kyu-Min Cho

Multi-phase interleaved LLC-SRC and its digital control scheme

This paper proposes a new 3-phase interleaved LLC resonant DC-DC converter and its control scheme. The proposed circuit consists of three conventional interleaved LLC resonant DC-DC converters and each converter operates with π/3 of phase difference respectively. Therefore the current ripple of the output capacitor can be significantly reduced and the life cycle of the converter will be extended. To verify the validity of the proposed converter and digital scheme, an experiment with a prototype 1kW (12V/84A) DC-DC converter was implemented and its results are presented in this paper.

Optimized neural network speed control of induction motor using genetic algorithm

For the high performance drives of induction motor, recurrent artificial neural network (RNN) based self tuning speed controller is proposed. RNN provides a nonlinear modeling of motor drive system and could give the information of the load variation, system noise and parameter variation of induction motor to the controller through the on-line estimated weights of corresponding RNN. Self tuning controller can change gains of the controller according to system conditions. The gains are composed of the weights of RNN. For the on-line estimation of the weights of RNN, extended Kalman filter (EKF) algorithm should be used. In order to design EKF with optimal constants, simple genetic algorithm is proposed. Genetic algorithm can follow the optimal estimation constants without trial and error efforts. The availability of the proposed controller is verified through the MATLAB and Simulink simulation with the comparison of conventional controller. The simulation results show a significant enhancement in shortening development time and improving system performance over a traditional manually tuned EKF estimation algorithm based neural network controller

Current-controllable FDNRs using linear transcapacitance amplifiers

A systematic synthesis process is described for the simulation of current-controllable FDNRs using linear transcapacitance amplifiers. The process is used to obtain three circuits; two are believed to be novel. The values of the FDNRs are controllable by adjusting the bias currents of the transcapacitance amplifiers. In order to implement the obtained FDNRs, a new transcapacitance amplifier is designed. Operation principles of designed circuits are presented and experimental results are used to verify theoretical predictions. The results show close agreement between predicted behaviour and experimental performance.

A New Dimming Algorithm for the Electrodeless Fluorescent Lamps

In this paper, a new dimming algorithm for the electronic ballast of an electrodeless fluorescent lamp is proposed. The proposed method is based on the burst dimming method that controls the duty ratio for the two switches of the electronic ballast by intermittently modulated pulse signal. This paper presents a fully digital circuit using an erasable programmable logic device (EPLD). To verify the validity of the proposed method, the implemented control circuit was applied to the electronic ballast for a 100 W electrodeless fluorescent lamp. As a result, a dimming method with a wide illumination range from 5 to 100% was obtained.

A novel average burst-duty control method for the dimming of induction lamps

In this paper, a new dimming algorithm for the electronic ballast of an electrodeless fluorescent lamp is proposed. The proposed method is based on the burst dimming method that controls the duty ratio for the two switches of the electronic ballast by intermittently modulated pulse signal. This paper presents a fully digital circuit using an erasable programmable logic device (EPLD). To verify the validity of the proposed method, the implemented control circuit was applied to the electronic ballast for a 100 W electrodeless fluorescent lamp. As a result, a dimming method with a wide illumination range from 5 to 100% was obtained

A new high voltage shorted-anode IGBT with intrinsic body diode improves performance of single-ended induction cooker

Nowadays the field-stop (FS) IGBT provides lower saturation voltage drop and lower switching losses than the conventional non-punch-through (NPT) IGBT, making the FS IGBT well suited for induction heating (IH) applications. A relatively recent improvement in the FS IGBT - the integration of an antiparallel diode on the IGBT die through use of the shorted-anode (SA) technology - made the FS IGBT even better for IH designs. The aim of this paper is to demonstrate the effectiveness of Fairchild semiconductors second generation FS SA trench IGBT. Although the new device combines both IGBT and body diode functions, it can provide better performances by means of an advanced field stop trench IGBT technology. The single-ended (SE) resonant inverter for induction cooking application is analyzed and experiments for two 2kW SE induction cookers were carried out to verify the validity of new IGBT.

Fully digital controlled electronic ballast for electrode-less lamps

This Paper presents digital control based and remote controlled electronic ballast for electrode-less lamps. In order to control the power of lamp driven by high-frequency electronic ballast, remote control is necessary. For the group lighting system, especially, wireless remote control using RF modem is proper. In this paper, 2.4-GHz ISM band RF modem based remote controlled electronic ballast is proposed. However, the cost of RF modem is relatively expensive as compare with the cost of electronic ballast. For the economic realization, one-controller two-lamps system is proposed. And the proposed control circuit of the ballast is implemented with fully digital circuit using low cost 16-bit DSP and small size EPLD. Detailed algorithms for the power control and protections for the commercial electronic ballast are described. Finally, the wire and wireless linked group lighting system using the proposed ballast is introduced.

Effectiveness of FRFET® MOSFETs for the CCFL inverters in LCD TVs

For the backlighting of most LCD panels such as TVs and monitors today, CCFL (cold cathode fluorescent lamp) is widely used because it can provide both low cost manufacturing and high quality color gamut. To illuminate the CCFL, half-bridge or full-bridge resonant inverters are necessary. Although resonant inverters can work under the ZVS condition when the PFM (pulse frequency modulation) method is applied, most major LCD manufacturers adopt the PWM (pulse width modulation) method to control their LCDpsilas CCFL inverter because not only the color gamut might be varied but also its stability will be unstable when the inverter is operated by the PFM method due to its incremental resistance according to the varying the switching frequency. In the cases where CCFL inverter works with PWM method, the hard switching operation is inevitable and the additional diodes must be required because the reverse recovery behavior of the MOSFETpsilas body diode is inferior to FRD (fast recovery diode), which causes a large amount of switching loss and it will even make the system failure due to the shoot-through current. In this paper, a newly improved FRFET MOSFET with superior reverse recovery characteristics is introduced and the experimental results for applying it to 42rdquo LCD TV are presented. From these results, the validity of the new FRFET has been verified. The reverse recovery time is shorter than 40 ns and irr is also much smaller than the typical power MOSFETs, which are sufficient to prevent the MOSFETpsilas failures without the external diodes in CCFL BLU (back light unit) system.

A fully digitally controlled power supply unit for wireless remote controlled LED lighting systems

This paper presents a fully digital controlled power supply unit for the wireless controlled dimmable LED lighting system. The proposed power supply designed using fly-back converter, which is directly controlled by a microprocessor. Although the proposed circuit does not sense the AC input current and has not AC input voltage feed-forward, it can achieve high power factor. The proposed power supply directly regulates the output power for LED loads using the PWM and PFM control of the fly-back converter without additional regulator. For a wireless remote control function, the Zigbee modem is equipped in the proposed power supply. A prototype set-up has been built and tested. Through the experiment with a prototype set-up, the usefulness of the proposed power supply is verified.

A new switching scheme for resonant inverters using a resonant-frequency tracking algorithm

This paper presents a new switching scheme for resonant inverters. The proposed method bases on the tracking algorithm of the resonant frequency. Therefore, the proposed method can keep unity output displacement factor at the load-impedance varying conditions. In order to control the output power, the proposed scheme uses pulse width modulation (PWM) method. Thus, since the proposed PWM scheme needs load-circulating operations, it can be adopted in the full-bridge inverter, but not in the conventional half-bridge inverters. In response to that, this paper also proposes a new half-bridge resonant inverter having load-circulating operation modes. In this paper, detailed switching schemes and control circuits of the proposed PWM method are described. Experimental results of the prototype experimental setup to verify the validity of the proposed method are presented and discussed.