Kamon Jirasereeamornkul

High efficiency battery management system for serially connected battery string

This article presents an approach for balancing serially connected battery strings with high efficiency energy transferred. The efficiency of this balancing process is accomplished by channeling an excess energy through a DC Link Bus rather than done serially. Using this proposed technique with converter which was 80 percent efficiency, the equalized efficiency of balancing process is increased more than the conventional techniques at least 12.80 percent. By applied this proposed technique to the charge equalized system, the unbalance charging problem can be eliminated. The validity of this approach can be supported by computer simulation and experimental result.

Power harvester design for semi-passive UHF RFID Tag using a tunable impedance transformation

This paper proposes a design of a power harvester for a semi-passive RFID Tag. A tunable impedance transformation circuit is inserted between the antenna and the rectifier unit to maximize the power delivered to the rectifier of a tag and minimize reflections from the antenna input port. A power harvester for the UHF band of 950 MHz has been designed based on a 0.35 µm CMOS technology. This impedance matching is designed to maximize efficiency by characterizing both the tunable impedance transformation circuit and the conventional rectifier circuit. The antenna is modeled as an RF source with series impedance ZS of 50Ω while the rectifier is modeled an impedance ZL, which is approximated from the process and design parameters of the NMOS transistors used in the conventional NMOS rectifier. These two impedances are used to find optimal matching parameters of the chosen lowpass LL matching circuit. The simulation results show that the required voltage for a 1.2V secondary battery can be achieved with the tunable impedance matching circuit and conventional 2-stage rectifier. The DC output of the rectifier yields the maximum DC voltage of 1.77V, the maximum average current of 4.72µA, and the power conversion efficiency of 15.85% for the input RF power of −14.47dBm at the battery voltage of 1.2V.

Implementation of a DC-Side Class-DE Low-

An analysis and design of a single-stage electronic ballast with a dc-side Class-DE low-dv/dt resonant rectifier is studied in this paper to improve a poor power-factor and low line harmonic. The power-factor correction is achieved by utilize an output characteristics of a Class-DE rectifier, which is inserted between the front-end bridge rectifier and the bulk-filter capacitor. The design procedure is based on the principle of the Class-DE rectifier, which also ensures more accurate results and the proposed scheme provided a more systematic and feasible analysis methodology. The active switches can be operated under the soft-switching condition. By employing an electromagnetic interference filter after bridge rectifier, the standard-recovery diode for bridge rectifier can be employed, the cost can be reduced, the conduction angle of the bridge-rectifier diode current was increased, and low line harmonic distortion and a power factor near unity were achieved. The dc-side Class-DE rectifier is driven by a high-frequency current source, which is obtained from the square-wave output voltage of the Class-D series-parallel resonant inverter through an LC-series circuit. A prototype of the ballast, operating at an 84-kHz fixed frequency and a 220-V rms, 50-Hz line voltage, was utilized to drive a T8-36 W fluorescent lamp. The validity of this approach was confirmed by simulation and experimental results.

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This paper presents the use of a novel, single-stage high-power-factor electronic ballast with a symmetrical class-DE low-dυ/dt resonant rectifier as a power-factor corrector for fluorescent lamps. The power-factor correction is achieved by using a bridge rectifier to utilize the function of a symmetrical class-DE resonant rectifier. By employing this topology, the peak and ripple values of the input current are reduced, allowing for a reduced filter inductor volume of the EMI filter. Since the conduction angle of the bridge rectifier diode current was increased, a low-line current harmonic and a power factor near unity can be obtained. A prototype ballast, operating at an 84-㎑ fixed frequency and a 220-Vrms, 50-㎐ line input voltage, was utilized to drive a T8-36W fluorescent lamp. Experimental results are presented which verify the theoretical analysis.

Rectifier as a PFC for Electronic Ballast Application

An analysis and design of a zero-current-switching (ZCS) Class-D current-source driven rectifier for the lighting applications is presented, which is one of the resonant rectifiers as a power-factor corrector to improve a poor power-factor and high line current harmonic of a single-stage converter. A high power-factor is achieved by the utilization of output characteristics of a Class-D ZCS rectifier, which is inserted between the front-end bridge rectifier and the bulk-filter capacitor. The conduction angle of the bridge rectifier diode current was increased and a low-line current harmonic and a power-factor near unity can be obtained. The design procedure is based on the principle of the Class-D ZCS rectifier, which also ensures more accurate results and the proposed scheme provides a high efficiency and a more systematic and feasible analysis methodology. The active switches can be operated under the soft-switching condition. The validity of this approach was confirmed by simulation and experimental results.

Single-Stage High-Power-Factor Electronic Ballast with a Symmetrical Class-DE Resonant Rectifier

An analysis of the junction capacitance in resonant rectifiers which has a significant impact on the operating point of resonance circuits is studied in this paper, where the junction capacitance of the rectifier diode is to decrease the resonant current and output voltage in the circuit when compared with that in an ideal rectifier diode. This can be represented by a simplified series resonant equivalent circuit and a voltage transfer function versus the normalized operating frequency at varied values of the resonant capacitor. A low voltage to high voltage push-pull DC/DC resonant converter was used as a design example. The design procedure is based on the principle of the half bridge class-DE resonant rectifier, which ensures more accurate results. The proposed scheme provides a more systematic and feasible solution than the conventional resonant push-pull DC/DC converter analysis methodology. To increase circuit efficiency, the main switches and the rectifier diodes can be operated under the zero-voltage and zero-current switching conditions, respectively. In order to achieve this objective, the parameters of the DC/DC converter need to be designed properly. The details of the analysis and design of this DC/DC converter’s components are described. A prototype was constructed with a 62–88 kHz variable switching frequency, a 12 VDC input voltage, a 380 VDC output voltage, and a rated output power of 150 W. The validity of this approach was confirmed by simulation and experimental results.

Class-D Zero-Current-Switching Rectifier as Power-Factor Corrector for Lighting Applications

This paper presented a high efficiency Class-D resonant inverter high power factor for induction heating multi-coils hardening application. The main function of the Class-D resonant inverter is to provide high frequency AC from bridge rectifier and LC filter input voltage. The advantages of this technique, the power switched are operated under the zero voltage switching condition and the leakage inductance of transformer can be used the LLC resonant. A prototype Class-D operating at a 102 kHz fixed frequency, 730 W maximum input power. Experimental results, induction hardening had a near unity power factor, total harmonic distortion of the input current THDi 6.5 %, it can be heat up 2 work pieces a same size diameter 9.5-mm from room temperature to 400°C within about 1 minutes and 92 % efficiency at full power.

Analysis and Implementation of a Half Bridge Class-DE Rectifier for Front-End ZVS Push-Pull Resonant Converters

This article present charge equalized module using quasi-resonant flyback converter with DC-link bus strategy. With this technique, turn on switching loss is decrease by 71 percent. Switching at low voltage and operating at low dv/dt, the electromagnetic interferences are also decline. By applied this proposed technique to the charge equalized system, the unbalance charging problem can be eliminated. The validity of this approach can be supported by computer simulation and experimental result.

A high efficiency of a Class-D resonant inverter high power factor for induction heating multi-coils hardening application

This article presents a high efficiency charge equalized system for balancing energy in serially connected battery strings using synchronous flyback converter. The efficiency of this synchronous flyback converter is 80.1 percent. By applying this proposed converter along with DC Link Bus technique in charge equalized system, the unbalance charging problem can be eliminated. The validity of this approach can be supported by experimental result.

Charge equalized module for serially connected VRLA battery string using quasi-resonant flyback converter

Optimum combining is already mentioned to be good matched technique for suppressing the multipath fading and reducing the effect of co-channel interference (CCI) in wireless communications. It has been used for either Gaussian fading channels and non-Gaussian fading channels for different conditions and purposes. In this paper, the performance evaluation of wireless digital communication systems for linear minimum mean square error diversity is investigated. The approach of this paper and its main contribution is to model the non-Gaussian fading channel of wireless systems. A new expression of outage probability in a non-Gaussian fading environment is studied by modeling fading channel as a spherically invariant random process (SIRP). As a special case of this work, it is straightforward to consider the situation where the interferers have equal powers and their number is no less than the diversity order. Finally, some numerical results show the impact of the number of antenna elements, the number of interferers and noise.