Roskhatijah Radzuan

The designs of low power AC-DC converter for power electronics system applications

This paper reviews low power AC-DC converter in different techniques capable of developing high efficiency of energy consumption in many applications. By using low power AC-DC converter, the size of whole system integrated circuit could be reduced. However, the requirements of CMOS converter that required low input voltage and low voltage drop of MOS transistors is discussed. Different techniques in different application are implemented to overcome those problems. In this paper, the reviews of low power AC-DC converters have been focused for energy harvesting systems and wireless power devices only. These AC-DC converters consume several micro-watts from small ac or rf signal voltage and achieve excellent performance in terms of power efficiency. However, the power efficiency of AC-DC converter system is actually highly correlated to the relationship between voltage and the alternating current in ac source. It is because, an in-phase voltage and current in alternating current source is causing in good power factor performance. Power factor correction, PFC is important in many single-phase AC-DC converter circuits to reduce harmonic distortion, hence increase power efficiency of electric appliances. Therefore, the low power AC-DC converter with PFC is proposed. The post-layout of low power AC-DC converter is designed by using the Silterra 0.18 μm technology. The whole post-layout AC-DC converter circuit consumes only 50 μW and works in low voltage, 1V. The power efficiency of whole system also improved to 93%. The proposed low power AC-DC converter with PFC is suitable for future power electronics systems such as battery charger and energy conversion devices.

Effect of different widths in CMOS rectifier for low voltage and frequency application

This paper presents the study on the effect of different widths in CMOS rectifier for low voltage and frequency application. The model is powered by 1V peak voltage of AC supply with frequency of 50Hz. This low frequency is used in this paper to match with the supply frequency from the power plant. The design is based on the CMOS 0.18um technology. The paper focuses on the effect of the two different width sizes (4um and 50um). The result for 4um is 558.36mV and increased by 40.6% for 50um width. The simulation is run using CADENCE Simulation Tools software.

Realization assessment of stabilizer with presonication on size-distribution of itraconazole nanoparticulate in wet-nanomilling

The paper investigates fabrication of itraconazole nanoparticulate in wet-nanomilling by appropriate alteration of the suspension properties and the milling parameters. By wet-nanomilling, stable nano-scale particulate can be prepared which have better physical properties. In this study, effects of adding stabilizer on nanoparticulate size and polydispersity index were performed during production of itraconazole nanoparticulate. In addition, the effect of pre-sonication followed by wet grinding was assessed on the particulate size of itraconazole in dispersion containing stabilizer. The size of drug particulate was reduced to less than 200nm with a polydispersity index (PDI) below 1.0 thus influencing the milling process under these conditions.

CADENCE simulation studies on the effect of transistor width size on internal resistance in CMOS rectifier using two PMOS and NMOS

This paper presents studies on the effects of the transistor width size on internal resistance in CMOS rectifier using two PMOS and NMOS configurations. The minimum value of 4 μm widths size of MOSFET in CMOS Rectifier are applied up to maximum value of 1500 μm. The proposed work was designed, modelled and simulated using CADENCE software. The best configuration of the width size on the PMOS and NMOS internal resistance are represented with the lowest internal resistance possible for miniaturizing the CMOS Rectifier. The simulation results are presented to verify the proposed configurations.

Verified in vitro characteristics of ketoconazole and itraconazole nanoparticulates in wet-nanomilling

The paper describes verification of in vitro characteristics of ketoconazole and itraconazole nanoparticulates in wet-nanomilling, as well as their physicochemical properties. By wet-nanomilling, stable nanoscale particulates can be prepared which have better physical properties. In this study, nanoparticulate drugs were characterized in shape and structure using the scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) was used to determine the chemical functional groups in the sample. Implied chemical changes of the structure of pure ketoconazole and itraconazole due to the formation of nanoparticulates were investigated by using the IR spectra.

An optimization model of the input current for a variable input voltage in CMOS AC/DC converter

An optimization model of the input current for a variable input voltage in CMOS AC/DC converter is proposed in order to achieve regulation control of an AC/DC converter. An input current model of CMOS converter is obtained by applying an average method in converter circuit over ones switching period. This model is implemented in Pspice circuit simulation tool to verify an averaged model of the input current. The results show that the input current exhibits an increasing response to input voltage variation from 0.3 to 1.5 V. The validity of the proposed steady-state model is verified by the given simulation results for a specified design of CMOS converter. A good agreement is obtained between steady-state model and simulation results.

Modeling of AC-DC converter using 0.18 μm CMOS technology

This paper proposes a modeling of low-power CMOS transistors, which are suitable for AC-DC converter applications. First section described DC analysis of input and output device of CMOS transistor using Spectre simulation tool from Cadence Design Systems. After that, advanced CMOS transistors have been applied onto development of low-voltage CMOS AC-DC converter with minimized voltage drop and power consumption. The input voltage is set to 1.0 V and the operating power supply frequency is 50 Hz. As a result, the CMOS rectifier has gained 94% of power efficiency and very small voltage drop, 39 mV with purely resistive load.

CMOS single-stage input-powered bridge rectifier with boost switch and duty cycle control

ABSTRACT This paper presents a single-stage input-powered bridge rectifier with boost switch for wireless-powered devices such as biomedical implants and wireless sensor nodes. Realised using CMOS process technology, it employs a duty cycle switch control to achieve high output voltage using boost technique, leading to a high output power conversion. It has only six external connections with the boost inductance. The input frequency of the bridge rectifier is set at 50 Hz, while the switching frequency is 100 kHz. The proposed circuit is fabricated on a single 0.18-micron CMOS die with a space area of 0.024 mm2. The simulated and measured results show good agreement.

CMOS bridge rectifier boost converter with internal ASIC DPWM

This paper presents the Application Specific Integrated Circuit (ASIC) design of a Digital Pulse Width Modulation (DPWM) signal generator, for the implementation of PWM control signal generator, to be integrated on a single die with the single-stage input-powered bridge rectifier with boost switch (BRBS) DC boost converter, in view to eliminate the need of external PWM control signal generator, while reducing the overall size of the rectifier system. The proposed controller is implemented on 0.18-micron CMOS process technology using a single die with space area of 180.238 mm2. This controller design has the total cell counts of 273 and has the power consumption of 1.2358 mW. Synopsys Design Compiler and Synopsys Astro design tools are used to produce the digital design part, while for the integration of digital and analog design parts, Cadence Virtuoso is used. Theoretical analysis for the proposed PWM control signal generator are provided and verified by simulation results.

Development of thin film capacitors for power system applications by PVD technique

Thin film capacitors are very interesting option to electrolytic capacitors, because they are simple, compact in structure and effective for fabrication of high frequency devices. Thin film coating capacitors also improved processing characteristics and better dielectric strength. This paper reports the development of thin film capacitors for DC filtering in AC/DC converter application. The design of thin film capacitor for high frequency AC/DC converter is implemented using simple simulation tools. The primary research hypothesis is that high frequency capacitance with smaller size can be implemented using Physical Vapor Deposition, PVD technique. The thickness of TiO2, area of metal contact and dielectric properties of TiO2 are considered as parameters for thin film capacitors development.