Young Hwan Lho

A study on radiation effects on PWM-IC controller of DC/DC power buck converter

DC-DC converter is composed of a PWM-IC (pulse width modulation-integrated circuit) controller, a MOSFET (metal-oxide semiconductor field effect transistor), inductor, capacitor, etc. PWM is applied to control and regulate the total output voltage. It is shown that the variation of threshold voltage at MOSFET and the offset voltage increase caused by radiation effects make the PWM pulse unstable. Radiation gives the main influence on the changes in the electrical characteristics of PWM-IC and MOSFET. In the PWM operation, the missing pulses, the changes in pulse width, and a change of the output waveform are studied by the simulation program with integrated circuit emphasis (SPICE) and compared with experiments.

A Study on the Design of Voltage Mode PWM DC/DC Power Converter

DC/DC switching power converters are commonly used to generate a regulated DC output voltages with high efficiencies from different DC input sources. The voltage mode DC/DC converter utilizes MOSFET (metal-oxide semiconductor field effect transistor), inductor, and a PWM (pulse-width modulation) controller with oscillator, amplifier, and comparator, etc. to efficiently transfer energy from the input to the output at periodic intervals. The fundamental boost converter and a buck converter containing a switched-mode power supply are studied. In this paper, the electrical characteristics of DC/DC power converters are simulated by program of SPICE, and the PWM controller is implemented to check the operation. In addition, power efficiency is analyzed based on the specification of each component.

Design of non-uniform 100-V super-junction trench power MOSFET with low on-resistance

The specific on-resistance of non-uniform super-junction (SJ) trench metal-oxide semiconductor field-effect transistor (TMOSFET) is superior to that of uniform SJ TMOSFET under the same breakdown voltage. For the desired blocking voltage with 100-V, the electric field varies exponentially with distance between the drain and the source regions. The idea with a linearly graded doping profile is proposed to achieve a much better electric field distribution in the drift region. The doping concentration linearly decreases in the vertical direction from the N drift region at the bottom to the channel one at the upper. The structure modeling and the characteristic analyses for doping density, potential distribution, and electric field are simulated by using of the SILVACO TCAD 2D device simulator, Atlas. As a result, the specific on-resistance of 0.66 mΩ · cm2 at the class of 100 V and 100 A is successfully optimized in the non-uniform SJ TMOSFET, which has the better performance than the uniform SJ TMOSFET in the specific on-resistance.

Transient Stability Improvement of a System Connected with Wind Energy Generators

Abstract This paper proposes a methodology to improve the transient stability (TS) of a system with wind energy generators. Induction machines are used widely as generators in the wind power plants. As these induction machines also have the stability problem like other synchronous machines, it is very important to analyze the TS of a system including the wind power plants. In this paper, the simulations and analysis of TS of power system including the induction generators during the short circuit fault conditions are carried out. The effect of pitch angle control on the stability of power system is analyzed. From the simulation results, it can be observed that the pitch control system which prevents the excess wind speed has the significant effect on the TS enhancement of the system. It can also be observed that the controller gain and time constant values have considerable effect on the pitch control system.

Optimum Location of Voltage Regulators in the Radial Distribution Systems

Abstract In this paper, a new heuristic algorithm is proposed for the optimum voltage control, which is applicable for the large Radial Distribution Systems (RDSs). In the RDSs, voltage levels at different buses can be maintained within the specified limits using the conductor grading or placing the Voltage Regulators (VRs) and capacitors at suitable locations. The proposed Back Tracking Algorithm (BTA) proposes the optimal location, number and tap positions of VRs to maintain the voltage profile within the desired limits and decreases losses in the system, which in turn maximizes the net savings in the operation of distribution system. In addition to BTA, an approach using the fuzzy logic called Fuzzy Expert System (FES) is also proposed, and the results of FES are compared with the results of BTA. This heuristic algorithm proposes the optimal location and tap setting of VRs, which contributes a smooth voltage profile along the network. It also used to access the minimum number of initially considered VRs, by moving them in such way as to control the network voltage at minimum possible cost. It is concluded that the FES also gives the optimal placement and the number along with the tap settings of VRs. The proposed FES contributes good voltage regulation, and decreases the power loss which in turn increases the net savings when compared to the BTA. The effectiveness of the proposed heuristic approaches are examined on practical 47 bus and 69 bus Radial Distribution Systems (RDSs).

A Study on Effective Control Methodology for DC/DC Converter

Abstract: DC/DC converters are commonly used to generate regulated DC output voltages with high-power efficiencies from different DC input sources. The converters can be applied in the regenerative braking of DC motors to return energy back to the supply, resulting in energy savings for the systems at periodic intervals. The fundamental converter studied here consists of an IGBT (Insulated Gate Bipolar mode Transistor), an inductor, a capacitor, a diode, a PWM-IC (Pulse Width Modulation Integrated Circuit) controller with oscillator, amplifier, and comparator. The PWM-IC is a core element and delivers the switching waveform to the gate of the IGBT in a stable manner. Display of the DC/DC converter output depends on the IGBTs changes in the threshold voltage and PWM-ICs pulse width. The simulation was conducted by PSIM software, and the hardware of the DC/DC converter was also implemented. It is necessary to study the fact that the output voltage depends on the duty rate of D, and to compare the output of experimental result with the theory and the simulation. Keywords: DC/DC converter, PWM-IC, duty rate, IGBT, DC motor

A Study on the Design of a Pulse-Width Modulation DC/DC Power Converter

DC/DC Switching power converters are commonly used to generate regulated DC output voltages with high-power efficiencies from different DC input sources. A switching converter utilizes one or more energy storage elements such as capacitors, or transformers to efficiently transfer energy from the input to the output at periodic intervals. The fundamental boost converter studied here consists of a power metal-oxide semiconductor field effect transistor switch, an inductor, a capacitor, a diode, and a pulse-width modulation circuit with oscillator, amplifier, and comparator. A buck converter containing a switched-mode power supply is also studied. In this paper, the electrical characteristics of DC/DC power converters are simulated by simulation program with integrated circuit emphasis (SPICE). Furthermore, power efficiency was analyzed based on the specifications of each component.

Total ionizing dose effects on the IGBT performance for a DC-DC converter

IGBT in power system has been dominating MOS (Metal Oxide Semiconductor) transistor since IGBTs (Insulated Gate Bipolar Transistor) guarantee better conduction loss and large current capacity. The radiation induced characteristics of IGBT are mainly emphasized the threshold shifting due to the oxide charge trapping in MOS and the reduction of current gain in the bipolar transistor being inherently composed in the IGBT structure. A lot of analysis on IGBT irradiation has been carried out by researchers. The IGBT in the converter plays an important role in switching. In this paper, the IGBT macro-model for the DC/DC converter is implemented and analyzed the electrical characteristics by SPICE simulation model. In addition, the design SPICE parameters of BF (forward beta), KP (MOS trans-conductance), and VT (threshold voltage) by γ radiation effects are evaluated.

A /spl gamma/ effect on the power MOSFET

The electrical characteristics of solid state devices such as BJT (bipolar junction transistor) and MOSFET, etc. are altered by impinging photon radiation and temperature in the space environment In this paper, the threshold voltage, the breakdown voltage, and the on-resistance for the two kinds of MOSFETs (200 V and 100 V of V/sub DSS/) are tested to /spl gamma/-irradiation and compared with the specifications under the pre and post irradiation of low dose rates of 4.97 and 9.55 rad/sec, and maximum total dose of 30 Krad. In our experiment, the /spl gamma/ radiation facility with low dose available at KAERI (Korea Atomic Energy Research Institute) has been applied on two commercially available IR (International Rectifier) products of IRFP250 and IRF540.

The Implementation of Testing Board for Single Event Upsets

One of the major problem encountered in nuclear plants and satellites design is EMI (Electro-Magnetic Interference) and EMC (Electro-Magnetic Compatibility). Here, our focus is to implement the test board for checking SEU (Single Event Upsets); the effects of protons on the electronic system. The SEU results from the level change of stored information due to photon radiation and temperature in the space environment. The impact of SEU on PLD (Programmable Logic Devices) technology is most apparent in ROM/SRAM/DRAM devices wherein the state of storage cell can be upset. In this paper, a simple and powerful test techniques is suggested, and the results are presented for the analysis and future reference. In our experiment, the proton radiation facility (having the energy of 50 MeV with a beam current of 60 uA of cyclotron) available at KIRAMS (Korea Institute of Radiological Medical Sciences) has been applied on a commercially available SRAM manufactured by Hynix Semiconductor Company.