Selim Borekci

Electronically-Tunable Current-Mode Biquad Design Using MO-OTAs

In this paper, electronically-tunable, current-mode biquad is proposed by using multiple-output operational transconductance amplifiers (MO-OTAs). The proposed circuit has one input and two outputs. Without changing the circuit topology, low-pass (LP), and band-pass (BP) responses can be realized. The filter is realized by using two MO-OTAs, a single-output OTA (SO-OTA), a two-output OTA and two grounded capacitors. The biquad is designed based on first-order LP filter or lossy integrator blocks. The feedback block is applied to the filter circuit in order to obtain high quality factor values greater than 1/2. The center frequency and the quality factor of the LP and BP filters can be electronically tuned by DC current of OTAs. The total power dissipation of the proposed biquad is approximately 10mW at ±3V supplied voltage. The theoretical analysis is also confirmed with SPICE simulations.

An accurate way of determining BJT's switching loss in medium and high voltage applications

Semiconductors are widely used in power electronics applications as a switching device. In some applications, BJTs are used and their power loss calculation has a crucial effect on the temperature performance of transistors which must be in thermal limits. The power loss can be analyzed in three states; on, off and transition. In recent studies, on state loss has been calculated by estimation. In addition to that, in higher voltage applications, it is difficult to measure collector-emitter voltages (VCE) to calculate on and transient state losses correctly due to tolerances of voltage probes. An accurate power loss calculation method of BJT devices has been presented in this research in which the losses are evaluated by measuring only the base (IB) and the collector currents (Ic) without any estimation. The method does not require collector-emitter voltage measurements. The proposed method has been experimented on a current fed push-pull resonant inverter.

Dimmable electronic ballasts by variable power density modulation technique

Dimming can be accomplished commonly by switching frequency and pulse density modulation techniques and a variable inductor. In this study, a variable power density modulation (VPDM) control technique is proposed for dimming applications. A fluorescent lamp is operated in several states to meet the desired lamp power in a modulation period. The proposed technique has the same advantages of magnetic dimming topologies have. In addition, a unique and flexible control technique can be achieved. A prototype dimmable electronic ballast is built and experiments related to it have been conducted. As a result, a 36WT8 fluorescent lamp can be driven for a desired lamp power from several alternatives without modulating the switching frequency.

Comparative Analysis of Reduced-Rule Compressed Fuzzy Logic Control and Incremental Conductance MPPT Methods

Photovoltaic (PV) power generation has been widely used in recent years, with techniques for increasing the power efficiency representing one of the most important issues. The available maximum power of a PV panel is dependent on environmental conditions such as solar irradiance and temperature. To extract the maximum available power from a PV panel, various maximum-power-point tracking (MPPT) methods are used. In this work, two different MPPT methods were implemented for a 150-W PV panel. The first method, known as incremental conductance (Inc. Cond.) MPPT, determines the maximum power by measuring the derivative of the PV voltage and current. The other method is based on reduced-rule compressed fuzzy logic control (RR-FLC), using which it is relatively easier to determine the maximum power because a single input variable is used to reduce computing loads. In this study, a 150-W PV panel system model was realized using these MPPT methods in MATLAB and the results compared. According to the simulation results, the proposed RR-FLC-based MPPT could increase the response rate and tracking accuracy by 4.66% under standard test conditions.

PV system flyback converter controlled PI control to charge battery under variable temperature and irradiance

This paper proposes to Flyback converter sourced photovoltaic (PV) Panel is controlled by PI technology, under variable irradiance (800 W/m2 to 1000 w/m2) and temperature (25 °C to 40 °C). The system was used to charge Lithium ion battery for PV panel applications. Voltage and power of PV panels are nonlinear they depend on environment conditions like irradiation and temperature. PV system can be thought as a DC (direct current) source so that one of the DC-DC converters, flyback converter, is used to regulate voltage and current of the PV panel. Flyback converters provide insulation between load and source also by adjustable turn ratio of transformer the load voltage can be regulated. PI control applied to switch (MOSFET) of flyback converter to regulate duty cycle of PWM (Pulse Width Modulation), to charge battery with constant voltage method. The maximum power point of PV module which used in this system, under STC (1000 W/m2 and 25 °C), is around 50 W and the load power of the flyback converter in that condition is around 40 W. The efficiency of system under STC is around 80 %, but when irradiation level decreases to 800 W/m2 and the temperature step up to 40 °C the efficiency of system increases (>95 %). The system was analyzed and constructed in Matlab1Simulink.