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1.
A flexible microcontroller-based data acquisition device
Darko Hercog, Bojan Gergič, 2014, izvirni znanstveni članek

Opis: This paper presents a low-cost microcontroller-based data acquisition device. The key component of the presented solution is a configurable microcontroller-based device with an integrated USB transceiver and a 12-bit analogue-to-digital converter (ADC). The presented embedded DAQ device contains a preloaded program (firmware) that enables easy acquisition and generation of analogue and digital signals and data transfer between the device and the application running on a PC via USB bus. This device has been developed as a USB human interface device (HID). This USB class is natively supported by most of the operating systems and therefore any installation of additional USB drivers is unnecessary. The input/output peripheral of the presented device is not static but rather flexible, and could be easily configured to customised needs without changing the firmware. When using the developed configuration utility, a majority of chip pins can be configured as analogue input, digital input/output, PWM output or one of the SPI lines. In addition, LabVIEW drivers have been developed for this device. When using the developed drivers, data acquisition and signal processing algorithms as well as graphical user interface (GUI), can easily be developed using a well-known, industry proven, block oriented LabVIEW programming environment.
Ključne besede: data acquisition, DAQ, microcontroller, analogue-to-digital converter, ADC, USB, HID, LabVIEW, GUI, data logging
Objavljeno: 22.06.2017; Ogledov: 671; Prenosov: 286
.pdf Celotno besedilo (1,98 MB)
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2.
High-precision hysteresis sensing of the quartz crystal inductance-to-frequency converter
Vojko Matko, Miro Milanovič, 2016, izvirni znanstveni članek

Opis: A new method for the automated measurement of the hysteresis of the temperature-compensated inductance-to-frequency converter with a single quartz crystal is proposed. The new idea behind this method is a converter with two programmable analog switches enabling the automated measurement of the converter hysteresis, as well as the temperature compensation of the quartz crystal and any other circuit element. Also used is the programmable timing control device that allows the selection of different oscillating frequencies. In the proposed programmable method two different inductances connected in series to the quartz crystal are switched in a short time sequence, compensating the crystal’s natural temperature characteristics (in the temperature range between 0 and 50 °C). The procedure allows for the measurement of the converter hysteresis at various values of capacitance connected in parallel with the quartz crystal for the converter sensitivity setting at selected inductance. It, furthermore, enables the measurement of hysteresis at various values of inductance at selected parallel capacitance (sensitivity) connected to the quartz crystal. The article shows that the proposed hysteresis measurement of the converter, which converts the inductance in the range between 95 and 100 μH to a frequency in the range between 1 and 200 kHz, has only 7 × 10−13 frequency instability (during the temperature change between 0 and 50 °C) with a maximum 1 × 10−11 hysteresis frequency difference.
Ključne besede: inductance-to-frequency converter, hysteresis, automated measurement, sensor switching method, inductance, quartz crystal, temperature compensation
Objavljeno: 30.06.2016; Ogledov: 1250; Prenosov: 354
.pdf Celotno besedilo (3,93 MB)
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3.
SWITCHED CAPACITOR-BOOST CONVERTER FOR THERMOELECTRIC SYSTEM
Leon Maruša, 2015, magistrsko delo

Opis: The purpose of this work was to develop and test the switched capacitors-boost converter (SC-BC), which can be used for stepping up voltage by a factor of at least ten driving energy harvesting applications. Extensive mathematical modelling of SC-BC was done for obtaining its nonlinear model and equations of multiple static characteristics. Simulations of SC-BC and its simplified models were done within a PSIM environment. The choice was made for closed-loop to use the combination of a PI controller and sliding mode control due to the robustness requirements and excellent closed-loop dynamics. Control was implemented on digital signal processor TMS320F28335 within a MATLAB/SIMULINK environment. Lastly the open and closed-loop experiments were done on a real SC-BC prototype.
Ključne besede: switched capacitors, boost converter, sliding mode control, energy harvesting, mathematical modelling
Objavljeno: 14.10.2015; Ogledov: 1358; Prenosov: 154
.pdf Celotno besedilo (5,47 MB)

4.
SOFT SWITCHING FOR IMPROVING THE EFFICIENCY AND POWER DENSITY OF A SINGLE-PHASE CONVERTER WITH POWER FACTOR CORRECTION
Tine Konjedic, 2015, doktorska disertacija

Opis: This thesis investigates the possibilities for increasing the power conversion efficiency and power density of a single-phase single-stage AC-DC converter with power factor correction capability. Initially, the limitations are investigated for simultaneous increase of power density and efficiency in hard switched bidirectional converters. The switching frequency dependent turn-on losses of the transistors have been identified as the main limiting factor. In order to avoid the increase in total power losses with increasing the switching frequency, a control approach is proposed for achieving zero voltage switching transitions within the entire operating range of a bidirectional converter that utilizes power transistors in a bridge structure. This approach is based on operation in the discontinuous conduction mode with a variable switching frequency. Operation in the discontinuous conduction mode ensures the necessary reversed current that naturally discharges the parasitic output capacitance of the transistor and thus allows this transistor to be turned on at zero voltage. On the other hand, the varying switching frequency ensures that the converter operates close to the zero voltage switching boundary, which is defined as the minimum required current ripple at which zero voltage switching can be maintained. Operation with the minimum required current ripple is desirable as it generates the lowest magnetic core losses and conduction losses within the power circuit. The performance and effectiveness of the investigated approach were initially verified in a bidirectional DC-DC converter. A reliable zero voltage switching was confirmed over the entire operating range of a bidirectional DC-DC converter, as well as the absence of the reverse recovery effect and the unwanted turn-on of the synchronous transistor. In order to justify its usage and demonstrate its superior performance, the proposed zero voltage switching technique was compared with a conventional continuous conduction mode operation which is characterized by hard switching commutations. After successful verification and implementation in a bidirectional DC-DC converter, the investigated zero voltage switching approach was adapted for usage in an interleaved DC-AC converter with power factor correction capability. Comprehensive analysis of the converter's operation in discontinuous conduction mode with a variable switching frequency was performed in order to derive its power loss model. The latter facilitated the design process of the converter's power circuit. A systematic approach for selecting the converter's power components has been used while targeting for an extremely high power conversion efficiency over a wide operating range and a low volume design of the converter. The final result of the investigations performed within the scope of this thesis is the interleaved AC-DC converter with power factor correction capability. Utilization of interleaving allows for increasing the converter's power processing capability, reduces the conducted differential mode noise and shrinks the range within which the switching frequency has to vary. The proposed zero voltage switching control approach was entirely implemented within a digital signal controller and does not require any additional components within the converter's circuit. The experimental results have confirmed highly efficient operation over a wide range of operating powers. A peak efficiency of 98.4 % has been achieved at the output power of 1100 W, while the efficiency is maintained above 97 % over the entire range of output powers between 200 W and 3050 W.
Ključne besede: zero-voltage switching, power factor correction, variable switching frequency, discontinuous conduction mode, reverse recovery, unwanted turn-on, bidirectional DC-DC converter, bidirectional AC-DC converter, control of switching power converters
Objavljeno: 13.10.2015; Ogledov: 1485; Prenosov: 166
.pdf Celotno besedilo (23,37 MB)

5.
Acoustic noise emissions caused by transformer in a DC/DC converter for welding appliactaions [!]
Gorazd Štumberger, Klemen Deželak, Drago Dolinar, Beno Klopčič, 2012, objavljeni znanstveni prispevek na konferenci (vabljeno predavanje)

Opis: This paper deals with the acoustic noise emissions caused by the transformer operating as a part of DC/DC converter in an industrial resistance spot welding system. The discussed DC/DC converter is schematically shown in Fig. 1. The three-phase alternating voltages (u1, u2 and u3) are rectified and smoothed in order to obtain almost constant DC-bus voltage UDC. The H-bridge inverter is used to supply the transformerćs primary winding with voltage pulses uH. The two transformerćs secondary windings are connected to the two output rectifier diodes (D1 and D2) which provide the direct welding current iL flowing through the load represented by LL and RL. A new control scheme forresistance spot welding systems was proposed in [1,2]. During the testing of the proposed control scheme it became evident that the proposed control scheme not only improves utilization of the iron core and prevent it from becoming saturated, but also substantially reduces the acoustic noise emissions caused by the transformer. The reasons for reduction of acoustic noise emission are discussed in this paper.
Ključne besede: DC/DC converter, acoustic noise emissions
Objavljeno: 10.07.2015; Ogledov: 1547; Prenosov: 38
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6.
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