Digital Current Mode Control for Buck-Converter Based on Average Inductor Current Measurement

This paper introduces a digitally performedcurrent mode and voltage control for the dc-dc step downconverter based on voltage to frequency converter where theaverage values of inductor current and output voltage areobtained. These current and voltage measurement arerealized by the voltage control oscillator (VCO) andcounters (digital integrator). Such an approach enables fulldigitalization of current and voltage control loops

Korekcija faktora faznog pomaka trofaznog trorazinskog uzlaznog ispravljača zasnovanog na PWM-u

Pulse width modulation (PWM) strategy for a matrix structured three-phase three-level AC to DC boost rectifier is developed. Such approach has been used on purpose to control the input displacement power factor close to unity. The connection between matrix switching function and PWM requirement very well describes all restrictions that occur in the modulation algorithm. This modulation algorithm enables the input displacement factor correction without an input current sensor. The only necessary control variable is the measured displacement angle between input voltage and input current.U radu je razvijen PWM algoritam za upravljanje matrično-strukturiranim trofaznim trorazinskim ispravljačem. Takav način upravljanja uzet je radi mogućnosti korekcije faktora pomaka (cos fi) na jediničnu vrijednost. Veza između prekidačkih funkcija i zahtjeva na impulsno-širinski modulator jasno opisuje sva ograničenja modulacijskog algoritma. Razvijeni modulacijski algoritam omogućuje korekciju faktora pomaka bez mjerenja ulazne struje pretvarača. Za potrebe te korekcije dovoljno je samo mjerenje faznog kuta između napona i struje na ulazu ispravljača

Highly Enhanced Inductance Sensing Performance of Dual-Quartz Crystal Converter

This paper presents ways of inductance sensitivity improvement in a quartz crystal converter for low inductance measurement. To improve the converter’s sensitivity, two quartz crystals that were connected in parallel and additional capacitance connected to the two quartz crystals in the oscillator’s circuit are used. The new approach uses a converter with special switchable oscillator and multiplexer switches to compensate for the crystal’s natural temperature-frequency characteristics and any other influences, such as parasitic capacitances and parasitic inductances, which reduce them to a minimum. The experimental results demonstrate improved sensitivity and well-compensated dynamic temperature influence on the converter’s output frequency. The fundamental quartz crystal frequency-temperature characteristics in the temperature range between 0–40 °C are simultaneously compensated. Furthermore, the converter enables the measurement of the influence of its own hysteresis at different values of inductances at the selected sensitivity by parallel capacitances connected either to the single- or dual-quartz crystal unit. The results show that the converter converting inductances in the range between 85–100 μH to a frequency range between 1–150 kHz only has ±0.05 ppm frequency instability (during the temperature change between 0–40 °C), which gives the converter a resolution of 1 pH. As a result, the converter can be applied where low inductance measurement, nondestructive testing, impedance change measurement, and magnetic material properties measurement are important

Reactivation System for Proton-Exchange Membrane Fuel-Cells

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