• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.5
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• pp.62-70
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• 2007

In this paper, the boost Power Factor Correction(PFC) technique for Direct Torque Control(DTC) of brushless DC motor drive in the constant torque region is implemented on a TMS320F2812DSP. Unlike conventional six-step PWM current control, by properly selecting the inverter voltage space vectors of the two-phase conduction mode from a simple look-up table at a predefined sampling time, the desired quasi-square wave current is obtained, therefore a much faster torque response is achieved compared to conventional current control. Furthermore, to eliminate the low-frequency torque oscillations caused by the non-ideal trapezoidal shape of the actual back-EMF waveform of the BLDC motor, a pre-stored back-EMF versus position look-up table is designed. The duty cycle of the boost converter is determined by a control algorithm based on the input voltage, output voltage which is the dc-link of the BLDC motor drive, and inductor current using average current control method with input voltage feed-forward compensation during each sampling period of the drive system. With the emergence of high-speed digital signal processors(DSPs), both PFC and simple DTC algorithms can be executed during a single sampling period of the BLDC motor drive. In the proposed method, since no PWM algorithm is required for DTC or BLDC motor drive, only one PWM output for the boost converter with 80 kHz switching frequency is used in a TMS320F2812 DSP. The validity and effectiveness of the proposed DTC of BLDC motor drive scheme with PFC are verified through the experimental results. The test results verify that the proposed PFC for DTC of BLDC motor drive improves power factor considerably from 0.77 to as close as 0.9997 with and without load conditions.

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.2
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• pp.83-89
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• 2010

In this study, we studied whether hydrogen sulfide ($H_2S$) has an effect on the pacemaker activity of interstitial cells of Cajal (ICC), in the small intestine of mice. The actions of $H_2S$ on pacemaker activity were investigated using whole-cell patch-clamp technique, intracellular $Ca^{2+}$ analysis at $30^{\circ}C$ and RT-PCR in cultured mouse intestinal ICC. Exogenously applied sodium hydrogen sulfide (NaHS), a donor of hydrogen sulfide, caused a slight tonic inward current on pacemaker activity in ICC at low concentrations (50 and $100{\mu}m$), but at high concentration ($500{\mu}m$ and 1 mM) it seemed to cause light tonic inward currents and then inhibited pacemaker amplitude and pacemaker frequency, and also an increase in the resting currents in the outward direction. Glibenclamide or other potassium channel blockers (TEA, $BaCl_2$, apamin or 4-aminopydirine) did not have an effect on NaHS-induced action in ICC. The exogenous application of carbonilcyanide p-triflouromethoxyphenylhydrazone (FCCP) and thapsigargin also inhibited the pacemaker activity of ICC as NaHS. Also, we found NaHS inhibited the spontaneous intracellular $Ca^{2+}$ ($[Ca^{2+}]_i$) oscillations in cultured ICC. In doing an RT-PCR experiment, we found that ICC enriched population lacked mRNA for both CSE and CBS, but was prominently detected in unsorted muscle. In conclusion, $H_2S$ inhibited the pacemaker activity of ICC by modulating intracellular $Ca^{2+}$. These results can serve as evidence of the physiological action of $H_2S$ as acting on the ICC in gastrointestinal (GI) motility.