Diode conduction time

The shape of the input current into the power supply is usually described as a haversine — which is simply a sine waveform offset on its vertical axis so as to make the minima of the curve coincide with the horizontal axis (t = 0). The current waveform shown in Figure 13-1 is thus a haversine — with a time period equal to the diode conduction time (during which it occurs). That means it is chopped out of a vertically offset sine wave of that time period. 

The RMS and average values of the current waveform (calculated only over the diode conduction time) are, respectively,... 

The time segments are mirrored oppositely in the ZVS family as compared to the ZCS family. The commutating diode conducts during the resonant off-period. The power switch is on between the resonant off-periods, and the power switch s current during these on-periods is the familiar current ramp from... 

Consider a diode half-wave rectifier with a filter capacitor C and a resistor R as shown in Fig. 10.21(a). When the input voltage V) is positive, the diode conducts and charges the capacitor C. When the diode moves into cutoff, the capacitor discharges through the rest of the cycle untQ the time at which V) exceeds the voltage at the capacitor. The output waveform for the rectifier with a capacitor is shown in Fig. 10.21 (b). The ripple volts e W is given by... 

During the conduction of D1 (or D2), a reverse voltage of a diode drop is appHed across 51 (or 52). This time for which the diode conducts must be greater than the turn-off time of the switch for successful operation of the circuit. 

For a PV device, the carriers created by the arriving photons are swept across the junction, and the photocurrent Ip is the carrier generation rate times the charge of the electron e = 1.6 x 10 cb). The photocurrent flows through the diode in the direction opposite to the normal diode conduction direction - it is a negative current. 

In order to improve the slope compensation circuitry that depends upon a resistor to ground all the time, I will split this resistor between the secondary winding of the current transformer and after the rectifiers. I will double the value of the two resistors (150 ohms each), so that when the diodes are conducting, the net value is the same. 

What happens if Vsw < VD In fact that is the situation in most commercial Flybacks. But note that to do a proper comparison, you have to reflect the diode drop to the primary side. And for that we have to multiply the diode drop by the turns ratio (see the equivalent Buck-Boost models of a Flyback section in my book, Switching Power Supply Design Optimization). So, for example, if the turns ratio is 20 and the diode drop is 0.6V, the effective VD we need to compare with Vsw for our time-sharing analysis is 0.6 x 20 = 12V. And that is usually greater than the (average) drop across the switch. Therefore, we tend to say that in a Flyback, decreasing D (increasing input) will worsen the total conduction loss and decrease the efficiency. But of course that never happens, because as we increase the... 

The diode laser is scanned up and down in frequency by a triangle wave, so that the scan should be linear in time and have the same rate in both directions. In the thermal accommodation coefficient experiments, the external beam heats the microsphere to a few K above room temperature and is then turned off. The diode laser is kept at fairly low power ( 7 pW) so that it does not appreciably heat the microsphere. Displacement of a WGM s throughput dip from one scan trace to the next is analyzed to find the relaxation time constant as the microsphere returns to room temperature. Results from the two scan directions are averaged to reduce error due to residual scan nonlinearity. This is done over a wide range of pressures (about four orders of magnitude). The time constant provides the measured thermal conductivity of the surrounding air, and fitting the thermal conductivity vs. pressure curve determines the thermal accommodation coefficient, as described in Sect. 5.5.2. 

The greatest disadvantage of all detector systems such as, e.g. FID, UV, diode array detection (UV-DAD), FL, refractory index (RI), light scattering detector (LSD) or conductivity, applied in combination with GC, LC or CZE, is that they only provide an electric signal at the detector. The retention time alone of standard compounds, if available, is not sufficient for a reliable identification. LC separation of surfactant-containing extracts may often result in non-reproducible retention... 

The idea of exploiting these new conducting polymers for the development of flexible diodes and junction transistors, as well as for selective field effect transistor sensors, has been proposed and experimentally confirmed, and thus we may, perhaps optimistically, look forward to a time when popular electronic devices can be based on low cost, flexible and modular polymer components. 

When the next switch in the timing sequence is turned on, it must conduct the reverse-recovery current of the diode. As in the case of dc-dc converters, the diode reverse-recovery process usually causes large current to flow, not only because reverse-recovery times can last hundreds of nanoseconds, but also because of the low-inductance power planes. Figure 3.14 shows the reverse-recovery characteristics of a silicon fast-recovery epitaxial diode (FRED) and a SiC diode. It is clear from this figure that the SiC diode is a far more capable replacement for the typical Si diode due to the lack of recovery current. 

An HPLC method for chlorogenic acids with lactones in six different commercial brands of roasted coffee was developed by Schrader et al. (143). Hydroxycinnamic acid derivatives, including mono- and di-caffeoylquinic acids, corresponding lactones, and feruloylquinic acids were extracted from coffee with methanol at 80°C for 1 h under reflux. An HPLC method using step-gradient elution with 2% aqueous acetic acid (eluent A) and ACN (eluent B) for a 75-min run time was developed. Determination was carried out by HPLC with UV detection at 324 nm, and further confirmation was conducted by HPLC-thermospray (TSP)-MS and HPLC-diode array detection. Elution order for mono-caffeoylquinic acid (CQA) was 3-CQA, 5-CQA, followed by 4-CQA, which was different from the usual elution order of mono-CQA (Fig. 17). These results indicate that it is currently not possible to predict the elution order of different reversed-phase packings due to the different selectivity (143). 

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