Duty cycle driver

Circuits where isolated gate drives operate at nearly full duty cycle or nearly zero duty cycle can be difficult to design. The transformer that provides isolation can easily saturate at full duty cycles. The circuit featured here uses a unique idea in order to circumvent this difficulty. 

In order to fully test the capabilities of this circuit, the input pulse was varied in duty cycle from 5% to 95%. The voltage source VIN used the following two statements  

Fast switching circuits like this one can cause simulation problems. Discontinuities can create time step too small errors. In order to aid in convergence, the following statement was added to each of the simulators. 

This circuit was also constructed in IsSpice, PSpice, and Micro-Cap. The resulting waveforms are shown in Figs. 9.14, 9.15, and 9.16, respectively. 

Advantages Isolated driver, nearly infinite duty cycle range, very low delay, not frequency limited 

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MOSFET driver output (totem-pole) 50 percent duty cycle limiting... 

Selecting the SMPS controller IC. The important factors within this application that affect the choice of switching power supply controller IC are MOSFET driver needed (totem-pole driver), single-ended output, 50 percent duty cycle limit desired, and current-mode control desired. The popular industry choice that meets these needs is the UC3845B. 

The advantage of AMOLED over PMOLED displays arises because emission in a passive matrix occurs one line at a time, so each OLED element operates at high peak currents and low duty-cycle. The duty-cycle in a PMOLED display is approximately equal to the inverse of the number of rows. For example, in an SXGA (1280 X 1024) display, the duty cycle is approximately 0.1%. The peak current of an OLED pixel may be 1 mA or more. High OLED currents lead to reduced power efficiency and operational lifetime and also place greater demands on the current capacity of the row driver circuits, which may have to handle currents of hundreds of miUiamperes on each output (although not simultaneously). 

The issue of carbon corrosion has received considerable attention in recent years. There are several drivers for this (1) the cost drivers for commercialization require the use of high performance catalysts with less durable carbon catalyst supports, (2) the need for system simplification and low cost prevents additional control systems to be implemented to avoid the carbon corrosion conditions, and (3) the use of the fuel cells subjected to "real world" conditions as opposed to carefully controlled demonstration projects, with very dynamic duty cycles and many start-up/shutdown cycles. This increased attention has resulted in new or improved measurement techniques and several studies and reviews on the high cathode potential and associated carbon corrosion mechanism [39,40,48-51]. 

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