Controlled junction

Deep levels influence a variety of device parameters. For example, in minority carrier devices they influence the recombination and generation lifetimes. The lifetime in turn controls junction currents and refresh times in dynamic random access memories. For this reason we discuss lifetimes. Defects... 

In order to account for the abstraction of ideal, no power consuming switching in a bond graph with invariant causalities that holds for all system modes, Umarikar extended 0- and 1-junctions by allowing for more than one bond to impose an effort on a 0-junction and more than one bond imposing a flow on a 1-junction with the constraint that only one of the causality imposing bonds is active at a time instant [12, 13], These extensions are called switched power junctions and are not to be confused with controlled junctions to be referred to subsequently. Figure 2.2 illustrates the idea. 

As early as 1974, Thoma introduced the concept of time dependent junctions [24] in order to switch off and on connections between power ports. Mosterman picked up this idea and introduced controlled Junctions [21], In contrast to switched power junctions, a local control algorithm associated with a controlled junction switches off all adjacent bonds of a controlled junction when a switching device considered as an ideal switch turns off and re-activates all bonds when the switch is closed. That is, an ideal switch in ON-mode is represented by a standard 0- or 1-junction. In OFF-mode the junction is replaced by a source of value zero as shown in Fig. 2.10. 

Switching devices, e.g. semiconductor switches in power electronic systems that are explicitly represented by a component model can be more easily identified in a bond graph in comparison to a representation that accounts for switches by controlled junctions. An initial not simplified bond graph is more close to a system schematic (cf. Chap. 4, Figs.4.2 and 4.3). 

In comparison to the BG in Fig.4.2, the BG in Fig.4.3 reproduced from [9] does not reflect the series connection of a resistor and a semiconductor switch. The latter one is not explicitly visible in the BG. Additional information must be known that junction I3 is a controlled junction. Moreover, detectors are not in inverted causality although sensors deliver a measured and thus known variable into a DBG. Also note that an auxiliary resistor R Rs2 is needed to determine the effort at junction O4. 

The previous section considers a simple DC to DC boost converter with two switches controlled by two complementary signals. The healthy boost converter thus may be in one of two feasible modes. Reference [18] studies switch faults in a simple single phase half-bridge inverter. In [17], bond graph-based FDI is applied to a single phase H-bridge inverter. Both works represent switches by means of controlled junctions, i.e. use hybrid bond graphs. 

A thyristor rectifier uses four silicon semiconductors of alternating types in a pack. Figure 8.7 shows that without some outside influence the three junctions can not simultaneously be conductive. When the cathode side is negative, two junctions are conductive, but the center, or control, junction is not. Applying a current pulse to the interior P-layer neutralizes the bias in that layer and allows current to flow through the rectifier pack. 

Trajfic Advisory Leaflet 2/03 Signal-control Junctions on High-speed... 

Overall, there was no clear evidence of a difference in pedestrian casualty risk at stand-alone crossings and signal-controlled junctions. 

The wider use of pedestrian stages at signal-controlled junctions should increase pedestrian convenience and reduce pedestrian—vehicle conflicts. 

Advanced stop lines (ASLs) can significantly improve safety for cyclists at signal-controlled junctions. 

Tap fitted with flow control junction Brick chips... 

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