Boost topology

In a Boost topology, there are no edges of inductor current waveform at the input. That is because there is an inductor present in series with the input, which helps level any current variations. So though a certain (small) amount of bulk capacitance is still required to smooth out the slowly undulating inductor current further, in principle, high-frequency... 

There is something puzzling about the statements above in case you haven t noticed How are we concluding that a decrease in D causes an increase in the inductor current So far we have been led to believe that in a Buck-Boost or Boost topology, the inductor current equals 70/(l - D), which implies that the inductor current goes up as D increases, not decreases ... 

Figure 12-3 A Check of the Results Obtained from an Online Tool for the Boost Topology...

July 2001 We need to convert 9-14V DC to a 12V regulated output. Normally, one would use a flyback topology to achieve this. However, we would rather try to use a Boost topology with parallel 12V zener clamp diodes (for simplicity). The switcher simulations... 

What follows is what you should really know about the Boost and Buck-Boost topologies themselves. 

In fact, this is our very first switching topology — the buck-boost topology. 

The above two observations make the buck-boost topology the only pure flyback topology around, in the sense that all the energy transferred from the input to the output, must have been previously stored in the inductor. No other topology shares this unique property. 

In Figure 1-16 we have presented the schematic of the boost topology. The direct and the freewheeling paths are indicated therein. In Figure 1-17, we have the corresponding analysis, including the key waveforms. 

Let us analyze the boost topology in terms of the voltseconds in steady state. We have... 

Note that, although the design procedure may be seen to specifically address only the buck topology, the accompanying annotations clearly indicate how a particular step or equation may need to change if the procedure were being carried out for a boost or a buck-boost topology. 

Therefore, for the boost topology, if Io is greater than this value, we will always remain in CCM, no matter how high we increase the input voltage. 

V to —30 V would need a negative boost. These are the two configurations of a boost topology. 

Answer Just as the isolated flyback is a derivative of the buck-boost topology, the forward converter is the isolated version (or derivative) of the buck topology. It too uses a transformer (and optocoupler) for providing the required isolation in high-voltage applications. Whereas the flyback is typically suited for output powers of about 75 W or less, the forward converter can go much higher. 

Answer We should first be clear that the boost and buck-boost topologies are so similar in nature, that any IC meant for a boost topology can also be used for a buck-boost application, and vice versa. Therefore, such control ICs are generally marketed as being for both boost and buck-boost applications. 

Note also, that a proper ON/OFF function cannot be implemented on a boost topology (as is). For that, an additional series transistor is required, to completely and effectively disconnect the output from the input. 

The name given this zero is the RHP zero , as indicated earlier — to distinguish it from the well-behaved (conventional) left-half-plane zero. For the boost topology, its location can be found by setting the numerator of the transfer function above to zero, that is, s x (L/R) = 1. So the frequency location of the boost RHP zero is... 

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