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Implementation Using a Multiplier
It is possible to use a multiplier for boost converter also. Using equation
(8), an expression for the duty cycle can be obtained to be:
The above equation is valid if the conduction is continuous. The above equation
can be realized using a multiplier and a few opamps as shown in Fig. 11. It
needs to be mentioned that components should be chosen suitably, reflecting
the required scaling. For example, if the multiplier yields an output of 10
V when both its inputs are at 10 V, an input of 10 V should correspond to
the maximum input voltage. If the maximum duty cycle is set to be 0.9 and
it corresponds to 9 V, then an input of 9 V to the opamp in the feedback path
should correspond to the maximum desired output voltage. In this case, the
ramp signal with which the output of this circuit is compared should rise
from 0 V to 10 V in one cycle period. Based on this scaling scheme, a value
of unity in Fig. 10 corresponds to 10 V. Instead of using Vo, a
reference signal proportional to desired output is used in Fig.11.
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