Impedance Matching
A buck converter can be used to maximize the power transfer through the use of impedance matching. An application of this is in a "maximum power point tracker" commonly used in photovoltaic systems.
By the equation for electric power:
where:
- Vo is the output voltage
- Io is the output current
- η is the power efficiency (ranging from 0 to 1)
- Vi is the input voltage
- Ii is the input current
By Ohm's Law:
where:
- Zo is the output impedance
- Zi is the input impedance
Substituting these expressions for Io and Ii into the power equation yields:
As was previously shown for the continuous mode, (where IL > 0):
where:
- D is the duty cycle
Substituting this equation for Vo into the previous equation, yields:
which reduces to:
and finally:
This shows that it is possible to adjust the impedance ratio by adjusting the duty cycle. This is particularly useful in applications where the impedance(s) are dynamically changing.
Read more about this topic: Buck Converter