Electronic – Input/Output Impedance of DC/DC converters and Impedance matching

dc/dc converterimpedance-matchinginput-impedancemppt

I am interested in understanding how do DC/DC converters achieve impedance matching for maximum power transfer applications. After visiting this entry, you can see in the "impedance matching" paragraph some calculations that lead to D=sqrt(η*Z_out/Z_in). What I would like to make clear is what exactly do we mean by input/output impedance, what the above Z_out,Z_in are supposed to represent, and how can I achieve impedance matching with the source, when based on the above equation, by changing the duty cycle I can merely change the ratio of the converter's impedances.

Best Answer

What I would like to make clear is what exactly do we mean by input/output impedance, what the above Z_out,Z_in are supposed to represent

  • \$Z_o\$ is the external impedance connected to the buck converter's output.
  • \$Z_i\$ is the impedance presented by the buck converts input to the power source.

how can I achieve impedance matching with the source, when based on the above equation, by changing the duty cycle I can merely change the ratio of the converter's impedances

The impedance seen by the source is the impedance presented by the buck converter, \$Z_i\$ and, in turn, that presented impedance is dependent on \$Z_o\$ and the duty cycle used by the buck converter.

In other words, the input impedance presented to the power source by the buck converter loaded with \$Z_o\$ is: -

$$Z_i =\dfrac{ηZ_0}{D^2}$$