Hi everybody

if we want to design an LC series network as a matching network to get maximum power transfer from a power supply when Rl(load) > Rs(internal resistance of the power supply)

we enter Rs in our calculations or not???

i wanna know if we want to design a LC network any where in a circuit we must take care of all the capacitor and inductance and resistor before the network or just we care of the input voltage only!!!??

please help me
thank you

 

Please note that, the LC matching network is designed to match the load resistance RL to the series resistance Rs. For this particular network, the design equation should look like RL=Rs(1+Q^2); Q=RL/(w0*L). In general, if there are some parasitic inductances or capacitances already present in the circuit, you need to take them into account in your design.

 

i want to know we take Rs + Rl as the resistance in the RLC network or only Rl

 

Please elaborate more. What do you mean by "resistance in the RLC network" ?

 

we have two patterns for R,L,C network
series & parallel standard patterns
that for make calculation easier
so for any either pattern or configuration of R,L,C we convert it to series or parallel standard pattern or combined series & parallel standard patterns
so we must have in the end one R , one L, one C
so my question is that we take Rs + Rl to represent the Resistance in the series pattern standard

 

This could be reduced to a series RLC, with R=2*Rs @ w=1/sqrt(LC)

 

so Rs in our calculation to define the response of the circuit RLC

 

so Rs in our calculation to define the response of the circuit RLC

The transformation to the series form (regardless of whether you are considering a high pass or a low pass match) ignores Rs and considers only the load Rl.

 

Yes, after transforming the parallel R-L combination to a series R-L, the network will resemble a series RLC having an effective loss resistance equal to Rs in series with the transformed RL, which at w=1/sqrt(LC) will equal to Rs.

 

Yes, after transforming the parallel R-L combination to a series R-L, the network will resemble a series RLC having an effective loss resistance equal to Rs in series with the transformed RL, which at w=1/sqrt(LC) will equal to Rs.

The resonance condition at match won't be governed by that simple relationship with L & C being the actual circuit elements. Replace L with L' in that equation and you would be correct.

 

Replace L with L' in that equation and you would be correct.

Since for a high Q system, value of the inductance remains unchanged after the series to parallel transformation, I didnt add mention it explicitly. But yes to speak without loss of generality, L will change to L'=L(1+Q^2)/Q^2.

 

Depends on the values one is trying to match. For instance if Rl=100 ohms and Rs=50 ohms then Q is 1.