Looking at some power supply circuits, I've noticed different types of smoothing circuits after the diode bridge.
Some include just include a series inductor with the load resistance
Others a shunt/parallel capacitor with the load resistance.
And other include a LC filter with the load resistance.
I understand the operation of the 2nd order LC filter to block out higher frequency harmonics. I understand the derivation of the transfer function for the filter aswell.
My confusion comes from the qualitative explanations I've read online, that state the inductor smoothens current ripples and the capacitor smoothens voltage ripples. Can someone explain why those explanations are used? Isnt the capacitor providing both current and voltage smoothing?
Below I've typed out my though process and where my confusion lies.
What doesnt make sense is that current is a function of voltage, so by smoothing the voltage across the load we should also be smoothing the current. For example, if we used a shunt capactior for smoothing the voltage across the load then it should also smooth the current through the load since I=V/R.
I tried thinking about this in the frequency domain to no avail.
Mathematically, we know the voltage across the capacitor in frequency domain is V=(1/wC)*I . From that we see that higher voltages dropped across the capacitor (and therefor the parallel load) for lower frequencys/harmonics which is our voltage smoothing action. But we can re order the equation such that I=V*wC in which case we see that I (the current shunted/bypassed through the capacitor) is larger for higher frequencies. So larger magnitudes of current are bypassed though the cap away from the parallel load for higher harmonics, thus also providing current smoothing for the load.
Some include just include a series inductor with the load resistance
Others a shunt/parallel capacitor with the load resistance.
And other include a LC filter with the load resistance.
I understand the operation of the 2nd order LC filter to block out higher frequency harmonics. I understand the derivation of the transfer function for the filter aswell.
My confusion comes from the qualitative explanations I've read online, that state the inductor smoothens current ripples and the capacitor smoothens voltage ripples. Can someone explain why those explanations are used? Isnt the capacitor providing both current and voltage smoothing?
Below I've typed out my though process and where my confusion lies.
What doesnt make sense is that current is a function of voltage, so by smoothing the voltage across the load we should also be smoothing the current. For example, if we used a shunt capactior for smoothing the voltage across the load then it should also smooth the current through the load since I=V/R.
I tried thinking about this in the frequency domain to no avail.
Mathematically, we know the voltage across the capacitor in frequency domain is V=(1/wC)*I . From that we see that higher voltages dropped across the capacitor (and therefor the parallel load) for lower frequencys/harmonics which is our voltage smoothing action. But we can re order the equation such that I=V*wC in which case we see that I (the current shunted/bypassed through the capacitor) is larger for higher frequencies. So larger magnitudes of current are bypassed though the cap away from the parallel load for higher harmonics, thus also providing current smoothing for the load.