lamp dimmer with pi filter

[gjo]

I am looking at a lamp dimmer circuit. It has an rc pi filter used to trigger a diac. I want to know why and when does the first capacitor discharge into second capacitor. The second question is how does the first capacitor fully discharge.

 

[barry]

1) Why does the first cap discharge into the second? Because it's voltage is higher.
2) When does the first cap discharge into the second? When it's voltage is higher (after the second cap starts to discharge)
3) What makes you think the cap DOES fully discharge?

 

[gjo]

I thought the first capacitor would discharge when the AC voltage is on it's decline.and does the second capacitor discharge when it's voltage is equal with first cap or at the discs breakage voltage.

 

[barry]

a schematic might help....

 

[Venkadesh_M]

Hi assume both capacitors parallel and no inductance, so both capacitors charge at same time but introducing inductance the second capacitor wont charge much faster it is to limit or filter the surge and to trigger the Triac...