I am quite interested in sine wave dimming of AC voltages.

I understand the concept on which it works but there doesnt seem to be much in the way of schematics for reference.

I have however stumbled upon this link

http://gaoweiming.blogspot.co.uk/2012/12/smart-sinewave-dimmer.html

I am a little bit stuck with whats going on with the overall scematic in Figure13.

I have marked in bold the parts i am struggling with, maybe someone can help.

This is Figure 11,

My understanding is that we have a bridge rectifier with an IGBT inside. Switching the IGBT (VF1) will give voltage at uo.

L1 and C1 is an input filter L2 and C2 are an output filter. VD1 and VC1 are for protection of the IGBT.

**How does VD1 and VC1 protect the IGBT?**

At a mains frequency of 50Hz - 60Hz what would be the ideal values for L1 and C1?

At a output frequency of 50Khz what would be the ideal values of L2 and C2 in order to filter everything except for the 50Hz to 60Hz line frequency?

At a mains frequency of 50Hz - 60Hz what would be the ideal values for L1 and C1?

At a output frequency of 50Khz what would be the ideal values of L2 and C2 in order to filter everything except for the 50Hz to 60Hz line frequency?

The document says that to allow for resistive, capacitive and inductive loads. they introduce a converter.

Figure12.

**VF2 and VF3 have been introduced here but i have no idea what they would be for to allow for resistive, capacitive and inductive loads. How would they be controlled? are they switched at the same frequency as VF1??**

The device i would like to build will need to control both resistive and inductive loads at various wattages.

The last figure, Figure 13 is the complete schematic.

Introduced here is RC1 and C3 this creates an RC output filter that is supposed to prevent LC harmonic oscillation problems.

**I assume this problem would come from L2 and C2?? Can anyone elaborate as to what will be goin on here??**

Sorry for the long post but there isnt much about this around so need a little help from someone

Thanks

**Also what would ideal values be for R1 and C1?**