Can anyone check if my signals as they should be?

[stevenmahoney]

I have a power supply that I am repairing and I wanted to know if signals are as they suppose to be. here is the schematics:



And here is what I got:



Do signals look OK to you?

Steven

 

[ronsimpson]

Looks good to me.
The load must be small and/or the line voltage is high.

ron

 

[stevenmahoney]

Ron,

If under the load it should become a square, right?

Steven

 

[ronsimpson]

no,
It should never go "square wave".
It is working correctly.

 

[stevenmahoney]

Thanks, Ron.

Do you understand how this circuit works? I am a little confused with a circuitry around windings N1 and N2. What is the purpose of diodes D3, D4? Can you explain that to me?

Steven

 

[ronsimpson]

I do understand.
N1 is the primary of the transformer. It is where the power enters the transformer.
N2 is a small secondary which powers IC1.
N3 is the secondary where power is taken from the transformer.
D3, D4 take the AC from the transformer and make DC.

When T1 is on, power is stored on the transformer. No power is output at this time.
When T1 is off (for the first small part of time) the voltage on T1 is very positive, it goes above the input voltage. At this time energy goes through diodes to the secondary supplies.
The next period of time noting happens. The transformer rings slowly. This is the dead time.

 

[stevenmahoney]

Hmmm. I thought IC is powered via R6-R7.... That looks like an easier way... Why would come one add an additional winding (an complexity) just for that?

If D3 makes DC, it looks like it is stored in capacitor C10, which is only allowed to charge during one of the cycles. But what is the purpose of that? To make a cirtain conditions for the ringing on specific frequency? But then the diode does not allow the current to flow both ways...

For some reason I thought that a simple square-wave generator would suffice...

Ron, thanks for helping me! Appreciate it...

Steven

 

[ronsimpson]

The main supply is 160 volts or 320 volts (approx). To get the power for the IC from 300 volts will waste many watts.

R7 & R8 sends a small amount of power to the IC. At first the IC does not switch, It pulls very little power. C7 charges up until there is enough voltage to make the IC work. When the IC starts working it takes too much power to keep going on what little power comes from R7,8. When the IC is working, power from the transformer keeps C7 charged.

The IC (depending on which version) might start working at 12V and stop working at 7V.

"GREEN POWER" requires switching supplies to not waste power.

 

[stevenmahoney]

I see... Thank you very much!