As requested. Please post your asc file, so that we can all sing from the same hymn-sheet.

This is the file with it not working.

If you give D1 and C2 seperate grounds , it works.

Take a look a post up where i posted the working and none working version with the arrows pointing to the ground connection showing it not working in one and then working in another

 

hi mike,
The way you have drawn the wire link from the diode to the capacitor it is not connected at the C2 point
Also, you need the K1 L1 L2 1 on the circuit.

I don't have your Schottky diode, it is an equivalent.

Try this asc file
E

 

hi mike,
The way you have drawn the wire link from the diode to the capacitor it is not connected at the C2 point
Also, you need the K1 L1 L2 1 on the circuit.

I don't have your Schottky diode, it is an equivalent.

Try this asc file
E
View attachment 301738

I dont understand what you mean K1 L1 L2 1
I dont know what that means? I have those L1 and L2 parts in place?

 

hi mike,
The two inductors are mutually coupled when using K1 L1 L2 1
The '1' indicates the coupling is 100%, or say 0.5 =50%.

Its in the LTS Help files

Did mjy asc file work OK?

E

 

hi mike,
The two inductors are mutually coupled when using K1 L1 L2 1
The '1' indicates the coupling is 100%, or say 0.5 =50%.

Its in the LTS Help files

Did mjy asc file work OK?

E

Thanks, mine works but yours works better.

I dont understand the mututal inductance thing. These are two inductors in series. If you go buy the recommended part from digi key from the data sheet its

DRQ74-330
https://www.digikey.com/en/products...7312?s=N4IgTCBcDaIAQBEBKBFA7AFgLQGYcAYQBdAXyA

This is not a transformer its two inductors. So why am i specifying mutual inductance in the sim?

 

Thanks, mine works but yours works better.

I dont understand the mututal inductance thing. These are two inductors in series. If you go buy the recommended part from digi key from the data sheet its

DRQ74-330
https://www.digikey.com/en/products...7312?s=N4IgTCBcDaIAQBEBKBFA7AFgLQGYcAYQBdAXyA

This is not a transformer its two inductors. So why am i specifying mutual inductance in the sim?

ok guess i screwed up
Looking at that part again, it is a little transformer
So this is what makes it a flyback, the isolation.

Is there a way to negate the isolation if you dont need it?
Or could you help me pick an easier part to deal with?
I dont need flyback but i need a little converter like this that i can generate -12V from

 

hi mike.
The two inductors are wound on the same core, like a transformer.
E

 

They don't specify the mutual coupling between the two windings, but it is likely very similar to a standard transformers of that size.

 

Is there a way to negate the isolation if you dont need it?

hi,
The Voltage Input and Outputs are not isolated.
What is your design requirement.?
E

 

hi,
The Voltage Input and Outputs are not isolated.
What is your design requirement.?
E

I dont have a design isolation requirement. I just need something that will generate a -12V rail with as little as 5V input.
~50mA current at -12V
But i dont want to get into flybacks and magnetics if i can help it.

 

hi mike,
Check out these links for 'Fesz' when using LTS
E
https://www.youtube.com/results?search_query=fesz+electronics+sepic

 

The circuit shown is a Čuk converter. It will work with two separate inductors or with coupled inductors. It works best with inductors that are badly coupled, such as two windings each occupying 180° of a toroid, with K about 0.9

 

Any other automotive grade parts that i can use that will give me a negative voltage you all can think of?

 

I think that the MC34063 can manage a negative output, but it won't beat a Čuk converter for ripple.

 

Thank you all