UC1825: UC1825J Power output

Hi ,

Yes thank you, I have made some adjustments. I have changed the load resistor to 4.66 ohms for 6A current. Since this is one to one how do I adjust the turns ratio? I have changed the diodes to 40V rating. How do I change the current rating for T1 and T2

Stan

Hi,

thanks, yes got the turns ratio set to 1.0 and am getting 26V. One more question how can I add the test points for OUT_A, OUT_B, ILM, etc to transient plot? I see two curves on the graph which is labeled ads Output. One shows the output going to 25.99V the other is unlabeled

Stan

Hi, 

When I add meters these do not show up on the transient graph nor do any of the test points that are already present. I just get a single noname graph with only the output shown when I run the transient analysis. Every pass a new graph TR1, TR2, etc. For some reason I cannot cut and paste the snip into this thread

Stan

6470.slum653 (1).tsc

HI ,

Yes that works. I was changing the transformer to match our configuration and now am getting a Convergence ERROR on SD1, the first diode. I restored the transformer configuration back to the example, but I am still getting the same Convergence Error. What causes this?

thanks'

Stan

5482.slum653 (1).tsc

3681.slum653 (1).tscHi,

I have configured the transformers to match our design and the output drops to zero. the transformer turns ratio is now 5:8 . Can you take a look?

thanks

Stan

Hi,

Here is our existing design, which we are having problems with excessive noise causing the FPGA PLL to become unlocked and the shutdown circuit requires 5 seconds to respond.

thanks

Hi,

Here is the latest schematic , which matches our circuit. I have adjusted the turns ratio and set C4.7384.slum653 (1).tsc The output is still zero.

thanks

Stan

Hi,

I just opened your schematic , but the transformers are not configured as our current design. Open the design I just sent and see the transformers. the Dots are reversed and one FET drives the top and one the bottom. What do you think?

thanks

Stan

Hi,

I have updated your schematic (i have renamed _H2) and attached with the current transformer configuration on our circuit. The output is zero. 

thanks

Stanslum653_h2.TSC

Hi See the screenshot the dots are reversed and the center two pins are grounded. and Vout < 0.2v

thanks

This is how our current circuit card is laid out unless there is an error in the schematic. As we are having problems with noise and when the Shut down is applied from the FPGA, the 28V does not shut down for 5 seconds. I am working remote and will not be in the office for another few days to  make measurements. I would think that the present circuit and simulation should match reasonably well. Here is our current configuration. And H2 matches this. 

Hi,

I tried reversing the dots, and keeping the middle two pins on the right side ground and the middle two pins on the left side tied to +28V and the output stays at mV. Perhaps there is something unique about this transformer?

Hi,

This is a custom transformer and is just like the schematic. A dual core with 5:8 turns ratio.. We may be getting a distorted waveform out. But connecting the Ideal transformers in this manner shows that this will not work. I can modify the board to match the connections form the original UC1825 schematic which does provide a +28V output and take measurements. Any recommendations? 

thank you for all of your support!

regards

Stan

Hi, Here is a bigger picture showing all of the T1 connections, Out A and Out B drive the push-pull bipolars

thanks

The T1 in the screenshot is a combination of TR1 and TR2 in the TINA simulation