Hello Everyone!
I have designed (okay okay, copied
) a current mode PSU with UCC2808 IC, from Texas. I read all the available documents (how works the current mode, current mode VS. volate mode, etcetcetc).
On the UCC2808 IC's datasheet, there's a DC/DC converter for [email protected]
I modified a little bit that circuit, to produce 2x50V @ 3A. I did this by changing the resistors neard the TL431, for higher voltage. And for the higher current limit, I changed the voltage divider near the current sense resistor. I reduced 2.8k.
But... When there's no load (just 2 1k soldered under the ouptut capacitors) the output voltage is OK. The feedback is taken from only 50V, not from 2x50V. Oh, and the "50V" is not really 50V, it's 54V, becouse I don't have 1% resistors, and I wouldn't like to use trim.pot.
When I load the regulated 54V with 100ohm, then the voltage is fine, about 54V. But when I change the load from 100ohm to 16ohm, the voltage drops to 40V. Why?
And another thing.
Sometimes the PSU is oscillating. I can hear it from the transformer (ETD49). Maybe, should I solder some bigger capacitor near the TL431, to slow down the feedback?
I attached the original schematic.
I have designed (okay okay, copied
On the UCC2808 IC's datasheet, there's a DC/DC converter for [email protected]
I modified a little bit that circuit, to produce 2x50V @ 3A. I did this by changing the resistors neard the TL431, for higher voltage. And for the higher current limit, I changed the voltage divider near the current sense resistor. I reduced 2.8k.
But... When there's no load (just 2 1k soldered under the ouptut capacitors) the output voltage is OK. The feedback is taken from only 50V, not from 2x50V. Oh, and the "50V" is not really 50V, it's 54V, becouse I don't have 1% resistors, and I wouldn't like to use trim.pot.
When I load the regulated 54V with 100ohm, then the voltage is fine, about 54V. But when I change the load from 100ohm to 16ohm, the voltage drops to 40V. Why?
And another thing.
Sometimes the PSU is oscillating. I can hear it from the transformer (ETD49). Maybe, should I solder some bigger capacitor near the TL431, to slow down the feedback?
I attached the original schematic.