Tool/software:
Hello everyone,
I am trying to test UCC24630 with a flyback operating with UCC38C40 on the primary side. It is a SMPS with a DC input voltage from 60V to 400 V and an output voltage equal to 12V/4A (UCC38C40 plus UCC24630) and 5V/1A (TPS 563208). My circuit schematic is in the comments bellow.
Resistor R27 was changed to 788k7, so the pin 1 (VPC) voltage is above the enable voltage (0.45V). I also used a 20 kΩ in R24 (time blanking resistor). R28 (gate-driver resistor) is a 50 Ω resistor.
I am following some component values in this reference design:
The SMPS is not working appropriately, because the voltage VREF is not in the appropriate range (4.9V - 5.1V according to UCC38C40 datasheet). It can be seen in the picture bellow in the channel 2 (green):
Here is another picture showing the voltage in the feedback pin of the UCC38C40:
I also got some results with UCC24630 that I’d like to show you guys, and maybe somebody could help me with this synchronous rectifier using ucc24630.
Here is the input voltage (ch. 1 - yellow), output voltage (ch.4 - red), VPC voltage (ch. 3 - blue), driver (ch. 2 – green):
Here is the input voltage (ch. 1 - yellow), output voltage (ch.4 - red), VSC voltage (ch. 3 - blue), driver (ch. 2 – green):
Here is the input voltage (ch. 1 - yellow), output voltage (ch.4 - red), VDD voltage (ch. 3 - blue), driver (ch. 2 – green):
Here is the input voltage (ch. 1 - yellow), output voltage (ch.4 - red) and the voltage on the third pin TBLK (ch. 3 - blue), driver (ch. 2 – green):
Any comments or suggetions regarding both ICs (UCC38C40 and UCC24630) would be of great help.
Thanks in advance.
Henrique.
I'll try to send the images here:
- Flyback topology:
- UCC38C40:
- UCC 24630:
Please let me know if it is clear.
Thank you.
