UCC28050: Output regulation and ZCD & DRV pin to Vcc

Sakthivishnu Rangaswamy

Part Number: UCC28050
Other Parts Discussed in Thread: PMP11155, UCC28051, UCC28810, , TPS92314

Dear Team,

I would like to understand more on the below points in PMP11155 reference design, TIDRT80 schematic.

1. referring to the old thread "UCC28051: why are we pulling down ZCD pin pulse by pulse?" I understand the R21 and R22 will influence the system configuration and how far?

2. What would be the output regulation, if I use feedback without opto-coupler (instead if i use resistor network). My circuit does not need isolation.

3. What is the purpose of ZCD and DRV pin connected to Vcc circuit.

Thanks in advance.

Warm regards,

Sakthivishnu

over 3 years ago

0 Ray DiCecco over 3 years ago

TI__Genius 10835 points

Hi Sakthivishnu, I am not able to give you complete answers at this time, but I will answer as best as I can right now and get you more complete answers once I'm able to go through the schematic more thoroughly.

1. It's hard to determine how it will affect the compensation without putting together a complete model. Needless to say, you no longer have type II compensation where you need it.

2. The opto-coupler is not being used for high voltage isolation, but rather for isolating the circuitry mentioned above from affecting the type II compensation network provided by R26, C19, C20. Do you need any of this circuitry in your design (other than the type II network)?

3. I am investigating this and will get back to you.

0 Ray DiCecco over 3 years ago in reply to Ray DiCecco

TI__Genius 10835 points

Hi Sakthivishnu, I did a bit more research on this:

2. If you don't need the isolation, you can just feed the output, through a divider, back to VO_SNS and move the type II compensation to COMP.

3. This circuit is described on page 18 of the UCC28810 datasheet. (The UCC28810 is a very similar device to the UCC28050 used in this design.)

0 Sakthivishnu Rangaswamy over 3 years ago in reply to Ray DiCecco

Prodigy 50 points

Dear Ray,

Could you please share your email id for further discussion.

Referring to PM6011 I have doubt in selecting the controller based on our specification.

Kindly do the needful.

Thanks,

Sakthivishnu

0 Ray DiCecco over 3 years ago in reply to Sakthivishnu Rangaswamy

TI__Genius 10835 points

Hi Sakthivishnu,

Please first describe your power requirements (VIN, VOUT, POUT, etc) as you may be best served by a different product family within TI. I can help to align you with the correct support team. Also indicate if your solution requires AC/DC or DC/DC (or even AC/AC). I'm not sure if you're trying to power PM6011 off of the line (mains) power or off of a pre-regulated supply.

Also, I recommend you start with the following resources

Webench Power Designer: https://webench.ti.com/power-designer/

TI Power Management ICs: https://www.ti.com/power-management/overview.html

Regards,

Ray

0 Sakthivishnu Rangaswamy over 3 years ago in reply to Ray DiCecco

Prodigy 50 points

Dear Ray,

Thanks for your reply. Please find my requirement.

AC to DC flyback with PFC controller, operating voltage 90 to 300Vac, iTHD < 5%, PF > 0.95, output voltage 28Vdc, output power 48W, Efficiency >90%.

Please suggest the best product family. I have selected UCC28051 for the above requirement.

Thanks,

Sakthivishnu

0 Ray DiCecco over 3 years ago in reply to Sakthivishnu Rangaswamy

TI__Genius 10835 points

Hi Sakthivishnu,

The UCC28050 (or 51) are probably the best choices for your flyback PFC solution. A PF > 0.95 is certainly achievable, however, iTHD <5% is probably not; 10% is more reasonable.

If you are interested in a primary-side solution, TI has the TPS92314 (https://www.ti.com/lit/ug/sluua13a/sluua13a.pdf). I just wanted to give you another option.

0 Sakthivishnu Rangaswamy over 3 years ago in reply to Ray DiCecco

Prodigy 50 points

Dear Ray,

I agree, but one of the product requires iTHD <5% is there any solution for it?

Thanks,

Sakthivishnu

0 Ray DiCecco over 3 years ago in reply to Sakthivishnu Rangaswamy

TI__Genius 10835 points

Hi Sakthivishnu, I'm unable to find a generic solution so meet all of those parameters with our UCCxxxxx family of PFC devices. However, there are techniques you can use to reduce THD for your specific application. Below is a post with a solution using TI's digital controllers.

https://e2e.ti.com/blogs_/b/powerhouse/posts/how-to-reduce-pfc-harmonics-and-improve-thd-using-harmonic-injection-part-1

https://e2e.ti.com/blogs_/b/powerhouse/posts/how-to-reduce-pfc-harmonics-and-improve-thd-using-harmonic-injection-part-2

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UCC28050: Output regulation and ZCD & DRV pin to Vcc