UCC256304: CC CV control for super capacitor charging

No this controller does not have this feature.

Then which controller do you suggest.

These below can do CV CC:

UCC28700 /01 /02 /03 /04

UCC28710 /11

UCC28730

UCC28740,

UCC28742

UCC28630 /31 /32 /33 /34

I think you didn't get my question properly.

UCC256304  Will be used as primary control and feedback path CC CV control will be added. Similar to  the attached schematics.

Since UCC256304 is LLC resonant controller when the output capacitor is discharged will it be able to supply constant current at very low voltage down to 1 V for example.

No, this controller does not have a constant current feature.

UCC256304   is LLC controller not flyback.        

Which LLC half bridge controller has constant current feature.

We do not have an LLC controller that can do CC.

I am not looking for integrated LLC controller with current control.

It's generic question can we put addition control in feedback path similar to attached picture for CC and CV control.

Similar to this please follow the link.  TIDA-010038.

 Is there any contact number available to discuss this issue. I think you are unable to understand my question.

Ok, let me find another support to see if we have a solution. 

Ok, I've forwarded your question to Ben who will provide support to you.

Hi Arunava,

It is possible to do a LLC design with CC-CV control using UCC256304. There are a couple items I think would be good to note.

1. If CC control down to 1V is needed, I think an auxiliary flyback of some sort will be necessary to provide bias power to both the LLC controller on the primary side as well as for the secondary side CC-CV feedback loop. 1V output would be too small for the error amplifiers on the secondary side to be properly biased directly from the output voltage. 

2. Could you share the total output voltage range for your super cap charger? For LLC, the efficiency gets worse the further away from resonance you operate. For a CC-CV type output where a wide operating range is necessary, you essentially need to "pick your poison" so to speak and select which operating points will have less than optimal efficiency. For most LLC designs I have seen using CC-CV control, the maximum output power tends to be selected as the point at which the converter operates at resonance. 

Any device in the UCC25630x or new UCC25640x LLC controller families would be able to do a half bridge LLC with CV-CC control. If you could share more information about your design spec, I think we would be better able to advise you on a suitable topology choice.

Best Regards,

Ben Lough

Hi Ben,

Thank you for your response.

We are intending to use UCC25640x. Along with microcontroller from TI which can send reference for CC CV control.

Input voltage range is 40-60V.

Capacitor voltage  would be from totally discharge capacitor 1V - 15.5V DC . Capacitor charging current would be around 20 A.

If we supply IHVHIGH pin of UCC256304: 12.6 mA

Can we use RVCC to supply power to microcontroller.

Regards

Arunava

Hi Ben,

Any update on the above questions.

Could you send us contact details and email so I can send you more details.

Could you please also supply UCC25640x / UCC2530X spice model for simulation so we can simulate this our design.

Hi Arunava,

Apologies for the late response. Based on the input and output voltage ranges, I think either a two switch forward or active clamp forward would be better suited for this design. LLC is achieves good efficiency from ZVS but it does have circulating current that does not contribute to the power transfer. This tradeoff is advantageous at high input voltage such as a PFC output or rectified AC. At lower input voltage, the circulating current needed to regulate would be higher and lead to more conduction loss. The wide output voltage range would also be problematic for LLC. 

ACForward is another soft switching topology but does not have the circulating current or wide operating range issues that LLC would see in this design. I think this would be a better topology choice for your application.

My email is ben.lough@ti.com. Please feel free to reach out.

Best Regards,

Ben Lough