UCC28070 EVM & UCC25600

Hi Atul Bhakay,

Thank you for your interest in these products.

Unfortunately the information you have supplied is not sufficient to allow me to provide a useful answer.

What is the input power source? Does the 400V output need to be isolated from the input power source? What is the power level that you require? What level of output current is being drawn when the output is being reduced from 400V? Over what range of voltage does the 400V output need to be controlled? What level of efficiency do you require when the input voltage is reduced?

Best Regards

Joe Leisten

Hello Atul

I am guessing that your intention is simply to turn the EVMs on and off. Neither EVM provides an analog control of the output voltage.

If you simply want to turn the EMV output on or off from a 0V / 8V signal then I suggest the following

Both devices may be turned off by pulling their SS pin low. This is UCC25600 pin 4 and UCC28070 pin 18.

Neither EVM has a direct connection to allow you to do this so you will have to add some external circuitry and make the appropriate connections. Dont apply the 0V/8V levels directly to the chips - I would suggest an open drain MOSFET connection and use the 0/8V signal to turn the MOSFET on and off as required.

Regards
Colin

Hi Joe,
Given below are my replies - now kindly advise
What is the input power source? 230V AC, 50Hz or 60Hz , +/-10%, 10A.
- Does the 400V output need to be isolated from the input power source?  yes, 4.2KV DC dielectric
What is the power level that you require?  We need 600W max., for starting testing initially we can start with 300W to 400W
What level of output current is being drawn when the output is being reduced from 400V?  At 400V DC max. current is 1.5A, when less voltage current will reduce down.
Over what range of voltage does the 400V output need to be controlled?  +/-1V at full load condition, with less than 10V ripple., we need to control from 0 to 400V DC , w.r.t 0 to 8V control input we have from our board, steps can be adjusted should be linear.
What level of efficiency do you require when the input voltage is reduced?  70 to 80 %
Regards
Atul Bhaky

Hi Atul Bhaky,

Assuming that you want to control the output all the way down to 0V and 0A the LLC converter topology is not a good choice. The LLC converter must deliver a minimum current when working into a short circuit. Please see this document for more details of this:

• LLC Design for UCC29950

A better suggestion would be to use the phase shifted bridge converter such as LM5046. Colin Gilmor can help you with this part.

Thanks

Joe Leisten

Hello Atul Bhaky

You will probably want a PFC boost front end - at 600W you could use an interleaved CCM design based on the UCC28070 or a single phase CCM design based on the UCC28019A.
To control the output over 0 to 400V - the best choice is a phase shifted full bridge - the UCC28950 will work well at this power level and there is a 600W EVM available - see www.ti.com/.../sluu421a.pdf for some details. The output is a fixed 12V so you will need to modify it to get 0 to 400V.
The LM5046 has integrated drivers but these are limited to 100V.

Regards
Colin