UCC3818A: Can UCC3818 run into open loop mode

Eric Lai

Expert 4940 points

Part Number:

Hi Expert,

The engineer is asking how to run the UCC3818 into the open loop mode.

They are thinking to inject a DC level into CAOUT pin.

Then PWM width can programmed by the this DC level.

Pls advice whether this is workable or not.

Thanks

Best regards,

Eric Lai

Field Application Engineer

Texas Instruments Taiwan Limited

O: +886-2-2175-2582

M: +886-909-262-582

E-Mail:Eric.Lai @ti.com

over 3 years ago

0 Sean Xu over 3 years ago

TI__Genius 14580 points

Hi, Eric,

Yes, UCD3138A can be programmed as you described. When you use Ki =0, Kd =0, only use big Kp, DPWM duty is linearly changed with input DC voltage.

Regards,
Sean

0 Eric Lai over 3 years ago in reply to Sean Xu

TI__Expert 4940 points

Hi Sean,

Thanks for your support.

The support needed is for the UCC devices. Part Number: UCC3818A

Eric Lai

0 David Huang33 over 3 years ago in reply to Eric Lai

TI__Genius 9140 points

Hi Eric,

what is the aim to use UCC3818A for open loop? does customer need DC input voltage? if yes,

UCC3818A can also support DC input, I would suggest still use close loop.

since CAOUT is a output pin and we can not ensure the current AMP in the controller do not have any output on the CAOUT pin, there may be risk directly inject the DC on this pin.

0 Eric Lai over 3 years ago in reply to David Huang33

TI__Expert 4940 points

Hi David,

Understood.

The design is applied the UCC3818 for the DC input instead the AC input from same design.

But there is a a huge 9Hz ripple (50V) on the output.

May we have your support to look into the design.

Thanks

Eric Lai

0 David Huang33 over 3 years ago in reply to Eric Lai

TI__Genius 9140 points

Hi Eric，

since you already send the email, let us discuss it from email.

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UCC3818A: Can UCC3818 run into open loop mode