LM5146: LM5146 CV-CC operation

Pankaj Misra

Part Number: LM5146
Other Parts Discussed in Thread: LMP8646, LM3102

Hi,

I have simulated LM5146 with below schematic for CV-CC operation . At 7A i am trying to enter in CC mode ,for me looks ok to me but this is with ideal OPAMP. Request the TI team if they can evaluate about the feasibility with actual component. This is 48V to 24 V converter and my application needs Constant current / limit operation after 6A (let's say at 6.5 to 7A)

If any already simulated file with LM5146 for CV-CC operation is available ,let me know.

Thanks

Pankaj Misra

over 1 year ago

0 Timothy Hegarty over 1 year ago

TI__Guru 50797 points

Hi Pankaj,

I think there's another thread on this same topic. The recommendation there was to use a current-mode controller for easier stability design relative to a voltage-mode controller. It would be interesting to plot the CC loop gain as there seems to be some ringing during the transition.

Regards,

Tim

0 Pankaj Misra over 1 year ago

Prodigy 40 points

Hi Timothy,

Any comment on upper schematic which i simulated for the CC loop.

Thanks

Pankaj

0 Pankaj Misra over 1 year ago

Prodigy 40 points

Hi Timothy,

Any comment on upper schematic which i simulated for the CC loop.

Thanks

Pankaj

0 Timothy Hegarty over 1 year ago in reply to Pankaj Misra

TI__Guru 50797 points

Hi Pankaj,

The concept seems fine. However, you need to verify stability in terms of interaction with the voltage-mode loop.

By the way, the LMP8646 is an interesting part for CC-CV as it has the amplifier and diode. Take a look at the app notes as well.

Regards,

Tim

0 Pankaj Misra over 1 year ago in reply to Timothy Hegarty

Prodigy 40 points

Hi Tim,

I have gone through doc. Actually LM3102 will not work as it is rated for 2.5A only.

0 Pankaj Misra over 1 year ago in reply to Pankaj Misra

Prodigy 40 points

Hi Tim,

Regarding LM5146, when i simulating for current limit then what i observed controller goes in hiccup mode but timing is not matching . I am operating at 255Khz then it should start after 32 mS ( (1/255kHz)* 8192 cycles) again after entering in Hiccup mode but actually it is staring after 3mS. Is my understanding not correct? is sth i am missing to understand ?

Thanks

Pankaj Misra

0 Timothy Hegarty over 1 year ago in reply to Pankaj Misra

TI__Guru 50797 points

Hi Pankaj,

I was just referencing the LMP8646 as a convenient building block for the CC-CV external circuit (the LM3102 etc. were given for reference, not for a solution here).

You are correct, the hiccup internal once OCP engages should be 8192 clock cycles. You can see that with the EVM. Not sure if the PSPICE model has an issue with that timing parameter.

Regards,

Tim

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LM5146: LM5146 CV-CC operation