Recommendation for 48V-to-24V, 25A PWM

PA Nilsson

Other Parts Discussed in Thread: LM5145, LM5143-Q1, LM5143

I have a design where I need to supply power to a high load PWM-like device.

Input is 45-50V, output is 24V.

The load is a pure resistive load that can vary between 1-1000 ohms, and is pulsed with a period of approximately 1ms, with a duty cycle of max 65%.

The load can vary from one pulse to another between the extremes (1-1000 ohms).

The target is an industrial application with long life time support needed, so long life components are needed.

Any recommendations?

/PA

over 5 years ago

0 Ed Walker over 5 years ago

Prodigy 5 points

Hello PA, thank you for posting to the Forum.

Does your design need isolation?
I ask because this could be done with a 2 phase synchronous buck, 48V to 24V and 2 180 degree phases would provide input and output ripple cancellation.

However the buck does not provide isolation from input to output.

Otherwise an Active Clamp Forward or a Phase Shift Full Bridge can provide safety isolation.

I look forward to your reply.

0 PA Nilsson over 5 years ago in reply to Ed Walker

Prodigy 200 points

Hi,

No, this output will not require isolation.

/PA

0 PA Nilsson over 5 years ago in reply to PA Nilsson

Prodigy 200 points

I have been looking at LM5145, any comments on using this part?

/PA

0 Timothy Hegarty over 5 years ago in reply to PA Nilsson

TI__Guru 62327 points

Hi PA,

You can also consider the LM5143-Q1 two-phase synchronous buck controller. There is a quickstart calculator available by download from the product folder to assist with component selection, power loss analysis, etc.

Regards,

Tim

0 PA Nilsson over 5 years ago in reply to Timothy Hegarty

Prodigy 200 points

What would be the key advantage for LM5143 in this case?

/PA

0 Timothy Hegarty over 5 years ago in reply to PA Nilsson

TI__Guru 62327 points

Hi PA,

The two-phase solution at 12.5A/phase provides accurate current sharing between phases and good thermal spreading in the PCB to avoid component hotspots. Also, ripple current cancellation at the input and output is achieved.

25A is high for one phase (even if the load is pulsed), particularly if the ambient temperature is high.

Regards,

Tim

0 PA Nilsson over 5 years ago in reply to Timothy Hegarty

Prodigy 200 points

I also need an additional separate 24V rail, with around 3A output.

I see that LM5143 have the possibility to have two outputs, are there any limitations to the second channel when the above is applied?

/PA

0 Marshall_Beck over 5 years ago in reply to PA Nilsson

TI__Mastermind 35180 points

We are working on this. Sorry for the delay.

0 Timothy Hegarty over 5 years ago in reply to PA Nilsson

TI__Guru 62327 points

Hi PA,

Yes, you can use the LM5143 to create a dual output configuration. However, the main output is quite high current so two phases are preferable for this.

As an alternative, you can consider a separate controller solution for the 24V/3A output, e.g. LM5145.

Regards,

Tim

0 PA Nilsson over 5 years ago in reply to Timothy Hegarty

Prodigy 200 points

Ok, thanks I will look into the dual phase mode.

/PA

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Recommendation for 48V-to-24V, 25A PWM