LM5177: Element selection for wide output volatges.

Piotr Sobieraj

Part Number: LM5177

Tool/software:

Good morning,

Can LM5177 operate in a large range of output voltages?
If so, how should the system elements be selected:

Inductor
Resistor
Compensation network

The Excel provided by Ti does not have the ability to set the output voltage range, only one specific value, and the webench changes the values of the coil, current measuring resistor and compensation system with each change of the output voltage.

The designed system should have an input voltage of 24V and an output from 0 to 60V, with a maximum power of 60W. The maximum current is 5A.

I tried a few combinationa, but I always had problems with stability.

over 1 year ago

0 Stefan Schauer over 1 year ago

TI__Guru 58641 points

Hi Piotr,

yes, the LM5177 can work in a wide range.

Of course tuning get more complicated and requires some iteration loop. The Quickstart Calculator is here the best tool.

How does the output power scale with the output voltage?

Is the current limited to 5 A over the full range?

Best regards,

Stefan

0 Piotr Sobieraj over 1 year ago in reply to Stefan Schauer

Prodigy 10 points

Hello Stefan,

Yes the current is limited to 5A at all range, but above 12V max power will limit the output current - so for e.g. at 60V output voltage, max current will be 1 A. Could you please help with selecting example components?

Other question is about inductor ripple current. What is the optimal value that I should aim for?

In our situation, low inductance provide stability but also big losses. When we increase inductor to 47uH inductor heating get smaller, but after attaching constant current load with set current of 100mA we get instability.