LM5145-Q1: Is series operation possible?

Hideaki Douguchi

Prodigy 10 points

Part Number: LM5145-Q1
Other Parts Discussed in Thread: LM5145,

Tool/software:

Hello support teams.

I would like to operate converters that use LM5145 in series.

Is series operation possible with LM5145?

I am concerned that if there is a difference in start-up times between the two converters, the overcurrent protection will be activated and one side will be unable to start up.

Please let me know if any countermeasures are necessary.

Best regards.

4 months ago

0 Taru Kapoor 4 months ago

TI__Genius 11845 points

Hi Hideaki,

Some designs do have DC/DC converters working in Parallel:

But I am not sure what you mean by operating them in series. Can you please elaborate?

Can you share what your system specs are?

Thanks,

Best Regards,

Taru

0 Hideaki Douguchi 4 months ago in reply to Taru Kapoor

Prodigy 10 points

Thank you for your reply.

It refers to connecting the outputs of two power supplies directly and operating them as shown below.

DC/DC1 and DC/DC2 each incorporate an LM5145-Q1.

Best Regards,

Hideaki

0 Taru Kapoor 4 months ago in reply to Hideaki Douguchi

TI__Genius 11845 points

Hi Hideaki,

Can you share the values of Vin and Vout? What is the current you want to supply?

Thanks,

Best Regards,

Taru

0 Hideaki Douguchi 4 months ago in reply to Taru Kapoor

Prodigy 10 points

Hi Taru,

There are two Vout patterns.

　Pattern 1: 12V 6.4A

　Pattern 2: 15V 5.5A

Vin is 30V on both.

Thanks,

Best Regards,

Hideaki

0 Taru Kapoor 4 months ago in reply to Hideaki Douguchi

TI__Genius 11845 points

Hi Hideaki,

Thanks for the reply.

So, if I understand correctly - you want to give a 12V and a 24V output from a 30V Vin (Pattern 1) and a 15V and a 30V output from a 30V Vin (Pattern 2).

Right?

Furthermore, I am not really convinced why you want to go ahead with this approach - there are much simpler topologies that can address your circuit needs.

Can you help me understand your reasoning behind this implementation?

Thanks,

Best Regards,

Taru

0 Hideaki Douguchi 4 months ago in reply to Taru Kapoor

Prodigy 10 points

Hi Taru,

Thanks for the reply.

We are currently developing an isolated dual-output power supply as shown in Figure 1.

It is an isolated two-output type, but some users would like to use it as a ±12V/±15V power supply as shown in Figure 2,

so I would like to know if it is possible to operate it in series.

If it is a non-isolated type, there is an easy way to output ±12V/±15V,

but we would like to have one model that can handle both.

(We want to keep the number of models as small as possible.)

Thanks,

Best Regards,

Hideaki

0 Taru Kapoor 4 months ago in reply to Hideaki Douguchi

TI__Genius 11845 points

Hi Hideaki,

If the GNDs to the two inputs of the DC/DCs are isolated (Which you can ensure via separate windings from the transformer) - then Yes - I don't see any problems with your implementation.

Thanks,

Best Regards,

Taru

0 Hideaki Douguchi 4 months ago in reply to Taru Kapoor

Prodigy 10 points

Hi Taru,

Thanks for the reply.

I'll check it out on a prototype.

Best Regards,

Hideaki

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LM5145-Q1: Is series operation possible?