LM5017: improve LM5017 no load power comsumption

Frank Chien

Part Number: LM5017
Other Parts Discussed in Thread: LM5181, LM5180

I am Frank ,recently we have to use the LM5017 flyback constructure application (40-55V/input) to (13V/Output) and ISO 5V/5V/12V , and I measure the power comsumption is 6.1mA without iso part only 13V non-iso when there is no load

is there posible that can reduce the power comsumption in no load thougth modify the parameter component ex: Ron-Vin Resistance etc.... or change the frequency?

1. is there any wayreduce by modify?

2. if not is that any solution which TI recommand ? another flyback IC??

5 months ago

0 David Baba 5 months ago

TI__Mastermind 32260 points

Hello Frank,

Yes, you can try to reduce the switching frequency by adjusting the RON resistor. please use the design calculator to modify your design to a lower switching frequency making sure you do not violate any critical specifications.

FLYBUCK-FLYBACK-DESIGN-CALC Calculation tool | TI.com

We do also have PSR flyback regulators (LM5180, LM5181 for example) you can consider as an alternative approach, this will give better light load efficiency's as it will operating in PFM and DCM modes, as opposed to the LM5017 operating in FPWM mode which is why the light load efficiency is not ideal.

LM5181 data sheet, product information and support | TI.com

LM5180 data sheet, product information and support | TI.com

Hope this helps,

David

0 Frank Chien 5 months ago in reply to David Baba

Prodigy 40 points

Hi Thanks for reply

But it has strange thing that I used the fomula calculate the frequency and it seems low limit of frequency is about 350-360kHz

is there posible to drop the frequency under 100kHz (Rson Resistance is 1M ,1.5M but the result is same)

0 David Baba 5 months ago in reply to Frank Chien

TI__Mastermind 32260 points

the min frequency is 50kHz Frank,

So, you should be able to.

lease fill out the design calculator with your requirements so I can check your design against it.

Also need to share with me the specification of the fly-buck transformer you are suing.

Thanks.

0 Frank Chien 5 months ago in reply to David Baba

Prodigy 40 points

there is the design parameter below pic

and the fly-buck transformer is used special case for our application , the yellow lable is the resistance that I modify at this time

0 Frank Chien 5 months ago in reply to Frank Chien

Prodigy 40 points

EP13-015-S.pdf

as attachment thank you

0 David Baba 5 months ago in reply to Frank Chien

TI__Mastermind 32260 points

Hello Frank,

I see your ripple injection circuit is not right. you are using a 2.2uF Cr capacitor (C418?). Can you please fill out a design calculator with your specification, use the higher power secondary voltage and lump the other rails power consumption into the single widing to get the correct design values. follow the fly buck design calculator recommendations and retest.

Thanks.

David.

0 Frank Chien 5 months ago in reply to David Baba

Prodigy 40 points

thank David

I will try it , and reply the result , it seem a priscription for now

0 David Baba 5 months ago in reply to Frank Chien

TI__Mastermind 32260 points

Thanks Frank,

Looking forward to your response, thanks,

David.

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LM5017: improve LM5017 no load power comsumption