How to generate positive power from negative input

Sunny Qin

Other Parts Discussed in Thread: TPS61170

Hi team,

Do we have any power solution that can generate positive power from negative input, for example, the input is -12V, the output is 5V, current requirement is 0.2A, I know that isolated power can meet that, but that`s too complex for customer, so I am wonder if we has simple non isolated solution.

Thanks.

Regards, Sunny

over 4 years ago

0 Ruby Li over 4 years ago

TI__Expert 7520 points

Hi Sunny

Sorry, our team do not have the solution with negative input.

Best regards

Ruby

0 Zhao Ma over 4 years ago

TI__Genius 15135 points

Hi, Sunny

From the topology, it looks the boost converter can achieve your application.

Suggest you contact BOOST product line to confirm.

0 Jasper Li over 4 years ago

TI__Mastermind 46905 points

Hi Sunny,

refer to this application note https://www.ti.com/lit/an/snva740/snva740.pdf for the operating principle for this application. replace the IC to TPS61170 and reduce the output capacitor.

0 Sunny Qin over 4 years ago in reply to Jasper Li

TI__Expert 4890 points

Hi Jasper,

That`s very good solution, thanks very much.

Regards, Sunny

0 Zhao Ma over 4 years ago in reply to Jasper Li

TI__Genius 15135 points

Hi, Jasper

What is the benefit of Q1 and Q2?

I see the description: "The advantage of using two transistors in this design is that the base-emitter diode voltage can be mostly nullified and the output can be more accurate. "

Why will Vout be more accurate?

is it okay to use resistor divider?

0 Jasper Li over 4 years ago in reply to Zhao Ma

TI__Mastermind 46905 points

Hi Zhao Ma,

the Q1 and Q2 act as level shifter to sense the output voltage because the GND pin of the device is now -12V.

the resistor divider doesn't work unless the -12V input is very stable, for example only +-1% variation

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How to generate positive power from negative input