LM20343EVAL: Using LM20343 as a synchronous boost converter

Mohammad Alsmadi

Part Number: LM20343EVAL
Other Parts Discussed in Thread: LM20343, LM5170-Q1, LM5176

I am writing to inquire about the possibility of using the an evaluation board for a synchronous buck converter (Say LM20343Eval or a synchronous buck-boost toology) as a synchronous BOOST converter as follows:

At the output of LM20343Eval (the input of the boost converter) a solar PV module will be connected (taking in mind the voltage rating of the output capacitor).
The input voltage of the boost converter (solar panel voltage) will be dynamically adjusted using a voltage DAC and a resistor at the FB pin of the evaluation board.
At the Input of the LM20343Eval (The output of the boost converter) I will connect a DC electronic load operated in constant voltage mode.

Are my assumptions technically right?

over 4 years ago

0 Ethan T over 4 years ago

TI__Expert 3835 points

Hi Mohammad,

Are you using 2 LM20343 devices? Please provide block diagram and circuit design.

Regards,

Ethan

0 Mohammad Alsmadi over 4 years ago in reply to Ethan T

Intellectual 340 points

Hello Ethan,

I attached a photo showing the diagram I want to run. I need to control the solar PV voltage and to use the LM20343Eval as a synchronous boost converter (the current is reversed). I am also inquiring of any other synchronous topology, ay buck-boost. Thank you so much.

0 Ethan T over 4 years ago in reply to Mohammad Alsmadi

TI__Expert 3835 points

Hi Mohammad,

The LM20343 cannot be used as a boost converter. The output voltage must be lower than the input voltage. Sync bucks can be used in an inverting buck-boost topology but the voltage is negative (See below). Why can you not use a boost converter in this case?

http://www.ti.com/lit/an/slyt286/slyt286.pdf

Here is a few buck-boost converters. Filter by your specific needs.

http://www.ti.com/power-management/non-isolated-dc-dc-switching-regulators/buck-boost-inverting/products.html#p1129=Buck-Boost&sort=p1129;desc

Regards,

Ethan

0 Mohammad Alsmadi over 4 years ago in reply to Ethan T

Intellectual 340 points

Hi Ethan,

Thank you for your reply. I intended to use the LM20343 as a boost converter taking the voltages into account. However, my ultimate goal is to use a DC converter where I can control the solar panel voltage. Any DC converter can fir my application. For the photo I sent you, if I want to use buck-boost converter, instead, does it work? I mean if I find a synchronous buck-boost converter and connect the PV panel at its output (to control its input) while using the input of the converter as an output (as in the photo I attached earlier), is it OK?

Thank you.

0 Ethan T over 4 years ago in reply to Mohammad Alsmadi

TI__Expert 3835 points

Hi Mohammad,

I am confused on your application. Please provide an example or desired power specifications .The buck converter can adjust to any output as long as the input voltage is greater than the desired output voltage (step-down). A buck-boost converter can either step up or down to a desired output voltage.

Regards,

Ethan

0 Mohammad Alsmadi over 4 years ago in reply to Ethan T

Intellectual 340 points

Hello Ethan,

Sorry for the confusion. My main point is to verify if the synchronous topology in LM20343 or in any other synchronous buck-boost topology allow reverse current flow. If they do so, I will connect my input at the output side and my output at the input side of LM20343. Is that clear, sir?

Thank you again.

0 Ethan T over 4 years ago in reply to Mohammad Alsmadi

TI__Expert 3835 points

Hi Mohhamad,

Is this reversed respective to the LM20343? The LM20343 is not designed for reverse current flow such that it sources the input.Are you looking for bi-directional DC/DC converters?

Regards,

Ethan