0
\$\begingroup\$

enter image description hereenter image description hereAm using the tps61175 boost converter ic in a project. per the datasheet here

i noticed when i pull the EN(enable) PIN LOW and the boost converter ic turns OFF , i still read voltage at the output Vout and the voltage corresponds to my input voltage Vin.

To further elaborate, say i connect a 3v battery to Vin and pull the EN(enable) PIN HIGH for the boost converter ic to start working with a Vout of 5.1v. When i pull the EN(enable) pin low, the Vout is becomes 3v.

The first picture shows what i did to turn the circuit off completely. That approach also lead to loss of about 400mA and the output voltage broke down to 4V instead of the desired 5V.

I need help about how to make the output Vout 0v when the boost ic is OFF, thus turn the circuit of completely.

\$\endgroup\$
1

1 Answer 1

Reset to default
4
\$\begingroup\$

It's a basic limitation of boost converters.

Even if the regulator IC is disabled, there's a current path from the input, through L1 and D1, to the output.

If you want to be able to fully disconnect the output from the input, you'll need to add an additional switch to your circuit.

\$\endgroup\$
5
  • \$\begingroup\$ I noticed the Vin and Vout had a direct path through the inductor and the schottky diode so i added a BJT at the output as a switch and used the same signal i use to turn the boost converter IC ON to switch the BJT base also. It worked perfectly but when i connect a load, the output current is about some 400mA less than what i get without the BJT. I also used a MOSFET but it was the same as the BJT \$\endgroup\$
    – Banini Prince
    Commented Nov 4, 2019 at 12:19
  • \$\begingroup\$ i figured i should add the MOSFET or BJT to the Vin side instead since adding them to Vout was done after the boost IC feedback circuit and as such voltage and current losses cannot be compensated for by the feedback circuit. what is your thought on this approach @The Photon \$\endgroup\$
    – Banini Prince
    Commented Nov 4, 2019 at 12:24
  • \$\begingroup\$ Please edit your question to include this information. Also how did you drive the base/gate of the switch element, and what is your load? \$\endgroup\$
    – The Photon
    Commented Nov 4, 2019 at 14:58
  • \$\begingroup\$ @BaniniPrince, please edit your question to share the schematic showing the switch. And include details about the load (Current requirement, is it inductive or resistive, ...) \$\endgroup\$
    – The Photon
    Commented Nov 4, 2019 at 19:09
  • \$\begingroup\$ Done editing. @The Photon \$\endgroup\$
    – Banini Prince
    Commented Nov 5, 2019 at 15:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.