Adding a Current Limit Feature to a Buck/Boost Converter

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Introduction: Adding a Current Limit Feature to a Buck/Boost Converter

About: Awesome Electronics Tutorials, Projects and How To´s

In this project we will have a closer look at a common buck/boost converter and create a small, additional circuit that adds a current limit feature to it. With it, the buck/boost converter can be used just like a variable lab bench power supply. Let's get started!

Step 1: Watch the Video!

The video gives you all information you need to recreate the circuit. In the next steps though, I will present you some additional information.

Step 2: Order Your Components!

Here you can find a parts list with example seller (affiliate links):

Aliexpress:

1x Buck/Boost Converter: https://s.click.aliexpress.com/e/_dTevK0K

1x LF33 Voltage Regulator: https://s.click.aliexpress.com/e/_dT0fKCw

1x 10nF Capacitor: https://s.click.aliexpress.com/e/_dU4FEsB

1x 10µF Capacitor: https://s.click.aliexpress.com/e/_d7dOwRz

1x 0.1Ω Current shunt: https://s.click.aliexpress.com/e/_dSyQdMA

2x 3.3kΩ, 2x 100kΩ Resistor: https://s.click.aliexpress.com/e/_dTPpXjt

1x MCP602 OpAmp: https://s.click.aliexpress.com/e/_dTvJRGw

1x 10kΩ Trimmer: https://s.click.aliexpress.com/e/_dTFyPv5

1x UF4007 Diode: https://s.click.aliexpress.com/e/_dYR45Bh

1x Voltage/Current Meter: https://s.click.aliexpress.com/e/_d8lymHM

Ebay:

1x Buck/Boost Converter: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x LF33 Voltage Regulator: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 10nF Capacitor: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 10µF Capacitor: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 0.1Ω Current shunt: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

2x 3.3kΩ, 2x 100kΩ Resistor: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x MCP602 OpAmp: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 10kΩ Trimmer: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x UF4007 Diode: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x Voltage/Current Meter: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

Amazon.de:

1x Buck/Boost Converter: http://amzn.to/2w1WgTz

1x LF33 Voltage Regulator: http://amzn.to/2w1f2dF

1x 10nF Capacitor: http://amzn.to/2xIowip

1x 10µF Capacitor: http://amzn.to/2habIql

1x 0.1Ω Current shunt: http://amzn.to/2haAOWd

2x 3.3kΩ, 2x 100kΩ Resistor: http://amzn.to/2w2jSaI

1x MCP602 OpAmp: http://amzn.to/2x61uBr

1x 10kΩ Trimmer: http://amzn.to/2x9NmVc

1x UF4007 Diode: http://amzn.to/2w2vzxU

1x Voltage/Current Meter: http://amzn.to/2xJ2YCt

Step 3: Create the Circuit!

Here you can find the schematic and pictures of my completed circuit. Use it as a reference to create your own.

A rather tricky part is the current path on the output side of the converter. If you want to hook up the current shunt and the V/I meter then your wiring should be like this: Out+ -->Load+ -->Load- --> Red Wire I Meter --> Black Wire I Meter --> Current Shunt 1 --> Current Shunt 2 --> Out-

Step 4: Success!

You did it! You just added a current limit feature to your Buck/Boost converter!


Feel free to check out my YouTube channel for more awesome projects:

http://www.youtube.com/user/greatscottlab

You can also follow me on Facebook, Twitter and Google+ for news about upcoming projects and behind the scenes information:

https://twitter.com/GreatScottLab
https://www.facebook.com/greatscottlab

6 People Made This Project!

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26 Comments

0
DrEmmanuelGold1
DrEmmanuelGold1

Question 8 months ago

Does the current limit not oscillate?
I think the gain is way too big.

0
adriangalazka15
adriangalazka15

Question 11 months ago

Hello I want do the power suply to charging li-on 6s max voltage on 1 s 4.0V I want do current limit 1A this project on Xl6019 is good

20210124_095857.jpg
0
duinodude
duinodude

Reply 1 year ago

;)

0
ОнС
ОнС

1 year ago


Hi . On MT3608 worked?

0
DanRiches
DanRiches

Answer 1 year ago

Hiya,

I have the exact same module and it works if you connect the 1N4007 diode to pin 5 of the XL6009. You must use a MCP602 though. I tried various TL08x variants and it did nothing but pulse like a stroboscope.

Dan

0
protoham
protoham

2 years ago

Nice video, just wanted to point out your schematic in the video is wrong, you connected pin 3 of your opamp to ground, but the schematic below is correct. Good work!

0
vgregorio
vgregorio

4 years ago

Is it possible to replace the MCP602 with an LM358? thank you!

0
AllexandruP
AllexandruP

Reply 4 years ago

both are op-amp,s so, it-s ok parameters are the same .at me worked

0
prabhatk13
prabhatk13

Reply 2 years ago

It will work maybe but you should mcp602 as it is a rail to rail op amp while lm358 is a normal one so your voltage may not reach to full .

0
azad6
azad6

Question 3 years ago

can I add this to a boost converter?

0
Relaf
Relaf

Question 3 years ago

Whats the maximum current passing through the circuit? How can i make this but in 10 amps version?

0
aggelos.loykatos
aggelos.loykatos

4 years ago

Excellent work! Would it be possible to replace the LM2587 Buck-Boost converter, with one using the XL6009 IC? (of course, using the correct feedback pin). Because the LM2587 ones seem to have gotten either hard to find, or quite pricey. Would any changes be necessary to the current limit circuit?

0
DIY Circuits
DIY Circuits

4 years ago

Out of curiosity, is there an LM equivalent of this op amp, and if not a complete equivalent then at least something that would do the job?

0
PirateKittyK
PirateKittyK

Reply 4 years ago

The ubiquitous LM358 is used in most Chinese modules. Cheap as dirt too.

0
Polymorph
Polymorph

Reply 4 years ago

The ones I have with LM358 current limiting use low side shunt resistance. Which means you absolutely cannot use more than one in a circuit, as you cannot tie the grounds together.

I'm not sure an LM358 will work as intended in this with high side shunt resistance. It is certainly worth a try, but keep in mind that it is a very old op amp. Although it can work in a rather low voltage circuit, the output is limited to 1.5V below V+. So 3.3V is rather low.

0
PirateKittyK
PirateKittyK

Reply 4 years ago

Of course it works. Its configured as a differential amplifier.

Just because a part has been around for many years, doesn't mean its bad!

Max Vout = Vsupply - 1.5V

Min Vout= 20mV

its not a problem with +5 Volts supply. Its not a rail-to-rail op amp.

0
Polymorph
Polymorph

Reply 4 years ago

I didn't say it won't work, I said it might not work.

The circuit as configured is running from 3.3V. The differential amp has a gain of about 30. At 1A, that is 0.1V x 30 = 3V. Right there, the output of IC1a cannot go above about 1.8V.

The output of IC1b is meant to drive the sense line of the buck regulator high, so the regulator will lower the output thinking it is too high. But with a max of 1.8V output and a 0.6V drop across D1, it is only about 1.2V maximum. Possibly worse, as fast recovery diodes sometimes drop a bit more voltage than the garden variety silicon rectifier diodes. Many regulators use 1.25V as the reference voltage and so the Sense line is at 1.25V already.

If you raise the Op Amp supply voltage to 5V, it might work. And replace D1 with a shottky diode.

But it isn't as simple as just looking at the specs and saying it will work. You need to consider operation of the circuit. It certainly could work with changes to the circuit, both have about the same offset voltage and Vcc requirements. It is the output range where the LM358 has an issue with this circuit.

The MCP602 isn't really that expensive. The eBay link the author gives is only $4 for 5 with shipping, about 80 cents each.

Correction: I see a problem with this circuit as designed, for either IC. The common mode input range for the MCP602 is V+ - 1.2V, and for the LM358 is V+ - 1.5V. So the Op Amp really needs a supply voltage higher than 12V, or the circuit redesigned. Right now the common mode voltage with 12V on the current shunt is 12 x 100k/(100k + 3.3k) = 11.6V