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Forum section: electronics / beginners

author: The_Almighty_Bacon_Lord
author_rank: Contributor
timestamp: May 09, 2016, 01:15:47 am
content: Delete Delete Delete

author: Dragonfly
author_rank: Contributor
timestamp: May 09, 2016, 06:15:32 am
content: Hi there Mr. Lord.Can you describe the problem you have with the converter? I looked at your pictures and it wasn't obvious to me what it was doing wrong.

author: station240
author_rank: Unknown
timestamp: May 09, 2016, 07:04:16 am
content: I'd first start by testing the D4184 mosfet.Measure the voltage on the gate pin, and if your meter has the Hz option, the frequency.Datasheet for the mosfet herehttp://www.aosmd.com/pdfs/datasheet/AOD4184A.pdfYou could also have blown the diode, it's got two diode symbols like this >|If your multimeter has a diode check function, look up how to use it.

author: Brumby
author_rank: Unknown
timestamp: May 09, 2016, 10:03:07 am
content: This:Quote from: Dragonfly on May 09, 2016, 06:15:32 amIt would help if you could tell us what you are expecting - and what you are actually seeing.

author: sjd.aliyan
author_rank: Contributor
timestamp: May 09, 2016, 12:21:46 pm
content: What kind of problem do you have with your modules?Test the output amperage with a high wattage resistor it depends on output characteristic of your modules.

author: sjd.aliyan
author_rank: Contributor
timestamp: May 09, 2016, 03:11:24 pm
content: Quote from: The_Almighty_Bacon_Lord on May 09, 2016, 12:45:39 pmGive us a link of product or datasheet of ic or part number.Have you tried reading the datasheet for optimal input output range?

author: Marco
author_rank: Super Contributor
timestamp: May 09, 2016, 03:23:36 pm
content: Google for ltsx boost controller and you find it's likely a LTC1871 ... it has a frequency programmed by a resistor on pin 4. Unfortunately it seems to be 47 kOhm, which puts the frequency at 500 kHz. Outside of the frequency measuring range of your multimeter.Why do you mention multiple potentiometers when there is only one on the board?Just a silly question, but you did try playing with the push buttons right?

author: Brumby
author_rank: Unknown
timestamp: May 09, 2016, 03:40:46 pm
content: Does it look like this module...?... with a slightly different inductor.

author: Dragonfly
author_rank: Contributor
timestamp: May 09, 2016, 05:45:59 pm
content: Hi Bacon, I have a few questions about your reply...Quote from: The_Almighty_Bacon_Lord on May 09, 2016, 12:45:39 pmDo you mean the input voltage (from your power supply) or the boost converter's output voltage decreases?Quote from: The_Almighty_Bacon_Lord on May 09, 2016, 12:45:39 pmAssuming you mean the boost converter's output voltage stays the same... this has me confused as there is only one adjustable POT on the boost converter to set the voltage output. It's the POT in the top left corner in the picture that Brumby posted. Is that the pot you are adjusting or do you mean you are adjusting the POTs on your power supply?Other questions...Has the converter ever worked for you before? If so, then did something happen like the output was shorted or it overheated?What is the input voltage you are using and what output voltage do you want?

author: netdudeuk
author_rank: Frequent Contributor
timestamp: May 09, 2016, 10:23:29 pm
content: Is this just a case of that multiturn pot needing a really good adjustment ?

author: Dragonfly
author_rank: Contributor
timestamp: May 09, 2016, 10:59:20 pm
content: Thanks Bacon for the clarification. So the situation is you are providing an input voltage and the output voltage is always a slightly lower than the input. That is probably due to the diode's voltage drop in the boost circuit which leads me to believe the problem could be the Mosfet (the part labeled D4184). It looks like station240 provided the right advice for troubleshooting.Quote from: station240 on May 09, 2016, 07:04:16 am

author: Dragonfly
author_rank: Contributor
timestamp: May 10, 2016, 03:52:04 am
content: From what you describe I don't think it is the diode (SD1040CS) but let's eliminate that to be sure. With the board powered OFF and your meter in diode mode, measure the forward voltage drop across the diode by placing the meter's positive probe on one of the small legs (either of the outside ones, not the short stubby pin in the middle) and the meter's negative (COM) probe on the large flat part near the output connector. It should read something like 0.3V or less. Then reverse the leads of your meter (positive probe on the fat part and the negative probe on one of the short legs). You should meter should show OL or something similar to indicate an open circuit.If that passes, then check the frequency on the gate of the Mosfet again. To do that power up the boost board, put your meter in frequency mode, connect the negative probe to the "Input -" of the module (which should be the circuit's common ground) and put your positive lead on the Mosfet's gate pin. Do you read a frequency?

author: Marco
author_rank: Super Contributor
timestamp: May 10, 2016, 05:24:19 am
content: His meter might not be able to count the gate signal, I think it's ~500 kHz and the meter tops out at 400.

author: station240
author_rank: Unknown
timestamp: May 10, 2016, 07:10:23 am
content: I've got a DC-DC converter here with the same D4184A mosfet, which blew due to bad design.Also if you have the same 11.8V on the Gate and Source pins, the mosfet is blown.The gate is an isolated floating input, clearly it's gone short circuit.The switching action of the mosfet is what makes a Boost converter live up to it's name.See this diagram.

author: paulhm81
author_rank: Regular Contributor
timestamp: May 14, 2016, 06:17:53 am
content: HelloFirst of all take a look at Dave's video so you can understand how a boost converter works!and this oneYou can test the diode with you meter. Put it in diode mode and check between pins 1-2 and 3-2 both ways. Put the red probe on 1 and black on 2 and the other way around. It shoud show a voltage drop one way and nothing the other way. If it shows you a voltage drop both ways then it's bad or if it doesn't show a voltage drop in any direction it's bad again. You should really check the mosfet as it's the most probable part to have blown. If you replace the mosfet it should work if the IC that controls the gate of the mosfet isn't blown aswell. The LTC1871 (if it's what you have) is the brains of this board. It turns the mosfet on and off to step up the voltage. If the mosfet is shorted, it will deliver the input directly to the output minus the drop on the diode that you removed witch would have a voltage drop of around 200mV.It's clear that your mosfet is not working but if it's the mosfet or the ltc1871 or both is unclear.Take a look at this to check the mosfet and find it's datasheet to know what the pins are!

author: nickeevblog10
author_rank: Contributor
timestamp: November 30, 2018, 02:14:18 am
content: Thank you for posting here.I discovered the Schotty Rectifier diode is the part I wanted to test and both the op's question and the response helped me to test the diode I have.And just to report my test results too, the reading I took using my UNI-T61E in diode mode measuring what seems to be milli ohms I think, was the same both ways, the reading raced up and down and I got scared to let the reading continue. I have bought a replacement diode with the same number of pins and the same specifications to solder into the laptop power supply which I had laid aside for while.Thank you for the tutorials.I tested LT1008 MBRF10100CT