5548Views37Replies
Why is my step up converter not increasing voltage and why output is a little lower than input?
My step up converter is not working ,it wont increase the voltage . I used a multi meter and the output ends up being lower than the input like for example when I connected the battery to it, the battery was at 8.40v and I checked the output and it was 8.10v . I was trying to make a DIY speaker for the first time, I am new to this.
step up converter is called a MT3608 LM2577. I got it off of aliexpress.
https://www.aliexpress.com/item/DC-DC-Adjustable-Boost-Module-2A-Boost-Plate-2A-Step-Up-Module-with-MICRO-USB-2V/32668154181.html?spm=2114.13010608.0.0.a2VAYu
The battery i used is off a battery pack .it is 8200 mah and 9v
Discussions
5 months ago
I had the same problem. Clockwise produced nothing, then I turned counter clockwise and it adjusted fine.
1 year ago
But it wont do anything when i turn the screw. nothing seems burnt
Answer 10 months ago
Yeahhhh i made the same mistake with those exact boost converters, doubt this will help you but might help someone else... Keep turning it, think the pot on the ones I got is ~100 turns for the full range.
And as for bad design, Vfb overvoltage is protected by R2 and the fact that the MT3608 refuses to make its Vout higher than 32v
1 year ago
Second thoughts, since some modules may be designed with the pot shorting clockwise, put the pot midway, and keep the input voltage below 6 volt, until the sense of the pot has been established.
Moral of the story on this one, as always, is to get and check the datasheets for all the devices in your designs.
1 year ago
The problem with most of the MT3608 and SX1308 modules is not the device, but the same flaw in the circuit design. If you look at the datasheet for these, which actually the same, you will find that the absolute maximum voltage allowed on the FB pin (feedback) is 6v.
Unfortunately, this can be easily exceeded because of the simple use of a 10k pot in the resistor divider from VOut to the FB pin. In operation FB is expected to be about 0.6V, but as the 10K pot can be reduced to zero, it can put VOut on the FB pin.
As the pot is turned (usually anticlockwise) the voltage on FB will increase, until it exceeds 0.6 volt and the device turns off. At that point the module will simply pass through the voltage from VIn to VOut via the inductor and diode.
Which means when the pot is connecting FB to VOut and VIn exceeds 6v plus a diode drop, the device will be destroyed.
Other than modifying the circuit, the best approach is to always turn the pot fully clockwise (most designs), then apply voltages and very slowly start turning anticlockwise for the required output.
1 year ago
i got the step converter that is 6a and can supply 100 watts is there any resisters i should use so I wont surge damage my components and so the volume will not lower.
1 year ago
When the booster power is greater then the amp power a resistor is not that useful and I believe the heat-sink will help the boost survive first power on..
1 year ago
Here are some fuse facts worth consideration;
A fuse is a lot slower to blow (melt sag open a circuit) then a semiconductor (tiny solid state PN junction can smolder to death)..
But then the booster has that nice metal heat sink => device to cool the Solid State PN Junction for a moment more time before junction reaching 130'C..
So it is a race between fuse and junction..
Also a 6A fuse probably will work a few seconds at 6 amps..
Yes, there are different speed fuses.. Please avoid all automotive fuses..
I show you the very fastest Fluke meter fuses I can get, but not on a Sunday so I repaired it.. See how fine the fuse wire material is compared to the readily available buss fuses..
The last is a 5A 32V fast mini buss fuse that may be able to save your booster from accidents.. I would get ten..
1 year ago
when told about the fuse do you think that an 6amp fuse could work temporarily so it wont kill the booster
1 year ago
and would that 6a converter still give that volume problem
1 year ago
the new one i bought is similar to the old but wont work because its only 2a and would be killed by the amp so ill have to wait to but that other new one then. but is there a way I can still use the new 2a one i bought or maybe with out the converter without the volume going down or with out damaging anything if not ill just wait
1 year ago
so should i try getting bigger step converter. Because the amp can go to 28 v and the new boost i orderd can go to 28v to
Answer 1 year ago
Nice find it has a maximum of output 6A..
Assume your amp is using 100W then the boost voltage out = P/A= 100/6 = 16.6 vdc...
Answer 1 year ago
If the amp can use a 100 watts then any booster must also be able to supply 100 watts...
Watts are output volts x amps and the battery more...
Example P=VxA and A=P/V
@ 28 volts Amps = 100/28= 3.6 Amps
@ 14 volts Amps = 100/14= 7.2 Amps
If 3.6A kills your Booster then 7.2A will also kill it at any loud note...
You need a power supply that limits output current to whatever it was designed to deliver...
1 year ago
would that work for when i can buy another part
1 year ago
https://www.aliexpress.com/item/100W-DC-DC-DC-3-35V-to-3-5-35V-LTC1871-Booster-step-up-Step-up/1967921037.html?spm=2114.01010208.3.2.Wtmu8t&ws_ab_test=searchweb0_0,searchweb201602_2_10152_10065_10151_10068_10130_10136_10137_10060_10138_10155_10062_10156_10154_10056_10055_10054_10059_10099_10103_10102_10096_10148_10147_10052_10053_10142_10107_10050_10051_10084_10083_10080_10082_10081_10178_10110_10111_10112_10113_10114_10181_10182_10033_10078_10079_10077_10073_10070_10123_10124-10051_10112_10033_10077,searchweb201603_1,ppcSwitch_5&btsid=05706ec8-0728-496c-8d1b-9c46fd2d2a4c&algo_expid=671bd1d8-c0e5-4bbf-9477-8224dd05ee03-0&algo_pvid=671bd1d8-c0e5-4bbf-9477-8224dd05ee03
1 year ago
whoops the amp can only go up 24 v and the step up can go supply 28 v but that still would still kill the step up is there a way i can use the step up with out killing it because i wont be able to buy something that could give more amps for a while
1 year ago
Good !
You realize the amp can try to pull 100 watts from a booster that can only deliver
14 volts at 2 amps thats only 28 watts.. No wonder anything above a whisper will blow the booster...
1 year ago
btw the amp is 2x50w each speaker is 50 watts
1 year ago
ok thank you ill i am going to do that
1 year ago
Why don't you use two batteries in series = under 18 VDC ? Give you double the time too..
But lets do the math for current... Output current over 2A max kills the unit and the efficiency is only 75% at full output... So lets work with 1.5 amps average where maybe Eff=90% >> 1.1 loss.. Put a 1.5 a fuse on the output later a 2A fuse.
Before energizing with the amplifier adjust the pot to deliver 14v You may have put some small load in order to make the booster work use an incandescent
Average Input current = 1.5Aout x (14v/8.8v) x 1.1 loss = 2.7 Amps input..
Any way, a quarter ohm resistor in series with the input will cut back 1amp input..
You make a o.25 ohm resistor by putting four one ohm 1/2 watt resistors in parallel..
Be sure to click the pic to see the whole image !
1 year ago
circuit
1 year ago
how can i stop the surge current damage
Answer 1 year ago
A resistor in series that is removed with a switch after 20 sec.
And I can't, until I know the circuit you are feeding the 14 volts to...
Fiure the R.
1 year ago
The new one I ordered is from different seller
1 year ago
14v
1 year ago
BTW I'm ordering two just to see the output..
1 year ago
What is voltage are you trying to boost up to ?
1 year ago
it bought a new one and i have another problem my diy speaker when turned on is at first loud but then the volume lowers even without the boost module
Answer 1 year ago
Sounds like you are surge current damaging your modules.
When you first generate the higher output voltage.. There is initially a 3 to 7 times current draw that could over load the unit... BTW did you first adjust the output pot without a load for the exact voltage you want ?
Then you could be draining the little battery.. Remember the battery must supply more current in proportion to the voltage increase and 93% efficiency means 7% is used to run the booster... Battery Current A = Speaker Current x (Vout/Vin) x 1.07
Answer 1 year ago
i checked without load nothing happens
1 year ago
how do i check with out load
Answer 1 year ago
Simply remove the out wires and put a volt meter on the output and try the pot again..
Answer 1 year ago
It wont do anything
Answer 1 year ago
I wont do anything
1 year ago
What happens when you turn the pot one way or another ?
Answer 1 year ago
nothing
Answer 1 year ago
niether decrease or increase
1 year ago
When i bought it. it said boost
1 year ago
Did you check that it's a step down (buck) vs. step up (boost)?
Did you check with load or without load?
Are there any burnt components - could you have ruined it?
Is your multimeter working properly?
Buy another one!
Answer 1 year ago
Wow...... Good advice Yonatan,
Can I assume that you can read schematic drawings now ?
Answer 1 year ago
Nope. Nothing has changed since then.
#1 - because I was lazy to read Chinglish.
#2 - tip that I know from checking regular power supplies
#3 - from experience (hint: wrong polarity and... BOOM! :)
#4 - also from experience (messing up an expensive multimeter so it shows that an 18650 battery is 20V :)