Step up voltage regulator that can handle 30V, 1A output

Thread Starter

metiz

Joined Oct 27, 2014
54
I'm building a stupid flashlight with a 30Watt LED chip. I plan to use 6 18650 cells, 3 in series and then two clusters of those in parallel, so the input voltage I have to work with is between about 9 and 11V. Is there a (cheap) step-up voltage regulator that I can buy that can handle 30V, ~1A output at those input voltages? Everything I've found so far is either too expensive, non descriptive or of questionable Chinese quality.
 
Last edited:

ronsimpson

Joined Oct 7, 2019
1,020
Everything ......... is too expensive, non descriptive or of questionable Chinese quality
That is the way it works. too expensive, non descriptive AND of questionable Chinese quality
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boost LED driver cc
Type: LED Drive Board
Size: 48mm x 38.5mm x 18mm
Input voltage: DC 5V - 32V
Output voltage: 26V - 36V
Output current: 900mA ± 5%
Conversion efficiency: 93% max
This is a constant current boost power supply. It will force 900mA through your LED. LEDs run on current not voltage. That is why you need a "cc" power supply.
1602211663244.png
 

Thread Starter

metiz

Joined Oct 27, 2014
54
That is the way it works. too expensive, non descriptive AND of questionable Chinese quality
----------------------------------------------------
boost LED driver cc

This is a constant current boost power supply. It will force 900mA through your LED. LEDs run on current not voltage. That is why you need a "cc" power supply.
View attachment 219094
Thanks for the circuit. Am I right in assuming that D1 is just for polarity protection? If so, I'll leave that out (cost cutting)
 

ronsimpson

Joined Oct 7, 2019
1,020
Am I right in assuming that D1 is just for polarity protection?
No! I think you should get the cheap Chinese board and use it as an example to build more if you want.
data sheet
Inside the IC there is a MOSFET switch from pin 3 to 1. About 150000 times a second the switch closes. This puts L1 across Vin. Current builds up in L1. Energy is stored in L1. When the switch opens up the stored energy wants to go somewhere (up). The point "SW" pushed up above VIN and charges Cout up to a voltage above Vin.

LEDs do not like running on a constant voltage. They like constant current. In this case the voltage on Cout will be about 30V but not exactly. Current flows through the LEDs to ground. RS is like a current meter shunt. When the voltage across RS reaches 0.22 volts the desired LED current is reached and the IC holds the current there.
1602245889681.png
 

Papabravo

Joined Feb 24, 2006
14,688
Thanks for the circuit. Am I right in assuming that D1 is just for polarity protection? If so, I'll leave that out (cost cutting)
Your question betrays a lack of knowledge on this type of circuit. Good luck getting a functional layout. Good luck troubleshooting it when things go wrong.
I think you need to buy one first even if it does not end up working for you. At least you will have some experience working with this kind of circuit, and can study the layout and component selection.
 

Thread Starter

metiz

Joined Oct 27, 2014
54
Your question betrays a lack of knowledge on this type of circuit. Good luck getting a functional layout. Good luck troubleshooting it when things go wrong.
I think you need to buy one first even if it does not end up working for you. At least you will have some experience working with this kind of circuit, and can study the layout and component selection.
Well, you're not wrong unfortunately. Never been that good with electronics. Regardless, ronsimpson's circuit looks easy enough to build so I'm gonna give it a try. I have a 2nd, crappy led chip I can test it with. I think that if I let out the blue smoke, I'll learn more from that than just buying an off the shelf circuit.
 

Thread Starter

metiz

Joined Oct 27, 2014
54
I ended up buying a off the shelf board. Way cheaper than getting the components myself as it turns out. When testing this board with a lab power supply, I found that it doesn't like low voltages. it barely works at the rated minimum voltage, and it won't reach 30V output when it does. My original idea was to put three batteries in series, and then put two clusters of those in parallel. I now think it might be a better idea to wire them all up in series, to get a voltage between 18 and 22V.
 

Ian0

Joined Aug 7, 2020
750
I now think it might be a better idea to wire them all up in series, to get a voltage between 18 and 22V.
There's a lot more choice for step-down regulators than step-up; and there are plenty of buck regulators specially designed for LED driving. Wise choice.
 

Thread Starter

metiz

Joined Oct 27, 2014
54
The flashlight is pretty much done. As an afterthought, I soldered in a charging port for each of the batteries (can't really get them out of the enclosure now). So, time for the idiot-check. I'm 99% sure I can do this, but just to be absolutely sure: when I have 6 batteries wired in series, but open-loop, can I hook up a battery charger designed for one cell to, for example, battery nr 2? I've attached a picture to clarify. the lowest voltage source is supposed to be the charger. The resistor is just to prevent the simulator going crazy.ggg.png
 

Alec_t

Joined Sep 17, 2013
11,744
For safety, you really should have a BMS (battery management system) for those cells, to ensure no cell gets charged above its maximum safe voltage or discharged below its minimum safe voltage. Lithium cells are unforgiving and can catch fire or explode if abused.
 

Thread Starter

metiz

Joined Oct 27, 2014
54
For safety, you really should have a BMS (battery management system) for those cells, to ensure no cell gets charged above its maximum safe voltage or discharged below its minimum safe voltage. Lithium cells are unforgiving and can catch fire or explode if abused.
I am aware. I'm using a charging circuit from a small power bank with a single 18650 battery, which incidentally is identical to the cells I'm using. The circuit above was just to clarify things. I never intended to just hook up the batteries to a voltage source.
 

Thread Starter

metiz

Joined Oct 27, 2014
54
For safety, you really should have a BMS (battery management system) for those cells, to ensure no cell gets charged above its maximum safe voltage or discharged below its minimum safe voltage. Lithium cells are unforgiving and can catch fire or explode if abused.
I am aware. I'm using a charging circuit from a small power bank with a single 18650 battery, which incidentally is identical to the cells I'm using. The circuit above was just to clarify things. I never intended to just hook up the batteries to a voltage source.

I plan to use the below circuit to warn me for low voltage. The 1.2k resistor can be tweaked to get the LED to turn on below a certain level.undervoltage circuit.png
 
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