A friends GF is a doctor, I’m trying to build her a disinfection box as she will be reusing masks.
Here is what I am working with
Power Supply Driver Transformer 100W 110V AC to 12V DC
DROK Adjustable Buck Converter Step Down Voltage Regulator 6V-32V 30V 24V 12V to 1.5-32V 5V 5A LCD Power Supply Volt Reducer Transformer Module Board
4x GermGuardian UV-C 10.5v 4W .38A
So… the problem I’m having is the bulbs are only drawing .16A and barely powering it on. I cant crank it up any more voltage as I’m limited to 11.9V on the DROK and increasing amps stops at .16A, if I go lower, voltage drops. The drok itself is support to output 5A. What am I doing wrong and how can I get the power the bulbs need to operate at their recommended power requirements?
Saw bulbs of that type recently in AliExpress. I think the problem lies in that these bulbs sort of work like leds, with their Vf being a lot higher when cold. Since your supply can not output more than 12 V, you cannot make the bulbs heat enough. You need to feed the buck module with way higher voltage, as the bulbs need a lot more voltage at startup. The buck module must operate in constant current mode, or the bulbs will blow up. You'll need one driver per bulb, too, or set some current limiting resistors with the bulbs if in parallel because no way the current will be shared with balance. Or a module with a lot higher output voltage and bulbs in series.
Great feedback, I’ll have to source items on amazon because time is short with spread down here. So if I change the power supply to a variable voltage dc supply, get a buck converter that can do constant current and add current limiting resistors to + to the bulbs, that should get them going?
Edit: manufacturer of the bulb said it needs 25v to start and 11v to operate so you are correct that it has a higher vf. Ordered an adjustable voltage power supply.
One is using mains AC, some guys were speaking about 4 - 4.5 µF capacitors in series with 220 V AC to power up those 3 W bulbs on the AliExpress ads I posted above. These are 4 W, and you're using 115 - 120 V AC, so maybe a 10 µF capacitor will do. The capacitor must be non-polarized, ceramic or film type, and its voltage rating must be at least 200 V, as 120 V AC mains peaks at ≈170 V. This is a bit of a guesswork from my side, so you may want to wait for some other people's input here.
Other solution is DC. If you need from amazon:
Without changing your currently limited voltage output power supply of 12 V DC, get buck boost modules to power each bulb for peace of mind. This and that could do (they're pricey there). A single module could also do with all bulbs in parallel and some resistors in series. A 4.7 Ω resistor in series with each bulb, for example, should be more than enough to limit any unbalanced inrush current to the bulbs as they'll heat up in parallel. But if any bulb fails, the rest will have to bear with the failed one's current share (!).
Changing the power supply to a 24 V one (with at least 3 A rating), some models here with adjustable output voltage. Then, using a CC/CV buck module for each bulb like these XL4015 units.
The led driver solution would also work fine, but as with the above modules and supplies getting them from your mainland doesn't looks as cheap as directly from China.
Any DC/DC converters should be adjusted to the bulbs rated current (≈0.38 A) using their constant current trimpots, with sufficiently high no-load output voltage. The converters, as your flashlight led drivers do, adjust the output voltage to keep a steady current to the bulbs.