For marine applications I have to design a 20 pieces 12V 10 W -each, LED lights supply fed by 12V on-board battery, driven by engine alternator and each LED have to take 12V and 900mA am rather sure in CC mode. The super-lamp will stay on ship stern to see the nighttime port entrance for several hundred meters away.
Ideas:
1) to buy everything SMPS mode from China. Somehow less costy 2 USD*20 pcs is not detrimental but confusing is that 12V input means 10.5V output and no options. Feel bad. Most costy about 5 USD/piece anyway have the same defect.
2) to construct the low=loss mosfet or igbt driven by TL431 or simple bjt. Implications are in-acceptable large voltage loss on current measure resistor. If even Ge bjt is used with 0.3V, then adding 0.1-0.2V on FET I get only 10...11 V on the LED what is too much low for 12V device.
3) Order the bunch of ZXCT1109 with 50-100 mV voltage loss on resistor, where the output moves bjt BE, and it moves above-mentioned FET, for example IRLZ44. Problem is that I never touched with that ZXCT monitor and project have drastically small money. So, any mistake is detrimental. Would any tell do this my idea is worth to claim be good??
4) step-up converter plus step-down converter (or SEPIC) in constant current regime, but it seems bit too complicated, no, hardly too complicated.
5) to spit over shoulder and plug `em straight on the ship 12 V battery with individual small say 0.2 Ohm resistor each. Wonder is it helpful enough for not burn if engine ocassionally is on not off. Okay, sub-version is add to those 20 resistors the collectivized resistor by relay if engine works, but I just dislike such bad prost-ness.
6) Look for some unknown possible PTC thermo-resistor at that value and current, wonder if such ever exist.
7) connect LED brutally parallel but I am sure for 99% very fast they will burn off.
8) to step-up 12V to 240V and switch all serially CC mode, for example by FET bufferized 34063. Yet my experience with LET series at 220V tells the life will be rather short and will end with abnormal braightness for short moment and then complete dark.

So, Your ideas are very welcome for low budget circuitry solutions.

 

Wow that's 18Amps @200W , that's going to take some battery power, or is this just one per battery?

I would use an led driver chip ready made as you said like these..


https://m.aliexpress.com/item/40008...l8pUIbxqvFsScY1603299047561&browser_id=&is_c=

 

[QUOTE="Dodgydave, I would use an led driver chip ready made as you said like these..
https://m.aliexpress
Ther is one thing bothering me, the 12V DC input case means maximum output 11V for that where the LED demand no less than 12V. Thus, it will not be operartional, perhaps.

 

RE:""that's going to take some battery power, or is this just one per battery?""
The lamp is needed for short, probably 5 minutes or 10 minutes, or 20 minutes use when in carbon black wall named Night covers the poorly illuminated small-port where only green and red couple of eyes can be seen on entrance and all anything other is completely invisible. Use other light source shows nothing, its well checked with rather strong handheld light on batteries, just the blind emptyness is seen what who knows, probably after 10 meter will end with the shark-like underwater stones-field Booom! or anything even more terrible. Light must be like train-style main lights have to do, illuminate everything like a daylight kilometers and kilometers afar and 100 A*h battery have enough power to give those 20 Amps for several minutes long.

 

Search for the best output current, it won't give you 12V out from a 12V supply but it will maintain the current.

https://m.aliexpress.com/item/32965...3a386e49b784b462c7fE.jpg_640x640Q90.jpg_.webp

 

OK, China post somehow was working flashlikely so now the 5 minutes as I am keeping those LEDs at the hand. Pushed that to the aluminium sheet for cooling, swithed to the CC lab source, adjusted 0.75A and read 10.48V. Thus means the 12V advertized are "Chinese Volts" where 1.0 European Volt is 1.1 Chinese Volt. This case it works on my behalf, step-down only is well pardonable solution. Problem solved.

 

RE:""that's going to take some battery power, or is this just one per battery?""
The lamp is needed for short, probably 5 minutes or 10 minutes, or 20 minutes use when in carbon black wall named Night covers the poorly illuminated small-port where only green and red couple of eyes can be seen on entrance and all anything other is completely invisible. Use other light source shows nothing, its well checked with rather strong handheld light on batteries, just the blind emptyness is seen what who knows, probably after 10 meter will end with the shark-like underwater stones-field Booom! or anything even more terrible. Light must be like train-style main lights have to do, illuminate everything like a daylight kilometers and kilometers afar and 100 A*h battery have enough power to give those 20 Amps for several minutes long.

What are you describing? Is it fog? Or a black hole?

 

Night covers the poorly illuminated small-port

just the blind emptyness is seen what who knows, probably after 10 meter will end with the shark-like underwater stones-field

Thought that was the job of port pilots, to know where the problems are and steer the ship in safely.
https://en.wikipedia.org/wiki/Maritime_pilot Are you sure your not getting yourself into doing something for a smuggler?

 

Thought that was the job of port pilots, to know where the problems are and steer the ship in safely.
https://en.wikipedia.org/wiki/Maritime_pilot Are you sure your not getting yourself into doing something for a smuggler?

If a smuggler is ever mistaken for a lighthouse, he might not be a very good smuggler.

 

read 10.48V. Thus means the 12V advertized are "Chinese Volts" where 1.0 European Volt is 1.1 Chinese Volt.

If you had a real data sheet you could see that the voltage is not accurate. It changes from batch to batch.

 

Because the battery voltage and the LED voltage are close:
1) boost-buck, (there are many kinds)
2) Boost only; Stack two LED to get 24V or 20.96V LEDs.
3) ?
Many of the CC PWMs have a feed back voltage of 0.1 to 0.3 volts to reduce the loss. (do not use a TL431 at 2.5V)

 

Shortbus: I myself am not any smuggler, be sure (but probably is worth to let the try??but the port lights where my yacht is staying are very poorly illuminated, daylight at autumn period is very short, thus the coming back in damn dark is everyweek practice. If the moon then something may be seen, if moon is small or clouds then full blindness. But what to want from fisherman village port far in the countryside 140 km off my liveplace where only stays 10 yachts and 5 about the same size fisherman boats. Yet I like that port, as it is much cheaper than at Riga and is crucially near to entrance in "big sea" as we call place where Gulf neck into Baltic. Thus if to float to Sweden it stays day travel nearer to the target and 140 km by car is one hour with the tail. Anyway - because of first snow the season was ended this year and boat stays now on coast until next spring. So the light-source project may wait a January when Chineeses will forward already ordered buck-boost packet with 20 pieces inside.
Ronsimpson: So, its right, buckboost was a best solution. If to think about strong boost factor and string of leds, as higher are boost factor as larger have to be energy loss. And energy efficiency here is critical very much, the battery is only like it is and cannoyt be much expanded.