Using AMC7135 based driver off of 12V supplies

[djQUAN]

Datasheet says no, I say yes.. by just adding two components

Based on the AMC driver datasheet, it can only accept voltages of up to 7V max. Running it on 12V will surely blow the IC apart.

I have a use for this: COB LED strip from DX powered off the solar 12V system in my house so I need to run it off 12VDC.

Since running it to its max rated 1320mA produces a great deal of heat, I found from previous LED lamp builds that underdriving these results to minimal reduction of light output but increases its efficiency and less heat to dissipate but still bright enough for my intended uses.

Since its measured Vf is only 11.3V, I decided a low dropout linear driver will work well especially with a 12V supply. A drive current of 700mA is about right from testing.

This is the circuit I made to run an AMC7135 at 12V (expect the actual used two AMC drivers in parallel for 700mA).

The IC will be dropping only about 1V from a 12V supply so heat should be minimal.

Parts used: AMC7135 and LED star with inbuilt AMC driver from FT, COB LED from DX

I mounted the AMC chips on the LED star as it was convenient (rather than etching my own PCB) and acts a good heatsink for the chips since it's an alu core PCB. I didn't have a 5V zener on hand so I used two green LEDs in series for a Vf of about 4V for the AMC chips.

Here's a test setup mounted on an aluminum angle bar.

At 12V, we get a little over 700mA.

Highest I've tested is at 14V though it will never go that high in my application since the battery voltage drops at night (no solar power). Keep in mind the AMC chips are dropping about 5V at that input voltage so it is not recommended unless heavily heatsinked.

Here's the final version. The capacitor is 2.2uF 25V. It is necessary as the wiring inductance triggers the protection circuit of the AMC chip and prevents it from working properly. I also made a 350mA version for dad's room as he uses it for a night light.

 

[BShanahan14rulz]

Good post! AMC7135 is very useful, and there are a few tricks out there for bringing down the V+ of the driver. One is to use another LED to drop the supply voltage.

+1 for the capacitor, this is often forgotten with larger builds, but is mentioned in some versions of the datasheet.

 

[djQUAN]

Yes, it shows with enough voltage (and some guts) you could power a green (or any high Vf diode with enough current capability) with this.

I made a 350mA version for dad's night light but ended up taking it out and putting back the previous one as it was still too bright haha. Used it in the kitchen instead. Makes me feel good for buying 100pcs of the AMC chips. I see a lot of uses in the future with these.

 

[benmwv]

The amc chips are very useful! I have a roll of them too. Great little chips, If only they came in more current options.

 

[LarryDFW]

They do have two 7135 current versions:

350 ma

& 380 ma.

LarryDFW

 

[AnthoT]

Yup AMC's are great! You get amazing battery life when powering a red

 

[djQUAN]

I actually had a need of about 450-500mA so another current version of around that much or a 200-250mA version (to use 2 in parallel) would be nice

I had a recoil light with a direct drive PCB (and an annoying strobe mode) so I took out the driver and made my own driver using three AMC chips to make it single mode regulated 1050mA. Worked perfectly.