Changing the voltage of a boost driver

blacklightning · 2024-01-08T02:27:37.337Z

Hi All,

Looking to put an emitter in that can take up to 8v/2a (Yingfeng HYF90E42N660AG-D9A) in a M21b, and would like to eventually upgrade from a Convoy 6v boost driver to a Hank driver that can provide the full wattage.

I think I can get 8v/2a by reducing a 12v boost to 8v (per the calculations from m4potofu on reddit here):

TopR = BotR * ( Voutavg - VFB ) / VFB

Where VFB = 1 and Voutavg is roughly the average VF of the LED, so ~6V for a 6V LED.

If I use VFB = 1 (not sure if this is a constant), Vout = 8v, and BotR = 10 ohm, I get 10*(8-1)= 70 ohms.

Is this the best way to dial in a specific voltage for my application? And will the driver still output 2 amps?

raccoon · 2024-01-08T02:29:12.405Z

You’re going to love it here, blacklightning!

thefreeman · 2024-01-08T04:15:32.518Z

Welcome to BLF,

blacklightning:

If I use VFB = 1 (not sure if this is a constant), Vout = 8v, and BotR = 10 ohm, I get 10*(8-1)= 70 ohms.

Is this the best way to dial in a specific voltage for my application? And will the driver still output 2 amps?

Yes except the bottom resistor of the voltage divider is most definitely not 10Ω, I don’t remember the value but it’s in the 10s of kΩ.

Scallywag · 2024-01-08T04:28:59.320Z

Haha, and he gets a reply from the perfect person. I love this.

blacklightning · 2024-01-08T04:50:42.559Z

Thanks, finally made it over from r/flashlight! And you’re right, I completely forgot to convert the SMD resistor code😅 Can you tell if R12 says 01C (10k) or 31D (20.5k)?

(though probably should just order both and verify once I have the part off)

Screenshot_20240107_233045_Chrome~21080×1260 322 KB

@Scallywag haha can’t go wrong with thefreeman himself!

YBF650 · 2024-01-08T08:58:44.813Z

I think it says 31D, looks like it has the orientation line on the right

Can’t check it with a multimeter?

thefreeman · 2024-01-08T10:47:49.194Z

blacklightning:

Can you tell if R12 says 01C (10k) or 31D (20.5k)?

10k.

Jeffgoldblum · 2024-01-08T11:07:28.422Z

Ya it’s 01C.