Shark Buck

[Aircraft800]

Once it drops out of regulation, does the shark buck direct drive and operate normally? If the overhead is not so high, low vf XM-L string might say in regulation till the batteries are 3.2v per cell, and are just about depleted anyway (3v correct?).

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[dat2zip]

Yes, the Shark Buck drops out of regulation and goes into DD.

Wayne

[vestureofblood]

With a shark buck once the voltage drops near the VF of the LED does it cut the power off, or will it go to DD?

[dat2zip]

With a shark buck once the voltage drops near the VF of the LED does it cut the power off, or will it go to DD?

It drops into DD.

[Darkstang]

New member here but have done a lot of reading and searching on the Shark Buck. What is the typical overhead that the sharkbuck needs in highpower useage?

I am interested in driving several Xm-l in series from a automotive setup. My supply is 14.3v that seems to be decently regulated. I know I will still need to add an inline regulator setup to the power for protection of the Shark setup.

With a vf of 3.35 volts at 3 amps for the xml, that puts me around 10 volts for 3 Xm-l's. This leaves 4.3 for the Shark to dissipate out in the form of heat. My concern is when turned down to lower settings when supposedly the xm-l's vf drops as low as 2.8-2.9. This could leave a ceiling of over slightly 5 volts. Is this too much?

4 xm-l's would be at 3.35 would only give a ceiling of about 1 volt and I believe from some of your replies, that may be too little.

Airflow and heatsinking are not a concern since it will have lots of airflow and can be hooked to good sized sinks.

Would like to use a shark buck if I can in this situation to make it simple. Also thought about doing the poor mans multi lux setup as well.

[videoman]

I wish to drive a single XM-L led with the Shark buck 3A, the battery voltage is either going to be 6 volts or 12 volts DC. If I use the 12V source, will the driver get hotter as opposed to using a 6 V source ? Does it also mean that it wastes the excess voltage in heat, introducing the possibility of thermal shutdown as opposed to using 6V ?

[Justin Case]

The Shark Buck is a buck driver (hence the name), not a linear regulator.

[videoman]

About the heat thing ?

[cmacclel]

About the heat thing ?

It's a real driver so heat should not be an issue.

Mac

[Justin Case]

The Shark Buck is a buck driver. The driver "bucks" down Vin to match Vout by adjusting its duty cycle. It isn't a linear regulator that burns up the excess voltage as heat.

[videoman]

So what you are saying is that the Shark buck outputting it's rated 3A stays at THE SAME heat level REGARDLESS of the input rated voltage. Like a XM-L with a 6 volt battery and changing it to a 14.4 volt battery, the Buck won't get hotter ?

[Justin Case]

The Shark Buck 3A's efficiency is relatively constant from 5V to 15V, so yes there is essentially no change in amount of waste heat generated.

It's not a linear regulator. It doesn't work by burning off excess voltage as heat.

It's not a linear regulator. It doesn't work by burning off excess voltage as heat.

It's not a linear regulator. It doesn't work by burning off excess voltage as heat.

It's not a linear regulator. It doesn't work by burning off excess voltage as heat.

[videoman]

"This leaves 4.3 for the Shark to dissipate out in the form of heat."

Post # 155 by Darkstang

That's the reason I ask.

[Justin Case]

Post #155 is wrong.

Do a web search to learn how a buck driver works vs a linear regulator.

[videoman]

Is the Shark buck's dimming designed as a PWM dimming ?

[dat2zip]

Is the Shark buck's dimming designed as a PWM dimming ?

The trim pot is analog in nature. You can vary the DC voltage to control the output or PWM this pin to vary the brightness. (analog is preferred).

Wayne

[videoman]

Thanks Wayne. The reason the PWM used for dimming concerns me is that many video cameras have experienced "banding" issues when used with PWM led light units by several led light manufacturers. This banding is horizontal lines that are apparent on the video when the fps (frames per second) or shutter speed is set to 50fps or higher for slow motion capture. It is not apparent at the 29.97 fps standard speed mode though. As long as the dimming is non PWM, there is no banding problem. Also to mention is that several videographers have experienced a high pitched frequency sound that is recorded and picked up by the camera's microphone that is in close proximity to the PWM dimmed led light.Whether this high pitched frequency sound emanates from the driver due to the PWM design or to other electronics in the driver is a mystery.I have never experienced this banding or high pitched sound with your drivers as the dimming is done with an analog pot (20K log.) I am happy that the Shark Buck used with an analog pot for dimming does not have those issues.

[dat2zip]

Thanks Wayne. The reason the PWM used for dimming concerns me is that many video cameras have experienced "banding" issues when used with PWM led light units by several led light manufacturers. This banding is horizontal lines that are apparent on the video when the fps (frames per second) or shutter speed is set to 50fps or higher for slow motion capture. It is not apparent at the 29.97 fps standard speed mode though. As long as the dimming is non PWM, there is no banding problem. Also to mention is that several videographers have experienced a high pitched frequency sound that is recorded and picked up by the camera's microphone that is in close proximity to the PWM dimmed led light.Whether this high pitched frequency sound emanates from the driver due to the PWM design or to other electronics in the driver is a mystery.I have never experienced this banding or high pitched sound with your drivers as the dimming is done with an analog pot (20K log.) I am happy that the Shark Buck used with an analog pot for dimming does not have those issues.

Yes, I am familiar with the issues you describe. There are many forms of PWM. PWM encompasses different technologies and PWM can give a bad perception to the technology due to how it is implemented.

Depending on how or the type of PWM method you can encounter PWM noise. If the PWM frequency is in the audio range and the inductor, capacitor or PCB could vibrate and become a speaker per se and generates this noise.

I go through great effort to make sure the engineering of my products do not generate any PWM signal in the LED current waveform and go through great lengths in component selection and PCB layout to prevent component singing.

I have a new buck converter that is nearing finalization that uses PWM and it should not generate the banding or singing of any audio noise.

The Shark Buck Remora board uses PWM, but, the PWM signal is filtered to DC before applied to the control pin that the trim pot connects to. The trim pot and the Remora board both should be effectively DC control of LED brightness of the converter board.

Wayne

[videoman]

Great to hear that Wayne. What diameter size will that new driver be ? Will it have provision to put an analog dimmer pot to it ?
Thanks

[videoman]

Wayne, I have a question. The copper C that is under the Shark, I imagine it is there for reason of heat. I always use arctic silver 2 part adhesive to pot the Shark to my heatsink. I use a lot of it because of the thickness of the copper C. I put the adhesive on the entire under area of the shark. If the copper C is eliminated I can use a lot less of the adhesive but will it compromise the heat or will it be ok ?

[Ginseng]

Hi Wayne,
I was wondering if it would be possible to have a Shark Buck made to deliver 3.5A? I plan on driving an XM-L with 2xLiIon in a 2C Mag Body. I know you say that 4A is really not advisable still I'd really like to push this installation.
Wilkey

[dat2zip]

Hi Wayne,
I was wondering if it would be possible to have a Shark Buck made to deliver 3.5A? I plan on driving an XM-L with 2xLiIon in a 2C Mag Body. I know you say that 4A is really not advisable still I'd really like to push this installation.
Wilkey

I can not advise that. The IC internal switch limit is min 3A, Typ 4A, max 5A. Also, the heat of the IC, inductor and diode are already pushing the boards limitation. Even if the IC internal switch was 4A I am pretty certain it will thermally limit out in less than a minute.

If you want 4A you can use two in parallel each set for 2A to get the 4A configuration.

Wayne

[dat2zip]

Wayne, I have a question. The copper C that is under the Shark, I imagine it is there for reason of heat. I always use arctic silver 2 part adhesive to pot the Shark to my heatsink. I use a lot of it because of the thickness of the copper C. I put the adhesive on the entire under area of the shark. If the copper C is eliminated I can use a lot less of the adhesive but will it compromise the heat or will it be ok ?

????

The copper C is the only way I know of that spreads the heat out from the hot spots of the IC, diode, inductor. Without the copper C any attachment method will fail as soldering the copper C is far superior to any method I am aware of. It also gives the end user the best possible chance of moving the heat away from the converter board as efficiently as possible.

There is no need for a lot of thermal epoxy to mount the Shark to heatsink. The only surface that needs proper mating is the bottom of the copper C. Any additional epoxy that touches the converter board adds little if any additional heat sinking capability.

You will get the best heat transfer if you can make your glue joint 1/2 as thick as it is now. Halving the thermal adhesive layer will more than double the transfer since Arctic alumina or Arctic Silver is such a poor thermal performer compared to copper, aluminum. It is the glue joint that will make or break the installation. Getting the converter mounted optimally is key to longevity and keeping the converter running as cool as possible.

If you have a dead Shark I would play with that to test your mounting procedure and verify it by popping off the converter after the thermal adhesive has setup. An ideal thickness is nearly transparent. If you can't see the copper C through the adhesive layer then it is too thick.

Wayne

[Ginseng]

I can not advise that. The IC internal switch limit is min 3A, Typ 4A, max 5A. Also, the heat of the IC, inductor and diode are already pushing the boards limitation. Even if the IC internal switch was 4A I am pretty certain it will thermally limit out in less than a minute.
If you want 4A you can use two in parallel each set for 2A to get the 4A configuration
Wayne

Thanks, Wayne. Looks like we're going to go with the 3A max on a single board because of space limitations. If well sinked, do you think it would run for 10 minutes without triggering thermal shutdown?
Wilkey

[jamesavery22]

Could I drive a XM-L at 2.4A w/ the Shark Buck using two RCR123's or two CR123's? Would two CR123's dip too low in voltage?