4.7V to 6V DC-DC Boost Converter Circuit

[DMStrider]

Hi.

I wish to build a DC-DC boost converter circuit to power a small device via usb rather than by means of an AC-DC adapter or batteries (it accommodates both these options as-is). I would prefer the voltage output to be regulated.

The device to be powered operates at 6V 350mA.

To the best of my knowledge a USB port produces ~4.7V 100mA (minimum output voltage is 4.25V and max output voltage is 5.25V).

Would it be possible to supply me with a circuit diagram and component list to increase the DC voltage from 4.7V to 6V?

Should further information be needed, please provide details and I will supply it if I am able to.

Any assistance will be greatly appreciated.

Regards,
David.

 

[Blueteeth]

USB provides a maximum of 500mA. Although there are requirements for devices, not all PC's adhere to these, and some are overly strict in what power a device can draw. I have seen USB provide 600mA, but some will kick up a fuss if you draw more than a few on standby (no device connected, just drawing power). Devices for low power, often tell the USB host they require 100mA max, so the host monitors this. Drawing more current than a device tells the host it needs often results in a blue screen.

All that said, with no device attached and literally just connecting to the USB powerlines, for the most part, you could draw 500mA without much trouble. I jstu thought I would warn you in case you got a blue screen

for minimum USB voltage of 4.25, with the minimum max current draw of 460mA thats 1.955Watts. Your requirement of 6V @ 350mA is 2.1W. Could be tricky. Even if the USB port provided 500mA exactly, thats still only 2.125 - 2.625W. This doesn't leave much margin for error, and requires quite an efficient boost converter.

What device are you trying to power? It may very well happily operate at 5V, or its 350mA rated current draw is an absolute maximum (they usually give the maximum requirement for headroom). And if it can be powered from batteries (for 6v, thats 4x AA's) then I'm sure it can operate at a slightly lower voltage, since a battery's voltage drops slightly as it discharges. Although, at 5V, that would mean each battery is at 1.25V, which many devices consider to be 'pretty dead'.

I am hesitant to recommend the venerable MC34063 chip, because its efficiency will be somewhat disappointing when compared to IC's specifically for this task. Thankfully your current requirement isn't sky high, with a continuous input current of 0.5A, I ithnk we can safely say the peak current will be around 1A. May I ask what parts/distributors you have available to you? Although it takes all the fun out of it, sometimes a simple 'module', whilst being more expensive, can save you time and hassle.

Blueteeth

 

[Mr RB]

(edit) Sorry I said it may work fine at 5v, and then realised Blueteeth had already covered that.(/edit)

 

[Blueteeth]

S'ok mr RB, saw your original post from an email notificaiton to a reply, and you explained it better than I. I can copy/paste your original post back here if you wish.

Plus just found this:
https://www.scribd.com/doc/12593359/usb-to-6v-0

 

[DMStrider]

@Blueteeth:
It is a portable audio controller (with speakers) that was designed for a portable cd player. Since I move between two locations regularly, I find it can be put to better use as portable, as well as compact, pc speakers.

You are correct, it does function happily with 5V. So it was merely soldering a cable to the power terminals rather than constructing a circuit. I would have liked to try my hand at the latter, lol. I did not encounter a blue screen, the only reason I ever did was with an IRQ conflict a while ago, I subsequently resolved that problem, but this is going off topic.

Thanks for correcting my information about the current output of USB ports as well.

As for what parts I have available. Most very common components (i.e. resistors, capacitors, common chips, LEDs, etc) are relatively easy to come by. Other components are not readily available (i.e trimpots, oscillators, potentiometers), but I am able to source them if needed.

For future reference, if you have links to information regarding the construction of DC-DC boost converters, you are more than welcome to post them here.

Thanks for your assistance.

@ Mr RB:
No problem, appreciate your assistance as well.