Voltage booster? - Electronic Circuits Projects Diagrams Free

bananasiong · 26th December 2006, 04:54 PM

Hi,
I found this: drive a LED with a single AA battery, is this also called voltage booster circuit? I've googled, some voltage booster use 555 timer, some use handmade coil with center tapping, and some use capacitor to hold the output voltage so that it won't be lower than supply voltage.
Can this circuit last long if i use only a single rechargeable AA (rated 2500mAh)?

audioguru · 26th December 2006, 05:20 PM

I don't know what is the duty-cycle of the oscillator and don't know for what percentage of each half-cycle the inductor can power the LED. I don't know the efficiency of this circuit.

Assuming that the blue LED needs 3.6V then the voltage must be stepped up 3 times. Assuming that the average on-current of the LED is 30mA and with a 50:50 duty-cycle then the total average current is 15mA. Then a 2500mAh battery cell's charge would last for 2500/(15 x 3)= 55.6 hours. The peak current could be higher then the battery cell's charge would last only 55.6/2= 27.8 hours.

hjames · 26th December 2006, 07:02 PM

It would be nice if these circuits would be properly referenced - the caption font is the one that ednmag uses:

http://www.edn.com/article/CA90758.h...=nbra&text=led

The author claims ~40mA current draw, for a ~4hr lifetime for a 1400mAH NiMH.

Whoops - typo'd that - should be 1600mAh

audioguru · 26th December 2006, 10:52 PM

Quote:

Originally Posted by hjames

The author claims ~40mA current draw, for a ~4hr lifetime for a 1400mAH NiMH.

Actually the author claims a 4 hours battery charge lifetime for a 1600mAh cell.
He can't calculate very well. A 1600mah cell will provide 40mA for about 40 hours.

bananasiong · 26th December 2006, 11:10 PM

Are the numbers in the circuit from the pins of 555 timer? Can the voltage be boosted without any oscillator i.e. 555 timer?

audioguru · 27th December 2006, 12:25 AM

The numbers on the schematic have nothing to do with a 555 IC. This circuit is a 2-transistor oscillator that boosts the voltage by using an inductor. A "charge-pump" circuit is different and uses an oscillator and capacitors to double or triple the supply voltage.

bananasiong · 27th December 2006, 12:50 AM

Can this circuit boost up to 5 volts to drive the microcontroller?
I've seen some booster with 555 timer, some with booster IC.

mramos1 · 27th December 2006, 01:37 AM

Quote:

Originally Posted by bananasiong

Can this circuit boost up to 5 volts to drive the microcontroller?
I've seen some booster with 555 timer, some with booster IC.

Use two cells and run the microcontroller for a long time (without the 555).. Run it at low speed 30-50Khz.

Or if size is a problem get the small AG-13 cells. Use 2 of them and run a 12F683 for more than a week with two AG-13 cells driving a load.

What are you attempting? AudioGuru gave you the numbers for your question.

bananasiong · 27th December 2006, 03:09 AM

No, I just want to know how does it be boosted up. And any calculation can be done? For calculating the boosted voltage.

audioguru · 27th December 2006, 04:19 AM

The boosted voltage with an inductor can be 100V or more, but the current is reduced the same amount the voltage is boosted so that the power remains the same, minus losses. For LED drivers, the LED limits the boosted voltage.

bananasiong · 27th December 2006, 05:34 AM

Can I control or limit the boosted voltage to be 5 volts?

Oznog · 27th December 2006, 05:42 AM

The LED itself will limit the voltage, because it is primarily a current-output device. The LED's I/V relationship determines the voltage based on the current running through it.

audioguru · 27th December 2006, 05:55 AM

You can use a boost circuit then a zener diode to limit the voltage. The zener diode will waste a lot of power.

RODALCO · 27th December 2006, 08:53 AM

Look under google for Joule thief.
has been discussed in these forums too.

In it is a more simple cct which drains a standard battery down to about 0.4 volts.
That only consists of a double wound coil, transistor and resistor and works very well.

RODALCO · 27th December 2006, 08:57 AM

http://www.emanator.demon.co.uk/bigclive/joule.htm

this is the link, with a good detailed describtion how to build it.

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26th December 2006, 04:54 PM	#1
bananasiong	Voltage booster? Hi, I found this: drive a LED with a single AA battery, is this also called voltage booster circuit? I've googled, some voltage booster use 555 timer, some use handmade coil with center tapping, and some use capacitor to hold the output voltage so that it won't be lower than supply voltage. Can this circuit last long if i use only a single rechargeable AA (rated 2500mAh)? Attached Thumbnails __________________ bananasiong

26th December 2006, 05:20 PM	#2
audioguru	I don't know what is the duty-cycle of the oscillator and don't know for what percentage of each half-cycle the inductor can power the LED. I don't know the efficiency of this circuit. Assuming that the blue LED needs 3.6V then the voltage must be stepped up 3 times. Assuming that the average on-current of the LED is 30mA and with a 50:50 duty-cycle then the total average current is 15mA. Then a 2500mAh battery cell's charge would last for 2500/(15 x 3)= 55.6 hours. The peak current could be higher then the battery cell's charge would last only 55.6/2= 27.8 hours. __________________ Uncle $crooge

26th December 2006, 07:02 PM	#3
hjames	It would be nice if these circuits would be properly referenced - the caption font is the one that ednmag uses: http://www.edn.com/article/CA90758.h...=nbra&text=led The author claims ~40mA current draw, for a ~4hr lifetime for a 1400mAH NiMH. Whoops - typo'd that - should be 1600mAh Last edited by hjames; 27th December 2006 at 01:34 AM.

26th December 2006, 11:10 PM	#5
bananasiong	Are the numbers in the circuit from the pins of 555 timer? Can the voltage be boosted without any oscillator i.e. 555 timer? __________________ bananasiong

27th December 2006, 12:25 AM	#6
audioguru	The numbers on the schematic have nothing to do with a 555 IC. This circuit is a 2-transistor oscillator that boosts the voltage by using an inductor. A "charge-pump" circuit is different and uses an oscillator and capacitors to double or triple the supply voltage. __________________ Uncle $crooge

27th December 2006, 12:50 AM	#7
bananasiong	Can this circuit boost up to 5 volts to drive the microcontroller? I've seen some booster with 555 timer, some with booster IC. __________________ bananasiong

27th December 2006, 03:09 AM	#9
bananasiong	No, I just want to know how does it be boosted up. And any calculation can be done? For calculating the boosted voltage. __________________ bananasiong

27th December 2006, 04:19 AM	#10
audioguru	The boosted voltage with an inductor can be 100V or more, but the current is reduced the same amount the voltage is boosted so that the power remains the same, minus losses. For LED drivers, the LED limits the boosted voltage. __________________ Uncle $crooge

27th December 2006, 05:34 AM	#11
bananasiong	Can I control or limit the boosted voltage to be 5 volts? __________________ bananasiong

27th December 2006, 05:42 AM	#12
Oznog	The LED itself will limit the voltage, because it is primarily a current-output device. The LED's I/V relationship determines the voltage based on the current running through it. __________________ I thought what I'd do was I'd pretend I was one of those deaf-mutes.

27th December 2006, 05:55 AM	#13
audioguru	You can use a boost circuit then a zener diode to limit the voltage. The zener diode will waste a lot of power. __________________ Uncle $crooge

27th December 2006, 08:53 AM	#14
RODALCO	Look under google for Joule thief. has been discussed in these forums too. In it is a more simple cct which drains a standard battery down to about 0.4 volts. That only consists of a double wound coil, transistor and resistor and works very well. __________________ There are more ways to get to Rome. Electricity, Electric clocks, Meters and Trains are great. Please don't sent me private messages, I will not answer them. The questions asked can be discussed in the open forums. http://www.youtube.com/user/RODALCO2007 some interesting electrical stuff to watch.

27th December 2006, 08:57 AM	#15
RODALCO	http://www.emanator.demon.co.uk/bigclive/joule.htm this is the link, with a good detailed describtion how to build it. __________________ There are more ways to get to Rome. Electricity, Electric clocks, Meters and Trains are great. Please don't sent me private messages, I will not answer them. The questions asked can be discussed in the open forums. http://www.youtube.com/user/RODALCO2007 some interesting electrical stuff to watch.