custom Boost circuit

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AtomSoft

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Hey guys me again Im trying to make my own boost circuit to save some money heh.. I want to know about this i came up with... Im trying to power 7 white LEDs from 3.7 to 5v....

I wanted to know ... since i made this there is about a 80% chance somethings bad or will go bad heh... take a look at the schematic and tell me if it has a chance of working...

 

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I think it will work fine.


Edit, that's a 100uH 3A choke, a 1N4148 and a 330uF cap. With 1k resistor current is 9mA, with 330R it's 12.5mA.

Mike.
 

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Hello there,


The boost theory says that the basic output voltage is Vi/(1-D) where D is the duty cycle, but for very light loads you can get higher outputs with smaller duty cycles. With 50 percent duty cycle and light load you might get 20 or more volts out, it depends partly on the current and efficiency of the coil. For such a light load like this you might even be able to get away with a small coil like those tubular kinds even though they can have a much higher resistance. 100uH or 200uH would probably do it. If you dont get enough output you can try increasing the 'on' duty cycle a little, but not too much.
 
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Thanks for the test Pommie.. some fears went away

MrAl thanks for the info!

Do i have to worry about some of the voltage leaking back to the pic?
 
One more simple question. Are Inductor codes like CAPACITOR codes? Where a 220 would be 22uh and a 221 would be 220uh?

So this would be a 22uh inductor:


And both of these are 220uh inductors:
 

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Ok i got it almost perfect in simulation...

Using :
 

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Pommie said:
I think it will work fine.

Edit, that's a 100uH 3A choke, a 1N4148 and a 330uF cap. With 1k resistor current is 9mA, with 330R it's 12.5mA.

Mike.
Click to expand...

Mike, did you build the choke yourself? How do we actually determine the approximate inductance? BTW, that's a really neat one.
 
I tried to make this neat like Mike lol he has all the skills
I get about 27v and using 16mA with a 220 ohm...



My Pic code to trigger every 30khz (or close to it)
Code: 
/* *****************************************************************************
;                                                                             *
;    Filename:                     				                              *
;    Date:                                         	                          *
;    File Version: 001                                                        *
;                                                                             *
;    Author:   Jason Lopez                                                    *
;    Company:  AtomSoft                                                       *
;                                                                             *
;***************************************************************************** */

#include <p18f2525.h>
#include <delays.h>
#include <string.h>

#pragma config WDT = OFF, LVP = OFF, OSC = INTIO67, XINST = OFF

/************************************
Prototypes
*************************************/
void main(void);


/************************************
Main
*************************************/
void main(void){
	OSCCON = 0x72;      			//8MHz clock
	while(!OSCCONbits.IOFS);		//wait for osc stable

	ADCON1 = 0x0F;			//Digital Pins (we dont need ADC)

	TRISA = TRISB = TRISC = 0x00;	//All Outputs
	LATA = LATB = LATC = 0x00;		//All Low

	while(1){
		LATCbits.LATC3 = 0;
		Delay10TCYx(6);
		Nop();		Nop();

		LATCbits.LATC3 = 1;
		Delay10TCYx(6);
		Nop();		Nop();

	}
}
 

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AtomSoft said:
One more simple question. Are Inductor codes like CAPACITOR codes? Where a 220 would be 22uh and a 221 would be 220uh?

So this would be a 22uh inductor:


And both of these are 220uh inductors:
Click to expand...


Hello again,


Yes i believe you are correct on that. However, we have to give the last word to the manufacturer who ultimately will dictate how their marking system works. In other words, one manu might use 220 for a 220uH and the other would use 221 for a 220uH, but i would go with your idea first in the event of no other information. A little test wouldnt hurt i guess just to make sure too. I dont remember what test equipment you have though. Since it looks like you got this circuit working pretty nicely now, if you have a scope you can do an in-circuit test if you like.
 
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I wish i had a scope .. i dont even have a LC meter or what ever is the name. all i have is a multimeter... If i had a scope i think i would know way more since i can see whats happening all the time...
 
Hi again,


I dont know if it is in your budget, but they make digital scopes for the PC, and analog scopes for as low as 300 dollars USD. It depends i guess if you want to do a lot of these kinds of circuits and you would learn a lot. For example, you can tell what the inductance of an inductor is by looking at the ramp of its current waveform vs time on the scope.
 
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Hi again,


Doesnt look that bad really, but unfortunately i dont have any experience with those scopes so maybe you can ask in a new thread here or find a forum or some user feedback on those scopes somewhere else. That might give you a btter idea what to expect than i can give you.
 
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