1.5V, 2-NPN White LED Driver Circuit (LTspice)

[analog]

This post presents an alternate, regulated version of a very simple
1.5V battery based white LED driver circuit from Electronic Design:

http://www.elecdesign.com/Files/29/5886/Figure_01.gif

The LTspice circuit file at the end of this post uses battery volt-
age feedforward and LED current feedback to reduce the effect of
operating conditions on average LED current. The following table
summarizes results of simulations under a range of input voltages.

Vin | Iout | Pout | eff
------+------+------+------
0.9v | 9ma | 34mw | .77
1.1v | 21ma | 94mw | .80
1.3v | 21ma | 92mw | .81
1.5v | 21ma | 87mw | .82
1.7v | 21ma | 84mw | .83

Notes about circuit operation:

Q2 turns off shortly after Q1 begins to steal base current due to
the rising saturation voltage on Q2 (coupled through R3 C1).

Since saturation voltage is device dependent, R1 may have to be
decreased (increased) for weaker (stronger) devices (Q2). A small
emitter degeneration resistor for Q2 could reduce this effect at
the cost of some efficiency and complexity.

Look for attached gifs of the schematic and waveforms in a follow-
up post in alt.binaries.schematics.electronic.

Download the full featured *free* LTspice circuit simulator at:
http://ltspice.linear.com/software/swcadiii.exe

The LTspice file follows directly (beware of unintended line wrap):

---- cut, paste and save as LED_driver.asc ----

Version 4
SHEET 1 1036 680
WIRE -160 416 -160 256
WIRE -160 192 -160 48
WIRE -160 48 -80 48
WIRE 288 48 288 144
WIRE 288 240 288 416
WIRE 0 416 0 352
WIRE 0 256 0 192
WIRE 0 80 0 48
WIRE 0 48 32 48
WIRE 0 416 -160 416
WIRE 144 208 144 176
WIRE 144 48 176 48
WIRE 112 48 144 48
WIRE 288 48 432 48
WIRE -160 416 -160 432
WIRE 432 48 432 160
WIRE 352 416 288 416
WIRE 352 384 352 416
WIRE 432 416 432 400
WIRE 256 304 320 304
WIRE 352 304 352 320
WIRE 432 416 352 416
WIRE 224 192 32 192
WIRE 0 192 0 160
WIRE 144 304 176 304
WIRE 144 304 144 272
WIRE 288 416 80 416
WIRE 64 304 80 304
WIRE 432 320 432 304
WIRE 432 304 352 304
WIRE 432 224 432 304
WIRE 80 304 80 320
WIRE 80 384 80 416
WIRE 80 416 0 416
WIRE 80 304 112 304
WIRE -32 48 0 48
WIRE 144 80 144 48
WIRE 176 48 288 48
WIRE 32 192 0 192
WIRE 112 304 144 304
WIRE 144 176 144 160
WIRE 320 304 352 304
WIRE -80 48 -80 176
WIRE -80 256 -80 304
WIRE -80 48 -32 48
WIRE -80 304 64 304
FLAG -160 432 0
FLAG -32 48 1
FLAG 176 48 2
FLAG 32 192 3
FLAG 112 304 4
FLAG 144 176 5
FLAG 320 304 6
SYMBOL npn 64 256 M0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL npn 224 144 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL res 272 288 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R4
SYMATTR Value 3k3
SYMBOL res -16 64 R0
SYMATTR InstName R2
SYMATTR Value 330
SYMBOL cap 128 208 R0
WINDOW 0 32 16 Left 0
WINDOW 3 32 48 Left 0
SYMATTR InstName C1
SYMATTR Value 1n
SYMBOL Misc\\cell -160 192 M0
WINDOW 123 0 0 Left 0
WINDOW 39 24 72 Left 0
WINDOW 3 24 44 Left 0
SYMATTR SpiceLine Rser=10m
SYMATTR InstName V1
SYMATTR Value 1.5
SYMBOL ind 16 64 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 5 56 VBottom 0
SYMATTR InstName L1
SYMATTR Value 100µ
SYMATTR SpiceLine Ipk=1 Rser=0.33 Rpar=0 Cpar=0 mfg="WE eiSos" pn="744 562 0"
SYMBOL diode 416 160 R0
WINDOW 0 40 16 Left 0
WINDOW 3 40 52 Left 0
SYMATTR InstName D2
SYMATTR Value LED
SYMBOL res 416 304 R0
SYMATTR InstName R5
SYMATTR Value 10
SYMBOL diode 64 384 M180
WINDOW 0 40 48 Left 0
WINDOW 3 40 12 Left 0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL res 128 64 R0
SYMATTR InstName R3
SYMATTR Value 330
SYMBOL polcap 336 320 R0
WINDOW 0 32 16 Left 0
WINDOW 3 32 52 Left 0
SYMATTR InstName C2
SYMATTR Value 10µ
SYMATTR SpiceLine V=50 Irms=170m Rser=1 MTBF=5000 Lser=0 mfg="Nichicon" pn="UPG1H100MPH" type="Al electrolytic" ppPkg=1
SYMBOL res -96 160 R0
SYMATTR InstName R1
SYMATTR Value 4k3
TEXT 432 8 Center 0 !.model LED d(Vfwd=3.4V Ron=10)
TEXT -298 10 Left 0 !.tran 0 .3m .1u uic
TEXT 528 120 Left 0 ;R1: 4k3 R4: 3k3\n+Vin Iout Pout eff\n_0.9v 9ma 34mw .77\n1.1v 21ma 94mw .80\n1.3v 21ma 92mw .81\n1.5v 21ma 87mw .82\n1.7v 21ma 84mw .83

 

[Andre]

This post presents an alternate, regulated version of a very simple
1.5V battery based white LED driver circuit from Electronic Design:

Interesting. I found a way to enhance the efficiency of a similar
circuit using nothing more than a single silicon diode from base to
emitter on the output transistor.

(this is the "mirror" circuit that uses an NPN and PNP transistor, and
about two other parts).

 

[Henry Kolesnik]

please post your circuit..
tnx
hank wd5jfr

Interesting. I found a way to enhance the efficiency of a similar
circuit using nothing more than a single silicon diode from base to
emitter on the output transistor.

(this is the "mirror" circuit that uses an NPN and PNP transistor, and
about two other parts).

34mw .77\n1.1v 21ma 94mw .80\n1.3v 21ma 92mw .81\n1.5v 21ma 87mw .82\n1.7v
21ma 84mw .83

 

[James Meyer]

please post your circuit..
tnx
hank wd5jfr

34mw .77\n1.1v 21ma 94mw .80\n1.3v 21ma 92mw .81\n1.5v 21ma 87mw .82\n1.7v
21ma 84mw .83

Dear Henry,

It is seldom necessary to quote an entire message that quotes another
entire message simply to add "post your circuit".

Jim

 

[James Meyer]

Interesting. I found a way to enhance the efficiency of a similar
circuit using nothing more than a single silicon diode from base to
emitter on the output transistor.

(this is the "mirror" circuit that uses an NPN and PNP transistor, and
about two other parts).

Dear Testing,

It is seldom necessary to quote an entire LTSpice circuit posting simply
to add a single silicon diode to the circuit.

Jim

 

[Jim Thompson]

This post presents an alternate, regulated version of a very simple
1.5V battery based white LED driver circuit from Electronic Design:

http://www.elecdesign.com/Files/29/5886/Figure_01.gif

The LTspice circuit file at the end of this post uses battery volt-
age feedforward and LED current feedback to reduce the effect of
operating conditions on average LED current. The following table
summarizes results of simulations under a range of input voltages.

Vin | Iout | Pout | eff
------+------+------+------
0.9v | 9ma | 34mw | .77
1.1v | 21ma | 94mw | .80
1.3v | 21ma | 92mw | .81
1.5v | 21ma | 87mw | .82
1.7v | 21ma | 84mw | .83

[snip]

With PSpice I don't get such stability, but I'm using a real
(logarithmic) LED model as opposed to one of Mikey's "funny diodes"
;-)

...Jim Thompson

 

[Jim Thompson]

Interesting. I found a way to enhance the efficiency of a similar
circuit using nothing more than a single silicon diode from base to
emitter on the output transistor.

(this is the "mirror" circuit that uses an NPN and PNP transistor, and
about two other parts).

[snip]
Dear Testing,

It is seldom necessary to quote an entire LTSpice circuit posting simply
to add a single silicon diode to the circuit.

Jim

Crabby! Crabby! Crabby! Jim, Are your ribs still taped up ?

...Jim Thompson

 

[Tim Williams]

Dear Henry,

It is seldom necessary to quote an entire message that quotes another
entire message simply to add "post your circuit".

Dear James,

It is seldom necessary to quote an entire message that quotes another entire
message that quotes another entire message simply to add three lines of text
at the bottom.

Trim or top post.

Tim

 

[Tim Williams]

Where's your post? I scrolled down five pages before giving up.

Tim

 

[Tim Auton]

Where's your post? I scrolled down five pages before giving up.

Five pages of what? I stopped at your (broken) sig separator. It's
"-- " not "--". Snip and quote properly if you want to be a usenet
cop.


Tim, just waiting for a speling, grammar or formatting flame.

 

[Mark Jones]

In news:[email protected] (Tim Auton):

Five pages of what? I stopped at your (broken) sig separator. It's
"-- " not "--". Snip and quote properly if you want to be a usenet
cop.


Tim, just waiting for a speling, grammar or formatting flame.

Luuuuurker! Luuuuuuuuuuuuurker!

 

[R.Lewis]

Why do you have to click on 'Start' when you want to stop Windows?

 

[Bill Garber]

message : Why do you have to click on 'Start' when you want to stop
Windows?

That's for the people who use AOL. ;-)

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - [email protected]
Remove - SPAM and X to contact me

 

[John Woodgate]

I read in sci.electronics.design that R.Lewis <[email protected]>

Why do you have to click on 'Start' when you want to stop Windows?

You don't. Wait a few minutes and it will stop by itself, with a pretty
blue screen. (;-)

 

[Al]

message : Why do you have to click on 'Start' when you want to stop
Windows?

That's for the people who use AOL. ;-)

That's nothin' I have to push "NO" on my cell phone to turn it on. I
guess it's "ON" backwards.

Al

 

[Tim Williams]

Why do you have to click on 'Start' when you want to stop Windows?

I don't. I ALT+F4

Tim

 

[petrus bitbyter]

Why do you have to click on 'Start' when you want to stop Windows?

I heard a lot of rumours about it. I remember only two of them:

- Windows is so great an operating system that nowbody ever wants to stop
it.

- The developers simply forgot the stop button as they never needed it.

If anyone knows better, I like to hear it. Always in the mood of learning
something new.

petrus

 

[Bill Garber]

:
: "R.Lewis" <h.lewis-not this [email protected]> schreef in
bericht
: : > Why do you have to click on 'Start' when you want to stop
Windows?
:
: I heard a lot of rumours about it. I remember only two of them:
:
: - Windows is so great an operating system that nowbody ever
wants to stop
: it.
:
: - The developers simply forgot the stop button as they never
needed it.
:
: If anyone knows better, I like to hear it. Always in the mood
of learning
: something new.
:
: petrus

I can't quote this, but I read somewhere that Bill Gates
himself had told a group that you press START to initiate
any function, and since SHUT DOWN is a function..........

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - [email protected]
Remove - SPAM and X to contact me

 

[Bill Garber]

: I read in sci.electronics.design that R.Lewis
<[email protected]>
: wrote (in <[email protected]>) about '1.5V, 2-NPN
White LED
: Driver Circuit (LTspice)', on Wed, 7 Jan 2004:
: >Why do you have to click on 'Start' when you want to stop
Windows?
: >
: >
: You don't. Wait a few minutes and it will stop by itself, with
a pretty
: blue screen. (;-)

Mine is Maroon now. Get a program called BSOD.EXE
when you are sick of the Blue, change it to whatever
suits you. ;-)

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - [email protected]
Remove - SPAM and X to contact me

 

[Michael A. Terrell]

: I read in sci.electronics.design that R.Lewis
<[email protected]>
: wrote (in <[email protected]>) about '1.5V, 2-NPN
White LED
: Driver Circuit (LTspice)', on Wed, 7 Jan 2004:
: >Why do you have to click on 'Start' when you want to stop
Windows?
: >
: >
: You don't. Wait a few minutes and it will stop by itself, with
a pretty
: blue screen. (;-)

Mine is Maroon now. Get a program called BSOD.EXE
when you are sick of the Blue, change it to whatever
suits you. ;-)

Bill

My last computer was set for a blood red screen. I think I used
Tweek-UI to change it.

Also, a Monty Python character yelled, "You started it, you bleeding
pig!" when you closed Windows on my last machine that ran Win 3.11.


--
We now return you to our normally scheduled programming.

Take a look at this little cutie! ;-)
http://home.earthlink.net/~mike.terrell/photos.html

Michael A. Terrell
Central Florida