ZXSC300 0.8v-4.5V 700mA 3W LED Driver - help with componets

[smilem]

Hi,

My LED is 3W 700mA max
AVAGO TECHNOLOGIES|ASMT-JW32-NVV01|LED, 3W, COOL-WHITE, MINIMUM 100LM | Farnell LT

Power source is 1.5V batteries x3 = 4.5Volts.

I would like to use ZXSC300 because it works up to 0.8V and I don't want to waste any power from my batteries

Here is datasheet for ZXCS300:
http://www.diodes.com/datasheets/ZXSC300.pdf

I tried to use ZXSC300 Feed Forward calculator here:
http://www.diodes.com/_files/calculators/ZXSC300_Calculator.xls

But I'm not sure my input power is 4.5V and calculator allow to use lower voltage than LED forward voltage 3.8V in my case.
Furthermore calculator allows to use 500mA and my LED is 700mA

I also have this datasheet that shows a setup to power 500mA led
http://www.diodes.com/zetex/_pdfs/3.0/appnotes/apps/an65.pdf

But it's for 3V input, if I have 4.5V and use 40mR sense resistor I think it should peak at 700mA. Thats just a guess.

 

[Selectron]

Could you clarify what type of cells you intend to use for this - primary (non-rechargeable) or secondary (rechargeable) and what type - e.g. alkaline, NiMH, or something else?

If you're intending to use either Nicad or NiMH then they would be damaged by allowing a series string of three to fall as low as 0.8V - by the time they reached that level, at least one cell would have developed a reverse-polarity, and in the case of primary cells such as alkaline, if a series string of three was allowed to fall as low as 0.8V then I think the risk of electrolyte leakage would be greatly increased.

It makes sense to clear that up first before looking at driver details. Thanks.

 

[VegasF6]

From the data sheet:

The ZXSC300 is a single or multi cell LED driver
designed for applications where step-up voltage​

conversion from very low input voltages is required.

It appears you are wanting to use this IC as a boost/buck circuit, which it isn't designed to do. I am not quite sure what will happen if battery V is greater than led V but I am thinking you will damage the circuit, and direct drive the led burning it up as well. I would suggest you lower your input voltage, then use the calculator to find an approx value for your sense resistor. You can fine tune it with a pot if needed.

This board from DX http://www.dealextreme.com/details.dx/sku.3256 used to have the ZX300 IC (supposedly some had the 310 but not that I ever got, same thing mostly anyhow) but has since been replaced with AX2002 IC which is superior anyhow.

 

[smilem]

From the data sheet:

The ZXSC300 is a single or multi cell LED driver
designed for applications where step-up voltage​

conversion from very low input voltages is required.

It appears you are wanting to use this IC as a boost/buck circuit, which it isn't designed to do. I am not quite sure what will happen if battery V is greater than led V but I am thinking you will damage the circuit, and direct drive the led burning it up as well. I would suggest you lower your input voltage, then use the calculator to find an approx value for your sense resistor. You can fine tune it with a pot if needed.

This board from DX http://www.dealextreme.com/details.dx/sku.3256 used to have the ZX300 IC (supposedly some had the 310 but not that I ever got, same thing mostly anyhow) but has since been replaced with AX2002 IC which is superior anyhow.

Well I can't find the AX2002 IC on Farnell, mouser, lemona catalogs so if it's only available in china then so be it.

The ZXCS300 310 can be used as Step down converter. I also found schematic for 3W LED http://www.diodes.com/_files/design_note_pdfs/zetex/dn73.pdf

However it's for 3.8V to 6.2V, and I need 1V to 4.5V. The calculator isn't working for this configuration. And my math is a bit rusty. Is it possible to use it in voltage range I want?

At some china site I found these screenshots:
They tested ZXCS300 and AMC7135
LED was LUMILEDS LXHL-PW09
Forward voltage 3.9V Peak Forward Current:1000mA

They damaged the LED running at more than 1360mA, the LED data sheet shows values for 1400mA but the schematic did work. I'm puzzled how did it work, it's the same schematic you said would fry the LED if voltage is more than 3V. But if you look at the table LED with Vf 3.9V worked until 5.4V

I tried to get AMC7135 but to no avail, seems only available in china.

 

[VegasF6]

Well I can't find the AX2002 IC on Farnell, mouser, lemona catalogs so if it's only available in china then so be it.
Yes, I don't know anyone who has found the AX chips for sale on their own. Too bad, they have some nice stuff. You could try and request a sample here if you like. I would love to get hold of a ax2003
http://www.micro-bridge.com/AX2002_AX2003.asp

The ZXCS300 310 can be used as Step down converter. I also found schematic for 3W LED http://www.diodes.com/_files/design_note_pdfs/zetex/dn73.pdf
True, it can also be used as a step down converter. More commonly it is a boost converter. However, that doesn't mean it can operate as a boost/buck converter in the same configuration.

However it's for 3.8V to 6.2V, and I need 1V to 4.5V. The calculator isn't working for this configuration. And my math is a bit rusty. Is it possible to use it in voltage range I want?
I don't know, hopefully someone else can confirm or deny. At a guess, I believe if you use it with that voltage range, with only the 1 led you mention, then when your input V is higher that ~3.7-3.9 drive current will not be regulated and led will not be protected. Could be wrong.
At some china site I found these screenshots:
They tested ZXCS300 and AMC7135
LED was LUMILEDS LXHL-PW09
Forward voltage 3.9V Peak Forward Current:1000mA

They damaged the LED running at more than 1360mA, the LED data sheet shows values for 1400mA but the schematic did work. I'm puzzled how did it work, it's the same schematic you said would fry the LED if voltage is more than 3V.
I don't think I said that. I think I said "I am not quite sure what will happen if battery V is greater than led V but I am thinking you will damage the circuit, and direct drive the led burning it up as well."
But if you look at the table LED with Vf 3.9V worked until 5.4V
Depends on what you mean by "it worked." I am sure the led was lit, that is the easy part. But the regulation was horrible allowing the led to be damaged.
I tried to get AMC7135 but to no avail, seems only available in china.
This IC is also difficult to get. Most people here simply purchase premade boards containing them and remove the component themselves. I believe a member here had some for sale in the marketplace. There is a seller on eBay that claims he can supply this as part of a $300 bulk lot.
This IC won't meet your specifications anyhow, it is simply a linear regulator, only capable of dropping excess current. Its advantage is it is very easy to use.

 

[smilem]

I have a china made led torch with AMC7135 chip in it.
The thing is 1W Luxeon LED 350mA. Work very nice, even with very low power batteries. I recently build joule thief circuit. And I have a spare seoul 1W Led, I was shocked to find out that the AMC7135 was better than joule thief on the same batteries.

Perhaps you know another IC I could use for my project? Should run on the voltages I mentioned 1V to 4.5V at 700mA. I looked at linear tech. they have something from 1.36V but very expensive.

I hope somebody helps me with those calculations for zxcs300 chip.

 

[eprom]

hi similem,

a driver like you think is our dream. IC that can help you, can be FP5138. DX sells drivers with this IC but they are only with boost topology. This IC can be used with sepic topology. If you look datasheet page.13 second schematic is refering to sepic (buck-boost) topology which can output 3.3V from 2.5V~6V input, this input range will keep the batteries in safe.
For Ni-Mh's going under 0.8V is not recomended, on 3xNi-Mh setup 2.4V is safety limit. Under 0.9V alkalines will not give enough juice for high loads so when 3xAlkalines used 2.7V is usable limit. I think this is constant voltage driver but wish someone can help you to make it constant current (ex. HansV has great knowledge). Dealextreme sku's with this driver IC are sku.26106 and sku.25516

SEPIC Schematic

wish helps,

 

[smilem]

Thanks for the circuit diagram.

What if I hack my battery holder to make 1 battery be parallel not in series?
That should give me 3V top voltage. But the 1 battery that will be connected parallel will give more juice anyway.

Then I can use ZXCS300 like in this datasheet
http://www.diodes.com/zetex/_pdfs/3.0/appnotes/apps/an65.pdf

I have my part list like this:

ZXSC310 | SOT23-5
FMMT617 transistor NPN 15 V | SOT23
Schottky diode SMC 15 V 3 A, 30BQ015PBF

Not sure what resistor I need for 700mA current:
RESISTOR, SMD 1% 25 mΩ 2W 20ppm/°C
Resistor SMD up to 20 W 16 mΩ 0.5 W ±1 % x2 to make 32mΩ

Is this inductor OK:
Inductor, SMD 22 ĄH 1.76 A 8X7X5 mm

What capacitor C1 and C2 I should use ?

If however I' will be unable to get desirable results from this driver then perhaps forum members will give me more clues as what to use.

 

[smilem]

Oh and I forgot to ask, I read somewhere that when working with pulsating voltage like this ZCX310 driver IC it's hard to measure current correctly.

Is this true? I have access to good quality multimeter U1242A.
Will it work OK on measuring current and voltage for this circuit?

 

[VegasF6]

You can use one dummy cell in your 3x series battery holder with alkaline or nimh, and a boost circuit.

Or you could use 2x and a dummy cell or 3x LiCo battery and higher voltage step down converter such as this one:
http://www.dealextreme.com/details.dx/sku.26110


Have you read data sheet for amc7135? It doesn't work the way you describe, and is no comparison for Joule Thief.
http://www.micro-bridge.com/data/ADD/AMC7135.pdf


I am all for DIY but is this really worth it for one cheap chinese torch that uses 3xAA or 3xAAA battery in series? I don't know of a single high end flashlight that uses that configuration.

 

[smilem]

You can use one dummy cell in your 3x series battery holder with alkaline or nimh, and a boost circuit.

Or you could use 2x and a dummy cell or 3x LiCo battery and higher voltage step down converter such as this one:
http://www.dealextreme.com/details.dx/sku.26110
Well how do I make it output 700mA and not 1A? The components used are low quality for that price? That's really cheap.

Have you read data sheet for amc7135? It doesn't work the way you describe, and is no comparison for Joule Thief.
http://www.micro-bridge.com/data/ADD/AMC7135.pdf
Perhaps you misunderstood me. I ran 3AAA batteries with joule thief and with my china made torch that has amc7135. The torch was better.
Perhaps my joule thief is not as efficient as I wanted it to be. I know amc7135 can't light a LED if I use 1 AAA battery.

I am all for DIY but is this really worth it for one cheap chinese torch that uses 3xAA or 3xAAA battery in series? I don't know of a single high end flashlight that uses that configuration.
The torch I'm making is not china made, the LED is replaced with is 3W 180lumen 700mA, and I try to build the LED driver now

Is the end if it will be more expensive than china made so be it, I know it will not be worse quality. And you really cant buy brand name torch for 12$ (thats how much I estimate my project cost), at least where I live.

 

[VegasF6]

Well how do I make it output 700mA and not 1A? The components used are low quality for that price? That's really cheap.

Yes, that board is really cheap, and quite popular. The components in my opinion are quite good. I mean, it won't compare to some of the first notch boards some of our members make, but really, it doesn' suck. Besides this forum, I have seen it used quite a bit on several other forums as well, mountain bike, planet hid, etc.
Here is a handy link about modifying the output of the driver.
http://www.candlepowerforums.com/vb/showpost.php?p=2800471&postcount=138

Perhaps you misunderstood me. I ran 3AAA batteries with joule thief and with my china made torch that has amc7135. The torch was better.
Perhaps my joule thief is not as efficient as I wanted it to be. I know amc7135 can't light a LED if I use 1 AAA battery.

Yes, I am not quite following what you mean. In my experience the joule thief circuits are meant for very low current, not for power leds. Perhaps you made a variation I am not familiar with.

The torch I'm making is not china made, the LED is replaced with is 3W 180lumen 700mA, and I try to build the LED driver now

I can't think when I have ever seen that Avago led used in a portable lighting application. Should be very interesting to see your results. The price is quite good. I have seen the Avago Moonstone LED in fixed lighting.
How is the lighting pattern with your reflector or optic? Does it give a nice smooth beam?

 

[MikeAusC]

. . .
Power source is 1.5V batteries x3 = 4.5Volts.

I would like to use ZXSC300 because it works up to 0.8V and I don't want to waste any power from my batteries

http://imageshack.us

You don't realistically gain anything by discharging 4.5 volt alakaline batteries to 0.3 volt per cell.

The "bucket analogy" seems to mislead people to think that a 1.5 volt battery still has 50% of its capacity at 0.75 volts.

There is so little energy left below 1 volt cell, you might as well use a driver designed to operate from 4.5 to 3 volts input. You could then safely use it with one LiIon cell.

 

[smilem]

Well decided to use sxcs300 so it it doesn't work may you suggest something better but not very expensive?

The beam output from lead is better because it is bigger than luxeon star leds.

I also would like to repeat my question about C1 and C2 what type / size should I use?