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NCP1529 Driver For RED LASER DIODES - What do you think?
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rhd
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You're going to have to explain that one, because I'm not sold.
1) Why would constant voltage be more efficient than constant current.
2) Why would it be any safer to run a RED or IR with constant voltage than a BR?
In fact, now is a great time for this:
Constant Current vs. Constant Voltage in use with Laser Diodes - YouTube
foulmist
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rhd thanks for the video I would have included it myself.
I am for constant current all the way in. When constant voltage is used current will change (increase more likely) with temperatures. If the driver or diode exceeds a certain temp the current will rise keeping the voltage the same and thus will kill the diode.
I must agree though that efficiency might be better with a constant voltage. I have managed to suck 1A out of LM3410 in constant voltage mode. But in constant current I could only get about 700mA tops. I am talking about the same output voltage here.
EDIT: I guess that's why Dr.Lava wired his IC on the flex drive as constant voltage output and then regulate the current with the INA regulator.
BUT constant current is what laser diodes need.
It's been tested many times. If I receive a free sample of the driver I will confirm this (unless the driver is really special and doesn't do that)
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Hi laserpointerforums.com
Me from that russian site too.
Nice to meet you.
Me from that russian site too.
Nice to meet you.
The fact is, that different diodes have different volt ampere characteristic and thermal stability. The most linear are red 660nm, so the constant voltage driver might be perfect. But 405nm and 445nm diodes are not linear and certainly require constant current drivers.
rhd
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I think the concern relates less to whether the relationship is linear, and more to whether the Vf curve itself is steep or relatively flat. A flat Vf curve will give you less security re: current, when you're regulating voltage.
Voltage reg is just the wrong way to go. I'll take diode safety over an extra 10% of driver efficiency ANY day.
benmwv
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What I want to know is
A. Does it have a max current limit that is safe for red diodes (I assume we are talking about lpc-815/826)?
B. How do you set the current? You can't use a test load because it's constant voltage, so do you just set it with your multimeter in current mode in series with the diode? This won't work well either simply because of the way the meter measures current it drops some voltage. It may not drop much voltage, but it will drop enough to change the current once you hook it straight up to the diode.
@foulmist
What input and output voltages were you using with the lm3410?
I could get 1.2A with a load a bit over 5v in constant current.
A. Does it have a max current limit that is safe for red diodes (I assume we are talking about lpc-815/826)?
B. How do you set the current? You can't use a test load because it's constant voltage, so do you just set it with your multimeter in current mode in series with the diode? This won't work well either simply because of the way the meter measures current it drops some voltage. It may not drop much voltage, but it will drop enough to change the current once you hook it straight up to the diode.
@foulmist
What input and output voltages were you using with the lm3410?
I could get 1.2A with a load a bit over 5v in constant current.
rhd
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It seems very strange to me that they would go to the trouble of adding THREE additional ICs simply for the battery monitor *frosting*, yet not bother to make this a proper current regulating driver with the addition of just ONE further IC.
foulmist
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I always use 3.6V/3.7V as input voltage as this is the Li-Ion battery nominal operating voltage. :beer:
Btw Happy New Year to all! :beer:
-Tom
Red LDs have rather stable current-voltage characteristic that allow to supply its with voltage. Also, red LDs consume lower current under undercooling. It means that risk of LD’s death becomes lower, because its efficiently and radiated power increase under frost. Though, this is not considerable changes. But, we still have the main advantage of supplying with voltage: absence of current sensor that dissipates the power; stable work of stabilizer that was created for voltage stability; we can use soft start; etc.
We use this driver more than 3 years. Practice shows that Red LDs like this type of supply. Also, IR LDs 780nm like too.
BR LDs have high temperature instability of current-voltage characteristic. Current will change high, so high that LD will become into sell-heating and die. Therefore, BR LDs need supply with current. We can use a little back-coupling with voltage for thermal stabilization of BR LDs’ radiated power. These principles were implemented in our driver for BR LDs. Its name is Indigo. In this time, converter’s effectiveness is higher at the expense of voltage dip considerable decreases at current setting resistor; we can use soft start; etc.
A main sense of this video is decreasing voltage with increasing temperature of LED. It isn’t a problem for red LD in pointers. We use constant current driver for supply Red LDs in projectors. But, this is another story.
No, it doesn’t. But, we make measurements of popular LDs and recommends current and voltage for them. For example, we recommend 2.95V for 815 and 2.73V for 826. It means that LDs will work 100 hours in laser pointer.
We use current-voltage characteristic for it.
By the way, we can. There is a possibility to set a current in Inferno.
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Li-Po has voltage range from 4.2V to 2.8V during a supply. :beer:
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foulmist
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Today I received the Inferno drive from HTV ) and it's time for the review which I promised. :beer: click here
) and it's time for the review which I promised. :beer: click here
