Dual Stage Driver

Hi,this driver will not be interesting people who can buy special purpose driver for LD.This driver contains parts that are cheap and easily obtainable in the whole world.This driver will be interesting people who have only three battery(3.6v) or only single li-ion(3.7V) and cant find driver that work on such small voltage difference and voltage drop.If you build this driver with SMD components dimensions in double layer PCB are around 20x20mm with height of 8-10mm depending of used components.

Characteristics of this driver are:

Input voltage 3-7V.
Output voltage 1.25-10.7V
Output current: 1A(Extended to 1.5A,read text).
Efficiency 80-87%.

First stage of this driver is MC34063 Boost converter that step up voltage from for example 3.6V to 5V.Second stage is LDO regulator which step down 5V to 3V or lower for laser diode.

Calibration is pretty easy.First put both trimmer in middle position.Example nr.1 If your input voltage is for example 3.6V drive trimmer R2 to 5V(if you go over 5V power dispassion will be bigger on LDO regulator and efficiency is decreased).Example nr.2 If you input voltage is 7V set trimmer R2 to 10V which is maximal allowed input voltage of LM1117.When you set R2 trimmer, then adjust final output voltage to laser diode with R3 trimmer.
LDO regulator is connected to regulate voltage NOT current because to maximize efficiency.If you have good cooler for laser diode they will not pull more current and can certainly work(I have laser pointer with LM1117 with voltage regulation and they work without any problems until have good cooling)

If you need more current connect two LM1117 in parallel and current will be 1.5A(which is maximal current for MC34063).


That all what I can say about this driver.I hope they will help someone.

Its an interesting approach, but the efficiency is for the 34063 part only - the loss in the linear regulator will be much greater reducing the overal efficiency to 50-60% or so (depending on output voltage mostly).

It might be possible to tweak the feedback loop of the 34063 to make it operate in constant current mode - i have not attempted this, but it should not be that difficult as a constant 1.25 volt is maintained here by the circuit.

You could simply add a sense resistor to the cathode end of the diode, but for flashlights and such this would mean both positive and negative laser diode leads need to be isolated from the case. Fine for 445/405's, no so good for dvd reds.

MC34063 can work in current sense mode if you put low value resistor between pins 6 and 7.But I left out due to the greater efficiency.

Nice ckt you have come up with, thanks for sharing :beer:

I would set up the LM1117 to regulate Current rather
than Voltage as you show it...


Jerry

You can limit current on two ways.First and badly way to reconnect LM1117 to current regulation,but i dont know that trimmer can handle 1A.Second way is the best, put low value resistor between pin 6 and 7 on MC34063.

Here is the calculator that calculate resistance for current resistor in MC34063.

MC34063 Step Up/Down/Inverting Switching Regulator - Calculator

Hello, Im sorry tfor reviving this topic, but I fried about 15 leds trying to make LED work with 34063.
Nevermind that, I have about 100 dvd writers that are broken lying around.
What is very confusing for me is that I boufht cheap car charger that is based on 34064 and it outputs about 5.3 Volts and 500mA.
I know it is high current output for DVD diode but anyway I hooked one diode that was mounted in aixis housing adn it worked flawlesly.
Then I hooked another diode same as the one that worked and it instantly fried. Input voltage was two LiIon batteries (8.2V in that specific case). After first diode not even one of the 15 diodes worked.
Only difference is that other diodes werent in the aixiz housing, but I think that it does not need to be if I power diode for few seconds, am I right?

Then I made that 34063 to put out lover voltage, it was 4.3 Volts, and 130mA, hooked up one diode and it worked. BUT when I turned off the diode and then back on It fried again.

Can we use JUST 34064 as the driver without additional voltage or current regulators at all. I mean I used it on one diode and with high current output, why not again on another one?:drool:

Check your merged everything right.MC34063 behaves strangely if you chose the wrong coil and frequency.Find above post for calculation.
In my latest project with blueray laser diode i used MC34063 to step down from 9V to 4.8V,@200mA.
On image is that driver.

Not being in the aixiz modules makes a lot of a difference: the laser diode housing is tiny, very low heat capacity, and will overheat literally in seconds even if you running it a proper power.

I would suggest you build a test load to see what your driver is actually outputting to the diodes though. If it blasts out 500 mA, i'm sure you'll keep on killing them every single time regardless of if they are in a module or not.

Guys, I dont know how I figured it out but I was doing things very stupid way, that car charger was ON every time I power on diode. When I turned of that car charger and connected the diode. Then diodes work flawlesly! It was some high open circuit voltage that killed LEDs, I guess so...

EXO I see you are using mc34063 for stepping down can you post component values you are using for 4.8V @ 200mA.