Page 1 of 6 12345 ... LastLast
Results 1 to 10 of 57

Thread: New High side Diode driver and TEC Driver

  1. #1
    Join Date
    Jan 2009
    Location
    Germany
    Posts
    241

    Default New High side Diode driver and TEC Driver

    Hi everybody,

    quite some time ago I asked for high side laser diode driver designs and after some help from Steve built a first prototype of my driver (see http://www.photonlexicon.com/forums/...9912#post99912). In the meantime I started to construct a nice red laser for my new projector. In this process I significantly improved the old circuit and added some more features. I also designed a TEC driver. To make mounting easy I designed both new drivers to be the same size and have mounting holes.
    Now I have finished this project and thought I add the gained knowledge to the already huge amount of interesting projects on PL. I hope that it is useful to you as well.
    I provide everything needed to build these drivers on your own, including schematics, layout, partlists and even digikey order numbers . You are free to built the driver for yourself but not to sell it. If you want to use it commercially just drop me a PM, and we will find an agreement as well! If there is sufficient interest I could also try to find a manufacturer to produce the drivers and organize a groupbuy.

    So here is picture of the laser I used the drivers for:
    Attachment 15661
    Click image for larger version. 

Name:	Laser642nm300mW..jpg 
Views:	627 
Size:	177.0 KB 
ID:	15667
    Specs: 300mW 642nm mirror combined Opnext HL6385 diodes

    Specs of the Diode driver:
    High side, that means you don't have to isolate diodes which have the cathode at the case.
    Rise/Fall times: 1us 100mA->500mA
    Reference voltage to make bias current independent from supply voltage
    Input modulation voltage limiting to protect the diode
    Current limiting to prevent current peaks trough the diode
    Up to 1W can be continously burned by the power mosfet. Depending on the input voltage that means up to ca. 1A current.

    Schematic and image of LD Driver:
    Attachment 15665Attachment 15663Click image for larger version. 

Name:	LDDriverV4b..png 
Views:	749 
Size:	91.4 KB 
ID:	15668Click image for larger version. 

Name:	TreiberV4..png 
Views:	514 
Size:	743.0 KB 
ID:	15669

    The layout in the attached file is a bit different from the image. This is because after I measured the current design, I decided to increase the copper area of the mosfet for improved heat dissipation. I also added many thermal vias to efficently thransfer heat to the backside of the driver. I have not built the current layout but there should be no problems just better cooling for the mosfet.

    Schematic of the TEC driver (inspired by
    http://pagesperso-orange.fr/redlum.x...lePWM-TEC.html ):
    Attachment 15664Click image for larger version. 

Name:	TECDriverV2..png 
Views:	613 
Size:	29.1 KB 
ID:	15670

    Specs:
    10k NTC for temperature sensing
    up to 2.5A current
    up to 4.5V at 5V input
    ca. 0.1°C temperature stability

    At the end the file with the layouts:
    EagleLayouts..zip

    Have a lot of fun with the circuits!

    Andreas

    Edit: I don't know whats wrong but in the first time the images did not work and now there are strange not working links in the text.

    Last edited by andythemechanic; 04-01-2010 at 09:56. Reason: Link was not working

  2. #2
    Join Date
    Jun 2007
    Location
    Lake Geneva, WI.
    Posts
    2,704

    Default

    Nice work man! I'll have to build a couple of these and try em out.
    Thanks!
    Adam

  3. #3
    Join Date
    Feb 2010
    Location
    Sweden
    Posts
    110

    Default

    Ah, there's another one! We need a separate section on the forum to collect all this nice stuff!
    -Great work, looks nice!

  4. #4
    Join Date
    Jun 2007
    Location
    Lake Geneva, WI.
    Posts
    2,704

    Default

    Quote Originally Posted by Occularis View Post
    We need a separate section on the forum to collect all this nice stuff!
    We do have a section, It's called Photonlexicon. The whole site is filled with good content, just like this thread.

  5. #5
    Join Date
    Jul 2009
    Location
    China
    Posts
    35

    Thumbs up

    looking really nice. I want to have one for my red module.

    But what I see is that cathod drive is still the majority on this forum. Just curious if high side driver does such good and convenience, why it is so rare?

    Is there any disadvantages of high side drive? Anyone has idea?

  6. #6
    Join Date
    Jan 2006
    Location
    Switzerland
    Posts
    129

    Default

    Hi Andy,

    thanks for mentioning my site. BTW don't you run into heatsinking problems with the FAN8301? As you know I used a similar SO-8 PWM step down (the L5973D) and I had to add some copper strip for heat sinking, otherwise this thing opted out when under full load for an extended period of time, and in fact the chips do take permanent damage from overheating.

    One of the reasons why I used the MAX726 in the simple TEC driver was that it comes in a TO-220 case which makes heatsinking easy. The more modern chips tend to come in SO or TSSOP with exposed pads and I found this cumbersome. The downside of the MAX726 is that it runs only at 100khz, which makes the whole circuit larger and also PWM ripple elimination from the LD driver is less easy.

    So I am actually grateful that you found another suitable chip that runs at a higher frequency. I like to modify my existing design for a highly stable driver, as I am running out of the HY5600 Tec controllers. But as said, I am concerned about the heat-sinking capabilities of the FAN8301, which does not even have an exposed pad. Did you run this driver under full load for an extended period of time, like 1/2h or so?

    Best,
    W

  7. #7
    Join Date
    Jan 2009
    Location
    Germany
    Posts
    241

    Default

    Quote Originally Posted by RedlumX View Post
    BTW don't you run into heatsinking problems with the FAN8301?
    Hi,

    I only tested my specific Application where the Driver runs well over hours. But I don't think you can really cool a lot of heat away with the driver, it's only thought for low power diodes. One calculation example:
    Lets assume we use a TEC with R=0.8Ohms (typical small 20x20mm TEC) and run it at 2A. The power the Driver has to deliver is then R*I^2=3.2W. From the datasheet at Vo=0.8Ohm*2A=1.6V an Efficiency of 75% is assumed. When we assume that the driver has to burn all the lost energy (I think thats unrealistic because the schottky diode burns also a lot but we are on the safe side) it has to burn 0.25*3.2W=0.8W.
    Thermal resistance is from the datasheet 105°C/W so at 30°C outside we are at 0.8W*105°C/W+30°C=114°C what is still below the max. operating temperature of 125°C.
    So in this case the Driver is at the border of being usable without additional cooling. Usually for cooling one or two laser diodes there is less current needed so for this application the driver is ok.
    If one needs more power an additional cooler can be glued to the case of the IC.
    Also the IC has a thermal shutdown which, I hope, prevents damage if somebody exceeds the limits.

    So I think to see if this circuits are useful one should carefully do calculations of this kind. They where build for my purpose and there is no guarantee that they will work for other purposes.

    BTW I used a TO220 switcher in the first instance and this got awful hot and was also low switching frequency so I needed bigger inductors and caps, so this was the point I decided to use this one.

    Greetings
    Andreas

  8. #8
    Join Date
    Jan 2009
    Location
    Germany
    Posts
    241

    Default

    Quote Originally Posted by RedlumX View Post
    thanks for mentioning my site.
    Ah yes, and how could I forget, Your site is really a great collection of ideas and circuits! Thanks for making all this nice stuff available.
    Sites like your's and the open source community are the reason I also like to make my stuff publicly available. I think this is the way to learn from each other.

  9. #9
    Join Date
    Dec 2008
    Location
    veenwouden
    Posts
    2,580

    Default

    It would be nice to combine 4 drivers and a Tec driver in one board. Since a lot of PL members including me are building a quad there is quite a big demand for a quad driver with Tec support.
    Looks very professional!!!!

  10. #10
    Join Date
    Oct 2006
    Location
    Cleveland, Ohio
    Posts
    2,342

    Default

    Quote Originally Posted by edison View Post
    It would be nice to combine 4 drivers and a Tec driver in one board. Since a lot of PL members including me are building a quad there is quite a big demand for a quad driver with Tec support.
    Looks very professional!!!!
    You mean like this?:
    http://store.laserextreme.nl/catalog...products_id/74

    edit: hmm despite having the title '6 ch driver' I'm not sure that it offers 6 individual channels of modulation.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •