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Thread: LASER Buck Converter (60KW Pulse)

  1. #1

    LASER Buck Converter (60KW Pulse)

    I trying to design and build solid state LASER Constant Pulse Power power supply, based on Buck converter topology.

    LASER Principle.jpg

    The principle of operation of those type of LASER:
    1 Charge Capacitor bank
    2 Discharge Capacitor through Xenon flash tube
    3 Emitted light from flash tube cause Simulated emitting of light radiation in LASER media
    4 Radiated light from LASER media amplifies trough laser mirrors (resonator)
    5 Amplified light exits LASER resonator

    The most important moment for the control of the output of the LASER is controlling capacitor discharge across the flash tube.

    UNCONTROLLED DISCHARGE /Connecting flash tube directly to capacitor bank/
    If uncontrolled discharge occurs, the current, that flows through flash tube and therefore the output light achieve peak pattern across time.

    Free Discharge.jpg

    CONSTANT CURRENT DISCHARGE /Connecting flash tube to capacitor bank through current controller/
    if constant current discharge occurs through flash tube and output light stays constant, which is actually our desired effect

    Standart Discharge.jpg

    another problem comes with uncontrolled discharge and this is flash tube output light spectrum alteration, which is highly undesired effect, so this is another reason we want constant current discharge.

    Spectrum vs Current.jpg

    Since electrical discharge duration is approximately 30mS and discharge current is couple of hundreds Amps, I have to build constant current /power/ Very High Peak power Buck converter to obtain control of discharge. For most accurate feedback best approach is to use output light intensity or current through lamp. So I have find some reference designs and start to thinking...

    Buck LASER Drive.jpg

    In my design I will use current feedback, so optical output measuring system will have mostly calibration purpose.

    In summary - I have to build a Buck converter with following characteristics:

    Input Voltage 300 - 400 V

    Output Voltage* 100-200 V --> I have to make more accurate calculations
    Output Current 300-600 A
    Pulse duration 30mS
    Output ripple +/- 20% or even more

    It apparent to be very difficult design for my, so I decide to ask help from most advanced SMPS forum.

    For now i have chose some of components:
    1. IGBT Switch:BSM400GA120DLC because I have it in home and think it is suitable for application
    2. Coil 100uH Air cored - I chose air core because I thing it will be cheaper than ferromagnetic cored
    3. Capacitor bank of 20 000uF at 500V

    I have doubts for :
    1. Topology - is it good idea to use different topology since I need high reliability and not interested about efficiency
    2. Buck controller IC - specialized Buck controller, generic PWM controller, or PFC controller.
    3. Switching frequency - I suppose 20 - 40 KHz are suitable.
    4. Do I need output capacitor, since application can take huge ripple voltages?

    I will highly appreciate any help.

    Best regards
    Last edited by boriszarkov; 11-07-2017 at 02:08 PM.

  2. #2
    My last picture with project schematic has too low resolution, update it with new.
    Buck LASER Drive.jpg
    Last edited by boriszarkov; 11-07-2017 at 11:36 PM.

  3. #3
    Hello guys I already build SMPS prototype as following :
    Demonstration video

    12 to 350V Flyback.jpg
    Flyback capacitor charger 12v to 350v

    Capacitors 2 x 3800uF 400V

    Power IGBT BSM400GA120DLC

    IGBT Driver.jpg
    driver.pdf - schematic

    IGBT driver

    Inductor 150uH air core

    Buck diode.jpg
    Buck diode 2 x VS-UFB230FA60

    Current sense.jpg
    Current sense shunt resistor (current feedback)

    HV Diode.jpg
    High voltage high current output diode 100 x 6A10S

    HV Generator.jpg
    High voltage generator (for ignition impulse) 20KV

    photo detector top.jpgphoto detector bottom.jpg
    detect.pdf - schematic
    Fast photodiode optic sensor (light feedback)

    POWER.pdf - Buck converter circuit
    za rqzane.pdf - Power components placement
    Buck circuit and component placement. I plan, that components will be attached to laser cutted 2mm copper traces and some textolite for support. Coil will be made from copper sheet like this:
    Last edited by boriszarkov; 02-08-2018 at 03:42 PM.

  4. #4

    Fullbridge 2KW Capacitor charger design

    Next step is to create 2KW 220VAC to 300 - 450VDC isolated SMPS for huge capacitor bank /25000uF at 450V/ charging. Capacitors will be emptied every 1-3 sec. So SMPS must work in constant current mode. I have not experience in such powerful supplies so I will need some competent help.

    For now I try to design PFC part, based on UCC28019 CCM PFC Controller , using TI UCC28019 PFC calculator .

    Here is some 350W reference schematic: UCC28019EVM_Schematic.JPG

    My transistor will be bigger and somehow oversized SPW47N60C3 , so I include MOSFET driver TC4422 in my design , boost diode is also oversized MUR3060 . Here is my schematic in progress charger PFC.pdf Biggest problem for me is choosing a proper inductor . Calculator suggest me : minimum boost inductor value 400uH, peak current 20A , so I think something like 700uH, but I have no idea what type of core should I use - so I will appreciate any help.

    For SMPS topology I planning to use fullbridge topology , and here I have 3 major problems (don't have idea about them):

    1.Choosing best PWM controller for constant current output
    2.Designing proper secondary schematic
    3.Choosing proper ferrite core for transformer

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