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DLPLCR4500EVM: How to reduce current control level

sangchan na
Prodigy 10 points
Part Number: DLPLCR4500EVM

Hi, 

I'm testing DLPLCR4500EVM with our setup, but it is too bright for our setup and the minimum current is too high. Can I change the control range of current from 0.4 ~ 4 A to 0 ~ 0.2 A

For example, I want to control the current as follow; 

Current (A) = 0.0008*(LED current value)

Can I modify the EVM to meet the range? or can anybody suggest any circuit for LED driving? I think that I can use the enable and the PWM signal from J29 to control the external circuit. 

Thanks in advance. 

Sangchan Na

  • 0
    TI__Mastermind 20565 points

    Hello Sangchan,

    Welcome to E2E!

    We are discussing with the team about possible solutions. Thank you for your patience in the mean time.

    Best regards,

    Arthur Brown

  • 0
    TI__Mastermind 20565 points

    Hello Sangchan,

    Do you have a specific minimum current you would like to drive? 

    Best,

    Arthur Brown 

  • 0 in reply to Arthur Brown
    Prodigy 10 points

    Hi Brown, 

    0 is the best, but 10 mA is ok for our setup. 

    Thanks and regards, 

    Sangchan Na

  • 0 in reply to sangchan na
    TI__Mastermind 28005 points

    Sangchan,

    Thanks for the feedback. The team should be able to get back to you within the next few days.

    Regards,

    Philippe

  • +1 in reply to sangchan na
    TI__Mastermind 20565 points

    Sangchan,

    I apologize for the delay on this. I talked with one of our hardware experts.

    from the reference design for this EVM the led drive is a buck converter and a MOSFET. on the source of this MOSFET is a 1W 0.020 Ohm resistor which is the main limiter of the current driven to the LED. if you doubled this resistor value you would halve the max current. if you chose 0.1 ohm you would have 1/5th max current etc. From our experts opinion this resistor could be up to 0.5 Ohm without much cause for concern.

    however these LEDs and Buck converter are designed for high current so you may likely experience light non-linearities in trying to drive such low current from the buck into the LEDs.

    if you are not concerned with adjusting the LED brightness you could use a simple external MOSFET circuit and only use the enable signal for each color. Other wise you could design a circuit copying the reference design, but choose a regulator which is suited for driving lower currents.

    Best regards,

    Arthur Brown

  • 0 in reply to Arthur Brown
    Prodigy 10 points

    Dear Arthur,

    Thanks for the information. I will try to increase the resistor value to control the current. 

    Have a nice day!

    Thanks and regards,

    Sangchan Na