• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 28 subscribers
  • Views 2002 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

External LED driver for DLP LEDs

Aamir Abbasi
Intellectual 445 points
Other Parts Discussed in Thread: DLPC350

Dear Experts,

I want to use an external LED driver to control the flickering of LEDs of the DLP LightCrafter.

The DLP LightCrafter Manual describe to connect an external light crafter on connector 15 of the EVM like this;

15. External LED driver connector: Install a jumper in J30 to disable the DLP LightCrafter 4500 LED drivers and set jumper J28 for 3.3-V or 1.8-V supply. Then use this connector to control an external LED driver board to power the LEDs of the DLP LightCrafter 4500 light engine or external light engine. 

 


Where can I get the pin configuration of this connector 15? Which LED driver do I have to use? From what I understood, it has to be a constant voltage LED driver, right? Can I use an Arduino to drive the LEDs of the lightcrafter by sending a PWM pulse?

Looking forward to your reply.

Best,

Aamir

  • 0
    Intellectual 445 points
    Hey Experts,

    Can anyone from the TI answer my question? It's urgent!!!

    Thanks,
  • 0 in reply to Aamir Abbasi
    TI__Expert 6995 points

    Aamir,

    To use and external LED driver, you install a jumper in J30. In J29 (which seems to be missing pinout description on the LightCrafter 4500 User's Guide), the LED enables (GRN_LED_EN_CON, RED_LED_EN_CON, and BLU_LED_EN_CON) and LED PWM signals (GRN_LED_PWM_CON, RED_LED_PWM_CON, and BLU_LED_PWM_CON) are available on J29. You can see the pinout of this connector on the LightCrafter 4500 schematic. This connector also routes the 12V supply from the power connector to this header. You can use this supply to drive up to 5A total current to an external LED driver. 

    As far as external LED driver, we do not offer a ready to use LED driver board. The best match is an LED driver that operates with a 12V supply and supplies up to 5A total current to the LEDs. This driver uses as input three LED enable signals and three PWM signals. TI has a reference design available for implementation:

    Best regards,
    Pedro

  • 0
    TI__Expert 6995 points

    Amir,

    The LED enables (GRN_LED_EN, RED_LED_EN, and BLU_LED_EN) and LED PWM signals (GRN_LED_PWM, RED_LED_PWM, and BLU_LED_PWM) are driven from the DLPC350 and are output of the DLPC350 to the LED driver circuitry. They are not to be driven externally by another board like the Arduino. The DLPC350 synchronizes these signals with the patterns sent to the DMD. If they were to be driven externally by another processor, they will not be in sync to the patterns sent to the DMD, and this you will be illuminating the DMD when patterns are switching or no pattern is displayed.

    The LED driver is a constant current driver. The PWM signals serve to control the current in combination with the sense resistor R210, R221, and R232. For more description on how the LED driver operates, see this post.

    Best regards,

     Pedro

  • 0 in reply to PedroGelabert
    Intellectual 445 points
    Dear Pedro,

    Thanks for your detailed reply. In my application I want to control the flicking of LightCrafter4500's LEDs in synchrony with an external device which generates 5V TTL/PWM pulses. In other words, whenever the TTL/PWM is high a predefined LED should turn on. I will mainly use blue LED to start with. I am using my DLP as a second screen and the idea is to send an image over HDMI to the DLP and then control it's display by driving the blue LED into on an off state. I want to do this in order to achieve very high refresh rates.

    From what you are telling me, the LED enables and LED PWM signals are generated by DLPC350, then how can I use an external LED driver to control the flicking of LightCrafter4500's LEDs? Is there a way to feed these TTL signals to DLPC350?

    Or is there any other way to do what I am proposing?

    Best Regards,
    Aamir
  • 0 in reply to Aamir Abbasi
    TI__Expert 6995 points
    Aamir,

    If you have an external LED driver, the DLPC350 outputs control the LED PWM and LED enables. These signals are outputs, not inputs to the DLPC350. These signals are used to modulate the LED current and select the correct LED when the DLPC350 sends the image to the DMD. Given the time sequential nature of the DMD modulation for the different colors, an external device will not be in sync with the images sent to the DMD by the DLPC350.

    You can have an external LED driver that drives the current of the LightCrafter 4500 LEDs, but this driver needs as input the LED enable and LED PWM signals from the DLPC350. The DLPC350 will send the red, green, and blue images sequentially to the DMD and control these signals to sync with the data sent to the DMD. If an external device pulses these signals, there will be no synchronization with the image displayed on the DMD.

    However, the LightCrafter 4500 offers a pattern mode that takes a trigger input to display the next pattern (TRIG1_IN_CON on J11) and another signal for the start of the pattern (TRIG2_IN_CON on J11). You can use these signals to have an external device sequence and trigger the patterns displayed by the LightCrafter. J10 and J12 control the voltage supply of these input pins.