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Large output ripple in TPS63020 LED driver simulation

Daniel Kuo
Prodigy 120 points
Other Parts Discussed in Thread: TPS63020, INA193, TINA-TI, INA199

Hi All,

I am currently designing a LED driver using the TPS63020, and I am encountering some issues when simulating the TINA spice model.  The TPS63020 seems to develop large output ripple when driving a high-current LED.  The LED draws 4.5V at 1.5A, and power is supplied from a single Li-ion cell (2.7-4.2Vin).  The output needs to be current regulated, so I added the INA193 current sense amplifier as described in pages 3-4 of the article "Different Methods to Drive LEDs Using TPS630xx Buck-Boost Converters".  Here is my schematic diagram:

 

 

When I attached the LED to the output, the TPS63020 output became unstable and ended up with nearly 500mA of ripple current going into the LED.  This amount of ripple seems unusually large and exceeds the maximum ratings for the LED.  Interestingly, the simulation works fine when driving a resistive load at the same voltage and current.  However, when I replace the resistor with a LED, the output becomes unacceptable.

Waveforms when driving a 3Ω resistor:

Waveforms when driving the LED:

So far I've tried the following without success:

  • Increasing input voltage (2.7v, 3.6v, 4.2v)
  • Varying the inductor value (1.5u, 2.2u, 3.3u, 4.7u)
  • Increasing output capacitance (With about 65uF of capacitance, the ripple suddenly disappeared.  However, this is more capacitance than I would like to use due to PCB space constraints)
  • Adding 0.1uF bypass capacitor to INA193 V+ pin
  • Adding 1nF bypass capacitor to INA193 output

I have attached the simulation waveforms along with the TINA-TI model.  Any help would be appreciated.

Thank you,

Daniel Kuo

 

 

Waveforms + TINA Model.zip
  • 0
    TI__Guru* 75756 points

     

    I have not tried your simulation but there have been several attempts to use the TPS63020 combined with INA193 in an LED driver application.  Stability and oscillations have been common and attempts to stabilize the circuit have been mixed.  

    The circuit with a grounded sense resistor has proven more successful and would be the most reliable approach.

     

  • 0 in reply to Bill Johns
    Prodigy 235 points

    I know this is an old post, but I was wondering if anyone got this to work.  I have a working solution, at least in simulation form that seems to solve the oscillation problem quite well.  I would like to use an INA199 instead of the INA193, however.  The problem is that I can't find a TINA-TI component model for the INA199.  Does anyone know where I can get a TINA-TI model for the INA199?