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TPS92314A-Provision for low and High Cut-off voltages

S Ramakrishnan
Prodigy 100 points
Other Parts Discussed in Thread: TPS92314A
Dear Sir, We are currently using TPS92314A in our street light solutions both 40W and 60W(60Vx600mA, 60Vx900mA). Is it possible to extend the power ouput to 80W960Vx1200mA)? Please confirm with changes if any.
In india the power line conditions are such that we are forced to cover a mains range of 85V to 300V AC. PI and lately Fairchild solutions offer LED driver solutions with Upper cut off at 320v and lower cut off at 70V. Please advise whether we can add these options to the standard TPS92314A driver solution and if yes, the details/schematics thereof.
We also need more clarity on the layout restrictions for a robust long term operation esp around the Anaolg and Power ground pins of the IC. Can the Analog and power grounds be shorted and connected to the Kelvin point at the root of the Sense resistor at the source of the Mosfet? where  do we connect the VCC and Aux winding grounds? IA specimen layout (Single side) would be a great help!
Regards,
S.Ramakrishnan 
  • 0
    TI__Mastermind 28655 points

    Hello,

    I assume the question is 80W(60VX1200mA).  If there are changes it will be related to your transformer design and larger parts if they are reaching a design limit such as the MOSFET or secondary side rectifier, leakage dissipation network, etc.

    There is no input to the TPS92314A that will tell the IC to shut off for high or low input voltage.  That would have to be an external disable circuit.  It could be added in series with Vcc to disconnect the TPS92314A from the bias voltage until the input conditions return.  This may have to be a low power circuit if it needs to run from the start-up resistors depending on how long it needs to be off.

    I would separate the power loop ground from the TPS92314A ground (IC reference).  Connecting it as you say would work fine as long as there isn't a long trace to the root of the sense resistor.  Aux winding should go to VCC with the capacitor close to the IC VCC and AGND.  The TPS92314A is trying to decode what the current and duty cycle are doing to regulate LED current so it's good to do the layout keeping in mind where the power loop is.

    The VCC and aux winding connections aren't as critical as long as the VCC capacitor is decoupling the IC well (meaning it's close to the VCC and AGND pins).