Tool/software:
Dear team,
I am considering using the LM25185-Q1 for an application (Dual Switch Flyback Converter) with a high voltage input range of 600V to 1000V. To achieve this, I plan to use a voltage divider for the Vin pin. I would like to confirm if this approach will affect the regulation and efficiency of the controller.
Could you please provide any insights or recommendations regarding this setup? Your expertise and advice would be greatly appreciated.
Thank you for your assistance.
Hi Anwar,
I dont recommend using LM25185-Q1 for this application because of the followign reasons.
VINP pin: This pin should never exceeds 42V. Even though you might connect a very high resistance (Mohm) from input line to this pin to limit the voltage seen at VINP, when the device is in shutdown mode, the current at this pin decreases to a very low value (1.7uA), which might cause high voltage seen at this pin and potentially damage the device.
FB pin: This pin should never exceed 42V. This pin is connected at the switching node through a resistor Rfb, which generates a voltage drop with the feedback current (100uA typical value when Rset=100kohm). In your case, SW node will see very high voltages SW=VIN_max+Vout*Nps+Clamp and the voltage at the FB pin will exceed recommended limits. Even though you might think on icnreasing its value to limti the volte, Rfb can not do that because it sets Vout DC value (equation below).
I recommend selecting a HV Flyback controller. You can check option here AC/DC & DC/DC controllers (external FET) | TI.com
Thank you
