LM25185-Q1: Design

Thank you for your patience.

LM25185 is a PDS Flyback converter that has an integrated 42V/1.5A. The power that you need to deliver is 170V*0.6A+12V*0.5A=108W. To be able to deliver that power with a VIN=9V-16V, you need a high current MOSFET at the primary side. I recommend using LM5185 with an external switch. The external switch allows you to select a MOSFET with high current rating. Please, find attached the Calculator Design tool that I prepared for your case (Below is the summary of the most critical components). Just a heads up, with such a limited VIN range and the output power required, expect conduction losses to be high and it will affect efficiency. EMI will also be a challenge with such a high primary switching peak current.

PS: Please, do not pay attention to the efficiency plot that the calculator shows, there is something wrong with the calculations that I need to fix

Transformer: Lmag 500nH, Nps=1/20

MOSFET: 66A, >35V

Rcs: 1.5mohm, RFB: 85.3kohm

Clamp: Zener Diode 15V 0.5W, Schottky diode 1A 25V

Sec. Diode Vout1 (170V): 637V 1.8A

Sec. Diode Vout2 (12V): 47V 1.5A

Cout=10uF, Cin=40uF

LM5185-DESIGN-CALC_Frank.xlsx

Thank you.

please share the DS of the transformer to complete the schematic review.

As mentioned above, efficiency and EMI will be a challenge. I recommend using a push pull controller for this case. Push pull controller allows to deliver more power with a limited VIN. Unlike the Flyback, push pull controllers deliver power continuously through the transformer instead of storing the energy in the magnetic core of the transformer (Flyback). Below is the link for Push Pull controllers. As a personal recommendation, UCC2808A is a good candidate with its 1A gate driver current. Although VIN is limited to 14V max. 

Thank you

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