Other Parts Discussed in Thread: PMP30104
Dear all,
in the reference design, PMP30104, a multiplied sepic capacitor charger is presented. It boost 15Vin to 420V/80mA out. I need some variations (higher input voltage, higher output voltage), and would need some advice, how to select components with different parameter. Because components with higher voltages getting bigger, more expensive and difficult to source, I like to have hints to still have a margin, but not oversize the parts.
Mosfet Q2: According to the test result(
), the mosfet see max 95V. TI selected an 150V Mosfet on this position, about 50% safety margin. For a redesign with, lets say, 30Vin, this Mosfet should be a 300V type? Would be 250V type ok, too?
Cm1-Cm5, CM7-Cm11: By guessing, the voltages on these capacitors will be 60-70V. TI choose 2.2 μF, 100 V types, X7R. 50% safety margin.
Dm1-Dm6: I thought, the voltage over the Schottky diodes are the same as over the capacitors Cmx, but the TI selected Schottky diodes are 150V types. When double input and output voltage, would 200V Schottky diodes be too weak? 300V Schottkey diodes are difficult to source, could then Ultra-fast rectifier diodes (75ns) be used instead?
TI have a wonderful software, called Power Stage Designer. Unfortunately, it not support the Multiplied sepic topology. Would be great, if this topology is supported in a future version of this software.
Thanks for your hints,
Michael
