Boost converter questions ?

Discussion in 'Power Electronics' started by DarthVolta, Sep 13, 2019.

  1. DarthVolta

    Thread Starter Member

    Jan 27, 2015
    I'm using a 555 for PWM of a mosfet in a basic boost converter, just to study them and learn a few equations for them. It's Vin is 9V. The unloaded output is 110V. The duty cycle is about 1:10. But with a load of only 80-100k, the output drops to 12V, so it's not a very good BC.

    I'm using a big coil from the PFC section of a ATX PSU. It's around 800uH @100kHz, Q of +100, I wrote it down but can't find it atm.

    The PWM is near 100kHz. 1 thing that I don't get, is adjusting the duty cycle, the unloaded voltage goes up pretty steady to about 35V, then from there to 50V is pretty sensitive. Then it jumps to 105V over a very very very small increase in duty cycle. The on time is only going from say 2.5us to ~2.7us, but the jump from 53V to 112V happens there. It's on the scope and the DMM, so it's not a bad-reading. I should check other variables, to see what component is doing this. But I already wrote this.
    Last edited: Sep 13, 2019
  2. crutschow


    Mar 14, 2008
    Hard to tell what's happening without a schematic of your circuit. :rolleyes: