Hi lads,
Having a bit of trouble understanding how exactly this works... The datasheet for the PWM chip says that PIN 8 is the Vcc and a sample circuit explains that you drop the main 320V across a few resistors to get around 18V to give the chip startup power.
However on this power supply there is a four pin inductor along the path to the Vcc pin... There is 320V on the main filter cap so it's good to there, then I measured 320V at pin 2 of the inductor. But on the other side of the inductor on pin 3 it measures 0V. I would have thought that the 320v would be dropped across R10, R11, and R12 ? There is another line coming from the right side of the schematic (Full schematic here), but I'm pretty sure that this is the RUN DC circuit for when the system is already running... Any opinions appreciated.
Having a bit of trouble understanding how exactly this works... The datasheet for the PWM chip says that PIN 8 is the Vcc and a sample circuit explains that you drop the main 320V across a few resistors to get around 18V to give the chip startup power.
However on this power supply there is a four pin inductor along the path to the Vcc pin... There is 320V on the main filter cap so it's good to there, then I measured 320V at pin 2 of the inductor. But on the other side of the inductor on pin 3 it measures 0V. I would have thought that the 320v would be dropped across R10, R11, and R12 ? There is another line coming from the right side of the schematic (Full schematic here), but I'm pretty sure that this is the RUN DC circuit for when the system is already running... Any opinions appreciated.