I opened my design schematic and realized I had already designed the Vpp control design. So now I have two options. I used an inductor in the first design to filter the base current of the voltage divider. In the second design, I just used an RC low pass filter to filter the base current of the transistor. This project has gone long enough that I am forgetting details of things I have already done.
I prefer the design I did last week to the earlier design. If I find the system doesn’t regulate very well, I may incorporate parts of the earlier design.
Cut in Planning:
Looking at the last schematic and schematic where I want to end up, I can see I need to remove Q4, 5, R6 and R9. I then need to attach pin 1 of the FAN5331 to Pulse. Pin 2 to GND, Pin 3 to Vps. Pin 4 and 5 to the supply side of L1. Short Q4 Pin2 to 3. Finally replace R9 with a transistor with filter to HVPulse.
Placing the new parts:
After removing the parts two transistors and two resistors, I soldered pins 4 and 5 of the FAN5331 to the end of L1 to hold it in place. I then soldered a piece of a component lead between pins 2 and 3 of Q4. I added jumper wires for Pins 1,2 and 3. I then soldered Pins 2 and 3 of the transistor to the pads of R9.
I soldered a 0.1µF capacitor to the GND side of C14 to hold it in place, and soldered the 100K and 510K resistors to it. I then soldered a jumper wire from pin 1 of the transistor to the 510K Resistor. Finally, I soldered a jumper from the 100K resistor to the base of Q5(Pin1)
I still need to test this circuit to verify linearity and see how loading affects regulation. The code is already written to allow me to do the minimum testing. Also, I don’t have a way to measure Vpp at this point, I will have to put a new voltage divider in to replace R8,9 to feedback to the ADC in the processor.
I have been looking for an adhesive that I can use on to hold components to PCBs while I am soldering. Do you know of any glues that work well for that? Would you have placed anything differently than me?