High voltage Dickson charge pump switching

Question

I am working on a circuit based on the LT1930 (DC634A) to boost input voltage between 30 and 90V.

I would like to take this boosted voltage and double it via a Dickson charge pump to the required ~160V.

This would allow for a variable voltage output between 60-180V. The current draw from this boosted supply is very low, ~1uA.

A logic level PWM signal will drive the Dickson charge pump.

I am having difficulty figuring out how to drive the boosted voltage through the C1 based on the PWM clock. I have setup a NPN driven by the PWM signal to switch a PNP MOSFET to high side switch the boosted HV.

When I run simulations, the output voltage does not double.

R1 and R2 are set to give a Vgs ~10V, but then this causes the drain on the FET to only vary between 80 and 70V.

I am open to suggestions, including completely wiping this circuit and using something else to generate a controllable ~100-180V.

Answer 1

You already have nice high-frequency (2.2MHz) AC at the converter chip SW terminal.

Try adding 2 or 3 more stages to the converter and 2 stages to the feedback divider. Each converter stage is 2 diodes, one resistor and 2 capacitors. Each feedback stage is 35.7K in parallel with 150nF.

Obviously you'll have to increase the voltage rating on C7 as well.