Electronic – How does the voltage doubler work at the startup

capacitorcapacitor charginghigh voltagevoltage-doubler

I have no particular interest in power electronics but I am always impressed by such clever circuit solutions as the Greinacher voltage doubler. The idea behind it is so clear and intuitive that it can be explained in a very simple way as I have done in my answer to a similar question.

Greinacher voltage doubler visualized

There are many sources dedicated to this circuit but they (including my answer) consider its operation in steady state (during one cycle of the mains AC voltage). But how does the circuit get to this state after startup? This is the question that concerns me now…

Best Answer

The doubler bootstraps its bias voltages across the capacitors until it reaches a steady-state where the output is double the half-wave amplitude of the AC input.

You can visualize the doubler's behavior using a simulation, right here using the CircuitLab tool.

Here's an example:


simulate this circuit – Schematic created using CircuitLab

And here's a quadrupler, showing how the stages stack up:


simulate this circuit

A detail you need to consider is that the diodes have Vf drop, which will reduce the voltage the doubler can reach. I've shown Schottky types (Vf = 0.3v) to minimize this effect.