An apparatus and a method for generating a pulse width modulated, PWM, voltage doubler signal is presented The apparatus comprises a voltage source, a capacitor, an output node, a switchable circuit assembly for connecting the voltage source, the capacitor and the output node, and a controller for the switchable circuit assembly which is adapted to be switchable between a first circuit configuration in which the capacitor is connected in parallel to the voltage source so as to be chargeable by the voltage source, and a second circuit configuration in which the capacitor is connected in series between the voltage source and the output node, and wherein the control means is adapted to control the switchable circuit assembly to switch to the first circuit configuration in the first period, and to switch to the second circuit configuration in the second period.