A phase cut dimmer, coupled between an AC power source and a load, to control the amount of power delivered from the power source to the load, comprising: a dimmer switch to turn on and off the current from the power source to the load; the dimmer switch being an AC switch formed of a first MOSFET and a second MOSFET connected in anti-series; the two source electrodes of the MOSFETs being connected together to form a common source terminal and the two gate electrodes of the MOSFETs being connected together to form a switch control terminal; a line filter bypassing very low current at the line frequency; a rectifier to convert the AC voltage from the power source to pulsating DC voltage which is coupled to the dimmer switch; a very low power unipolar zero detector extracting a zero marker signal from the pulsating DC voltage; the unipolar zero detector comprising a voltage-controlled bleeder impedance, a comparator, a pulse generator, wherein the voltage-controlled bleeder impedance is coupled to the pulsating DC voltage whereby the bleeder impedance is controlled proportional to the instantaneous value of the voltage; the pulsating DC voltage is compared to a reference close to zero level by the comparator, triggering the pulse generator to generate the zero marker signal when the voltage is lower than the reference; a very low power adjustable timer to control the dimmer switch in synchronization with the zero marker signal.