This invention discloses a power converter with a secondary-side control, including an input circuit with one or more switches, an output circuit with an output end and a controller, and a transformer with a primary-side coil assembly connecting the switch(es) and a secondary-side coil assembly connecting the output circuit. The on/off state of the switch(es) is controlled by variations in voltage of primary-side coil assembly. The controller in the output circuit detects an output voltage and sends detected results to the primary-side coil assembly as a feedback for primary-side coil assembly to regulate the PWM or PFM action of the switch in a specific way to maintain voltage stability.