A power converter can include: an input circuit, including a primary winding and a primary power switch which are coupled in series between an input terminal and a first ground; at least one constant voltage output circuit, including a first secondary winding coupled with said primary winding; and at least one constant current output circuit, including a second secondary winding coupled with said primary winding, a secondary power switch, a current output port, a second rectifier circuit and a current sampling circuit. The second rectifier circuit can be coupled between the current output port and the second secondary winding, the current output port can be coupled to an LED as a load, the LED may be coupled between one end of the second secondary winding and a second ground, and the secondary power switch and the current sampling circuit can connect in series.