A flyback converter includes a controller integrated circuit (IC) housed in an IC package with only three terminals. The controller IC is grounded through a ground terminal. A feedback signal is received onto a power terminal. The feedback signal powers the controller IC and is derived from a voltage across an auxiliary inductor of the flyback converter. A switch terminal is coupled to an inductor switch that is turned on by a switch control signal having a frequency and a pulse width. The inductor switch controls the current that flows through a primary inductor of the flyback converter. A switch signal is received onto the switch terminal and is used to generate the inductor switch control signal. The controller IC adjusts the frequency in a constant current mode such that output current remains constant and adjusts the pulse width in a constant voltage mode such that output voltage remains constant.