Energy in a power converter is regulated by receiving a first signal representative of an output voltage and a second signal representative of a current of the power converter. An output current of the power converter is determined in response to at least one of the first and second signals. An inner maximum output power point corresponding to a first value of output voltage and a first value of output current is determined. An outer maximum output power point corresponding to a second value of output voltage and a second value of output current is determined. A maximum capability boundary between the inner maximum output power point and the outer maximum output power point is determined. A power switch is switched to regulate the output voltage and the output current of the power converter such that the maximum output power is lower than the maximum capability boundary.