A method and apparatus are described for controlling the phase of an interleaved boost converter using cycle ring time. In an embodiment, a cycle controller generates a first drive signal to control switching of a first converter and a second drive signal to control switching of a second converter, the controller receives a first cycle signal from the first converter and a second cycle signal from the second converter, wherein the first cycle signal and the second cycle signal have a power phase time and a ringing phase time. The cycle controller determines a master ringing phase time of the first cycle signal and applies the master ringing phase time to the second cycle signal to determine a slave ringing phase time. The cycle controller generates the second drive signal in accordance with the slave ringing phase time.