Patent ID: 7598718

Claim:
A DC to DC converter to convert an input voltage to an output voltage, said DC to DC converter comprising: a pair of switches comprising a high side switch and a low side switch; an inductor coupled to said pair of switches; and a controller configured to estimate a zero crossing of an inductor current through said inductor, said controller is further configured to provide a pulse width modulated (PWM) signal and a low side switch enabling signal, said low side switch responsive to said PWM signal and said low side switch enabling signal, said controller is further configured to provide a pulse width modulated (PWM) signal and a low side switch enabling signal, said controller comprising a capacitor, wherein said zero crossing of said inductor current is estimated by monitoring when a charge on said capacitor is less than a low voltage threshold, said controller including a first current source configured to provide a first current level and a second current source configured to provide a second current level, said controller further including a capacitor configured to be charged by a charging current equal to said second current level less said first current level during a first time interval, wherein said first time interval has a start time and an end time, said start time occurring when a charge level on said capacitor is substantially zero and said end time occurring when a charge level of said capacitor is greater than a charge threshold level, wherein said zero crossing of said inductor current is estimated by said start time of said first time interval.