Modulation of switching signals in power converters

A control system for reducing noise in a power converter switching device, the switching device for coupling a direct current (DC) source to provide an alternating current (AC) output at a particular switching frequency, the control system comprising:

• a controller for switching the switching device in the power converter according to a modulation scheme, the controller being arranged to switch the switching device, in each switching period, between an active configurations providing a finite voltage at the AC output and an inactive configurations providing a zero voltage at the AC output;
• wherein a ratio between a total period of time in which the switching device is in the active configuration and a total period of time in which the switching device is in the inactive configuration is the same for each switching period and is determined according to a desired voltage at the AC output;
• and
• wherein, in each switching period, there are at least two time periods in which the switching device is in the inactive configuration, and a ratio between those at least two time periods is changed every switching period.

A switching power converter comprising:

• a switching device for coupling a direct current (DC) source to provide an alternating current (AC) output at a particular switching frequency;
• and
• a controller for reducing noise in the power converter by switching the switching device according to a modulation scheme, the controller being arranged to switch the switching device, in each switching period, between active configurations providing a finite voltage at the AC output and inactive configurations providing a zero voltage at the AC output;
• wherein a ratio between a total period of time in which the switching device is in the active configuration and a total period of time in which the switching device is in the inactive configuration is the same for each switching period and is determined according to a desired voltage at the AC output;
• and
• wherein, in each switching period, there are at least two time periods in which the switching device is in the inactive configuration, and a ratio between those at least two time periods is changed every switching period.