A modulated power supply comprises a converter having a primary power switching
device and a secondary power switching device. The outputs of the primary and secondary
power switching devices are combined to provide an output. A controller controls
operation of the switching devices in response to a modulating input signal. Only
the primary power switching device is operated while a property of the input signal
lies within a first predetermined range and both the primary and the secondary
power switching devices are operated while the property of the input signal lies
outside the first predetermined range. This can reduce switching losses in comparison
to operating the full array of switches. This is particularly well-suited to peaky
signals. The property of the modulating input signal which causes the controller
to bring secondary power switching devices into operation can be amplitude or rate
of change of amplitude.
