A circuit arrangement for switched boundary mode power conversion, a corresponding signal processor and a method of switched boundary mode power conversion are provided. The circuit arrangement comprises an input for receiving an input voltage from a power supply, an output to provide an output voltage to a load, an energy storage device, a controllable switching device, and a signal processor. The signal processor is connected to the controllable switching device and being configured for zero-current switching of the switching device. The signal processor is further configured to determine an on-time period for the switching device in one or more switching cycles based on the output voltage and the output of a crossover frequency control module to provide an improved transient response characteristic of the circuit arrangement.