We present a non-stationary model proposed for high power impulse magnetron sputtering discharges, which is based on a global description of the plasma processes. The model takes into account a typical structure of magnetron discharges by dividing the plasma volume into two zones, the magnetically confined high-density zone above the target racetrack and the bulk plasma zone, where the transport of particles onto the substrate and the chamber walls dominates. The comparisons of the calculated data with measured results for distinct experimental conditions in two different high power impulse magnetron sputtering systems show a good agreement, suggesting that all relevant plasma processes were correctly incorporated into the model equations. The model can be used to gain a more detailed insight into the complicated processes in such types of discharges and to predict the influence of various process parameters on the deposition characteristics.