For microprocessors used in real-time embedded systems, minimising power consumption is difficult due to the timing constraints. Dynamic voltage scaling (DVS) has been incorporated into modern microprocessors as a promising technique for exploring the trade-off between energy consumption and system performance. However, it remains a challenge to realise the potential of DVS in unpredictable environments, where the system workload cannot be accurately known. By addressing system-level power-aware design for DVS-enabled embedded controllers, an analytical model has been established for the DVS system that encompasses multiple real-time control tasks. From this model, a feedback control based approach to power management is developed to reduce dynamic power consumption, while achieving good application performance. With this approach, the unpredictability and variability of task execution times can be attacked. Thanks to the use of feedback control theory, predictable performance of the DVS system is achieved, which is favourable to real-time applications. Extensive simulations are conducted to evaluate the performance of the proposed approach.