Reducing the power consumption of packet switches is becoming increasingly significant to future networks. However, previous research all focused on reducing power in crossbar-based switches, which is either complex or not effective, especially in some extreme cases. This paper proposes to leverage the dynamic voltage and frequency scaling (DVFS) technique in the buffered crossbar-based switches, which is more flexible and simple. The basic idea is to decrease the working frequencies of the crosspoint buffers while still preserving the maximum throughput and the satisfactory delay. Traffic estimators are used at the input and output ports to estimate the traffic arrival rates, based on which the power controller can adjust the working frequencies of the crosspoint buffers at a fine-grained level. Simulation results show that the scheme is effective.