Non-linear semi active vibration control devices have experienced a significant development in recent years, due to their performance and advantages compared with the passive and active approaches. Pulse switching techniques, which were developed in the field of piezoelectric damping, lead to effective trade-offs between performance, simplicity and the required power supply. The control law in this method is based on triggering an inverting switch on each extremum of the produced voltage (or displacement); however, in the case of random excitation, false switching on the local maxima can reduce the efficiency overwhelmingly. A successful approach, to overcome this limitation is based on windowed statistical examination of the vibration signal to determine the optimum triggering voltage level. According to this approach, this paper presents a modified method and for the first time presents a novel circuit structure to predict the optimum trigger time of the damping switch. This circuit structure is implementable using compact analog devices which can be embedded in the vibration energy extraction system. The proposed circuit calculates statistical parameters of the displacement sensor signal then estimates the value of the threshold. Results for a cantilever beam excited by different excitation forces, such as harmonic, random samples and pulse forces are presented and compared with the numerical simulations. (C) 2011 Elsevier BM. All rights reserved.