In this paper, we propose a method for building the state class graph of a bounded time Petri net (TPN) as a timed automaton (TA). We consider bounded TPN, whose underlying net is not necessarily bounded. We prove that the obtained TA is timed-bisimilar to the initial TPN. The number of clocks of the automaton is much lower than with other methods available. It allows us to check real-time properties on bounded TPN with efficient TA model-checkers. We have implemented the method, and give some experimental results in this paper, illustrating the efficiency of the algorithm in terms of clock number.