An electrical to optical efficiency of 5% has been demonstrated in an x‐ray preionized XeCl discharge laser using an improved prepulse‐mainpulse circuit, based on resonant charging of the peaking capacitor. In contrast to known prepulse‐mainpulse circuits, the new scheme has no time delay between prepulse and mainpulse nor a voltage reversal on the electrodes. We present three possible configurations of the scheme and one of them has been realized for demonstrating its high‐efficiency capabilities.