This paper presents a high-throughput asynchronous protocol converter between two-phase communication links and four-phase pipelined routers for asynchronous Network-on-Chip. In the proposed protocol converter, two-phase input and output signals are encoded to and decoded from the four-phase signals, respectively, by using two controllers which are attached to the router. Since the two controls are realized respectively by using only the input signal and the output signal, the "two-to-four-phase" and "four-to-two- phase" conversions are independently performed. Therefore, each conversion is completely performed without input-output dependency. As a result, the proposed protocol converter achieves an up to 77 % increase in throughput under a comparable energy consumption with respect to that of a conventional protocol converter on a Silterra 0.13-μm CMOS technology.