| Nowadays, the power supply of microprocessors is Voltage Regulator Module (VRM), which has been the challenge and focus in the field of Power Electronics. With the great increase of the speed and integration density of microprocessors, for the future VRM ,the output voltage is getting lower and lower, while output current will dramatically increase,in the meantime, the faster transient response with higher power density is also required .All these prompt severe challenge for its efficiency. Against this background, it is significant to study the VRM with high efficiency, because it can save energy and reduce the thermal stress.In this paper, the VRM with 48 V input and 3.3 V/30 A output is the main study object and the active clamp forward converter with self-driven synchronous rectifier is chosen. Firstly, the detail operation principle of the active clamp forward converter is analyzed. At the same time ,the factor of the converter loss is introduced simply. Secondly, according to the study of the synchronous rectifier and soft-switching which can improve the efficiency, the design method of the key components are introduced in detail, including the main power switch, clamp switch, synchronous rectifier, transformer, and output filter, etc. The detailed loss estimation of the converter is described. Finally, the design method of the peak current-mode PWM controller UCC2897A, the optical coupler and the compensation circuitand is stated, at the same time, the design of the control loop is pretend completed.On the base of the theoretical analysis above, the VRM prototype with 48V input and 3.3 V/30 A output is built up. The experimental results and the analysis of results are given. The results show that the main power switch, clamp switch and synchronous rectifier have achieved ZVS and the efficiency of the converter reach as high as 95.6%, when the two synchronous rectifier are paralleled. Thus the experimental results verify the analysis above.
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