Design Of DMA-48V/75A Switch Rectifier

This paper presents the structure, the principle and the design of DMA-48V/75A switching mode communication power system. The system consists of the AC input stage, single phase PFC, main inverter, output low-pass filter, auxiliary power supply, and load current sharing circuit, etc.The operation principle and practical design method of the PFC stage is introduced. This method is based on the theoritical analysis, but it's simplied according to the application. The system is both stable and reliable. A low power loss passive snubber is added to the Boost converter, therefore the switching losses are reduced.By the classification of the typical control method,"phase overlapped control"(POC)is proposed. Low cost, high reliability are its advantages. ZCS of the lagging leg is realized by adding a simple LCD circuit to the transformer's secondary side.System exceptions, such as over-voltage, over-current, over-temprature, DC under-voltage, etc, are dealt with by carefully disigned protection circuits. These circuits provide various functions to protect the system, including soft start, drive signals mask, and power supply shut down.By using master-slave load current sharing technich, modules can be parrallzed easily, thus capacity-expansion is very convenient.Because of the high frequency operation, this switching mode power supply have many advantages:light weight,small physical size,high reliability,etc.