Development Of A Switching Mode Powers Supply Of AC/DC To DC With Super-wide Input Voltage Range For Process Instruments

Power-supply module is an important part of the process instruments, and its function is converting the power supply voltage provided by application site into a DC voltage that is required by the process instruments. In the domestic, all the enterprises cannot provide a power-supply module that adapts to the different form and scope of the input voltage. So it is not convenient to the user. What is worse, the process instruments will be damaged if its power-supply module is selected incorrectly.For this reason, the application background and technical difficulty are analyzed, a two-stage cascaded circuit topology consisting of boost converter and flyback converter circuits is designed, and a switching mode power supply of AC/DC to DC with a range of 85-265VAC and 18-100VDC is developed in this paper. This switching mode power supply of AC/DC to DC includes an input protection and filter circuit, a boost converter circuit, a flyback converter circuit, an auxiliary power supply and control circuit and two pulse width modulation (PWM) regulator circuits. The two-stage circuit topology, circuit switching point, auxiliary power supply and switching mode are selected reasonably to ensure the switching power supple high efficiency and great power output.In order to evaluate the performance of this power-supply, some experiment test are conducted, including the output voltage accuracy, the output voltage ripple, the voltage regulation, the load regulation and the efficiency. The result shows that, in the whole range of the input voltage, the output voltage accuracy is better than 1%, the output voltage ripple is less than 1%, the voltage regulation is less than 1%, the load regulation of this module is less than 1%, and the efficiency is more than 70% under the rated load. In order to apply this power-supply to the Coriolis Mass Flowmeteris (CMF), the temperature experiments are performed, which suggests that this power-supply can work well under the temperature of 55 ℃. When used as the power of the CMF, the whole temperature of the transmitter is within the normal operating temperature range, and the transmitter can work normally.