Wide Input Voltage Flyback Switching Power Supply

Flyback topology is the most popular during low-power application power system, especially in during has multi-output power supply system. which was mainly due to Flyback topology simple structure,fewer components required,debugging convenience and so on. In traditional flyback topology applications, the input voltage range is generally in the 90 to 130VAC or 200 to 270VAC, At certain special applications, the need for very wide input voltage power supply to normal working,This need to study the wide input voltage switching power supply.This article design of photovoltaic energy system using solar cell auxiliary power supply for solar power, it can provide the right voltage for the control system of the photovoltaic electricity generating system. Because of the wide voltage output of the photovoltaic cells, and input voltage range from 120VDC to 850VDC, The article namely to this one practical application suffer open question set a sort of control mode, through automatically changing the operating frequency during different input voltage to set the question, so that flyback switching power supply to a wide input voltage be able to normal working. Incremental fewness component, use with fruitful.After reviewing the state of the art of DC/DC converting and analyzing the common DC/DC topology, combined with practical applications of the chosen Double Transistor Flyback Converter topology. Frequency conversion circuit is through to the input voltage the detection, using transistor cooperation with optocoupler to control the main chip with the timing resistance, in a timely to change the frequency of the main control chip to achieve. A special control chip UC3844 was used in the power system to realize the double-loop control of voltage and current, The voltage control and steady voltage output are realized by using three-terminal voltage regulator TL431 with the device UC3844, and the optical coupler PC817 is used to realize the input/output isolation and feedback.The power supply input voltage range from 120V to 850V, and output voltage has three road for + 5V and±15V. So it can provide the right voltage for the control system of the photovoltaic electricity generating system. Test results show that the designed power supply has good voltage regulation performance, and it has lower output voltage ripple, lower load adjustment rate and lower input voltage adjustment rate.