Single-ended forward transform switching power supply circuit diagram

Published:2011/3/29 2:14:00 Author:Nicole | Keyword: Single-ended forward transform, switching power supply | From:SeekIC

The figure is a practical circuit of single-ended forward transform switching power supply. As using optocoupler in feedback loop, so the input and output have good isolation effect. The output voltage is 5V, output current is 10A. When connected to the power supply, it will output 300V DC voltage through VD1, L1, C1 rectifier filter, added to the switch VTl directly, and give the control circuit a working voltage to make it works. During the switch VTl turns on, the secondary winding N2 of transformer T can obtain energy. The polarity make the rectifier diode VD3 conduction, and transfer to the load through L2, freewheeling diode VD4 is off. When VTl cuts off, storage inductor L2 releases energy, and the polarity in the two ends of L2 change, VD4 turns on, VD3 cuts off, L2 continues to provide energy to the load through VD4. When the output voltage Uo rises for some reasons, the current of VT4, VT5 increases. The current is coupled to VT2 through optocoupler VT3, the resistance of VT2 decreased, then the base potential of control switch VTl decreases, the duty cycle of VTl decreases, Uo declines. Conversely, when Uo declines, to adjust in the opposite direction according to the above process, then it rebounded, so as to maintain Uo stable.



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