Application circuit diagram of simplified VMOS switching power supply

Published:2011/5/5 7:27:00 Author:Nicole | Keyword: switching power supply, VMOS | From:SeekIC

VMOS switching power supply circuit diagram. Because of adopting voltage comparator 710, so the circuit issimpler than former. As shown, resistor R1, R2, R3 and regulator VDl, VD2 form divider regulator circuit, three groups of 5V, 6V and 18V are separated from 28V input voltage,they areused as the power supply; resistors R12, R13, capacitor C13, diodes VD6, VD7 and transistor VT3 constitute the power soft-start circuit. The moment of power turn on, the drive pulse width of VMOS tube VTl increases exponentially. when the comparator 710 cut off the drive pulse firstly, it can prevent the current of energy storage inductor too large. When the switch VTl cut down, the output voltage of switching power supply continues to rise because the current of energy storage inductor L1 still charge to the output filter capacitor C6 ~ C12. In other words, soft-start circuit make the current of energy storage inductor L1 rise slowly when the power supply start working, then to prevent output voltage from large overshoot. After the power supply into steady-state, the soft-start circuit is not work.



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