Specifications

4.3 AC/DC Power Supply
The implementation shown in Appendix B is the reference design of a 3.6V AC/DC
tor from National Semiconductors. The input voltage can be between
4.3.1 Specifications
flyback regula
85VAC to 265VAC. For more information on the design please contact National
Semiconductors.
Parameter Condition Limit Unit
VIN
min
85 VAC
VIN
max
265 VAC
VOUT 500mA (2.5A peak) 3.65 VDC
Switching Frequency 140 KHz
4.3.2 Design Summary
This design utilizes the LM5021 AC-DC Current Mode PWM Controller to implement a
single output offline flyback switching power converter. The dc input voltage to the
converter is generated by rectifying and smoothing a 50 or 60Hz, 85 to 265V ac
mains voltage to produce a steady dc voltage of 120 to 375V.
The flyback converter is a topology in which a MOSFET and a rectifier are switched
on and off at a high frequency to successively and periodically connect a transformer
and capacitors in two (or three) topological states such that the input voltage is
changed efficiently to an output voltage of different average value and/or polarity.
During the first part of the switching cycle energy is stored in the transformer’s
agnetizing inductance by applying the input voltage across the transformer’s
rimary winding through a MOSFET Q101. In the second part of the cycle the input
oltage is disconnected from the transformer and some or all of the stored energy is
transferred from its secondary winding to a load through the output rectifier D106
and the output capacitors. This cycle keeps repeating at a frequency of 140 KHz.
m
p
v
Gx64 APPLICATION NOTE
This document is the sole and exclusive property of WAVECOM. Not to be distributed or divulged without prior written agreement.
Ce document est la propriété exclusive de WAVECOM. Il ne peut être communiqué ou divulgué à des tiers sans son autorisation préalable
Power Management
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