Ac/Dc Power Supply; Specifications; Design Summary - Wavecom Gx64 Application Note

4.3

AC/DC Power Supply

The implementation shown in Appendix B is the reference design of a 3.6V AC/DC
flyback regula
85VAC to 265VAC.
Semiconductors.
4.3.1

Specifications

Switching Frequency
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
m agnetizing inductance by applying the input voltage across the transformer's
p rimary winding through a MOSFET Q101. In the second part of the cycle the input
v 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.
Gx64 APPLICATION NOTE
Power Management
Page: 25/30
tor from National Semiconductors. The input voltage can be between
For more information on the design please contact National
Parameter Condition
VIN
min
VIN
max
VOUT 500mA (2.5A peak)
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Ce document est la propriété exclusive de WAVECOM. Il ne peut être communiqué ou divulgué à des tiers sans son autorisation préalable
Limit Unit
85 VAC
265 VAC
3.65 VDC
140 KHz