TDA4605 데이터 시트보기 (PDF) - STMicroelectronics
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TDA4605 Datasheet PDF : 7 Pages
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TDA4605
FUNCTIONAL DESCRIPTION
In free running fly-back converters, the TDA4605
assumes control of a MOS power transistor and all
necessary regulation and monitoring functions.
The serial circuit of power transistor and primary
winding of the flyback transformer is connected to
the input voltage. During the switch-on period of
the transistor, energy is stored in the transformer
and during the switch-off period it is fed to the load
via the secondary winding. By varying the switch-
on time of the power transistor, the IC controls
each portion of energy transferred to the second-
ary side such that the output voltage remains near-
ly independent of load variations.
The required control information is taken from the
input voltage during the switch-on period and from
a regulation winding during the switch-off period. A
new cycle begins as soon as the energy stored in
the transformer has been totally delivered to the
secondary side.
In different load ranges, the SMPS will behave as
follows:
– No-Load Operation: The power supply unit os-
cillates in non continuous mode at a typical fre-
quency of 20 to 40kHz. Depending upon the
transformer winding and the regulated voltage di-
vider, the output voltage can be slightly above
the nominal value.
– Normal Operation: Starting from typ. 200kHz,
the switching frequency falls with increasing load
and decreasing AC voltage. The duty cycle de-
pends primarily on the AC voltage. The output
voltage is only slightly load-dependent.
– Overload Point: Maximum output power is
available at this point of the output characteris-
tics
– Overload: The energy transferred per operation
cycle is limited at the top. Therefore, the output
voltage will fall with secondary overloading.
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