VIPER53-E View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'VIPER53-E' PDF : 36 Pages View PDF
VIPer53 - E
Primary regulation configuration example
5
Primary regulation configuration example
Figure 18. Off line power supply with auxiliary supply feedback
F1
AC IN
C1
T1
R1
D1
C2
U1
VIPer73
R3
VDD
OSC
15V
C4
TOVL
R4
DRAIN
COMP SOURCE
R6
1k
R5
C5
C11
10nF
C6
C7
R2
C3
D2
D3
T2
L1
D4
C8 C9
C10
DC OUT
The schematic on Figure 18 delivers a fixed output voltage by using the internal error
amplifier of the device in a primary feedback configuration. The primary auxiliary winding
provides a voltage to the VDD pin, and is automatically regulated at 15V, due to the internal
error amplifier connected to this pin. The secondary voltage has to be adjusted through the
turn ratio of the transformer between auxiliary and secondary.
The error amplifier of the VIPer53 is a transconductance type: its output is a current
proportional to the difference of voltage between the VDD pin and the internally trimmed 15V
reference (i.e., the error voltage). As the transconductance value is set at a relatively low
value to control the overall loop gain and ensure stability, this current has to be integrated by
a capacitor (C7 in Figure 18). When the steady state operation is reached, this capacitor
blocks any DC current from the COMP pin and imposes a “nil” error voltage. Therefore, the
VDD voltage is accurately regulated to 15V.
This results in a good load regulation, which depends only on transformer coupling and
output diodes impedance. The current mode structure takes care of all incoming voltage
changes, thus providing at the same time an excellent line regulation.
15/36
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