VIPer53 - E Primary regulation configuration example
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5 Primary regulation configuration example
Figure 18. Off line power supply with auxiliary supply feedback
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 V
DD
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 V
DD
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
V
DD
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.
15V
VDD
OSC
DRAIN
SOURCECOMPTOVL
U1
VIPer73
R3
R4
D3
D1
C1
T1
C2
F1
R1
D2
C7
C5
C4
C6
T2
D4
C8
C10
L1
C9
R2
C3
AC IN
DC OUT
C11
10nF
R5
R6
1k
