Figure 76 is a partial block diagram and schematic of the
808 Power Supply, showing the voltage regulators and
associated circuitry.
A power supply requires regulation to maintain a constant
voltage level with variations in load, AC line voltage, and
environmental conditions. Voltage regulators provide the
regulation which will enable the supply to maintain a
constant output voltage under these changing conditions.
The
Graymark
808 is voltage regulated triple power supply.
The following are the definitions of load, and line regulation:
LOAD REGULATION: Load regulation is a supply’s ability
to maintain a constant voltage or current output level with
changes in a resistive load.
increases.This is because of the internal resistance of the
power supply. When the load resistance decreases, the
load current increases, causing a proportional increase in
the voltage drop across the internal resistance of the power
supply. This results in a decrease in the voltage at the
power supply output. Refer to Fig. 78.
LINE
REGUIATION:
Line regulation is a supply’s ability to
maintain a constant voltage or current output level with
changes in the input AC line voltage.
Figure 77 shows four voltage graphs plotted with a
common X axis, representing the passage of time.The top
graph is of AC line voltage. It appears that some other large
loads on this line are being switched on and off, resulting
in variations of the AC line voltage.
If the value of FULL LOAD voltage is equal to the value
of NO LOAD voltage, the LOAD VOLTAGE REGULATION
Two power supplies are connected to this power line. One
is 0%, which is the ideal
value.This
value means the power
is unregulated, the other is a regulated power supply. Both
supply is a true voltage source, where the output voltage
of these power supplies have nominal output ratings of
15
is independent of the current drawn from the supply.
Volts DC at 300
mA.
Both power supplies are driving
identical loads. These loads periodically change between
In an UNREGULATED power supply the output voltage
no load (infinite resistance),
1/2
load (100 Ohms resistance)
decreases as the amount current drawn from the supply
.
+
4
I
4
OVER
OTO
-
CURRENT
’
’
+15vou
’
’
YiEF
-
DETECTOR
REGULATOR
6
. ,
+
,
-4
I
-
I
I
I,
T?l2
I
I
R2
?
--
fiXED
b
REGULATOR
.
.
FIG.
76
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