Elenco Variable Voltage Power Supply - Manual (Page 2)

Figure 1
Simplified diagram of positive power supply
120VAC
Input
18VAC 20VDC 0 - 15V
Regulated
Output
Transformer
120V to 18V
AC to DC
Converter
Voltage
Regulator
CIRCUIT DESCRIPTION
INTRODUCTION
The XP-15 Power Supply features an output voltage variable from
0 to 15V at 0.3 ampere maximum current. The voltage is regulated
to within 0.1V when going from no load to full load. Varying the input
AC voltage from 110 to 130V will have practically no effect on the
output voltage. This is because of the specially designed IC circuit
used in the XP-15. Severe overloading or even short circuiting the
output will not damage the supply. Special turn-off circuits in the IC
sense the overload and turn off the output.
Figure 1 shows a simplified circuit diagram of the power supply. It
consists of a power transformer, a DC rectifier stage and the
regulator stage.
-1-
TRANSFORMER
The transformer T1 serves two purposes. First, it reduces the
120VAC input to 18VAC to allow the proper voltage to enter the
rectifier stage. Second, it isolates the power supply output from the
120VAC line. This prevents the user from dangerous voltage shock
should they be standing in a grounded area.
SPECIFICATIONS FOR XP-15 POWER SUPPLY
Output Voltage 0 - 15VDC
Output Current 0.3A @ 12V, 0.2A @ 15V
Load Regulation 0.1V
Line Regulation 0.1V
Ripple Max. 0.01V rms
Short Protection IC THERMO
Output Impedance 0.3 W