OVERVIEW 
11 
Series Lineup / Main Features 
Series Lineup 
 
Model  V Meter A Meter USB  Tracking Error 
GPD-3303D  3 digit  3 digit  Yes 
≤ 0.5% + 50mV of Master
GPD-3303S  5 digit  4 digit  Yes 
≤ 0.5% + 10mV of Master
Main Features 
 
Performance 
•  Low noise: Cooling fan controlled by Heatsink 
temperature 
•  Compact size, light weight 
Operation 
•  Constant Voltage / Constant Current operation
•  Tracking Series / Tracking parallel operation 
•  Output On/Off control 
•  3 outputs: 30V/3A x 2, 2.5V/3.3V/5V/3A x 1 
•  Digital panel control 
•  4 sets of panel setup save/recall 
•  Coarse and fine Voltage/Current control 
•  Software calibration 
•  Buzzer output 
•  Key lock function 
Protection 
•  Overload protection 
•  Reverse polarity protection 
Interface 
•  USB for remote control 
    GPD-3303 Series User Manual 
12 
Principle of Operation 
 
Overview 
The power supply consists of the following. 
•  AC input circuit 
•  Transformer 
•  Bias power  supply including rectifier, filter, 
pre-regulator and reference voltage source 
•  Main regulator circuit including the main 
rectifier and filter, series regulator, current 
comparator, voltage comparator, reference 
voltage amplifier, remote device and relay 
control circuit 
The block diagram below shows the circuit 
arrangement. The single phase input power is 
connected to the transformer through the input 
circuit. Details of each part are described in the 
next page. 
Block diagram