SERVICE INFORMATION
Figure A-1. Block Diagram
PRINCIPLES OF OPERATION
(Block Diagram Overview)
This section presents the principles of operation of the E3630A Triple Output Power Supply. Throughout this discus- sion, refer to both the block diagram of Figure A-1 and the schematic diagrams at the rear of the manual.
The two primary windings of the power transformer are con- nected in one of three different ways by setting the two slide switches mounted on the circuit board. These switches select one of the nominal ac input voltages for which the supply is designed: 100 V, 115 V, or 230 V.
The transformer secondaries, together with rectifiers and capacitor filters, provide raw dc for the three output regulator circuits and for another regulator that provides reference and bias voltages to the output regulators.
By comparing its output to a high-stability reference, the 0 to +6-volt regulator holds its output voltage at the value deter- mined by a front panel control. Any error in the actual output as compared to the desired output is amplified by an opera- tional amplifier and applied as feedback to control the con- duction of a series regulator transistor. As a result, the voltage across the series transistor varies so as to hold the output voltage constant at the desired level. The high gain of the voltage comparison amplifier and the stability of the reference voltage ensure that input voltage or load current variations have little effect on the output voltage.
The 0 to +6-volt output is protected by a current foldback lim- iter to minimize dissipation in the series regulator transistor during overloads. In a current foldback circuit, the current limit depends on the output terminal voltage. The current limit ranges from 2.75 A ± 5% at 6 volts to 1 A ± 15% with the out- put shorted. The operating region of the +6-volt regulator out-
