Specifications

4-8 888-2500-001 5/2/2013
WARNING: Disconnect primary power prior to servicing.
DAX-1/DAX-3
Section 4 Theory of Operation
conduction angle of the SCRs is increased, raising the DC output voltage. If the DC
output voltage increases, the conduction angle of the SCRs decreases, lowering the DC
output voltage.
Two DC bus voltages are provided by the Power Supply Controller selecting between
two sets of transformer secondary taps; these two taps provide the 300V and 200V
(variable between 80Vdc and 200Vdc for low power optimization) DC bus voltages.
The voltage regulation function is made possible by voltage feedback from the DC
output of the B+ supply. The DC voltage feedback is provided by a resistive voltage
divider, which is changed whenever a different secondary voltage tap is selected. When
a different B+ voltage is selected, the multiplexer connects the appropriate voltage
divider resistors to the DC output and the correct voltage regulation feedback voltage is
sent to the ENERPRO SCR firing board.
4.4.1.5.1 B+ Supply Enable/Disable Functions
The B+ supply is enabled and disabled via a single logic line from the main controller.
When the B+ supply is enabled the SCRs begin firing at their minimum conduction
angle and progressively fire at greater and greater conduction angles until DC output
voltage regulation is achieved; this provides a “soft-start” turn-on characteristic for the
B+ supply. When the B+ supply is disabled the SCRs are instantly disabled; this
provides the desired “soft-start/instant disable” characteristic for the B+ supply.
4.4.1.6 DC Output Filtering
The rectified AC is filtered with an L-C network in order to provide a low ripple DC
output.
4.4.2 Power Supply Controller
The Power Supply Controller Board provides the interface and control functionality for
the transmitter’s power supply. The Controller Board provides the following functions:
• Receives the power supply logic control signals from the Main Controller
• Provides the interface between the Main Controller, transformer, SCR firing board,
and rectifier assembly
• Provides feedback to the Main Controller on power supply faults
• Provides transformer secondary voltage and DC output current samples to the Main
Controller
• Provides fuse protection for the rectifiers and DC output components