User's Manual

AT7120 Owner Manual Rev. 1.1 – March 2009 40/76
Section 7 – Power Supply
Module 4401
General Functional Description
Power supply - Module 4401 - is the switching type, configured in the topology of half bridge, having
overall efficiency above 80%. Module 4401 is responsible for the generation and distribution of
following voltage DC:
+32V FIXED
+32V RE-CONNECTABLE
+18V
-18V
+9V
Module 4401 can be connected to the electric AC network of 120Vac or 240Vac, according with internal jump
positions.
Module 4401 is self-protected against DC short-circuit. This protection acts by inhibiting the generation of
switching pulses, shutting down the power supply; 0 volts at the DC’s outputs. The output +32V RE-
CONNECTABLE is managed by the Control unit.
The re-connection command is sent to the power supply, to turn the +32V RE-CONNECTABLE on. This voltage
is responsible for feeding the 60W amplifier - Module 4407. The consumption in Amps from the +32V RE-
CONNECTABLE power supply is basically the consumption associated with the drain electrical current of the
LDMOS transistors of the amplifier. Because of this configuration, the LDMOS currents are measured at the
power supply - Module 4401.
These current measurements are routed to the control unit. In case of extreme measured values, the control unit
inhibits the +32 RE-CONNECTABLE power supply.
Module 4401 – Block Diagram
Input AC filter
The C1, C6 and TF-1 components together assemble the line filter. This filter minimizes the noise
generated by the power supply into the AC network.
The varistors V1, V2 and V3 prevent over-voltage damages potentially caused by occurrences on the
AC network.
The group of diodes D1/D4 rectifies the AC voltage from the AC network and delivers this rectified
voltage to the capacitors C9 and C10 for filtering. These capacitors could be connected in parallel or in
series, according with the set of the jumps for 120/240Vac.