R.V.R. Elettronica PJRL250, Техническое руководство

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PJRL250 Technical and Maintenance Manual
R.V.R. Elettronica S.r.l. (Bo) Pag. 14
ELECTRICAL DESCRIPTION
This section describes the overall working theory of the PJRL250.
For case of description the amplifier is subdivided into subassemblies that
will be discussed in detail below.
The block diagram is illustrated in Fig.3.
2.1 POWER SUPPLY
The switching power supply (2 Photo 1) fitted to the supporting rails and
is accessible from the upper part of the amplifier as shown in Photo 1.
A mains transformer has a selectable input for voltages between 110,120,220
and 240 Volt and two outputs: A 30+30 Volt, B 18+18 Volt.
The A output drive the switching power supply unit that generate the
50 Volt needed by the RF module.
Output B supplies the soft-start circuit and the ALARMS CARD.
Inside the ALARMS CARD a rectifying and stabilization circuit provides the
+15 and -15 Volt needed by the electronics.
The 50 Volt switcher regulate the RF output power using a voltage detected
by a directional coupler mounted inside the low pass filter box.
2.2 SOFT START
The soft start (6 Photo 1) eliminates the current spikes generated by the
transformer when it is powered.
2.3 R.F. POWER AMPLIFIER MODULE
The R.F. power amplifier module (4 Photo 1) are placed in the right side
of the PJRL250. This module is totally shielded and placed on a heat sink as
shown Photo 1.
The R.F. power amplifier module delivers 250W with 10W of drive and is supplied
by an switching power supply.
The quiescent parameters of module are:
VDC=50V I
dq
=400mA
The active device employed is a Mosfet (BLF378).
2.4 LOW PASS FILTER
This filter (1 Photo 1) is fitted in a metallic box mounted on the internal
chassis in the position shown in Photo 1 .
Thanks to this low pass filter we have a harmonic suppression of more than
75 dB.