CDX2000 / 13.56 MHz & 400 kHz Manual
© 2006 Comdel, Inc.
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Theory of Operation
The CDX2000 is a dual frequency power amplifier for use in OEM applications. The power sources consist of an
AC Interlock assembly, DC power supply, a 1000W 13.56 MHz power amplifier and a 1000W 350-450 kHz power
amplifier, and associated control systems and monitoring circuits.
13.56 MHz Amplifier
The radio frequency signal is generated locally in the Oscillator Control Module. From this module the signal goes
to the driver. The driver further amplifies the signal to approx. 40 Watts to drive the power amplifier. From the PA
the signal is fed through a low-pass filter to remove harmonic content. Forward and Reflected control signals are
obtained from the output signal as it passes through the power monitor board to the output RF connector. The
front panel CDX Controller monitors the user input from either the front panel or rear connector, and monitors the
control signals from the RF output power monitor, PA current monitor, and PA overtemp switch. Refer to Figure
FP5315RX, CDX2000 BLOCK DIAGRAM, to see how the individual modules are connected together.
400 kHz Amplifier
The radio frequency signal is generated locally on the front panel CDX controller. From this assembly, the signal
goes to LF1250 power amplifier (PA). The output of this power amplifier is matched to 50 ohms through a 6 pole
low-pass filter. Control signals are obtained from the output signal as it passes through the power monitor board to
the RF output connector. The front panel CDX Controller monitors the user input from either the front panel or rear
connector, and monitors the control signals from the RF output power monitor, PA voltage sensors, PA current
monitor, and PA overtemp switch. Refer to Figure FP5315RX, CDX2000 BLOCK DIAGRAM, to see how the
individual modules are connected together.
The LF1250 amplifier’s frequency can be manually adjusted between 380-420 kHz from the front panel (local mode
only) or the amplifier can Autotune to minimize reflected power. The Autotune algorithm is carried out in the
generator’s firmware and is optimized to tune quickly in a plasma load. There are some adjustable parameters that
can be set via DIP switches on the CX microcontroller assembly located behind the front panel. Adjustment of
these switches should not normally be necessary. A description of the switch settings is located under CDX
Autotune Parameters at the end of this section.
A. AC Interlock System
WARNING: Never attempt to operate this equipment with any of the interlocks bypassed.
The AC mains to the mains power transformer is switched via relay K1, controlled by the AC INTERLOCK
PCB (Figure FA0900RX) mounted on the front panel behind the ON/OFF softkeys. AC power to this interlock
system is supplied by 24VAC transformer, which is energized when circuit breaker CB1 on the back panel is
thrown.
The AC INTERLOCK PCB supplies the logic to the AC mains control contactor to start and stop the CDX2000
via the front panel softkeys. The PCB's start/stop circuitry is composed of relay logic for safety. The active
circuitry (U1A) causes the OFF softkey lamp to flash if the interlock loop is broken.
The interlock 'loop' for the CDX2000 includes the rear panel I/O 15 pin 'D' connector, the top cover, and the
RF output connector cover.
B. DC Power Supply
The DC supply consists of a three-phase transformer, full-wave, bridge rectifier and a low-pass filter for the
main power voltages. There are three single-phase bridge rectifiers and filters feeding the positive 15 volt,
negative 15 volt, and positive 5 volt regulators. A negative 5 volt supply is generated from the regulated
negative 15 volt supply. These voltages are used in the control circuitry.
