User guide

Xenus Filter Xenus XTL User Guide
156 Copley Controls Corp.
D.1: Overview
The XTL-FA-01 edge filter can be used to minimize noise on the output of any Xenus amplifier.
D.1.1: Differential and Common Mode Filtering
Most noise is capacitively coupled from the motor power cable to neighboring cables. To minimize
this noise, the XTL-FA-01 edge filter uses both differential edge filtering and common mode
filtering. Differential edge filtering reduces the high frequency component of the PWM signal, thus
producing a signal with less energy that can be coupled during transmission. Common mode
filtering reduces the unnecessary common mode noise generated by PWM signals.
D.1.2: Description and Functional Diagram
The differential filter increases the rise time by at least a factor of 3, substantially reducing noise in
the system. Copley Controls amplifiers typically have a 150 ns-rise time (high frequency
component in the MHz range). Thus, the edge filter can increase rise time to 500 ns, reducing the
high frequency noise emissions by the square law. The differential filter is designed with 82 PH
inductors and a proprietary passive circuit. The inductance will provide a total of 164PH in series
with the load, helping to reduce ripple current. This brings low inductance motors into the required
range.
The common mode filter is designed with a 220 PH common mode toroid that works with the cable
capacitance to earth ground to remove common mode switching noise.
Amp
Filter
Motor
U
V
W
J1
J1-4
J1-3
J1-2
J1-1
Common
Mode
82uH
82uH
82uH
Differential
Mode
J2
J2-4
J2-3
J2-2
J2-1
U
V
W
Case GND
D.1.3: PWM Output Plot
+HV
500ns
10%
90%
Raw PWM
Filtered
150ns