Pre-charging resistors can be critical in
applications that experience high impulse
current. When devices are suddenly
switched on, these large current transients
can be sufficient to damage PCB traces
and cables, hence the use of a series
resistor to limit such impulses."
Gábor Márk
Resistive Products Application Engineer, Bourns, Inc.
The challenges of pre/discharge
resistors that engineers can expect
Several challenges are associated with pre/
discharging resistors. First, they need to be able
to handle high-power pulses, something which
is common when capacitive loads are suddenly
connected to a circuit. Second, they need to have
high overload-voltage capability, as applications
that are subject to overvoltage conditions (such as
switching inductors) can see large transients. These
resistors also go through rapid thermal cycles, so
they need high thermal capacity as well to account
for repeated contraction and expansion. Finally, while
discharge resistors reduce the overall efficiency of a
circuit, they are still needed for safety reasons.
How Bourns
®
pre/discharge
resistors provide engineers with the
best solutions
Bourns offers several solutions for pre/discharging
resistors. The CMP series of pulse-withstanding
thick-film chip resistors provide high pulse power
handling capabilities, making them ideal for use
in pre-charging circuits. The CRS series of chip
resistors are tested for 1.2/50 µs surge, providing
C h a p t e r 4 | R e s i s t i v e S o l u t i o n s f o r P r e / D i s c h a r g i n g C i r c u i t s
21
Passives and Their Emerging Applications
