BPC Series Power Resistors

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Resistive Components
BPC Series
Power Resistors
Non-inductive Planar
Thick Film Power
Resistors
• Planar thick film
• Low inductance
• High frequency
operation
• Vertical mount
• Low board level
temperature
• 20x rated
power surge
A subsidiary of TT electronics plc
BI Technologies
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BI Technologies offer the BPC series of non-inductive planar thick film power resistors for current limiting, power supply circuits and
snubber circuits. Manufactured using 96% Alumina substrates with Ruthenium oxide resistors the BPC series power resistors are
capable of withstanding a 20x overload for 8ms and offer excellent performance and high reliability. BPC series power resistors are
available in 3, 5, 7.5 and 10 watt power ratings as shown below.
Size
Power rating
Dimensions (length, width, thickness)
BPC3
BPC5
BPC7
BPC10
3W
5W
7.5W
10W
27.7 x 10.2 x 2.54mm
27.7 x 12.7 x 2.54mm
27.7 x 19.1 x 2.54mm
27.7 x 25.4 x 2.54mm
Range
1Ω to 200kΩ
Standard Tolerance %
±10 (optional 1, 2, 5)
Operating Temperature Range
-55°C to +125°C
Operating Voltage Maximum
300 VAC, 500 VDC
Temperature Coefficient of Resistance
±100 maximum ppm/°C (± 250 for values below 1ohm)
Why Use BI Technologies BPC Series Power Resistors?
• Planar Thick Film Cermet Resistor - Very low inductance
for high frequency operation.
• Large surface area to thickness ratio - maximises power
dissipation, minimises hot spots.
• 20x Rated power surge capability.
• Vertical mounting. Power is dissipated above the circuit
board. Enhances board cooling due to natural
convection flow.
• Low operating temperature at board surface means
high temperature solder is not required.
• Minimises required board area. Uses only a third board
area versus a typical wirewound resistor.
1. Inrush current suppression
The BPC may be used to limit inrush
current when a power supply is switched
on. Figure 1 shows a typical PFC circuit
in which two BPC10 resistors in series
function in an inrush current suppression
circuit which operates principally at
switch-on.
BPC010
BPC010
5Ω
5Ω
Ct HM31
Vo 400Vdc
L1
HM00
AC
Line
EMI
filter
Ct
HM31
Load
Co
gate
driver
PFC PWM
Figure 1: A typical PFC Circuit showing two BPC resistors for current inrush suppression
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2. Snubber circuits and Start-up Circuits
The BPC may be used in series with a
capacitor in a snubber circuit to filter
spikes in the rising and falling edges of
square waves.
EMI
filter
BP3
500Ω
R2
BPC5
50kΩ
R1
In Figure 2 BPC3 500Ω is used.
Figure 2 also includes a start-up circuit
that provides 18 Volts to the PWM while
the power supply is turning on. In this
case a 50kΩ, BPC5 is utilised.
to output
circuitry
PWM
18V
47µF
Figure 2: Circuit showing BPC Resistors in Start-up (R1) and Snubber (R2) Applications
3. Inrush current limiting
This resistor limits the amount of current
allowed to surge into the system at turnon. Power resistors in this circuit must be
able to withstand a 20x nominal surge
for 8msec. This is typically a 15Ω, 7-10
Watt, 10% resistor. A typical location of
this resistor is shown in Figure 3. This
resistor carries the main current load.
AC
input
EMI/RFI
filter
* other power
resistors
inrush power
resistor
Figure 3: Circuit showing a BPC Resistor in an Inrush Application
4. Other Snubber Circuits
In these applications the power resistor
bleeds current of the magnetics to
prevent inductive spikes. This resistor will
experience voltage spikes at 2x the
switchmode switching frequency. This is
typically a 500Ω to 1kΩ, 3W to 5W, 2%
to 5% resistor. Circuit configurations are
found in Figure 4.
1000pF
1000Vdc
ceramic
L101
FBL-00-103
1kΩ
2% 3W
FBL-00-103
FBL-00-256
Snubber Circuit 1
Figure 4: Snubber circuits found in power supplies
240pF
20% 1kV
ceramic
Snubber Circuit 2
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Resistive Components
5. Biasing (Current conditioning)
These resistors do not experience surges
or spikes. This is a steady state
application. In these applications the
resistor values vary considerably from
200Ω to 20kΩ, 3W to 5W, 2% to 5%.
An example is shown in Figure 5.
Biasing
resistor
to dc
section
Figure 5: Circuit from a high-current power supply which uses a BPC resistor for Biasing
6. Preloading (1)
This resistor experiences a steady state
condition. The typical resistor is 3Ω to
1kΩ with 10% tolerance. The preloading
is usually a function of the circuit. An
example is shown in Figure 6.
10kΩ
0.1Ω
4.7µF
180Ω
470pF
1000V
ceramic
from
switching
circuitry
1500µF
35V
650Ω
3W
output
preload
resistor
power
resistor
Figure 6: Part of proprietary power supply showing two power resistors
7. Current Limiting
0.01µF(5kV)
BPC resistors have uses as current
limiters in high-voltage power supplies.
An example of a high voltage power
supply, which is used to drive a laser, is
shown in Figure 7 and the BPC resistor is
highlighted.
1800pF
47k 5W
1800pF
BPC5
high voltage diodes
laser
Vsw
Vin
switching Vfb
regulator
Figure 7: Laser power supply showing a BPC5 for current limiting
4
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Resistive Components
8. Preloading (2)
Another example of preloading is in a
Battery Charger circuit as shown in
Figure 8 where a resistor is used as a
dummy load to prevent overcharging the
battery.
Si9405
1M
6.8V
3.65M
7.5Ω
10W
BPC10
8M
1M
load
1A
solar
array
340k
TIP121
12V
5Ahr
1M
VN2222
1.2V
Figure 8: Shunt battery charger which uses a BPC10
Inrush Application
Model BPC
Vertical mounting
Enhances board cooling
due to natural
convection airflow
Planar, Thick Film
Cermet Resistor
Time (milliseconds)
Non inductive
20x Nominal
Power Rating
Automated
laser trimming
Large surface
Maximises power
dissipation and
minimises hot spot
Accurate and stable
resistance values
Power
Leads soldered
on both sides
Built-in stand off
Low operating
temperature
At board surface high
temperature solder
not required
Vertical mounting
Minimises board area
0
Inrush Application
8
5
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Resistive Components
BI Technologies - SMT BI Technologies - ECD BI Technologies - MCD
Company Profile
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© BI Technolgies 2003
A subsidiary of TT electronics plc
Issue B 09/03