Forward Topology (See Figure 2)
Benefit:
Coiltronics flyback PoE transformers support 1500Vac isolation in the
power converter with feedback voltage of 11V at 0.1A. Available in
4W, 7W and 13W, the transformers accept input voltage ranging from
29.5V to 60V using a nominal 250kHz switching frequency.
Lowest cost for >6A output currents.
When to Use:
Typically for output voltages less than 12 V.
Recommended for multi-output voltages (<2.5V) and for applications
requiring highest efficiency.
Coiltronics PoE transformers feature split primary and secondary
windings to minimize leakage inductance (the result of imperfect
magnetic linking of one winding to another). These transformers allow
multiple output variations. 3.3V and 5V PoE transformers support
three outputs while 12V transformers support two outputs. These
three transformers have parallel windings with identical output voltage.
Advantages:
• Low output ripple current results in lower output capacitor cost.
• Higher efficiency due to lower peak and rms currents can utilize
synchronous rectification.
These enable the windings to be used:
• Independently for isolated circuits
• Isolated output.
Disadvantages:
• Paralleled for higher current
Requires additional components including an output energy storage
inductor and additional rectifying device (diode or MOSFET).
• Connected in series to generate higher voltages.
L
Input
Output
+
+
N
N
Vo
1
C
2
Vin
_
_
Cooper Bussmann Coiltronics 26 Watt PoE Transformers.
Coiltronics also offers transformers for forward converters with
synchronous rectification support, 1500Vac isolation, isolated
feedback voltage and can deliver up to 26W. These transformers
accept an input voltage range from 29.5V to 60V using a nominal
300kHz switching frequency.
Figure 2. Transformer Forward Topology.
Cooper Bussmann® Coiltronics® Transformers
These components operate in ambient temperatures between -40°C
and +85°C with a maximum operating temperature of 125°C.
The Coiltronics Versa-Pac® product line offers more than 500 usable
inductor or transformer configurations. This same user-configurable
concept is used in the PoE transformer family (VER suffix devices).
Connecting the windings in parallel increases the current carrying
capability while connecting in series increases the output voltage.
These devices provide even greater flexibility in the number of voltage
and current combinations than are available in this standard off-the-
shelf transformer series.
Cooper Bussmann Coiltronics 4 to 13 Watt PoE Transformers.
Typical PoE/PD Configurable Transformer Applications
The Coiltronics lines of RoHS compliant PoE configurable transformers
are available for use with a wide variety of PWM controllers from
several IC manufacturers, providing PD supply solutions that utilize
either flyback or forward converter topologies.
• For IEEE 802.3af-compliant Power-over-Ethernet applications.
• UPS, VoiP Phone, wireless LAN access point, Bluetooth access point,
network camera, building access systems.
Flyback and forward DC-DC converters solve the isolation
requirements of the PoE standard. Forward and flyback switcher
topologies can use Coiltronics PoE transformers to isolate the PDs PoE
interface from the rest of its circuitry while stepping down the PoE
input voltage to power the PD circuits.
• Retail point-of-information systems.
• Vending/gaming machines.
COOPER [ COOPER BUSSMANN, INC. ]
