1. Fairchild Power Switch
Sep, 2004
Power Conversion

2. The Value Proposition of PoE
Before
After
Each end device needs
it’s own power supply.
Each end device gets
it’s own power from the network.
External AC/DC Adaptor
Built in DC/DC Converter

3. The Motivation for Power over Ethernet
Almost all appliances require both data connectivity and a power supply. In a familiar example, telephones are powered from the telephone exchange through the same twisted pair that carries the voice. Now we can do the same thing with Ethernet devices.
So why bother? Here are some reasons:
Only one set of wires to bring to your appliance - simplifies installation and saves space.
There is no need to pay for an expensive electrician, or delay your installation to meet the electrician's schedule - saves time and money.
The appliance can be easily moved, to wherever you can lay a LAN cable - minimal disruption to the workplace.
Safer - no mains voltages anywhere.
A UPS can guarantee power to the appliance even during mains power failure.
As well as the data transfer to and from the appliance, you can use SNMP network management infrastructure to monitor and control the appliances.
Appliances can be shut down or reset remotely - no need for a reset button or power switch.
In wireless LAN systems it simplifies the RF survey task, as the access point can easily be moved and wired in.

4. Some Possible Uses of the Technology
Already manufacturers have products on the market. Many of these are described in the Products section of the website. There is no shortage of the Power Sourcing Equipment Midspan Hubs, so you can start playing with the technology now. The big market players are using it for these applications:
VoIP (Voice over Internet Protocol) telephones.
IEEE Wireless LAN Access Points.
Bluetooth Access Points.
Web cameras.
But Power Over Ethernet will enable many more appliances. Here's a list - but you can imagine others!
Smart signs/web signs.
Vending machines.
Gaming machines.
Audio and video juke boxes.
Retail point of information systems.
EPOS systems.
Building access control systems.
Time and attendance systems.
Battery chargers for mobile phones and PDAs.
Electronic musical instruments.

5. Power-over-Ethernet(PoE) LAN switches
The user would merely have to plug the devices into a traditional Category-5, Ethernet-cable wall socket.

6. Power Supplied over the Spare Pins
How PoE is done
The power for Power-over-Ethernet devices can be supplied through the spare wires of a typical CAT-5 cable. This is supported by the standard.
Cat5 cable
RG-45
Switch End
RG-45
DTE end
RG-45
Switch End
RG-45
DTE end
Normal legacy network
Power Supplied over the Spare Pins

7. FS6X1220R
Description
The FS6X1220R is a high voltage power switching regulator that combines the required converter functions with allowing a simple power system solution for DC-DC converters
Features
Optimized for Off-line type DC to DC Converter
High switching frequency for good efficiency (300KHz)
Line UVLO monitoring and Sleep on/off
Various protection functions (OVP, OLP, TSD)
Auto restart mode
TO-220F-5L / D2-PAK-5L
Over 80% Efficiency
 Low Rds(on) QFET minimizes conduction losses
 Low capacitance QFET cuts switching losses

8. Start-up
During start up, the power is supplied to Vcc pin from DC link through startup resistor.
When Vcc reaches the UVLO upper threshold, the power is supplied from auxiliary transformer winding.

9. Feedback for off-line DC/DC converters
Optimized Feedback for off-line DC/DC converters
Current Mode PWM IC

10. Features: Over Load Protection
Shutdown
7.5V V t t1 t2
Time Constant : 5uA = Cfb * 4.5V / t2 3V
OSC.
LEB
5uA
1mA
2.8R R
Voffset S Q
Vck
FPSTM FB
Vfb* Vo
Cfb
Thermal
Reset
Secondary Side
Consider the load current increasing significantly
• FPSTM increases its duty cycle within the limits of its pulse-by-pulse current limit
• Output voltage falls and the feedback voltage rises
• If just a momentary surge then the output will rise after the surge and the feedback voltage will resume its steady state
• However, if output is shorted to ground, then feedback voltage continues to rise
• At 3V, feedback voltage is pulled up with a small internal 5µA current allowing for adjusting the delay as shown above
• When feedback voltage crosses the over-load shutdown (VSD) threshold, the FPS stops switching
• With FPSTM not switching, no bias current is supplied and supply Vcc will fall
• When the Vcc voltage reaches its “Under Voltage Lock Out” threshold, the FPSTM is automatically restarted
• The cycle will repeat until the fault condition is removed.

11. Over Voltage Protection
FS6X1220RT
Vck
5uA
1mA
OSC.
2.5R S Q R
Vfb* R
Reset R Q
Shutdown
7.5V S
Vcc
Vcc
Thermal
Shutdown
Vovp
Protection for over voltage
Auto restart mode

12. Auto Restart
Auto-restart : protection latch is automatically reset when Vcc < 9V

13. Sleep mode and Line UVLO
Line UVLO mode (VLS<2.5V): operating current = 10mA
Sleep mode (VLS<1.8V): operating current = 300uA
Startup current : 60 uA

14. Measured Efficiency Input = 36V Pin Efficiency Io Vo Po 1A 3.362V
3.36W
4.14W
81.13% 2A
3.357V
6.71W
7.64W
87.91% 3A
3.351V
10.05W
11.31W
88.92% 4A
3.345V
13.38W
15.02W
89.08% 5A
3.338V
16.69W
18.66W
89.45% 6A
20.17W
22.78W
88.55%
Input =48V
3.374V
3.37W
4.58W
73.72%
3.369V
6.74W
8.20W
82.20%
3.363V
10.09W
11.89W
84.88%
3.355V
13.42W
15.67W
85.67%
16.73W
19.53W
85.63%
3.334V
20.00W
23.57W
84.87%
Input =60V
Pin
Efficiency Io Vo Po 1A
3.378V
3.38W
4.80W
70.33% 2A
3.373V
6.75W
8.57W
78.73% 3A
3.365V
10.10W
12.22W
82.62% 4A
3.357V
13.43W
16.01W
83.86% 5A
3.346V
16.73W
19.87W
84.21% 6A
3.334V
20.00W
23.84W
83.91%
Input =72V
3.381V
5.09W
66.41%
3.375V
8.97W
75.28%
3.368V
12.67W
79.73%
3.359V
13.44W
16.45W
81.70%
20.31W
82.37%
3.335V
20.01W
24.25W
82.52%

15. Measured Efficiency