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Fairchild Power Switch Sep, 2004 Power Conversion
The Value Proposition of PoE After Before Each end device gets it’s own power from the network. Each end device needs it’s own power supply. External AC/DC Adaptor Built in DC/DC Converter
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.
Some Possible Uses of the Technology • Already manufacturers have products on the market. Many of these are described in the Products section of the www.PowerOverEthernet.com 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. • IEEE802.11 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.
Power-over-Ethernet(PoE) LAN switches • The user would merely have to plug the devices into a traditional Category-5, Ethernet-cable wall socket.
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 DTE end RG-45 Switch End RG-45 Switch End RG-45 DTE end Normal legacy network Power Supplied over the Spare Pins
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
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.
Feedback for off-line DC/DC converters • Optimized Feedback for off-line DC/DC converters • Current Mode PWM IC
Features: Over Load Protection Vck FPSTM Secondary Side V 1mA 5uA Shutdown FB Vo 7.5V OSC. 2.8R Cfb Vfb* R S 3V Q Voffset R LEB 0 t t1 t2 Reset R 7.5V Q Shutdown Thermal Shutdown S • Time Constant : 5uA = Cfb * 4.5V / t2 • 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.
Over Voltage Protection Vck OSC. S Q R 7.5V FS6X1220RT 1mA 5uA 2.5R Vfb* R Reset R Q Shutdown S Vcc Vcc Thermal Shutdown Vovp • Protection for over voltage • Auto restart mode
Auto Restart • Auto-restart : protection latch is automatically reset when Vcc < 9V
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