Power Integrations expands dc-dc chip line for PoE apps

The IEEE approved the 802.3af standard for power over standard Ethernet cables in June last year. Since then, many products have been introduced for this emerging market.

To boost its DPA-Switch family, Power Integrations added six part types in 8-pin plastic DIP and surface mount packages. The company boasts lower-power converter system cost using the new ICs and simpler dc-dc power conversion designs in a wider array of applications for PoE and Powered Devices (PDs) under the 802.3af standard.

The DPA-Switch line of converter ICs can deliver up to 100W of continuous power, suitable for PDs over the full PoE power range. These ICs integrate a 220V high-frequency power MOSFET, PWM control, fault protection and other control circuitry in one CMOS chip. The chips can eliminate more than 20 external components compared to a standard MOSFET plus PWM controller dc-dc converter design, which can save board space, shorten design cycles and lower system cost.

The product line also offers built-in soft-start, selectable 300kHz or 400kHz switching frequency, cycle skipping at light load and internal hysteretic thermal shutdown. The converter ICs can be used in both flyback and single-ended forward topologies and are compatible with any self-driven synchronous rectification scheme to boost efficiency in low-voltage, high-current applications.

Power classifications

The IEEE802.3af standard defines 3 power classifications. Class 1 device needs 4W, Class 2 needs 7W and Class 3 power device requires 15W. An end device with no stated classification is assumed to require 15.4W.

Power-over-Ethernet offers a significant reduction in power supply costs for IP phones and WLANs by providing the necessary power over the same CAT-5 cable. PoE is expected to save 50 percent of overall costs by eliminating electrical wiring and power outlets for powered devices.

Aside from PoE and PD applications, the DSP-Switch family can also be used in networking and telecommunication line cards, "brick" dc-dc converter modules, digital feature phones, and industrial controls.

Power Integrations is also offering two new design accelerator kits (DAK-68 and DAK-71) for the DPA-Switch family, each with an operational dc-dc converter reference design and an engineering report.

Dave Ledesma

Electronic Engineering Times - Asia