High-speed pin diodes are stabile and reliable

Now available from RF and microwave component specialist Link Microtek is a range of high-speed PIN diodes that are made from high-resistively epitaxial silicon material, passivated with silicon dioxide to achieve high levels of stability and reliability.
Capable of operating with as little as +10mA forward bias, the devices are ideal for RF switching applications in telecommunications, radar and ECM systems, and they can also be used as current-controlled resistors in attenuator-type applications over the frequency range from UHF to Ku band.

Available from www.usbid.com - Diode Silicon Epitaxial Planar Type - 015AZ2.0~015AZ12 is designed for Constant Voltage Regulation Applications. Toshiba Diode Silicon Epitaxial Planar Type 015 AZ 2.0 • 015AZ2.0-X. Flash memory may be ordered from USBid catalog page http://www.usbid.com/search/AddPartNoLogin_action.cfm

PFC diodes are needed
Choosing a suitable diode is the easiest and most cost-effective way of reducing both the peak power and the average switching losses in the MOSFET.

Conventional ultra fast epitaxial diodes are optimized for low forward voltage as well as short recovery time. Diodes for use in power factor correction circuits have higher forward voltage but much shorter reverse recovery times in order to reduce the transistor losses

Active power factor correction has a number of advantages, which result from removing the effect of power line voltage variations:
• Greater efficiency and better line voltage regulation in the downstream switched mode converter stages.
• Use of a smaller reservoir capacitor for a given hold-up time, because energy storage is always at a higher voltage than the peak of the rectified mains.
• Lower peak current in the mains input rectifier diodes and lower ripple current in the reservoir capacitor
• Operation over the full international range of power line voltages (90-V - 277-V AC rms) without range switching

In contrast, ultra fast epitaxial diodes designed for power factor correction need to have much faster reverse recovery in order to reduce the MOSFET switching losses.
The reverse recovery time of a BYC5 power factor correction diode is typically 15 ns at 500 A/-Mu s, 25 Celsius, and the maximum forward voltage is 2.8 V at 5 A, 25 Celsius. This represents the optimum trade-off between forward voltage and reverse recovery time in this application