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Sychronous Rectification

From Beta Dyne Inc.
 

 
Synchronous rectification (SR) is used in DC/DC converters when low output voltage is less than 5V and high current is needed. Synchronous rectification utilizes power MOSFETs to rectify the output voltage of the power transformer. These MOSFETs are synchronized to the converter frequency and perform more efficiently the rectification of the output voltage than rectifying diodes due to the low I×R drop through the channel. The N channel power MOSFET offers the lowest ON resistance and is relatively inexpensive. In order to reduce the MOSFET ON resistance, semiconductor manufacturers parallel connect many higher ON resistance MOSFETs (or cells.) The parallel connection of cells not only decreases the ON resistance of the resulting channel but also parallel connects their parasitic capacitance. Today, a typical N channel MOSFET has an ON resistance of 5 to 10mO VDS 30V and a gate capacitance of 3300 to 6800pF. The higher parasitic capacitance of the power MOSFET limits its application to switching frequencies below 1MHz and requires high-speed, high-power gate driving signals to switch.
Products & Services
AC to DC converter chips transfer an AC input into DC power using switching (MOSFET, IGBT) or rectification (diodes, Schottky diodes). Learn more about AC to DC Converter Chips
Power MOSFETs are majority carrier devices which have high input impedance and do not exhibit minority carrier storage effects, thermal runaway, or secondary breakdown. Power MOSFETs have higher breakdown voltages than bipolar junction transistors (BJTs) and can be used in higher frequency applications where switching power losses are important. Search by Specification | Learn more about Power MOSFET
Metal-oxide semiconductor field-effect transistors (MOSFETs) are electronic switching devices with a conducting channel as the output. An electrode called a gate controls the width of the channel and determines how well the MOSFET conducts. Search by Specification | Learn more about Metal-oxide Semiconductor FET (MOSFET)
DC-DC converter chips provide a regulated DC voltage output from a different, unregulated input voltage.  Search by Specification | Learn more about DC-DC Converter Chips
Insulated gate bipolar transistors (IGBT) are bipolar transistors with an insulated gate. They combine the advantages of the bipolar transistor (high voltage and current) with the advantages of the MOSFET (low power consumption and high switching). Search by Specification | Learn more about Insulated Gate Bipolar Transistors (IGBT)
Product Announcements
Mouser Electronics, Inc. - Vishay Siliconix’s TrenchFET® Gen III Power MOSFET
Mouser Electronics, Inc., known for its rapid introduction of the newest products, today announced it is stocking Vishay Siliconix's TrenchFET Gen III Power MOSFETs. Vishay Siliconix transistors and... (read more)
ON Semiconductor L.L.C. - NCP1580 Low Voltage Synchronous Buck Controller
The NCP1580 is a voltage mode PWM controller designed to operate from a 5.0 V or 12 V supply and produce an output voltage as low as 0.8 V. This 8−pin device provides an optimal level of... (read more)
Banner Engineering Corp. - QS18 Universal Voltage Sensors
Banner Engineering Corp. introduces the WORLD-BEAM® QS18 Universal Voltage sensors featuring ac or dc voltage operation. The 3-wire photoelectric sensors deliver solid-state output for reliable... (read more)
Micropac Industries, Inc. - 53111 Power MOSFET Optocoupler (Solid State Relay)
The 53111 is a single channel, hermetically sealed power MOSFET optocoupler, for Space, Military and Hi Rel Applications. Visit www.micropac.com for more information on our full line of products. (read more)
Topics of Interest
3.3 Power MOSFET On-Resistance As discussed in Chapter 2, the RF output power that can be delivered using a power MOSFET can be reduced by its on-resistance because it limits the lowest excursion of... (Read More)
9.2.8 MOSFET Current Ratings For bipolar transistors, maximum output current is limited by the fact that current gain falls drastically as output current rises. Thus unacceptably high base input... (Read More)
3.4 Summary In this chapter, the physics of operation of the super-linear (SL) MOSFET structure has been contrasted with that of the conventional MOSFET structure by deriving analytical equations... (Read More)
The low on-resistance and high current carrying capability of power MOSFETs make them preferred switching devices in SMPS power supply design. However, designing with these devices is not as... (Read More)
Overview The focus of this book is on silicon power MOSFETs used for cellular signal amplification. These devices contain a channel region, which enables control of the output current of the... (Read More)
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