Product category:
Power Supply ICs and Controllers
News Release from: International Rectifier | Subject: DirectFET MOSFETs and IR2086S controller IC
Edited by the Electronicstalk Editorial
Team on 12 November 2004
MOSFETs work with full-bridge controller
IC
International Rectifier has a new chipset solution for wide-range, universal telecommunications input (36 to 75V) and 48V fixed input systems.
International Rectifier has a new chipset solution for wide-range, universal telecommunications input (36 to 75V) and 48V fixed input systems Designed for isolated or nonisolated DC/DC convertor applications, the chip set enhances system level power supply performance such as bulk 48V conversion for system boards up to 220W or for powering the radio amplifier in basestation systems
This article was originally published on Electronicstalk on 15 Feb 2001 at 8.00am (UK)
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Two new 20V HEXFET power MOSFET families from International Rectifier are designed to increase efficiency by up to 4% in 12V-input DC/DC convertors.
"Our new optimised chip set consists of new DirectFET MOSFETs and the new IR2086S controller IC to create simplified complete solutions for two commonly used convertor topologies in the networking and communications industry", said Carl Smith, Marketing Manager for Networking and Telecommunication Products at International Rectifier.
The IR2086S controller IC simplifies isolated DC/DC convertor circuits using primary side full-bridge topologies.
The IC is specifically optimised for bus convertor applications, using a self-oscillating 50% fixed duty cycle.
Further reading
MOSFETs improve power density on both sides
New from International Rectifier are two TO-220-packaged HEXFET power MOSFETs that maximise power density and performance in primary- and secondary-side DC/DC convertor circuits.
Rad-hard MOSFETs protect and survive
With high radiation hardness and unparalleled single event effect (SEE) immunity, International Rectifier's new R5 MOSFETs are well suited for systems that must survive penetrating gamma rays.
Reference design simplifies high-efficiency PSUs
International Rectifier has released a reference design for its recently introduced IR1176 application-specific synchronous rectification IC (SRIC).
It helps reduce overall board space by up to 50% compared with industry-standard quarter-bricks and reduces overall component count by up to 60%.
The IR2086S features an integrated soft-start capacitor that gradually increases duty cycle to 50% over 2000 cycles to limit inrush current during start up and maintains equal pulsewidths for the high- and low-side MOSFETs in the full bridge throughout the startup sequence.
Other features include hiccup current limit protection, +/-1.2A gate drive current and adjustable deadtime from 50 to 200ns to protect against shoot-through current and programmable switching frequency up to 500kHz.
To complete the chipset, a designer may choose from four new DirectFET MOSFETs, the 100V IRF6644 and IRF6655 or 40V IRF6613 and IRF6614.The new MOSFETs use IR's latest trench technology with DirectFET packaging technology, enabling dramatic reduction in key device specifications such as on-resistance and gate charge.
A typical telecomms basestation power amplifier stage, for example, requires a 28V regulated output from a wide-range (36 to 75V) input.
IR's new DirectFET MOSFET and controller IC chip set can be used to create a very efficient (92.5% at full load, 28V/250W) convertor using a two-stage approach.
The first stage uses the IRF6655 and IRF6644 in a nonisolated synchronous buck configuration to produce a regulated intermediate voltage, followed by a simple full bridge fixed-ratio bus convertor using the IR2086S and IRF6614 on the primary side, and the IRF6644 on the secondary side for self-driven synchronous rectification.
This solution eliminates complex secondary side control schemes that are used in single stage regulated solutions.
The 50% nature of the bus convertor also allows the use of 100V MOSFETs on the secondary side, rather than 150 or 200V MOSFETs that can reduce efficiency by up to 2%.
The new 100V IRF6644 can also be used to achieve up to 95.7% efficiency at full load of 220W (8V/27.5A) in stand-alone fixed 48V input bus convertor applications, suitable for most networking and high-end computing systems.
Compared with similar circuits using single 100V SO-8 MOSFETs, this is approximately 1% better efficiency, and a 40C reduction in device temperature.
This lower device temperature eliminates the need to parallel additional devices on the primary side for increased current requirements, and in general the IRF6644 enables an approximately 46% increase in output power and balanced temperature between the primary side and secondary side of the convertor.
The IRF6644 achieves approximately 48% lower on-state resistance compared with competing solutions with similar charge parameters.
Key performance figures-of-merit for combined on-state resistance and gate charge are up to 45% better than competing solutions, and the IRF6644 replaces two parallel, lowest charge competing solutions for equivalent on-state resistance.
Depending on specific input-to-output voltage ratios, the secondary-side synchronous rectification topology can use IR's 40V IRF6613 DirectFET MOSFET, for 33% more voltage headroom than a 30V device.
When using IR's 40V device, efficiencies to within 1% of 30V parts can be achieved.
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