He continues to state that the turn-on and turn-off lead time is adjustable and can be set to accommodate a variety of power-MOSFET sizes and circuit conditions. The IR1175 also provides gate-drive overlap/dead-time control via external components. These features further reduce diode conduction by nulling the effects of secondary-loop and device package inductance. Above all, Abdoulin emphasizes that the IR1175 is a standalone circuit that has no ties to the primary. The controller derives its operating power directly from the secondary winding of the transformer.
To enable the controller to work in noisy environments, the IC employs Schmitt-trigger inputs incorporating double pulse-suppression techniques. The device also boasts high-current drive capability and high-speed operation. Plus, it's adaptable to multiple topologies. As per the data sheets, the IR1175 offers up to 2-A output drive current and 2-MHz switching capability. Abdoulin cautions, however, that the controller is best suited for designs that operate below 500 kHz and require less than 2-A drive current. For very high current requirements, he recommends external gate drivers.
Selecting the right MOSFETs from the maze out there is equally challenging. To more easily choose the most appropriate parts that will work efficiently with the controller, IR has unveiled optimized MOSFET families. Using its stripe-planar process, the manufacturer developed application-specific HEXFETs for both the primary and secondary side of the transformer.
At the primary end, for instance, 200-V and 150-V HEXFET power MOSFETs have been crafted to offer an optimal combination of on-resistance, gate charge, and die size. The technology applied gives the best tradeoff between the switching and conduction losses, says the company. Plus, by packing these devices in miniature surface-mountable D2PAK and DPAK packages, they offer power-density and cost-per-watt benefits.
Initially, four parts have been readied for the primary side. These include the 200-V, 30-A IRFS30N20D, the 200-V, 13-A IRFR13N20D, the 150-V, 41-A IRFS41N15D, and the 150-V, 18-A IRFR18N15D. For the secondary side, the supplier released three optimized devices that provide a combination of on-resistance and gate charge based on the output power rating and circuit topology. The two 30-V power MOSFETs include IRFBL3703 and IRF7455. The 20-V version is called the IRF7456 (see the table). Because it comes housed in a Super-D2PAK package, the IRFBL3703 is able to target high-current applications in which space is of utmost importance.
To demonstrate the impact of the dedicated solution, the company developed an experimental, single-ended forward converter with synchronous-rectifier control. It uses IR1175 and optimized primary and secondary power MOSFETs (Fig. 2). Compared to the self-driven, cross-coupled design, this solution shows remarkable improvement in the overall efficiency of the dc-dc converter. Internal tests indicate that it achieves about 88.4% efficiency for a 200-W brick (Fig. 3). IR engineers believe that further matching the primary- and secondary-side MOSFETs closer to the dedicated controller, as well as tweaking the design for lower losses due to the magnetics, will bring another 1% to 2% enhancement.
Meanwhile, the company continues to refine the synchronous-rectification controller to completely match the device with the MOSFETs. The controller line might be expanded to extend the solution to other topologies, including non-isolated versions. Outputs could eventually drop down to 1.8 V and below.
Price & Availability
The IR1175 5-V CMOS dedicated controller comes in a 20-pin SSOP package. It's available for $2.75 each in 1000-piece quantities. Both the primary and secondary optimized power MOSFETs are sampling now, with production to follow next month. In 10,000 pieces, the primary-side MOSFET IRFS30N20D is priced at $0.95, and the secondary-side IRF7455 costs $0.72, respectively.
International Rectifier Corp., 233 Kansas St., El Segundo, CA 90245; (310) 252-7105; www.irf.com
He continues to state that the turn-on and turn-off lead time is adjustable and can be set to accommodate a variety of power-MOSFET sizes and circuit conditions. The IR1175 also provides gate-drive overlap/dead-time control via external components. These features further reduce diode conduction by nulling the effects of secondary-loop and device package inductance. Above all, Abdoulin emphasizes that the IR1175 is a standalone circuit that has no ties to the primary. The controller derives its operating power directly from the secondary winding of the transformer.
To enable the controller to work in noisy environments, the IC employs Schmitt-trigger inputs incorporating double pulse-suppression techniques. The device also boasts high-current drive capability and high-speed operation. Plus, it's adaptable to multiple topologies. As per the data sheets, the IR1175 offers up to 2-A output drive current and 2-MHz switching capability. Abdoulin cautions, however, that the controller is best suited for designs that operate below 500 kHz and require less than 2-A drive current. For very high current requirements, he recommends external gate drivers.
Selecting the right MOSFETs from the maze out there is equally challenging. To more easily choose the most appropriate parts that will work efficiently with the controller, IR has unveiled optimized MOSFET families. Using its stripe-planar process, the manufacturer developed application-specific HEXFETs for both the primary and secondary side of the transformer.
At the primary end, for instance, 200-V and 150-V HEXFET power MOSFETs have been crafted to offer an optimal combination of on-resistance, gate charge, and die size. The technology applied gives the best tradeoff between the switching and conduction losses, says the company. Plus, by packing these devices in miniature surface-mountable D2PAK and DPAK packages, they offer power-density and cost-per-watt benefits.
Initially, four parts have been readied for the primary side. These include the 200-V, 30-A IRFS30N20D, the 200-V, 13-A IRFR13N20D, the 150-V, 41-A IRFS41N15D, and the 150-V, 18-A IRFR18N15D. For the secondary side, the supplier released three optimized devices that provide a combination of on-resistance and gate charge based on the output power rating and circuit topology. The two 30-V power MOSFETs include IRFBL3703 and IRF7455. The 20-V version is called the IRF7456 (see the table). Because it comes housed in a Super-D2PAK package, the IRFBL3703 is able to target high-current applications in which space is of utmost importance.
To demonstrate the impact of the dedicated solution, the company developed an experimental, single-ended forward converter with synchronous-rectifier control. It uses IR1175 and optimized primary and secondary power MOSFETs (Fig. 2). Compared to the self-driven, cross-coupled design, this solution shows remarkable improvement in the overall efficiency of the dc-dc converter. Internal tests indicate that it achieves about 88.4% efficiency for a 200-W brick (Fig. 3). IR engineers believe that further matching the primary- and secondary-side MOSFETs closer to the dedicated controller, as well as tweaking the design for lower losses due to the magnetics, will bring another 1% to 2% enhancement.
Meanwhile, the company continues to refine the synchronous-rectification controller to completely match the device with the MOSFETs. The controller line might be expanded to extend the solution to other topologies, including non-isolated versions. Outputs could eventually drop down to 1.8 V and below.
Price & Availability
The IR1175 5-V CMOS dedicated controller comes in a 20-pin SSOP package. It's available for $2.75 each in 1000-piece quantities. Both the primary and secondary optimized power MOSFETs are sampling now, with production to follow next month. In 10,000 pieces, the primary-side MOSFET IRFS30N20D is priced at $0.95, and the secondary-side IRF7455 costs $0.72, respectively.
International Rectifier Corp., 233 Kansas St., El Segundo, CA 90245; (310) 252-7105; www.irf.com