Project Analog - April 2008 - (Page 10) Accelerating design of >50-W Class D amplifiers A power switching stage for Class D designs lets you concentrate on amp features and bypass the learning curve By Jun Honda International Rectifier / El Segundo, CA www.irf.com Contents Viewpoint Calculating Power Dissipation Accelerating Amplifier Design Driving Power MOSFETs Analog news M arket demands for low-profile designs and high audio output make Class D audio amplifiers very attractive to makers of high-end domestic and automotive audio products. For audio designers, integrated flexible Class D gate drivers eliminate much of the guesswork associated with power switching design. In Class D operation, the amplifier output transistors switch between the hard-on and hard-off states, allowing the amplifier to operate at >95% efficiency. Compared to typical Class A/B amplifier efficiency of 30%, this improvement reduces heat dissipation and thermal management requirements. When operated at one-eighth of full 10 · prOjECT ANAlOg · Apr 08 Microchip analog page rated power, which is considered normal for safety reasons, Class D amplifiers can operate without a heat sink. The overall component count is also lower than for a traditional linear amplifier, allowing designers to achieve high audio outputs within compact case dimensions while reducing build complexity. Figure 1 compares the relative physical sizes of a two-channel linear Class A/B amplifier of 120-W/ channel output with a comparable Class D reference design. The Class D implementation occupies 61 cm2 PCB area and total volume 109 cm3, compared to 390 cm2 and 1,794 cm3, respectively, for the Class A/B design. MOSFET driver overview Sample center microchipDIRECT Reference designs/ app notes Technical training http://www.irf.com http://www.microchip.com http://www.microchip.com/analog http://www.microchip.com/analog http://www.microchip.com/mosfetdriver http://www.microchip.com/mosfetdriver http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423
Table of Contents Feed for the Digital Edition of Project Analog - April 2008 Project Analog - April 2008 Contents Viewpoint About Project Analog Sponsor Calculating Power Dissipation in a MOSFET Driver Accelerating Design of >50-W Class D Amplifiers Driving Power MOSFETs in Switch Mode Power Supplies Synergistic MOSFET Solutions Trends in MOSFET Gate Drivers Analog News—Analog news from multiple sources Enter to win an iPhone Contact Project Analog Sponsor Treelink Microchip Advanced Parts Selector (MAPS) Project Analog - April 2008 Project Analog - April 2008 - Project Analog - April 2008 (Page 1) Project Analog - April 2008 - Contents (Page 2) Project Analog - April 2008 - Viewpoint (Page 3) Project Analog - April 2008 - About Project Analog Sponsor (Page 4) Project Analog - April 2008 - Calculating Power Dissipation in a MOSFET Driver (Page 5) Project Analog - April 2008 - Calculating Power Dissipation in a MOSFET Driver (Page 6) Project Analog - April 2008 - Calculating Power Dissipation in a MOSFET Driver (Page 7) Project Analog - April 2008 - Calculating Power Dissipation in a MOSFET Driver (Page 8) Project Analog - April 2008 - Calculating Power Dissipation in a MOSFET Driver (Page 9) Project Analog - April 2008 - Accelerating Design of >50-W Class D Amplifiers (Page 10) Project Analog - April 2008 - Accelerating Design of >50-W Class D Amplifiers (Page 11) Project Analog - April 2008 - Accelerating Design of >50-W Class D Amplifiers (Page 12) Project Analog - April 2008 - Driving Power MOSFETs in Switch Mode Power Supplies (Page 13) Project Analog - April 2008 - Driving Power MOSFETs in Switch Mode Power Supplies (Page 14) Project Analog - April 2008 - Driving Power MOSFETs in Switch Mode Power Supplies (Page 15) Project Analog - April 2008 - Synergistic MOSFET Solutions (Page 16) Project Analog - April 2008 - Synergistic MOSFET Solutions (Page 17) Project Analog - April 2008 - Synergistic MOSFET Solutions (Page 18) Project Analog - April 2008 - Trends in MOSFET Gate Drivers (Page 19) Project Analog - April 2008 - Trends in MOSFET Gate Drivers (Page 20) Project Analog - April 2008 - Trends in MOSFET Gate Drivers (Page 21) Project Analog - April 2008 - Analog News—Analog news from multiple sources (Page 22) Project Analog - April 2008 - Contact Project Analog Sponsor (Page 23) Project Analog - April 2008 - Treelink (Page 24) Project Analog - April 2008 - Microchip Advanced Parts Selector (MAPS) (Page 25) Project Analog - April 2008 - Microchip Advanced Parts Selector (MAPS) (Page 26) Project Analog - April 2008 - Microchip Advanced Parts Selector (MAPS) (Page 27) Project Analog - April 2008 - Microchip Advanced Parts Selector (MAPS) (Page 28) Project Analog - April 2008 - Microchip Advanced Parts Selector (MAPS) (Page 29) Project Analog - April 2008 - Microchip Advanced Parts Selector (MAPS) (Page 30) Project Analog - April 2008 - Microchip Advanced Parts Selector (MAPS) (Page 31)
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