>On 8/17/07, Michael Rigby-Jones > wrote: > >> >Should point out though that PWM is a poor way to drive an LED >> >- you're much better off with a proper constant current regulator. >> >> Not if you want to achive the highest possible peak power! >> >> Regards >> >> Mike >> >-----Original Message----- >From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] >On Behalf Of Chris McSweeny >Sent: 17 August 2007 12:29 >To: Microcontroller discussion list - Public. >Subject: Re: [PIC] PWM and high(ish) current > > >Only if you want a flashing LED in your application. Otherwise >you come up against the same mean power limitation as with >running a constant current - the peak power might be higher, >but not the average, and I'd suggest that for human eye >applications 60Hz is fast enough for individual flashes to be >indistinguishable (though you might detect strobing). In that >case the brightness detected will be less than if you ran the >same average current through the LED, but using a steady >current rather than PWM, due to LEDs improved efficiency at >lower drive currents. Agreed for the general case of using an LED for indication or illumination to the human eye. This has been discussed in depth many times on the list for anyone else that wishes more details. However, for other purposes such as remote control, range finding etc. peak power is important. The OP didn't state his application so we don't know if peak power is relevant or not, but he believes he needs high peak current. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist