[Lowfer] Epson Question

[Bill Ashlock]

Johan,

Thank you for pointing out the error of my ways in the amplitude of the 
square wave fundamental freq. This makes a lot of sense in my calculations 
for the loop current when the input power is known. The measured value was 
always greater than the calculated value. I just located my college textbook 
and, sure enough, there's a 4/pi factor in front of the fourier series!

Bill A


>From: "Johan Bodin" <jbodin@tele2.se>
>Reply-To: lowfer@mailman.qth.net
>To: <lowfer@mailman.qth.net>
>Subject: Re: [Lowfer] Epson Question
>Date: Tue, 20 Apr 2004 07:20:26 -0000
>
>Hi
>
>the fundamental frequency component of a square wave
>has an amplitude of:
>
>Vsine_rms = Vsq_wave_peak_to_peak * square_root (2) / pi
>
>which means
>
>Vsine_rms = Vsq_wave_peak_to_peak * 0.4502
>
>or
>
>Vsine_peak_to_peak = Vsq_wave_peak_peak * 1.2732
>
>(Assuming 50/50 % square wave duty cycle)
>
>Although it may appear surprising, the Vpp of the fundamental
>frequency component is larger than the Vpp of the square wave itself :-)
>
>To run class D, you can put a series resonant circuit of sufficient
>loaded Q, say 5 or more, between the square wave generator and
>the load (XC = XL = 5*Rload, or more).
>
>The series circuit will pass only the fundamental frequency so the
>generator will see only negligible loading on the harmonics.
>This is much better than using a "grounded C input" lowpass
>filter directly at the generator output (which will cause high current
>switching spikes = more switching loss).
>
>BTW, I would guess that the Epson oscillator has a quite "weak" output
>stage so it will probably deliver more power into a load >50 ohms.
>
>73
>Johan SM6LKM
>
>_______________________________________________
>From the Lowfer mailing list
>Send messages to: Lowfer@mailman.qth.net
>To sub/unsub visit: http://mailman.qth.net/mailman/listinfo/lowfer

_________________________________________________________________
Free up your inbox with MSN Hotmail Extra Storage! Multiple plans available. 
http://join.msn.com/?pgmarket=en-us&page=hotmail/es2&ST=1/go/onm00200362ave/direct/01/