From: firstname.lastname@example.org (R.Legg)
Subject: Re: Help needed - H-bridge, ClassD output stage IC
Date: 15 Jan 2003 22:59:18 -0800
NNTP-Posting-Date: 16 Jan 2003 06:59:18 GMT
> I was planning to do the same thing as TI since my modulator is very
> stable. I ran a lot of tests in matlab and I don't really see where it
> could go wrong. However, I'm not really sure this is what you meant
> since you said is is 'somewhat naive' to you. Do you mean that the
> output stage would require feedback for proper operation?
If the bridge timing and recovery delays were insignifigant in
generating the intended volt-seconds, to be averaged by the output
If the pwm was always used the full supply rail voltage, so that
energy recovery did not modify output volt-seconds,
If the output filter components were linear under large signal
If the load impedance were resistive and linear with respect to the
If the noise generated by the switches were sufficiently partitioned
so as not to affect any other circuitry (or test equipment)in the
neighbourhood in an unpredictable manner,
Then you could expect the output to reflect the intended result of the
TI is confident that their evaluation circuit is capable of achieving
this, under specified conditions and using the recommended parts,
equipment and test methods. Some commercial manufacturers will sell
you something in a box, which you must assume does what it claims,
over the range of temperatures indicated.
I wonder what it takes to guarantee that a breadboard will do the same
thing, after it's been made to fit somebody's idea of a practical
production line device?
Considering the distortion generated by most audio transducers,
differences may be irrelevant to the end user and it is hardly likely
to be used in critical applications, without testing.
The application of digital power modulation has it's advantages and
it's disadvantages. Use it where it makes sense, but be prepared to
put more hours into it than the parts salesman or the thesis writer is
likely to admit are needed.