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Newsgroups: sci.electronics.design
From: legg <l...@nospam.magma.ca>
Date: Sat, 05 Jul 2008 20:50:32 -0400
Local: Sun, Jul 6 2008 5:50 am
Subject: Re: Feedback for low frequency PWM regulator
On Fri, 04 Jul 2008 20:44:37 GMT, "JMini"
<j.minih...@minihane.tzo.com> wrote: Why ? >I'm building a PWM regulator for an incandescent bulb. Some of thos was >described in a thread called "RMS Approximation of PWM/Square wave". In any >case. Since there is no inductor/diode/cepacitor in the output stage I'll be >using an RMS converter (LTC1968). For the PWM section I'm using the MIC1557 >(SOT-23 size 555 equiv) for a R-C sawtooth to a comparator (TLV7211a) >inverting input. I can choose the frequency (probably in the 200-800Hz >range). The feedback is sent through the LTC1968 RMS converter to the FB pin >(0.8V) of a tiny (SC-70) 5mA voltage regulator (OnSemi NCP102). It's really >just a powerful error amplifier. The Output of that is sent to the >non-inverting input of the comparator. So if the feedback voltage drops, the >NCP102 increases voltage ot the non-inverting input of the TLV7211, thus >increasing duty cycle. I've tested this type of layout on breadboard using >different components. This sort of arrangement will hit the lamp with the mother of all Once stable (tee hee), you've got an rms voltage comparison to a What are you trying to do? RL You must Sign in before you can post messages.
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