Re: continuous mode,current mode control, boost circuit

On Sat, 23 Feb 2008 09:21:03 -0800 (PST), reggie
<veggiedom@xxxxxxxxxxxxxx> wrote:


Why does a full wave rectified waveform, turns into what looks like a
good sinewave? This waveform is what is confusing me. I think it is
too pure to be power parasitic elements and have a hunch that it's
something to do with the control chip. I may be wrong it won't be the
first time!

I recall being somewhat perplexed at seeing what apparently was a
fairly cleen sinusoid myself, a decade or so ago. However the waveform
or my perplexity prevented the timely production of useful and
reliable hardware.

The old unitrode U-134 by Philip Todd has some theoretical waveforms
for you, with competent labeling for LF voltage, current and power.:

http://focus.ti.com/lit/an/slua144/slua144.pdf

As far as PFC methods and formulas go, these are many and varied,
making interesting reading, when you've got the time and inclination
to do so.

The eferenced app note applies to the 3854, a much more widely used
device with similar control inputs and design method.

The only MicroLinear PFC chip I ever directly encountered was the
ML4812, which, in it's initial release, had the annoying habit of
going inependantly active high on its mosfet driver output, at the
time of shutdown UVLO, for a period dependent upon the discharge time
of any capacitors that might be hanging on it's reference pin for
simple decoupling purposes. I believe they fixed that, eventually, but
it came as a surpise at the time, particularly in buck PFC
applications.

I think I've used a MicroLinear 8pin PFC/PWM combo controller since,
without too much trouble, except there still seemed to be issues with
supply consumption in and around the UVLO thresholds.


I need waveforms!!

Any ideas?

Make some.

RL
.

Relevant Pages

  • Re: continuous mode,current mode control, boost circuit
    ... This waveform is what is confusing me. ... too pure to be power parasitic elements and have a hunch that it's ... As far as PFC methods and formulas go, these are many and varied, ... The only MicroLinear PFC chip I ever directly encountered was the ...
    (sci.electronics.design)
  • Re: voltage to frequency converter circuit (VCO)
    ... able to create a square and triangle waveform easily and i've found ... I'm having trouble finding information about a voltage to ... the common way to do it is to use an op-amp integrator ... The control voltage input can be fed to an inverter to generate a ...
    (sci.electronics.design)
  • Re: How to eliminate horizonal overscan when no service adjustment?
    ... to tight enough tolerance to not need a width control. ... It's pin 32 of that chip, ... The waveform shown on the schematic shows it ... Output transitor, ...
    (sci.electronics.repair)
  • Re: Waveform Mini-Language
    ... wanted to "control" a waveform generator. ... And a waveform description language is exactly what I am devising.. ... I control the entire hardware and software design. ...
    (comp.arch.embedded)
  • Re: Circuit for converter AC 50Hz to 60Hz
    ... degrees, low for 120 degrees, open for 60 degrees waveform instead." ... I am using hardware implement only, how to control the on / off time ... for the FET? ...
    (sci.electronics.design)