Thanks for the responses.  I should clarify what we're doing so there's les=
s questions about our process.  This is a AC to DC boost controller/rectifi=
er with an output range of 320 to 400 volts.  Getting this to run efficient=
ly is important when you're pushing that many watts around.  Here's a few o=
ther points that were brought up:

- We are using 2 control loops, first is output voltage and second is curre=
nt feedback and is done cycle by cycle.  Both use a PI controller to meet t=
he target spec.
- Maximum power requires 85% duty cycle, minimum is around 25% to achieve s=
omething higher than passive rectification alone.
- Microchip ap note AN1106 (power factor correction in power conversion app=
lications) shows the adc triggers being done right at the start of the pwm =
period in figure 18 (timing logic).  Our concern is that this would read an=
y turn-on transient.

The intention is to have the adc read the voltage and current when it is at=
 a steady state for that time segment (25 uS) so we are now thinking that r=
ight after any turn-on transient would probably be the best point for that.=
  The dsPIC includes leading edge blanking for the current and fault limite=
rs but the adc is able to be triggered at any time.  Our logic is that we s=
hould either read while we are boosting or after it is returning to a stead=
y state at the end of the pwm period.  For now we're setting the trigger po=
int at 10% and continuing with that but we'd like to see if there are other=
 opinions on what is the best point for reading the current in particular.

Regards,
Andy
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