UCC28070: Output pwm

Hello Jacob, 

Thank you for your question on open-loop operation of the UCC28070 PFC controller. 

For test purposes without any high voltage applied, several signals must be manipulated manually to effect changes in PWM.

1.  Disable frequency dithering (if any) by connecting CDR to VREF and RDM to GND.  
2.  Use a lab supply to apply 3V to VINAC through a 10K resistor.
3.  Use another lab supply to apply 2.8V to VSENSE through a 10K resistor. 
4.  Use a signal generator to apply a waveform mimicking the signal normally seen at the CSx input. 
         You can try using two generators at the same time, but synchronizing will be difficult.  I suggest a single generator to one CSx input at a time.  The other input can be left floating, and ignore its corresponding PWM output.  Even so sync'ing one generator to the PFC frequency may still be tricky.  An alternative is to vary the offset voltage and ramp of the circuit from Figure 27 in the datasheet (if it is implemented) to get a CSx waveform that is similar to a real CT output.  
Adjust to obtain the PWM duty cycle that you desire. 
5.  Since VINAC is a DC signal, PWM will not vary.  The multiplier initializes into the lowest gain state.  To increase gain, VINAC must be reduced AND an artificial zero-crossing must be applied to trigger a gain change. Do that by very briefly shorting VINAC to GND.   If PFC-type variation is required, then a  low-voltage rectified-AC source must be applied to VINAC.
6.  Since the voltage error amp is an integrator, you cannot adjust VAO output simply by adjusting VSENSE.  I suggest to add a 200kR resistor from VAO to GND to act as a load on the source current.  Then VSENSE can be adjusted between 2.8V to 3.00V to raise or lower VAO to affect the IMO output.  VSENSE below about 2.79V will trigger the Slew-Rate Correction current, so try to keep VSENSE within the small-signal range (close to but less than 3.00V). 
A resistance much higher than 10kR from the lab supply to VSENSE can allow you to vary the supply voltage wider for better resolution on VSENSE variations.  

With those inputs, you should be able to vary the PWM of each phase independently.  

Regards,
Ulrich