Digital PFC Description
12.4.1
Background Loop
The firmware starts from function main(). In this function, after the system initialization, it goes to an infinite
loop. All the non-time critical tasks are put in this loop, it includes:
•
Calculate voltage feed forward.
•
Clear current offset at zero load.
•
System monitoring.
•
PMBus communication.
•
Primary and secondary UART communication.
NOTE:
User can always add any non-time critical functions in this loop.
12.4.2
Voltage Loop Configuration
The voltage control loop is a pure firmware loop. V
OUT
is sensed by a 12-bit ADC, and compared with
voltage reference. The error goes into a firmware Proportional-Integral (PI) controller, and its output is
used to do current loop reference calculations.
12.4.3
Current Loop Configuration
Current loop consists of several modules:
•
Front End (FE) Module, to configure the AFE block gain.
–
For single phase PFC, AFE0 is used.
•
Filter Module, to configure the current loop compensation.
–
FILTER1 is used.
•
DPWM Module, to generate the PWM signal driving PFC.
–
For single phase PFC, DPWM1B is used.
NOTE:
Loop Mux Module, to configure interconnection among front end, filter and DPWM modules.
12.4.4
Interrupts
There are two interrupts, the Standard Interrupt (IRQ), and the Fast Interrupt (FIQ).
•
IRQ contains the state machine and most of the PFC control firmware.
•
FIQ is used in relation to implementing OVP protections.
38
Digitally Controlled Single-Phase PFC Pre-Regulator
SLUU885B – March 2012 – Revised July 2012
Copyright © 2012, Texas Instruments Incorporated
