STNRGPF01 datasheet(8/40 Pages) STMICROELECTRONICS

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STNRGPF01 block diagram

STNRGPF01

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DocID030377 Rev 2

3.1

Voltage and current loop

The STNRGPF01 implements mixed signal average current control. The task of the digital

voltage loop is to regulate the output voltage of the PFC. The VIN and IOUT measurements

are used to implement the input/output feed-forward (I/O FFD), so load steps or input

voltage variations are quickly compensated for by acting on digital PI output calculations.

This function allows keeping the output voltage at the set point value and as constant as

possible (see Figure 3).

Figure 3. Voltage loop and current reference

The output of the digital PI controller is the peak current reference. In order to obtain a

sinusoidal current reference, the Ipk_ref is multiplied by a lookup table (LUT). The LUT is

synchronized with the input voltage thanks to the ZVD signal (pin 17). The output of the

multiplier is a PWM signal with a sinusoidal duty cycle that is configured on pin 19 SIN REF.

An analog filter is used to obtain the final sinusoidal current reference for the external

current loop (itot_ref). The analog PI current compares the reference itot_ref with the total input

current feedback (itot_fb) and generates the duty cycle wave for the PWM modulation. The

master PWM signal is obtained by comparing (COMP2,3) the output of the PI current with a

triangular wave at switching frequency (see Figure 6: Analog comparators section and

Section 3.4: Driving and interleaving).

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