AN3165

STM32 digital PFC

Doc ID 17180 Rev 1

11/31

Figure 3.

Use of peripherals for STM32 digital PFC

Table 1 describes the STM32 pins and their purpose.

2.5

Timing

The signal output from TIM3_CH4 is applied to the power MOSFET gate and its frequency

is fixed at 80 kHz; its duty cycle varies and is linked to the control strategy of the digital PFC.

TIM3_CH3 is used to trigger ADC1: a conversion is started at the end of each ON period.

The duty cycle of TIM3_CH3 is equal to half that of TIM3_CH4 but never lower than 1 µs to

avoid invalid conversions due to noise generated by the switching of the power MOSFET.

Figure 4 shows the triggering mechanism of TIM3, ADC and DMA1.

Table 1.

STM32F103ZE pin description

MCU pin

Description

MC + PFC connector

PA.03

Vdc – PFC output DC voltage

14

PA.04

Iac – PFC current

24

PA.05

Vac – input AC voltage

22

PC.09

PFC power MOSFET driver

29

PD.02

Vac zero-crossing detection

27

PD.10

Drives the relay to bypass the resistor when there is in-rush

current at start up

21

PE.01

PFC hardware overcurrent detection

2