Freescale Semiconductor M68HC08 manual Synchronization Interrupt Routine, Freescale Semiconductor

Software Implementation

5.3.3 Synchronization Interrupt Routine

The interrupt procedure is used for trimming the internal oscillator and for synchronization of the phase shift of the reference sine wave with the mains voltage. A detailed illustration of this is shown in Figure 5-4.

interrupt void IRQisr(void)

Get actual timer value

Stop and reset timer

Run timer

Enable PI PFC stage regulator computing

Enable trimming value calculation

Reset sine wave table pointer

Clear IRQ flag

End of subroutine

Figure 5-4. Flow Chart — Synchronization Interrupt Routine

5.3.4 Sine Wave Generation Interrupt Routine

The PWM modulator is used to generate the reference sine wave for PFC control. The amplitude of generated sine wave depends on output DC-bus voltage and it is calculated by means of PI regulator. The phase shift of the sine wave is synchronized by means of IRQ interrupt that is launched by input AC voltage zero crossing detector. The table bSinTab[PWM_RELOADS] contains duty cycle values for PWM. These values can be calculated by means of worksheet PWM_Setup of the file DLB_Setup.xls (see Reference [4]). For service PWM reload interrupt the pwmISR() routine is used (see Figure 5-5). Moreover, inside the PWM, a counter generates a reload interrupt signal every 1 ms. This interval is used for software timing.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 43