UM0324 datasheet(42/105 Pages) STMICROELECTRONICS

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Library functions

UM0324

42/105

Furthermore, you have the possibility to add any A/D conversions required for your

application (hereafter referred to as general purpose conversions). This section describes

how this is achieved.

First of all, the SVPWM_3ShuntInit function performs the synchronization between PWM

and TIM0 peripherals (Figure 21 shows the two peripheral counters when REP_RATE = 1),

then, the A/D converter peripheral is configured so that it is triggered by the TIM0 OC2

signal.

Figure 21.

PWM and TIM0 synchronization (REP_RATE=1)

This way, when the value of the TIM0 counter matches the value contained in the OCR2

Meanwhile, a DMA transaction reloads the TIM0 OCR2 register with the value

corresponding to the delay required for the second current sampling conversion. Moreover,

the end of this first A/D conversion triggers another DMA transaction which sets the next

channel to be converted in the ADC register CLR2.

At the end of the second conversion, the three-phase load current has been updated and

the IFOC algorithm can then be executed in the A/D End of Conversion Interrupt Service

Routine (EOC ISR). In this routine, the A/D converter is also reconfigured so that it can

perform the general purpose chain of conversions while the CPU executes the IFOC

algorithm.

The entire process is illustrated in Figure 22.

After execution of the IFOC algorithm, the A/D converter is configured to perform the next

PWM period three-phase current sensing (delays and channels). This allows to reduce the

CPU load (lower number of ADC ISR) and limits to 6 (@ 7.5 MHz ADC peripheral clock) the

number of general purpose A/D conversions that can be performed in each PWM period.

To specify the general purpose conversions to be performed, you can select the first channel

and the number of channels to be converted by editing the

GP_CONVERSIONS_FIRST_CHANNEL

and GP_CONVERSIONS_NUMBER parameters

respectively in the MC_pwm_3shunt_prm.h header file.

UM0324 Datasheet(PDF) 42 Page - STMicroelectronics