SWCU195A December 2024 – May 2025 CC2744R7-Q1 , CC2745P10-Q1 , CC2745R10-Q1 , CC2745R7-Q1 , CC2755R10
The LGPT can be used to drive a BLDC motor. Consider a BLDC motor with three half bridges, this requires three or more channels. In this scenario, the three IOC and the three IOC complementary outputs of one LGPT are connected to a motor driver or directly to the half bridges. See Figure 12-15.
Here, each half bridge is controlled by an IOC and IOC complementary pair; that is, PWM0 and PWM1 correspond to IOC[0] and IOC_C[0], PWM2 and PWM3 to IOC[1] and IOC_C[1], and so on. To operate the motor in a basic fashion, current is driven through two of the inductors at a time in a sequential pattern. This is done by switching the transistors in a distinct pattern. See Figure 12-16.
Notice that the high time of each transistor consists of a PWM signal (as illustrated in Q0). The duty cycle of the PWM signal corresponds to the current that is driven through the inductors and consequently the motor speed/load. The PWM can be generated as mentioned in Section 12.3.6.2. The software interactions needed to operate the motor (We assume Q0 is connected to IOC[0] and Q1 connected to IOC_C[0] and so on) are as follows:
SW operations:
Software needs a signal to determine when to change between the different phases, this can, for example, be done by an ADC measuring the back (EMF) Electromotive Force at the inactive inductor. Software can also change phases only on a ZERO interrupt from LGPT to ensure complete PWM pulses during phase changes.