New-Tech Europe Magazine | April 2017

Fig. 2: Control diagram of motor driver

non-overlapping output signals that stop the high- and low-side conducting at the same time. Ideally, the n- and p-channel MOSFETs should have the same on resistance (RDSon) and total gate charge QG to obtain the optimal switching performance. Therefore, while it would be good to choose a complementary pair of MOSFETs to match these parameters, in reality this is impossible due to their different construction; the chip size of the p-channel device must be two to three times that of the n-channel to match the RDSon performance. But the larger the chip size, the larger the effect of QG. Thus, when selecting the MOSFETs, it is important to decide whether RDSon or QG will have the biggest impact on switching performance and choose accordingly. Fault detection Exceeding the motor’s maximum allowable torque loading can cause

Fig. 3: Single-phase BLDC motor driver schematic diagram

the driver’s components. To avoid this, a dead-band delay can be

implemented using the CWG’s counter registers. This provides

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