In summary, there are multiple ways of driving the fan motor, and each method has advantages and disadvantages. The most basic method is hard switching which can generate significant kickback and noise due to the peaks on the rising and falling edges. Soft switching which switches operation off before the switching phase which reduces reactive current and resulting in better efficiency, lower kickback, and noise than with hard switching. There are two methods of bridged transformer-less drive, BTL, which is the most silent energization method. In BTL the trapezoidal waveform smooths out the current at phase switching, creating a very quiet drive. The efficiency is poorer because while ramping the driving transistor is in the linear region, consuming more power than if it were on or off. The BTL-PWM method creates a trapezoidal shape but the driver transistors do not remain in the linear region of operation, which results in increased efficiency, plus a silent drive close in performance to BTL. The final method is the PWM switching drive, a method that enables smooth current switching by changing the duty cycle at phase switching. The output transistor does not remain in the linear region long, enabling a highly efficient drive. The type of application will dictate what type of motor drive method is preferred. If a silent drive is the most important requirement, a BTL drive method for a single-phase motor would be a good choice. If the requirement is a mixture of low noise and low power, choosing a BTL-PWM driver is good. Lastly, if power, price, and quietness are the main requirements, a PWM switched solution would be most likely choice.