Shown on this slide is an overview of the different driving methods. The black line in the top waveform is used to illustrate the most basic method, hard switching. As can be seen in the peaks on the rising and falling edges, this simple method will generate significant kickback and noise. The blue line shows soft switching which switches off operation before the switching phase. With this method reactive current is reduced. As a result, better efficiency and lower kickback and noise are seen than with hard switching. The next waveform shows two methods of bridged transformer-less drive, BTL. As shown in red, this is the most silent energization method. The trapezoidal waveform smooths out the current at phase switching, creating a very quiet drive. However, the efficiency suffers because during the ramping the driving transistor is in its linear region, consuming more power than if it were on or off. To combat this issue, the BTL-PWM method creates a trapezoidal shape but does not leave the driver transistors in the linear region of operation. This results in increased efficiency and a silent drive close in performance to BTL. The final waveform shows PWM switching drive. This method enables smooth current switching by changing the duty cycle at phase switching. The output transistor is never long in the linear region, enabling a highly efficient drive.