The curves in the following applet are related to the previous applet 'Bi- and Unipolar PWM'. The left hand side diagram shows waveforms for bipolar PWM, and the right hand side diagram for unipolar PWM. The signal m1(t) (and m2(t) with m2_uni= m1 and m2_bi = -m1) is now sinusoidal. The triangular signal's frequency is some orders of magnitude higher than the frequency of m1. Therefore, m1 can be assumed to be constant during a single switching period of the triangular signal (also called the 'carrier signal'). 

We assume a load consisting of an inductor in series with an AC voltage source as shown in the applet 'Hysteresis Control / Switching Frequency Variation'. The signal m1 defines the average of the block-shaped output voltage u2 which is approximately equal to its fundamental u2,(1). uLoad (blue) is the voltage of the AC voltage source on the load side. The difference between u2,(1) and uLoad is the voltage drop on the load side inductor shown as the green curve below. This defines the load current i2 (blue) which is shown (together with its fundamental and ripple) in the diagram below. 

The curves on the right hand side show the operation for unipolar PWM which is in principle the same. Due to the available zero-voltage level, the voltage pulses on the load side inductor are reduced by a factor of 2, and also the pulse frequency of uL is reduced by a factor of 2. Therefore, the current ripple di2 (magenta) is significantly reduced, although the switching frequency of the power switches and the related switching losses are equal for both modulation schemes. Also, the current ripple's frequency spectrum is shifted to higher frequencies.

• Drag the red points to change the frequency of the carrier signal. Lower frequency means higher ripple and increased filter component volume, but reduced switching losses and a smaller heat sink. These are the main considerations for an optimized design.
• Drag the red points to change the signal m1. m1 has to be very close to uLoad in order to control any kind of load current i2.