Triangle vs. sawtooth for PWM comparator

[rtarbell]

pwm comparator

I was initially taught that when converting a signal waveform to a PWM waveform, a triangle wave was compared to the input signal (via a comparator) and the PWM wave is the output of the comparator.

Why do some PWM ICs use a sawtooth wave instead of a triangle wave? What is the difference?

 

[Miguel Gaspar]

pwm sawtooth triangle

When you use a sawtooth the pwm pulse will be at the begining of the period, but in the triangular wave will be at the center of the period.