Calculation Of Pwm Duty Cycle - Renesas M16C/Tiny User Manual

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2.5 Calculation of PWM Duty Cycle

Sawtooth Wave

modulation

Output

Figure 3.1.4

PWM duty cycle depends on counting values of TAi. The actual rotation speed is proportion to

PWM duty cycle, the bigger is PWM duty cycle, the faster is the actual rotation speed. In the

course of approaching rotation speed command, the carrier wave cycle pulses can be acquired

by target rotation speed every time. Every result is saved a 1dimension array including 12 data

units. Then 12 elements are added to calculate average value, a current carrier wave pulses

between zero-crossings can be gotten.

According to formula 3.3.1, the current actual rotation speed will be gotten. Consequently, the

PWM duty cycle is changed according to the conditions given below.

Target rotation speed > Actual rotation speed

RSBJEUM0001-0101 Rev. 1.01

TB2

TAi

Slow

Fast

Relationship between PWM Duty Cycle and Rotation Speed Command

Condition

Amount of change

+ ∆ duty

- ∆ duty

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