Signal\Block Diagram Non-Linear
Domains: Discrete, Continuous. Size: 1-D. Allowed in: Block Diagrams.
Pulse width modulation (PWM) is a powerful technique for controlling analog circuits with a processor's digital outputs. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. The output of a PWM block is a pulse train. The duty cycle, (the time that a pulse is on divided by the time the pulse is off) is proportional to the value of the input signal if the input is within the range < -input_amp , +input_amp >. For Bipolar PWM the output signal witches between a positive and a negative value. For Unipolar PWM the output signal witches between zero and positive or negative value.
|
input |
bipolar PWM |
Unipolar PWM |
|
> input_amp |
100% output_amp 0% -output_amp |
100% output_amp 0% 0 |
|
input_amp |
100% output_amp 0% -output_amp |
100% output_amp 0% 0 |
|
0.5*input_amp |
75% output_amp 25% -output_amp |
50% output_amp 50% 0 |
|
0 |
50% output_amp 50% -output_amp |
0 |
|
-0.5*input_amp |
25% output_amp 75% -output_amp |
50% 0 50% -output_amp |
|
-input_amp |
0% output_amp 100% -output_amp |
0% 0 100% -output_amp |
|
<-input_amp |
0% output_amp 100% -output_amp |
0% 0 100% -output_amp |
An example is shown in the graph below. The parameter input_amp is equal to 1 and the parameter max output is equal to 5. The frequency of the PWM signal is 10 Hz.
Bipolar and Unipolar PWM conversion.
Inputs |
Description |
input |
|
Outputs |
|
output |
|
Parameters |
|
f input_amp output_amp |
The modulating frequency [Hz]. Maximum value of the input signal. The output value will switch between output_amp, 0 and -output_amp. |