SimElectronics™

Controlled PWM Voltage - Model pulse-width modulated voltage source

Library

Actuators & Drivers

Description

The Controlled PWM Voltage block represents a pulse-width modulated (PWM) voltage source that depends on the reference voltage V_ref across its +ref and -ref ports. The duty cycle is

where:

V_min is the minimum reference voltage
V_max is the maximum reference voltage

The value of the Output voltage amplitude parameter determines amplitude of the output voltage.

At time zero, the pulse is initialized as high, unless the duty cycle is set to zero.

Basic Assumptions and Limitations

The model is based on the following assumptions:

The REF output of this block is floating, i.e. it is not tied to the Electrical Reference. One consequence of this is that if you connect the PWM and REF electrical ports directly to the H-Bridge PWM and REF electrical ports, you must attach an Electrical Reference block to the REF connection line.
Do not use the Controlled PWM block to drive a motor block directly. A PWM motor driver goes open circuit in between pulses. Use the H-Bridge block to drive a motor block.
Set the Simulation mode parameter to Averaged to speed up simulations when driving a motor via the H-Bridge block. You must also set the Simulation mode parameter of the H-Bridge block to Averaged mode. This applies the average of the demanded PWM voltage to the motor. The Averaged mode assumes that the impedance of the motor inductive term is small at the PWM frequency. To verify this assumption, run the simulation using the PWM mode and compare the results to those obtained from using the Averaged mode.

Dialog Box and Parameters

PWM frequency: Frequency of the PWM output signal. The default value is 1000 Hz.
Input value Vmin for 0% duty cycle: Value of the input voltage at which the PWM signal has a 0% duty cycle. The default value is 0 V.
Input value Vmax for 100% duty cycle: Value of the input voltage at which the PWM signal has a 100% duty cycle. The default value is 5 V.
Output voltage amplitude: Amplitude of the PWM signal when the output is high. The default value is 5 V.
Simulation mode: The type of output voltage can be PWM or Averaged. The default mode, PWM, produces a pulse-width modulated signal. In Averaged mode, the output is a constant whose value is equal to the average value of the PWM signal.

Ports

The block has the following ports:

+ref: Positive electrical reference voltage.
-ref: Negative electrical reference voltage.
PWM: Pulse-width modulated signal.
REF: Floating zero volt reference.

Examples

See the Linear Electrical Actuator (System-Level Model) and Linear Electrical Actuator (Implementation Model) demos.