Learn more about SimElectronics

H-Bridge - Model H-bridge motor driver

Library

Actuators & Drivers

Description

The H-Bridge block represents an H-bridge motor driver. The block has the following two Simulation mode options:

PWM — The H-Bridge output is a controlled voltage that depends on the input signal at the PWM port. If the input signal has a value greater than the Enable threshold voltage parameter value, the H-Bridge output is on and has a value equal to the value of the Output voltage amplitude parameter. If it has a value less than the Enable threshold voltage parameter value, the block maintains the load circuit using one of the following two Freewheeling mode options:
- A freewheeling diode and a semiconductor switch
- Two freewheeling diodes
The signal at the REV port determines the polarity of the output. If the value of the signal at the REV port is less than the value of the Reverse threshold voltage parameter, the output has positive polarity; otherwise, it has negative polarity.
Averaged — The H-Bridge output is:

Where:
- V_O is the value of the Output voltage amplitude parameter.
- V_PWM is the value of the voltage at the PWM port.
- A_PWM is the value of the PWM signal amplitude parameter.
- I_OUT is the value of the output current.
- R_ON is the Bridge on resistance parameter.

Set the Simulation mode parameter to Averaged to speed up simulations when driving the H-Bridge block with a Controlled PWM Voltage block. You must also set the Simulation mode parameter of the Controlled PWM Voltage block to Averaged mode. This applies the average of the demanded PWM voltage to the motor. The Averaged mode assumes that the effect 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.

Basic Assumptions and Limitations

The model has the following limitations:

If you are linearizing your model, set the Simulation mode parameter to Averaged and ensure that you have specified the operating point correctly. You can only linearize the H-Bridge block for inputs that are greater than zero and less than the PWM signal amplitude.

Dialog Box and Parameters

Enable threshold voltage

Threshold above which the voltage at the PWM port must rise to enable the H-Bridge output. This parameter is used only when the Simulation mode parameter is set to PWM. The default value is 2.5 V.

PWM signal amplitude

The amplitude of the signal at the PWM input. The H-Bridge block uses this parameter only when the Simulation mode parameter is set to Averaged. The default value is 5 V.

Reverse threshold voltage

When the voltage at the REV port is greater than this threshold, the output polarity becomes negative. The default value is 2.5 V.

Braking threshold voltage

When the voltage at the BRK port is greater than this threshold, the H-Bridge output terminals are short-circuited via the following series of devices:

One bridge arm
One bridge arm in parallel with a conducting freewheeling diode

The default value is 2.5 V.

Output voltage amplitude

The amplitude of the voltage across the H-Bridge output ports when the output is on. The default value is 12 V.

Simulation mode

Select one of the following options for the type of output voltage:

PWM — The output voltage is a pulse-width modulated signal. This is the default option.
Averaged — The output voltage is a constant whose value is equal to the average value of the PWM signal.

Freewheeling mode

Select one of the following options for the type of H-Bridge dissipation circuit:

Via one semiconductor switch and one freewheeling diode — In this mode, the block controls the load by maintaining one high-side bridge arm permanently on and using the PWM signal to modulate the corresponding low-side bridge arm. This means that the block uses only one of the freewheeling diodes in completing the dissipation circuit when the bridge turns off. This option is the default.
Via two freewheeling diodes — In this mode, all bridge arms are off during the bridge off-state. This means that the block dissipates the load current across the power supply by two freewheeling diodes.

This parameter is only visible when you select PWM for the Simulation mode parameter.

Total bridge on resistance

The total effective resistance of the two semiconductor switches that connect the load to the two power rails when the voltage at the PWM port is greater than the Enable threshold voltage. The default value is 0.1 Ω.

Freewheeling diode on resistance

The total resistance in the freewheeling diodes that dissipate the current that flows through the motor when the voltage at the PWM port is less than the Enable threshold voltage. This parameter is only visible when you select PWM for the Simulation mode parameter. The default value is 0.1 Ω.

Ports

The block has the following ports:

+ref: Positive electrical output voltage.
-ref: Negative electrical output voltage.
PWM: Pulse-width modulated signal. The voltage is defined relative to the REF port.
REF: Floating zero volt reference.
REV: Voltage that controls when to reverse the polarity of the H-Bridge output. The voltage is defined relative to the REF port.
BRK: Voltage that controls when to short circuit the H-Bridge output. The voltage is defined relative to the REF port.

Examples

See the Controlled DC Motor, Linear Electrical Actuator (System-Level Model) and Linear Electrical Actuator (Implementation Model) demos.

Generic Rotary Actuator

Incremental Shaft Encoder

Related Products & Applications

Get Simulink trial software

Learn more about Simulink through this collection of videos, articles, technical literature and the Getting Started with Simulink Guide.

Get this Simulink Kit