H-bridge driver simulation in Simulink - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the H-bridge operation

Which statement best describes the function of an H-bridge in motor control?

A It converts AC voltage to DC voltage for the motor.

B It increases the voltage supplied to the motor to boost speed.

C It measures the motor speed and adjusts the current accordingly.

D It allows the motor to run forwards and backwards by controlling the polarity of the voltage applied.

💡 Hint

Think about how direction control is achieved in DC motors.

An H-bridge switches the polarity of the voltage across the motor terminals, enabling forward and reverse rotation.

❓ Predict Output

intermediate

Simulink block output for H-bridge input signals

Given a Simulink model of an H-bridge with inputs IN1=1, IN2=0, what is the expected output voltage polarity across the motor terminals?

Simulink

IN1 = 1;
IN2 = 0;
% Output voltage polarity: +V to terminal A, 0V to terminal B

A Both terminals are at 0V (motor stopped).

B Motor terminal A is negative, terminal B is positive (reverse rotation).

C Motor terminal A is positive, terminal B is negative (forward rotation).

D Both terminals are at positive voltage (short circuit).

💡 Hint

Check which input is high and which is low to determine polarity.

IN1=1 and IN2=0 causes the H-bridge to apply positive voltage to terminal A and ground terminal B, resulting in forward rotation.

❓ data_output

advanced

Simulated PWM signal effect on motor speed

In a Simulink H-bridge model, a PWM signal with 50% duty cycle is applied to the enable pin. What is the expected average voltage across the motor terminals?

Simulink

PWM_duty = 0.5;
V_supply = 12; % volts
V_avg = PWM_duty * V_supply;

A 6 volts average voltage across the motor terminals.

B 12 volts average voltage across the motor terminals.

C 0 volts average voltage across the motor terminals.

D 24 volts average voltage across the motor terminals.

💡 Hint

Average voltage is supply voltage multiplied by PWM duty cycle.

With 50% duty cycle PWM, the motor receives half the supply voltage on average, so 6 volts.

🔧 Debug

advanced

Identify the error in H-bridge input signals causing short circuit

In a Simulink H-bridge model, both IN1 and IN2 inputs are set to 1 simultaneously. What is the likely outcome?

A Motor runs at maximum speed forward.

B Short circuit occurs because both high-side switches are on, damaging the circuit.

C Motor runs at maximum speed reverse.

D Motor stops safely with no voltage applied.

💡 Hint

Consider what happens if both sides of the H-bridge are connected to the supply voltage at the same time.

Both IN1 and IN2 high turns on both high-side switches, causing a direct short from supply to ground, which can damage components.

🚀 Application

expert

Designing a Simulink model for bidirectional motor control

You want to simulate a bidirectional DC motor control using an H-bridge in Simulink. Which input signal combination correctly achieves forward, reverse, and stop states?

A Forward: IN1=1, IN2=0; Reverse: IN1=0, IN2=1; Stop: IN1=0, IN2=0

B Forward: IN1=0, IN2=0; Reverse: IN1=1, IN2=1; Stop: IN1=1, IN2=0

C Forward: IN1=1, IN2=1; Reverse: IN1=0, IN2=0; Stop: IN1=0, IN2=1

D Forward: IN1=0, IN2=1; Reverse: IN1=1, IN2=0; Stop: IN1=1, IN2=1

💡 Hint

Recall the polarity needed for forward and reverse motor rotation and what input combination stops the motor.

Forward rotation is achieved by IN1=1 and IN2=0, reverse by IN1=0 and IN2=1, and stop by both inputs low (0,0) to avoid short circuits.

Practice

1. What is the main purpose of an H-bridge in motor control simulation?

easy

A. To control the direction of the motor by switching current paths

B. To increase the motor speed beyond its maximum rating

C. To convert AC power to DC power for the motor

D. To measure the temperature of the motor during operation

Solution

1. Step 1: Understand H-bridge function

   An H-bridge is designed to control the direction of current flow through a motor.

2. Step 2: Relate to motor control

   By switching current paths, it changes motor rotation direction safely.

3. Final Answer:

   To control the direction of the motor by switching current paths -> Option A

4. Quick Check:

   H-bridge controls motor direction = A [OK]

Hint: Remember: H-bridge switches current to change motor direction [OK]

Common Mistakes:

• Confusing H-bridge with power conversion devices
• Thinking it measures motor parameters
• Assuming it increases motor speed directly

2. Which Simulink block is typically used to represent the switches in an H-bridge driver simulation?

easy

A. Scope block

B. Gain block

C. Integrator block

D. Switch block

Solution

1. Step 1: Identify switch representation

   In Simulink, the Switch block models on/off states like switches in an H-bridge.

2. Step 2: Exclude other blocks

   Gain changes signal magnitude, Integrator accumulates signals, Scope displays signals, none act as switches.

3. Final Answer:

   Switch block -> Option D

4. Quick Check:

   Switch block models switches = A [OK]

Hint: Switch block simulates on/off control in Simulink [OK]

Common Mistakes:

• Choosing Gain block thinking it switches signals
• Confusing Scope with control elements
• Using Integrator block for switching

3. Consider this Simulink logic for an H-bridge driver:
Switch1 = ON, Switch4 = ON, Switch2 = OFF, Switch3 = OFF
What is the motor direction output?

medium

A. Motor direction is undefined

B. Motor rotates forward

C. Motor is stopped

D. Motor rotates backward

Solution

1. Step 1: Analyze switch states

   Switch1 and Switch4 ON means current flows in one diagonal path of the H-bridge.

2. Step 2: Determine motor direction

   This diagonal current flow causes the motor to rotate forward.

3. Final Answer:

   Motor rotates forward -> Option B

4. Quick Check:

   Diagonal switches ON = forward rotation [OK]

Hint: Diagonal switches ON means forward rotation [OK]

Common Mistakes:

• Assuming any two switches ON cause stop
• Confusing diagonal switch pairs
• Ignoring OFF switches effect

4. In a Simulink H-bridge model, the motor does not rotate even though Switch1 and Switch4 are ON. What is the most likely error?

medium

A. Switch1 and Switch4 are connected incorrectly in the model

B. The motor block is missing from the Simulink model

C. Switch2 and Switch3 are also ON causing a short circuit

D. The power supply block is disconnected

Solution

1. Step 1: Check switch connections

   If Switch1 and Switch4 are ON but motor doesn't rotate, wiring may be incorrect.

2. Step 2: Exclude other causes

   Switch2 and Switch3 ON causes short, not no rotation; missing motor or power would cause no output but question states switches ON.

3. Final Answer:

   Switch1 and Switch4 are connected incorrectly in the model -> Option A

4. Quick Check:

   Incorrect wiring stops motor despite switches ON [OK]

Hint: Check wiring if switches ON but motor stays still [OK]

Common Mistakes:

• Assuming short circuit causes no rotation instead of damage
• Ignoring wiring errors
• Overlooking power supply connection

5. You want to simulate a motor braking effect using an H-bridge in Simulink. Which switch configuration achieves this?

hard

A. Turn ON both switches on opposite diagonal (Switch1 and Switch4 ON)

B. Turn ON both switches on the same side (Switch1 and Switch2 ON)

C. Turn ON both switches on the same diagonal (Switch2 and Switch3 ON)

D. Turn OFF all switches

Solution

1. Step 1: Understand braking in H-bridge

   Braking is done by shorting motor terminals, which happens when switches on the same diagonal are ON.

2. Step 2: Identify correct switch pair

   Switch2 and Switch3 ON short motor terminals, causing braking effect.

3. Final Answer:

   Turn ON both switches on the same diagonal (Switch2 and Switch3 ON) -> Option C

4. Quick Check:

   Same diagonal switches ON = braking [OK]

Hint: Same diagonal switches ON short motor for braking [OK]

Common Mistakes:

• Confusing diagonal switches with braking
• Turning OFF all switches thinking it brakes
• Using opposite diagonal switches for braking