PWM generation in Simulink - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding PWM Signal Characteristics

Which parameter in a PWM signal directly controls the average voltage delivered to a load?

A Duty cycle of the PWM signal

B Amplitude of the carrier wave

C Frequency of the PWM signal

D Phase shift of the PWM signal

💡 Hint

Think about how the 'on' time affects power delivery.

The duty cycle defines the percentage of time the signal is 'on' during one period, controlling the average voltage.

❓ Predict Output

intermediate

Simulink PWM Block Output Behavior

Given a Simulink PWM Generator block configured with a 1 kHz frequency and a 40% duty cycle, what is the expected output waveform characteristic?

A A constant DC voltage at 40% of the supply voltage

B A square wave with 1 kHz frequency and 40% high time

C A sine wave with 1 kHz frequency and 40% amplitude

D A square wave with 40 kHz frequency and 1 kHz duty cycle

💡 Hint

Recall what a PWM signal looks like in time domain.

The PWM Generator outputs a square wave with specified frequency and duty cycle, so 1 kHz frequency and 40% 'on' time.

❓ data_output

advanced

Analyzing PWM Signal Data in Simulink Scope

You run a Simulink model with a PWM Generator block set at 2 kHz frequency and 75% duty cycle. The Scope block shows the output signal over 2 ms. How many complete PWM cycles appear in the Scope display?

A 4 complete cycles

B 8 complete cycles

C 1 complete cycle

D 2 complete cycles

💡 Hint

Calculate how many 0.5 ms periods fit into 2 ms.

At 2 kHz, each cycle is 0.5 ms. 2 ms / 0.5 ms = 4 cycles.

🔧 Debug

advanced

Identifying Error in PWM Duty Cycle Modulation

A Simulink model uses a PWM Generator block with a duty cycle input signal that varies from -10% to 110%. What error or unexpected behavior will most likely occur?

A The PWM signal amplitude doubles

B Simulink throws a runtime error due to invalid duty cycle values

C The PWM output frequency changes unexpectedly

D The PWM block clamps duty cycle to 0-100%, so no error but unexpected clipping

💡 Hint

Consider how duty cycle inputs outside valid range are handled.

Simulink PWM Generator clamps duty cycle inputs below 0% to 0% and above 100% to 100%, so no error but output duty cycle clips.

🚀 Application

expert

Designing a Simulink Model for Variable PWM Control

You want to design a Simulink model that adjusts PWM duty cycle based on a sensor input ranging from 0 to 5 volts, mapping 0 V to 10% duty cycle and 5 V to 90% duty cycle linearly. Which block combination correctly implements this mapping?

A Use a Gain block with gain 0.16 and a Bias block with bias 10, feeding into PWM duty cycle input

B Use a Gain block with gain 0.16 and a Bias block with bias -10, feeding into PWM duty cycle input

C Use a Gain block with gain 16 and a Bias block with bias 10, feeding into PWM duty cycle input

D Use a Gain block with gain 16 and a Bias block with bias -10, feeding into PWM duty cycle input

💡 Hint

Map 0 V to 10% and 5 V to 90% means slope = (90-10)/5 = 16, intercept = 10.

The linear equation is duty_cycle = 16 * sensor_voltage + 10. So gain=16 and bias=10.