In this DIY electronics project, we will design and build a DC motor driver circuit using the IRG7SC28U, an Insulated Gate Bipolar Transistor (IGBT). The IRG7SC28U is a versatile power transistor designed for high-speed switching applications and is ideal for driving DC motors. This project will demonstrate how to use the IRG7SC28U IGBT in a motor driver circuit, giving you the ability to control the speed and direction of a 28V DC motor.

The IRG7SC28U is well-suited for this task due to its high voltage and current handling capabilities. It allows for efficient switching and offers low conduction losses, making it an excellent choice for applications involving motors, where efficiency and speed control are crucial. We’ll build a simple motor driver circuit and discuss the key elements involved, including the IRG7SC28U's operation, circuit design, and motor control techniques.

Materials Needed:

1．IRG7SC28U IGBT (1 or 2 depending on motor configuration)

2．28V DC power supply

3．DC motor (rated for 28V)

4．H-Bridge driver circuit

5．Diodes (1N4007 for flyback protection)

6．Resistors (10kΩ, 220Ω)

7．Capacitors (100nF for smoothing)

8．Push buttons (for motor direction control)

9．Heat sinks (for IGBT cooling)

10．Potentiometer (for speed control)

11．Breadboard or PCB for assembling the circuit

12．Soldering tools (if making a permanent version)

13．Multimeter (for testing voltage and current)

Project Overview:

This project will focus on building a motor driver circuit that can drive a 28V DC motor using the IRG7SC28U IGBT. The main objective is to control the speed and direction of the motor based on the input from push buttons and a potentiometer for speed adjustment.

The IRG7SC28U is a high-performance IGBT that can handle significant current and voltage, making it ideal for controlling motors. The motor driver circuit will be built around an H-bridge configuration, which allows for bidirectional control of the motor, meaning the motor can rotate in both directions. The potentiometer will be used to adjust the speed of the motor, while the push buttons will allow for reversing the motor's direction.

Understanding the IRG7SC28U IGBT:

The IRG7SC28U is an IGBT that operates as a switch in high-speed applications. It combines the best characteristics of a MOSFET (voltage-controlled operation) and a BJT (high current handling capability). IGBTs like the IRG7SC28U are commonly used in power electronics to efficiently switch large loads, such as motors or high-power LEDs.

Key specifications of the IRG7SC28U:

1．Voltage rating: 1200V

2．Current rating: 28A

3．Gate threshold voltage: 5V

4．Low switching loss: Ideal for high-speed switching applications

5．Thermal performance: Needs heat sinking for efficient operation in power applications

In this project, the IGBT will act as a switching element within the H-bridge driver, controlling the flow of current to the DC motor. The H-bridge configuration will allow us to control both the speed (by adjusting the duty cycle of the pulse-width modulation, or PWM) and direction (by switching the polarity of the motor).

Circuit Design:

1. Power Supply:

The first step in the circuit is setting up the 28V DC power supply that will provide the voltage required to drive the motor. Connect the positive terminal of the power supply to the H-bridge circuit and the motor, ensuring the negative terminal is connected to the common ground of the circuit.

2. The H-Bridge Driver:

To allow both forward and reverse motion of the motor, we’ll use an H-bridge driver circuit. An H-bridge consists of four switching elements (in this case, two IGBTs per leg), which can be controlled to change the polarity of the voltage applied to the motor, thus changing the direction of rotation.

1．In the forward direction, one set of switches (IGBTs) will be ON, allowing current to flow in one direction through the motor.

2．In reverse, the other set of switches will be ON, reversing the polarity across the motor, and causing it to spin in the opposite direction.

Each IGBT in the H-bridge will be controlled by a gate signal. The gate drive circuitry for the IGBTs will ensure that the switching happens at the correct time. In this case, we will use 220Ω resistors to limit the gate current and protect the IGBT gates.

3. Speed Control with PWM:

To control the speed of the DC motor, we’ll use Pulse Width Modulation (PWM). By varying the width of the pulses, we control the average power delivered to the motor, thus adjusting its speed.

1．The PWM signal will be generated by a simple circuit using a 555 timer IC, a potentiometer, and resistors.

2．The potentiometer will be used to vary the duty cycle of the PWM signal, allowing for smooth adjustment of the motor’s speed.

4. Direction Control with Push Buttons:

To control the direction of the motor, we’ll use two push buttons. One button will set the motor to run in the forward direction, while the other button will reverse the direction. These buttons will control which pair of IGBTs in the H-bridge are turned on, thus reversing the current flow through the motor.

1．Button 1: Forward (switches one set of IGBTs ON)

2．Button 2: Reverse (switches the opposite set of IGBTs ON)

The push buttons will be wired in parallel with the gate signals of the IGBTs. When a button is pressed, it will trigger the corresponding gate drive circuitry to turn on the appropriate IGBTs in the H-bridge.

5. Flyback Diodes for Protection:

When driving motors, particularly inductive loads, it’s essential to protect the switching components from voltage spikes that occur when the motor is turned off. These spikes can damage the IGBTs if not properly mitigated.

To protect the IGBTs, we’ll add flyback diodes across each of the IGBT’s collector-emitter terminals. These diodes will provide a path for the current when the motor is suddenly turned off, preventing high-voltage spikes.

We’ll use 1N4007 diodes in this case, as they are well-suited for handling the inductive kickback from the motor.

6. Heat Sinking:

The IRG7SC28U IGBT can generate significant heat when switching large currents, especially in power applications like motor driving. To ensure that the IGBT operates efficiently and doesn’t overheat, you’ll need to attach a heat sink to the IGBT to dissipate heat.

The heat sink should be chosen based on the maximum current rating of the motor and the operating environment. A larger heat sink is necessary for higher currents.

Assembling the Circuit:

1. Power Supply and Motor: Connect the 28V power supply to the H-bridge circuit. The motor’s terminals are connected to the output side of the H-bridge.

2. H-Bridge Circuit: Using four IRG7SC28U IGBTs, construct the H-bridge. Connect the IGBTs in the configuration that allows current to flow through the motor in both directions when the IGBTs are switched.

3. PWM Speed Control: Set up the PWM circuit using a 555 timer and a potentiometer. Connect the output PWM signal to the gate of the IGBTs.

4. Direction Control: Connect the push buttons to the gate driver circuitry, ensuring that each button controls the correct pair of IGBTs in the H-bridge for forward and reverse motion.

5. Diodes and Heat Sinks: Add the flyback diodes for protection and attach heat sinks to the IGBTs.

Testing the Motor Driver:

Once the circuit is built, test the motor driver by:

1．Adjusting the potentiometer to vary the speed of the motor.

2．Pressing the forward and reverse buttons to change the direction of the motor.

Check the motor for smooth operation and ensure that the motor speed varies with the potentiometer setting. Also, verify that the direction changes as expected when the buttons are pressed.

Conclusion:

This DIY project demonstrates how to build a 28V DC motor driver circuit using the IRG7SC28U IGBT. The use of an H-bridge configuration, combined with PWM for speed control and push buttons for direction control, makes this circuit a versatile and powerful solution for driving DC motors.

By incorporating flyback diodes and heat sinks, we ensure the circuit remains reliable and efficient, even under load. This motor driver can be used in a wide range of applications, from robotics to automotive systems, offering precise control over the motor's speed and direction.