In this DIY electronics project, we’ll be focusing on building a high-power MOSFET switch circuit using the IRG7PH35UD1-E, a powerful IGBT (Insulated Gate Bipolar Transistor) module from Infineon Technologies. The IRG7PH35UD1-E is designed to handle high voltages (up to 1200V) and high currents (up to 35A), making it an excellent choice for switching heavy loads in power electronics, motor control, and industrial applications.

The aim of this project is to design a MOSFET switch circuit that can be used to control high-power devices such as motors, heating elements, or other high-voltage appliances. This circuit will use the IRG7PH35UD1-E to act as the switch, with the capability to control a high-power AC or DC load based on a low-voltage input, such as a microcontroller or a simple switch.

Project Overview: High-Power MOSFET Switch Circuit

In this project, the IRG7PH35UD1-E will serve as a high-power switch controlled by a low-power control circuit. We will use the MOSFET in a low-side switch configuration, where the IRG7PH35UD1-E will control the flow of current from a high-voltage DC or AC source to a load. The main objective is to design a simple and reliable circuit for switching high-power loads in a controlled manner, making this project suitable for use in home automation, motor control, or industrial power applications.

Components Needed

For this DIY high-power switch circuit, we’ll need the following components:

· IRG7PH35UD1-E IGBT Module (1 piece)

· Optocoupler (e.g., PC817 or similar) for isolation between the control and power sides

· Resistors:

o 1 kΩ for current limiting to the optocoupler LED

o 10 kΩ for the base of the IGBT

· Diode (e.g., 1N4007) for flyback protection (in case of inductive load)

· Capacitor: 100nF (to filter noise in the circuit)

· Heat Sink: To dissipate heat from the IGBT

· Control Switch: Can be a simple push-button switch, or a microcontroller (e.g., Arduino) for controlling the MOSFET

· DC or AC Load: For example, a small DC motor, fan, or high-power LED array

· External Power Source: Suitable for the load (e.g., 12V, 24V, or AC mains)

· Wires and Connectors: For connections

Understanding the IRG7PH35UD1-E

The IRG7PH35UD1-E is an IGBT module that combines the fast switching capabilities of a MOSFET with the high current and voltage handling capabilities of a bipolar transistor. This makes it ideal for power control applications, such as motor drives, high-power switches, and power supplies.

Key features of the IRG7PH35UD1-E include:

· Voltage Rating (Vce): 1200V, which allows it to safely control high-voltage loads.

· Current Rating (Ic): 35A, capable of handling moderate to high current loads.

· Low Saturation Voltage (Vce(sat)): Ensures low power dissipation during operation.

· Fast Switching Speed: Fast turn-on and turn-off characteristics, which are essential for efficient switching in power applications.

· Built-in Freewheeling Diode: Helps protect against inductive load kickback when switching inductive loads like motors or relays.

Step-by-Step Guide to Building the High-Power MOSFET Switch

Step 1: Circuit Design Overview

The circuit will consist of the following main sections:

1. Control Section: This part of the circuit will receive a low-power signal (e.g., from a microcontroller or a simple switch) and activate the optocoupler, which in turn will drive the base of the IGBT.

2. Power Section: This part will handle the high-voltage switching and includes the IRG7PH35UD1-E IGBT, the load (e.g., motor, light), and a flyback diode to protect against inductive kickback.

3. Protection Section: The flyback diode and heat sink will help protect the components and ensure the MOSFET operates within safe thermal limits.

Here’s a basic flow of how the circuit will work:

1. The control signal (from a microcontroller or switch) will activate the optocoupler, which will provide current to the base of the IRG7PH35UD1-E IGBT.

2. The IGBT will then allow current to flow from the collector to the emitter, turning on the connected load.

3. When the control signal goes low, the optocoupler will turn off, cutting off the base drive to the IGBT, which will stop the current flow to the load and switch the load off.

Step 2: Setting Up the Control Section

Optocoupler:

o The first component in the control section is the optocoupler (e.g., PC817). This provides electrical isolation between the low-voltage control circuitry (like a microcontroller or manual switch) and the high-voltage switching side of the circuit.

o Connect the anode of the optocoupler's LED to the control signal (from a microcontroller or manual switch). The cathode of the LED should be connected to ground through a 1 kΩ resistor to limit current.

Resistor for Base Drive:

o The phototransistor side of the optocoupler will drive the base of the IRG7PH35UD1-E IGBT.

o Connect the emitter of the optocoupler's phototransistor to ground, and the collector to the base of the IGBT through a 10 kΩ resistor to limit base current. This resistor helps ensure the IGBT switches on and off cleanly.

Step 3: Setting Up the Power Section

IGBT Module:

o The IRG7PH35UD1-E will be the main switching element. Connect the collector of the IGBT to the positive terminal of your DC or AC power supply.

o The emitter of the IGBT will be connected to one terminal of your load (e.g., a motor, heating element, or other high-power device). The other terminal of the load will be connected to ground.

Flyback Diode:

o If you are controlling an inductive load, like a motor or a relay, a flyback diode (e.g., 1N4007) should be placed across the load to protect the IGBT from voltage spikes when the load is turned off. The anode of the diode should be connected to the negative side of the load, and the cathode should be connected to the positive side.

Heat Sink:

o Attach an appropriate heat sink to the IGBT to dissipate heat. High-power IGBTs can generate substantial heat under load, so it is essential to manage thermal dissipation to prevent damage. If your load is going to draw substantial current, choose a large heat sink or active cooling methods.

Step 4: Assembling the Circuit

Power Supply:

o Connect the power supply to the collector of the IGBT. If using a DC supply, ensure the voltage is within the rated limits of the IGBT module (up to 1200V). For AC applications, appropriate rectification and filtering may be necessary, or a proper AC to DC conversion stage can be used.

Load Connection:

o Connect the other terminal of your load to the emitter of the IGBT. Make sure the load is rated to operate with the chosen voltage and current limits.

Testing the Control Signal:

o Apply a control signal to the optocoupler’s LED side. This could be a simple switch or a signal from a microcontroller. When the signal is high, the optocoupler will turn on the IGBT, allowing current to flow through the load.

o When the control signal is turned off, the optocoupler will turn off the IGBT, cutting the current to the load.

Step 5: Testing and Calibration

Testing the Control Section:

o Apply the control signal (high) and measure the output at the collector-emitter junction of the IGBT. You should see the voltage drop across the load, indicating that the IGBT is conducting.

o Turn off the control signal and measure the output again. The voltage should now be zero or very close to zero, indicating that the IGBT has turned off.

Heat Management:

o Measure the temperature of the IGBT during operation, especially under load. If the temperature rises too much, consider adding more cooling or adjusting the load current to prevent thermal damage.

Current Measurement:

o If you are using a current-limited power supply, measure the current drawn by the load while the IGBT is conducting. Ensure that it is within the safe operating limits of the IGBT.

Step 6: Troubleshooting

If the circuit does not work as expected, here are a few things to check:

· Optocoupler Orientation: Ensure that the optocoupler’s LED and phototransistor are connected correctly with the right orientation.

· IGBT Connections: Double-check that the collector, emitter, and gate of the IGBT are properly connected.

· Heat Dissipation: If the IGBT is overheating, check the current through the load and improve the cooling system.

· Flyback Diode: Ensure the flyback diode is connected correctly across the load, especially for inductive loads.

Conclusion

In this DIY project, we’ve successfully built a high-power MOSFET switch using the IRG7PH35UD1-E IGBT module. This circuit is capable of controlling high-power AC or DC loads with a low-power control signal, making it ideal for applications like motor control, power switching, and home automation.

By using an optocoupler for isolation, a flyback diode for protection, and a heat sink for thermal management, we’ve created a simple yet robust power switching solution. This project is a great foundation for building more complex high-power control circuits and can be adapted for a wide range of applications, including industrial machinery and renewable energy systems.