Isolated Half-Bridge Motor Driver

A robust, single half-bridge motor driver featuring galvanic PWM isolation and high-resolution bidirectional current sensing. Designed to safely interface a microcontroller with high-voltage motor rails while providing precise analog current feedback.

Project Status

• Hardware: Complete (KiCad schematic and PCB layout finalized).
• Firmware: C++ driver code currently in development.

Key Hardware Specifications

• Gate Driver: IR2101 with bootstrap topology (1N5819 diode / 1uF cap).
• Power Stage: 2x IRFZ44N N-Channel MOSFETs with 1000uF bulk smoothing.
• Galvanic Isolation: 2x 6N137 high-speed optocouplers protecting the logic side.
• Current Sensing: AD8418 bidirectional amplifier across an R002 milliohm shunt, heavily filtered (10Ω/10nF/1nF).
• Reference Voltage: Buffered 1.65V rail generated via MCP6002 for center-biased bidirectional sensing.

Interface & Pinout

Logic Side (Low Voltage)

• PWM_H / PWM_L: 2-Channel high-speed logic inputs (isolated via 6N137).
• I_SENSE_OUT: Amplified analog voltage representing motor current (centered at 1.65V).
• VCC_LOGIC: Input for the onboard LDO stepping down to power the opto-secondaries and IR2101.
• GND: Logic ground.

Power Side (High Voltage)

• MOTOR_V+: Main high-voltage power rail.
• MOTOR_OUT: Half-bridge switching output to the motor.
• GND_PWR: Power ground (isolated from logic ground).

Repository Structure

• /Hardware - KiCad project files (.kicad_pro, .kicad_sch, .kicad_pcb).
• /Docs - PDF schematics, board renders, and full CSV Bill of Materials.
• /Firmware - Placeholder for the upcoming C++ hardware abstraction and control classes.

Usage Notes

The design utilizes a bootstrap capacitor (C3) for the high-side MOSFET. The low-side MOSFET must be periodically pulsed on to recharge the bootstrap capacitor; do not attempt 100% duty cycle on the high side.