Firmware Engineer (Power Tech)

About Ubiquiti

At Ubiquiti Inc., we create technology platforms for Businesses, Smart Homes, and Internet Service Providers, driven by our goal to connect everyone, everywhere. To date, Ubiquiti has shipped over 100 million devices worldwide, from ISP networking products to next generation of IT solutions. Our growth is made possible by the dedicated team of hundreds behind the scenes. From software developers and product managers to designers and strategists, Team UI is driven to achieve our common goal: Rethinking IT. At Ubiquiti, you’ll heighten your potential and broaden your horizons - all while shaping the future of connectivity.

Responsibilities

• Design and implement digital control loops (voltage, current, PLL, droop, etc.) for the rectifier, inverter, and DC/DC stages of Online UPS systems.
• Develop and tune control algorithms such as PI/PID, state feedback, repetitive control, and feedforward compensation for power conversion topologies.
• Implement high-frequency PWM/SVPWM generation, ADC sampling, and interrupt-driven real-time control on DSP/MCU platforms.
• Develop firmware for full UPS operating modes — online (double-conversion), eco, battery, and bypass — including seamless mode transitions.
• Implement battery charger control (CC/CV charging, charge/discharge management) and coordinate with the BMS for safe battery operation.
• Optimize control performance for transient response, output THD, efficiency, and stability across line and load conditions.
• Design firmware-level protection and fault-handling logic (OV/UV/OC/OTP, short-circuit, inrush, output overload).
• Perform bring-up, debugging, and waveform analysis using oscilloscopes, current probes, and emulators.
• Collaborate with power hardware, magnetics, and system engineers to co-tune control loops with the physical plant.
• Support compliance testing (efficiency, THD, hold-up time, EMI) and resolve firmware-related issues.

Minimum Qualifications

• Bachelor's or Master's degree in Electrical Engineering, Power Electronics, Control Engineering, or a related field.
• 7+ years of firmware development experience focused on digital power conversion.
• Proven track record of shipping Online UPS firmware — hands-on experience with rectifier, inverter, and bypass control is essential.
• Strong hands-on experience implementing digital control loops for switching power converters (PFC, inverter, bidirectional DC/DC, LLC, phase-shift full-bridge, etc.).
• Deep understanding of Power Factor Correction techniques — average current mode control, bridgeless / totem-pole PFC, interleaved PFC.
• Working knowledge of battery charge/discharge control, including CC/CV charging profiles, charger-to-BMS coordination, and battery protection.
• Proficiency with real-time control DSPs/MCUs (e.g., TI C2000, STM32 G4/H7, Infineon XMC, or equivalent); strong understanding of ePWM, ADC, and trip-zone style peripherals.
• Strong grasp of control theory: s-domain / z-domain analysis, Bode plot tuning, discretization (Tustin, ZOH), and loop compensation.
• Proficient in C/C++ and real-time, interrupt-driven embedded programming.
• Experience working with power stage waveforms and debugging closed-loop control issues on real hardware.

Preferred Qualifications

• Experience with 3-phase UPS, parallel/redundant UPS operation, or modular UPS architectures.
• Familiarity with MATLAB/Simulink, PLECS, or PSIM for control modeling and offline simulation; experience with model-based design or auto-code generation is a plus.
• Knowledge of advanced techniques such as digital PLL for grid synchronization, resonant control, or model predictive control (MPC).
• Experience addressing EMI/EMC issues through firmware (e.g., switching pattern shaping, spread spectrum).
• Familiarity with UPS-relevant safety and regulatory standards (IEC 62040, UL 1778, IEC 61000, etc.).
• Experience with version control (Git) and firmware architecture design for safety-critical, real-time systems.
• Ability to read power electronics schematics and collaborate closely with hardware engineers on loop tuning and stability.