A three-phase motor is driven from a three-phase AC input. It us used to control the motor’s speed and torque, ensuring efficient operation.
"blocks": [ { "name": "Three Phase AC IN", "function": "Provides the three-phase AC mains input to the drive.", "theory_of_operation": "Utility/grid three-phase source feeding the front-end filter and rectification stages.", "interaction": "Feeds the EMC Filter.", "category": "Third party", "connection": ["EMC Filter"] }, { "name": "EMC Filter", "function": "Mitigates conducted/radiated emissions and improves immunity at the mains interface.", "theory_of_operation": "Common-mode chokes and X/Y capacitors form differential and common-mode filters to meet EMC limits.", "interaction": "Conditions the AC input and delivers filtered power to the AC/DC Converter.", "category": "Third party", "connection": ["AC/DC Converter", "Auxiliary power Supply", "Sensing & Isolation"] }, { "name": "AC/DC Converter", "function": "Rectifies and conditions the three-phase AC to a high-voltage DC bus for the drive and auxiliaries.", "theory_of_operation": "Three-phase diode or active rectifier with bulk capacitors and optional PFC produces a stable HVDC bus.", "interaction": "Supplies HVDC to DC/DC Converter and Inverter Stage & Brake; feedback through Sensing & Isolation; switches driven by Gate Driver if active front-end.", "category": "onsemi", "connection": ["DC/DC Converter", "Sensing & Isolation"] }, { "name": "DC/DC Converter", "function": "Generates isolated/regulated low-voltage rails from the HVDC bus for control and drivers.", "theory_of_operation": "High-frequency isolated/non-isolated topologies (e.g., flyback, buck) provide tightly regulated rails.", "interaction": "Powers Gate Driver, Sensing & Isolation, MCU, MCU Interface, and Support Circuitry; monitored by Sensing & Isolation; may be PWM-controlled via Gate Driver.", "category": "onsemi", "connection": ["Sensing & Isolation", "Inverter Stage & Brake"] }, { "name": "Inverter Stage & Brake", "function": "Creates variable-frequency three-phase output and manages dynamic braking.", "theory_of_operation": "A 3-phase bridge (IGBTs/MOSFETs) PWM-modulates the HVDC bus; a chopper and brake resistor dissipate regenerated energy.", "interaction": "Drives the Three Phase Motor; current/voltage sensed by Sensing & Isolation; switches are driven by Gate Driver.", "category": "onsemi", "connection": ["Three Phase Motor", "Sensing & Isolation"] }, { "name": "Three Phase Motor", "function": "Converts electrical power to mechanical torque/speed.", "theory_of_operation": "Stator AC excitation produces a rotating magnetic field that induces rotor torque (e.g., PMSM/IM).", "interaction": "Receives three-phase power from the Inverter Stage & Brake.", "category": "Third party", "connection": ["Inductive Sensor"] }, { "name": "Gate Driver", "function": "Provides high-current, level-shifted and/or isolated gate drive to power switches.", "theory_of_operation": "Miller-immune drivers with UVLO and DESAT; may use isolated drivers or digital isolators for primary/secondary separation.", "interaction": "Receives PWM/enable from MCU; drives switches in AC/DC Converter (if active front-end), DC/DC Converter, and Inverter Stage & Brake; powered by Auxiliary/low-voltage rails.", "category": "onsemi", "connection": ["AC/DC Converter", "DC/DC Converter", "Inverter Stage & Brake"] }, { "name": "Sensing & Isolation", "function": "Measures phase currents, bus voltages, temperatures and communicates them across safety isolation.", "theory_of_operation": "Shunts/HV dividers with isolated amplifiers or sigma-delta modulators; isolated ADCs or digital isolators transport data to the control domain.", "interaction": "Monitors AC/DC Converter, DC/DC Converter, and Inverter Stage & Brake; delivers conditioned/isolated signals to MCU.", "category": "onsemi", "connection": ["MCU"] }, { "name": "Inductive Sensor", "function": "Provides rotor position/speed feedback for FOC/commutation.", "theory_of_operation": "Eddy-current or resolver-style inductive sensing that outputs sinusoidal or conditioned digital position signals.", "interaction": "Interfaces to the MCU via the MCU Interface (e.g., amplifier/comparator or dedicated interface).", "category": "onsemi", "connection": ["MCU"] }, { "name": "Auxiliary Power Supply", "connection": ["MCU", "Gate Driver", "Sensing & Isolation", "MCU Interface", "Inductive Sensor"], "sub_blocks": [ { "name": "Controllers", "function": "PWM and regulation control for isolated/non-isolated auxiliary converters.", "theory_of_operation": "Implements current/voltage-mode control, start-up and protections for primary power stages.", "interaction": "Drives primary MOSFETs and regulates auxiliary outputs.", "category": "onsemi", "connection": [] }, { "name": "Converters", "function": "Point-of-load and intermediate rail conversion for logic and drivers.", "theory_of_operation": "Synchronous buck/boost and flyback stages provide efficient regulated rails.", "interaction": "Feed MCU, Gate Driver and sensing rails.", "category": "onsemi", "connection": [] }, { "name": "Circuit Protection", "function": "Protects low-voltage rails and loads from surge, ESD and short-circuit events.", "theory_of_operation": "TVS/eFuse/thermal protection elements limit energy and disconnect faults.", "interaction": "Safeguards all auxiliary outputs and downstream ICs.", "category": "onsemi", "connection": [] }, { "name": "Offline Controllers", "function": "Primary-side control for isolated auxiliary supplies from HVDC or mains.", "theory_of_operation": "High-voltage startup with PSR/SSR loops and integrated protections.", "interaction": "Regulates transformer primary and biases secondaries.", "category": "onsemi", "connection": [] }, { "name": "Offline Regulator", "function": "Bias supply generation directly from the HV bus or mains.", "theory_of_operation": "Linear or switching conversion from high voltage to logic-level rails.", "interaction": "Provides bias to controllers, drivers and sensing front-ends.", "category": "onsemi", "connection": [] }, { "name": "LDO Regulator", "function": "Low Dropout Regulator for stable, low-noise voltage supply.", "theory_of_operation": "Linear regulation for noise-sensitive analog and digital rails.", "interaction": "Polishes rails for MCU, analog front-ends and transceivers.", "category": "onsemi", "connection": [] }, { "name": "Diode", "function": "Rectification, OR-ing and clamping in the auxiliary paths.", "theory_of_operation": "PN/Schottky conduction and recovery characteristics define efficiency and protection.", "interaction": "Used in rectifiers, freewheeling and surge clamps.", "category": "onsemi", "connection": [] }, { "name": "MOSFETs", "function": "Switching devices for auxiliary converters and load management.", "theory_of_operation": "Enhancement-mode FETs used in synchronous stages and power switches.", "interaction": "Controlled by controllers/PMICs to regulate rails and sequencing.", "category": "onsemi", "connection": [] }, { "name": "Load Switch", "function": "Rail gating and sequencing with current limiting and soft-start.", "theory_of_operation": "Integrated FET with control and protection circuits.", "interaction": "Distributes rails selectively to subsystems.", "category": "onsemi", "connection": [] }, { "name": "PMIC", "function": "Multi-rail power management in a single device.", "theory_of_operation": "Integrates DC/DCs, LDOs and monitoring in one IC.", "interaction": "Centralizes rail generation for digital/control domains.", "category": "onsemi", "connection": [] } ] }, { "name": "Support Circuitry", "connection": [], "sub_blocks": [ { "name": "Zener Diode", "function": "Voltage clamping and simple references.", "theory_of_operation": "Operates in avalanche breakdown for a near-constant voltage.", "interaction": "Protects inputs and sets reference points in analog circuits.", "category": "onsemi", "connection": [] }, { "name": "Level Translator", "function": "Bridges differing logic voltage domains.", "theory_of_operation": "Bidirectional level shifting using MOS pass-gates or buffer architectures.", "interaction": "Interfaces MCU logic with 5 V/3.3 V/1.8 V peripherals.", "category": "onsemi", "connection": [] }, { "name": "Logic", "function": "Glue logic for timing, gating and state control.", "theory_of_operation": "CMOS gates, latches and flip-flops implement discrete digital functions.", "interaction": "Coordinates control signals among subsystems.", "category": "onsemi", "connection": [] }, { "name": "Small Signal", "function": "Analog conditioning such as amplification and filtering.", "theory_of_operation": "Precision op-amps/comparators/filter networks tailor bandwidth and gain.", "interaction": "Front-ends sensors and feedback channels before ADC/MCU.", "category": "onsemi", "connection": [] }, { "name": "GPIO Expander", "function": "Adds additional digital I/O pins to the controller.", "theory_of_operation": "I²C/SPI device maps serial commands to parallel GPIO.", "interaction": "Extends MCU pin count for controls and indicators.", "category": "onsemi", "connection": [] }, { "name": "Voltage Reference", "function": "Provides stable reference for ADCs/DACs and precision comparators.", "theory_of_operation": "Bandgap/curvature-corrected references with low tempco and noise.", "interaction": "Stabilizes measurement accuracy across temperature and supply variations.", "category": "onsemi", "connection": [] }, { "name": "BJTs & BRTs", "function": "Discrete amplification, level shifting and bias networks.", "theory_of_operation": "Bipolar devices; BRT integrates resistors to simplify biasing.", "interaction": "Implements drivers, pull-ups and signal buffers.", "category": "onsemi", "connection": [] }, { "name": "Voltage Supervisor", "function": "Monitors rails and asserts reset/PG signals.", "theory_of_operation": "Window/threshold comparators with hysteresis and timing.", "interaction": "Supervises MCU and critical rails for safe startup/shutdown.", "category": "onsemi", "connection": [] } ] }, { "name": "MCU", "function": "Real-time control (FOC, PWM generation, protections, communications).", "theory_of_operation": "DSP/MCU executes control loops using isolated measurements and commands gate drivers.", "interaction": "Exchanges control/telemetry with Gate Driver and Sensing & Isolation; interfaces with field networks via MCU Interface; powered by Auxiliary rails.", "category": "Third party", "connection": ["Gate Driver", "MCU Interface"] }, { "name": "MCU Interface", "connection": ["MCU"], "sub_blocks": [ { "name": "Memory", "function": "Nonvolatile code/data storage for control firmware and logs.", "theory_of_operation": "Serial NOR/NAND/EEPROM/FRAM accessed via SPI/I²C.", "interaction": "Provides program storage and parameter logging for the MCU.", "category": "onsemi", "connection": [] }, { "name": "Flexray", "function": "Deterministic automotive/industrial network interface.", "theory_of_operation": "Time-triggered, dual-channel communication for high reliability.", "interaction": "Provides robust, synchronized communication between controllers.", "category": "onsemi", "connection": [] }, { "name": "ESD Protection", "function": "Protects external interfaces from ESD and surge transients.", "theory_of_operation": "Low-capacitance TVS/rail-clamp arrays shunt surge currents.", "interaction": "Safeguards Ethernet, CAN, LIN and sensor lines.", "category": "onsemi", "connection": [] }, { "name": "Ethernet Controllers", "function": "Industrial Ethernet connectivity (PHY/MAC).", "theory_of_operation": "Implements 10/100/1000BASE-T physical layer with MII/RMII/RGMII.", "interaction": "Connects MCU to field networks and higher-level controllers.", "category": "onsemi", "connection": [] }, { "name": "CAN", "function": "Robust multi-drop differential communication for control networks.", "theory_of_operation": "CAN/CAN-FD transceivers with dominant/recessive arbitration and fault protection.", "interaction": "Links the drive to factory/vehicle control networks.", "category": "onsemi", "connection": [] }, { "name": "LIN", "function": "Low-cost single-wire communication for auxiliary modules.", "theory_of_operation": "UART-based master/slave protocol over a single-wire bus.", "interaction": "Provides simple peripheral communication channels.", "category": "onsemi", "connection": [] }, { "name": "Amplifier & Comparator", "function": "Analog signal conditioning and threshold detection for sensors.", "theory_of_operation": "Precision op-amps and comparators with selectable gain and hysteresis.", "interaction": "Interfaces Inductive Sensor and protection thresholds to the MCU.", "category": "onsemi", "connection": [] } ] } ], "interconnections": [ {"source": "Three Phase AC IN", "target": "EMC Filter"}, {"source": "EMC Filter", "target": "AC/DC Converter"}, {"source": "EMC Filter", "target": "Sensing & Isolation"}, {"source": "EMC Filter", "target": "Auxiliary Power Supply"}, {"source": "AC/DC Converter", "target": "DC/DC Converter"}, {"source": "AC/DC Converter", "target": "Sensing & Isolation"}, {"source": "DC/DC Converter", "target": "Inverter Stage & Brake"}, {"source": "DC/DC Converter", "target": "Sensing & Isolation"}, {"source": "Inverter Stage & Brake", "target": "Three Phase Motor"}, {"source": "Inverter Stage & Brake", "target": "Sensing & Isolation"}, {"source": "Three Phase Motor", "target": "Inductive Sensor"}, {"source": "Gate Driver", "target": "AC/DC Converter"}, {"source": "Gate Driver", "target": "DC/DC Converter"}, {"source": "Gate Driver", "target": "Inverter Stage & Brake"}, {"source": "MCU", "target": "Gate Driver"}, {"source": "Sensing & Isolation", "target": "MCU"}, {"source": "Auxiliary Power Supply", "target": "MCU"}, {"source": "Auxiliary Power Supply", "target": "Gate Driver"}, {"source": "Auxiliary Power Supply", "target": "Sensing & Isolation"}, {"source": "Auxiliary Power Supply", "target": "MCU Interface"}, {"source": "MCU", "target": "MCU Interface"}, {"source": "Inductive Sensor", "target": "MCU"}, {"source": "MCU Interface", "target": "MCU"} ], "Last_update": "2025-10-28",
1. What applications commonly use three‑phase motor drives?
Three‑phase motor drives are widely used in industrial pumps, fans, compressors, conveyors, and machine tools. The diagram reflects these applications by combining high‑power stages, control logic, and protection functions suitable for continuous operation and demanding industrial loads.
2. How does power conversion work in a three‑phase motor drive?
Power conversion works by rectifying the AC input, storing energy in a DC link, and generating controlled three‑phase outputs using an inverter. The block diagram highlights these stages to show how electrical energy is efficiently converted into controlled motor drive signals.
3. What role do gate drivers play in a three‑phase motor drive?
Gate drivers provide the correct voltage and timing signals to switch power transistors in the inverter stage. In the block diagram, gate drivers act as the interface between the controller and power devices, ensuring safe, efficient, and reliable switching behavior.
4. How are current and voltage sensing implemented in the system?
Current and voltage sensing provide real‑time feedback on motor and inverter operation. The diagram includes sensing blocks that feed data to the controller, enabling precise control, efficiency optimization, and detection of abnormal operating conditions such as overloads or faults.
5. How does the onsemi Interactive Block Diagram help me select parts and build a worksheet/BOM?
The onsemi interactive block diagram lets you select a taxonomy, choose devices per block, and download a worksheet. If you need a deeper dive into the tool, watch our tutorial video.
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