Thursday, June 13, 2024

Reference Design For HVAC Compressor

The three-phase inverter drive innovates automotive A/C systems with efficient control for brushless DC motors.

compressor

Hybrid electric vehicles (HEVs) feature a key system known as idle-stop or stop-start. This system turns off the engine when the car is idling, such as at a traffic light. However, this engine shutdown means no power to operate the A/C compressor. To address this, most hybrids and all-electric vehicles (EVs) incorporate an electrically driven compressor. This compressor integrates an electric motor powered by the vehicle’s high-voltage battery through an inverter. The inverter’s IGBTs handle high currents, leading to the widespread use of isolated components like gate drivers and analog-to-digital converters (ADCs). These components, while essential, introduce delays in the switching circuit and increase the overall cost. Additionally, the price is affected by the need for rotation detection in the motor. Designers often achieve this through the implementation of a resolver or by using a pair of Hall sensors, each contributing to the system’s complexity and expense.

The TIDA-01418 from Texas Instruments (TI) represents a three-phase inverter drive designed for automotive A/C compressors. It utilizes discrete IGBTs to power brushless DC (BLDC) motors and operates on a sensorless torque control mechanism. This setup is tailored explicitly for driving BLDC motors in automotive air conditioning systems.

The solution for operating an automotive HVAC A/C compressor using a BLDC motor is employing the UCC27712-Q1 high- and low-side gate driver and discrete insulated-gate bipolar transistor (IGBT) half bridges. This system’s core is Texas Instruments’ C2000 Piccolo F2805x microcontroller, coupled with the InstaSPIN-FOC sensorless motor control solution. This innovative approach facilitates motor parameter identification and automatic tuning of the current loop, enabling high-performance sensorless functionality. 

Key features of the design include starting under heavy loads and precise control at very low speeds. InstaSPIN technology significantly enhances the dynamic range of the compressor, allowing it to operate at lower speeds (down to 500 rpm) while maintaining full torque, leading to electric vehicle battery savings during HVAC operation. Designers can access InstaSPIN through special libraries in the Piccolo microcontrollers’ read-only memory (ROM) (MCUs). This provides a robust toolkit for developers working on sensorless motor control applications, focusing on velocity and torque.

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This design boasts a range of features tailored for automotive applications. It can handle low-voltage conditions, surviving up to 45 V, and is robust enough to withstand reverse battery and load dump scenarios in 12-V systems. The design includes safeguards such as an active Miller clamp and an overcurrent detecting circuit to protect against overcurrent and false turn-on events. It also features an isolated CAN-communication interface, ensuring secure and reliable data transmission. The gate drivers are non-isolated, cost-effective, and capable of delivering a 2.5-A peak output. An isolated power supply is integrated into the design, enhancing its safety and efficiency. The compact layout of the components is meticulously planned, with each component selected to meet automotive temperature and quality standards. 

TI has tested this reference design. It comes with a Bill of Material (BOM), schematics, etc. You can find additional data about the reference design on the company’s website. To read more about this reference design, click here.

Nidhi Agarwal
Nidhi Agarwal
Nidhi Agarwal is a journalist at EFY. She is an Electronics and Communication Engineer with over five years of academic experience. Her expertise lies in working with development boards and IoT cloud. She enjoys writing as it enables her to share her knowledge and insights related to electronics, with like-minded techies.

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