What is HVAC motor controller？
The HVAC motor controller efficiently controls heating and ventilation and interfaces with the vehicle’s VECU to adjust the speed of the HVAC blower motor. There are two connections in the controller, one to the load through the harness and another to the VECU. The signal from the VECU controls the motor speed and creates a soft start that will suppress any inrush during the motor’s start up.
The HVAC motor controller operates at 12 or 24V and drives DC motors up to 30A. It provides over-voltage protection, up to 100V for two minutes, meeting automotive requirements for EMC, vibration and shock. These features help extend the life of the HVAC unit and prevent the nuisance blowing of fuses or circuit breakers. The HVAC controller is sealed to IP68, to protect it from the extreme environmental conditions subject to the blower housing. The HVAC motor controller is compact and uses fewer components and connections than traditional motor control devices.
HVAC motor controller is devided to 2 types, the one is AC input HVAC motor control, the other is DC input HVAC motor control. Let's talk about AC input HVAC motor control first.
AC Motor Control Basics
An AC motor controller is known as the device that controls the speed of the AC motor. An AC controller can also be referred to as a variable frequency drive, adjustable speed drive, frequency converter and more. The AC motor receives power, which is converted by the AC motor controller into an adjustable frequency. This adjustable output allows the motor speed to be precisely controlled.
Typically, an AC motor controller consists of three basic parts: the rectifier, inverter, and the DC link to connect the rectifier and inverter. The rectifier converts AC input into DC (direct current), while the inverter switches the DC voltage to an adjustable frequency AC output voltage. The inverter can also be used to control output current flow if needed. Both the rectifier and inverter are directed by a set of controls to generate a specific amount of AC voltage and frequency to match the AC motor system at any given point in time.
As shown below, AC input HVAC motor control has 18 structures, each part namely Input rectifier & filter、PFC stage、Non-isolated DC/DC power supply、Digital IO interface、Diagnostics/monitoring、DC-link current & voltage sense、Point of load power supply、Analog IO interface、Fieldbus/configuration interface、Output user interface、Input user interface、Application controller、Isolation、Motor controller、Wireless interface、3-phase power stage、Temperature monitoring、Motor current & voltage sense, each part has it's own products, let's see what are they.
Input rectifier & filter
EMI filter, AC rectification and protection for mains power supply includes inrush current control. Input rectifier & filter include Low-side switches, it's corresponding product is ULN2003A.
PFC stage
The power factor correction (PFC) stage contains the PFC controllers which offer the highest efficiency, lowest standby power, superior power factor, and current distortion for the switched-mode power supplies (SMPS). Our portfolio covers everything from conduction mode/transition (CRM/TM) mode to continuous conduction mode (CCM) PFC. PFC stage includes Low-side drivers and Power factor correction (PFC) controllers, the corresponding products are UCC27517、UCC28070
Non-isolated DC/DC power supply
Non-isolated DC/DC power supply is used to generate the voltage rail to power gate drivers. Form factor, efficiency and good regulation are the key design considerations. Non-isolated DC/DC power supply includes Flyback controllers、Series voltage references and Isolated DC/DC converters & modules, the corresponding products are UCC28711、REF35、LM25180
Digital IO interface
Digital IO interfaces are designed to communicate with external system controller. Digital IO interface includes Noninverting buffers & drivers、Inverting buffers & drivers、Comparators、Multi-switch detection interface (MSDI) ICs and N-channel MOSFETs, the corresponding products are CD74HCT541、SN74LVC1G17、SN74LV04A、TLV9031、SN65HVS885、CSD18537NQ5A
Diagnostics/monitoring
The safe torque off function removes torque producing component from the inverter, thereby stopping the motor. Multiple redundant paths might be implemented to realize safe torque off in drives to achieve the required safety levels. Diagnostics/monitoring includes AND gates, it's corresponding product is SN74AUP1G08-Q1
DC-link current & voltage sense
DC-link current is measured to protect the inverter against over current and ground faults. DC bus voltage is measured to detect overvoltage, under voltage and control the inverter. Proper selection of op amp is critical to precisely measure the DC-link current and voltage. DC-link current & voltage sense includes General-purpose op amps、Comparators、Analog current-sense amplifiers、Precision op amps (Vos<1mV)、Difference amplifiers、Shunt voltage references and Series voltage references, the corresponding products are OPA323、LM393LV、INA303、OPA2192、INA149、ATL431LI、REF2025
Point of load power supply
Point of load power supply is used to generate the regulated voltage rails to power op amps, MCU and other circuits. Form factor, efficiency and good regulation are the key design considerations. Point of load power supply includes Buck converters (integrated switch)、Linear & low-dropout (LDO) regulators、Buck modules (integrated inductor) and Series voltage references, the corresponding products are TPS562203、TPS7A24、TLVM23615、REF35
Analog IO interface
Analog inputs are used to communicate speed/position/torque control reference setpoints from the HVAC system controller to the motor control unit. Analog outputs are used to monitor and feedback key drive parameters back to the HVAC system controller. Analog IOs can be +/-10V, 0-10V signals or 4-20mA current signals. Analog IO interface includes General-purpose op amps、Comparators、4-20mA signal conditioners、Precision op amps (Vos<1mV)、Instrumentation amplifiers、TVS diodes、Shunt voltage references、Series voltage references、Precision DACs (≤10 MSPS) and Precision ADCs, the corresponding products are OPA323、LM393B、XTR300、OPA320、INA188、TVS1400、TLV431A、REF35、DAC7760
Fieldbus/configuration interface
Wired signal interfaces like RS-485, CAN or interface translators are important for deterministic, secure and reliable communication between motor and HVAC system controllers. Signal interfaces need to support fieldbus solutions like Profibus, Modbus or vendor specific protocols. Fieldbus/configuration interface includes Isolated CAN transceivers、Isolated RS-485 transceivers、RS-485 & RS-422 transceivers, the corresponding products are ISO1042、ISO3082、THVD1500
Output user interface
The output user interface may consist of a simple LED to indicate system status. An LED driver is an option for flashing a single color LED. Output user interface includes Noninverting buffers & driver and Inverting buffers & drivers, the corresponding products are CD74HCT541、SN74AHC541、SN74LVC1G14
Input user interface
Input user interfaces include keypads, touch sensitive screens and rotary dials. This sub-system receives the real-world inputs and translates the inputs into signal forms that can be interpreted by digital processing. Input user interface includes Noninverting buffers & drivers, it's corresponding products are SN74AHC125、SN74AHC541
Application controller
The application controller block communicates with external systems. It communicates with the motor controller MCU with isolated SPI bus. Application controller includes C2000 real-time microcontrollers, it's corresponding product is TMS320F2800133
Isolation
Isolated SPI bus is used to communicate between the motor control and the appication MCU. Isolation includes Digital isolators, it's corresponding product is ISO7741
Motor controller
The motor controller block receives current, voltage, temperature feedback signals and implements torque control algorithm, monitors for fault conditions, generates gate signals to drive the power devices, stores critical information like fault parameters amongst other functions. This block can be implemented as one MCU or with multiple MCU with cross functional validation. Motor controller includes C2000 real-time microcontrollers、Arm Cortex-M0+ MCUs、MSP430 microcontrollers、Noninverting buffers & drivers、Inverting buffers & drivers, the corresponding products are TMS320F2800133、MSPM0G1506、MSP430F5132、SN74AHC125、SN74LVC1G14
Wireless interface
The wireless interface allows the user to access and control the motor from a remote location. A system-on-chip solution which integrates a microcontroller and radio allows designs to run the application layer and wireless protocol stack on one chip. A microcontroller with dedicated RF radio topology allows designs to separate the wireless protocol stack from the application layer. A range extender can be used if additional range is required or will be used in an area that can expect a weak radio signal. Wireless interface includes Wi-Fi products and Arm Cortex-M0+ MCUs, the corresponding products are WL1801MOD、MSPM0G1506
3-phase power stage
3-phase power stage converts the DC-link voltage to variable voltage and variable frequency ac output. It is usually built with power devices like MOSFETs. Appropriate selection of gate drivers impacts power stage efficiency, overcurrent protection, safety and EMI. 3-phase power stage includes Isolated gate drivers、Low-side drivers、Half-bridge drivers、Isolated DC/DC converters & modules、Noninverting buffers & drivers、Inverting buffers & drivers, the corresponding products are UCC21750、UCC27531、UCC27712、CD74HCT541、SN74LV04A
Temperature monitoring
Temperature sensor together with signal conditioning circuit is used to measure the power device temperature. This information is used to limit the output power of the inverter to avoid thermal runaway. Temperature monitoring includes General-purpose op amps、Comparators、Analog temperature sensors, the corresponding products are OPA323、TLV9001、TLV3201、TMP235
Motor current & voltage sense
Motor current and voltages are sensed to implement the motor control algorithms as well as protect the inverter against over current conditions. Proper selection of op amp is critical to obtain wide speed ratio and to reduce torque ripple. Motor current & voltage sense includes General-purpose op amps、Comparators、High-speed op amps (GBW ≥ 50 MHz)、Precision op amps (Vos<1mV)、Instrumentation amplifiers、Precision ADCs、Shunt voltage references、Series voltage references, the corresponding products are TLV9152、LM393LV、OPA835、OPA2192、ADS131E08S、ATL431LI、REF3425
Hope our reference designs and integrated circuits can help you create HVAC motor control designs to meet standard energy conservation requirements.
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