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.
What are DC motor controllers?
Simply put, a DC motor controller is any device that can manipulate the position, speed, or torque of a DC-powered motor. There are controllers for brushed DC motors, brushless DC motors, as well as universal motors, and they all allow operators to set desired motor behavior even though their mechanisms for doing so differ.
To briefly summarize, the speed/torque curve of DC motors are inversely linear, meaning their torque proportionally decreases as the motor RPMs increase. This allows for easy control, as lowering the speed will increase the torque, and vice versa. Also, unlike some AC motors, DC motors are easily reversed by simply switching their leads so that the DC current runs in the opposite direction. DC motor controllers exploit these characteristics in unique ways, and this article will explore the most popular methods.
As shown below, DC input HVAC motor control has 14 structures, each part namely Input power protectionNon-isolated DC/DC power supply、Digital IO interface、Analog IO interface、Fieldbus/configuration interface、Output user interface、Input user interface、Digital processing、Wireless interface、3-phase power stage、Current & voltage sense、Hall sensor interface、Self-diagnostics/monitoring、Position sensing, each part has it's own products, let's see what are they.
Input power protection
The input section of the power supply needs to be protected against over-voltage and reverse polarity due to mis-wiring. Further, the current drawn at the input needs to be limited during power up as well as steady state condition. Input power protection includes eFuses & hot swap controllers and N-channel MOSFETs, the corresponding producta are TPS25921A、CSD18563Q5A.
Non-isolated DC/DC power supply
Non-Isolated DC/DC power supply is used to generate the regulated voltage rails to power OPAMPS, MCU and other circuits. Form factor, efficiency and good regulation are the key design considerations. Non-isolated DC/DC power supply includes Buck converters (integrated switch)、Linear & low-dropout (LDO) regulators、Buck controllers (external switch)、Series voltage references、N-channel MOSFETs、Buck modules (integrated inductor)、Load switches, the corresponding products are TPS560200、TLV703、LM5145、REF4132、CSD17318Q2、TPSM63602、TPS22918
Digital IO interface
Digital input and output interfaces are often isolated to avoid ground loops and require an isolated DC/DC converter to supply an isolated rail for the isolated I/Os. Digital IO interface includes Inverting buffers & drivers、Noninverting buffers & drivers、Comparators、General-purpose op amps、ESD protection diodes、TVS diodes, the corresponding products are SN74LVC3G14、SN74LVC3G17、TLV1701、TLV9154、TPD2E2U06、TVS1401
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、Precision op amps (Vos<1mV)、Analog current-sense amplifiers、4-20mA signal conditioners、Analog switches & muxes、ESD protection diodes、TVS diodes、Shunt voltage references、Series voltage references、Precision ADCs and Precision DACs (≤10 MSPS), the corresponding products are TLV9154、TLV1702、LMP7709、INA199、XTR300、SN74CBTLV3257、TPD2E2U06、TVS1401、LM4041D、REF4132、ADS131E08、DAC8760
Fieldbus/configuration interface
Wired signal interfaces like USB, RS485, RS-232 are important for deterministic, secure and robust communication between motor and external user device. Industrial drives need to support multi-protocol solutions and need to meet the IEC61800-3 EMC immunity requirements for robust communication in harsh industrial environments. Fieldbus/configuration interface includes Isolated RS-485 transceivers、Isolated CAN transceivers、RS-485 & RS-422 transceivers、ESD protection diodes、TVS diodes、RS-232 transceivers, the corresponding products are ISO3082、ISO1050、SN65HVD3085E、TPD1E10B06、TVS1401、TRS3232E
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 & drivers、Shift registers、Inverting buffers & drivers, the corresponding products are SN74LVC1G17、SN74HC595、SN74AHC1G14
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、Shift registers, the corresponding products are SN74AHC541、SN74HC595
Digital processing
The digital processing block receives current, voltage, temperature feedback signals and implements torque control algorithm, monitors for fault conditions, communicates with external systems, generates gate signals to drive the power devices, stores critical information like fault parameters among other functions. This block can be implemented as one MCU or with multiple MCU with cross functional validation.Digital processing includes C2000 real-time microcontrollers、MSP430 microcontrollers、Arm Cortex-M4 MCUs、Inverting buffers & drivers、Noninverting buffers & drivers, the corresponding products are TMS320F28027F、MSP430F5528、TM4C123GH6PM、SN74AHC1G14、SN74LVC3G17
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、Low-power 2.4-GHz products、Sub-1 GHz wireless MCUs, the corresponding products are CC3100MOD、CC2652R、CC1350
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 N-channel MOSFETs、BLDC drivers、Inverting buffers & drivers、Noninverting buffers & driver, the corresponding products are CSD18543Q3A、DRV8308、SN74LVC3G14、SN74AHC541
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. Various current sensing techniques (shunt, magnetic) are used depending upon the accuracy, ease of implementation and current measurement range. Current & voltage sense includes General-purpose op amps、Comparators、High-speed op amps (GBW ≥ 50 MHz)、Precision op amps (Vos<1mV)、Analog current-sense amplifiers、Instrumentation amplifiers、Linear & low-dropout (LDO) regulators、Linear & low-dropout (LDO) regulators、Series voltage references、Precision ADCs, it's corresponding products are TLV9002、LM2903、OPA365、TLC2274A、INA138、INA188、TLV1117LV、TLV431B、REF4132、ADS8354
Hall sensor interface
For 'sensored' BLDC motor control, if hall sensors are used, appropriate level translations may be required. This block becomes optional for sensorless BLDC motor control algorithms. Hall sensor interface includes ESD protection diodes、TVS diodes、Load switches, the corresponding products are TPD1E10B06、TVS0500、TPS22860
Self-diagnostics/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. Self-diagnostics/monitoring includes General-purpose op amps、Comparators、Supervisor & reset ICs、Analog temperature sensors、Digital temperature sensors, the corresponding products are TLV9002、TLV1701、TPS3823、LMT87、LMT01
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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