Air conditioning is an indispensable configuration to meet the comfort requirements of the car. It is used for interior cooling, heating, ventilation, and a comfortable driving environment is also related to driving safety. The automatic air conditioner is more convenient than the traditional manual air conditioner, and can automatically detect and adjust according to the temperature set by the user, so that the temperature and humidity in the vehicle are within the set range. Moreover, automatic air conditioning also helps to save energy and reduce fuel economy.
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Typical power supply structure for automotive air conditioners
In general, automotive voltage is divided into 24 V system and 12 V system: 24 V power supply can be powered by high-power TVS (transient voltage suppressor), then by low-dropout regulator (LDO) to 5 V, while Powering the motor driver; it can also be reduced to 12 V with a higher cost DC-DC buck, then from LDO to 5 V, while powering the motor driver; 12 V power supply to the microcontroller, sensor, etc. via the LDO At the same time, it directly supplies power to motor drivers such as DC/stepper motors.
Figure 1. Typical power supply structure for automotive air conditioning
If you use a 24 V power supply system, you need to consider high-voltage products, while taking into account thermal management, power efficiency and cost control; if you use a 12 V power supply system, you need to consider factors such as cost, quiescent current (Iq) and packaging.
ON Semiconductor offers a rich lineup of LDOs for automotive air conditioning systems, including standard static power series (Iq > 100 uA) such as NCV4264-2, NCV4266-2, and low static power series (Iq < 100 uA) such as NCV8501 and NCV8502. Very low static power series (Iq < 50 uA) such as NCV8664, NCV8660, ultra low static power series (Iq < 33 uA) such as NCV8768, NCV8769, to meet the different needs of the design.
ON Semiconductor also offers the voltage follower NCV8184, which provides an adjustable buffered output voltage that closely matches the reference input voltage (accuracy of ±3 mV). The device has an output current capability of 70 mA, a quiescent current of only 70 uA, and a typical voltage drop of only 0.35 V at 50 mA, in a SOIC-8 package.
drive
1. damper actuator drive
DC motors, unipolar stepper motors, and bipolar stepper motors are three typical structures for automotive air-conditioning damper actuators. The DC motor damper actuator includes a DC motor and a position sensor. A complete H-bridge (composed of 2 high-side switches and 2 low-side switches) is required to control the forward and reverse rotation of the motor. The position sensor can monitor the position of the damper in real time to realize closed-loop control. The control of the unipolar stepping motor only needs 4 high sides or 4 low side drives. Due to the characteristics of the stepping motor itself, the number of steps can be counted. To know the position of the damper; the bipolar stepper motor only needs two sets of coils, and its drive requires two H-bridges (composed of four high-side switches and four low-side switches) to control the two coils, and unipolar The stepper motor is similar, and the current position of the damper can be known by counting the number of steps.
Figure 2. Damper actuator motor structure and drive type
The DC motor damper actuator has a normal operating current of approximately 100 mA and a stall current of less than 450 mA. An H-bridge drive is required to change the direction of operation and provide a fault diagnosis report and adequate protection. ON Semiconductor's NCV77XX series fully meets these requirements and can operate in forward, reverse, braking and high impedance states. Taking the six-way half-bridge driver NCV7718 as an example, six PMOSs are used as high-side drivers, six NMOSs are used as low-side drivers, high and low sides are connected inside the chip, and H half-bridges are used as outputs to provide 0.55 A continuous drive current, and internal freewheeling is integrated. Diode, on-resistance typical and maximum values ​​are 1 Ω and 2.25 Ω, controlled by a 16-bit SPI interface, low power consumption (maximum current consumption is only 5 Ua), providing drive state, low load protection, overcurrent, over Diagnostic reports such as mild temperature warnings and integration of a range of protection features such as overvoltage/undervoltage protection, overcurrent shutdown, overtemperature protection, etc., in SSOP-24 / SSOP24-EP package. In addition, depending on the output requirements, you can choose ON Semiconductor's 8-way half-bridge driver NCV7719 or 10-way half-bridge driver NCV7720. ON Semiconductor also offers a six-way half-bridge driver NCV7728 with independent diagnostics. The device has a peak current of 0.55 A. The typical and maximum on-resistance are 1 Ω and 2 Ω, respectively. The interface is compatible with 3.3 V/5 V microcontrollers. Ultra-low static power consumption in sleep mode, controlled by 16-bit SPI interface (baud rate 5 MHz, compatible with daisy-chain communication), integrated freewheeling protection, overcurrent protection, open circuit detection, thermal shutdown and overtemperature alarm Protection features.
Figure 3. Typical application example for a 6-way half-bridge driver NCV7728 with independent diagnostics
In the stepper motor damper actuator, each motor needs 4 drives, the maximum operating current is less than 300 mA, and can be directly controlled or remotely controlled via the LIN bus. ON Semiconductor's unipolar stepper motor drivers for automotive air conditioners are the NCV7608 and NCV7240. The NCV7608 is an 8-channel high- and low-side configurable driver that delivers 350 mA of drive current per channel. It provides comprehensive protection in a SOIC28 package and is AEC-Q101 certified. The NCV7420 is an 8-channel low-side driver that provides 600 mA per channel. The current, controlled by a 16-bit SPI interface, provides complete diagnostic and protection functions such as open circuit diagnostics, overload protection, and overtemperature protection. It is packaged in SSOP24 and certified to AEC-Q100. ON Semiconductor's bipolar stepper motor drivers for automotive air conditioners include the AMIS30730 and NCV70501, both of which have a drive current of 300 mA. The AMIS30730 uses a LIN interface with MCU, ROM, RAM and EEPROM; the NCV70501 uses an SPI interface.
2. High/low side drive
SmartFETs are used for control of external loads (such as relays in central electrical boxes) and can be used as high-side or low-side drives that require additional protection features such as short-circuit protection, thermal shutdown, overvoltage protection, and logic Flat control and ESD protection. ON Semiconductor's NCV8452 is a high-side SmartFET with an on-resistance of 200 mΩ, an overvoltage protection rating of 41 V, and an output current limit of 1 A. It integrates a wide range of protection features such as short-circuit protection and overload. Protection, over temperature shutdown and automatic restart, internal clamp diode overvoltage protection, ESD protection and logic level control, etc., junction temperature -40 ~ 150 °C. ON Semiconductor's high-/low-side smart drive devices include NCV8440, NCV8450, and NCV8401/2/3/5/6, which provide different clamping voltages, on-resistance, and output current parameters.
3. Blower drive
Blowers fall into two broad categories: brushed DC motors and brushless DC motors (BLDC). Brushed DC motors have a maximum operating current of 30 A and are PWM controlled with power MOSFETs. BLDC motors require pre-drivers and power MOSFETs. ON Semiconductor offers N-channel power MOSFETs for brushed DC motors and BLDC drives as shown in Table 1, as well as three-phase pre-drivers for BLDC motors such as the LV8907UW and MC33033/5. To help engineers simplify design and save space, ON Semiconductor also offers the STK984-xxx series of intelligent power modules with integrated pre-drivers and power MOSFETs, an integrated motor-driven algorithm, six MOSFETs and driver circuits, via PWM or voltage regulation. The OTP register is provided for motor parameter configuration, modularization for PCB-free design, and integrated protection features such as overcurrent protection, overtemperature protection, and overvoltage/undervoltage protection.
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