Whether it's a hot summer or a cold winter, passengers can always enjoy a comfortable interior environment with the car's heating and cooling system. These HVAC systems vary in complexity and automation in different categories of vehicles. Economy cars may require the driver to manually turn the knob to control the temperature, while in high-end vehicles, the temperature inside the car and the humidity and quality of the air can be automatically controlled by the sensor.
air flow
Regardless of the type of vehicle, the automotive HVAC system exchanges air and changes its temperature, humidity and quality during this process.
Let's take a look at the principle of air flow. Air can be drawn into the system from the outside or inside of the cabin. It can also be adjusted by entering the HVAC system through an evaporator or heat exchanger; the air is distributed throughout the cabin to keep the passenger's feet warm and prevent the windshield from fogging.
There are many ways to move air: from the outside to the evaporator to the windshield, or from the inside to the heat exchanger to the vents at the bottom of the car. So how does the HVAC system control the flow of air?
Figure 1 is a side view of an HVAC system. The key components are numbered and the arrows indicate the direction of air flow. Parts 4 through 8 in Figure 1 are shown as damper actuators. The orange dotted line indicates the area where the damper moves, and the orange solid line represents the damper. The number of damper actuators in an HVAC system depends on the overall complexity of the system - whether it is a single zone or a multi-zone HVAC.
Figure 1: Car HVAC consisting of eight components: 1 = blower, 2 = evaporator, 3 = heater, 4 = intake damper, 5, 6 and 7 = air distribution damper, 8 = air mixing damper
Damper actuator
Air flows through the pipe in the HVAC system; the damper controls the flow of air by opening or closing sections of the pipe in whole or in part. A damper actuator (also known as a damper) is an electrical device that moves the damper.
There are three types of damper actuators in automotive HVAC systems:
Intake damper actuator (component 4 in Figure 1): This damper actuator controls the regulation of the air source - the outside air or the recirculated air inside the vehicle. The damper actuator position can be controlled by the driver using a recirculation button or by the HVAC system based on data from the inboard air quality sensor.
Air Mixing Damper Actuator (Part 8 in Figure 1): This damper actuator mixes the heating (heat exchanger) and the cold air (evaporator) to achieve the set air temperature.
Air distribution damper actuators (components 5, 6 and 7 in Figure 1): The number of damper actuators varies depending on the type of vehicle used to distribute the air within the cabin.
DC
Which electrical equipment is responsible for driving the damper? Just as there are many ways to control air flow, car manufacturers have many options for electrical equipment that drives the damper. A brushed DC motor with a potentiometer is used to sense the position of the damper; a three-phase brushless DC (BLDC) motor that uses a back electromotive force (back EMF) to measure the position or a stepper motor that measures the position by calculating the number of steps. These DC motors drive the damper through gears of different sizes.
More choices
Once the motor is selected, HVAC system engineers can also choose the architecture that drives the motor. As mentioned earlier, the damper actuator can be controlled locally or remotely. In local control, the electronics that control the motor are located near the motor, ie the motor control IC is integrated in the same housing as the motor (see damper actuator control in Figure 2). A communication protocol, such as a Local Interconnect Network (LIN), controls the motor to drive the damper to a specific location. In remote control, the electronics that control the motor are located in the HVAC control unit (see Figure 3) away from the damper actuator. Communication between the motor driver and the microcontroller on the HVAC control unit can be achieved via the Serial Peripheral Interface (SPI) or even via a parallel digital control interface.
Figures 2 and 3 illustrate two possible architectures. The architecture in Figure 2 is more complex than the architecture in Figure 3; however, the architecture in Figure 2 provides greater design scalability and flexibility.
Figure 2: Remote control of the damper actuator motor
Figure 3: Integrated motor drive for the damper actuator
More choices
Let's take a look at the connection between the microcontroller and the motor driver control IC. HVAC system designers also have a variety of options for this connection. The microcontroller can be connected to the motor driver using a digital communication interface such as SPI, or it can be directly connected to the motor driver using a control line. Figures 4 and 5 illustrate these options.
PCB circuit boards are widely used in automotive electronics, including power control systems, safety control systems, body electronics systems, and communications.
In the future, automotive electronics will move toward the trend of big functions, namely: mobile communications, multimedia leisure, safe driving assistance (including automatic driving), ride comfort, energy saving (including electric vehicles), protection and preservation, all of which pose challenges to the PCB industry. At the same time, it also provides good development opportunities. For example, autonomous driving will bring large-scale applications of millimeter-wave radar, so the demand for high-frequency PCB boards for radars will be significantly increased, and the value is significantly higher than traditional PCB boards; BMS in electric vehicles is one of the core components. PCB board is one of the basic components of BMS and will benefit from the development of electric vehicles.
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