In the car, the pumps, oil pumps and power steering pumps are still directly driven by the engine. These loads are driven by the motor, which greatly simplifies the mechanical design, eliminating the need for belts and wheels, while saving space in the engine compartment. The AUIR3330S provides a solution for driving any type of motor at full speed, with active di/dt control for EMI and switching loss performance optimization.
Motor adoption
We need to go back many years to review the period when the vehicle did not use the motor. At that time, the vehicle was started by a crank crank, and the engine cooling fan and wiper were mechanically coupled to the engine. The combination of the electric motor and the internal combustion engine was quickly combined, and this combination was originally mainly for comfort considerations. These motors are low-power motors (100W) and usually require only a simple relay to drive the load, which is the best choice for improving system efficiency and performance. As motors begin to be put into safety applications, such as anti-lock braking systems and traction control systems, motors require a more reliable drive system.
Recently, however, the automotive industry has turned its attention to reducing fuel consumption. The pressure of green traffic has forced engineers to find smart, effective solutions for their vehicles. The motor can achieve excellent performance when driven by intelligent electronic devices. The electronic solution is especially suitable for high power motors ("100W"). Although engine cooling and blowers in modern cars now use electronic power control, the range of applications for motors is still wide. Many of the functions in the car still use mechanical systems that are connected to the internal combustion engine. Electronic control can bring significant improvements in efficiency, and pumps and pumps are good examples. With electrical control, power can be efficiently transmitted to the motor, enabling the motor to accurately meet power requirements at all times.
Frequency conversion technology brings significant opportunities to the automotive industry
Vehicle engine cooling and blower application variable frequency motor control is the latest innovation. Both the engine cooling unit and the blower of the old model use a speed control system consisting of a resistor and a relay. With this system, the speed of the motor is limited to several discrete values. A resistor is required in series with the motor to achieve any speed value. The speed of the motor cannot be optimized for power requirements, so the performance of this solution is extremely low. This results in typical efficiencies below 50% in most cases.
Recent advances in power electronics technology have made variable frequency motor control the solution of choice for many applications. With variable frequency control, typical system efficiencies greater than 90% can be achieved over the entire load range. Taking a typical 400W engine cooling fan as an example, the power consumption of the electronic controller is 100W less than that of the resistance fan controller during a typical load cycle. The 100W power saved is equivalent to a reduction of about 0.1L per 100km of fuel consumption.
The challenge of driving motors with PWM control technology is to meet EMI requirements. At 20 kHz, the system produces noise on the battery side. The current slope di/dt during turn-on and turn-off is the primary source of EMI. In order to comply with EMI requirements, a passive filter must be connected between the battery and the inverter. This filter usually consists of two large capacitors and one inductor. The cost of the filter is an important cost for the entire system. In a simple system using MOSFETs, the only way to reduce di/dt is to insert a resistor at the gate to slow down the switching speed. Doing so will greatly increase switching losses, reduce system efficiency, and increase the size of the heat sink. In such systems, the size of the EMI filter and heat sink needs to be weighed.
The AUIR3330S uses proprietary di/dt control for the output to reduce the conducted emissions of the panel. This active di/dt control optimizes EMI and switching loss performance and is no longer subject to the trade-offs of EMI filters and heat sinks. The implementation of this feature requires the formation of a specific gate in the MOSFET, which is not possible with discrete components. For general applications with MOSFETs with drivers, switching time control is achieved by using a gate resistor to control the drive current. In addition, the AUIR3330S offers a solution for driving any type of motor at full speed. High integration allows designers to design a compact solution. Full speed range design can be achieved quickly with a minimum of external components.
Active di/dt control
During the turn-on process, the driver applies a large current to reach the MOSFET threshold as quickly as possible. As current begins to flow into the MOSFET, the gate current decreases to limit di/dt. When the drain-source voltage begins to drop, the gate current rises to limit switching losses. The switching losses are the same in the di/dt phase compared to resistor-driven MOSFETs, but the switching losses are much lower during the dv/dt phase. Therefore, at the same EMI level, the AUIR3330S consumes much less power and requires only a smaller heat sink. Active di/dt control requires a complex driver that can use different gate currents at different stages of the switch. The AUIR3330S also includes intelligent circuitry for detecting the di/dt and dv/dt phases.
Modern motor drive applications also require additional features such as protection and troubleshooting. The AUIR3330S integrates a variety of features to prevent system failure in abnormal mode, including over temperature conditions, output shorts, ground or bootstrap capacitor disconnection. In any of the above fault conditions, the AUIR3330S is protected and the fault diagnosis results are reported to the microprocessor. The diagnostic result is a value that can be read directly by the microprocessor.
In addition, the AUIR3330S has a current feedback function that reads the load current by measuring the voltage flowing through the Rifb resistor. The system monitors the load current to control the power supplied to the load. And the motor stall state can be detected.
Current sense feedback is used to set the overcurrent protection threshold. When the voltage across the Rifb resistor exceeds 4.5V, the output is automatically turned off. This feature prevents any faults in the line or motor during stalled conditions and can be adapted to the needs of each system.
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