Design of Control Power Supply for NEC Electronic Body Electronic System

As the demand for more functions and higher reliability continues to grow, the variety and complexity of automotive electronics are also rapidly increasing. There are many kinds of Electronic subsystems in automobiles, such as chassis electronics, driver information electronics, and body electronics. The body electronic subsystem provides functions such as seat adjustment, interior lighting and wipers. The intelligent design enables the body control module (BCM) to drive the load more effectively and reliably.

BCM is one of the most important modules in a car. BCM is used to control common “body” functions that do not require a dedicated controller, including window, mirror, door lock and lamp control, and RF receivers that receive information from car keys and tire pressure monitors. In addition, BCM also functions as a gateway to transmit data between different modules through the network bus. Because BCM connects multiple car buses, it is an ideal platform for adding new functions to cars. When automotive electronics design engineers want to add new features to the car, but do not have much time, space or budget to add new modules, they can often write new software for BCM and use its networking capabilities to achieve these features.

Obviously, the demand for BCM varies from car to car, but one application trend is to develop a single module that can cover multiple car models so that car manufacturers can reduce development and maintenance costs. Only need to carry on some configuration work to each kind of vehicle type, can deploy this module on multiple car platforms more quickly, thus shortening the overall time-to-market of the product.

The work of BCM can be roughly divided into two parts: the control part, including MCU, sensor input and the in-car network; the power part, including the power devices that can provide high-power signals to drive various loads. When designing the power supply part, it is necessary to understand the various load characteristics used in the body electronics. For example, LEDs are rapidly replacing incandescent lamps because of their low power consumption, excellent robustness and reliability. Electronic motors are also used to implement mechanical functions such as raising and lowering windows, changing seat positions, and adjusting mirrors. Resistive elements are used in seat heating and rear window defrosting applications.

Integrating control and power circuits into one module requires some challenges to be solved. When BCM designers start a new design, they must consider all possible device options for the control and power supply parts, and then, after considering all design factors, decide how to combine the two to best meet the needs. When a designer chooses a suitable device combination, the main design factors that must be considered are: power budget, heat dissipation, robustness, and cost. For example, the power supply part traditionally only uses power relays, but recent designs have shown signs of transition to solid-state solutions. Solid-state electronics can provide a more robust solution to reduce overall costs. In addition, by combining these solid-state devices with intelligent digital controllers, designers can achieve diagnostic and fault prevention protection functions that were impossible before. Ultimately, the designer’s goal is to produce a cost-effective BCM that can fully meet application needs and has high reliability to meet stringent automotive standards.

Figure 1 is a BCM principle block diagram based on NEC Electronics’ 32-bit MCU V850ES/Fx3, which shows the connection between the module and the sensor’s output and power supply. The advantage of using MCU is that the control problem can be divided into hardware peripherals and software algorithms to solve. Compared with the method of realizing control by hardware, this modular design method has more flexibility. In addition, the use of MCU can also perform diagnosis (even self-diagnosis) in the system, thereby making the system more robust.

  Design of Control Power Supply for NEC Electronic Body Electronic System

Figure 1: The block diagram of the body control module based on the 32-bit MCU V850ES/Fx3.

When implementing the control part of the body module, the most critical decision is to select an MCU with appropriate peripherals that can meet the application’s performance and cost budget requirements, such as NEC Electronics’ V850ES/Fx3 MCU. V850ES/Fx3 is based on the V850 32-bit CPU core and is optimized for automotive body applications. The V850 core is designed for embedded systems. It has real-time performance such as high-performance processing capabilities, fast interrupt response speed, and efficient data transmission capabilities. The core also includes a dedicated interrupt controller equipped with an independent vector for each interrupt source, which can quickly respond to various requests. The on-chip direct memory access (DMA) unit can access the memory and the system bus, and can transfer data without CPU intervention.

In particular, the V850ES/Fx3 MCU integrates a variety of advanced peripherals that are particularly required by body modules. For example, the timer is very important for car body applications. It is used to schedule tasks, capture external signals such as RF pulses, and more importantly, it can generate pulse width modulation (PWM) signals required to control LEDs in the car. The V850ES/Fx3 MCU can provide multiple programmable timer macros that can run in multiple modes. It can also synchronize each timer to increase the PWM capability. In order to meet the increasing needs of OEMs for the network, the MCU series integrates 5 controller area network (CAN) channels, each channel has an independent information buffer and a mask register that can filter information without CPU intervention. For low-speed local interconnect network (LIN) applications, the V850ES/Fx3 MCU supports 8 LIN channels and has a multi-LIN master (MLM) unit that uses hardware to process the LIN protocol, thereby saving CPU resources. The MCU has up to 40 analog-to-digital conversion channels to process analog signals. These channels have pin diagnostics, automatic discharge and flexible trigger resources.

  Design of Control Power Supply for NEC Electronic Body Electronic System

In addition to the demand for smart on-chip peripherals, an overwhelming trend in embedded automotive electronics is the use of flash memory. For example, the code flash space of V850ES/Fx3 MCU is from 6? kB to 1MB, it also has other on-chip memory that can be used as data memory to store high-endurance data.

One of the most demanding requirements for the MCU in body electronics applications is that the MCU must keep working when the car is not running. In this case, the MCU must support a standby mode to provide the necessary functions at an acceptable power consumption level. V850ES/Fx3 MCU has NEC Electronics’ MF2 embedded flash memory technology for low power consumption mode, which enables the MCU to run only necessary peripherals such as internal clock and periodic timers required by the system, which consumes power at this time Only 10 to 15uA, which can meet the most demanding power consumption requirements. Combining the beauty of high-density flash memory and low-leakage current logic, it can reduce power consumption while enabling the entire MCU to have an outstanding cost performance.

As the demand for more functions and higher reliability continues to grow, the variety and complexity of automotive electronics are also rapidly increasing. There are many kinds of electronic subsystems in automobiles, such as chassis electronics, driver information electronics, and body electronics. The body electronic subsystem provides functions such as seat adjustment, interior lighting and wipers. The intelligent design enables the body control module (BCM) to drive the load more effectively and reliably.

BCM is one of the most important modules in a car. BCM is used to control common “body” functions that do not require a dedicated controller, including window, mirror, door lock and lamp control, and RF receivers that receive information from car keys and tire pressure monitors. In addition, BCM also functions as a gateway to transmit data between different modules through the network bus. Because BCM connects multiple car buses, it is an ideal platform for adding new functions to cars. When automotive electronics design engineers want to add new features to the car, but do not have much time, space or budget to add new modules, they can often write new software for BCM and use its networking capabilities to achieve these features.

Obviously, the demand for BCM varies from car to car, but one application trend is to develop a single module that can cover multiple car models so that car manufacturers can reduce development and maintenance costs. Only need to carry on some configuration work to each kind of vehicle type, can deploy this module on multiple car platforms more quickly, thus shortening the overall time-to-market of the product.

The work of BCM can be roughly divided into two parts: the control part, including MCU, sensor input and the in-car network; the power part, including the power devices that can provide high-power signals to drive various loads. When designing the power supply part, it is necessary to understand the various load characteristics used in the body electronics. For example, LEDs are rapidly replacing incandescent lamps because of their low power consumption, excellent robustness and reliability. Electronic motors are also used to implement mechanical functions such as raising and lowering windows, changing seat positions, and adjusting mirrors. Resistive elements are used in seat heating and rear window defrosting applications.

Integrating control and power circuits into one module requires some challenges to be solved. When BCM designers start a new design, they must consider all possible device options for the control and power supply parts, and then, after considering all design factors, decide how to combine the two to best meet the needs. When a designer chooses a suitable device combination, the main design factors that must be considered are: power budget, heat dissipation, robustness, and cost. For example, the power supply part traditionally only uses power relays, but recent designs have shown signs of transition to solid-state solutions. Solid-state electronics can provide a more robust solution to reduce overall costs. In addition, by combining these solid-state devices with intelligent digital controllers, designers can achieve diagnostic and fault prevention protection functions that were impossible before. Ultimately, the designer’s goal is to produce a cost-effective BCM that can fully meet application needs and has high reliability to meet stringent automotive standards.

Figure 1 is a BCM principle block diagram based on NEC Electronics’ 32-bit MCU V850ES/Fx3, which shows the connection between the module and the sensor’s output and power supply. The advantage of using MCU is that the control problem can be divided into hardware peripherals and software algorithms to solve. Compared with the method of realizing control by hardware, this modular design method has more flexibility. In addition, the use of MCU can also perform diagnosis (even self-diagnosis) in the system, thereby making the system more robust.

  Design of Control Power Supply for NEC Electronic Body Electronic System

Figure 1: The block diagram of the body control module based on the 32-bit MCU V850ES/Fx3.

When implementing the control part of the body module, the most critical decision is to select an MCU with appropriate peripherals that can meet the application’s performance and cost budget requirements, such as NEC Electronics’ V850ES/Fx3 MCU. V850ES/Fx3 is based on the V850 32-bit CPU core and is optimized for automotive body applications. The V850 core is designed for embedded systems. It has real-time performance such as high-performance processing capabilities, fast interrupt response speed, and efficient data transmission capabilities. The core also includes a dedicated interrupt controller equipped with an independent vector for each interrupt source, which can quickly respond to various requests. The on-chip direct memory access (DMA) unit can access the memory and the system bus, and can transfer data without CPU intervention.

In particular, the V850ES/Fx3 MCU integrates a variety of advanced peripherals that are particularly required by body modules. For example, the timer is very important for car body applications. It is used to schedule tasks, capture external signals such as RF pulses, and more importantly, it can generate pulse width modulation (PWM) signals required to control LEDs in the car. The V850ES/Fx3 MCU can provide multiple programmable timer macros that can run in multiple modes. It can also synchronize each timer to increase the PWM capability. In order to meet the increasing needs of OEMs for the network, the MCU series integrates 5 controller area network (CAN) channels, each channel has an independent information buffer and a mask register that can filter information without CPU intervention. For low-speed local interconnect network (LIN) applications, the V850ES/Fx3 MCU supports 8 LIN channels and has a multi-LIN master (MLM) unit that uses hardware to process the LIN protocol, thereby saving CPU resources. The MCU has up to 40 analog-to-digital conversion channels to process analog signals. These channels have pin diagnostics, automatic discharge and flexible trigger resources.

  Design of Control Power Supply for NEC Electronic Body Electronic System

In addition to the demand for smart on-chip peripherals, an overwhelming trend in embedded automotive electronics is the use of flash memory. For example, the code flash space of V850ES/Fx3 MCU is from 6? kB to 1MB, it also has other on-chip memory that can be used as data memory to store high-endurance data.

One of the most demanding requirements for the MCU in body electronics applications is that the MCU must keep working when the car is not running. In this case, the MCU must support a standby mode to provide the necessary functions at an acceptable power consumption level. V850ES/Fx3 MCU has NEC Electronics’ MF2 embedded flash memory technology for low power consumption mode, which enables the MCU to run only necessary peripherals such as internal clock and periodic timers required by the system, which consumes power at this time Only 10 to 15uA, which can meet the most demanding power consumption requirements. Combining the beauty of high-density flash memory and low-leakage current logic, it can reduce power consumption while enabling the entire MCU to have an outstanding cost performance.

power control

The second challenge in designing the BCM module is to generate the power supply part. This part of the design is closely related to the type of load that the module must drive. Simple LED lights are a common load. The most direct way to control the LED is to use the MCU output pin to control the on and off of the LED operating current. Using the PWM signal to light up the LED can bring a more pleasant visual impression. The use of the PWM signal allows the LED to be switched on and off at such a frequency that the LED seems to be on all the time to the human eye. By increasing/decreasing the duty cycle, the designer can increase or decrease the average current flowing through the LED to effectively adjust the brightness of the LED, which is similar to the lighting control of a theater. Using red, green and blue LEDs, each color is PWM controlled, and designers can generate composite light of any color. This function further increases the demand for PWM channels in the MCU.

The second type of load for BCM modules is motors, such as fan motors used in thermal ventilation and air conditioning systems. The motor is also used to adjust the seat position and drive the wiper system. Similar to controlling LEDs, with PWM, designers can effectively control and adjust the speed of standard DC motors. In addition, sampling the PWM signal with an analog-to-digital converter allows designers to detect possible failures. In body electronics applications, various motors are used. They include brushed DC, brushless DC and even three-phase motors. Each motor requires unique control characteristics, and this requirement must be taken into consideration when designing the power supply section.

The third type of load in body electronics is heating elements, for example, heating elements used to heat the seat to generate heat. For effective heating, these high-power resistors require the body module to provide sufficient current. Traditionally, simple 12V relays are used to provide the required current for high-power applications. Relays are large and heavy electromechanical devices, and they are not as reliable as full electronic solutions. This is a fatal shortcoming for automotive devices. In view of these shortcomings, some traditional relay applications have been replaced by power MOSFETs. MOSFETs are designed to deliver large currents and are a complete solid-state solution. MOSFET solves the problems of volume, weight and reliability of relays. Adding intelligence to the solid-state switch will further strengthen its function. At this time, it is also called an intelligent power device or IPD. A typical IPD integrates both power MOSFET and control circuit in a single package. Like MOSFETs, IPDs are smaller, lighter, and lower power devices that replace typical relays. IPD combines the high current and high reliability of MOSFET with the characteristics of thermal runaway, short-circuit protection and diagnosis. It is a better product than MOSFET.

Figure 3 shows a high-end IPD with built-in short-circuit and overheat protection and load current sensing. In addition, in order to reduce the EMI in the module, the IPD has a switch control function that limits the rapid fluctuation of the output current.

This type of IPD is often used to replace relays in body applications such as interior and exterior lighting and heating (Figure 4). Based on the small size of the IPD die, a four-way IPD module can replace 4 standard relays. In this case, the 4 relays that drive the brake and turn signal lights can be replaced by an IPD module. In addition, because the IPD is smaller than the relay in all dimensions, the ECU engineer can reduce the size of the PCB and the entire module. The reduced module size and the number of components combined with the increased reliability brought about by the use of IPD can produce higher quality and more cost-effective products.

Because IPD is a relatively new product for many designers, it is important to understand its main characteristics when deciding which product to use. The typical situation is to determine how much current the IPD can provide under what voltage. Many suppliers will first arrange their devices according to these parameters. Once this decision is made, there are several other factors to consider when choosing a specific IPD. As mentioned before, IPD can provide diagnostic data for the control unit. Diagnosis data transmission can be realized through network protocols such as Serial Peripheral Interface (SPI) or independent port communication. For systems with SPI bus, SPI connection is very convenient. However, for systems that need to receive IPD feedback signals faster than SPI can provide, standard port signals are a good choice. There are IPDs that support these two methods. Therefore, the module designer must consider the overall system requirements to select the most suitable communication method.

  Design of Control Power Supply for NEC Electronic Body Electronic System

On-resistance, sometimes written as R (ON), is the equivalent resistance at both ends of the device when it is working. Large on-resistance will bring many problems, it will cause a significant voltage drop across the device, leading to greater power consumption, and therefore increase the device heat. To solve this problem, the R(ON) value of the devices currently produced can be as low as 8mΩ. When choosing IPD, the designer will, as always, choose the device with the lowest R(ON) that can meet the system requirements. Another important factor that should be considered is the connection between the control circuit and the analog power supply section. There are two commonly used IPDs: single-base and multi-base forms. In a single-base IPD, its control and power supply parts are made on the same silicon base. In a multi-substrate IPD, the control and power supply are separated on different silicon substrates. The reason for these two methods lies in the underlying technology required by each. The process technology required for high-density logic cannot provide high current, so multi-substrate technology must be used to realize high-current devices. When the current requirement is not very high, the same technology can be used to design the power supply and logic, and the designer can avoid the complexity and cost brought by two different substrates and the subsequent bonding and packaging problems. Although the choice of single-base and multi-base solutions is usually determined by the IPD supplier, the designer should always be aware of the specific process technology used to ensure that the device meets the demand.

  

Finally, packaging is also very important. Currently, IPDs are manufactured with more and more refined processes, allowing smaller packages and supporting multi-channel packages. Designers are almost always looking for the smallest package, and do not miss any opportunity to replace multiple IPDs with multi-channel packages.

In short, in order to design a reliable, cost-effective system, you need to grasp the two main parts of the design-control and power. In order for these two parts to work together best in the entire system, they must deal with their own challenges when selecting devices for them.

Author: Adam Prengler

Automotive Electronics Platform Solution Engineer

NEC Electronics

The Links:   PM100RSE120 G057QN01-V1

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