## 2 SJB Implementation  
### Design of the SJB PCB Module  
A schematic of the implemented SJB is shown in Figure 3. In this design, the PCB module consists of a dual PCB-type arrangement in which the power and control circuits are separate. The components in the system include a 16-bit MCU, a controller area network (CAN) communications controller, a multiple switch detection interface (MSDI) chip, a 9-channel IPS, a low-side driver (LSD) chip for relay control, and a power supply. The IPS was initially configured to supply and control six headlights that consume a large amount of current, although other loads, such as that of wipers, can also be added. The initial six control loads were defined as: Headlight Low (left hand (LH) and right hand (RH)), Headlight High (LH and RH), and Fog (LH and RH). The CAN module provides both low- and high-speed communications buses. The low-speed CAN bus is used for load control communications with the vehicle body control module (BCM) while the high-speed bus is used for communications with other modules, such as an electronic control unit (ECU), in support of load control and diagnostic functions. The purpose of the watchdog circuit is to monitor and reset the MCU when any of the components malfunction and to directly drive the Headlight Low Beams in such instances. The SJB control board receives power from the power board and is configured to control the on/off state of the load through the IPS. This board includes the following:  
Main power supply circuit: converts the 13.5 V (input) to 5 V (output), as required by the MCU, Control MCU: the MCU and its associated peripheral circuits, IPS: the IPS and the peripheral circuits required for each load capacity, CAN: includes one high speed and one low speed 1-channel CAN bus,  
Figure 3: Schematic of the implemented SJB. Watchdog: circuit designed to detect abnormalities in the operation of the MCU, and Interface and I/O: Interface circuitry for processing external input signals and input/output circuitry to and from the other circuits in the SJB. A detailed schematic of the main power supply is shown in Figure 4. To stabilize the power, B + 2, B + 3, and ACC power are supplied in parallel from the relay box at the rear of the battery. All three of these types of power pass through reverse voltage diodes that smooth the power before it is received at the SJB control board. The voltage regulator in this supply is a TLE4263 (Infineon) with an output voltage of 5 V and a maximum output current of 200 mA. An inhibit port is provided as a way to implement a sleep function, which limits the dark current, and the watchdog port is connected to allow the watchdog function to exert control in the MCU. The SJB power board is composed of a multi-function switch input circuit to supply power to the load through the connection with the SJB control board and to the other modules through a fuse connection. This board includes the following:  
A terminal block for connection purposes,  
A fuse for power distribution,  
Relay and driver circuits, and  
I/O expansion circuits that support connection to external input signal processors. A schematic of the SJB power board circuitry is shown in Figure 5.  
Figure 4: Schematic of the main power supply. Figure 5: Schematic of the circuitry on the SJB power board. The specifications of the primary power, control, and communications components in the designed SJB are listed in Table 1.  
The specifications of the output in terms of the loads, current consumed, and IPS are provided in Table 2.  
The proposed SJB includes a PCB structure consisting of power, control, and communication portions. The power and control units were placed in separate regions on the same PCB to simplify placement of the connector and fuse and to reduce the amount of noise generated by the strong current. This arrangement also reduces the potential for temperature-related problems because it allows the IPS to be placed in the upper section of the PCB.