## 1 Introduction
This problem has been solved by including a microcontroller unit (MCU) in the JB in which the software supports real-time failure diagnosis by storing and monitoring sensor and communications information. Advances in the electronic systems of vehicles have led to the development of intelligent power switches (IPSs), which are semiconductor devices designed to drive a variety of loads, such as lamps, motors, and valves. In addition to basic load switching functions, IPSs also provide overload and short-circuit protection, diagnostics, and improved electromagnetic compatibility, and are available as solderable surface-mount devices, which reduce manufacturing costs. However, as most lamps and motors in a vehicle are controlled via pulse-width modulation (PWM) signaling and receive their operating current from the IPS, the IPS needs to support both PWM signaling and monitoring via an MCU for diagnostic purposes [19; 20]. These recent requirements and existing problems in JBs have led to the development of smart JBs (SJBs) that incorporate IPSs controlled via PWM to replace fuses and mechanical relays. SJBs also incorporate electronics to improve the stability of the electrical system, provide efficient power management, and enable efficient data exchange. Recent SJBs also incorporate an MCU for monitoring and control purposes. These advantages have enabled in-vehicle power distribution systems in internal combustion engine vehicles and electric vehicles (xEVs) to evolve from fuse/relay-based JBs to IPS-based SJBs. A timeline of the evolution of JBs to smart JBs (SJBs) is shown in Figure 1, and schematics illustrating the differences between JBs and SJBs are shown in Figure 2.  
The growing adoption of xEVs has triggered a need for SJBs that can be mounted on xEVs to serve as a stable source of power [21]. However, previous studies have analyzed the results of simulations. In addition, there has been no recent research experimentally verifying the characteristics that can be seen through the manufacture of prototypes. [22; 23]. In this study, we implemented a PCB-type SJB that was designed to provide stable power for the low-voltage headlights used in xEVs. A key requirement of automotive electronic systems is reliable power supply to the headlights, which is used for illumination while driving. However, this is not straightforward as the headlights are located in different places in the wiring harness, which changes the respective wiring lengths and resistances the power must traverse. If the SJB did not take this into account, the brightness of the headlights on the left and the right would not be uniform, which would compromise driver safety and may decrease the service life of the bulbs. The PCB-type SJB in this study included a power supply and control unit that were designed to stabilize the current supplied to the headlights by controlling the duty cycle of the voltage based on the PWM signal from the SJB. The power and control units were positioned in separate locations in  
Figure 1: Timeline showing the evolution of JBs to SJBs. Figure 2: Schematics illustrating the differences between JBs and SJBs: (**a**) JBs and (**b**) SJBs. the SJB design to minimize any temperature-related effects. An MCU and associated software were implemented to improve driving stability by monitoring the headlights to identify any abnormal states when driving. The detection of any abnormal condition, such as open circuits, short circuits, and overvoltage, during operation, disables and resets the control system to check the load. When the input voltage is below 13.5 V, a 100% duty cycle PWM voltage is supplied to the headlights. On the other hand, when the input voltage exceeds 13.5 V, the PWM duty cycle is less than 100% to minimize the effects of the overvoltage on the headlights. The performance of the design was validated by conducting a thermal analysis by simulating the PCB module to confirm the temperature distribution of the SJB when the headlights were driven by the IPS.