## 3 Experimental Verification of the SJB
### Assessing the Uniformity of the Supplied Power in the Presence of Supply Voltage Fluctuations  
As explained in the previous section, when the headlights are turned on, a non-uniform drop in voltage occurs from the SJB to each headlight due to the different lengths of the connecting wire. Therefore, the power supplied by the SJB needs to be stable despite variations in the length of the wire. In addition, the capacity in the SJB needs to be sufficient to satisfy the demands of each headlight in terms of the inrush current. As this is a factor that may reduce the life of the headlight, there is also a need to tailor the driving method to prevent the headlight from experiencing premature burnout. In the proposed SJB, this was accomplished via PWM control. A schematic of the test setup used to evaluate the uniformity of the power delivered by the SJB is shown in Figure 15.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Lamp Load**} & **Output Power** & **Battery Voltage** & **Load Voltage** & **Inrush Current** & **Operating Current** \\  & **[W]** & **[V]** & **[V]** & **[A]** & **[A]** \\ \hline H/LP High LH & 55 & 12.7 & 10.1 & 26.6 & 4.7 \\ H/LP Low RH & 55 & 12.7 & 10.3 & 22.4 & 4.2 \\ H/LP Low LH & 55 & 12.7 & 10.6 & 23.2 & 4.2 \\ H/LP High RH & 55 & 12.7 & 10.1 & 22.6 & 4.5 \\ Fog LH & 35 & 12.7 & 10.8 & 21 & 2.8 \\ Fog RH & 35 & 12.7 & 10.6 & 18 & 2.8 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Measured characteristics of each load.  
Figure 14: Current characteristic measurement of the H/LP High LH output.  
Here, PWM control was used to vary the duty cycle of the voltage based on an input voltage of 13.5 V. The duty cycle was determined as follows:  
\[\text{Duty cycle (\%)}=(\text{V}_{\text{ref}}/\text{V}_{\text{out}})\times 100 \tag{1}\]  
where \(\text{V}_{\text{ref}}\) is the input voltage reference value of 13.5 V, and \(\text{V}_{\text{out}}\) is the output voltage provided by the IPS to the headlight load. To reduce the headlight loss when the output voltage is too high, the following procedure was applied. When the power supply voltage is 13.5 V or less, the PWM duty cycle is set to 100%. On the other hand, when the power supply voltage is higher than 13.5 V, the duty cycle of the PWM voltage is expressed by Equation (1).  
An experiment was performed to measure the output duty cycle of the PWM signal supplied by the SJB to the headlight load and the resulting waveforms are shown in Figure 16. In this test, \(\text{V}_{\text{ref}}\) was 13.5 V and the input voltage ranged from 13.5 to 16 V. The input duty of the IPS through the PWM are shown in Figure 16a-c, where it can be seen that, as the input voltage increased, the input duty cycle of the IPS decreased so as not to exceed the input voltage reference value of 13.5 V. As shown in Figure 16d-f, the output duty cycle of the IPS was the same as the voltage applied to the headlight load. The plot of the output duty cycle of the IPS shows that the PWM control output did not exceed 13.5 V, thereby preventing unnecessary energy loss in the headlight.  
Figure 15: Schematic of the setup used to test the uniformity of the headlight power supply.  
The input and output duty cycles of the IPS for various input voltages are shown in Figure 17. As shown in the figures, as the input voltage increased, the error between the target and measured duty cycles tended to increase. In particular, the input duty and output duty cycles of the IPS were 84% for an input voltage of 16 V. Although the error between the target and measured duty cycles was 2.5%, the rms value of the IPS output voltage was 13.44 V, which satisfies the desired target (13.5 V) and does not degrade the life of the headlight.  
Figure 16: Measured input voltage and IPS duty cycle (PWM waveform): (**a**) IPS input duty cycle at 13.5 V; (**b**) IPS input duty cycle at 15 V; (**c**) IPS input duty cycle at 16 V; (**d**) IPS output duty cycle at 13.5 V; (**e**) IPS output duty cycle at 15 V; and (**f**) IPS output duty cycle at 16 V.