## 1 Introduction  
As semiconductor technology continues to develop and innovate, the uses of electronic devices and elements in the on-board parts of vehicles or electric cars are progressively increasing. Twin headlamps in the front end of vehicles, including the blink lights, low beam lights, and high beam lights, are applied to cope with different traffic circumstances. In vehicle headlamps, incandescent halogen lamps have been replaced with optoelectronic semiconductors (OPSs) in a new generation of cars, due to their benefits such as direct-current (DC) driving, high brightness, high efficiency of power conversion, and outstanding color rendering [1; 2; 3; 4; 5; 6]. In addition, when motor vehicles are driven in road tunnels or on roadways in the night, the headlamp irradiation ranges can be expanded using high beam lights, the brightness of which settles on metal halide high-intensity discharge (HID) lamps. However, several negative characteristics of HID lamps should be contemplated, including alternating-current (AC) power driving, AC high-voltage start-up, and negative resistance characteristic; thus, electronic ballasts can be used to stabilize the brightness and driving current of HID lamps [7; 8; 9]. The abbreviation, laser, is an acronym for light amplification by stimulated emission of radiation. According to laser oscillator configurations, laser devices can be classified based on the various materials used for construction, such as solid-state laser, gas laser, semiconductor laser, and fiber laser. Figure 1a is a simple model of the semiconductor laser, whose active layer is embedded in between the p-type and n-type materials. The p-type Gallium Nitride (p-GaN ) can be a positive electrode, and the n-type Gallium Nitride (n-GaN) contact can be a negative electrode. When the laser diode (LD) is excited, the active layer can emit laser beams, which can be amplified using the mirror surfaces to emit laser beams [10]. When voltage from a power source is applied to the positive-negative electrode and the laser diode operates in the forward bias, the electrons are injected into the active layer from the n-type semiconductor; the wide band gap of the heterojunction can limit the amount of electron combinations in the active layer, and, through this carrier confinement, the population inversion probabilities can be substantially increased to promote high-intensity light emission [11], as shown in Figure 1b. In addition, the semiconductor laser possesses several exceptional characteristics, including monochromaticity, high directionality, high coherence, and high energy density. Thus, motor vehicle manufacturers have started to develop the high beam light of high brightness based on the high-power laser diode (HPLD). In this study, the HPLD of InGaN-based blue beam was used as the illuminant sources for vehicle headlamps. Due to the optical output power (OOP) of HPLD being directly proportional to its forward operating current [12], the HPLDs must be driven by a constant-current (CC). Therefore, the design of high-power laser diode driving controller (HPLDDC) requires a current-loop controller (CLC) and a voltage-loop controller (VLC) to manipulate the HPLDDC, achieving the constant-current output mode (CCOM) and constant-voltage output mode (CVOM), and the CLC and VLC can apply the proportional-integral (PI) control to accomplish the low steady-state error and system stable requirement. The PI control has excellent behavior in the low steady-state error; however, the tardy response speed of PI control can result in the current spike problem and the long settling time during the HPLDDC start-up transient phase. Therefore, studies [13; 14; 15] have proposed the use of dual control loops, including the proportional (P) control and PI control, in which the P control can promote  
Figure 1: Laser diode configuration and heterojunction: (**a**) Semiconductor configuration; (**b**) recombination of electron–hole pair at the heterojunction.