A high-power laser diode driving controller (HPLDDC), which incorporates the power converter with the feedback controller, was developed and implemented in this paper. The synchronous buck–boost converter (SBBC) was the topology of the power converter; the SBBC could be operated in step-up or step-down mode in accordance with variable on-board battery voltage inputs into the HPLDDC. Moreover, the feedback controllers were equipped with a current-loop controller (CLC) and a voltage-loop controller (VLC); the VLC was employed to regulate the SBBC output voltage to drive and start-up the high-power laser diode (HPLD). The CLC was used to regulate the SBBC output current to supply a constant-current driving the HPLDs. During the start-up transient phase, when the SBBC output mode is changed from the constant-voltage to the constant-current, a start-up current spike occurs that can destroy the semiconductor material of the laser diode. However, few studies have discussed methods of coping with this problem. Therefore, this study proposed a proportional-integral associating proportional (PIAP) control technology, which can be applied to the CLC for the start-up current spike mitigation. Complete designs and analyses are presented in this paper. Simulations and experiments validate that the PIAP control method is effectual to solve the start-up current spike.

An enhancement-mode gallium-nitride high-electron-mobility transistor (E-mode GaN HEMT) operated at high frequency is highly prone to current spikes (di/dt) and voltage spikes (dv/dt) in the parasitic inductor of its circuit, resulting in damage to the power switch. To highlight the phenomena of di/dt and dv/dt, this study connected the drain, source, and gate terminals in series with inductors (L_D, L_S, and L_G, respectively). The objective was to explore the effects of di/dt and dv/dt phenomena and operating frequency (f_S) on drain-to-source voltage (V_ds), drain-to-source current (I_ds), and gate-to-source voltage (V_gs). The experimental method comprised two projects: (1) establishment of a measurement system to assess the change of electrical characteristics of the E-mode GaN HEMT and (2) change of the f_S and the inductances (i.e., L_D, L_S, and L_G) in the circuit to measure the changes in V_ds, I_ds, and V_gs, thus summarizing the experimental results. According to the experimental results on electrical characteristics, a gate driver circuit may be designed to drive and protect the E-mode GaN HEMT while being actually applied to a 120-W synchronous buck converter with an output voltage of 12 V and an output current of 10 A.