This paper presents a Pulse Width Modulation (PWM)-based Maximum Power Point Tracking (MPPT) approach suitable for low-power DC energy harvesting systems. A wide-range, low-power PWM scheme is achieved by incorporating one half-circuit of a single thyristor delay element. The proposed Thyristor-based PWM circuit achieves a wide duty cycle range of 2% to 60% while consuming 23n to 80n , making it an energy-efficient solution for various applications. The energy harvester attains a peak tracking efficiency of 99.9 % and above 99% for a wide input power range. An integrated Power Change Detector (PCD) is proposed, which saves power by activating the MPPT circuit only when needed, reducing power consumption to 125nW. The performance is verified through simulation using 65nm CMOS technology.