Abstract: A comparator is designed to control the current flowing through a synchronous rectifier. This comparator adjusts its threshold voltage based on the output voltage to address the issue of a small amount of reverse current required by a DC/DC switching power supply management chip operating in PWM mode under light load. Keywords: comparator; variable threshold; synchronous rectifier; output reverse current [b][align=center]Design of a Comparator Applied in Current Detect of Synchronous Reifications SUN Mao-mao, FENG Quan-yuan[/align][/b ] It adjusts the threshold voltage according to the output feedback voltage to permit small amounts of reverse current to flow from the output during light loads in PWM mode. Key words: comparators; adjustable threshold voltage; synchronous rectification; reverse currents. Introduction In recent years, with the increasingly widespread application of low-voltage, high-current, and high-efficiency switching power supplies, replacing traditional rectifier diodes with low-power synchronous rectifiers has become a major technology for improving efficiency. In Buck-type DC/DC switching power supplies, the synchronous rectifier provides a path to ground for the inductor when the switch is off. Under normal load conditions, when the inductor current drops to 0, the synchronous rectifier needs to be turned off to prevent inductor backflow and reduced efficiency. Since the output voltage increases under light load in PWM mode, a small amount of reverse current is required to release the charge on the output capacitor. Therefore, designing a comparator to control the current flowing through the synchronous rectifier is crucial. In PWM mode, the comparator raises the threshold voltage under light load, allowing the synchronous rectifier to permit a small amount of reverse current, thereby eliminating the limitation of the switching power supply on minimum load. This switching power supply chip is manufactured using a 0.6µm BICMOS process, achieving an efficiency of over 95%. It is primarily used in mobile phones, PDAs, and portable devices. For more details, please click: Research and Design of Synchronous Rectifier Current Control Comparator.