Sample-and-Hold Peak Current Control in Switching Power Supplies

The sample and hold circuit captures and holds the peak current value at the moment it occurs, before the current begins to decrease. This preliminary action of storing the peak value allows for accurate comparison with the reference voltage without being affected by subsequent current changes or switching frequency variations, thereby resolving the contradiction between maintaining efficient peak current control and achieving accurate control.

The circuit employs a feedback mechanism where the held peak current value is compared with a reference voltage through an operational amplifier. The comparison result generates a control signal that adjusts the switching state of power switches. This feedback loop ensures accurate control by continuously monitoring and correcting the peak current based on the reference value, overcoming the inaccuracy caused by switching frequency and inductor influences.

The sample and hold circuit acts as an intermediary that decouples the peak current detection from the switching frequency variations. By capturing and holding the peak value in isolation, it provides a stable reference for comparison that is not directly influenced by switching frequency or inductor characteristics, thereby maintaining both switching control performance and measurement accuracy.

The circuit creates a copy of the peak current value by storing it in the sample and hold circuit. This copied and stored value can then be accurately compared with the reference voltage without being affected by the original current waveform changes or switching frequency variations, ensuring both effective switching control and accurate measurement.