An Auxiliary Sampling Circuit of Primary Inductance Peak Current of Switching Power Supply

Abstract

Disclosed in the invention is an auxiliary sampling circuit of a primary inductance peak current of a switching power supply. The auxiliary sampling circuit is composed of a PWM inverting circuit, a first sampling circuit, a fine tuning circuit, a delay circuit and a second sampling circuit. The fine tuning circuit carries out fine tuning on a first sampling voltage obtained by the first sampling circuit and compensating for an error caused by delayed internal transmission of a power controller chip. The delay circuit enables the internal transmission delay of the power controller chip to be completed when the second sampling circuit starts to carry out sampling and guarantees that a final sampling voltage of the second sampling circuit is a switching power supply primary peak voltage reaching a peak value, thereby realizing sampling of the actual primary peak voltage of the switching power supply. For the primary peak voltage, the precise switching power supply primary inductance peak current can be obtained by a sampling resistor, thereby avoiding inaccuracy of primary inductance peak current sampling of the switching power supply due to factors like transmission delay and the like. The sampling precision is guaranteed; and stability and consistency of the switching power supply controller chip are improved.

Description

technical field [0001] The invention relates to the technical field of electronic circuits, in particular to an auxiliary sampling circuit for the peak current of the primary inductance of a switching power supply. Background technique [0002] With the rapid development of integrated circuits, switching power supplies are being used more and more as an indispensable part of the integrated circuit field. As an important technical parameter of switching power supply, the peak current of the primary inductor of switching power supply will greatly affect its sampling accuracy. The overall performance of the switching power supply controller chip. The traditional sampling circuit samples the peak current of the primary inductor of the switching power supply when the PWM signal is turned off. However, due to unpredictable factors such as transmission delay inside the switching power supply controller chip, there is a time delay between the PWM signal being turned off and the BD ...

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Problems solved by technology

However, due to unpredictable factors such as transmission delay inside the switching power supply controller chip, there is a time delay between the PWM signal being turned off and the BD port of the switching power supply controller chip being actually turned off. During the actual shutdown process of the BD port, the primary peak voltage of the switching power supply continues to rise, resulting in a deviation between the sampled primary peak voltage of the switching power supply and the real peak voltage of the switching power supply, which in turn causes the sampled value of the peak current of the primary inductor of the switching power supply to be different from the real value. There is a deviation between them, so that there is an error in the internal operation, which will lead to a decrease in the overall performance of the controller chip

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