An Adaptive Soft-Start Circuit with Unsteady Current Limit

Abstract

An adaptive soft-start circuit with unsteady-state current limitation belongs to the technical field of electronic circuits. The present invention is applied to a switching converter, including an adaptive soft-start voltage generation circuit and a voltage selection circuit, the switching converter includes an error amplifier, and the voltage selection circuit compares the soft-start signal output by the adaptive soft-start voltage generation circuit with the second bias voltage , and the signal with a lower voltage value is input to the positive input terminal of the error amplifier; the error amplifier amplifies the error of its input signal and outputs it to the second input terminal of the adaptive soft-start voltage generation circuit, the adaptive soft-start The first input terminal of the voltage generating circuit is connected to the first bias voltage, and the charging current of the internal capacitor C is regulated according to the input signal thereof. The above circuit constitutes a negative feedback structure, so that the output signal of the error amplifier is clamped near the first bias voltage during the soft start, so that the inductor current can be kept at an appropriate value during the start.

Description

Technical field [0001] The invention belongs to the technical field of electronic circuits, and relates to an adaptive soft start circuit with a function of limiting unsteady current applied to a DC-DC switching converter. Background technique [0002] In many applications of DC-DC converters, a soft-start module is usually designed to prevent problems such as excessive current and logic errors during the hard power-up of the chip. The traditional method of the soft-start circuit is to charge the capacitor with a constant current. The capacitor voltage is used as the output voltage of the soft-start circuit. The output voltage is supplied to one of the inputs of the error amplifier, so that the output voltage of the converter follows the rise of the soft-start voltage. The speed increases to achieve the purpose of soft start. However, since the charging current of the traditional soft start is fixed, the rising slope of its output voltage is also fixed, and the DC-DC converter u...

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Problems solved by technology

The above situation will cause problems such as high duty cycle in some start-up situations

At the same time, because the capacitance and bias current are greatly affected by the process deviation, it is usually necessary to set a large margin to ensure the normal function of the soft start, which often makes the DC-DC converter have a relatively long start-up time

In addition, during soft start and other processes, the converter does not work in a steady state, especially in the current mode DC-DC converter, its unsteady current is not controlled during these processes, and even in extreme cases There is a situation where a large current burns the chip

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