Soft start circuit with quick response characteristic

Abstract

The invention belongs to the technical field of electronic circuits, and specifically relates to a soft start circuit with quick response characteristic. The circuit charges an RC (Resistor-Capacitor) parallel structure by adopting step current; the charging circuit comprises a current source I1, a current source I2, an off-chip capacitor C, a resistor R1, a resistor R2, a comparator and a switching tube MN; the voltage drop generated on the resistor R1 by the current source I1 is input to the negative input end of the comparator, the voltage drop generated on the resistor R2 by the current source I2 is input to the negative input end of the comparator, and the resistor R2 is connected in parallel with the off-chip soft start capacitor and connected with the drain of the MN1; the voltage drop V1 generated on the resistor R1 by the current source I1 is input to the positive input end of the comparator as a voltage reference point of the soft start circuit; the current source I2 charges the off-chip capacitor C, and the voltage V2 on the capacitor is input to the negative input end of the comparator; and the soft start process ends when the comparator outputs a high soft start identification signal, and a chip enters a normal working state.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits, and in particular relates to a soft start circuit with fast response characteristics. Background technique [0002] In the field of switching power supply technology, the soft-start circuit is a very important module, which can be applied in the DC-DCBUCK converter. Its function is to provide a slow power-on process for the system and prevent the system from inrush current when the system is powered on. [0003] The common structure of the traditional soft start circuit is as follows: figure 1 As shown, including comparator SS_COMP1, off-chip capacitor C, and mirror current source I1. [0004] Assuming that the capacitor is charged from the initial state of zero point pressure, the voltage on the capacitor at time t is determined by the following formula: [0005] V ss_in C ss =t×I ss [0006] I ss Output current for current source I1; [0007] When the charging voltage on the...

AI Technical Summary

Problems solved by technology

That is to say, the voltage on the soft-start capacitor is required to discharge from 5V to 0.8V before the soft-start flag signal changes, so there is a long system shutdown response time, which brings potential safety problems in the event of a fault

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