Soft start circuit used in monolithic integration switching-type regulator

Abstract

The invention provides a soft start circuit used in a monolithic integration switching-type regulator, which comprises a charging current generative circuit which is internally provided with a bias current generator, a soft start capacitor and a group of current mirrors, and is used for generating a first current IREF in the bias current generator, and then the IREF generates charging current ICSSby a group of current mirrors, the ICSS charges the soft start capacitor and generates capacitance voltage on the soft start capacitor; a soft start voltage generative circuit obtains the capacitancevoltage which is taken as the soft start voltage SS to be output; a soft start control signal generative circuit is internally provided with the input end of a comparator which respectively inputs the SS and a first voltage reference VREF, and is used for selecting one of a second reference voltage and the SS as the output voltage according to a high-low output soft start signal control signal SS-signal between the SS and VREF. The technology provided by the embodiment is applied to ensure that the output of the switching-type regulator realizes the smooth transition from the soft start to normal operating conditions, and no external high-capacity soft start capacitor is need, thus reducing chip pins and cost.

Description

technical field [0001] The invention relates to electronic circuit technology, in particular to a soft start circuit for a monolithic integrated switching regulator. Background technique [0002] Traditional switching regulators such as figure 1 In the typical boost converter shown, during start-up, since the output voltage is relatively small, the voltage at the feedback terminal FB is relatively low, and the reference voltage is already a normal value, the output of the error amplifier quickly charges the compensation capacitor C103, which may can cause surges that overload the input, or excessive voltage at the output. [0003] This surge can be avoided by using a soft-start controller to slowly ramp up the voltage on capacitor C and limit the energy delivered to the output capacitor C. figure 2 A soft-start device is described. During the power-on stage, due to the relatively large capacitance of the external soft-start capacitor C104, the voltage at the SS terminal r...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the embodiment of the present invention is to provide a soft-start circuit for a monolithic integrated switching regulator, which is used to solve the problem in the prior art that the soft-start circuit requires additional capacitors and additional pins, and the number of leads is limited. Defects that are impractical in circumstances and cannot be packaged in a monolithic integrated circuit due to capacitors that are too large

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