Soft start control circuit for switching power supply, and switching power supply

Abstract

The invention provides a soft start control circuit for a switching power supply, comprising: a clock frequency generator for generating a frequency signal with a small duty cycle; an output end of the clock frequency generator is connected with a control end of a first switch module; an input end of the first switch module is connected to a power end, and an output end of the first switch moduleis connected to the end having a high capacitance potential of the soft start control circuit; and the common end of the first switch module and a capacitor is further connected with a non-inverting input end of a first comparator of the soft start control circuit. The invention also provides a switching power supply comprising the soft start control circuit, an error amplifier, a pulse width modulation comparator, a switch tube drive unit and other main components. The invention uses the uA-level current to charge a delay capacitor with a certain duty ratio, thereby solving the problem that the soft start of the switching power supply is abnormal. At the same time, the capacitance value of the delay capacitor is reduced, the space inside the chip is saved, and the cost of the chip is reduced.

Description

Technical field [0001] The present invention relates to the technical field of switching power supplies, in particular to a soft start control circuit of a switching power supply and a switching power supply. Background technique [0002] Due to the advantages of high efficiency and high energy density, switching power supplies are used in more and more fields, especially DC-DC BOOST switching power supplies have been widely used in mobile power supplies and portable electronic devices. [0003] Although the DC-DC BOOST switching power supply can convert the low voltage of a single ordinary battery to a higher voltage to meet the use of equipment, the BOOST switching power supply will generate surge current and overshoot voltage when starting, which may damage the switching tube Other devices and the risk of burning the lithium battery that provides power to the chip. Therefore, we need to add a soft-start control circuit to the BOOST switching power supply, which can control the ...

AI Technical Summary

Problems solved by technology

[0005] In view of this, an embodiment of the present invention provides a soft-start control circuit for a switching power supply and a switching power supply to solve the problem that the nA-level current is affected by the process and cause the abnormal start-up of the soft-start control circuit for the switching power supply, and at the same time, reduce the use of The capacitance value of the capacitor that generates the start-up delay

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