Soft starting circuit for voltage regulator

Abstract

The invention discloses a soft starting circuit for a voltage regulator, and the soft starting circuit comprises a first bias current source, a first capacitance, a switch device, a second bias current source, a first resistance and a first operational amplifier, wherein the second bias current source is arranged between an external power supply and a first terminator of the first resistance, the first terminator of the first resistance is used as an output end of the soft starting circuit, and a second terminator of the first resistance is respectively connected with a negative input end of the first operational amplifier and the output end of the first operational amplifier. The soft starting circuit not only can prevent inductance current surge and overshoot pulse of the output voltage in the starting process, but also can reduce the variation range of the system on-off frequency in the soft starting process and reduce the processing difficulty of the system electromagnetic interference, so that the output voltage is smoothly increased to a stable working value, and the stability problem in the starting process can be avoided.

Description

technical field [0001] The invention belongs to the technical field of power supplies, and in particular relates to the design of a soft start circuit used in a voltage regulator. Background technique [0002] A voltage regulator is a system that completes the conversion of a power supply from one DC form to another, and realizes functions such as output voltage amplitude being greater than or less than input voltage amplitude. There are many control modes for voltage regulators, including voltage mode control, current mode control, constant on-time control (COT (Constant-on-time) control) and so on. The COT control mode is widely used because of its simple control loop structure and fast system response. [0003] In order to prevent the inductor current surge and output voltage overshoot during the power-on process of the chip, a soft-start module is designed when designing the chip, so that the chip transitions smoothly from the startup phase to the stable working state. ...

AI Technical Summary

Problems solved by technology

Traditional soft-start circuits in COT control mode such as figure 2 , only control the loop comparator in the start-up phase, so that the reference level of the loop comparator gradually rises with time to prevent excessive inrush current and output voltage overshoot in the inductor current, but due to the On_Timer timer timing T on Therefore, when the chip starts to start, the inductor current will surge, resulting in a step in the output voltage Vo, and the operating frequency of the system changes greatly during the start-up period, such as image 3 As shown, this will lead to unnecessary power loss, reduce the conversion efficiency of the chip, and increase the difficulty of EMI (Electro Magnetic Interference) processing

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