Soft start circuit and power system

Abstract

The embodiment of the invention provides a soft start circuit and a power supply system. The soft start circuit is connected with a power supply circuit comprising an error amplifier, the soft start circuit comprises a comparator and a discharge module connected with the comparator, a first input end of the comparator is connected with an output end of the error amplifier, a second input end of the compactor is connected with first reference voltage, the compactor is used for outputting a discharge signal to the discharge module according to the output voltage of the error amplifier and the comparison result of the first reference voltage, and the discharge module is used for controlling the error amplifier to discharge according to the discharge signal; a voltage value of the first reference voltage is increased step by step from small to large along with increase of time, the peak value of the output voltage of the error amplifier is increased step by step from small to large along with increase of time, and then the peak value of a current value or a voltage value of the power circuit output can be increased step by step from small to large along with increase of time.

Description

technical field [0001] The invention relates to the technical field of power supplies, in particular to a soft start circuit and a power supply system. Background technique [0002] Along with the wide application of portable devices, switching power supplies are widely used due to their small size, light weight and high efficiency. [0003] A switching power supply, such as a Boost power supply circuit, generally includes a boost circuit and a feedback loop. [0004] The boost circuit includes an input terminal, a power tube, an inductor, a capacitor, a voltage regulator tube, a PWM controller, etc. The input terminal is connected to an inductor, the inductor and capacitor are connected in series, and the inductor and capacitor are grounded through the power tube. The on and off of the power tube is controlled by the PWM signal. When the power tube is turned on, the inductor is grounded through the power tube, and the input terminal is charged for the inductor; when the po...

AI Technical Summary

Problems solved by technology

[0007] Although the inductor current or output voltage overshoot can be prevented by the soft-start circuit, but in the start-up phase of the switching power supply, for example: when the start-up is first started, the voltage at the output terminal is too small, which makes the duty ratio of the PWM signal large, resulting in the current of the power tube The peak value is large, which further causes the inductor to charge more energy for the capacitor, which in turn leads to a sudden increase in output current or output voltage, which will damage transistors and other devices

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