Control system and control method for stepless current limiting of switch power supply

Abstract

The invention discloses a control system for the stepless current limiting of a switch power supply. The system comprises a current limiting voltage control unit, a voltage loop controller, a current limiting current control unit, a current loop controller and a pulse width modulation unit; the output end of the pulse width modulation unit is connected with a DC (direct current) / DC main circuit of the switch power supply. The system also comprises a voltage sampling unit, a first filter, a current sampling circuit and a second filter. The control method for the stepless current limiting of the switch power supply is used for performing dual-closed loop control, namely voltage loop control on the outer loop and current loop control on the inner loop, on the DC-DC main circuit of the switch power supply, so the current limiting function of software is realized. Driving oscillation of a power switch caused by the current limiting is avoided, and the system has the characteristics of precise current limiting, capability of setting a current limiting point, reduction of output ripple wave voltage (peak-peak value noise voltage) under the current limiting condition, small system noise, high reliability and the like.

Description

technical field [0001] The invention relates to a current limiting control system, in particular to a stepless current limiting control system applied to a switching power supply and a control method thereof. Background technique [0002] At present, the current limiting method of switching power supply with voltage loop and current loop control is as follows: [0003] (1) Hardware current limiting method (or hardware peak current limiting method): [0004] When the output current Ioi exceeds the output current limiting point ILmt, the hardware circuit turns off the driving PWM signal to achieve the purpose of output current limiting, but at this time the voltage loop and the current loop are equivalent to open loops. When the detected output current is less than Ilmt , due to the open-loop saturation of the voltage loop and the current loop during current limiting, the maximum duty ratio of the drive output power tube switch stress is large, which reduces the reliability o...

AI Technical Summary

Problems solved by technology

[0006] When the output current Ioi exceeds the output current limit point ILmt, the software directly turns off the drive PWM signal to achieve the purpose of output current limit, but at this time the voltage loop is equivalent to an open loop, when the detected output current is less than the output current limit point When ILmt is reached, due to the open-loop saturation of the voltage loop and the current loop, the maximum duty cycle of the drive output, the stress of the power tube switch is large, and the reliability of the system is reduced. In addition, the existing software current limiting method is easy to cause the problem of power tube drive oscillation, which also exists Large system noise, large output voltage ripple, etc.

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