Line voltage detection circuit for switching power supply

Abstract

A line voltage detection circuit for a switching power supply comprises a line voltage input end used for inputting a line voltage, an input resistor, a voltage regulator module and a current sampling module, wherein the input resistor, the voltage regulator module and the current sampling module are connected in sequence; one end of the input resistor is connected with the line voltage input end, and the other end of the input resistor is connected with the voltage regulator module; the voltage regulator module comprises a first output end used for outputting a regulating voltage, a second output end used for outputting a regulating current, and an input end used for outputting a reference voltage, and the voltage regulator module controls the regulating voltage and outputs the regulating current to the current sampling module; an input end of the current sampling module is connected with the second output end of the voltage regulator module and used for receiving the regulating voltage, and an output end of the voltage regulator module is used for outputting a detection current proportional to the regulating current. By means of the line voltage detection circuit for the switching power supply, the ratio of a detection output value and a line voltage input value can be set according to a resistance value inputted to the resistor.

Description

technical field [0001] The invention relates to a line voltage detection circuit of a switching power supply. Background technique [0002] The line voltage of the switching power supply, that is, the input voltage of the switching power supply circuit. When the switching power supply circuit works in the constant current output mode, due to the inherent defect of the closed-loop constant current control method, the output current amplitude is affected by the input voltage, that is, the line voltage amplitude, and the degree of this influence is also related to the system circuit board parameters. Internally, through an additional compensation circuit, the amplitude of the output current will be compensated according to the amplitude of the detected line voltage, so as to achieve the purpose of constant current output. Therefore, a line voltage detection circuit of a switching power supply is needed, which is used to output a detection current related to the line voltage an...

AI Technical Summary

Problems solved by technology

[0003] However, in the current line voltage detection circuit of the existing switching power supply, the ratio of the detected output current value to the line voltage input is set as a fixed value inside the control chip, and the fixed value cannot adapt to the parameter change of the system circuit board, so that the compensation The compensation effect of the circuit deviates from the design value. In addition, the fixed value set inside the chip is affected by the production process and has a large degree of dispersion, thereby reducing the batch consistency of the constant current output.

Therefore, the existing switching power supply line voltage detection circuit has been increasingly unable to meet the needs of users

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