Line loss compensation circuit for switch power supply

Abstract

The invention relates to a line loss compensation circuit for a switch power supply, which is divided into a current-type line loss compensation circuit and a voltage-type line loss compensation circuit, wherein the current-type circuit comprises a multi-stage RC low pass filter, a voltage / current switching circuit and a current mirroring circuit, and the voltage-type circuit comprises a multi-stage RC low pass filter, a subtractor and a compensating resistance. The invention can produce a compensating current of Icpr or a compensating voltage of Vcpr which is proportionable to an output current of Iout, and the compensating current or the compensating voltage is used for offsetting voltage drop of an output wire caused by change of Iout, thereby recovering voltage stabilizing control function of a control loop to secure constant output. The invention has the advantages of skilful design idea and simple circuit and is easy to realize. The improvement of the invention is that: the switch RC filter is adopted to greatly reduce volume of an electric capacity of the RC filter, thereby facilitating integration, further improving circuit performance and simplifying circuit structure, and strengthening operation reliability of the switch power supply.

Description

technical field [0001] The invention relates to a line loss compensation circuit of an AC-DC switching power supply. Background technique [0002] In the existing technology, AC-DC switching power supply generally adopts a flyback primary side control method, such as Figure 5 As shown, with this architecture, the system does not need to use the optocoupler to feedback sampling at the secondary output of the output transformer, but uses the sampling of the primary auxiliary terminal (Vaux) of the output transformer to perform loop control. Its working process is: the input AC alternating current is converted into a DC signal Vin after full-wave rectification by diodes D1~D4 and filtering by capacitor C1. On the one hand, the DC signal Vin charges the capacitor C2 through the starting resistor R1. When the capacitor C2 is on After the voltage reaches the start-up voltage Vp of the voltage regulator control chip X3, the chip X3 starts to work; on the other hand, the DC signal ...

AI Technical Summary

Problems solved by technology

[0003] The problem with the above-mentioned switching power supply system is that in general, the voltage regulation is adjusted for a variable of the load (Load).

[0015] From the above formulas (1'), (2'), and (3'), it can be seen that when the output wire is selected, its loss resistance Rcable is a certain value, but the output current Iout is a variable that changes with the load Load , therefore, there are two variables Vout and Iout in formulas (1'), (2'), and (3'), but the control loop only regulates the voltage of Vout, and does not regulate the voltage of Iout, so , the control loop loses constant control of the output

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