A constant current control system for output current of primary-side feedback flyback power converter

Abstract

The invention discloses a constant current control system for the output current of a primary side feedback flyback power converter, which adds Ts compensation, Tr compensation and primary side peak current compensation on the basis of the traditional constant current control strategy, and also combines Constant current processing of digital PI compensation, and two modes of PWM and PFM are used for control. When some compensation is not considered, in PWM mode, the conduction time decreases with the decrease of the load, so the output current decreases with the decrease of the load. The deviation from the rated current is getting bigger and bigger. In PFM mode, the on-time remains unchanged, and the output current deviation from the rated current remains unchanged. The present invention can finally obtain the effect that the precision of the constant current is ±2%, thereby improving the constant current characteristic of the flyback converter.

Description

technical field [0001] The invention relates to an isolated switching power converter, in particular to a constant current control system for the output current of a primary-side feedback flyback power converter. Background technique [0002] With the rapid development of household electronic equipment, the demand for high-efficiency power supplies is also increasing, which leads to the rapid development of AC-DC power converters. The development of electronic equipment has put forward new indicators for AC-DC power converters, and the energy consumption and control accuracy of equipment have become the focus of the current power supply industry. In the field of power supply design, the flyback topology is widely used in low-power converters due to its simple structure, low cost, and wide input range. Such as offline charger, LED driver, etc. With the development of miniaturization and low-cost requirements of products, the primary side feedback method is proposed. Howeve...

AI Technical Summary

Problems solved by technology

[0006] Aiming at the defect of poor constant current accuracy of the existing primary-side feedback flyback power supply, the present invention provides a constant-current control system for the output current of the primary-side feedback flyback power converter, by analyzing three factors that affect the current accuracy , and then get the impact of various factors on the current accuracy, and on this basis to compensate for each factor, through the final simulation and test, comparison found that the effect of the constant current accuracy of ± 2% can be obtained, thereby improving the flyback conversion The constant current characteristic of the device further expands the application of the primary side feedback flyback switching power supply in the field requiring accurate constant current

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